Prof. Dr. Stephan Schulz

Inorganic Chemistry
University of Duisburg-Essen

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  • From π-Bonded Gallapnictenes to Nucleophilic, Redox-Active Metal-Coordinated Pnictanides
    Krüger, J. and Wölper, C. and Schulz, S.
    Angewandte Chemie - International Edition 60 (2021)
    A comprehensive reactivity study of gallapnictenes LGaEGa(Cl)L (E=As, Sb; L=HC[C(Me)N(Ar)]2, Ar=Dip=2,6-i-Pr2C6H3) proved the nucleophilic character of the pnictogen and the electrophilic nature of the Ga atom. Reactions of LGaEGa(Cl)L with imidazolium chloride [IPrH][Cl] yielded {[LGa(Cl)]2E−}{IPrH+} (E=As 1, Sb 2), and those with HCl and MeI gave pnictanes [LGa(Cl)]2EH (E=As 5, Sb 6) and L(I)GaE(Me)Ga(Cl)L (E=As 7, Sb 8). Pnictanides 1 and 2 also react with [H(OEt2)2][BArF4] (BArF4=B(C6F5)4) to 5 and 6, while reactions with MeI yielded [LGa(Cl)]2EMe (E=As 9, Sb 10). Single electron oxidation reactions of pnictanides 1 and 2 gave the corresponding radicals [LGa(Cl)]2E. (E=As, Sb). © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
    view abstract10.1002/anie.202013618
  • Influence of Nanoparticle Processing on the Thermoelectric Properties of (BixSb1−X)2Te3 Ternary Alloys
    Salloum, S. and Bendt, G. and Heidelmann, M. and Loza, K. and Bayesteh, S. and Sepideh Izadi, M. and Kawulok, P. and He, R. and Schlörb, H. and Perez, N. and Reith, H. and Nielsch, K. and Schierning, G. and Schulz, S.
    ChemistryOpen (2021)
    The synthesis of phase-pure ternary solutions of tetradymite-type materials (BixSb1−x)2Te3 (x=0.25; 0.50; 0.75) in an ionic liquid approach has been carried out. The nanoparticles are characterized by means of energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy. In addition, the role of different processing approaches on the thermoelectric properties - Seebeck coefficient as well as electrical and thermal conductivity - is demonstrated. © 2021 The Authors. Published by The Chemical Society of Japan & Wiley-VCH GmbH
    view abstract10.1002/open.202000257
  • Single-Entity Electrocatalysis of Individual “Picked-and-Dropped” Co3O4 Nanoparticles on the Tip of a Carbon Nanoelectrode
    Quast, T. and Aiyappa, H.B. and Saddeler, S. and Wilde, P. and Chen, Y.-T. and Schulz, S. and Schuhmann, W.
    Angewandte Chemie - International Edition 60 (2021)
    Nano-electrochemical tools to assess individual catalyst entities are critical to comprehend single-entity measurements. The intrinsic electrocatalytic activity of an individual well-defined Co3O4 nanoparticle supported on a carbon-based nanoelectrode is determined by employing an efficient SEM-controlled robotic technique for picking and placing a single catalyst particle onto a modified carbon nanoelectrode surface. The stable nanoassembly is microscopically investigated and subsequently electrochemically characterized. The hexagonal-shaped Co3O4 nanoparticles demonstrate size-dependent electrochemical activity and exhibit very high catalytic activity with a current density of up to 11.5 A cm−2 at 1.92 V (vs. RHE), and a turnover frequency of 532±100 s−1 at 1.92 V (vs. RHE) towards catalyzing the oxygen evolution reaction. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
    view abstract10.1002/anie.202014384
  • Synthesis and Reactivity of Heteroleptic Ga-P-C Allyl Cation Analogues
    Li, B. and Wölper, C. and Haberhauer, G. and Schulz, S.
    Angewandte Chemie - International Edition 60 (2021)
    Oxidative addition of cyclic alkyl(amino)carbene-coordinated phosphinidenes (MecAAC)PX to LGa affords gallium-coordinated phosphinidenes LGa(X)-P(MecAAC) (L=HC[C(Me)N(2,6-i-Pr2C6H3)]2; X=Cl 1, Br 2), which react with NaBArF4 and LiAl(ORF)4 to [LGaP(MecAAC)][An] (An=B(C6H3(CF3)2)4 3, B(C6F5)4 4, Al(OC(CF3)3)4 5). The cations in 3–5 show substantial Ga−P double bond character and represent heteronuclear analogues of allyl cations according to quantum chemical calculations. The reaction of 4 with 4-dimethylaminopyridine (dmap) to adduct 6 confirms the strong electrophilic nature of the gallium center, whereas 5 reacts with ethyl isocyanate with C−C bond formation to the γ-C atom of the β-diketiminate ligand and formation of compound 7. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
    view abstract10.1002/anie.202012595
  • A Mechanistic Study on Reactions of Group 13 Diyls LM with Cp*SbX2: From Stibanyl Radicals to Antimony Hydrides
    Helling, C. and Wölper, C. and Cutsail, G.E., III and Haberhauer, G. and Schulz, S.
    Chemistry - A European Journal 26 (2020)
    Oxidative addition of Cp*SbX2 (X=Cl, Br, I; Cp*=C5Me5) to group 13 diyls LM (M=Al, Ga, In; L=HC[C(Me)N (Dip)]2, Dip=2,6-iPr2C6H3) yields elemental antimony (M=Al) or the corresponding stibanylgallanes [L(X)Ga]Sb(X)Cp* (X=Br 1, I 2) and -indanes [L(X)In]Sb(X)Cp* (X=Cl 5, Br 6, I 7). 1 and 2 react with a second equivalent of LGa to eliminate decamethyl-1,1’-dihydrofulvalene (Cp*2) and form stibanyl radicals [L(X)Ga]2Sb. (X=Br 3, I 4), whereas analogous reactions of 5 and 6 with LIn selectively yield stibanes [L(X)In]2SbH (X=Cl 8, Br 9) by elimination of 1,2,3,4-tetramethylfulvene. The reactions are proposed to proceed via formation of [L(X)M]2SbCp* as reaction intermediate, which is supported by the isolation of [L(Cl)Ga]2SbCp (11, Cp=C5H5). The reaction mechanism was further studied by computational calculations using two different models. The energy values for the Ga- and the In-substituted model systems showing methyl groups instead of the very bulky Dip units are very similar, and in both cases the same products are expected. Homolytic Sb−C bond cleavage yields van der Waals complexes from the as-formed radicals ([L(Cl)M]2Sb. and Cp*.), which can be stabilized by hydrogen atom abstraction to give the corresponding hydrides, whereas the direct formation of Sb hydrides starting from [L(Cl)M]2SbCp* via concerted β-H elimination is unlikely. The consideration of the bulky Dip units reveals that the amount of the steric overload in the intermediate I determines the product formation (radical vs. hydride). © 2020 The Authors. Published by Wiley-VCH GmbH
    view abstract10.1002/chem.202001739
  • A silicon–carbonyl complex stable at room temperature
    Ganesamoorthy, C. and Schoening, J. and Wölper, C. and Song, L. and Schreiner, P.R. and Schulz, S.
    Nature Chemistry 12 (2020)
    Main-group-element compounds with energetically high-lying donor and low-lying acceptor orbitals are able to mimic chemical bonding motifs and reactivity patterns known in transition metal chemistry, including small-molecule activation and catalytic reactions. Monovalent group 13 compounds and divalent group 14 compounds, particularly silylenes, have been shown to be excellent candidates for this purpose. However, one of the most common reactions of transition metal complexes, the direct reaction with carbon monoxide and formation of room-temperature isolable carbonyl complexes, is virtually unknown in main-group-element chemistry. Here, we show the synthesis, single-crystal X-ray structure, and density functional theory computations of a room-temperature-stable silylene carbonyl complex [L(Br)Ga]2Si:–CO (L = HC[C(Me)N(2,6-iPr2-C6H3)]2), which was obtained by direct carbonylation of the electron-rich silylene intermediate [L(Br)Ga]2Si:. Furthermore, [L(Br)Ga]2Si:–CO reacts with H2 and PBr3 with bond activation, whereas the reaction with cyclohexyl isocyanide proceeds with CO substitution. [Figure not available: see fulltext.] © 2020, The Author(s), under exclusive licence to Springer Nature Limited.
    view abstract10.1038/s41557-020-0456-x
  • Active Ga-catalysts for the ring opening homo- And copolymerization of cyclic esters, and copolymerization of epoxide and anhydrides
    Ghosh, S. and Glöckler, E. and Wölper, C. and Tjaberings, A. and Gröschel, A.H. and Schulz, S.
    Dalton Transactions 49 (2020)
    A series of gallium complexes L12Ga4Me8(1), L22Ga4Me8(2), and L32Ga4Me8(3) was synthesized by reaction of GaMe3with Schiff base ligands L1-3H2(L1H2= 2,4-di-tert-butyl-6-{[(3-hydroxypropyl)imino]methyl}phenol; L2H2= 2,4-dichloro-6-{[(3-hydroxypropyl)imino]methyl}phenol; L3H2= 4-tert-butyl-2-{[(3-hydroxypropyl)imino]methyl}phenol) and characterized by1H,13C NMR, IR spectroscopy, elemental analysis and single crystal X-ray analysis (1,2), proving their tetranuclear structure in the solid state. Complexes1-3showed good catalytic activity in the ring opening homopolymerization (ROP) and ring opening copolymerization (ROcoP) of lactide (LA) and ε-caprolactone (ε-CL) in the presence of benzyl alcohol (BnOH) in toluene at 100 °C, yielding polymers with the expected average molecular weights (Mn) and narrow molecular weight distributions (MWD), as well as a high isoselectivity for the ROP ofrac-lactide (rac-LA), yielding isotactic-enriched PLAs withPmvalues up to 0.78. Kinetic studies with complex1proved the first order dependence on monomer concentration, while mechanistic studies confirmed the coordination insertion mechanistic (CIM) pathway. Sequential addition of monomers gave well defined diblock copolymers of PCL-b-PLLA and PLLA-b-PCL, proving the living character of the polymerization reactions. The catalysts also showed perfect selectivity for the copolymerization of cyclohexene oxide (CHO) with both succinic anhydride (SA) and maleic anhydride (MA) in the presence of BnOH and produced >99% alternating block copolymers. © The Royal Society of Chemistry 2020.
    view abstract10.1039/d0dt02831b
  • Direct Synthesis of Pentaarylcyclopentadienyl Sandwich and Half-Sandwich Complexes of s-, p-, and d-Block Metals
    Schulte, Y. and Weinert, H. and Wölper, C. and Schulz, S.
    Organometallics 39 (2020)
    The sterically demanding pentaarylcyclopentadienyl radical CpBIGt-Bu⢠(1; CpBIGt-Bu = Cp(4-t-Bu-Ph)5) reacts with group 2, group 13, and group 14 metal amalgams to form the following complexes of the type CpBIGt-Bu 2M (M = Ca (3), Sr (4), Ba (5)), CpBIGt-BuM (M = Ga (6), In (7), Tl (8)) and CpBIGt-Bu 2M (M = Sn (10), Pb (11)). In addition, metallocenes CpBIG 2Mg (2), CpBIG 2Hg (12), and CpBIG 2Ge (9) were formed in reactions of 1 with magnesium anthracene (2) and elemental mercury (12) as well as by salt metathesis between CpBIGt-BuK and GeCl2·dioxane (9). 6 was found to react with (coe)Cr(CO)5 (coe = cis-cyclooctene) with formation of CpBIGt-BuGaCr(CO)5 (13). 2-13 were characterized by elemental analysis and IR and NMR spectroscopy. In addition, the solid-state structures of 2, 4, 5, and 9-13 were determined by single-crystal X-ray diffraction. Copyright © 2019 American Chemical Society.
    view abstract10.1021/acs.organomet.9b00741
  • Effect of the Size and Shape on the Electrocatalytic Activity of Co3O4Nanoparticles in the Oxygen Evolution Reaction
    Saddeler, S. and Hagemann, U. and Schulz, S.
    Inorganic Chemistry 59 (2020)
    Co3O4 nanoparticles were size- and shape-selectively synthesized in a solvothermal approach by the thermal decomposition of either cobalt(II) acetylacetonate [Co(acac)2] or cobalt(II) nitrate [Co(NO3)2] in different solvents followed by calcination under air. Spherical, cubic, octahedral, and platelike nanoparticles with narrow size distributions and sizes ranging from 8 to 90 nm were formed in high yield. The nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray photoelectron spectroscopy. The distinctive influence of the size and shape of the nanoparticles on the electrocatalytic activity in the oxygen evolution reaction is also demonstrated. Copyright © 2020 American Chemical Society.
    view abstract10.1021/acs.inorgchem.0c01180
  • Electronic effect of a perfluorinated β-diketiminate ligand on the bonding nature of copper carbonyl complexes
    Huse, K. and Weinert, H. and Wölper, C. and Schulz, S.
    Dalton Transactions 49 (2020)
    Two copper complexes 17Fnac2Cu(C6H6) (3) and 17Fnac2CuCO (4) containing the monoanionic, perfluorinated β-diketiminate 17Fnac2- ligand (1) (17Fnac2 = FC[C(CF3)N(C6F5)]2) were synthesized and characterized by IR and NMR spectroscopy (1H, 13C, 19F), cyclovaltammometry (CV), elemental analysis and single crystal X-ray diffraction. The perfluorinated 17Fnac2- ligand marginally reduces the π-back-bonding capacity of the copper centre to the carbonyl group in 4 when compared with the corresponding 16Fnac2- substituted complexes but substantially when compared with the fluorine free substituted derivatives. Quantum chemical calculations gave deeper insight into the bonding situation of this carbonyl complex, while CV studies were performed to determine the oxidation potential of 3 in solution. Based on these data, the influence of the degree of fluorination in different β-diketimine ligands on the electronic nature of the corresponding copper complexes is discussed. © The Royal Society of Chemistry.
    view abstract10.1039/d0dt01943g
  • Heteroleptic β-Ketoiminate Magnesium Catalysts for the Ring-Opening Polymerization of Lactide
    Ghosh, S. and Glöckler, E. and Wölper, C. and Tjaberings, A. and Gröschel, A.H. and Schulz, S.
    Organometallics 39 (2020)
    A series of heteroleptic β-ketoimine magnesium complexes L1L′1Mg2Cp*(1), L22Mg2Cp2(2), L12Mg2(OAr)2(3 and 4), and L22Mg2(OAr)2(5 and 6) (L1= Me2NC2H4NC(Me)CHC(Me)O, L′1= Me2NC2H4NC(CH2)CHC(Me)O, L2= Me2NC3H6NC(Me)CHC(Me)O; Ar = Ph and 2,6-t-Bu2-C6H3) with different steric and electronic properties were synthesized. 1 and 3-6 adopt binuclear structures in the solid state and in solution, whereas 2 forms a monomer/dimer equilibrium in solution. Complexes 1 and 2 showed very poor activity in the ring-opening polymerization (ROP) of racemic-lactide (rac-LA), whereas heteroleptic phenoxide complexes 3-6 are active polymerization catalysts at variable temperature in solution in the absence of any co-initiator, yielding isotactic-enriched polylactide (PLA). The catalytic activity and stereoselectivity is controlled by the electronic and steric properties of the phenoxide substituent and reaction temperature. Kinetic studies with catalyst 3 and 5 proved the first-order dependence on monomer concentration, and mechanistic studies showed that the polymerization reactions follow the coordination insertion mechanism (CIM). © 2020 American Chemical Society. All rights reserved.
    view abstract10.1021/acs.organomet.0c00168
  • Hungry for charge - How a beryllium scorpionate complex "eats" a weakly coordinating anion
    Naglav-Hansen, D. and Dzialkowski, K. and Tobey, B. and Wölper, C. and Jansen, G. and Schulz, S.
    Zeitschrift fur Naturforschung - Section B Journal of Chemical Sciences 75 (2020)
    We present the reaction of a tris(pyrazolyl) beryllium scorpionate (TpBe) complex with a weakly coordinating anion (WCA), which yields the heteroleptic complex TpBeOC(CF3)3 1 (TpBeORF). The product 1 has been characterized by multinuclear NMR spectroscopy (1H, 9Be, 13C) and single-crystal X-ray diffraction (scXRD). Quantum chemical calculations (DFT, NPA, LOL) were performed to study the bonding nature in 1. © 2020 Walter de Gruyter GmbH, Berlin/Boston 2020.
    view abstract10.1515/znb-2020-0034
  • Intermediate snapshot on the insertion reaction of isocyanates into the Zn-Cp∗ bond of dizincocene Cp∗2Zn2
    Li, B. and Wölper, C. and Huse, K. and Schulz, S.
    Chemical Communications 56 (2020)
    Heteroleptic Zn(i) complexes Cp∗Zn-Zn(N(R)C(Cp∗)O) (R = Dipp = 2,6-i-Pr2-C6H32, t-Bu 3) with unsymmetrically η4-coordinated Cp∗ substituents represent snapshots of the insertion reaction of RNCO into the Zn-Cp∗ bond of Cp∗2Zn21. The bonding situation in 2 and 3, which represent the first Zn(i) olefin complexes, was evaluated by computational calculation and further compared to other Zn(i) complexes. © The Royal Society of Chemistry.
    view abstract10.1039/d0cc03831h
  • Ionic Liquid-Based Low-Temperature Synthesis of Phase-Pure Tetradymite-Type Materials and Their Thermoelectric Properties
    Loor, M. and Salloum, S. and Kawulok, P. and Izadi, S. and Bendt, G. and Guschlbauer, J. and Sundermeyer, J. and Perez, N. and Nielsch, K. and Schierning, G. and Schulz, S.
    Inorganic Chemistry 59 (2020)
    Phase-pure crystalline Bi2Se3 and Bi2Te3 nanoparticles are formed in reactions of [C4C1Im]3[Bi3I12] (C4C1Im = 1-butyl-3-methylimidazolium) with [C4C1Pyr][ESiMe3] (E = Se or Te; C4C1Pyr = 1-butyl-1-methylpyrrolidinium) in the ionic liquid (IL) [C4C1Im]I. The resulting crystalline tetradymite-type nanoparticles exhibit stoichiometric Bi:E (E = Se or Te) molar ratios (2:3). Because all synthetic steps were performed under strict inert gas conditions, the surfaces of the Bi2Se3 and Bi2Te3 nanoparticles are free of metal oxide species. As proven by infrared and X-ray photoelectron spectroscopy analyses, the nanoparticle surfaces reveal only minor organic contamination from solvent residues ([C4C1Im]I). The nanomaterials show high Seebeck coefficients of -124 μV K-1 (Bi2Se3) and -155 μV K-1 (Bi2Te3) and feature high electrical conductivities (328 and 946 S cm-1, respectively) at the highest tested temperature (240 °C). The corresponding thermal conductivities (0.8 and 2.3 W m-1 K-1, respectively, at 30 °C) are comparable to those of single crystals and recently reported ab initio calculations, which is in remarkable contrast to typical findings of nanograined bulk materials obtained from compacted nanoparticles. These findings emphasize the low level of impurities, surface contamination, and, in general, defects produced by the synthetic approach reported here. The figure of merit in the in-plane direction of the compacted pellets reached peak values 0.45 for Bi2Se3 and 0.4 for Bi2Te3. © 2020 American Chemical Society.
    view abstract10.1021/acs.inorgchem.9b03060
  • Ligand Effects on the Electronic Structure of Heteroleptic Antimony-Centered Radicals
    Helling, C. and Cutsail, G.E., III and Weinert, H. and Wölper, C. and Schulz, S.
    Angewandte Chemie - International Edition 59 (2020)
    We report on the structures of three unprecedented heteroleptic Sb-centered radicals [L(Cl)Ga](R)Sb. (2-R, R=B[N(Dip)CH]2 2-B, 2,6-Mes2C6H3 2-C, N(SiMe3)Dip 2-N) stabilized by one electropositive metal fragment [L(Cl)Ga] (L=HC[C(Me)N(Dip)]2, Dip=2,6-i-Pr2C6H3) and one bulky B- (2-B), C- (2-C), or N-based (2-N) substituent. Compounds 2-R are predominantly metal-centered radicals. Their electronic properties are largely influenced by the electronic nature of the ligands R, and significant delocalization of unpaired-spin density onto the ligands was observed in 2-B and 2-N. Cyclic voltammetry (CV) studies showed that 2-B undergoes a quasi-reversible one-electron reduction, which was confirmed by the synthesis of [K([2.2.2]crypt)][L(Cl)GaSbB[N(Dip)CH]2] ([K([2.2.2]crypt)][2-B]) containing the stibanyl anion [2-B]−, which was shown to possess significant Sb−B multiple-bonding character. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
    view abstract10.1002/anie.202000586
  • Long-Lived Radicals of the Heavier Group 15 Elements Arsenic, Antimony, and Bismuth
    Helling, C. and Schulz, S.
    European Journal of Inorganic Chemistry 2020 (2020)
    The syntheses and properties of long-lived arsenic, antimony, and bismuth-centered radicals are reviewed. In contrast to the rich phosphorus-based radical chemistry, that of the heavier congeners is far less advanced, which can be attributed to the increased instability of coordinatively and electronically unsaturated heavy main-group element centers. However, the development of new synthetic strategies and stabilization methods particularly in the last decade enabled the isolation and characterization of several unpaired electron-containing heavy group 15 element species featuring various structural motifs and electronic properties. The long-lived character of these radicals allowed for the elucidation of their electronic structures and bonding properties, as well as the exploration of their unique reactivity. © 2020 The Authors published by Wiley-VCH GmbH
    view abstract10.1002/ejic.202000571
  • Metal Complexes of Donor-functionalized Fluorinated β-Ketoiminates – Synthesis, Structure, and CVD Application
    Kaiser, K. and Ganesamoorthy, C. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie 646 (2020)
    Six alkali metal complexes of partly-fluorinated, donor-functionalized β-ketoiminate ligands [L1Li (1), L1Na (2), L1K (3), L1Cs (4), L1 = OC(CF3)CHC(CH3)NCH2CH2OCH3; L2Li (5), L2Na (6), L2 = OC(CF3)CHC(CH3)NCH2CH2N(CH3)2] were prepared and structurally characterized. Reactions of L1Li with PtCl2 gave the homoleptic Pt complex L12Pt (7), which was characterized spectroscopically and by single-crystal X-ray diffraction and whose promising application as CVD precursor (chemical vapor deposition) is shown. Polycrystalline, pure Pt films were grown at 500 °C on SiO2@Si(100) substrates at 10–3 mbar and characterized by XRD, SEM, AFM, EDX and XPS. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
    view abstract10.1002/zaac.201900239
  • Multi-Talented Gallaphosphene for Ga−P−Ga Heteroallyl Cation Generation, CO2 Storage, and C(sp3)−H Bond Activation
    Sharma, M.K. and Wölper, C. and Haberhauer, G. and Schulz, S.
    Angewandte Chemie - International Edition (2020)
    Gallaphosphene L(Cl)GaPGaL (2; L=HC[C(Me)N(2,6-i-Pr2C6H3)]2), which is synthesized by reaction of LGa(Cl)PCO (1) with LGa, reacts with [Na(OCP)(dioxane)2.5] to LGa(OCP)PGaL (3), whereas chloride abstraction with LiBArF4 yields [LGaPGaL][BArF4] (4; BArF4=B(C6F5)4). 4 represents a heteronuclear analog of the allyl cation according to quantum chemical calculations. Remarkably, 2 reversibly reacts with CO2 to yield L(Cl)Ga−P[μ-C(O)O]2GaL (5), while reactions with acetophenone and acetone selectively give compounds 6 and 7 by C(sp3)−H bond activation. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
    view abstract10.1002/anie.202014381
  • On the reversible deactivation of cobalt ferrite spinel nanoparticles applied in selective 2-propanol oxidation
    Anke, S. and Falk, T. and Bendt, G. and Sinev, I. and Hävecker, M. and Antoni, H. and Zegkinoglou, I. and Jeon, H. and Knop-Gericke, A. and Schlögl, R. and Roldan Cuenya, B. and Schulz, S. and Muhler, M.
