A route to trinuclear platinum–gold clusters

Abstract

New A-frame cluster complexes have been prepared by addition of electrophilic gold fragments to the Pt—Pt bond of [Pt2Cl2(μ-ppm)2], dppm = Ph2PCH2PPh2. For example, [AuCl(SMe2)] gave [Pt2Cl2((μ-AuCl)((μ-dppm)2] and [Au(NO3) (PPh3)] gave [Pt2Cl2(μ-AuPPh3)(μ-dppm)2]NO3. The complexes [(CH2)n(PPh2AuBF4)2] reacted with [Pt2Cl2(μ-dppm)2] to give [Pt2Cl2(μ-AuPPh2(CH2)nPPh2AuCl)(μ-dppm)2]BF4 when n = 1 or 2, but the bridged bis(A-frame) cluster complex [{Pt2Cl2(μ-dppm)2(μ-AuPPh2CH2)}2CH2](BF4)2 when n = 3. In contrast, CuCl reacted with [Pt2Cl2(μ-dppm)2] to give [Pt2Cl(CuCl2)(μ-dppm)2]. Attempts to synthesize A-frame clusters containing Pt2Ag, Pt2Cu, Pd2Au, or PdPtAu units were unsuccessful, and it is concluded that these units are considerably weaker than the analogous 3-center 2-electron bond of the Pt2Au unit. The AuCl unit is displaced from [Pt2Cl2(μ-AuCl)(μ-dppm)2] on reaction with diazomethane, with formation of [Pt2Cl2(μ-CH2)(μ-dppm)2]. Keywords: platinum, gold, cluster, copper, silver.