Preparation and ligand-exchange reactions of phosphinegold ethynyl complexes

Abstract

Phosphinegold chlorides, [AuCIL], react readily with terminal alkynes RCCH in ethanolic sodium ethoxide to produce high yields of ethynyl complexes [Au(CCR) L][L = PPh₃; R = Me, Et, Ph, or CF₃: L = P(C₆H₄Me-p)₃, R = Ph]. When R = H a second reaction leads to formation of [LAuCCAuL][L = PPh₃, P(C₆H₄Me-p)₃, or P(C₆H₄OMe-p)₃]. In a similar manner, the cyclopentadienyl complex [Au(C₅H₅)(PPh₃)] can conveniently be made from [AuCl(PPh₃)], Na(OEt), and C₅H₆. The phosphine of [Au(CCPh)L] rapidly exchanges in solution with free phosphines. The compounds [Au(CCPh)(PPh₃)] and [AuCl{P(C₆H₄Me-p)₃}] readily equilibrate with [AuCl(PPh₃)] and [Au(CCPh){P(C₆H₄Me-p)₃}], a reaction which could also involve exchange of phosphines, but the exchange of Cl for CCPh is another possible pathway. Phenylethynyl groups from [Au(CCPh)(PPh₃)] exchange with both chlorides of HgCl₂, cis-[PtCl₂(PMePh₂)₂], and cis-[PtCl₂(CO)(PMePh₂)]. With the latter complex the exchange is non-stereospecific, unlike related reactions with organomercurials.