    Journal of Catalysis 382 (2020)
    CoFe2O4 nanoparticles (NPs) were synthesized by using a colloidal one-pot synthesis method based on the decomposition of metal acetylacetonates in the presence of oleyl amine. The characterization by X-ray diffraction, transmission electron microscopy and N2 physisorption revealed non-porous spinel phase CoFe2O4 NPs with an average particle size of 4 nm. The unsupported metal oxide NPs were applied in the selective oxidation of 2-propanol in a continuously operated fixed-bed reactor under quasi steady-state conditions using a heating rate of 0.5 k min−1. 2-Propanol was found to be oxidatively dehydrogenated over CoFe2O4 yielding acetone and H2O with high selectivity. Only to a minor extent dehydration to propene and total oxidation to CO2 was observed at higher temperatures. The detected low-temperature reaction pathway with maxima at 430 and 510 K was inhibited after the initial 2-propanol oxidation up to 573 K, but an oxidative treatment in O2 or N2O atmosphere led to full regeneration. No correlation between the desorbing amount or the surface oxygen species investigated by O2 temperature-programmed desorption experiments and the low-temperature activity was observed. The amounts of evolving CO2 during the TPO experiments indicate deactivation due to formation of carbonaceous species. Inhibition experiments with pre-adsorbed reaction intermediates and infrared spectroscopy identified acetate species as reversible poison, whereas carbonates are rather spectators. In addition, carbon deposition was detected by X-ray photoelectron spectroscopy, which also revealed a minor influence of cobalt reduction during the deactivation process as confirmed by X-ray absorption spectroscopy studies. © 2019 Elsevier Inc.
    view abstract10.1016/j.jcat.2019.12.007
  • One-step synthesis of carbon-supported electrocatalysts
    Tigges, S. and Wöhrl, N. and Radev, I. and Hagemann, U. and Heidelmann, M. and Nguyen, T.B. and Gorelkov, S. and Schulz, S. and Lorke, A.
    Beilstein Journal of Nanotechnology 11 (2020)
    Cost-efficiency, durability, and reliability of catalysts, as well as their operational lifetime, are the main challenges in chemical energy conversion. Here, we present a novel, one-step approach for the synthesis of Pt/C hybrid material by plasma-enhanced chemical vapor deposition (PE-CVD). The platinum loading, degree of oxidation, and the very narrow particle size distribution are precisely adjusted in the Pt/C hybrid material due to the simultaneous deposition of platinum and carbon during the process. The as-synthesized Pt/C hybrid materials are promising electrocatalysts for use in fuel cell applications as they show significantly improved electrochemical long-term stability compared to the industrial standard HiSPEC 4000. The PE-CVD process is furthermore expected to be extendable to the general deposition of metal-containing carbon materials from other commercially available metal acetylacetonate precursors. © 2020 Tigges et al.; licensee Beilstein-Institut.
    view abstract10.3762/BJNANO.11.126
  • Paving the way to solubility through volatility: Thermodynamics of imidazolium-based ionic liquids of the type [CnC1Im][I]
    Zaitsau, D.H. and Siewert, R. and Pimerzin, A.A. and Bülow, M. and Held, C. and Loor, M. and Schulz, S. and Verevkin, S.P.
    Fluid Phase Equilibria 522 (2020)
    Ionic liquids are effectively used for manufacturing of nanoparticles for thermoelectric generators and in the field of hydrogen storage. Development and optimization of these processes require knowledge of the thermodynamic properties of ionic liquids. Thermochemical study of the series of 1-alkyl-3-methylimidazolium iodides is presented in this work. Vapor pressures and vaporization enthalpies have been measured by using quartz-crystal microbalance. Solution enthalpies were measured by using solution calorimetry. Thermodynamics of aqueous solutions, solubility parameters and miscibility of ILs in eleven organic solvents were derived and discussed. The absence of thermal decomposition of [C4C1Im][I] under vaporization conditions has been demonstrated experimentally and theoretically. It has been shown that vaporization enthalpies are linearly dependent on the chain length of the alkyl substituent and linearly dependent on the surface tension. Aqueous-phase enthalpies of formation of alkyl imidazolium cations have been derived with help of solution calorimetry. © 2020 Elsevier B.V.
    view abstract10.1016/j.fluid.2020.112767
  • Rapid thermal annealing of Sb2Te3 thin films grown via atomic layer deposition
    Tynell, T. and Geishendorf, K. and Piontek, S. and Komossa, T. and Schulz, S. and Nielsch, K. and Thomas, A.
    Thin Solid Films 700 (2020)
    view abstract10.1016/j.tsf.2020.137922
  • Separation and recovery of rare earths by in situ selective electrochemical oxidation and extraction from spent fluid catalytic cracking (FCC) catalysts
    Zhou, Y. and Schulz, S. and Lindoy, L.F. and Du, H. and Zheng, S. and Wenzel, M. and Weigand, J.J.
    Hydrometallurgy 194 (2020)
    An efficient method for recovering and separating Ce3+ and La3+ rare earth elements from spent fluid catalytic cracking (FCC) catalyst is described. Initially, the spent FCC catalyst was leached with 2 M HNO3 at 80 °C then removal of iron from the leach solution was carried out by solvent extraction with 25% (v/v) diisooctyl phosphinic acid (DiOAP) in n-octane. Extraction of the above rare earths was then undertaken from the nitric acid leach solution using an organic phase consisting of 25% (v/v) di(2-ethylhexyl) phosphoric acid (D2EHPA) and 25% (v/v) tri-n-butyl phosphate (TBP) in n-octane. Both rare earths were stripped form the organic phase using H2SO4. Separation of the Ce3+ from La3+ was then achieved by means of an in situ electrochemical oxidation coupled with a simultaneous solvent extraction process. In this, the Ce3+ was electrochemically oxidized to Ce4+ and removed from the aqueous phase by solvent extraction employing 100 mM D2EHPA in n-octane. This led to efficient separation of the above rare earths, giving rise to La3+ in high purity of up to 99.5% and Ce4+ up to 100%. The separation occurs via a single extraction step without the need for pH adjustment or for the use of additional reagents. © 2020 Elsevier B.V.
    view abstract10.1016/j.hydromet.2020.105300
  • Size Matters: Synthesis of Group 13 Metal-Substituted Dipnictanes by E-C Bond Homolysis
    Helling, C. and Wölper, C. and Schulz, S.
    European Journal of Inorganic Chemistry 2020 (2020)
    Pnictanes Cp*(Ph)ECl (E = As 1, Sb 2; Cp* = C5Me5) react with group 13 diyls LM (M = Al, Ga, In; L = HC[C(Me)N(Dip)]2, Dip = 2,6-iPr2C6H3) with oxidative addition of the E-Cl bond to a unique series of metalylpnictanes [L(Cl)M](Ph)ECp* (E = As, M = Al 3, Ga 4, In 5; E = Sb, M = Al 6, Ga 7, In 8). Thermal treatment of 4 and 6–8 results in homolytic E-C bond scission with Cp* radical liberation, yielding the corresponding dipnictanes {[L(Cl)M](Ph)E}2 (E = As, M = Ga 9; E = Sb, M = Al 10, Ga 11, In 12). Compounds 1–12 were characterized by NMR (1H, 13C) and IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction (3–12). © 2020 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH GmbH
    view abstract10.1002/ejic.202000747
  • Stepwise Bi-Bi Bond Formation: From a Bi-centered Radical to Bi4Butterfly and Bi8Cuneane-Type Clusters
    Krüger, J. and Wölper, C. and Schulz, S.
    Inorganic Chemistry 59 (2020)
    In contrast to their lighter homologues (P, As, Sb), the synthesis of polybismuthane clusters is still restricted to classical solid-state approaches. We herein report on systematic reduction reactions of different bismuth precursors with Ga(I) and Mg(I) complexes. This study not only yielded the first metal-coordinated tetrabismuthane ([{L1(Cl)Ga}2-μ,η1:1-Bi4] 3, L1 = HC[C(Me)N(2,6-i-Pr2C6H3)]2) and realgar-type bismuth cluster ([(L2Mg)4(μ4,η2:2:2:2-Bi8)] 4, L2 = HC[C(Me)N(2,4,6-Me3C6H2)]2) in addition to the bismuth-centered radical [L1Ga(Cl)]2Bi• 1 and dibismuthene [L1(Cl)GaBi]2 2, but clearly demonstrates the crucial role of the substituents and the oxidation state of the bismuth precursor as well as the specific reduction potential of the main group metal reductants on the product formation. Compounds 3 and 4 were spectroscopically characterized (1H, 13C NMR, IR), and the structures of 1-4 were determined by single-crystal X-ray diffraction. Computational calculations gave deeper insights into the electronic structures of 1′, 3′, and 4′. Copyright © 2020 American Chemical Society.
    view abstract10.1021/acs.inorgchem.0c01657
  • Syntheses, structures and catalytic activity of tetranuclear Mg complexes in the ROP of cyclic esters under industrially relevant conditions
    Ghosh, S. and Wölper, C. and Tjaberings, A. and Gröschel, A.H. and Schulz, S.
    Dalton Transactions 49 (2020)
    Four tetranuclear magnesium complexes were synthesized and fully characterized. They are excellent catalysts for the ring-opening polymerization (ROP) of bulk racemic-lactide (rac-LA) and ϵ-caprolactone (ϵ-CL) even with low catalyst loading under industrially relevant conditions without additional co-initiators, yielding polymers with high molecular weight (Mn) and moderately controlled molecular weight distribution (MWD). The polymerization activity depends on the steric and electronic properties of the imino(phenolate) ligands. Kinetic studies of the most active catalyst 1 confirmed that the ROP of rac-LA and ϵ-CL has a first order dependence on monomer concentration. The ROP of rac-LA and ϵ-CL using 1-4 with BnOH gave polymers with narrow MWD and a close correlation between Mobsn and Mtheon values. Catalyst 1 was also capable of polymerizing technical-grade rac-LA and ϵ-CL even with large monomer-to-catalyst ratios ([M]0/[C]0) of up to 10 000 : 1 and without any additional co-initiator. The very high turnover frequencies (TOF) of 9600 h-1 (rac-LA) and 24 000 h-1 (ϵ-CL) prove that 1 belongs to the most active biocompatible, sustainable and nontoxic ROP catalysts under industrially relevant conditions. © 2020 The Royal Society of Chemistry.
    view abstract10.1039/c9dt04359d
  • Synthesis of heteroleptic gallium-substituted antimony hydrides by stepwise β-H elimination
    Helling, C. and Wölper, C. and Schulz, S.
    Dalton Transactions 49 (2020)
    Heteroleptic stibanes Cp*(R)SbCl (R = Dip1, N(SiMe3)22, OB(NDipCH)23; Cp* = C5Me5; Dip = 2,6-i-Pr2-C6H3) react with monovalent gallanediyl LGa (L = HC[C(Me)N(Dip)]2) with elimination of 1,2,3,4-tetramethylfulvene, yielding heteroleptic metal-stabilized Sb hydrides [L(Cl)Ga](R)SbH (R = Dip4, N(SiMe3)25, OB(NDipCH)26). Compounds1-6were characterized by heteronuclear NMR (1H,11B,13C) and IR spectroscopy, and the solid-state structures of4-6were determined by single-crystal X-ray diffraction. A close correlation between the1H NMR chemical shift of the hydride ligand and the electronegativity of the Sb-coordinating atoms was revealed. © The Royal Society of Chemistry 2020.
    view abstract10.1039/d0dt01937b
  • Synthesis of Homo- and Heteroleptic Al, Ga and Zn Complexes Containing (Per)fluorinated β-Diketiminate Ligands
    Huse, K. and Li, B. and Ghosh, S. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie (2020)
    Alkane elimination reactions of equimolar amounts of 17Fnac2H (17Fnac2H = FC[C(CF3)NC6F5]2H) with ZnEt2 and AlMe3 as well as 16Fnac2H (16Fnac2H = HC[C(CF3)NC6F5]2H) with GaMe3 yielded the corresponding heteroleptic complexes of 17Fnac2ZnEt (1), 17Fnac2AlMe2 (2), and 16Fnac2GaMe2 (3), whereas reactions of two equivalents of 16Fnac2H and 17Fnac2H with either ZnEt2 or Cp*2Zn gave homoleptic ZnII complexes (16Fnac2)2Zn (4) and (17Fnac2)2Zn (5), respectively. 1–5 were characterized by IR and NMR spectroscopy (1H, 13C, 19F), elemental analysis and single-crystal X-ray diffraction. © 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie published by Wiley-VCH GmbH
    view abstract10.1002/zaac.202000305
  • Transition into a phonon glass in crystalline thermoelectric (S b1-x B ix)2 T e3 films
    Rieger, F. and Roddatis, V. and Kaiser, K. and Bendt, G. and Schulz, S. and Jooss, C.
    Physical Review Materials 4 (2020)
    Gaining fundamental insights into phonon interactions is of high importance for the improvement of thermoelectric materials. The particular challenge is to enable a phonon glass state with low thermal conductivity in crystalline materials with high electron conductivity. We present here the relation between atomic structure and c-axis lattice thermal conductivity κc,l(T) of epitaxially grown nearly single crystalline (Sb1-xBix)2Te3 thin films. Aberration corrected high-resolution transmission electron microscopy shows a highly ordered crystalline lattice, with doping dependent statistical occupation of the Sb sublattice by Bi atoms and a very low density of planar defects. The observed strong decrease of κc,l(T) with doping is due to an increase both of the Rayleigh scattering rate at point defects as well as of the phonon-phonon scattering rate. For x=0.24 a transition to a low, almost temperature independent κc,l(T) is observed, indicating a transition to a phonon glass state. The theoretical calculations reveal that the phonon mean free path is reduced below the phonon wavelength for the majority of phonon frequencies, suggesting a breakdown of the phonon approximation to heat transport due to the strongly anharmonic lattice. © 2020 American Physical Society.
    view abstract10.1103/PhysRevMaterials.4.025402
  • Erratum: Intrinsic activity of oxygen evolution catalysts probed at single CoFe2O4 nanoparticles (Journal of Medicinal Chemistry (2019) 141:23 (9197-9201) DOI: 10.1021/jacs.9b04516)
    El Arrassi, A. and Liu, Z. and Evers, M.V. and Blanc, N. and Bendt, G. and Saddeler, S. and Tetzlaff, D. and Pohl, D. and Damm, C. and Schulz, S. and Tschulik, K.
    Journal of the American Chemical Society 141 (2019)
    Page 9199, sentence directly below caption of Figure 5: Error in “no correlation is seen when plotting the step duration as a function of the step height in Figure 4b.” This should refer to Figure 5b as correctly written in the sentence below: “no correlation is seen when plotting the step duration as a function of the step height in Figure 5b”. © 2019 American Chemical Society.
    view abstract10.1021/jacs.9b06330
  • Heterolepic β-Ketoiminate Zinc Phenoxide Complexes as Efficient Catalysts for the Ring Opening Polymerization of Lactide
    Ghosh, S. and Schäfer, P.M. and Dittrich, D. and Scheiper, C. and Steiniger, P. and Fink, G. and Ksiazkiewicz, A.N. and Tjaberings, A. and Wölper, C. and Gröschel, A.H. and Pich, A. and Herres-Pawlis, S. and Schulz, S.
    ChemistryOpen 8 (2019)
    Zinc phenoxide complexes L1ZnOAr 1–4 (L1=Me2NC2H4NC(Me)CHC(Me)O) and L2ZnOAr 5–8 (L2=Me2NC3H6NC(Me)CHC(Me)O) with donor-functionalized β-ketoiminate ligands (L1/2) and OAr substituents (Ar=Ph 1, 5; 2,6-Me2-C6H3 2, 6; 3,5-Me2-C6H3 3, 7; 4-Bu-C6H4 4, 8) with tuneable electronic and steric properties were synthesized and characterized. 1–8 adopt binuclear structures in the solid state except for 5, while they are monomeric in CDCl3 solution. 1–8 are active catalysts for the ring opening polymerization (ROP) of lactide (LA) in CH2Cl2 at ambient temperature and the catalytic activity is controlled by the electronic and steric properties of the OAr substituent, yielding polymers with high average molecular weight (Mn) and moderately controlled molecular weight distribution (MWDs). 1 and 5 showed a living polymerization character and kinetic studies on the ROP of L–LA with 1 and 5 proved first order dependencies on the monomer concentration. Homonuclear decoupled 1H-NMR analyses of polylactic acid (PLA) formed with rac-LA proved isotactic enrichment of the PLA microstructure. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
    view abstract10.1002/open.201900203
  • Intrinsic Activity of Oxygen Evolution Catalysts Probed at Single CoFe2O4 Nanoparticles
    El Arrassi, A. and Liu, Z. and Evers, M.V. and Blanc, N. and Bendt, G. and Saddeler, S. and Tetzlaff, D. and Pohl, D. and Damm, C. and Schulz, S. and Tschulik, K.
    Journal of the American Chemical Society 141 (2019)
    Identifying the intrinsic electrocatalytic activity of nanomaterials is challenging, as their characterization usually requires additives and binders whose contributions are difficult to dissect. Herein, we use nano impact electrochemistry as an additive-free method to overcome this problem. Due to the efficient mass transport at individual catalyst nanoparticles, high current densities can be realized. High-resolution bright-field transmission electron microscopy and selected area diffraction studies of the catalyst particles before and after the experiments provide valuable insights in the transformation of the nanomaterials during harsh oxygen evolution reaction (OER) conditions. We demonstrate this for 4 nm sized CoFe2O4 spinel nanoparticles. It is revealed that these particles retain their size and crystal structure even after OER at current densities as high as several kA·m-2. The steady-state current scales with the particle size distribution and is limited by the diffusion of produced oxygen away from the particle. This versatilely applicable method provides new insights into intrinsic nanocatalyst activities, which is key to the efficient development of improved and precious metal-free catalysts for renewable energy technologies. © 2019 American Chemical Society.
    view abstract10.1021/jacs.9b04516
  • Role of London Dispersion Interactions in Ga-Substituted Dipnictenes
    Song, L. and Schoening, J. and Wölper, C. and Schulz, S. and Schreiner, P.R.
    Organometallics 38 (2019)
    We report the synthesis and structural characterization of Ga-substituted diarsene [L(EtO)GaAs]2, which is an exemplary case of a Ga-substituted dipnictene of the general type [L(X)Ga]2E2 (L = C[C(Me)N(2,6-i-Pr2-C6H3)]2, X = F, Cl, Br, I, NMe2, OEt; E = As, Sb, Bi). We examined this extended series of compounds computationally and found that attractive London dispersion interactions between the substituents on the N,N′-chelating β-diketiminate ligands as well as pnictogen-π interactions between the group 15 metal center and the ligand are key factors for the stability and the electronic structures of such types of complexes. © 2019 American Chemical Society.
    view abstract10.1021/acs.organomet.9b00072
  • Selective 2-Propanol Oxidation over Unsupported Co3O4 Spinel Nanoparticles: Mechanistic Insights into Aerobic Oxidation of Alcohols
    Anke, S. and Bendt, G. and Sinev, I. and Hajiyani, H. and Antoni, H. and Zegkinoglou, I. and Jeon, H. and Pentcheva, R. and Roldan Cuenya, B. and Schulz, S. and Muhler, M.
    ACS Catalysis 9 (2019)
    Crystalline Co3O4 nanoparticles with a uniform size of 9 nm as shown by X-ray diffraction (XRD) and transmission electron microscopy (TEM) were synthesized by thermal decomposition of cobalt acetylacetonate in oleylamine and applied in the oxidation of 2-propanol after calcination. The catalytic properties were derived under continuous flow conditions as a function of temperature up to 573 K in a fixed-bed reactor at atmospheric pressure. Temperature-programmed oxidation, desorption (TPD), surface reaction (TPSR), and 2-propanol decomposition experiments were performed to study the interaction of 2-propanol and O2 with the exposed spinel surfaces. Co3O4 selectively catalyzes the oxidative dehydrogenation of 2-propanol, yielding acetone and H2O and only to a minor extent the total oxidation to CO2 and H2O at higher temperatures. The high catalytic activity of Co3O4 reaching nearly full conversion with 100% selectivity to acetone at 430 K is attributed to the high amount of active Co3+ species at the catalyst surface as well as surface-bound reactive oxygen species observed in the O2 TPD, 2-propanol TPD, TPSR, and 2-propanol decomposition experiments. Density functional theory calculations with a Hubbard U term support the identification of the 5-fold-coordinated octahedral surface Co5c3+ as the active site, and oxidative dehydrogenation involving adsorbed atomic oxygen was found to be the energetically most favored pathway. The consumption of surface oxygen and reduction of Co3+ to Co2+ during 2-propanol oxidation derived from X-ray absorption spectroscopy and X-ray photoelectron spectroscopy measurements before and after reaction and poisoning by strongly bound carbonaceous species result in the loss of the low-temperature activity, while the high-temperature reaction pathway remained unaffected. © 2019 American Chemical Society.
    view abstract10.1021/acscatal.9b01048
  • Structure and Reactivity of 1,8-Bis(naphthalenediyl)dipnictanes
    Dzialkowski, K. and Gehlhaar, A. and Wölper, C. and Auer, A.A. and Schulz, S.
    Organometallics 38 (2019)
    Syntheses and solid-state structures of diarsane Naph2As2 (Naph = 1,8-naphthalenediyl, 1) and (Naph)5Sb4Cl2 3 are reported and the σ-donor capacity of Naph2E2 (E = As 1, Sb 2) was studied in reactions with (coe)Cr(CO)5 (coe = Z-cyclooctene), yielding [Naph2As2][Cr(CO)5]2 (4) and [Naph2E2][Cr(CO)5] (E = As 5, Sb 6). In contrast, reactions of 1 and 3 with Me2SAuCl proceed with oxidation and formation of elemental gold as well as Naph2(AsCl)2 (7) and [NaphSbCl2]2 8. All complexes were characterized by elemental analyses, heteronuclear (1H, 13C) NMR and FT-IR spectroscopy, as well as single crystal X-ray diffraction. Intermolecular E···πinteractions (E = As, Sb), which were observed in 7 and 8, were quantified by use of density functional theory and local coupled cluster electronic structure theory calculations. These allow to assess the nature and relative importance of covalent and noncovalent interactions and illustrate how dispersion interactions change with the electronic structure of the compounds. © 2019 American Chemical Society.
    view abstract10.1021/acs.organomet.9b00269
  • Sulfidation of Magnetite Nanoparticles – Following the Polysulfide Pathway
    Bendt, G. and Saddeler, S. and Schulz, S.
    European Journal of Inorganic Chemistry 2019 (2019)
    The in-situ sulfidation of sub-10 nm sized Fe 3 O 4 and partial-substituted Co x Fe 3–x O 4 (x = 0.25–0.75) nanoparticles by hot-injection of sulfur dissolved in oleylamine (OA) is strongly time- and temperature dependent. Fe 3 O 4 nanoparticles are completely converted within 5 minutes into Fe 3 S 4 nanoparticles with preservation of the spinel structure at 250 °C, whereas higher reaction temperatures and prolonged reaction times result in additional sulfur uptake and formation of pyrite FeS 2 nanoparticles. The formation of the cubic (Co,Fe)S 2 phase was observed in sulfidation reactions of Co x Fe 3–x O 4 , even with low Co substitution levels (x = 0.25). The chemical composition, morphology, and phase purity of the resulting nanoparticles were investigated by EDX, XRD, TEM, and XPS. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/ejic.201801075
  • Synergistic Effects of Mo2C-NC@CoxFey Core–Shell Nanoparticles in Electrocatalytic Overall Water Splitting Reaction
    Wang, S. and Bendt, G. and Saddeler, S. and Schulz, S.
    Energy Technology 7 (2019)
    Transition metals (TMs) are highly investigated as nonprecious electrocatalysts for hydrogen evolution (HER) and oxygen evolution (OER) reactions. There is a strong demand for highly efficient and inexpensive catalysts for overall water splitting. Herein, the bimetallic CoxFey alloy nanoparticles encapsulated in a N-doped graphene shell containing molybdenum carbide (Mo2C) nanoparticles are synthesized by the pyrolysis of cobalt ferrite (CoxFe3−xO4) nanoparticles coated by melamine-formaldehyde resin cross-linked with molybdic acid. Molybdic acid not only serves as precursor for the formation of highly dispersed Mo2C nanoparticles in the N-doped graphene shell but also enhances the thermal stability of the organic shell, resulting in the formation of smaller CoxFey cores. The formation of Mo2C nanoparticles in the graphene shell is promoted by the CoxFe3−xO4 core. Interestingly, the synergistic presence of Mo2C nanoparticles not only enhances the HER activity of the material but also renders a partial breakage of the graphene shell, which increases the surface concentration of OER-active Co and therefore enhances the OER activity. The as-prepared TM-based materials serve as bifunctional catalysts for the overall water splitting and exhibit improved electrocatalytic performances compared to standard cells based on precious metals, with the potentials of 1.53 and 1.60 V at 10 and 20 mA cm−2 in alkaline media, respectively. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/ente.201801121
  • Syntheses, Structures, and Bonding Analyses of Carbene-Stabilized Stibinidenes
    Krüger, J. and Wölper, C. and John, L. and Song, L. and Schreiner, P.R. and Schulz, S.
