Surface modifications of eight-electron palladium silver superatomic alloys.

Atomically precise thiolate-protected coinage metal nanoclusters and their alloys are far more numerous than their selenium congeners, the synthesis of which remains extremely challenging. Herein, we report the synthesis of a series of atomically defined dithiophosph(in)ate protected eight-electron superatomic palladium silver nanoalloys [PdAg{SPR}], 2a-c (where R = OPr, a; OBu, b; Ph, c) via ligand exchange and/or co-reduction methods. The ligand exchange reaction on [PdAg{SP(OPr)}], 1, with [NH{SePR}] (where R = OPr, or OPr) leads to the formation of [PdAg{SeP(OPr)}] (3) and [PdAg{SeP(OPr)}] (4), respectively. Solid state structures of 2a, 2b, 3 and 4 unravel different PdAg metal frameworks from their parent cluster, originating from the different distributions of the eight-capping silver(I) atoms around a Pd@Ag centered icosahedron with C D T and T symmetries, respectively. Surprisingly ambient temperature crystallization of the reaction product 3 obtained by the ligand exchange reaction on 1 has resulted in the co-crystallization of two isomers in the unit cell with overall T (3a) and C (3b) symmetries, respectively. To our knowledge, this is the first ever characterized isomeric pair among the selenolate-protected NCs. Density functional theory (DFT) studies further rationalize the preferred geometrical isomerism of the PdAg core.