Gold complexes derived from diphenyl-2-styrylphosphine

Abstract

Complexes of diphenyl-2-styrylphosphine (sp) with gold, first reported in 1971, have been reinvestigated. [AuX(sp)] can be oxidised with X₂ for X = Cl or Br but not for X = I. The initial product, [AuX₃(sp)], undergoes a reversible rearrangement in which an Au–X bond adds across the styryl double bond to give [AuX₂(sp-X)] (sp-X = 2-CH(CH₂X)C₆H₄PPh₂). The carbon-bound halide can be replaced by methoxy by reaction with methanol. [AuX₂(sp-Y)] (X = Cl or Br; Y = Cl, Br or OMe) react with iodide to give eventual reduction to [AuI(sp)], confirming that non-chelated [AuX₂(Y)(sp)] is unstable when X = I. Reduction reactions of this type complicate attempts to study halide-substitution reactions of [AuX₂(sp-Y)], but a variety of substituted products have been identified (e.g. those in which X = OAc CN, SCN, ½SCH₂CH₂NH₂ or ½S₂CNEt₂). Monosubstitution has been achieved with PPh₂R (R = Me or Ph). The crystal structure of [Au(SCH₂CH₂NH₂)(sp-OMe)]PF₆ has been determined; in it and all other substituted products the softer, incoming ligand is trans to phosphorus.