    European Journal of Inorganic Chemistry 2019 (2019)
    Reactions of two equivalents of LGa {L = HC[C(Me)NAr] 2 ; Ar = 2,6-iPr 2 -C 6 H 3 } with SbX 3 (X = Cl, Br) yield double-inserted products (LGaX) 2 SbX (X = Cl 1, Br 2), which were isolated at –40 °C. Warming solutions of 1 and 2 to ambient temperature results in intramolecular elimination of LGaX 2 and formation of Ga-substituted stibinidenes L(X)GaSb as reaction intermediates, which were stabilized by coordination of strong σ-donating carbenes. Four carbene-stabilized stibinidenes Me CAAC-SbGa(X)L { Me CAAC = [H 2 C(CMe 2 ) 2 NAr]C, Ar = 2,6-iPr 2 -C 6 H 3 , X = Cl 3, Br 4} and IDipp-SbGa(X)L {IDipp = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene, X = Cl 5, Br 6} were characterized by single-crystal X-ray diffraction and the nature of the bonding in 3–6 was further investigated by quantum chemical methods. The studies reveal substantial Sb–C c arbene π-backbonding contributions in 3 and 4, whereas the IDipp-stabilized derivatives 5 and 6 exhibit Sb–C c arbene single bonds. DFT computations with and without dispersion corrections reveal that dispersion interactions mainly from the bulky aryl groups decisively contribute to the stability of 3–6. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/ejic.201900167
  • Synthesis and structures of gallaarsenes LGaAsGa(X)L featuring a Ga-As double bond
    Schoening, J. and John, L. and Wölper, C. and Schulz, S.
    Dalton Transactions 48 (2019)
    Three equivalents of LGa {L = HC[C(Me)N(2,6-i-Pr2C6H3)]2} react with AsX3 (X = Cl, Br) by insertion into two As-X bonds, followed by the elimination of LGaX2 and formation of LGaAsGa(Cl)L (1) and LGaAsGa(Br)L (2). According to single crystal X-ray analysis, 1 and 2 each exhibit one Ga-As single bond and one Ga-As double bond. The π-bonding contribution (9.71 kcal mol-11 and 9.44 kcal mol-12) was proved by variable temperature (VT) 1H NMR spectroscopy, while the electronic structure of 1′ was studied by quantum chemical calculations. This journal is © The Royal Society of Chemistry.
    view abstract10.1039/c9dt03998h
  • Synthesis and structures of s- and p-block metal complexes containing sterically demanding pentaarylcyclopentadienyl substituents
    Schulte, Y. and Stienen, C. and Wölper, C. and Schulz, S.
    Organometallics 38 (2019)
    The synthesis of alkali metal salts of sterically demanding cyclopentadienyls CpBIGi-PrM (CpBIGi-Pr = Cp(4-i-Pr-Ph)5; M = Li 1, Na 2, K 3, Rb 4, Cs 5), CpBIGn-BuM (CpBIGn-Bu = Cp(4-n-Bu-Ph)5; M = Li 6, Na 7, K 8, Rb 9, Cs 10), and CpBIGt-BuM (CpBIGt-Bu = Cp(4-t-Bu-Ph)5; M = Li 11, Na 12, K 13, Rb 14, Cs 15) and their complete characterization including IR and heteronuclear (1H, 13C, 7Li, 23Na, 87Rb, 133Cs) NMR spectroscopy are reported. In addition, the solid-state structures of 5, 10, 11, and 13 were determined by single-crystal X-ray diffraction, revealing the formation of infinite one-dimensional chain structures in the solid state (5, 10) or solvent-separated ion pairs (11, 13). Salt elimination reactions of CpBIGt-BuK 13 with ECl3 yielded the monosubstituted cyclopentadienyl compounds CpBIGt-BuECl2 (E = P 16, As 17, Sb 18, Bi 19), which were characterized by elemental analysis, IR, and heteronuclear (1H, 13C, 31P) NMR spectroscopy and single-crystal X-ray diffraction (17). © 2019 American Chemical Society.
    view abstract10.1021/acs.organomet.9b00203
  • Synthesis of a Ga-Stabilized As-Centered Radical and a Gallastibene by Tailoring Group 15 Element-Carbon Bond Strengths
    Helling, C. and Wölper, C. and Schulte, Y. and Cutsail, G.E. and Schulz, S.
    Inorganic Chemistry 58 (2019)
    A convenient synthetic route to Ga-stabilized pnictogen-centered radicals and gallapnictenes by manipulation of pnictogen-carbon bond strengths is presented. Two equivalents of LGa (L = HC[C(Me)N(Dip)]2, Dip = 2,6-i-Pr2C6H3) react with CpArAsCl2 (CpAr = C5(4-T. © 2019 American Chemical Society.
    view abstract10.1021/acs.inorgchem.9b01519
  • A General Pathway for the Synthesis of Gallastibenes containing Ga=Sb Double Bonds
    Krüger, J. and Ganesamoorthy, C. and John, L. and Wölper, C. and Schulz, S.
    Chemistry - A European Journal 24 (2018)
    Reactions of three equivalents of LGa {L=HC[C(Me)N(2,6-iPr2C6H3)]2} with SbX3 (X=F, Cl, Br, I) proceed with insertion into the Sb−X bond, elimination of LGaX2, and formation of LGaSbGa(X)L (X=F 1, Cl 2, Br 3, I 4) containing a Ga=Sb double bond. In contrast, the 2:1 molar ratio reaction of LGa and SbCl3 initially gives the twofold insertion product [L(Cl)Ga]2SbCl 7, which could not be isolated due to its strong tendency toward elimination of LGaCl2 and formation of distibene [L(Cl)GaSb]2 5 at 25 °C or cyclotristibine [L(Cl)GaSb]3 6 at 8 °C. The formation of 1–6 can be rationalized by formation of the Ga-substituted stibinidene L(X)GaSb as reaction intermediate. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/chem.201801813
  • A General Route to Metal-Substituted Dipnictenes of the Type [L(X)M]2E2
    Tuscher, L. and Helling, C. and Wölper, C. and Frank, W. and Nizovtsev, A.S. and Schulz, S.
    Chemistry - A European Journal (2018)
    Two equivalents of LGa (L=HC[C(Me)N(2,6-iPr2C6H3)]2) reacted with PX3 (X=Cl, Br) with insertion into two P-X bonds and formation of [L(X)Ga]2PX (X=Cl 1, Br 2), whereas the analogous reaction with AsCl3 occurred with twofold insertion and subsequent elimination of LGaCl2 and formation of the Ga-substituted diarsene [L(Cl)Ga]2As2 (3). Analogous findings were observed in the reactions with Me2NAsCl2, yielding the unsymmetrically-substituted diarsene [L(Cl)Ga]As=As[Ga(NMe2)L] (4). The reaction of As(NMe2)3 with LGa gave [L(Me2N)Ga]2As2 (5) after heating at 165°C for five days, whereas the reaction with LAl gave [L(Me2N)Al]2As2 (6) after heating at only 80°C for one day. Finally, two equivalents of LGa reacted with Bi(NEt2)3 to give [L(Et2N)Ga]2Bi2 (7). Complexes 1-7 were characterized by NMR spectroscopy (1H, 13C, 31P), elemental analysis, and single-crystal X-ray diffraction (except for 1 and 5). The bonding situations in 4, 6, and 7 were analyzed by quantum chemical calculations. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/chem.201705233
  • Comprehensive Study on Reactions of Group 13 Diyls with Tetraorganodipentelanes
    Ganesamoorthy, C. and Krüger, J. and Glöckler, E. and Helling, C. and John, L. and Frank, W. and Wölper, C. and Schulz, S.
    Inorganic Chemistry 57 (2018)
    L1Ga {L1 = HC[C(Me)N(2,6-iPr2C6H3)]2} reversibly reacts with E2Ph4 (E = Sb, Bi) in a temperature-dependent equilibrium reaction with insertion into the E-E bond and formation of L1Ga(EPh2)2 (E = Sb 1, Bi 2). Analogous findings were observed in the reactions of L2Ga {L2 = (C6H11)2NC[N(2,6-iPr2C6H3)]2} with E2R4 (R = Ph, Et), yielding L2Ga(EPh2)2 (E = Sb 3, Bi 4) and L2Ga(EEt2)2 (E = Sb 5, Bi 6). 1-3 and 5 were isolated by fractional crystallization at low temperature, whereas 4 and 6 could not be isolated in their pure form even at low temperature. In contrast, reactions of [Cp∗Al]4 (Cp∗ = C5Me5) with Sb2R4 (R = Ph, Et) and Bi2Et4 did not proceed with insertion into the E-E bonds but with formation of (Cp∗Al)3E2 (E = Sb, 7; Bi, 8), whereas the reaction with Bi2Ph4 yielded metallic bismuth. 8 was also formed in the reaction of [Cp∗Al]4 and BiEt3 at ambient temperature, whereas the analogous reaction of [Cp∗Al]4 with SbEt3 did not yield 7 even under drastic reaction conditions (120 °C, 3 days). In contrast, Cp∗Ga and Sb2R4 (R = Ph, Et) were found to react only at elevated temperature (120 °C) with formation of antimony metal. Copyright © 2018 American Chemical Society.
    view abstract10.1021/acs.inorgchem.8b01489
  • Dispersion interactions between neighboring Bi atoms in (BiH3)2 and Te(BiR2)2
    Haack, R. and Schulz, S. and Jansen, G.
    Journal of Computational Chemistry 39 (2018)
    Triggered by the observation of a short Bi⋯Bi distance and a BiTeBi bond angle of only 86.6° in the crystal structure of bis(diethylbismuthanyl)tellurane quantum chemical computations on interactions between neighboring Bi atoms in Te(BiR2)2 molecules (R = H, Me, Et) and in (BiH3)2 were undertaken. Bi⋯Bi distances atoms were found to significantly shorten upon inclusion of the d shells of the heavy metal atoms into the electron correlation treatment, and it was confirmed that interaction energies from spin component-scaled second-order Møller–Plesset theory (SCS-MP2) agree well with coupled-cluster singles and doubles theory including perturbative triples (CCSD(T)). Density functional theory-based symmetry-adapted perturbation theory (DFT-SAPT) was used to study the anisotropy of the interplay of dispersion attraction and steric repulsion between the Bi atoms. Finally, geometries and relative stabilities of syn–syn and syn–anti conformers of Te(BiR2)2 (R = H, Me, Et) and interconversion barriers between them were computed. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.
    view abstract10.1002/jcc.25209
  • From stable Sb- and Bi-centered radicals to a compound with a Ga=Sb double bond
    Ganesamoorthy, C. and Helling, C. and Wölper, C. and Frank, W. and Bill, E. and Cutsail, G.E. and Schulz, S.
    Nature Communications 9 (2018)
    Neutral stibinyl and bismuthinyl radicals are typically short-lived, reactive species. Here we show the synthesis and solid-state structures of two stable stibinyl [L(Cl)Ga]2Sb· 1 and bismuthinyl radicals [L(I)Ga]2Bi· 4, which are stabilized by electropositive metal centers. Their description as predominantly metal-centered radicals is consistent with the results of NMR, EPR, SQUID, and DFT studies. The Lewis-acidic character of the Ga ligands allow for significant electron delocalization of the Sb- and Bi- unpaired radical onto the ligand. Single-electron reduction of [L(Cl)Ga]2Sb· gave LGaSbGa(Cl)L 5, the first compound containing a Ga=Sb double bond. The π-bonding contribution is estimated to 9.56 kcal mol-1 by NMR spectroscopy. The bonding situation and electronic structure is analyzed by quantum mechanical computations, revealing significant π backdonation from the Sb to the Ga atom. The formation of 5 illustrates the high-synthetic potential of 1 for the formation of new compounds with unusual electronic structures. © 2017 The Author(s).
    view abstract10.1038/s41467-017-02581-2
  • Low intrinsic c-axis thermal conductivity in PVD grown epitaxial Sb2Te3 films
    Rieger, F. and Kaiser, K. and Bendt, G. and Roddatis, V. and Thiessen, P. and Schulz, S. and Jooss, C.
    Journal of Applied Physics 123 (2018)
    Accurate determination and comprehensive understanding of the intrinsic c-axis thermal conductivity κc of thermoelectric layered Sb2Te3 is of high importance for the development of strategies to optimize the figure of merit in thin film devices via heterostructures and defect engineering. We present here high precision measurements of κc of epitaxial Sb2Te3 thin films on Al2O3 substrates grown by physical vapor deposition in the temperature range of 100 K to 300 K. The Kapitza resistances of the involved interfaces have been determined and subtracted from the film data, allowing access to the intrinsic thermal conductivity of single crystalline Sb2Te3. At room temperature, we obtain κc = 1.9 W/m K, being much smaller than the in-plane thermal conductivity of κab = 5 W/m K and even lower than the thermal conductivity of nano crystalline films of κnc ≈ 2.0-2.6 W/m K published by Park et al. [Nanoscale Res. Lett. 9, 96 (2014)]. High crystallinity and very low defect concentration of the films were confirmed by x-ray diffraction and high resolution transmission electron microscopy. Our data reveal that the phonon mean free path lmfpT is not limited by defect scattering and is of intrinsic nature, i.e., due to phonon-phonon scattering similar to other soft van der Waals type bonded layered systems. © 2018 Author(s).
    view abstract10.1063/1.5025491
  • Low-temperature MOCVD deposition of Bi2Te3 thin films using Et2BiTeEt as single source precursor
    Bendt, G. and Gassa, S. and Rieger, F. and Jooss, C. and Schulz, S.
    Journal of Crystal Growth 490 (2018)
    Et2BiTeEt was used as single source precursor for the deposition of Bi2Te3 thin films on Si(1 0 0) substrates by metal organic chemical vapor deposition (MOCVD) at very low substrate temperatures. Stoichiometric and crystalline Bi2Te3 films were grown at 230 °C, which is approximately 100 °C lower compared to conventional MOCVD processes using one metal organic precursors for each element. The Bi2Te3 films were characterized using scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. The elemental composition of the films, which was determined by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, was found to be strongly dependent of the substrate temperature. © 2018 Elsevier B.V.
    view abstract10.1016/j.jcrysgro.2018.03.021
  • Main-Group-Metal and Transition-Metal Complexes Containing Fluorinated β-Diketiminate Ligands
    Huse, K. and Wölper, C. and Schulz, S.
    European Journal of Inorganic Chemistry 2018 (2018)
    The synthesis of fluorinated β-diketimine LH 1 (L = HC[C(CF3)NC6F5]2) and its reactions with main-group-metal and transition-metal complexes, yielding LAlMe2 4, LZnEt 5, LCu(C6D6) 6 and LCuCO 7, is reported. 1–7 were characterized by IR and NMR spectroscopy (1H, 13C, 19F), elemental analysis and single-crystal X-ray diffraction. The C6F5 substituents strongly reduce the π-back-bonding capacity of the β-diketiminate ligand as was shown for 7 by IR spectroscopy. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/ejic.201800414
  • Solvent-induced ion separation of a beryllium scorpionate complex
    Naglav, D. and Tobey, B. and Dzialkowski, K. and Bläser, D. and Wölper, C. and Jansen, G. and Schulz, S.
    Dalton Transactions 47 (2018)
    Spontaneous ion separation of the scorpionate beryllium complex, TpBeI 1 (Tp = 1-trispyrazolylborate), occurs upon treatment with THF, yielding [TpBe(thf)]I 2, which was characterized by heteronuclear NMR spectroscopy (1H, 9Be, 13C) and structurally characterized by single crystal X-ray diffraction. 2 represents a rare example of a structurally characterized monocationic beryllium complex, and to the best of our knowledge, the synthesis of 2 by a solvent-induced ion separation has previously only been observed in the reactions of beryllium dihalides with strong Lewis bases. © 2018 The Royal Society of Chemistry.
    view abstract10.1039/c8dt01640b
  • Structural and thermoelectrical characterization of epitaxial Sb2Te3 high quality thin films grown by thermal evaporation
    Bendt, G. and Kaiser, K. and Heckel, A. and Rieger, F. and Oing, D. and Lorke, A. and Rodriguez, N.P. and Schierning, G. and Jooss, C. and Schulz, S.
    Semiconductor Science and Technology 33 (2018)
    Thermal evaporation of Sb2Te3 powder was systematically studied under various pressure and temperature conditions. Low pressure experiments (5 •10-6 mbar) conducted inside a horizontal tube reactor at a temperature range of 500 °C-600 °C generated rough polycrystalline films on Si(100) substrates. Based on these experiments, the chemical composition of the resulting films were determined by the furnace temperature. Enhancing the reactor pressure to 20 mbar shifted the growth zone towards higher temperature ranges and yielded highly c-oriented Sb2Te3 films on Si(100) and Al2O3(0001) substrates. Additional experiments were conducted inside a special reactor containing two independent heaters to study the effects of the evaporator and substrate temperatures independently. In contrast to the samples generated in the previous reactor, a two-zone heating reactor allowed the growth of epitaxial Sb2Te3 films with a very smooth surface topology on Al2O3(0001) substrates, as shown by SEM, EDX, XPS, and HRTEM. The electrical in-plane conductivity of the Sb2Te3 films decreased with increasing temperature, ultimately reaching 3950 S •cm-1 at 300 K. The films showed a p-type carrier concentration of 4.3 •10-19 cm-3 at 300 K and a very high carrier mobility of 558 cm2 •V-1 •s-1. The Seebeck coefficient increased monotonically from 94 μV •K-1 at 270 K to 127 μV •K-1 at 420 K. © 2018 IOP Publishing Ltd.
    view abstract10.1088/1361-6641/aad7a3
  • Synthesis and solid-state structures of t-Bu3Ga–EPh3 Lewis acid–base adducts
    Heckel, A. and Bendt, G. and John, L. and Wölper, C. and Schulz, S.
    Applied Organometallic Chemistry 32 (2018)
    Three Lewis acid–base adducts t-Bu3Ga–EPh3 (E = P 1, As 2, Sb 3) were synthesized by reactions of Ph3E and t-Bu3Ga and characterized by heteronuclear NMR (1H, 13C (31P)) and IR spectroscopy, elemental analysis and single crystal X-ray diffraction. Their structural parameters are discussed and compared to similar t-Bu3Ga adducts. The strength of the donor-acceptor interactions within 1–3 was investigated in solution by temperature-dependent 1H NMR spectroscopy and by quantum chemical calculations. Copyright © 2018 John Wiley & Sons, Ltd.
    view abstract10.1002/aoc.4430
  • Synthesis and X-ray Crystal Structures of Ga-substituted Distibenes [L(X)GaSb]2
    Krüger, J. and Schoening, J. and Ganesamoorthy, C. and John, L. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie 644 (2018)
    The reactions of two equivalents of LGa {L = HC[C(Me)N(2,6-iPr2C6H3)]2} with SbX3 (X = Br, I, OEt) proceed with elimination of LGaX2 and formation of Ga-substituted distibenes [L(X)GaSb]2 [X = Br (1), I (2), OEt (3)]. Compounds 1 to 3 were characterized by heteronuclear NMR (1H, 13C), IR and UV/Vis spectroscopy, elemental analysis, and single-crystal X-ray diffraction. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/zaac.201800204
  • Synthesis and X-ray Crystal Structures of Homotrimetallic Zinc Bisureate Complexes
    Bayram, M. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie 644 (2018)
    Alkane elimination reactions of the tethered bis(urea) proligand 1,4-(tBuNHCONH)2-C4H8 (1) with ZnR2 (R = Me, Et, nPr) yielded trimetallic zinc complexes [RZn-1,4-(tBuNHCON)2-C4H8]2Zn [R = Me (2), Et (3), and nPr (4)]. 2–4 were characterized by heteronuclear NMR (1H, 13C) and IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/zaac.201700350
  • Synthesis and X-ray Crystal Structures of β-Ketoiminate Complexes
    Steiniger, P. and Dittrich, D. and Scheiper, C. and John, C. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie 644 (2018)
    Heteroleptic zinc complexes containing side-arm donor-functionalized tridentate β-ketoiminate ligands were obtained from metalation reactions of β-ketoimines L1/2/3Do1/2/3/4H [L1 = {(OC(Me)C(H)C(Me)NCH2CH2Do)}, L2 = {(OC(Me)C(H)C(Me)NCH2CH2CH2Do)}, L3 = {(OC(OMe)C(H)C(Me)NCH2CH2Do)}; Do1 = NMe2, Do2 = NEt2; Do3 = Pyr, Do4 = OMe] with equimolar amounts of Zn[N(SiMe3)2]2 [L1Do1ZnN(SiMe3)2 (1), L1Do2ZnN(SiMe3)2 (2)] and ZnEt2 [L1Do3ZnEt (3), L2Do3ZnEt (4), L3Do1ZnEt (5), L3Do4ZnEt (6)]. Analogous reactions of AlMe3 and Cp*MMe3 with L1Do1/2H yielded homoleptic aluminum [L1Do1AlMe2 (7), L1Do2AlMe2 (8), L2Do1AlMe2 (9)], titanium [L1Do2Ti(Me2)Cp* (10)] and zirconium complexes [L1Do2Zr(Me2)Cp* (11)]. In addition, 7 reacts with an ethereal HCl solution with methane elimination and formation of L1Do1Al(Cl)Me (12) and L1Do1AlCl2 (13), whereas the reaction with one and two equivalents of 2,6-dimethylphenol yielded L1Do1Al(Me)O-2,6-Me2C6H3 (14) and L1Do1Al(O-2,6-Me2C6H3)2 (15). The complexes were characterized by elemental analysis, 1H, 13C NMR, and IR spectroscopy and single-crystal X-ray analysis (2, 4, 7, 10, 12–14). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/zaac.201800321
  • Synthesis of a gallaarsene {HC[C(Me)N-2,6- i -Pr2-C6H3]2}GaAsCp∗ Containing a Ga=As double bond
    Helling, C. and Wölper, C. and Schulz, S.
    Journal of the American Chemical Society 140 (2018)
    Cp∗AsCl2 (Cp∗ = C5Me5) reacts with one equivalent of LGa (L = HC[C(Me)N(2,6-i-Pr2C6H3)]2) with formation of L(Cl)GaAs(Cl)Cp∗ 1, whereas the reaction with two equivalents of LGa yielded gallaarsene LGaAsCp∗ 2 containing a Ga=As double bond and (η1-Ga(Cp∗)L(η2-GaL)(μ-As3) 3. Compounds 2 and 3 were structurally characterized by single crystal X-ray diffraction, and the π-bonding contribution in 2 was analyzed by temperature-dependent 1H NMR spectroscopy (9.65 kcal mol-1) and by quantum mechanical computation. © 2018 American Chemical Society.
    view abstract10.1021/jacs.8b02447
  • Synthesis, Structures, and Catalytic Activity of Homo- and Heteroleptic Ketoiminate Zinc Complexes in Lactide Polymerization
    Steiniger, P. and Schäfer, P.M. and Wölper, C. and Henkel, J. and Ksiazkiewicz, A.N. and Pich, A. and Herres-Pawlis, S. and Schulz, S.
    European Journal of Inorganic Chemistry 2018 (2018)
    The heteroleptic complex LZnEt [(1); L = MeNacac = MeNC(Me)CHC(Me)O] containing the sterically less demanding N,O-chelating ketoiminate (MeNacac) ligand was synthesized by reaction of ZnEt2 with an equimolar amount of MeNacacH, whereas the reaction with two equivalents MeNacacH gave the homoleptic complex L2Zn 5. 1 reacts with ArOH (Ar = 2,6-Me2-Ph) with ethane elimination and formation of LZnOAr (2). Addition of the Lewis base dmap (dmap = 4-dimethylamino pyridine) to 1 and 2 yielded the corresponding Lewis acid-base adducts dmap-Zn(L)Et 3 and dmap-Zn(L)OAr 4. Compounds 1–5 were characterized by heteronuclear NMR (1H, 13C) and IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction (1–3, 5). Their technical application as catalysts in ring-opening polymerization (ROP) of rac-lactide in CD2Cl2 or CDCl3 solutions at ambient temperature was investigated. 2 and 3 show the highest activities, whereas those of 1 and 5 are substantially lower. 2 and 3 polymerize rac-lactide (90 % conversion) within 140 (3) and 180 (2) minutes, respectively. In contrast, 4 could only be investigated in bulk polymerization reactions due to its very poor solubility in common organic solvents. These studies proved that 4 is active in bulk polymerization, converting 93 % lactide to polylactide at 140 °C within 20 minutes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/ejic.201800504
  • The Role of Composition of Uniform and Highly Dispersed Cobalt Vanadium Iron Spinel Nanocrystals for Oxygen Electrocatalysis
    Chakrapani, K. and Bendt, G. and Hajiyani, H. and Lunkenbein, T. and Greiner, M.T. and Masliuk, L. and Salamon, S. and Landers, J. and Schlögl, R. and Wende, H. and Pentcheva, R. and Schulz, S. and Behrens, M.
