Eight-Electron Silver and Mixed Gold/Silver Nanoclusters Stabilized by Selenium Donor Ligands

The first atomically and structurally precise silvernanoclusters stabilized by Se-donor ligands, [Ag-20{Se2P-((OPr)-Pr-i)(2)}(12)] (3) and [Ag-21{Se2P(OEt)(2)}(12)](+)(4), were isolated by ligand replacement reaction of [Ag-20{S2P((OPr)-Pr-i)(2)}(12)] (1) and [Ag-21{S2P((OPr)-Pr-i)(2)}(12)](+) (2), respectively. Furthermore, doping reactions of 4 with Au(PPh3)Cl resulted in the formation of [AuAg20{Se2P(OEt)(2)}(12)](+) (5). Structures of 3, 4, and 5 were determined by single-crystal X-ray diffraction. The anatomy of cluster 3 with an Ag-20 core having C-3 symmetry is very similar to that of its dithiophosphate analogue 1. Clusters 4 and 5 exhibit an Ag-21 and Au@Ag-20 core of O-h symmetry composed of eight silver capping atoms in a cubic arrangement and encapsulating an Ag-13 and Au@Ag-12 centered icosahedron, respectively. Both ligand exchange and heteroatom doping result in significant changes in optical and emissive properties for chalcogen-passivated silver nanoparticles, which have been theoretically confirmed as 8-electron superatoms.