Gold(I) dimethyl- and diphenyl-dithiophosphinate complexes

In an attempt to carry out polyauration of dithiophosphinate units, diphenyldithiophosphinic acid, Ph₂P(S)SH, was treated with the reagents {[(R′₃P)Au]₃O}⁺BF₄^- to give compounds {Ph₂P[SAu(PR′₃)]₂}⁺BF ₄^- with R′ = Ph, Me or o-tolyl (o-Tol) (1-3). The symmetrical Au ⋯ Au bonded structure of complex 1 was confirmed by a single-crystal X-ray diffraction study. Intercationic contacts are found only between gold and sulfur atoms. The analogous reaction with PhP(S)(SSiMe₃)₂ gave an unstable product of the composition {PhP[SAu(PPh₃)]₃}⁺BF₄^- 4, for which a solution structure with mirror-symmetry is proposed on the basis of low-temperature NMR data. Attempts to polyaurate dimethyldithiophosphinic acid led to cleavage of the P-S bonds with formation of known trigold sulfonium salts. (Phosphine)gold(I) dithiophosphinates Me₂P(S)SAu(PR′₃) were obtained from Me₂P(S)SNa and chloro(phosphine)gold complexes (R′ = Me, Ph or o-Tol, 5-7 respectively). The crystal and molecular structure of compound 5 was determined. In the crystal, the compound forms two crystallographically independent, centrosymmetrical dimers with Au ⋯ Au contacts [3.1152(5) and 3.1466(5) Å] between 'crossed' monomers. With (Me₂S)AuCl as a precursor, the product of the reaction with Me₂P(S)SNa was [Me₂P(S)SAu]₂ 8. Compound 8 is a dinuclear complex with an elongated eight-membered ring structure in a chair conformation. The crystal-structure analysis reveals the expected transannular Au ⋯ Au contacts [3.1949(9) Å], but no intermolecular contacts are discernible.