    ACS Catalysis 8 (2018)
    Cation substitution in transition-metal oxides is an important approach to improve electrocatalysts by the optimization of their composition. Herein, we report on phase-pure spinel-type CoV2-xFexO4 nanoparticles with 0 ≤ x ≤ 2 as a new class of bifunctional catalysts for the oxygen evolution (OER) and oxygen reduction reactions (ORR). The mixed-metal oxide catalysts exhibit high catalytic activity for both OER and ORR that strongly depends on the V and Fe content. CoV2O4 is known to exhibit a high conductivity, while in CoFe2O4 the cobalt cation distribution is expected to change due to the inversion of the spinel structure. The optimized catalyst, CoV1.5Fe0.5O4, shows an overpotential for the OER of â300 mV for 10 mA cm-2 with a Tafel slope of 38 mV dec-1 in alkaline electrolyte. DFT+U+SOC calculations on cation ordering confirm the tendency toward the inverse spinel structure with increasing Fe concentration in CoV2-xFexO4 that starts to dominate already at low Fe contents. The theoretical results also show that the variations of oxidation states are related to the surface region, where the redox activity was found experimentally to be manifested in the transformation of V3+ ↠V2+. The high catalytic activity, facile synthesis, and low cost of the CoV2-xFexO4 nanoparticles render them very promising for application in bifunctional electrocatalysis. © 2017 American Chemical Society.
    view abstract10.1021/acscatal.7b03529
  • Adjusting the catalytic properties of cobalt ferrite nanoparticles by pulsed laser fragmentation in water with defined energy dose
    Waag, F. and Gökce, B. and Kalapu, C. and Bendt, G. and Salamon, S. and Landers, J. and Hagemann, U. and Heidelmann, M. and Schulz, S. and Wende, H. and Hartmann, N. and Behrens, M. and Barcikowski, S.
    Scientific Reports 7 (2017)
    Highly active, structurally disordered CoFe2O4/CoO electrocatalysts are synthesized by pulsed laser fragmentation in liquid (PLFL) of a commercial CoFe2O4 powder dispersed in water. A partial transformation of the CoFe2O4 educt to CoO is observed and proposed to be a thermal decomposition process induced by the picosecond pulsed laser irradiation. The overpotential in the OER in aqueous alkaline media at 10 mA cm-2 is reduced by 23% compared to the educt down to 0.32 V with a Tafel slope of 71 mV dec-1. Importantly, the catalytic activity is systematically adjustable by the number of PLFL treatment cycles. The occurrence of thermal melting and decomposition during one PLFL cycle is verified by modelling the laser beam energy distribution within the irradiated colloid volume and comparing the by single particles absorbed part to threshold energies. Thermal decomposition leads to a massive reduction in particle size and crystal transformations towards crystalline CoO and amorphous CoFe2O4. Subsequently, thermal melting forms multi-phase spherical and network-like particles. Additionally, Fe-based layered double hydroxides at higher process cycle repetitions emerge as a byproduct. The results show that PLFL is a promising method that allows modification of the structural order in oxides and thus access to catalytically interesting materials. © 2017 The Author(s).
    view abstract10.1038/s41598-017-13333-zf
  • Bismuth amides as promising ALD precursors for Bi2Te3 films
    Rusek, M. and Komossa, T. and Bendt, G. and Schulz, S.
    Journal of Crystal Growth 470 (2017)
    The thermal properties of five homoleptic bismuth amides of the general type (R1R2N)3Bi (R1, R2 = Me 1, R1, R2 = Et 2, R1, R2 = n-Pr 3, R1 = Me, R2 = Et 4, R1 = n-Bu, R2 = Et 5) and the cyclo-dibismadiazane [(Me3Si)2NBi-μ-NSiMe3]2 6 were studied by DSC and TGA/DTA (1, 6) and their reactions with (Et3Si)2Te were investigated by in situ NMR spectroscopy. Based on these results, the potential application of 1, 4 and 6 to serve as ALD precursors for the deposition of Bi2Te3 films in reactions with (Et3Si)2Te were investigated. The resulting films were characterized by XRD, EDX, AFM and SEM and the crucial role of the substrate material and substrate temperature on the film growth rate and the morphology and chemical composition of the Bi2Te3 films was determined. © 2017
    view abstract10.1016/j.jcrysgro.2017.04.019
  • Detecting inconsistencies in large first-order knowledge bases
    Schulz, S. and Sutcliffe, G. and Urban, J. and Pease, A.
    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 10395 LNAI (2017)
    Large formalizations carry the risk of inconsistency, and hence may lead to instances of spurious reasoning. This paper describes a new approach and tool that automatically probes large first-order axiomatizations for inconsistency, by selecting subsets of the axioms centered on certain function and predicate symbols, and handling the subsets to a first-order theorem prover to test for unsatisfiability. The tool has been applied to several large axiomatizations, inconsistencies have been found, inconsistent cores extracted, and semi-automatic analysis of the inconsistent cores has helped to pinpoint the axioms that appear to be the underlying cause of inconsistency. © Springer International Publishing AG 2017.
    view abstract10.1007/978-3-319-63046-5_19
  • Dilute suspensions in annular shear flow under gravity: Simulation and experiment
    Schröer, K. and Kurzeja, P. and Schulz, S. and Brockmann, P. and Hussong, J. and Janas, P. and Wlokas, I. and Kempf, A. and Wolf, D.E.
    EPJ Web of Conferences 140 (2017)
    A dilute suspension in annular shear flow under gravity was simulated using multi-particle collision dynamics (MPC) and compared to experimental data. The focus of the analysis is the local particle velocity and density distribution under the influence of the rotational and gravitational forces. The results are further supported by a deterministic approximation of a single-particle trajectory and OpenFOAM CFD estimations of the overcritical frequency range. Good qualitative agreement is observed for single-particle trajectories between the statistical mean of MPC simulations and the deterministic approximation. Wall contact and detachment however occur earlier in the MPC simulation, which can be explained by the inherent thermal noise of the method. The multi-particle system is investigated at the point of highest particle accumulation that is found at 2/3 of the particle revolution, starting from the top of the annular gap. The combination of shear flow and a slowly rotating volumetric force leads to strong local accumulation in this section that increases the particle volume fraction from overall 0.7% to 4.7% at the outer boundary. MPC simulations and experimental observations agree well in terms of particle distribution and a close to linear velocity profile in radial direction. © The Authors, published by EDP Sciences, 2017.
    view abstract10.1051/epjconf/201714009034
  • Imidazolium Based Ionic Liquids: Impact of the Cation Symmetry and Alkyl Chain Length on the Enthalpy of Vaporization
    Yermalayeu, A.V. and Zaitsau, D.H. and Loor, M. and Schaumann, J. and Emel'yanenko, V.N. and Schulz, S. and Verevkin, S.P.
    Zeitschrift fur Anorganische und Allgemeine Chemie 643 (2017)
    The vaporization thermodynamics of symmetric imidazolium based ionic liquids of the general formula [CnCnIm][Br] with the chains length n = 4, 5, 6, and 8 were investigated using a combination of DSC, TGA, and QCM methods with quantum chemical calculations. Comparison of vaporization enthalpies for the symmetric ([CnCnIm][Br]) and asymmetric imidazolium based ILs ([Cnmim][Br]) revealed a general trend with the lower vaporization enthalpies of the symmetric species indicating a significant decrease of the Coulombic interactions affecting energetics of vaporization. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/zaac.201600332
  • Improving the zT value of thermoelectrics by nanostructuring: tuning the nanoparticle morphology of Sb2Te3 by using ionic liquids
    Schaumann, J. and Loor, M. and Ünal, D. and Mudring, A. and Heimann, S. and Hagemann, U. and Schulz, S. and Maculewicz, F. and Schierning, G.
    Dalton Transactions 46 (2017)
    A systematic study on the microwave-assisted thermolysis of the single source precursor (Et2Sb)2Te (1) in different asymmetric 1-alkyl-3-methylimidazolium- and symmetric 1,3-dialkylimidazolium-based ionic liquids (ILs) reveals the distinctive role of both the anion and the cation in tuning the morphology and microstructure of the resulting Sb2Te3 nanoparticles as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). A comparison of the electrical and thermal conductivities as well as the Seebeck coefficient of the Sb2Te3 nanoparticles obtained from different ILs reveals the strong influence of the specific IL, from which C4mimI was identified as the best solvent, on the thermoelectric properties of as-prepared nanosized Sb2Te3. This work provides design guidelines for ILs, which allow the synthesis of nanostructured thermoelectrics with improved performances. © The Royal Society of Chemistry.
    view abstract10.1039/c6dt04323b
  • Intramolecularly-stabilized Group 14 Alkoxides - Promising Precursors for the Synthesis of Group 14-Chalcogenides by Hot-Injection Method
    Rusek, M. and Bendt, G. and Wölper, C. and Bläser, D. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie (2017)
    Intramolecularly-stabilized germanium, tin, and lead alkoxides of the type M(OCH2CH2NR2)2 [R = Et, M = Ge (1); R = Me, M = Sn (2); R = Me, M = Pb (3)] are suitable precursors for the synthesis of group 14 chalcogenides ME (M = Ge, Sn, Pb; E = S, Se, Te) in scrambling reactions with (Me3Si)2S and (Et3Si)2E (E = Se, Te) at moderate temperatures via hot injection method. The reactions proceed with elimination of the corresponding silylether as was proven by in situ 1H NMR spectroscopy. The solid-state structures of the homoleptic complex 1 and the heteroleptic complex ClGe(OC2H4NEt2) (4) were determined by single-crystal X-ray diffraction, whereas the group 14 chalcogenides were characterized by XRD, SEM, and EDX. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/zaac.201700029
  • Preparation, catalytical activity and crystal structure of a heptanuclear zinc acetate cluster
    Dittrich, D. and Tewes, H. and Wölper, C. and Bläser, D. and Schulz, S. and Roll, J.
    Transition Metal Chemistry 42 (2017)
    Reaction of [Zn4(µ4-O)(O2CCH3)6] with one equivalent of 4-tertiary-butylpyridine leads to a nearly quantitative formation of the heptanuclear cluster [Zn7O2(O2CCH3)10(tbupy)2] (1). Here, we present the crystal structure of 1 and first results of the examination of its catalytic activity in transesterification reactions and polymerization of lactide compared to the activity of [Zn4(µ4-O)(O2CCH3)6] in the presence of 4-tertiary-butylpyridine. © 2017, Springer International Publishing Switzerland.
    view abstract10.1007/s11243-017-0127-y
  • Reduction of [Cp*Sb]4 with Subvalent Main-Group Metal Reductants: Syntheses and Structures of [(L1Mg)4(Sb4)] and [(L2Ga)2(Sb4)] Containing Edge-Missing Sb4 Units
    Ganesamoorthy, C. and Krüger, J. and Wölper, C. and Nizovtsev, A.S. and Schulz, S.
    Chemistry - A European Journal 23 (2017)
    [Cp*Sb]4 (Cp*=C5Me5) reacts with [L1Mg]2 and L2Ga with formation of [(L1Mg)4(μ4,η1:2:2:2-Sb4)] (L1=iPr2NC[N(2,6-iPr2C6H3)]2, 1) and [(L2Ga)2(μ,η2:2-Sb4)] (L2=HC[C(Me)N(2,6-iPr2C6H3)]2, 2). The cleavage of the Sb−Sb and Sb−C bonds in [Cp*Sb]4 are the crucial steps in both reactions. The formation of 1 occurred by elimination of the Cp* anion and formation of Cp*MgL1, while 2 was formed by reductive elimination of Cp*2 and oxidative addition of L2Ga to the Sb4 unit. 1 and 2 were characterized by heteronuclear NMR spectroscopy and single-crystal X-ray diffraction, and their bonding situation was studied by quantum chemical calculations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/chem.201605547
  • Retention of the Zn−Zn bond in [Ge9Zn−ZnGe9]6− and Formation of [(Ge9Zn)−(Ge9)−(ZnGe9)]8− and Polymeric 1∞ [−(Ge9Zn)2−−]1
    Mayer, K. and Jantke, L.-A. and Schulz, S. and Fässler, T.F.
    Angewandte Chemie - International Edition 56 (2017)
    Reactions of ZnI 2L2 (where L=[HC(PPh2NPh)]−) with solutions of the Zintl phase K4Ge9 in liquid ammonia lead to retention of the Zn−Zn bond and formation of the anion [(η4-Ge9)Zn−Zn(η4-Ge9)]6−, representing the first complex with a Zn−Zn unit carrying two cluster entities. The trimeric anion [(η4-Ge9)Zn{μ2(η1:η1Ge9)}Zn(η4-Ge9)]8− forms as a side product, indicating that oxidation reactions also take place. The reaction of Zn2Cp*2 (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with K4Ge9 in ethylenediamine yielded the linear polymeric unit (Formula presented.) {[Zn[μ2(η4:η1Ge9)]}2− with the first head-to-tail arrangement of ten-atom closo-clusters. All anions were obtained and structurally characterized as [A(2.2.2-crypt)]+ salts (A=K, Rb). Copious computational analyses at a DFT-PBE0/def2-TZVPP/PCM level of theory confirm the experimental structures and support the stability of the two hypothetical ten vertex cluster fragments closo-[Ge9Zn]2− and (paramagnetic) [Ge9Zn]3−. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/anie.201610831
  • Retention of the Zn−Zn bond in [Ge9Zn−ZnGe9]6−and Formation of [(Ge9Zn)−(Ge9)−(ZnGe9)]8−and Polymeric 1∞ [−(Ge9Zn)2−−]1
    Mayer, K. and Jantke, L.-A. and Schulz, S. and Fässler, T.F.
    Angewandte Chemie - International Edition 56 (2017)
    Reactions of ZnI2L2(where L=[HC(PPh2NPh)]−) with solutions of the Zintl phase K4Ge9in liquid ammonia lead to retention of the Zn−Zn bond and formation of the anion [(η4-Ge9)Zn−Zn(η4-Ge9)]6−, representing the first complex with a Zn−Zn unit carrying two cluster entities. The trimeric anion [(η4-Ge9)Zn{μ2(η1:η1Ge9)}Zn(η4-Ge9)]8−forms as a side product, indicating that oxidation reactions also take place. The reaction of Zn2Cp*2(Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with K4Ge9in ethylenediamine yielded the linear polymeric unit (Formula presented.) {[Zn[μ2(η4:η1Ge9)]}2−with the first head-to-tail arrangement of ten-atom closo-clusters. All anions were obtained and structurally characterized as [A(2.2.2-crypt)]+salts (A=K, Rb). Copious computational analyses at a DFT-PBE0/def2-TZVPP/PCM level of theory confirm the experimental structures and support the stability of the two hypothetical ten vertex cluster fragments closo-[Ge9Zn]2−and (paramagnetic) [Ge9Zn]3−. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/anie.201610831
  • Role of Composition and Size of Cobalt Ferrite Nanocrystals in the Oxygen Evolution Reaction
    Chakrapani, K. and Bendt, G. and Hajiyani, H. and Schwarzrock, I. and Lunkenbein, T. and Salamon, S. and Landers, J. and Wende, H. and Schlögl, R. and Pentcheva, R. and Behrens, M. and Schulz, S.
    ChemCatChem 9 (2017)
    Sub-10 nm CoFe2O4 nanoparticles with different sizes and various compositions obtained by (partial) substitution of Co with Ni cations have been synthesized by using a one-pot method from organic solutions by the decomposition of metal acetylacetonates in the presence of oleylamine. The electrocatalytic activity of CoFe2O4 towards the oxygen evolution reaction (OER) is clearly enhanced with a smaller size (3.1 nm) of the CoFe2O4 nanoparticles (compared with 4.5 and 5.9 nm). In addition, the catalytic activity is improved by partial substitution of Co with Ni, which also leads to a higher degree of inversion of the spinel structure. Theoretical calculations attribute the positive catalytic effect of Ni owing to the lower binding energy differences between adsorbed O and OH compared with pure cobalt or nickel ferrites, resulting in higher OER activity. Co0.5Ni0.5Fe2O4 exhibited a low overpotential of approximately 340 mV at 10 mA cm−2, a smaller Tafel slope of 51 mV dec−1, and stability over 30 h. The unique tunability of these CoFe2O4 nanocrystals provides great potential for their application as an efficient and competitive anode material in the field of electrochemical water splitting as well as for systematic fundamental studies aiming at understanding the correlation of composition and structure with performance in electrocatalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/cctc.201700376
  • Syntheses and Structures of Homo- and Heteroleptic Beryllium Complexes Containing N,N'-Chelating Ligands
    Bayram, M. and Naglav, D. and Wölper, C. and Schulz, S.
    Organometallics 36 (2017)
    Reactions of BeEt2 with S(NSiMe3)2 and carbodiimides RNCNR yielded homoleptic bisdiimidosulfinate [EtS(NSiMe3)2]2Be (1) and amidinate complexes [EtC(NAr)2]2Be (Ar = 2,6-i-Pr2-C6H3 2, SiMe3 3). In addition, the heteroleptic amidinate [t-BuC(NAr)2]BeEt (4) and β-diketiminate [HC(CMeNAr')2]Be(i-Bu) (6) (Ar' = 2,4,6-Me3C6H2) complexes were obtained by alkane elimination reactions of BeEt2 with t-BuC(NSiMe3)N(H)SiMe3 and Be(i-Bu)2 with β-diketimine [Ar'N(H)C(Me)CHC(Me)NAr'], respectively. In addition, 4 was found to react with dry oxygen with formation of the corresponding alkoxide [t-BuC(NAr)2]BeOEt (5). 1-6 were characterized by multinuclear NMR (1H, 9Be, 13C) and IR spectroscopy as well as by single-crystal X-ray diffraction (1, 2, 4, 5, 6). © 2017 American Chemical Society.
    view abstract10.1021/acs.organomet.6b00865
  • Syntheses and structures of N,C,N-stabilized antimony chalcogenides
    Ganesamoorthy, C. and Wölper, C. and Dostál, L. and Schulz, S.
    Journal of Organometallic Chemistry 845 (2017)
    The oxidation reactions of ArSb [Ar = 2,6-(HC=N-t-Bu)2C6H3] with S8, grey Se and Te as well as E2Ph2 (E = S, Se, Te) are demonstrated. The reactions of ArSb with elemental sulfur and selenium occurred at elevated temperatures and yielded ArSbE (E = S, 1; Se 2), whereas the reactions with E2Ph2 proceeded at room temperature with subsequent formation of the corresponding insertion complexes ArSb(EPh)2 (E = S 3; Se 4). In addition, ArSb(TePh)2 (5) was formed at very low temperature and showed a temperature-dependent reversible equilibrium with ArSb and Te2Ph2 between -80 °C and 20 °C. The formation and structure of compounds 1-4, which were isolated in good yields, are assigned through multinuclear NMR (1H, 13C, 77Se), IR spectroscopy and microanalyses data. In addition, the molecular structures of 2-4 are further confirmed by single crystal X-ray diffraction studies. © 2017.
    view abstract10.1016/j.jorganchem.2017.01.007
  • Synthesis of Sb2Se3and Bi2Se3Nanoparticles in Ionic Liquids at Low Temperatures and Solid State Structure of [C4C1Im]3[BiCl6]
    Loor, M. and Bendt, G. and Schaumann, J. and Hagemann, U. and Heidelmann, M. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie 643 (2017)
    Crystalline Sb2Se3nanoparticles were prepared by reaction of SbCl3with (Et3Si)2Se in the presence of oleylamine (OA) in the ionic liquid [C4C1Im]Cl, whereas the reaction of (Et3Si)2Se with [C4C1Im]3[BiCl6] (1), which was obtained from the reaction of BiCl3with [C4C1Im]Cl and structurally characterized by single-crystal X-ray diffraction, yielded Bi-rich Bi2Se3nanoparticles. In contrast, the reaction of the reactive IL [C4C1Im]3[Bi3I12] with (Et3Si)2Se in the presence of oleylamine in [C4C1Im]I gave phase-pure Bi2Se3nanoparticles. The chemical composition of the nanoparticles was investigated by EDX, while possible surface contaminations were studied by XPS and IR spectroscopy. The morphology of the nanoparticles was studied by SEM and TEM. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/zaac.201600325
  • Synthesis, Solid-State Structure, and Bonding Analysis of a Homoleptic Beryllium Azide
    Naglav, D. and Tobey, B. and Lyhs, B. and Römer, B. and Bläser, D. and Wölper, C. and Jansen, G. and Schulz, S.
    Angewandte Chemie - International Edition 56 (2017)
    [Ph4P]2[Be(N3)4] (1) and [PNP]2[Be(N3)4] (2; PNP=Ph3PNPPh3) were synthesized by reacting Be(N3)2 with [Ph4P]N3 and [PNP]N3. Compound 1 represents the first structurally characterized homoleptic beryllium azide. The electronic structure and bonding situation in the tetraazidoberyllate dianion [Be(N3)4]2− were investigated by quantum-chemical calculations (NPA, ELF, LOL). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/anie.201703147
  • Synthesis, solid-state structures and reduction reactions of heteroleptic Ge(II) and Sn(II) β-ketoiminate complexes
    Wiederkehr, J. and Wölper, C. and Schulz, S.
    Zeitschrift fur Naturforschung - Section B Journal of Chemical Sciences 72 (2017)
    A series of new heteroleptic divalent germaniun and tin complexes of the general type L1,4GeN(SiMe3)2 (1, 2) and L1-4SnN(SiMe3)2 (3-6) were synthesized by reaction of β-ketimines L1-4H with Ge[N(SiMe3)2]2 and Sn[N(SiMe3)2]2, respectively. The reaction of 3 with the strong Mg(I) reductant L5Mg yielded the heteroleptic complex L1MgL5 7 after ligand transfer from tin to magnesium, whereas analogous reactions of L4GeN(SiMe3)2 2 and L4SnN(SiMe3)2 6 with L5Mg occurred with formation of insoluble precipitates, transfer of the amido substituent from the group 14 metal to magnesium and subsequent formation of the heteroleptic magnesium complex L5MgN(SiMe3)2 (8). 1-8 were characterized by heteronuclear NMR (1H, 13C, 119Sn) and IR spectroscopy, elemental analysis and single-crystal X-ray diffraction (L4SnN(SiMe3)2 6, L1MgL5 7).
    view abstract10.1515/znb-2017-0098
  • Synthesis, structure and dispersion interactions in bis(1,8-naphthalendiyl)distibine
    Ganesamoorthy, C. and Heimann, S. and Hölscher, S. and Haack, R. and Wölper, C. and Jansen, G. and Schulz, S.
    Dalton Transactions 46 (2017)
    Naph2Sb21 was synthesized by a reaction of 1,8-dilithionaphthalene NaphLi2 with SbCl3 and its solid state structure is reported on. 1 shows intermolecular interactions in the solid state, which were studied by quantum chemical calculations with dispersion corrected density functional theory, supermolecular ab initio approaches and symmetry adapted perturbation theory. The same methods were employed to compare the solid state interactions in the crystal of 1 to those in real (for E = P) and hypothetical (for E = As and Bi) crystal structures of Naph2E2. Dispersion interactions were found to provide the most important stabilising contribution in all cases, seconded by electrostatic attraction between pnictogen atoms and π-systems of neighbouring naphthyl groups. © 2017 The Royal Society of Chemistry.
    view abstract10.1039/c7dt02165h
  • Synthesis, Structure, and Reactivity of Ga-Substituted Distibenes and Sb-Analogues of Bicyclo[1.1.0]butane
    Tuscher, L. and Helling, C. and Ganesamoorthy, C. and Krüger, J. and Wölper, C. and Frank, W. and Nizovtsev, A.S. and Schulz, S.
    Chemistry - A European Journal 23 (2017)
    Monovalent gallanediyl LGa {L=HC[C(Me)N(2,6-iPr2C6H3)]2} reacts with SbX3 to form the Ga-substituted distibenes [(LGaX)2Sb2] (X=NMeEt 1, Cl 2). Upon heating, 2 reacts to the bicyclo[1.1.0]butane analogue [(LGaCl)2(μ,η1:1-Sb4)] 3 containing a [Sb4]2− dianion. Moreover, 2 reacts with Li amides LiNR2 in salt elimination reactions that form the corresponding amido-substituted compounds 1 and [(LGaNMe2)2Sb2] 4, whereas reactions of 4 and [(LGaNMe2)2(μ,η1:1-Sb4)] 5 with two equivalents of GaCl3 resulted in the formation of 2 and 3, respectively. 1, 2 and 3 were characterized by 1H and 13C NMR spectroscopy, elemental analysis, and single crystal X-ray diffraction. In addition, their bonding situation was analyzed by quantum chemical calculations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/chem.201701248
  • (MeZn)2(μ-η2:η2-N6Ph2): A Powerful Starting Reagent for the Synthesis of Metal Hexazene Complexes
    Stienen, C. and Gondzik, S. and Gehlhaar, A. and Haack, R. and Wölper, C. and Jansen, G. and Schulz, S.
