Abstract
The coordination motif of alkynly with a metal atom is versatile and plays a pivotal role in tailoring the kernel configuration of the atomically precise metal nanoclusters. In this study, we synthesized a new mono-valent Au(I)2Ag(I)2(C10H6NO)4(Ph3P)2 alloy cluster with a very high yield of >90%, which is well characterized by a serial of technologies, e.g. UV-vis, X-ray single crystal diffraction (SCXRD) and FT-IR. The SCXRD analysis shows the alloy cluster is composed of a quadrangular Au2Ag2 kernel protected by four alkynyl and two phosphine ligands. Intriguingly, a new divergent alkyne-metal coordination model is revealed in this cluster, the alkynyl ligands selectively bind to Au and Ag atoms via σ- and π-bond configurations and adopt a VI-shaped alkynyl-M motif. It is distinct from the convergent motif observed in big clusters featuring an IV- or V-shaped alkynyl-M motif due to the steric effect. Finally, the titanium oxide-supported Au2Ag2 cluster catalysts show good catalytic performance in the multicomponent coupling reaction of alkynes, aldehydes and amines.