Distibine versus Diphosphine Ligands: Modulating the Properties of Isostructural Au ₁₃ Cu ₂ Nanoclusters

We report the first example of a pair of isostructural atomically precise Au13Cu2 bimetallic nanoclusters (NCs) protected by mixed monolayers of distibine or diphosphine and pyridine-thiolate ligands. Total structure determination of the synthesized NCs, namely, [Au13Cu2(dpsf)3(F3C-pyS)6][PF6], i.e., Au13Cu2(Sb), and [Au13Cu2(dppf)3(Cl-pyS)6][PF6], i.e., Au13Cu2(P) (dpsf = 1,1′-bis(diphenylstibino)ferrocene, F3C-pySH = 5-trifluoromethyl-2-mercaptopyridine, dppf = 1,1′-Bis(diphenylphosphino)ferrocene, Cl-pySH = 5-chloro-2-mercaptopyridine), by single-crystal X-ray diffraction reveals both the NCs to be 8-electron superatoms. The metal core of these NCs consists of a traditional Au13 icosahedron, two triangular Au3 faces of which are capped by one Cu atom on opposite ends. The symmetry of this achiral Au13Cu2 core is broken by the asymmetric arrangement of pyridine-thiolate and diphosphine/distibine ligands on the Au13Cu2 NC surface. Although the two NCs exhibit the same metal core and ligand binding modes, distinct differences along with similarities are observed in their optical properties, stability, chemical reactivity, and catalytic properties. Taken together, our findings underscore the significant role ligating atoms in the same group (i.e., P vs Sb) play in modulating the properties of metal NCs.