    Organometallics 35 (2016)
    [(MeLDippZn)2(μ-η2:η2-PhN6Ph)] (3), which was synthesized by reaction of MeLDipp 2Zn2 with PhN3, reacts with two equivalents of Me2Zn to give [(MeZn)2(μ-η2:η2-PhN6Ph)] (2). The reaction of 2 with pyridine gave [(MeZn)2(μ-η2:η2-PhN6Ph)(Py)2] (4), while reactions with H-acidic ligands (MeLMesH, MeLPhH) occurred with elimination of methane and formation of [(MeLMesZn)2(μ-η2:η2-PhN6Ph)] (1) and [(MeLPhZn)2(μ-η2:η2-PhN6Ph)] (5). The reaction of 1 with two equivalents of MeLi yielded the heterobimetallic hexazene complex [(MeZn)(μ-η2:η2-PhN6Ph)(Li)], which was found to undergo stepwise reaction with Me2AlCl to give [MeZn(μ-η2:η2-PhN6Ph)AlMe2] and finally [(Me2Al)2(μ-η2:η2-PhN6Ph)(thf)2] (6). Compounds 3-6 were characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction. Quantum chemical calculations were performed in order to investigate the electronic structure of 4′ and 6′ in more detail and to identify the absorption bands of the hexazene unit. © 2016 American Chemical Society.
    view abstract10.1021/acs.organomet.6b00116
  • Alternative Precursors for the Synthesis of Binary Sb2E3and Bi2E3(E = S, Se, Te) Nanoparticles by the Hot Injection Method
    Rusek, M. and Bendt, G. and Wölper, C. and Schulz, S.
    European Journal of Inorganic Chemistry 2016 (2016)
    Intramolecularly stabilized Sb(OCH2CH2NMe2)3(1) and Bi(OCH2CH2NMe2)3(2) readily react with (Me3Si)2S and (Et3Si)2E (E = Se, Te) at moderate temperatures (hot injection method) with elimination of the corresponding silyl ether and subsequent formation of the group 15 chalcogenides Sb2E3and Bi2E3, which were characterized by XRD, SEM, and energy-dispersive X-ray spectroscopy (EDX). In addition, the solid-state structure of 1 was determined by single-crystal XRD. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/ejic.201600490
  • Lewis acid-base adducts of group 13 elements: Synthesis, structure and reactivity toward benzaldehyde
    Ganesamoorthy, C. and Matthias, M. and Bläser, D. and Wölper, C. and Schulz, S.
    Dalton Transactions 45 (2016)
    Lewis acid-base adducts [LGa-M(C6F5)3] (M = B 1, Al 2, Ga 3) were prepared by the reaction of gallanediyl LGa {L = HC[C(Me)N(2,6-i-Pr2C6H3)]2} with the Lewis acids M(C6F5)3 (M = B, Al, Ga). Benzaldehyde reacts with [LGa-M(C6F5)3] (M = B 1, Al 2) at room temperature with the insertion and formation of [LGa(C6F5){CH(Ph)(OB(C6F5)2)}] (4) and the zwitterionic species [LGa(C6F5){CH(Ph)(OAl(C6F5)2)}] (5), respectively, which was found to decompose at 80 °C with the formation of {(C6F5)2Al(OCH2Ph)}2 (6). Any attempts to isolate the insertion complex of [LGa-Ga(C6F5)3] with benzaldehyde failed and only {(C6F5)2Ga(OCH2Ph)}2 (7) was isolated at elevated temperatures. 2-5 and 7 were structurally characterized by heteronuclear NMR spectroscopy and single crystal X-ray diffraction. © The Royal Society of Chemistry 2016.
    view abstract10.1039/c6dt01688j
  • Molecular Design for Tailoring a Single-Source Precursor for Bismuth Ferrite
    Bendt, G. and Schiwon, R. and Salamon, S. and Landers, J. and Hagemann, U. and Limberg, C. and Wende, H. and Schulz, S.
    Inorganic Chemistry 55 (2016)
    Nearly phase-pure bismuth ferrite particles were formed by thermolysis of the single-source precursor [Cp(CO)2FeBi(OAc)2] (1) in octadecene at 245 °C, followed by subsequent calcination at 600 °C for 3 h. In contrast, the slightly modified compound [Cp(CO)2FeBi(O2CtBu)2] (2) yielded only mixtures of different bismuth oxide phases, revealing the distinctive influence of molecular design in material synthesis. The chemical composition, morphology, and crystallinity of the resulting materials were investigated by X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. In addition, the optical properties were investigated by Fourier transform infrared and UV-vis spectroscopies, showing a strong band gap absorption in the visible range at 590 nm (2.2 eV). The magnetic behavior was probed by vibrating-sample and superconducting quantum interference device magnetometry, as well as 57Fe Mössbauer spectroscopy. © 2016 American Chemical Society.
    view abstract10.1021/acs.inorgchem.6b00951
  • Off the Beaten Track—A Hitchhiker's Guide to Beryllium Chemistry
    Naglav, D. and Buchner, M.R. and Bendt, G. and Kraus, F. and Schulz, S.
    Angewandte Chemie - International Edition 55 (2016)
    This Minireview aims to give an introduction to beryllium chemistry for all less-experienced scientists in this field of research. Up to date information on the toxicity of beryllium and its compounds are reviewed and several basic and necessary guidelines for a safe and proper handling in modern chemical research laboratories are presented. Interesting phenomenological observations are described that are related directly to the uniqueness of this element, which are also put into historical context. Herein we combine the contributions and experiences of many scientist that work passionately in this field. We want to encourage fellow scientists to reconcile the long-standing reservations about beryllium and its compounds and motivate intense research on this spurned element. Who on earth should be able to deal with beryllium and its compounds if not chemists?. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/anie.201601809
  • On the Stability of Trimeric Beryllium Hydroxide Scorpionate Complexes
    Naglav, D. and Tobey, B. and Wölper, C. and Bläser, D. and Jansen, G. and Schulz, S.
    European Journal of Inorganic Chemistry 2016 (2016)
    The controlled hydrolysis of TpBeCl {Tp = trispyrazolylborate [HB(C3N2H3)3]–} with H2O and D2O in the presence of N,N-diisopropylethylamine (DIPEA) yields the trimeric beryllium hydroxide scorpionate complexes [Be3(µ-OX)3(Tp)3] (X = H: 1, D: 2) quantitatively. The complexes contain six-membered Be3O3 rings according to single-crystal X-ray diffraction studies and theoretical calculations. Temperature-dependent 1H and 9Be NMR spectroscopy established that 1 has a dynamic structure in solution. In addition, the structure of [Be3(µ-OH)3(Br)3(thf)6], which was obtained from hydrolysis of a solution of BeBr2 in tetrahydrofuran and CHCl3, is reported. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/ejic.201501433
  • Organosilane modified Zr-based conversion layer on Zn–Al alloy coated steel sheets
    Lostak, T. and Timma, C. and Krebs, S. and Flock, J. and Schulz, S.
    Surface and Coatings Technology 305 (2016)
    Conversion layers based on amorphous Zirconium oxide are still in focus to replace state-of-the-art pre-treatment technologies like chromate- and phosphate-based inorganic protection coatings in different industrial sectors. Besides exceeding corrosion protection properties these layers offer sufficient adhesion behaviours. To investigate the influence of organofunctional silanes on the protection properties of these pre-treatment systems, 3-gylcidoxypropyltrimethoxysilane (γ-GPS) was added to the aqueous model conversion solution containing well-defined amounts of hexafluorozirconic acid (H2ZrF6). The surface composition of these modified conversion layers was determined using X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (FT-IRRAS) and confocal Raman microscopy (CRM). Scanning Kelvin Probe (SKP) measurements were obtained on organic coated samples in order to investigate the corrosive cathodic delamination process in more detail. © 2016 Elsevier B.V.
    view abstract10.1016/j.surfcoat.2016.08.030
  • Simultaneous synthesis of nanodiamonds and graphene via plasma enhanced chemical vapor deposition (MW PE-CVD) on copper
    Gottlieb, S. and Wöhrl, N. and Schulz, S. and Buck, V.
    SpringerPlus 5 (2016)
    The simultaneous growth of both nanodiamonds and graphene on copper samples is described for the first time. A PE-CVD process is used to synthesize graphene layers and nanodiamond clusters from a hydrogen/methane gas mixture as it is typically done successfully in thermal CVD processes for graphene synthesis. However, the standard thermal CVD process is not without problems since the deposition of graphene is affected by the evaporation of a notable amount of copper caused by the slow temperature increase typical for thermal CVD resulting in a long process time. In sharp contrast, the synthesis of graphene by PE-CVD can circumvent this problem by substantially shortening the process time at holding out the prospect of a lower substrate temperature. The reduced thermal load and the possibility to industrially scale-up the PE-CVD process makes it a very attractive alternative to the thermal CVD process with respect to the graphene production in the future. Nanodiamonds are synthesized in PE-CVD reactors for a long time because these processes offer a high degree of control over the film’s nanostructure and simultaneously providing a significant high deposition rate. To model the co-deposition process, the three relevant macroscopic parameters (pressure, gas mixture and microwave power) are correlated with three relevant process properties (plasma ball size, substrate temperature and C2/Hα-ratio) and the influence on the quality of the deposited carbon allotropes is investigated. For the evaluation of the graphene as well as the nanodiamond quality, Raman spectroscopy used whereas the plasma properties are measured by optical methods. It is found that the diamond nucleation can be influenced by the C2/Hα-ratio in the plasma, while the graphene quality remains mostly unchanged by this parameter. Moreover it is derived from the experimental data that the direct plasma contact with the copper surface is beneficial for the nucleation of the diamond while the growth and quality of the graphene benefits from a larger distance to the plasma. Therefore, this work presents a basis for a method to tailor the deposition of graphene–diamond hybrid films using a MW PE-CVD process or to suppress the diamond deposition entirely if desired. © 2016, The Author(s).
    view abstract10.1186/s40064-016-2201-x
  • Syntheses and Structures of Zinc Bis(phosphinimino)methanide Complexes
    Bayram, M. and Gondzik, S. and Bläser, D. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie 642 (2016)
    Reactions of bis(phosphinimino)methanes H2C(PPh2NR)2 [R = SiMe3 (L1H), Ph (L2H), 2,6-iPr2-C6H3 (DIPP) (L3H)] with ZnR2 (R = Me, Et) yielded the corresponding bis(phosphinimino)methanide zinc complexes LZnMe [L2 (1), L3 (2)] and LZnEt [L1 (3), L2 (4), and L3 (5)]. Complexes 1–5 were characterized by heteronuclear NMR (1H, 13C, 31P) and IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/zaac.201600196
  • Synthesis and solid state structure of a metalloid tin cluster [Sn10(trip8)]
    Wiederkehr, J. and Wölper, C. and Schulz, S.
    Chemical Communications 52 (2016)
    (trip2Sn)2 (trip = 2,4,6-i-Pr3C6H2) reacts with Mg(i) reductants (LMg)2 (L = HC[C(Me)N(dipp)]2) and (L′Mg)2 (L′ = HC[C(Me)N(mes)]2) with Sn-C bond cleavage and formation of the novel metalloid tin cluster Sn10trip8 1 or elemental tin. 1, which contains Sn atoms in the formal oxidation states 0, +I and +II, and the side products LMgtrip (2) and L′Mgtrip (3) were characterized spectroscopically and by single crystal X-ray diffraction. © 2016 The Royal Society of Chemistry.
    view abstract10.1039/c6cc06770k
  • Synthesis and Structural Characterization of Magnesium-Substituted Polystibides [(LMg)4Sb8]
    Ganesamoorthy, C. and Wölper, C. and Nizovtsev, A.S. and Schulz, S.
    Angewandte Chemie - International Edition 55 (2016)
    Redox reactions of [(L1,2Mg)2] and Sb2R4 (R=Me, Et) yielded the first Mg-substituted realgar-type Sb8 polystibides [(L1,2Mg)4(μ4,η2:2:2:2-Sb8)] (L1=HC[C(Me)N(2,4,6-Me3C6H2)]2, L2=HC[C(Me)N(2,6-i-Pr2C6H3)]2). Compounds [(L1,2Mg)2] serve both as reducing agents, initiating the cleavage of the Sb-C bonds, and as stabilizers for the resulting Sb8 polyanion. The polystibides were characterized by NMR and IR spectroscopies, elemental analysis, and X-ray structure analysis. In addition, results from quantum chemical calculations are presented. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/anie.201510504
  • Synthesis and Structure of Bis(diphenylphosphinimino)methanide and Bis(diphenylphosphinimino)methanediide Beryllium Complexes
    Bayram, M. and Naglav, D. and Wölper, C. and Schulz, S.
    Organometallics 35 (2016)
    Reactions of BeEt2 with bis(diphenylphosphinimino)methanes H2C[PPh2NR]2 yielded the first bis(diphenylphosphinimino)methanide and bis(diphenylphosphinimino)methanediide beryllium complexes [CH(PPh2N-2,6-i-Pr2C6H3)2]BeEt (1), [C(PPh2NSiMe3)2](BeEt)2 (2), and [C(PPh2NPh)2](BeEt)2 (3), respectively. 1-3 were characterized by multinuclear NMR and IR spectroscopy as well as single-crystal X-ray diffraction. © 2016 American Chemical Society.
    view abstract10.1021/acs.organomet.6b00380
  • Synthesis of Bi2Te3 and (Bi: XSb1- x)2Te3 nanoparticles using the novel IL [C4mim]3[Bi3I12]
    Loor, M. and Bendt, G. and Hagemann, U. and Wölper, C. and Assenmacher, W. and Schulz, S.
    Dalton Transactions 45 (2016)
    The novel Bi-containing reactive ionic liquid [C4mim]3[Bi3I12], which was synthesized in quantitative yield by equimolar reaction of BiI3 and [C4mim]I, was used as a novel Bi-source for the ionothermal synthesis of Bi2Te3 nanoparticles by reaction with (Et3Si)2Te in the ionic liquid [C4mim]I. The solid state structure of [C4mim]3[Bi3I12] was determined by single crystal X-ray diffraction. In addition, the ionothermal synthesis of the single source precursor (Et2Sb)2Te and [C4mim]3[Bi3I12] yielded the ternary (BixSb1-x)2Te3 (x = 0.25, 0.5, 0.75) nanoparticles. The chemical composition and phase purity of the tetradymite-type materials were determined by EDX and XRD and the surface composition of the nanoparticles was further investigated by IR and XPS. In addition, the morphology of the nanoparticles was investigated by SEM and TEM. © 2016 The Royal Society of Chemistry.
    view abstract10.1039/c6dt02361d
  • A Gallium-Substituted Distibene and an Antimony-Analogue Bicyclo[1.1.0]butane: Synthesis and Solid-State Structures
    Tuscher, L. and Ganesamoorthy, C. and Bläser, D. and Wölper, C. and Schulz, S.
    Angewandte Chemie - International Edition 54 (2015)
    RGa {R=HC[C(Me)N(2,6-iPr<inf>2</inf>C<inf>6</inf>H<inf>3</inf>)]<inf>2</inf>} reacts with Sb(NMe<inf>2</inf>)<inf>3</inf> with insertion into the SbN bond and elimination of RGa(NMe<inf>2</inf>)<inf>2</inf> (2), yielding the Ga-substituted distibene R(Me<inf>2</inf>N)GaSbSbGa(NMe<inf>2</inf>)R (1). Thermolysis of 1 proceeded with elimination of RGa and 2 and subsequent formation of the bicyclo[1.1.0]butane analogue [R(Me<inf>2</inf>N)Ga]<inf>2</inf>Sb<inf>4</inf> (3). Getting GaGa about antimony: Comparative studies on the reaction of RGa with EX<inf>3</inf> (E=Sb, Bi; X=Et, NMe<inf>2</inf>) show the subtle influence of the organic substituents on the reactivity of the Group 15 compound and on the stability of the insertion product R(X)GaEX<inf>2</inf>. The use of Sb(NMe<inf>2</inf>)<inf>3</inf>, containing rather weak SbN bonds, resulted in the formation of a distibine, which was thermally converted into the first Sb analogue of bicyclo[1.1.0]butane. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/anie.201502827
  • Bonding situation in Be[N(SiMe3)2]2-an experimental and computational study
    Naglav, D. and Neumann, A. and Bläser, D. and Wölper, C. and Haack, R. and Jansen, G. and Schulz, S.
    Chemical Communications 51 (2015)
    The solid state structure of Be[N(SiMe3)2]2 (1) was determined by in situ crystallisation and the bonding situation investigated by quantum chemical calculations. The Be-N bond is predominantly ionic, but some evidence for the presence of a partial Be-N double bond character was found. © The Royal Society of Chemistry 2015.
    view abstract10.1039/c4cc09732g
  • Chemical vapor deposition of Si/SiC nano-multilayer thin films
    Weber, A. and Remfort, R. and Wöhrl, N. and Assenmacher, W. and Schulz, S.
    Thin Solid Films 593 (2015)
    Stoichiometric SiC films were deposited with the commercially available single source precursor Et3SiH by classical thermal chemical vapor deposition (CVD) as well as plasma-enhanced CVD at low temperatures in the absence of any other reactive gases. Temperature-variable deposition studies revealed that polycrystalline films containing different SiC polytypes with a Si to carbon ratio of close to 1:1 are formed at 1000°C in thermal CVD process and below 100°C in the plasma-enhanced CVD process. The plasma enhanced CVD process enables the reduction of residual stress in the deposited films and offers the deposition on temperature sensitive substrates in the future. In both deposition processes the film thickness can be controlled by variation of the process parameters such as the substrate temperature and the deposition time. The resulting material films were characterized with respect to their chemical composition and their crystallinity using scanning electron microscope, energy dispersive X-ray spectroscopy (XRD), atomic force microscopy, X-ray diffraction, grazing incidence X-ray diffraction, secondary ion mass spectrometry and Raman spectroscopy. Finally, Si/SiC multilayers of up to 10 individual layers of equal thickness (about 450 nm) were deposited at 1000°C using Et3SiH and SiH4. The resulting multilayers features amorphous SiC films alternating with Si films, which feature larger crystals up to 300 nm size as measured by transmission electron microscopy as well as by XRD. XRD features three distinct peaks for Si(111), Si(220) and Si(311). © 2015 Published by Elsevier B.V.
    view abstract10.1016/j.tsf.2015.08.042
  • Covalently bonded compounds of heavy group 15/16 elements - Synthesis, structure and potential application in material sciences
    Schulz, S.
    Coordination Chemistry Reviews 297-298 (2015)
    Our understanding on the nature of weak intermolecular metal-metal interactions as well as of multiple bonding in group 15/16 chemistry, in particular of compounds containing the heaviest elements of both groups - Sb, Bi, Se, and Te - is still scarce. These types of interactions are particularly important for the chemical and physical properties of such main group element compounds. For instance, the formation and disruption of weak intermolecular metal-metal interactions are the origin of the so-called thermochroism. The structural characterization of compounds containing sterically less demanding organic substituents is therefore of particular interest, since the capability of small substituents to kinetically stabilize the respective metal centers - and hence to suppress intermolecular interactions - is expected to be rather less pronounced. We will herein summarize the most recent results reported for the synthesis and structural characterization of group 15/16 compounds containing a direct (polar-covalent) element-element bond including compounds containing a terminal, formally double bond. In addition, the capability of selected compounds to serve as single-source precursor for the synthesis of the corresponding nanomaterials, in particular Sb<inf>2</inf>Te<inf>3</inf> and Bi<inf>2</inf>Te<inf>3</inf>, by using wet chemical methods as well as gas phase approaches such as metal organic chemical vapor deposition (MOCVD) processes will be demonstrated. © 2014 Elsevier B.V.
    view abstract10.1016/j.ccr.2014.11.003
  • MeL2Zn2(μ-1,6-Ph2-N6)-a building block for new hexazene complexes
    Gondzik, S. and Wölper, C. and Haack, R. and Jansen, G. and Schulz, S.
    Dalton Transactions 44 (2015)
    The zinc hexazene complex MeL<inf>2</inf>Zn<inf>2</inf>(μ-1,6-Ph<inf>2</inf>-N<inf>6</inf>) 1 (MeL = HC[C(Me)N(2,4,6-Me<inf>3</inf>C<inf>6</inf>H<inf>2</inf>)]<inf>2</inf>) is a suitable hexazene transfer reagent in reactions with main group metal and transition metal complexes containing M-Me units. The reactions proceed with elimination of MeLZnMe and the resulting complexes were characterized by NMR and IR spectroscopy and single crystal X-ray diffraction (5, 8). Quantum chemical calculations were performed to investigate the electronic structure of 5′ and 8′ in more detail and to identify the absorption bands of the hexazene unit. © 2015 The Royal Society of Chemistry.
    view abstract10.1039/c5dt02423d
  • Non-innocence of β-diketiminato ligands
    Gondzik, S. and Bläser, D. and Wölper, C. and Schulz, S.
    Journal of Organometallic Chemistry 783 (2015)
    The homoleptic thio-β-ketiminate zinc complex [MesNC(Me)CH{C(Me)NMes}S]2Zn (1) was obtained from reactions of elemental sulfur with the β-diketiminato zinc complexes [CH{C(Me)NMes}2]ZnMe, [CH{C(Me)NMes}2]2Zn2 and [[CH{C(Me)NMes}2]Zn-TePh]2. 1 and the byproducts were characterized by multinuclear NMR (1H, 13C, 125Te) and IR spectroscopy, elemental analyses as well as by single crystal X-ray diffraction. © 2015 Published by Elsevier B.V.
    view abstract10.1016/j.jorganchem.2015.02.028
  • Oxidative addition of diethylchalcogenanes to lappert's germylene and stannylene
    Bendt, G. and Lapsien, S. and Steiniger, P. and Bläser, D. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie 641 (2015)
    Oxidative addition of diethyldichalcogenanes Et<inf>2</inf>E<inf>2</inf> (E = S, Se, Te) to bis[bis(trimethylsilyl]amido]germylene and -stannylene M[N(SiMe<inf>3</inf>)<inf>2</inf>]<inf>2</inf> (M = Ge, Sn) proceed with formation of the corresponding bis(ethylchalcogenato)germanes (Me<inf>3</inf>Si)<inf>2</inf>N)<inf>2</inf>Ge(EEt)<inf>2</inf> [E = S (1), Se (2), Te (3)] and -stannanes (Me<inf>3</inf>Si)<inf>2</inf>N)<inf>2</inf>Sn(EEt)<inf>2</inf> [E = S (4), Se (5), Te (6)]. The solid state structures of 1-6 were determined by single-crystal X-ray diffraction. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/zaac.201500023
  • Record figure of merit values of highly stoichiometric Sb2Te3 porous bulk synthesized from tailor-made molecular precursors in ionic liquids
    Heimann, S. and Schulz, S. and Schaumann, J. and Mudring, A. and Stötzel, J. and MacUlewicz, F. and Schierning, G.
    Journal of Materials Chemistry C 3 (2015)
    We report on the synthesis of Sb2Te3 nanoparticles with record-high figure of merit values of up to 1.5. The central thermoelectric parameters, electrical conductivity, thermal conductivity and Seebeck coefficient, were independently optimized. The critical influence of porosity for the fabrication of highly efficient thermoelectric materials is firstly demonstrated, giving a strong guidance for the optimization of other thermoelectric materials. © The Royal Society of Chemistry 2015.
    view abstract10.1039/c5tc01248a
  • Synthesis and X-ray Crystal Structure of Diimidosulfinate Transition Metal Complexes
    Bayram, M. and Bläser, D. and Wölper, C. and Schulz, S.
    Organometallics 34 (2015)
    Bis(trimethylsilyl)sulfurdiimide S(NSiMe3)2 reacts with equimolar amounts of Me2Zn and Cp∗2Zn either with insertion into the metal-carbon bond and formation of the expected S-methyl diimidosulfinate complex [MeZnN(SiMe3)S(Me)NSiMe3]2 1 or the unexpected complex {Me3SiNS[N(SiMe3)SNSiMe3]N(SiMe3)Zn}2 2. Insertion reactions were also observed with Cp∗MMe3 (M = Ti, Zr, Hf), yielding Cp∗(Me)2M[Me3SiNS(Me)NSiMe3] (M = Ti 3, Zr 4, Hf 5), whereas the corresponding Cl-substituted derivatives Cp∗(Cl)2M[(Me3SiNS(Me)NSiMe3] (M = Ti 6, Zr 7, Hf 8) were obtained from salt elimination reactions of Li S-methyl diimidosulfinate (Me3SiN)2S(Me)Li(thf)]2 9 with Cp∗MCl3. Compounds 1-8 were characterized by heteronuclear NMR (1H and 13C) and IR spectroscopy, and the solid state structures of 1-5 and 9 were determined by single crystal X-ray diffraction. © 2015 American Chemical Society.
    view abstract10.1021/acs.organomet.5b00407
  • Synthesis and X-ray crystal structures of zinc dichloride complexes supported by a β-Diimine ligand
    Scheiper, C. and Naglav, D. and Bläser, D. and Wölper, C. and Schulz, S.
