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  • X-ray structures  (4)
  • Hydroboration  (3)
  • Platinum  (3)
  • Ab initio calculations  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Contributions to the Chemistry of Boron, 227Part 226: Ref.. The P-centered Chemistry of [(Di-tert-butylphosphanyl)imino]-(2,2,6,6-tetramethylpiperidino)boraneDedicated to Professor Helmut Werner on the occasion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 205-212 
    Details
    ISSN: 0009-2940
    Keywords: Borane, [(di-tert-butylphosphanyl)imino](2,2,6,6-tetramethylpiperidino) dimer ; Phosphonium, di-tert-butylmethyl[(2,2,6,6-tetramethylpiperidinoborylene)imino]iodide ; Haloboration ; Hydroboration ; Metal carbonyl complexes of [(di-tert-butylphosphanyl)imino](2,2,6,6-tetramethylpiperidino)borane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The elements oxygen, sulfur, and selenium add to the P atom of the title borane 1. In contrast to the formation of tmp—B≡N—P(X)tBu2 (X = S, Se), the P oxide (X = O) dimerizes to [tmp—B≡N—P(O)tBu2]2 (5) with an eight-membered flat boat-shaped B2N2P2O2 ring. Borane 1 reacts readily with Mel to yield a phosphonium salt 8 and with BBr3 to give an adduct 9 with a B—P bond. In contrast, bis(dichloroboryl)-methane not only adds to 1 to generate a coordinate B—P bond but also chloroborates the B≡N triple bond, the final product being a new five-membered heterocycle 10. Similarly, the BH3 component of BH3·SMe2 first adds to the P atom of 1 followed by reaction of a second mol of BH3·SMe2 which hydroborates the B≡N triple bond. Finally, metal carbonyl fragments add only to the P atom of 1, demonstrating also that the chemistry of the molecule 1 is dominated by the basicity of its P center.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280302
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  • 2
    Electronic Resource
    Electronic Resource
    Beiträge zur Chemie des Bors, 213. Reaktionen eines Amino-imino-borans mit Triboran(7) und Decaboran(14)Herrn Professor Wolfgang Beck zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2691-2699 
    Details
    ISSN: 0009-2940
    Keywords: Hydroboration ; Tetraborane(8) ; μ-(tert-butylimino)-μ-(tetramethylpiperidino)- ; arachno-Undecaboranates(13), 11-(organylamino)-11-(tetramethylpiperidinio)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contributions to the Chemistry of Boron, 213[1]. - Reactions of an Amino-imino-borane with Triborane(7) and Decaborane(14)Triborane(7)-THF hydroborates (tert-butylimino)(tetramethylpiperidino)borane 1 slowly to form μ-(tert-butylamino)-μ-(tetramethylpiperidino)tetraborane(8) 5. This molecule shows fluxional behaviour at ambient temperature in solution. In the solid state, an X-ray structure analysis reveals the presence of the asymmetric 1104-styx valence tautomer. 1 does not react at ambient temperature with pentaborane(9) in dichloromethane/hexane solution. However, 1 reacts rapidly with decaborane(14) to produce a tetramethylpiperidine adduct of an 11-(tert-butylamino)undecaborane(14) as determined by an X-ray structure analysis. The same kind of reaction occurs between decaborane(14) and (2,6-diisopropylphenylimino)-(2,2,6,6-tetramethylpiperidino)borane. Thus, decaborane(14) acts as a diprotic acid towards amino-imino-boranes.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921251212
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  • 3
    Electronic Resource
    Electronic Resource
    A Deceiving X-ray Single-Crystal Structure Determination: Amino-Hydrogen Exchange in Amino-alkynylboranes and ab initio Investigations of Alkynylboranes, Borirenes, and Boraallenes (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 711-717 
    Details
    ISSN: 0009-2940
