Preparation, structure and reactivity of polynuclear gold(I) phosphanyl alkanethiolates

The homoleptic gold(l) thiolates of formula [Au(SR)](n) (R = CMe3, CH2CMe3, CH2CHMe2, CPh3) have been converted into their phosphane derivatives of general formula [Au(SR)(L)] (L = PMe3, PMe2Ph, PMePh2, PPh3) and [Au-2(SR)(2)(dppe)] [dppe 1, 2-bis (diphenylphosphanyl) ethane], which have been characterized by elemental analysis, mass spectrometry, H-1 and P-31 NMR spectroscopy and cyclic voltarnmetry. Complexes [Au(SCMe3)(PMePh2)] (1c), [Au-2(SCMe3)2(dppe)] (1e) and [Au(SCH2CMe3)(PPh3)] (3d) have been characterized in the solid state by X-ray diffraction: no aurophilic interactions have been found. The electrochemical behaviour of these phosphane thiolato derivatives shows two irreversible oxidation processes, the first of which involves 0.5 electrons per Au-SR. Chemical oxidation by [FeCP2]BF4 produces disulfide and cationic gold(l) complexes of formula [Au-2(SR)(L)(2)][BF4] and [Au-2(SR)(dppe)][BF4], characterized by elemental analysis, mass spectrometry and H-1 and (31)p NMR spectroscopy. All the complexes are presumably dimeric in the solid state as shown in the case of [BF4(SCMe3)(2)(dppe)(2)][BF4](2) (5e) and [Au-4(SCH2CMe3)(2)(PMe3)(4)][BF4](2) (7a), which have been fully characterized by X-ray diffraction. The aurophilic interactions form a structure of four gold atoms with pairs of atoms bonded by bridging thiolato ligands, which are arranged in an almost perfect square in the case of 7a and in an unprecedented zigzag sequence in the case of 5e. Complex 4a reacts with HSCMe3 under basic conditions to give [Au(SCMe3)(PMe3)] and with LiX (X = Me, CH2CMe3) to give a 1:1 mixture of [AuX(PMe3)] and [Au(SCMe3)(PMe3)]. (c) Wiley-VCH Verlag GmbH & Co. KGaA.