    Zeitschrift fur Anorganische und Allgemeine Chemie 641 (2015)
    β-Diimine zinc dichloride complexes [CH<inf>2</inf>{C(Me)NAr}<inf>2</inf>]ZnCl<inf>2</inf> [Ar = Mes (1), Dipp (2)] were obtained from the reactions of ZnCl<inf>2</inf> with the corresponding β-iminoamines [ArN(H)C(Me)CHC(Me)NAr]. Complexes 1 and 2 were characterized by multinuclear NMR (1H, 13C) and IR spectroscopy, elemental analyses as well as by single-crystal X-ray diffraction. The energy differences between the enamine-imine tautomers of the β-iminoamines were quantified by quantum chemical calculations. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/zaac.201500046
  • Synthesis of Binary Sb2E3 (E = S, Se) and Ternary Sb2(S,Se)3 Nanowires Using Tailor-Made Single-Source Precursors
    Heimann, S. and Assenmacher, W. and Prymak, O. and Schulz, S.
    European Journal of Inorganic Chemistry 2015 (2015)
    Thermal decomposition of four single-source precursors of the type (Et<inf>2</inf>Sb)<inf>2</inf>E and Et<inf>3</inf>SbE (E = S, Se) at 170 °C in the presence of suitable capping agents yielded binary Sb<inf>2</inf>S<inf>3</inf> and Sb<inf>2</inf>Se<inf>3</inf> nanowires. In addition, simultaneous decomposition of (Et<inf>2</inf>Sb)<inf>2</inf>S and(Et<inf>2</inf>Sb)<inf>2</inf>Se gave the ternary phase Sb<inf>2</inf>(S,Se)<inf>3</inf> with almost equal S and Se concentrations. The materials were characterized by XRD, REM, EDX, ED and HRTEM. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201500325
  • Synthesis of Heterobimetallic Group 13 Compounds via Oxidative Addition Reaction of Gallanediyl LGa and InEt3
    Ganesamoorthy, C. and Blaser, D. and Wolper, C. and Schulz, S.
    Organometallics 34 (2015)
    Equimolar amounts of LGa (L = [(2,6-i-Pr-2-C6H3)NC(Me)](2)CH) and InEt3 were found to react with insertion into the Incarbon bond and formation of LGa(Et)InEt2 (1), while in the presence of the N-heterocyclic carbene It-Bu [C(Nt-Bu2CH)(2)], the base-stabilized compound LGa(Et)Et2In <- It-Bu (2) was formed, which shows an abnormal binding mode of the NHC group. In addition, the reaction of InEt3 with two equivalents of LGa occurred with double insertion and formation of [LGa(Et)](2)InEt (3). 1-3 were characterized by heteronuclear NMR (H-1, C-13) and IR spectroscopy, their solid-state structures were determined by single-crystal X-ray analyses, and their thermal stability was investigated by in situ NMR spectroscopy.
    view abstract10.1021/acs.organomet.5b00302
  • Synthesis, Solid-State Structures, and Computational Studies of Half-Sandwich Cp∗BeX (X = Cl, Br, I) Compounds
    Naglav, D. and Tobey, B. and Neumann, A. and Bläser, D. and Wölper, C. and Schulz, S.
    Organometallics 34 (2015)
    The solid-state structures of half-sandwich beryllium complexes Cp∗BeX (X = Cl (1), Br (2), I (3)) are described. All attempts to synthesize Cp∗BeF (4) by reaction of 1-3 with several fluorinating reagents such as AgF<inf>2</inf>, XeF<inf>2</inf>, 4-FC<inf>6</inf>H<inf>4</inf>IF<inf>2</inf>, AgF, NaF, and Me<inf>4</inf>NF failed. However, the reaction of 3 and AgF in resulted in the unexpected synthesis of the known beryllocene Cp∗<inf>2</inf>Be (5). Quantum-chemical calculations were performed to investigate the electronic structures of 1-4. (Chemical Equation Presented). © 2015 American Chemical Society.
    view abstract10.1021/acs.organomet.5b00389
  • Te-Te and Te-C bond cleavage reactions using a monovalent gallanediyl
    Ganesamoorthy, C. and Bendt, G. and Bläser, D. and Wölper, C. and Schulz, S.
    Dalton Transactions 44 (2015)
    LGa (L = [(2,6-i-Pr<inf>2</inf>-C<inf>6</inf>H<inf>3</inf>)NC(Me)]<inf>2</inf>CH) reacts with elemental tellurium with formation of the Te-bridged compound [LGa-μ-Te]<inf>2</inf>1, whereas the reactions with Ph<inf>2</inf>Te<inf>2</inf> and i-Pr<inf>2</inf>Te occurred with cleavage of the Te-Te and Te-C bond, respectively, and subsequent formation of LGa(TePh)<inf>2</inf>2 and LGa(i-Pr)Tei-Pr 3. 1-3 were characterized by heteronuclear NMR (1H, 13C, 125Te) and IR spectroscopy and their solid state structures were determined by single crystal X-ray analyses. © The Royal Society of Chemistry 2015.
    view abstract10.1039/c5dt00172b
  • Van der Waals epitaxial MOCVD-growth of (BixSb1-x)2Te3 (0 < x < 1) films
    Bendt, G. and Sonntag, J. and Lorke, A. and Assenmacher, W. and Hagemann, U. and Schulz, S.
    Semiconductor Science and Technology 30 (2015)
    Epitaxial (Bi<inf>x</inf>Sb<inf>1-x</inf>)<inf>2</inf>Te<inf>3</inf> films with (0 < x < 1) were grown by the metal-organic chemical vapour deposition (MOCVD) process at 400 °C using the tailor-made precursors Et<inf>2</inf>Te<inf>2</inf>, i-Pr<inf>3</inf>Sb and Et<inf>3</inf>Bi. The films grown on Al<inf>2</inf>O<inf>3</inf>(0001) substrates show a very smooth surface morphology as shown by a scanning electron microscope (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM), while those grown on Si(100) are rather polycrystalline. The chemical composition of the crystalline films (x-ray powder diffraction (XRD)) was investigated by energy-dispersive x-ray (EDX) and x-ray photoelectron spectroscopy (XPS), and the in-plane transport properties were measured, and a strong dependency from the bismuth content was found, which allows the tuning of the carrier concentration and mobility in a wide range. © 2015 IOP Publishing Ltd.
    view abstract10.1088/0268-1242/30/8/085021
  • Wet-chemical synthesis of different bismuth telluride nanoparticles using metal organic precursors-single source vs. dual source approach
    Bendt, G. and Weber, A. and Heimann, S. and Assenmacher, W. and Prymak, O. and Schulz, S.
    Dalton Transactions 44 (2015)
    Thermolysis of the single source precursor (Et<inf>2</inf>Bi)<inf>2</inf>Te 1 in DIPB at 80 °C yielded phase-pure Bi<inf>4</inf>Te<inf>3</inf> nanoparticles, while mixtures of Bi<inf>4</inf>Te<inf>3</inf> and elemental Bi were formed at higher temperatures. In contrast, cubic Bi<inf>2</inf>Te particles were obtained by thermal decomposition of Et<inf>2</inf>BiTeEt 2 in DIPB. Moreover, a dual source approach (hot injection method) using the reaction of Te(SiEt<inf>3</inf>)<inf>2</inf> and Bi(NMe<inf>2</inf>)<inf>3</inf> was applied for the synthesis of different pure Bi-Te phases including Bi<inf>2</inf>Te, Bi<inf>4</inf>Te<inf>3</inf> and Bi<inf>2</inf>Te<inf>3</inf>, which were characterized by PXRD, REM, TEM and EDX. The influence of reaction temperature, precursor molar ratio and thermolysis conditions on the resulting material phase was verified. Moreover, reactions of alternate bismuth precursors such as Bi(NEt<inf>2</inf>)<inf>3</inf>, Bi(NMeEt)<inf>3</inf> and BiCl<inf>3</inf> with Te(SiEt<inf>3</inf>)<inf>2</inf> were investigated. © 2015 The Royal Society of Chemistry.
    view abstract10.1039/c5dt02072g
  • Bi-Zn bond formation in liquid ammonia solution: [Bi-Zn-Bi]4-, a linear polyanion that is Iso(valence)-electronic to CO2
    Benda, C.B. and Köchner, T. and Schäper, R. and Schulz, S. and Fässler, T.F.
    Angewandte Chemie - International Edition 53 (2014)
    Reactions of the zinc(I) complex [Zn2(Mesnacnac)2] (Mesnacnac=[(2,4,6-Me3C6H2)NC(Me)] 2CH) with solid K3Bi2 dissolved in liquid ammonia yield crystals of the compound K4[ZnBi2] ·(NH3)12 (1), which contains the molecular, linear heteroatomic [Bi-Zn-Bi]4- polyanion (1a). This anion represents the first example of a three-atomic molecular ion of metal atoms being iso(valence)-electronic to CO2 and being synthesized in solution. The analogy of the discrete [Bi-Zn-Bi]4- anion and the polymeric 1 ∞ [(ZnBi4/2)4-] unit to monomeric CO2 and polymeric SiS2 is rationalized. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/anie.201404343
  • Deposition of topological insulator Sb2Te3 films by an MOCVD process
    Bendt, G. and Zastrow, S. and Nielsch, K. and Mandal, P.S. and Sánchez-Barriga, J. and Rader, O. and Schulz, S.
    Journal of Materials Chemistry A 2 (2014)
    Layered Sb2Te3 films were grown by a MOCVD process on Al2O3(0001) substrates at 400 °C by use of i-Pr 3Sb and Et2Te2 and characterized by SEM, AFM, XRD, EDX and Auger spectroscopy. The electrical sheet resistivity was measured in the range of 4 to 400 K, showing a monotonic increase with increasing temperature. The valence band structure probed by angle-resolved photoemission shows the detailed dispersions of the bulk valence band and the topological surface state of a quality no less than for optimized bulk single crystals. The surface state dispersion gives a Dirac point roughly 30 meV above the Fermi level leading to hole doping and the presence of bulk valence states at the Fermi energy. © 2014 the Partner Organisations.
    view abstract10.1039/c4ta00707g
  • Magnetic vortices induced by a monopole tip
    Magiera, M.P. and Schulz, S.
    IEEE Transactions on Magnetics 50 (2014)
    A ferromagnetic monolayer with an easy-plane anisotropy scanned by a magnetic tip that is moved with constant velocity \({v}\) is studied using atomistic computer simulations. The spin dynamics are treated using the Landau-Lifshitz-Gilbert equation. To study the influence of the tip's field, it is modeled by a monopole field instead of a dipole field, which is a common near-field approximation of a scanning probe microscopy cantilever. The magnetic structures induced by the moving tip are analyzed with respect to the strength of the coupling as well as the scanning velocity, and the energy dissipation is calculated. The results agree with calculations in a continuum model using Thiele's equation, as well as with earlier results obtained from simulations using a dipolar tip. The quantitative influence of the field is illustrated using energetic arguments. © 2014 IEEE.
    view abstract10.1109/TMAG.2014.2317457
  • Methanetrisamidines in coordination chemistry-syntheses, structures and CH-NH tautomerism
    Gutschank, B. and Schulz, S. and Bläser, D. and Wölper, C.
    Dalton Transactions 43 (2014)
    Methanetrisamidines {HC[C(NR)NHR]3} (R = i-Pr 1a; Ph 1b) were reacted with different metal complexes. Reaction of 1a with NiCl 2(H2O)6 occurred with protonation of 1a and formation of {[C(C(NHi-Pr)2)3]2+[NiCl 4]2-} 2, whereas the reaction with CuCl gave [C(C(N(i-Pr)CuCl)NHi-Pr)2(C(NHi-Pr)2)] 3. The formation of 2 and 3, which contain the N-H tautomeric form of 1a, occurred with H-migration from carbon to nitrogen. In contrast, reactions of 1b with [M(NCMe) 3(CO)3] (M = Cr, Mo, W) yielded octahedral complexes fac-[M(CO)3CH(C(NHPh)NPh)3] (M = Cr 4a, Mo 4b, W 4c), in which the C-H tautomeric form is preserved. 1b is a rather strong σ-donor ligand as was shown by IR spectroscopy. The structures of 2, 3 and 4a were determined by single crystal X-ray diffraction. © 2014 The Royal Society of Chemistry.
    view abstract10.1039/c3dt53261e
  • Perfluorodecalin-soluble fluorescent dyes for the monitoring of circulating nanocapsules with intravital fluorescence microscopy
    Laudien, J. and Naglav, D. and Groß-Heitfeld, C. and Ferenz, K.B. and De Groot, H. and Mayer, C. and Schulz, S. and Schnepf, A. and Kirsch, M.
    Journal of Microencapsulation 31 (2014)
    Perfluorodecalin (PFD) is an established artificial oxygen carrier due to its physical capability to solve the respiratory gases oxygen and carbon dioxide. PFD-filled poly(n-butyl-cyanoacrylate) (PACA) nanocapsules are already discussed as effective artificial oxygen carriers, and their principal suitability for intravenous administration had been shown. To further elucidate their action in vivo, it is imperative to characterise their preclinical safety and particularly their biodistribution. For these purposes, intravital fluorescence microscopy would display an attractive technique in order to monitor the PACA nanocapsules in vivo, but unfortunately, it is impossible to stain the PACA nanocapsules with a fluorescent dye fulfilling special criteria required for in vivo microscopy. In order to develop such a dye, a long-chained fluorinated thiol was used to modify a BODIPY derivative that is a highly fluorescent organic compound belonging to the difluoro-boraindacene family, as well as to functionalise mesoscopic systems, such as CdSe/ZnS-quantum dots and gold nanoparticles. Furthermore, a functionalisation of porphyrin derivatives was investigated by placing divalent ions in the centre of these systems. Due to the high solubility of all synthesised dyes in PFD, it should be possible to stain PFD-filled particles in general. However, only the functionalised BODIPY derivative was suitable for in vivo monitoring of the PFD-filled PACA nanocapsules. © 2014 Informa UK Ltd.
    view abstract10.3109/02652048.2014.918668
  • Plasma-enhanced chemical vapor deposition of graphene on copper substrates
    Wöhrl, N. and Ochedowski, O. and Gottlieb, S. and Shibasaki, K. and Schulz, S.
    AIP Advances 4 (2014)
    A plasma enhanced vapor deposition process is used to synthesize graphene from a hydrogen/methane gas mixture on copper samples. The graphene samples were transferred onto SiO2 substrates and characterized by Raman spectroscopic mapping and atomic force microscope topographical mapping. Analysis of the Raman bands shows that the deposited graphene is clearly SLG and that the sheets are deposited on large areas of several mm2. The defect density in the graphene sheets is calculated using Raman measurements and the influence of the process pressure on the defect density is measured. Furthermore the origin of these defects is discussed with respect to the process parameters and hence the plasma environment. © 2014 Author(s).
    view abstract10.1063/1.4873157
  • Reaction of L2Zn2 with Ph2E 2-synthesis of LZnEPh and reactions with oxygen and H-acidic substrates
    Gondzik, S. and Schulz, S. and Bläser, D. and Wölper, C.
    Chemical Communications 50 (2014)
    L<inf>2</inf>Zn<inf>2</inf> (L = HC[C(Me)N(2,4,6-Me<inf>3</inf>C <inf>6</inf>H<inf>2</inf>)]<inf>2</inf>) and Ph<inf>2</inf>E<inf>2</inf> (E = Se, Te) react to form LZnSePh (1) and LZnTePh (2). 1 and 2 further react with H<inf>2</inf>O and EtOH to form LZnOH (3) and LZnOEt (4), respectively, whereas the reaction of 2 with oxygen yielded [LZnOTe(O)Ph]<inf>2</inf> (5). 1, 4 and 5 were characterized by single crystal X-ray diffraction. © 2014 The Royal Society of Chemistry.
    view abstract10.1039/c3cc48677j
  • Reactions of a Zn(i) complex with group 14 azides-formation of zinc azide and zinc hexazene complexes
    Gondzik, S. and Schulz, S. and Bläser, D. and Wölper, C. and Haack, R. and Jansen, G.
    Chemical Communications 50 (2014)
    Two zinc hexazene complexes L<inf>2</inf>Zn<inf>2</inf>(μ-1,6-R <inf>2</inf>-N<inf>6</inf>) (L = HC[C(Me)N(2,4,6-Me<inf>3</inf>C <inf>6</inf>H<inf>2</inf>)]<inf>2</inf>; R = Ph (3), Dipp = 2,6-i-Pr <inf>2</inf>C<inf>6</inf>H<inf>3</inf> (4)), were synthesized by reaction of the Zn(i) complex L<inf>2</inf>Zn<inf>2</inf> (1) with phenyl azide and 2,6-diisopropylphenyl azide, respectively. 3 represents the second structurally characterized transition metal hexazene complex. In contrast, reactions of 1 with Me<inf>3</inf>MN<inf>3</inf> (M = Si, Sn) yielded the azido complex [LZn(μ-N<inf>3</inf>)]<inf>2</inf> (2) and Me<inf>3</inf>M-MMe<inf>3</inf>. © 2014 The Royal Society of Chemistry.
    view abstract10.1039/c3cc47687a
  • Sequential Bi-C bond activation reactions of BiEt3via insertion reactions of RE {R = HC[C(Me)N(2,6-i-Pr2C6H3)]2; E = Al, Ga, In}
    Ganesamoorthy, C. and Bläser, D. and Wölper, C. and Schulz, S.
    Chemical Communications 50 (2014)
    Two of the Bi-C bonds of BiEt3 are sequentially activated by mono-valent RM {R = HC[C(Me)N(2,6-i-Pr2C6H3)]2; M = Al, Ga, In}. The first Bi-C bond activation leads to the formation of insertion complexes, [RMEt(BiEt2)] (M = Al 1; Ga 2; In 3), whereas the consecutive second activation proceeds through a reductive elimination of RMEt2 (M = Al 4, Ga 5), elemental Bi and BiEt3. © the Partner Organisations 2014.
    view abstract10.1039/c4cc05028b
  • Solid-state structures of bis(diethylbismuthanyl)sulfane, -selenane, and -tellurane
    Heimann, S. and Bläser, D. and Wölper, C. and Schulz, S.
    Organometallics 33 (2014)
    Tetraethyldibismuthine (Bi2Et4) reacts with elemental chalcogens with insertion into the Bi-Bi bond and formation of bis(diethylbismuthanyl)chalcogenanes ((Et2Bi)2E; E = S (1), Se (2), Te (3)). The structures of 1-3 were determined by single crystal X-ray diffraction. The complexes exclusively adopt syn-anti conformations in the solid state. The molecules show weak intermolecular Bi··· chalcogen contacts, resulting in the formation of a three-dimensional network of corner-shared Bi4E tetrahedra (E = S, Se, Te). © 2014 American Chemical Society.
    view abstract10.1021/om500208c
  • Syntheses and solid-state structures of Et2SbTeEt and Et2BiTeEt
    Heimann, S. and Kuczkowski, A. and Bläser, D. and Wölper, C. and Haack, R. and Jansen, G. and Schulz, S.
    European Journal of Inorganic Chemistry 2014 (2014)
    Diethylstibanyl- and diethylbismuthanyl telluranes Et2MTeEt (M = Sb 1, Bi 2) as well as tBu3Sb (3) were structurally characterized by single-crystal X-ray diffraction. Single crystals of 1-3 were grown by using an IR-laser-assisted technique. Compounds 1 and 2 form short intermolecular E···Te interactions in the solid state, which were further investigated with dispersion-corrected density functional theory. Single crystals of Et2M-TeEt (M = Sb 1, Bi 2) as well as tBu3Sb (3) were grown by using an IR-laser-assisted technique. Compounds 1 and 2 form short intermolecular E···Te interactions in the solid state, which were further investigated with dispersion-corrected density functional theory. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201402471
  • Syntheses and structures of bis-amidinate-alane complexes
    Bayram, M. and Bläser, D. and Wölper, C. and Schulz, S.
    Organometallics 33 (2014)
    Insertion reactions of α,ω-bis-carbodiimides (RNCN) 2X (1-5: R = Et, t-Bu, Ph; X = C3H6, C 4H8) with 2 equiv of AlMe3 yielded the dinuclear tethered bis-amidinate-alane complexes [RNC(Me)NAlMe2] 2X (R = Et, X = C4H8 (6); R = t-Bu, X = C 3H6 (7), C4H8 (8)). Analogous reactions with 4 equiv of AlMe3 resulted in the coordination of two additional AlMe3 molecules, yielding the tetranuclear bis-amidinate complexes [EtN(AlMe3)C(Me)NAlMe2]2X (X = C 3H6 (9), C4H8 (10)) and [t-BuNC(Me)N(AlMe3)AlMe2]2X (X = C 3H6 (11), C4H8 (12)). In addition, equimolar reactions between (RNCN)2X (R = Et, X = C3H 6, C4H8; R = Ph, X = C4H 8) and 2 equiv of AlMe3 at elevated temperatures occurred with intramolecular cyclization and formation of [EtNC(Me)NC3H 6N(AlMe3)CNEt]AlMe2 (13) and [RNC(Me)NC 4H8N(AlMe3)CNR]AlMe2 (R = Et (14), Ph (15)). Hydrolysis of 11 gave the protonated free ligand PhNC(Me)NC 4H8N(H)CNPh (16) in high yield. 6-16 were characterized by elemental analyses, multinuclear NMR (1H, 13C) and IR spectroscopy, and single-crystal X-ray diffraction (7, 10-14, 16). © 2014 American Chemical Society.
    view abstract10.1021/om5002217
  • Syntheses, solid-state structures and catalytic activity of zinc carboxylate complexes in lactide polymerization
    Scheiper, C. and Wölper, C. and Bläser, D. and Roll, J. and Schulz, S.
    Zeitschrift fur Naturforschung - Section B Journal of Chemical Sciences 69 (2014)
    Three dinuclear zinc carboxylate complexes [L1-3Zn(μ,η2-O<inf>2</inf>CPh)]<inf>2</inf> (1, 2, 4) containing either the bidentate N,N'-chelating β-diketiminate ligand RNC(Me)C(H)C(Me)NR (R = 2,6-iPr<inf>2</inf>-C<inf>6</inf>H<inf>3</inf>, L1, complex 1), the tridentate O,N,N-chelating ligand OC(Me)C(H)C(Me)NCH<inf>2</inf>CH<inf>2</inf>NMe<inf>2</inf> (L2, complex 2) or the bis-N,N'-chelating bis-β-diketiminate ligand RNC(Me)C(H)C(Me)NNC(Me)-C(H)C(Me)NR (R = 2,6-iPr<inf>2</inf>-C<inf>6</inf>H<inf>3</inf>, L3, complex 4) were synthesized and characterized including single-crystal X-ray diffraction. Reaction of the neutral bis-β-diketimine (L3(H)<inf>2</inf>) with two equivalents of ZnMe<inf>2</inf> leads to the expected heteroleptic dinuclear zinc complex L3 (ZnMe)<inf>2</inf> 3 in 93% yield. Further reaction with benzoic acid PhCO<inf>2</inf>H leads to complex 4. Complex 2 forms a rather strong carboxylate-bridged dimer, whereas the carboxylate groups in complexes 1 and 4 act as asymmetrical bridges between both Zn atoms, pointing to the formation of a weakly bonded dimer. The zinc atoms in 1 and 4 are tetrahedrally coordinated, whereas in 2 the coordination number is increased to five due to the coordination of the pendant donor arm. The ring opening polymerization (ROP) of rac-lactide was investigated with the zinc complexes 1-4 and diazabicycloundec-7-ene (DBU) as a co-catalyst. Complexes 2 and 3 are active polymerization catalysts, which in the presence of DBU converted 200 equiv. of rac-lactide into polylactide within 10 min at ambient temperature. The analysis of the crude polymer showed that the lactide polymerization with catalyst 2 occurs via a slightly modified activated-monomer mechanism. © 2014 Verlag der Zeitschrift für Naturforschung, Tübingen.
    view abstract10.5560/ZNB.2014-4133
  • Synthesis and characterization of heteroleptic 1-tris(pyrazolyl)borate beryllium complexes
    Naglav, D. and Bläser, D. and Wölper, C. and Schulz, S.
    Inorganic Chemistry 53 (2014)
    The synthesis and crystal structures of 1-tris(pyrazolyl)borate beryllium halides TpBeX (X = Cl 1, Br 2, I 3, F 4), the pyrazole adduct of TpBeF (5) and of 1-tris(pyrazolyl)borate beryllium hydride, deuteride and azide TpBeX (X = H 6, 2H (D) 7, N3 8; Tp = 1-trispyrazolylborate) is described. In addition, 9Be-NMR spectroscopy is introduced as suitable analytical tool for the in situ characterization of heteroleptic organoberyllium halides, pseudohalides and hydrides. Studies in different solvents and solvent mixtures allowed the formulation of a reference guide for the chemical shift of heteroleptic coordination complexes of beryllium only based on variation of the second substituent. © 2014 American Chemical Society.
    view abstract10.1021/ic402895h
  • Synthesis, structure, and catalytic activity of tridentate, base-functionalized β-ketiminate zinc complexes in ring-opening polymerization of lactide
    Scheiper, C. and Dittrich, D. and Wölper, C. and Bläser, D. and Roll, J. and Schulz, S.