    Keywords: Alkynylboranes ; Borirenes ; Boraallenes ; Calculations, ab initio ; Hydroboration ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dimeric(dimethylamino)(phenylethynyl)borane (2)2 is formed by the reaction of bis(dimethylamino)(phenylethynyl)-borane (1) with 9-BBN-H. An X-ray single-crystal diffraction study revealed a central B2N2 four-membered ring for (2)2 with both alkynyl groups pointing to the same side in a cisoid arrangement. However, solution and solid-state NMR as well as ab initio calculations on model compounds show that the cis arrangement in the crystal chosen for X-ray diffraction is not representative of the bulk material, which consists of both cis and trans isomers. Further investigations of the competition between hydrogen-amino group exchange and hydroboration in the reaction of amino-alkynylboranes with hydroborating agents (9-BBN-H and catB-H) show the exchange to be much faster even in the presence of Wilkinson's catalyst and with cyclic amino-alkynylboranes such as 1,3-dimethyl-2-[(trimethylsily1)ethynyl]-1,3,2-diazaborolidine (3). Ab initio calculations on alkynylboranes I, borirenes II, and boraallenes III, which are all geometrical isomers, show alkynylboranes to be the most stable isomers only if strongly π-donating groups X (X = NH2, F) are attached to the boron atom. In any case, boraallenes are highest in energy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280709
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and Structures of Magnesium TetrahydridoaluminatesDedicated to Dr. R. Bauer, who first synthesized magnesium tetrahydridoaluminate, on the occasion of his 70th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 999-1006 
    Details
    ISSN: 0009-2940
    Keywords: Magnesium tetrahydridoaluminate ; Magnesium halide tetrahydridoaluminate ; (Organyloxo)magnesium tetrahydridoaluminates ; X-ray structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular structures of XMg(A1H4) · 4 THF (1a, 2, 3a) (X = A1H4, Cl, Br) have been determined by X-ray structural analysis. Each compound possesses a hexacoordinated Mg center and AlH4- groups bound to this center via a single hydride bridge bond. Attempts to prepare ROMg(AlH4) compounds were successful only for sterically demanding groups R (R = CMe3, CPh3, naph, mes, smes). The 2-naphthoxy derivative 7, a compound with the composition (naphO)Mg-(AlH4) · 2.5 THF, is a dimer with a central Mg2O2 ring. One of its two AlH4- groups is terminally bound to one Mg atom, the other bridges the two Mg centers. This structure indicates how AlH4- transfer may occur from ROMg(AlH4) compounds to form Mg(OR)2 and Mg(AlH4)2.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281007
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  • 5
    Electronic Resource
    Electronic Resource
    Bis(tetramethylpiperidino)aluminum Halide Adducts tmp2AlX · Do and Tetrahaloaluminates of Tricoordinated Aluminum Cations [tmp2Al(Do)]AlX4 (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 927-939 
    Details
    ISSN: 1434-1948
    Keywords: Bis(tetramethylpiperidino)aluminum halide complexes ; Tricoordinated aluminum cations ; 27Al-NMR spectroscopy ; X-ray crystal structure analysis ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Upon treatment with Lewis bases Do (Do = pyridine bases or THF), the Lewis acids tmp2AlX (X = Cl, Br, I) are converted exclusively to the monoadducts tmp2AlX · Do (2-4). The Al-X bonds of these addition compounds are considerably elongated, indicating a tendency towards the formation of ionic species [tmp2Al(Do)]X. Due to the steric requirements of the bulky tmp ligands, addition of an excess of the Lewis base does not force these compounds to form tetracoordinated aluminum cations [tmp2Al(Do)2]+ or pentacoordinated adducts tmp2AlX · Do2. Attempts to prepare ionic representatives by reaction of tmp2AlX · Do with “ate” complexes of comparatively low nucleophilicity [MY = NaBPh4, AgBPh4, LiB(C6F5)4, AgBF4, AgOtos] result