Regiochemistry of thiolate for selenolate ligand exchange on gold clusters.

Ligand exchange is a fundamental reaction of metal nanoparticles. Multiple symmetry and kinetic exchange environments are observed for thiol protected gold nanoparticles, but the correlation between these is unclear. Structural study of ligand exchange on chalcogenide passivated gold clusters has so far revealed the locations of 10% or fewer of incoming ligands. In a set of 13 crystal structures, we reveal the locations of up to 17 ligands of the 18 ligands in thiolate for selenolate exchanged Au25SeR18-xSRx clusters. Overall, we see a distinct preference for the locations of thiolate and selenolate ligands that emerges over time. This most-comprehensive to-date structural study of ligand exchange on gold clusters evidences a structural basis for exchange of solvated ligands, exchange of ligands between clusters, and a net reaction that amounts to translation of ligands on the cluster surface.