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 20 {S 2 PR 2 } 12 ], 2a-c (where R = O i Pr, a; O i Bu, b; Ph, c) via ligand exchange and/or co-reduction methods. The ligand exchange reaction on [PdAg 20 {S 2 P(O n Pr) 2 } 12 ], 1, with [NH 4 {Se 2 PR 2 } 12 ] (where R = O i Pr, or O n Pr) leads to the formation of [PdAg 20 {Se 2 P(O i Pr) 2 } 12 ] (3) and [PdAg 20 {Se 2 P(O n Pr) 2 } 12 ] (4), respectively. Solid state structures of 2a, 2b, 3 and 4 unravel different PdAg 20 metal frameworks from their parent cluster, originating from the different distributions of the eight-capping silver(I) atoms around a Pd@Ag 12 centered icosahedron with C 2, D 3, T h and T h 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 3 (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 20 core.