in phenylation products [e.g. tmp2AlPh (5a) and BPh3 · py (5b)] or tetracoordinated addition compounds tmp2AlY · Do (Y = anion). However, addition of one equivalent of AlX3 (X = Br, I) initiates halide abstraction with formation of the ionic [tmp2Al(Do)]AlX4 species 6a-f, as indicated by 27Al-NMR data and conductivity measurements. Solid [tmp2Al(py)]AlI4 (6b) decomposes readily into tmpAII2 and tmpAlI2 · py (7c). Addition of non-polar aliphatic solvents to solutions of [tmp2Al(Do)]AlX4 (6) leads to slow decomposition into tmp2AlX and AlX3 · Do (7a-b, d). This also occurs in polar donor solvents, where compounds AlX3 · Do are favoured due to the formation of penta- or hexacoordinated species AlX3 · Do · Solvn (n = 1, 2). Semiempirical AM1 calculations reveal the gas-phase stability of the tricoordinated bis(tmp)aluminum cation in the salt [tmp2AlPy]AlCl4 as the only representative in a series of calculated aluminum cations [(R2N)2AlPy]AlCl4 (R2N = Me2N, Et2N, iPr2N, tmp). According to these calculations, the stability of a given cation increases when tetrachloroaluminate is replaced by tetraiodoaluminate. Ab initio calculations have been performed on two cations [(H2N)2Al(Do)]+ (Do = NH3, py) and indicate very short Al-N bond lengths owing to ionic bonding contributions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Metal Complexes of Alkyne-Bridged α-Amino Acids (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1791-1798 
    Details
    ISSN: 1434-1948
    Keywords: p-Ethynylphenylalanine ; Alkyne-bridged α-amino acids ; N,O-Chelate complexes ; Ferrocenes ; Schiff bases ; Platinum ; Gold ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The palladium-mediated coupling of p-ethynylphenylalanine (p-epa) with different halogenated benzenes yielded alkyne-bridged α-amino acids. A series of cationic mono- to hexanuclear (Ph3P)2Pt complexes with the anions of p-ethynylphenylalanine and alkynyl- or benzene-bridged di-, tri-, tetra- and hexa-ethynyl phenylalanines as N,O-chelate ligands was prepared. N-t-Boc-p-ethynylphenylalanine methyl ester was metal-substituted to give complexes of the types Ph3PAu-C≡C-R and (Et3P)2Pt(C≡CR)2. The benzene-bridged di-, tri-, tetra- and hexa-p-ethynylphenylalanine methyl esters form Schiff bases with ferrocene aldehyde and a tripodal ligand was obtained from Ph2PCH2CH2CH2NH2 and the benzene-bridged tri-ethynylphenylalanine. The structure of (Ph3P)2Pt[NH2C(H)(CH2C6H4C≡CH)CO2]+ BF4- was determined by X-ray diffraction.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxidative Addition of α-Bromoglycine to Palladium(0) and Platinum(0) Complexes: α-Metallated Amino Acids as Models for Intermediates in the Metal-Catalyzed Hydrogenation of Dehydroamino Acids (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 375-379 
    Details
    ISSN: 1434-1948
    Keywords: α-Metallated amino acids ; Palladium ; Platinum ; Oxidative addition ; α-Bromoglycinate ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidative addition of methyl N-benzoyl-2-bromoglycinate to bis(dibenzylideneacetone)palladium, in the presence of 2,2′-bipyridyl, and to (Ph3P)2Pt(η2-C2H4) gives the α-metallated glycine esters 1a and 2a. Abstraction of bromide from 1a, 2a, using AgSbF6 or AgBF4, affords the cationic C,O-chelate complexes [(bpy)Pd-CH(CO2Me)NHC(Ph)O]+ (1b,c) and [(Ph3P)2Pt-CH(CO2Me)NHC(Ph)O]+ (2b), respectively, featuring coordination of the amide O atom. The complexes 1b and 2b have been characterized by X-ray diffraction.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Magnesiation of Triisopropylsilylphosphane: Synthesis and Structures of New Mg2nP2m Polyhedra (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2215-2220 
    Details
    ISSN: 1434-1948
