Photoinduced C–C bond formation from alkyl halides catalysed by luminescent dinuclear gold(I) and copper(I) complexes
The photoluminescent properties of [Au2(µ-dppm)2]2+[dppm = bis(diphenylphosphino)methane], [Au2(µ-dmpm)3]2+[dmpm = bis(dimethylphosphino)methane] and [Cu2(µ-dppm)2(MeCN)4]2+ have been investigated. Irradiation of a degassed acetonitrile solution of benzyl chloride or 1-bromopentane in the presence of a sacrificial electron donor such as triethylamine and a catalytic amount of [Au2(µ-dppm)2]2+ led to the formation of bibenzyl or n-decane. Similar photoreactions with much lower yields of the C–C bond coupling products have also been observed with [Au2(µ-dmpm)3]2+ and [Cu2(µ-dppm)2(MeCN)4]2+ as catalysts. The mechanism of the photoreaction between alkyl halides and [Au2(µ-dppm)2]2+ has been investigated by steady-state photolysis, Stern–Volmer quenching and flash-photolysis studies.