    European Journal of Inorganic Chemistry (2014)
    Zinc complexes [LZnR] containing tridentate β-ketiminate ligands with an additional side-arm donor {referred to as [NNO] ligands; L = L1 = OC(Me)C(H)C(Me)NCH2CH2CH2NMe2, R = Me (1), Et (2), Cl (3); L = L2 = OC(Me)C(H)C(Me)NCH 2CH2NMe2, R = Me (6), Et (7), Cl (9)} as well as cationic derivatives with a weakly coordinating anion [LZn][Al(OC(CF 3)3)4] [L = L1 (4), L = L 2 = (10)], a base-stabilized complex [L2Zn(dmap)Et] (8; dmap = 4-(dimethylamino)pyridine), and a base-free complex without a side-arm donor [L3ZnEt] [12, L3 = OC(Me)C(H)C(Me)N-2,6-iPr 2C6H3] were synthesized and characterized by single-crystal X-ray diffraction (1, 2, 3, 8, 9, 11, and 12). The ring-opening polymerization (ROP) of rac-lactide was studied with the zinc complexes 1-4, 6-10 and 12, mixtures of 7 and Lewis bases [7/1,8-diazabicycloundec-7-ene (7/DBU; 15), 7/tBuPy (16)], and 12/DBU (17). Lithium-β-ketiminates L 1Li (5), L2Li (11), DBU (13), and a mixture of L 2Li/DBU (14) were also investigated. All compounds except for 3, 4, 10, and 12 are active rac-lactide polymerization catalysts by a slightly modified activated-monomer mechanism. The catalytic activity of the complexes in rac-lactide polymerization reactions at ambient temperature increases with the addition of Lewis bases to the β-ketiminate zinc compounds. The highest activity was found for the mixture 7/DBU (15), which converted 200 equiv. of rac-lactide into polylactide within 1.5 min at ambient temperature. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201301462
  • Temperature-Dependent Electron Shuffle in Molecular Group 13/15 Intermetallic Complexes
    Ganesamoorthy, C. and Bläser, D. and Wölper, C. and Schulz, S.
    Angewandte Chemie - International Edition 53 (2014)
    Monovalent RAl (R=HC[C(Me)N(2,6-iPr2C6H3)]2) reacts with E2Et4 (E=Sb, Bi) with insertion into the weak E-E bond and subsequent formation of RAl(EEt2)2 (E=Sb 1; Bi 2). The analogous reactions of RGa with E2Et4 yield a temperature-dependent equilibrium between RGa(EEt2)2 (E=Sb 3; Bi 4) and the starting reagents. RIn does not interact with Sb2Et4 under various reaction conditions, but formation of RIn(BiEt2)2 (5) was observed in the reaction with Bi2Et4 at low temperature. Doing the shuffle: Reactions of monovalent RAl with E2Et4 (E=Sb, Bi; Ar=2,6-iPr2C6H3) proceed with E-E bond cleavage and formation of RAl(EEt2)2, whereas RGa forms a reversible chemical equilibrium with E2Et4 and RGa(EEt2)2. RIn does not react with Sb2Et4, but also forms a reversible equilibrium with Bi2Et4 at low temperatures. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/anie.201406304
  • The bonding situation in triethylchalcogenostiboranes-polarized single bonds vs. double bonds
    Heimann, S. and Bläser, D. and Wölper, C. and Haack, R. and Jansen, G. and Schulz, S.
    Dalton Transactions 43 (2014)
    Triethylchalcogenostiboranes Et3SbE (E = S 1, Se 2) were synthesized and their solid state structures were determined. The Sb-Se bond length is the shortest ever reported. Short Sb⋯E contacts were not observed. According to quantum chemical calculations, the bonding situation in 1 and 2 is best described as a polarized Sb-E single bond. This journal is © the Partner Organisations 2014.
    view abstract10.1039/c4dt01940g
  • Thermopower engineering of Bi2Te3 without alloying: The interplay between nanostructuring and defect activation
    Bae, C. and Böhnert, T. and Gooth, J. and Lim, S. and Lee, S. and Kim, H. and Heimann, S. and Schulz, S. and Shin, H. and Nielsch, K.
    Semiconductor Science and Technology 29 (2014)
    We report on the interplay between nanostructuring and defect activation in dense polycrystalline Bi2Te3 thin films in terms of the thermopower engineering. The Bi2Te3 thin films were prepared at relatively low temperatures (100-160 °C) by atomic layer deposition and their grains showed different sizes in the range of 50-200 nm according to the deposition temperatures. We monitored the conductivity, Seebeck coefficient, and power factor of all samples from the temperature of 50-400 K. By increasing the growth temperature, remarkably, we observed the gradual defect activation from the nominal p-type to n-type in our binary end compound, Bi2Te3 without any alloying. The present results give us an insight on the optimization of thermoelectric materials not only by nanostructuring (i.e., phonon engineering) but also by controlled defect activation (i.e., electron engineering). © 2014 IOP Publishing Ltd.
    view abstract10.1088/0268-1242/29/6/064003
  • Zr-based conversion layer on Zn-Al-Mg alloy coated steel sheets: Insights into the formation mechanism
    Lostak, T. and Maljusch, A. and Klink, B. and Krebs, S. and Kimpel, M. and Flock, J. and Schulz, S. and Schuhmann, W.
    Electrochimica Acta 137 (2014)
    Zr-based conversion layers are considered as environmentally friendly alternatives replacing trication phosphatation in the automotive industry. Based on excellent electronic barrier properties they provide an effective corrosion protection of the metallic substrate. In this work, thin protective layers were grown on novel Zn-Al-Mg alloy coated steel sheets by increasing the local pH-value at the sample surface leading to deposition of a Zr-based conversion layer. For this purpose Zn-Al-Mg alloy (ZM) coated steel sheets were treated in an aqueous model conversion solution containing well-defined amounts of hexafluorozirconic acid (H2ZrF6) and characterized after different immersion times with SKPFM and field emission SEM (FE-SEM)/EDX techniques. A deposition mechanism of Zr-based conversion coatings on microstructural heterogeneous Zn-Al-Mg alloy surfaces was proposed. © 2014 Elsevier Ltd.
    view abstract10.1016/j.electacta.2014.05.163
  • Formation and characterization of Fe3+-/Cu2+-modified zirconium oxide conversion layers on zinc alloy coated steel sheets
    Lostak, T. and Krebs, S. and Maljusch, A. and Gothe, T. and Giza, M. and Kimpel, M. and Flock, J. and Schulz, S.
    Electrochimica Acta 112 (2013)
    Zirconium oxide conversion layers are considered as environmentally friendly alternatives replacing chromate-based passivation layers in the coil-coating industry. Based on excellent electronic barrier properties they provide an effective corrosion protection of the metallic substrate. In this work, thin layers were grown on HDG-steel-substrates by increasing the local pH at the surface and were characterized using potentiodynamic polarization technique. The influence of Cu(NO3)2·3H 2O or Fe(NO3)3·9H2O on morphology and thickness of deposited protective layers were investigated by XPS, ToF-SIMS and FE-SEM. A significant film thickness increase was found by adding Cu2+ or Fe3+ ions to the conversion solution. In addition, growth kinetics was studied by in situ measurements of corrosion potential using potentiodynamic polarization technique. © 2013 Elsevier Ltd.
    view abstract10.1016/j.electacta.2013.08.161
  • Heterobimetallic metal-amidinate complexes by stepwise metalation of methanetrisamidines
    Gutschank, B. and Bayram, M. and Schulz, S. and Bläser, D. and Wölper, C.
    European Journal of Inorganic Chemistry (2013)
    The acidity of the four N-H groups in methanetrisamidine 1c differs significantly, thereby allowing stepwise metalation by metal organic compounds such as ZnMe2, AlMe3, and GaMe3. Dinuclear complexes 3a-c were formed under kinetic control in the reactions of 1c with 2 equiv. of the metal organic compounds at low temperatures, whereas prolonged reaction times at elevated temperature (100 °C) with 4 equiv. of ZnMe 2, AlMe3, and GaMe3 yielded the corresponding tetranuclear complexes 4a-c. The different acidity of the four N-H groups also allowed the stepwise metalation of 1c by two different metal organic complexes with the formation of the heterobimetallic complexes 5a and 5b. In addition, transmetalation by Zn/Al exchange was observed in the reaction of 3c with AlMe3, yielding the corresponding dinuclear aluminium complex 3a. The complexes were characterized by NMR and IR spectroscopy and single-crystal X-ray diffraction (3a, 4b, 5a). Methanetrisamidines can be two- and four-fold metalated by different metal organic complexes to form di- and tetranuclear homometallic complexes, respectively. Moreover, the different acidity of the N-H groups also allows the stepwise deprotonation by different organometallic reagents with the subsequent formation of heterobimetallic complexes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201300939
  • Low-temperature MOCVD of crystalline Ga2O3 nanowires using tBu3Ga
    Schulz, S. and Bendt, G. and Assenmacher, W. and Sager, D. and Bacher, G.
    Chemical Vapor Deposition 19 (2013)
    Crystalline Ga2O3 nanowires are synthesized via an Au-catalyzed, as well as a self-catalyzed, growth by a low-temperature metal-organic (MO)CVD process using tBu3Ga as a novel Ga source. Morphology, elemental composition, and crystallinity of the resulting nanowires are analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and selected area electron diffraction (SAED). Photoluminescence (PL) spectra of the Ga2O3 nanowires show efficient defect-luminescence in the visible and UV ranges with blue and green emission peaks at 430nm and 512 nm, respectively, at room temperature. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/cvde.201307060
  • Organoaluminum Complexes with Bonds to s-Block, p-Block, d-Block, and f-Block Metal Centers
    Schulz, S.
    Modern Organoaluminum Reagents: Preparation, Structure, Reactivity and Use 41 (2013)
    This chapter summarizes the recent developments in organoaluminum compounds containing at least one direct bond between aluminum and a s-block, p-block, d-block, or f-block metal center. General synthetic pathways to access such species are described along with their structural and bonding properties.
    view abstract10.1007/3418_2012_33
  • Single-Source Precursor-Based Deposition of Sb2Te3 Films by MOCVD
    Bendt, G. and Schulz, S. and Zastrow, S. and Nielsch, K.
    Chemical Vapor Deposition 19 (2013)
    The low-temperature metal-organic (MO)CVD of Sb2Te3 films is achieved by the use of the single-source precursor (Et2Sb)2Te, 1. The role of the substrate temperature on the deposition rate and the composition of the resulting film is described. The resulting Sb2Te3 films are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Auger spectroscopies. Moreover, the Seebeck coefficient of the Sb2Te3 film deposited at 200°C is determined, and the value of 160μVK-1 demonstrates the high quality and low carrier density of the film. (Et2Sb)2Te is a volatile, single-source-precursor for the MOCVD of Sb2Te3 films at low temperatures. The growth rates increase from 600nmh-1 at 200°C with increasing substrate temperature. The Sb2Te3 films consist of randomly oriented hexagonal nanoplates with a diameter of more than 2μm. In addition, Seebeck coefficients of up to 160μVK-1 demonstrate the high quality and low carrier density of the Sb2Te3 films. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/cvde.201207044
  • Solid-State structures of trialkylbismuthines BiR3 (R = Me, i -Pr)
    Schulz, S. and Kuczkowski, A. and Bläser, D. and Wölper, C. and Jansen, G. and Haack, R.
    Organometallics 32 (2013)
    Two trialkylbismuthines BiR3 (R = Me (1), i-Pr (2)) were structurally characterized by single-crystal X-ray diffraction. Single crystals were grown using an IR-laser-assisted technique. 1 forms short intermolecular Bi···Bi interactions in the solid state, which were further investigated through quantum chemical computations with ab initio coupled cluster and dispersion-corrected density functional methods. © 2013 American Chemical Society.
    view abstract10.1021/om400730r
  • Solution-based synthesis of GeTe octahedra at low temperature
    Schulz, S. and Heimann, S. and Kaiser, K. and Prymak, O. and Assenmacher, W. and Brüggemann, J.T. and Mallick, B. and Mudring, A.-V.
    Inorganic Chemistry 52 (2013)
    GeTe octahedra were prepared by reaction of equimolar amounts of GeCl 2·dioxane and Te(SiEt3)2 in oleylamine, whereas a slight excess of the Te precursor yielded GeTe octahedra decorated with elemental Te nanowires, which can be removed by washing with TOP. The mechanism of the GeTe formation is strongly influenced by the solvent. The expected elimination of Et3SiCl (dehalosilylation) only occurred in aprotic solvents, whereas Te(SiEt3)2 was found to react with primary and secondary amines with formation of silylamines. Temperature-dependent studies on the reaction in oleylamine showed that crystalline GeTe particles are formed at temperatures higher than 140 C. XRD, SAED, and HRTEM studies proved the formation of rhombohedral GeTe nanoparticles. These findings were confirmed by a single-crystal and powder X-ray analysis. The rhombohedral structure modification was found, and the structure was solved in the acentric space group R3m. © 2013 American Chemical Society.
    view abstract10.1021/ic402266j
  • Syntheses and solid-state structures of bis(dialkylstibanyl)sulfanes and -telluranes
    Heimann, S. and Schulz, S. and Bläser, D. and Wölper, C.
    European Journal of Inorganic Chemistry (2013)
    Distibines Sb2R4 (R = Me, Et) react with elemental chalcogens (E = S, Se, Te) with insertion into the Sb-Sb bond and formation of the corresponding bis(dialkylstibanyl)sulfanes, -selenanes, and -telluranes (R2Sb)2E. The structures of (Et2Sb) 2S (1), (Et2Sb)2Te (3), and (Me 2Sb)2Te (4) were determined by single-crystal X-ray diffraction. The complexes either adopt a syn-syn (1, 4) or syn-anti conformation (3) in the solid state. In addition, the compounds have different intermolecular interaction modes, which depend on the bridging chalcogen and the organic substituent bound to the Sb atoms. Bis(dialkylstibanyl)sulfanes, -selenanes, and -telluranes (R2Sb)2E were synthesized by reaction of Sb2R4 (R = Me, Et) with elemental chalcogens (E = S, Se, Te) and structurally characterized by single-crystal X-ray diffraction. The roles of the bridging chalcogen atom and the organic substituents on the packing of the molecules and their intermolecular interactions are discussed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201300767
  • Synthesis and crystal structure of a salt containing ∞ 1{Zn[trans-μ2(η3: η3-Ge9)]}2- anions: A polymer with Ge 9 zintl clusters bridged by Zn atoms
    Benda, C.B. and Schäper, R. and Schulz, S. and Fässler, T.F.
    European Journal of Inorganic Chemistry (2013)
    The reaction of an ethylenediamine (en) solution of K4Ge 9 with Zn2(Mesnacnac)2 {Mesnacnac = [(2,4,6-Me3C6H2)NC(Me)]2CH} in the presence of 18-crown-6 (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane) leads to the formation of the new compound [K(18-crown-6)]2{Zn[trans- μ2(η3:η3-Ge9)]}(en). A crystallographic structure determination revealed that the salt contains ∞ 1[Zn(Ge9)]2- polyanions in which each Zn atom bridges two Ge9 clusters by coordinating to opposite triangular faces of the Ge9 deltahedra. The polymeric chain can be formally described as consisting of a trans ZnII complex with two [η3:η3-Ge9]4- ligands. 1H NMR spectroscopic investigations indicated that the protonation of the Mesnacnac- ligand by the solvent ethylenediamine plays a crucial role in the disproportionation of the ZnI starting material and thus in the formation of the polymeric ZnII complex. In contrast, the reaction of ZnPh2 instead of Zn2(Mesnacnac)2 under the same conditions leads to the known complex [PhZn(η4- Ge9)]3-. Crystals of the compound [K(18-crown-6)] 2{Zn[trans-μ2(η3:η3- Ge9)]}(en), containing strands of ∞ 1{Zn[trans-μ2(η3:η3- Ge9)]}2- units in which Zn atoms connect Ge9 clusters in an η3-fashion, were obtained by the reaction of the binary Zintl phase K4Ge9 with Zn2(Mesnacnac) 2 (Mesnacnac = [(2,4,6-Me3C6H 2)NC(Me)]2CH) in ethylenediamine (en). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201301122
  • Synthesis and single crystal x-ray structures of cationic zinc β-diketiminate complexes
    Scheiper, C. and Schulz, S. and Wölper, C. and Bläser, D. and Roll, J.
    Zeitschrift fur Anorganische und Allgemeine Chemie 639 (2013)
    The cationic zinc complex [L1Zn][Al(OC(CF3) 3)4] (1) (L1 = {[(2,4,6-Me3-C 6H2)NC(Me)]2CH}) bearing a weakly coordinating aluminate anion was obtained from reaction of L1ZnCl with Li[Al(OC(CF3)3)4]. In addition, base-stabilized zinc cations [L1/2Zn(base)2][X] (2-5) (L2 = {[(2,6-iPr2-C6H3)NC(Me)]2CH}; X = [Al(OC(CF3)3)4], [B(C6F 5)4]) containing weakly coordinating anions and different Lewis bases (dimethylaminopyridine (dmap), tert-butylpyridine (tBuPy)) were synthesized and structurally characterized. Moreover, the solid-state structures of L1ZnMe (6) and the neutral base-stabilized complexes tBuPy-Zn(Cl)L1 (7) and base-Zn(Me)L2 (base = dmap 8, tBuPy 9) are reported and compared with those of 2-5. Preliminary studies showed that 1 is catalytically activity in lactide polymerization at 160 °C. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/zaac.201300119
  • Synthesis and structure of base-stabilized germanium(II) diazide IPrGe(N3)2
    Lyhs, B. and Bläser, D. and Wölper, C. and Schulz, S. and Haack, R. and Jansen, G.
    Inorganic Chemistry 52 (2013)
    Coordination of a strong σ-base has been shown to be an effective method for the stabilization of low valent main group element complexes. This general method was now used for the synthesis of the divalent germanium diazide. IPrGe(N3)21 represents the first neutral homoleptic germanium diazide that could be structurally characterized. © 2013 American Chemical Society.
    view abstract10.1021/ic400866c
  • The origin of thermochromic behavior in distibines: Still an open question
    Schulz, S. and Heimann, S. and Kuczkowski, A. and Bläser, D. and Wölper, C.
    Organometallics 32 (2013)
    A detailed structural investigation of Sb2Et4 using an in situ crystallization technique clearly shows that thermochromic behavior of distibines cannot be solely attributed to the formation of intermolecular Sb···Sb interactions in the solid state. Both the yellow and the red phase of Sb2Et4 showed almost identical bond lengths and angles including rather short intermolecular Sb·· ·Sb bond distances. © 2013 American Chemical Society.
    view abstract10.1021/om4003413
  • Thermoelectric transport and Hall measurements of low defect Sb 2Te3 thin films grown by atomic layer deposition
    Zastrow, S. and Gooth, J. and Boehnert, T. and Heiderich, S. and Toellner, W. and Heimann, S. and Schulz, S. and Nielsch, K.
    Semiconductor Science and Technology 28 (2013)
    Sb2Te3 has recently been an object of intensive research since its promising applicability in thermoelectric, in phase-change memory devices and as a topological insulator. In this work, we report highly textured Sb2Te3 thin films, grown by atomic layer deposition on Si/SiO2 wafers based on the reaction of SbCl 3 and (Et3Si)2Te. The low deposition temperature at 80 °C allows the pre-patterning of the Sb2Te 3 by standard lithography processes. A platform to characterize the Seebeck coefficient S, the electrical conductivity σ as well as the Hall coefficient RH on the same film has been developed. Comparing all temperature-dependent transport properties, three different conductive regions in the temperature range of 50-400 K are found. Room temperature values of S = 146 × 10-6 VK-1, σ = 104 Sm -1 and mobility M = 270.5 × 10-4 m2 V-1 s-1 are determined. The low carrier concentration in the range of n = 2.4 × 1018 cm-3 at 300 K quantifies the low defect content of the Sb2Te3 thin films. © 2013 IOP Publishing Ltd.
    view abstract10.1088/0268-1242/28/3/035010
  • A comparison of the solid-state structures of halogen azides XN3 (X=Cl, Br, I)
    Lyhs, B. and Bläser, D. and Wölper, C. and Schulz, S. and Jansen, G.
    Angewandte Chemie - International Edition 51 (2012)
    Delicate crystals: ClN3 adopts a polymeric structure in the solid state (see picture; N blue, Cl green) with short intermolecular Cl×××Cl distances, as was observed for the elemental halogen. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/anie.201206028
  • First structural characterization of neutral, base-stabilized group 15-pentaazides: Single Crystal X-ray structures of dmap-As(N 3) 5 and dmap-Sb(N 3) 5
    Lyhs, B. and Bläser, D. and Wölper, C. and Schulz, S. and Jansen, G.
    Inorganic Chemistry 51 (2012)
    Two neutral group 15-pentaazides dmap-As(N 3) 5 (1) and dmap-Sb(N 3) 5 (2) were synthesized and structurally characterized for the first time (dmap = 4-dimethylaminopyridine). Base-stabilization was confirmed to be very suitable for the kinetic stabilization of highly explosive covalent main group polyazides. © 2012 American Chemical Society.
    view abstract10.1021/ic300523k
  • Insertion reactions of heterocumulenes with zincocene Cp* 2Zn
    Schulz, S. and Schmidt, S. and Bläser, D. and Wölper, C.
    Zeitschrift fur Anorganische und Allgemeine Chemie 638 (2012)
    Zincocene Cp* 2Zn reacts with carbodiimides C(NR) 2 with insertion into the Zn-Cp* bond and formation of [(Cp*C(NR) 2] 2Zn [R = Et (1), iPr (2), Cy (3)]. In addition, the reaction of Cp* 2Zn with CS 2 under dry conditions gives (Cp*CS 2) 2Zn (4), whereas in the presence of a small amount of water [Zn 4(μ 4-O)(S 2CCp*) 6] (5) is obtained. Compounds 1-4 were characterized by NMR ( 1H, 13C) and IR spectroscopy as well as elemental analysis and single-crystal X-ray diffraction (2-4, 5 of poor quality). The solid-state structure of 5 is comparable to the carboxylate complex previously obtained from the reaction of Cp* 2Zn with CO 2. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/zaac.201200061
  • Ketoiminato and bisthiophosphinoyl-Methanediide ligands
    Schulz, S. and Schäper, R. and Bläser, D. and Wölper, C.
    Zeitschrift fur Anorganische und Allgemeine Chemie 638 (2012)
    Homoleptic zinc complexes of the type L2Zn containing monoanionic β-ketoiminate and bisthiophosphinoyl)methanide substituents were synthesized in almost quantitative yield by reaction of HCCMe) 2O)NH)CH2CH2NMe2) and H 2CPPh2=S)2 with zincocene Cp 2Zn at ambient temperature. The reactions proceeded with elimination of Cp*H. (HCCMe)2O)NCH2CH2NMe2)] 2Zn 1) and [HCPPh2=S)2]2Zn 2) were characterized by NMR 1H, 13C, 31P) and IR spectroscopy as well as elemental analysis and single crystal X-ray diffraction. 1 and 2 were also obtained in reactions of dizincocene, Cp 2Zn2, with two equivalents of the ligands. The reactions proceeded with disproportionation of initially formed monovalent dizinc complexes. © 2012 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim.
    view abstract10.1002/zaac.201200115
  • Reactivity of (β-diketiminato)zinc hydride toward lewis bases, heterocumulenes and cyclohexene oxide
    Bendt, G. and Schulz, S. and Spielmann, J. and Schmidt, S. and Bläser, D. and Wölper, C.
    European Journal of Inorganic Chemistry (2012)
    The reaction of LZnH (1) {L = Mesnacnac = [(2,4,6-Me 3C 6H 2)NC(Me)] 2CH} with 4-(dimethylamino)pyridine (dmap) yielded the Lewis acid-base adduct LZn(H)dmap (2), whereas LZn(Cl)dmap (3) was obtained from the equimolar reaction of LZnCl with dmap. In addition, reactions of 1 with di-tert-butylcarbodiimide [C(NtBu) 2] and tert-butyl thioisocyanate (tBuNCS) proceeded with insertion of the heterocumulene into the Zn-H bond and formation of [LZn(tBuNC(H)NtBu)] (4) and [LZn(tBuNC(H)S)] (5), whereas 1 reacted with Me 3SiN 3 with the elimination of Me 3SiH and formation of [LZnN 3] 2 (6). Moreover, the reaction of 1 with cyclohexene oxide (CHO) occurred with ring opening and formation of [LZnOCy] 2 (7) (Cy = cyclohexyl). Complexes 2-7 were characterized by multinuclear NMR ( 1H, 13C) and IR spectroscopy, elemental analyses and by single-crystal X-ray diffraction (2, 3, 6, 7). MesnacnacZnH {Mesnacnac = [(2,4,6-Me 3C 6H 2)NC(Me)] 2CH} reacts with 4-(dimethylamino)pyridine (dmap) upon adduct formation, whereas reactions with (tBuN) 2C, tBuNCS and CHO proceed with insertion into the Zn-H bond. In contrast, Me 3SiN 3 was found to react with MesnacnacZnH with the formation of MesnacnacZn(N 3), which forms an azido-bridged dimer in the solid state. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201200378
  • Solid-state structure of bromine azide
    Lyhs, B. and Bläser, D. and Wölper, C. and Schulz, S. and Jansen, G.
