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  • Author: Hubert Schmidbaur x
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The phosphonic acid anhydrides of the general formula [RPO2]n have been prepared with R = Me, Et, i-Pr, t-Bu, and Ph from the corresponding phosphonic acids and their chlorides and esters. Mass spectrometric data indicate that the trimers are the dominant oligomers for all five systems. According to their NMR spectra, the methyl and t-butyl compounds have a symmetrical (C3v) structure with equivalent RP groups, while the ethyl, i-propyl and phenyl homologues have the Cs structure with non-equivalent PR groups in the ratio 1:2.

The reaction of tris[(tri-tbutyl-phosphine)gold(I)]oxonium tetrafluoroborate with close to stoichiometric quantities of ammonia in dichloromethane at -78 °C affords tetrakis[(tri- tbutyl-phosphine)gold(I)]ammonium tetrafluoroborate, the structure of which has been determined by single crystal X-ray diffraction. The cation features a strongly distorted NAu4 tetrahedron with four short and two longer Au -Au edges. - With a large excess of ammonia, only partially aurated ammonium salts are formed, as suggested by detailed NMR spectroscopic and mass spectrometric studies. These partially aurated intermediates have not been isolated. Slow decomposition processes in these solutions lead to the precipitation of bis(tri- tbutyl-phosphine)gold(I) tetrafluoroborate. The structure of the bis(chloroform) solvate has also been determined. The crystals contain two independent C3-symmetrical cations with similar structures.

Abstract

The reaction of HAuCl4 or AuCl3 with Sn(CH3)4 in methanol at low temperatures gives [(CH3)2AuCl]2 in yields from 40 to 45%.

Dimethylsulfide reacts with (triphenylphosphine) gold(I) trifluoromethanesulfonate to give quantitative yields of the mixed ligand complex [(Ph3P)Au(SMe2)]+O3SCF3 - (1). The structure of compound 1 has been determined by an X-ray crystal structure analysis. The lattice contains independent anions and (monomeric) cations, which have a linear P-Au-S axis. Attempts to produce a binuclear. dicationic complex through addition of a second equivalent of [(Ph3P)Au]+ failed and lead to decomposition products including [(Ph3P)2Au]+O3SCF3 -.

Abstract

Tris[(triphenylphosphine)gold(I)]telluronium tetrafluoroborate (1) was prepared from the corresponding oxonium salt and bis(t-butyldimethylsilyl)tellurium in dichloromethane at -78°C. The product forms yellow crystals, thermally stable to 125°C. It was identified by standard analytical and spectroscopic techniques, including a single crystal X-ray diffraction study. In the crystal lattice, the cations form tellurium-capped triangles of gold, which are associated into dimers through short intermolecular Au -Au contacts, resembling those in the corresponding sulfur and selenium compounds. - The reaction of (t-BuMe2Si)2Te with four equivalents of [(Ph3P)Au]BF4 in tetrahydrofuran at -78°C gives a tetranuclear compound, {[(Ph3P)Au]4Te}2+ 2 BF4 - (2) which differs from 1 in its analytical and spectroscopic data. Its structure could not be determined, but it is assumed that the dications have a square pyramidal geometry

The composition of aqueous fluoroberyllate solutions has been studied by 9Be and 19F NMR spectroscopy for various ratios of the beryllium and fluorine concentrations, and at different pH values. The equilibrium constants have been determined for the ligand exchange processes, which involve the species [Be(OH2)4]2+, [BeF(OH2)3]+, [BeF2(OH2)2], [BeF3(OH2)]- , and [BeF4]2-. These equilibria are shifted towards [BeF4]2- at high pH. No polynuclear fluoroberyllates have been detected. The fluoride exchange between the individual species is slow on the NMR time scale at room temperature, and separate sharp signals with the expected multiplicity are therefore recorded. Calculated 9Be chemical shifts are in good agreement with experimental data.

Abstract

The reaction of 1,4-dibromobutane with bis(diphenylphospliino)methane (1) yields two products, one of which is identified as butane-1,4-bis[diphenyl(diphenylphosphinomethyl)-phosphonium bromide] (3 a). Transylidation of this bis-phosphonium salt using two equiv-alents of (CH3)3P = CH2 affords the bis-ylide [CH2CH2P(C6H5)2 = CH-P(C6H5)2]2 (4) in high yields. This conversion can be reversed on treatment of 4 with etheral HCl (to give 3b). Methylation of 4 with CH3I occurs at phosphorus, however, and produces the bis-semiylide salt (5), [CH2CH2P(C6H5)2CHP(C6H5)2CH3]2 2⊕ 2I⊖. Transylidation of 5 (again with (CH3)3P = CH2) leads to the bis-carbodiphosphorane (6), [CH2CH2P(C6H5)2 = C = P(C6H5)2CH3]2. All compounds were characterized by elemental and detailed NMR analyses. The second product of the above quaternisation reaction is a cyclic bis-phosphonium salt (2) with a seven-membered ring structure.

Abstract

Treatment of tris[(triphenylphosphine)gold(I)]-sulfonium tetrafluoroborate with AgBF4 (molar ratio 2:1) in tetrahydrofuran affords a hepta-nuclear mixed-metal cluster trication {[(Ph3P)6Au6AgS2](thf)}3+ as the tetrafluorobor­ate salt. The crystal structure of the compound has been determined by X-ray diffraction. The sil­ver atom is found in a bridging position between the two Au3S units with short contacts to both sulfur atoms and to three out of six gold atoms. The coordination sphere of the silver atom is complemented by a tetrahydrofuran molecule. In di(tri)chlorom ethane solutions there is rapid site exchange of the silver coordination as shown by virtual equivalence of the phosphine ligands on the NMR time scale at ambient temperature.

Abstract

A new and efficient synthetic route to di- and tri(silyl)methane is presented. Starting from bis- and tris(phenylsilyl)methane, bis- and tris(trifluoromethanesulfonatosilyl)methane can be obtained by Si-Ph cleavage with equivalent quantities of trifluoromethanesulfonic acid (triflic acid). Their reduction with lithium aluminium hydride yields di- and tri(silyl)methane. Substitution of the previously employed liquid anhydrous hydrogen bromide by triflic acid thus offers an experimentally more simple alternative with shorter reaction times and high selectivity.

Tris(dimethylstibino)amine N(SbMe2)3 is formed during reactions of sodium dimethylstibide with haloalkanes in liquid ammonia. It forms colourless monoclinic crystals, a = 12.108(1), b = 6.663(1), c = 16.891(2) Å, β = 10 1 .1 2 (1)°, P21/c, Z = 4, at -78 °C. The lattice contains independent molecules with a planar NSb3 core (sum of the angles at nitrogen 359.9°) and approximate C3h symmetry.