    Keywords: Magnesium ; Metalation ; Phosphorus ; Polyhedra ; X-ray structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The magnesiation of triisopropylsilylphosphane with dibutylmagnesium in toluene yields the octanuclear complex [Mg8(PSiiPr3)6{P(H)SiiPr3}4] (1) which consists of MgPSiiPr3 units forming a hexagonal Mg6P6 prism, with two opposite Mg2P2 moieties capped by additional Mg[P(H)SiiPr3]2 groups. If a small amount of THF is present during the metalation reaction [(THF)4Mg6(PSiiPr3)6] (2) also containing a hexagonal Mg6P6 prism can be isolated. The magnesiation of H2P-SiiPr3 in tetrahydrofuran leads to the formation of the tetrameric complex [(THF)MgPSiiPr3]4(3) with a slightly distorted Mg4P4 cubane-like structure.The structures depend strongly on the steric strain caused by the trialkylsilyl substituents and the neutral coligands at the magnesium center. The highest steric strain, which is induced by coordination to every magnesium atom, leads to the smallest MgnPn polyhedron - the central Mg4P4 heterocubane moiety. In compounds 1 and 2 the hexagonal Mg6P6 prism is formed, however, with reduced steric strain as observed for 2 where the Mg-P bond lengths become more similar.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    The Molecular Structure of Some Transition-Metal Complexes with 1,2,3,4-Tetrazole-5-thiolate Anions (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 93-99 
    Details
    ISSN: 1434-1948
    Keywords: 2-Methyl-1,2,3,4-tetrazole-5-thiolates ; 2-Phenyl-1,2,3,4-tetrazole-5-thiolates ; Palladium ; Platinum ; Copper ; Silver ; Gold ; Molecular structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular structures of nine transition metal tetrazolethiolates have been determined by X-ray structure determinations. The ligand is invariably coordinated through its sulfur atom to the metal center [M = PdII, CuI, AgI, AuI, AuIII, and Hg]. The M-S-C bond angles vary considerably, but this cannot be correlated with variations in the C-S bond lengths. Intermolecular association occurs for Ph3PAu(SCN4Me) via Au-S contacts, leading to dimeric strands in the solid state. The copper compound (Ph3P)3Cu4(SCN4Me)4 (5), possesses a rather asymmetric structure: one Cu atom is tricoordinated by 3 sulfur atoms, the other three are tetracoordinated by P and N as well as by S atoms.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    The Aluminum-Nitrogen Bond in Monomeric Bis(amino)alanes: A Systematic Experimental Study of Bis(tetramethylpiperidino)alanes and Quantum Mechanical Calculations on the Model System (H2N)2AlY (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1095-1114 
    Details
    ISSN: 1434-1948
    Keywords: Aminoalanes ; Alanes ; Ab initio calculations ; 27Al-NMR spectroscopy ; Structure elucidation ; Substituent effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of metallated nucleophiles MIY [Y = OR, SR, NR2, PR2, AsR2, CR3, Si(SiMe3)3, R = organyl, H] with bis(2,2,6,6-tetramethylpiperidino)aluminum halides [tmp2AlX, (X = Cl, Br, I)] offer facile access to a variety of bis(amino)alanes of the type tmp2AlY. As indicated by 27Al-NMR spectroscopy, mass spectrometry and X-ray crystal structure determina-tions, all of these compounds are monomeric in the solid state, in solution, and in the gas phase. Even Al-E single bonds (E = Si, P, As etc.) that are not commonly encountered are stabilized by the supporting tmp fragments. The results of a systematic analysis of the bonding parameters determined for the tmp2AlY compounds, combined with a quantum mechanical study on model compounds (H2N)2AlY, not only reveal the presence of a highly polar Al-N bond, but at the same time rule out AlN-pp(π) bonding, in contrast to the situation in the analogous tmp2BY compounds. It is shown that the Al-N bond length depends on the acidic character of the protic species HY: the shorter d(Al-N), the less basic is Y.
    Type of Medium: Electronic Resource
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