(Phosphine)gold(I) trifluoromethanesulfonates, trifluoroacetates and trichlorothioacetates†

Abstract

Stable, crystalline (phosphine)gold(I) trifluoroacetates of the type (R₃P)AuOC(O)CF₃ have been prepared in high yield from the corresponding chloro complexes with AgOC(O)CF₃ in tetrahydrofuran for R = Me, Ph or o-Tol. The crystal structure of (Me₃P)AuOC(O)CF₃ features trimers with two short aurophilic Au· · ·Au contacts in an angular Au· · ·Au· · ·Au unit. Trichlorothioacetic acid has been aurated (in high yield) using {[(R₃P)Au]₃O}⁺BF₄^– and NaBF₄ in dichloromethane to give equally stable compounds (R₃P)AuSC(O)CCl₃ with R = Me, Ph or o-Tol. In these products the trichlorothioacetate group is exclusively sulfur bonded to the gold atom. The methyl and o-tolyl compounds are dimers in the solid state, but association is based on only very long intermolecular Au· · ·S and Au· · ·Cl contacts, respectively. (Triphenylphosphine)gold thioacetate was prepared similarly, but the product is thermally unstable in both the solid and solution state. It thus appears that the presence of the halogen substituents is essential for the stability of the present compounds, which are useful aurating agents and can be employed for the controlled deposition of gold. [Tri(o-tolyl)phosphine]gold chloride was converted into the trifluoromethanesulfonate (triflate) in 95% yield by treatment with AgOS(O)₂CF₃ in tetrahydrofuran. The crystal structure determination of the CH₂Cl₂ solvate revealed non-ionic, molecular components [Au–O 2.110(3) Å, S–O–Au 120.4(2)°], which are associated into dimers via hydrogen bonds [O· · ·H–C 170.2°, C–H 0.969 Å, H· · ·O 2.575 Å] with two CH₂Cl₂ molecules.