Structural Basis for Ligand Exchange on Au₂₅(SR)₁₈

Abstract

The single-crystal X-ray structure of Au₂₅(SC₂H₄Ph)₁₆(pBBT)₂ is presented. The crystallized compound resulted from ligand exchange of Au₂₅(SC₂H₄Ph)₁₈ with pBBT as the incoming ligand, and for the first time, ligand exchange is structurally resolved on the widely studied Au₂₅(SR)₁₈ compound. A single ligand in the asymmetric unit is observed to exchange, corresponding to two ligands in the molecule because of the crystallographic symmetry. The ligand-exchanged Au₂₅ is bonded to the most solvent-exposed Au atom in the structure, making the exchange event consistent with an associative mechanism. The apparent nonexchange of other ligands is rationalized through possible selective crystallization of the observed product and differential bond lengths