Mechanism of photocatalysed coupling reaction from benzyl chloride by Au( I )-phosphine bridge complex

Abstract

With laser flash-photolysis, UV-visible absorption spectroscopy and transient absorption spectroscopy techniques, the quenching rates of excited state of [Au2-(μ-dmpm)3](ClO4)2 by alkyl halides were measured, the steady-state photoreaction of [Au2(μ-dmpm)3](ClO4)2 and CHCl3 was investigated, respectively. The mechanism of C-C coupling reaction from benzyl chloride with Au ( I )-phosphine bridge complex as photocatalyst was explored. It was found that [Au2(μ-dmpm)3](ClO4)2 lost a dmpm ligand easily to give [Au2(μ-dmpm)2](ClO4)2, the latter played the key role in the photocatalytic reaction. Bibenzyl was produced by the combination of two benzyl radicals or by the nucleophilic reaction of benzyl anion and benzyl chloride.