    Angewandte Chemie - International Edition 51 (2012)
    A new twist: The single-crystal structural analysis of BrN 3 is described. In contrast to IN 3, which forms chains, BrN 3 forms a helical structure in the solid state (see picture). Such a structural feature has not been previously observed in covalent p-block azide chemistry. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/anie.201108092
  • Structural characterization of amidinatobismuth(III) diazides
    Lyhs, B. and Bläser, D. and Wölper, C. and Haack, R. and Jansen, G. and Schulz, S.
    European Journal of Inorganic Chemistry (2012)
    Amidinatobismuth(III) diazides LBi(N 3) 2 {L 1 = [tBuC(NiPr) 2] (2), L 2 = [tBuC(NDipp) 2] (3, Dipp = 2,6-iPr 2-C 6H 3)} were synthesized in high yields by metathesis reactions of the corresponding halide-substituted complexes L 1BiI 2 (1) and L 2BiCl 2 with AgN 3. Compounds 1-3 were characterized by using elemental analyses, multinuclear NMR ( 1H, 13C), and IR spectroscopy as well as by using single-crystal X-ray diffraction (for 2, 3). © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201200699
  • Synthesis and X-ray crystal structures of heteroleptic zinc amidinate complexes
    Schmidt, S. and Schulz, S. and Bläser, D. and Wölper, C.
    Main Group Metal Chemistry 35 (2012)
    The synthesis of heteroleptic zinc amidinate complexes is reported. Reactions of LZnI [L=t-BuC(NDipp) 2; Dipp=2,6-i-Pr 2-C 6H 3] with diisopropylcarbodiimide (i-PrN) 2C yielded the Lewis acid-base adduct LZn(I)-N(i-Pr)CN(i-Pr) 1. In addition, the synthesis of LZnN(SiMe 3) 2 2 and its reaction with (i-PrN) 2C, which occurred with formation of the heteroleptic amidinate-guanidinate complex LZnL′ 3 [L′=(Me 3Si) 2NC(Ni-Pr) 2], is reported. Compounds 1-3 were characterized by nuclear magnetic resonance ( 1H, 13C) and infrared spectro\xadscopy, elemental analysis, and single crystal X-ray diffraction (1 and 2), respectively. © 2012 by Walter de Gruyter Berlin Boston.
    view abstract10.1515/mgmc-2012-0004
  • Synthesis of bismuth pseudocubes by thermal decomposition of Bi 2Et 4
    Schulz, S. and Heimann, S. and Wölper, C. and Assenmacher, W.
    Chemistry of Materials 24 (2012)
    Bismuth pseudocubes were prepared by thermal decomposition of the novel subvalent metal organic precursor tetraethyldibismuthine Bi 2Et 4 under kinetic control at low temperatures. The pseudocubes were characterized by XRD, SEM, HRTEM, EDX, and SAED, and the influence of the thermolysis temperature and of the capping agents NaN(SiMe 3) 2 and PVP* on the size- and shape-selective growth of these nanoparticles was investigated. © 2012 American Chemical Society.
    view abstract10.1021/cm2038377
  • Synthesis of hexagonal Sb 2Te 3 nanoplates by thermal decomposition of the single-source precursor (Et 2Sb) 2Te.
    Schulz, S. and Heimann, S. and Friedrich, J. and Engenhorst, M. and Schierning, G. and Assenmacher, W.
    Chemistry of Materials 24 (2012)
    The size-selective synthesis of hexagonal Sb 2Te 3 nanoplates by thermal decomposition of the single-source precursor bis(diethylstibino)telluride (Et 2Sb) 2Te is described for the first time. The role of the thermolysis temperature and the concentration of the capping agent (PVP*) on the growth of the nanoplates was investigated. The thermal properties of (Et 2Sb) 2Te were investigated by differential scanning calorimetry (DSC), and the resulting Sb 2Te 3 nanoplates were characterized by XRD, SEM, TEM, EDX, and SAED. Moreover, electrical conductivity, Seebeck coefficient and thermal conductivity of the nanoplates were determined, clearly proving the enhanced thermoelectric properties of nanosized antimony telluride. © 2012 American Chemical Society.
    view abstract10.1021/cm301259u
  • Synthesis, reactivity and applications of zinc-zinc bonded complexes
    Li, T. and Schulz, S. and Roesky, P.W.
    Chemical Society Reviews 41 (2012)
    The discovery of decamethyldizincocene [Zn 2(η 5- Cp*) 2] (Cp* = C 5Me 5), the first complex containing a covalent zinc-zinc bond, by Carmona in 2004 initiated the search for this remarkable class of compounds. Low-valent organozinc complexes can either be formed by ligand substitution reactions of [Zn 2(η 5-Cp*) 2] or by reductive coupling reactions of Zn(ii) compounds. To the best of our knowledge, until now 25 low-valent Zn-Zn bonded molecular compounds stabilized by a variety of sterically demanding, very often chelating, organic ligands have been synthesized and characterized. There are two major reaction pathways of [Zn 2(η 5-Cp*) 2]: it can either react with cleavage of the Zn-Zn bond or by ligand substitution. In addition, upon reaction with late transition metal complexes, [Zn 2(η 5-Cp*) 2] was found to form novel intermetallic complexes with Cp*Zn and Cp*Zn 2 acting as unusual one-electron donor ligands. Very recently, the potential capability of [Zn 2(η 5-Cp*) 2] to serve as a suitable catalyst in hydroamination reactions was demonstrated. Finally, the recent work on Cd-Cd bonded coordination compounds is reviewed. © 2012 The Royal Society of Chemistry.
    view abstract10.1039/c2cs15343b
  • Synthesis, structure, tautomerism, and reactivity of methanetrisamidines
    Gutschank, B. and Schulz, S. and Marcinkowski, M. and Jansen, G. and Bandmann, H. and Bläser, D. and Wölper, C.
    Angewandte Chemie - International Edition 51 (2012)
    Tout au contraire: Both tautomeric forms of a methanetrisamidine were structurally characterized for the first time by X-ray diffraction and by ab initio calculations (see structures; gray C, red H, blue N). Their reactivity as proton acceptors and multianionic ligands was demonstrated. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/anie.201205030
  • Aminotroponiminatozinc(I) complexes: Syntheses and spectroscopic analyses
    Nayek, H.P. and Lühl, A. and Schulz, S. and Köppe, R. and Roesky, P.W.
    Chemistry - A European Journal 17 (2011)
    Aminotroponiminates-very effective ligands for the stabilization of low-valent ZnI-ZnI bonded compounds (see scheme). For the first time a stretching motion of the Zn-Zn bond, which is almost uncoupled to other vibrations, was found in the Raman spectrum. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/chem.201002443
  • Base-stabilized monomeric stibinoalane dmap-Al(Et2)Sb( tBu)2
    Schulz, S. and Nieger, M.
    Journal of Chemical Crystallography 41 (2011)
    The six-membered heterocycle [Me2AlSb(t-Bu)2] 3 was reacted with the strong Lewis-base 4-dimethylaminopyridine (dmap), yielding the first completely alkyl-substituted monomeric complex dmap-Al(Me2)Sb(t-Bu)2 1. 1 was characterized by NMR spectroscopy and single crystal X-ray diffraction. 1 is monoclinic, space group P21/n with a = 9.9004(2) Å, b = 16.8166(3) Å, c = 13.8400(3) Å, β = 100.746(1)° and Z = 4. © 2010 Springer Science+Business Media, LLC.
    view abstract10.1007/s10870-010-9886-4
  • Direct carboxylation of zincocene Cp*2Zn
    Schulz, S. and Schmidt, S. and Bläser, D. and Wölper, C.
    European Journal of Inorganic Chemistry (2011)
    The reaction of zincocene Cp*2Zn with CO2 proceeds with the formation of [Zn4(μ4-O)(O 2CCp*)6] (1), which was characterized by NMR ( 1H, 13C) and IR spectroscopy as well as by elemental analysis and single-crystal X-ray diffraction. The solid-state structure of 1 is comparable to that previously observed for basic zinc acetate. In contrast to many previously reported CO2 activation reactions, the formation of 1 occurred without the use of any additional transmetalation catalyst. Zincocene activates CO2 with the formation of [Zn4(μ4- O)(O2CCp*)6] (1), whose structure is comparable to that of basic zinc acetate. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201100715
  • Insertion reactions of heterocumulenes into Zn-C bonds: Synthesis and structural characterization of multinuclear zinc amidate complexes
    Schmidt, S. and Schäper, R. and Schulz, S. and Bläser, D. and Wölper, C.
    Organometallics 30 (2011)
    Reactions of ZnMe2 with isocyanates RNCO proceeded with insertion of the isocyanate into the Zn-Me bond, giving the corresponding heteroleptic amidate complexes [MeZnOC(Me)NR]x (R = i-Pr (1), t-Bu (2)) and [{MeZn}4Zn{OC(Me)NC6F5}6] (3) in high yields. In contrast, ZnCp*2 reacts with isocyanates and isothiocyanates with formation of homoleptic complexes of the type [Zn{OC(Cp*)NR}2]2 (R = Et (4), i-Pr (5)) and [Zn{SC(Cp*)N-i-Pr}2]2 (6). 1-6 were characterized by elemental analyses, multinuclear NMR (1H, 13C, 19F) and IR spectroscopy, and single-crystal X-ray diffraction (1, 2, 5). © 2011 American Chemical Society.
    view abstract10.1021/om101107e
  • Structural characterization of Et4Sb2 and Et 4Bi2
    Kuczkowski, A. and Heimann, S. and Weber, A. and Schulz, S. and Bläser, D. and Wölper, C.
    Organometallics 30 (2011)
    The solid-state structures of Et4Sb2 (1) and Et 4Bi2 (2) were determined by single-crystal X-ray diffraction. Single crystals of 1 and 2 were grown in a closed quartz glass capillary under an inert argon atmosphere on the diffractometer using a specific IR-laser-assisted technique. 1 shows short intermolecular Sb••• Sb interactions, whereas the closest Bi•••Bi distances are longer than the sum of the van der Waals radii. © 2011 American Chemical Society.
    view abstract10.1021/om2005723
  • Syntheses and structures of triazides of heavy group 15 elements
    Schulz, S. and Lyhs, B. and Jansen, G. and Bläser, D. and Wölper, C.
    Chemical Communications 47 (2011)
    Synthesis of group 15-triazides E(N3)3 (E = Sb 1, Bi 2) and Py2-Bi(N3)33 (Py = pyridine). Single crystals of 1 were in situ grown by an IR-laser-assisted technique on the diffractometer. The structure of 3, which represents the first structurally characterized neutral Bi-triazide, is influenced by crystal packing effects according to DFT calculations. © 2011 The Royal Society of Chemistry.
    view abstract10.1039/c1cc10237k
  • Syntheses and X-ray crystal structures of organoantimony diazides
    Lyhs, B. and Bläser, D. and Wölper, C. and Schulz, S.
    Chemistry - A European Journal 17 (2011)
    Antimony(III) complexes of the general type LSbF2 (3: L 1=[tBuC(NiPr)2]; 4: L2=[tBuC(NDipp) 2], Dipp=2,6-iPr2C6H3) and LSb(N3)2 (6: L1; 7: L2) were prepared in high yields and characterized by elemental analyses, NMR and IR spectroscopy and single-crystal X-ray diffraction. Moreover, the solid-state structures of [L2SbF2][L2Li] (5), [L 2AlH2] (1), and [L′H][L′K(thf)3] (2; L′=HC(NDipp)2) are described, in which the Li (5) and K atoms (2) adopt rather unusual coordination modes. Upping the anti(mony): Antimony(III)bisazides LSb(N3)2 (L=amidinate; see figure) were synthesized by treating the corresponding fluorides LSbF2 with Me3SiN3. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/chem.201002730
  • Synthesis and crystal structures of t-Butyl-Pyridine adducts of ZnR 2 (R = Me, i-Pr, t-Bu, Cp*)
    Schulz, S. and Schäper, R. and Krech, D. and Schuchmann, D. and Bläser, D. and Boese, R.
    Zeitschrift fur Anorganische und Allgemeine Chemie 637 (2011)
    Lewis acid-base adducts of the general type R2Zn(4-tBuPy) x (R = Me 1, iPr 2, tBu 3, Cp* 4; x = 1, 2) were obtained in high yields from reactions of ZnR2 with the Lewis base 4-tBu-Pyridine. Compounds 1-4 were characterized by multinuclear NMR ( 1H, 13C) and IR spectroscopy and elemental analyses, 1 and 4 also by X-ray diffraction at single crystals. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/zaac.201000264
  • Synthesis and structural characterization of antimony polyazides
    Lyhs, B. and Jansen, G. and Bläser, D. and Wölper, C. and Schulz, S.
    Chemistry - A European Journal 17 (2011)
    The synthesis of antimony polyazides and structural characterization of the pentaazidoantimonite [Sb(N3)5]2- dianion, which is without precedent in Group 15 polyazide chemistry, is reported (see scheme). © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/chem.201102224
  • Synthesis and X-ray crystal structures of multinuclear zinc amidinate complexes
    Schmidt, S. and Gutschank, B. and Schulz, S. and Bläser, D. and Boese, R. and Wölper, C.
    European Journal of Inorganic Chemistry (2011)
    The reactions of Me2Zn with carbodiimides RN=C=NR (R = Et, Ph) yielded the polynuclear zinc amidinate complexes {[MeZn]4[C(RNCNR) 4]} [R = Et (1), Ph (3)] and {[MeZn]2[C(EtNCNEt) 2(C2(NEt)3)]} (2). In addition, the reaction of {[ClZn]4[C(iPrNCNiPr)4]} with MCl3 gave the corresponding Lewis acid-base adducts {[MCl3]2[ClZn] 4[C(iPrNCNiPr)4]} [M = Al (4), Ga (5)]. Compounds 1-5 were characterized by multinuclear NMR (1H, 13C) and IR spectroscopy, elemental analyses and single-crystal X-ray diffraction. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201100685
  • X-Ray crystal structure of a heterobimetallic Al-Zn-oxide complex
    Schulz, S. and Spielmann, J. and Bläser, D. and Wölper, C.
    Chemical Communications 47 (2011)
    OH/R (R = H, Me, i-Bu) exchange was observed in reactions of [MesnacnacZn(μ-OH)] 2 (1) with metal complexes L nMR, whereas DippnacnacAl(Me)OH reacts with MesnacnacZnH with elimination of H 2 and formation of the heterobimetallic Al-Zn-oxide complex MesnacnacZnOAl(Me)Dippnacnac 2. © 2011 The Royal Society of Chemistry.
    view abstract10.1039/c0cc05599a
  • Base-stabilized dimeric organozinc alkoxides
    Schulz, S. and Flörke, U.
    Journal of Chemical Crystallography 40 (2010)
    Dimeric, base-stabilized organozinc alkoxides [dmap-Zn(R)μ-OR] 2 (R = Et 1; i-Pr 2), were obtained from reactions of ZnR2 and 4-dimethylaminopyridine (dmap) in the presence of O2. Their solid state structures were determined by single crystal X-ray diffraction studies. 1 is triclinic, space group P-1 with a = 8.0639(10) Å, b = 8.3082(11) Å, c = 10.4545(13) Å, α = 70.846(2)°, β = 72.316(2)°, γ = 81.505(2)° and Z = 1. 2 is triclinic, space group P-1 with a = 8.6381(6) Å, b = 9.2773(7) Å, c = 10.2186(7) Å, α = 112.094(1)°, β = 103.040(1)°, γ = 92.598(1)° and Z = 1. Graphical Abstract: Single crystal X-ray analyses of two base-stabilized organozinc alkoxides [dmap-Zn(R)μ-OR]2 (R = Et 1; i-Pr 2), which were obtained from reactions of ZnR2 and 4-dimethylaminopyridine (dmap) in the presence of O2, are described.[Figure not available: see fulltext.] © 2010 Springer Science+Business Media, LLC.
    view abstract10.1007/s10870-010-9843-2
  • Lewis acid-base adduct Me3Sb-Ga(t-Bu)3
    Schulz, S. and Kuczkowski, A. and Nieger, M.
    Journal of Chemical Crystallography 40 (2010)
    The simple Lewis acid-base adduct Me3Sb-Ga(t-Bu)3 1 was prepared by reaction of t-Bu3Ga and SbMe3 in 1:1 M ratio. 1 was fully characterized by multinuclear NMR spectroscopy ( 1H, 13C). In addition, its solid state structure was determined by single crystal X-ray diffraction studies. 1 is monoclinic, space group P21 /n with a = 8.4895(2) Å, b = 12.9303(4) Å, c = 17.9976(5) Å, β = 97.472(2)° and Z = 4. Graphical Abstract: Me3Sb-Ga(t-Bu)3 was synthesized by the reaction of equimolar amounts of the weak Lewis-base Me3Sb and Ga(t-Bu) 3. Me3Sb-Ga(t-Bu)3 represents a rather rare example of a Lewis acid-base adduct of trimethylstibine.[Figure not available: see fulltext.] © 2010 Springer Science+Business Media, LLC.
    view abstract10.1007/s10870-010-9815-6
  • Low-valent organometallics-synthesis, reactivity, and potential applications
    Schulz, S.
    Chemistry - A European Journal 16 (2010)
    General concepts for the synthesis and stabilization of low-valent organometallic complexes of Groups 2, 12, 13, and 15 metals and common structural motifs are described. While kinetically stabilized complexes are in the focus for more than two decades, the principle of base-stabilization only recently allowed the synthesis of unforeseen compounds. As-prepared complexes not only show fascinating structural diversities, but exhibit also very interesting chemical properties. Low-valent complexes are of particular interest in the synthesis of novel molecular complexes, but may also find applications as tailor-made precursors for the synthesis of nanosized materials. © 2010 Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim.
    view abstract10.1002/chem.201000580
  • Novel synthetic pathway for new Zn-Zn-bonded compounds from dizincocene
    Gondzik, S. and Bläser, D. and Wölper, C. and Schulz, S.
    Chemistry - A European Journal 16 (2010)
    Making it new! A novel synthetic pathway for the synthesis of Zn-Zn-bonded complexes (see graphic) under mild reaction conditions is presented. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/chem.201002482
  • Reactions of a β-diketiminate zinc hydride complex with heterocumulenes
    Schulz, S. and Eisenmann, T. and Schmidt, S. and Bläser, D. and Westphal, U. and Boese, R.
    Chemical Communications 46 (2010)
    The β-diketiminate zinc hydride MesnacnacZnH (1) reacts with CO 2, C(Ni-Pr) 2 and t-BuNCO at ambient temperature with insertion into the Zn-H bond and subsequent formation of the corresponding formato (2), formamido (3) and formamidinato (4) complexes. © 2010 The Royal Society of Chemistry.
    view abstract10.1039/c0cc01329c
  • Reactions of dizincocene with sterically demanding bis(iminodi(phenyl) phosphorano)methanes
    Schulz, S. and Gondzik, S. and Schuchmann, D. and Westphal, U. and Dobrzycki, L. and Boese, R. and Harder, S.
    Chemical Communications 46 (2010)
    Reactions of Cp*2Zn2 with sterically demanding bis(iminodi(phenyl)phosphorano)methanes LH (LH = CH2(Ph 2PNR)2 (R = Ph L1H, SiMe3L 2H, 2,6-i-Pr2C6H3 (Dipp) L 3H) at ambient temperature occurred with elimination of Cp*H and subsequent formation of the homoleptic complex L1 2Zn21 and the heteroleptic complexes LZnZnCp* (L = L22, L33, L14). 3 is the first structurally characterized heteroleptic organozinc complex with the zinc atoms in the formal oxidation state +1. © The Royal Society of Chemistry.
    view abstract10.1039/c0cc02859b
  • Self-catalyzed growth of GaSb nanowires at low reaction temperatures
    Schulz, S. and Schwartz, M. and Kuczkowski, A. and Assenmacher, W.
    Journal of Crystal Growth 312 (2010)
    Thermal decomposition of Lewis acid-base adducts [t-Bu 3Ga-Sbi-Pr 3] (1) and [t-Bu 3Ga] 2[Sb 2Et 4] (2) in closed glass ampoules at temperatures between 250 and 350 °C yielded crystalline GaSb nanowires. Isolated GaSb nanowires were formed preferably at low decomposition temperatures, whereas dendritic-like growth was observed at higher decomposition temperatures. In addition, self-catalyzed growth of GaSb nanowires using 90 nm-sized Ga droplets, which were pre-deposited on Si(1 0 0) substrates, was achieved with the distibine Sb 2Et 4 at 250 °C. © 2010 Elsevier B.V. All rights reserved.
    view abstract10.1016/j.jcrysgro.2010.01.026
  • Structural characterization of a completely alkyl-substituted Al-Sb Lewis acid-base adduct
    Schulz, S. and Kuczkowski, A. and Nieger, M. and Saxell, H.
    Journal of Organometallic Chemistry 695 (2010)
    The Lewis acid-base adduct t-Bu3Al-SbMe3 (1), which was synthesized by reaction of equimolar amounts of t-Bu3Al and trimethylstibine SbMe3, was characterized by multinuclear NMR ( 1H, 13C) spectroscopy, elemental analyses as well as by single crystal X-ray diffraction. © 2010 Elsevier B.V.
    view abstract10.1016/j.jorganchem.2010.06.022
  • Synthesis and structural characterization of new zinc amidinate complexes
    Schmidt, S. and Schulz, S. and Bläser, D. and Boese, R. and Bolte, M.
    Organometallics 29 (2010)
    The synthesis and reactivity of heteroleptic zinc complexes of the type LZnX (X = Me, I) containing amidinate ligands L of varying steric bulk were investigated. Complexes of the type LZnMe, which were obtained from the homoleptic complexes L2Zn upon reaction with ZnMe2, react with iodine with subsequent formation of LZnI. Single-crystal X-ray structures of the amidinate zinc complexes [{MeC(Ni-Pr)2}ZnMe]2, 1, [{MeC(Ni-Pr)2}ZnI]2LiI(OEt)2, 3, [t-BuC(NDipp)2]ZnMe, 5, [t-BuC(NDipp)2]ZnMe(t-BuPy), 6, [{t-BuC(NDipp)2}Zn(μ-I)]2, 7, and [t-BuC{N(H)Dipp} 2][Al{OC(CF3)3}4], 8, are reported. © 2010 American Chemical Society.
    view abstract10.1021/om1008549
  • Synthesis and x-ray crystal structures of tetranuclear zincamidinate complexes
    Gutschank, B. and Schulz, S. and Westphal, U. and Bläser, D. and Boese, R.
    Organometallics 29 (2010)
    Polynuclear amidinate zinc halide complexes of the general type{C[C(Ni-Pr)2ZnX]4} [X = Cl, 2; Br, 3; I, 4] were prepared in high yields via methyl/halide exchange reaction of {C[C(Ni-Pr) 2ZnMe]4} (1a) with AlX3. 2-4 were characterized by elemental analysis, multinuclear NMR, and IR spectroscopy and single-crystal X-ray diffraction. Computational calculations of halide-substituted complexes {C[C(Ni-Pr)2ZnX]4} [X = F-I] were performed to clarify the influence of the halide atom on the structural parameters of the complexes and to elucidate their electronic structure and bonding situation. The capability of these halide-substituted complexes to serve as suitable starting reagents for further salt elimination reactions was proven by reaction of 2 with LiR (R = Me, n-Bu) and EtMgBr, which yielded the corresponding Zn-alkyl species {C[C(Ni-Pr)2ZnR]4} [R = Me, 1a; n-Bu, 5; Et, 6]. © 2010 American Chemical Society.
    view abstract10.1021/om100065w
  • Synthesis, structure, and reactivity of a tetranuclear amidinato zinc hydride complex
    Gutschank, B. and Schulz, S. and Bläser, D. and Boese, R. and Wölper, C.
    Organometallics 29 (2010)
    The tetranuclear amidinato zinc hydride complex (C[C(Ni-Pr) 2ZnH]4) (3) was synthesized by reaction of the Cl-substituted complex (C[C(Ni-Pr)2ZnCl]4) with CaH 2. 3 was found to react with phenylacetylene and acetylene at ambient temperature with elimination of H2 and subsequent formation of C[C(Ni-Pr)2ZnC≡CPh]4 (4) and (C[C(Ni-Pr) 2ZnC≡CH]4 (5), respectively. 3-5 have been characterized by multinuclear NMR (1H, 13C) and IR spectroscopy, elemental analyses, and single-crystal X-ray diffraction. © 2010 American Chemical Society.
    view abstract10.1021/om100966d
  • MOCVD process

  • nanoparticles

  • photonics

  • semiconductors

  • synthesis

  • thin films

  • x-ray diffraction

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