Monoarsine-protected icosahedral cluster [Au(AsPh)Cl]: comparative studies on ligand effect and surface reactivity with its stibine analogue.

Ligand shells of gold nanoclusters play important roles in regulating their molecular and electronic structures. However, the similar but distinct impacts of the homologous analogues of the protecting ligands remain elusive. The symmetric monoarsine-protected cluster [Au(AsPh)Cl] (AuAs) was facilely prepared by direct reduction of (PhAs)AuCl with NaBH. This cluster is isostructural with its previously reported stibine analogue [Au(SbPh)Cl] (AuSb), enabling a comparative study between them. AuAs exhibits a blue-shifted electronic absorption band, and this is probably related to the stronger π-back donation interactions between the Au core and AsPh ligands, which destabilize its superatomic 1P and 1D orbitals. In comparison to the thermodynamically less stable AuSb, AuAs achieves a better trade-off between catalytic stability and activity, as demonstrated by its excellent catalytic performance towards the aldehyde-alkyne-amine (A) coupling reaction. Moreover, the ligand exchange reactions between AuAs with phosphines, as exemplified by PPh and PhP(CH)PPh, suggest that AuAs may be a good precursor cluster for further cluster preparation through the "cluster-to-cluster" route.