Reversible Cu–S Motif Transformation and Au4 Distortion via Thiol Ligand Exchange Engineering

The thiol ligand-induced structural change is a good strategy to construct new metal nanoclusters. In this paper, ligand engineering was exploited to render reversible Cu–S motif transformation between [Au4Cu4(SAdm)5(Dppm)2]Br and [Au4Cu5(C6H11S)6(Dppm)2]­(BPh4) (SAdmH = 1-adamantane mercaptan, C10H15SH; C6H11SH = cyclohexyl mercaptan; Dppm = bis-(diphenylphosphino)­methane, Ph2PCH2PPh2), which was well characterized by single-crystal X-ray crystallography (SCXC) and monitored by time-dependent UV–vis absorption spectroscopy. Surprisingly, by etching with cyclohexyl mercaptan (C6H12S), [Au4Cu4(SAdm)5(Dppm)2]+ was converted to [Au4Cu5(C6H11S)6(Dppm)2]+, accompanied by the transformation of Cu4(SAdm)5 to Cu5(C6H11S)6. Besides, a reversible transformation reaction can be achieved via HSAdm etching with [Au4Cu5(C6H11S)6(Dppm)2]+. These reversible Cu–S motif transformations via thiol ligand engineering between [Au4Cu4(SAdm)5(Dppm)2]+ and [Au4Cu5(C6H11S)6(Dppm)2]+ present a new desirable model to tailor the structure of Au–Cu alloy nanoclusters capped with Dppm and thiol ligands at the atomic level.