Acetylide-for-thiolate and thiolate-for-acetylide exchange on gold nanoclusters

Acetylide-protected gold nanoclusters represent a recently described class of nanocluster compounds that are computationally predicted to be more stable than well-studied thiolate-protected clusters. Ligand exchange of thiolates-for-acetylides on these clusters as well as the reverse reaction are so-far unknown. Such reactions can inform a practical understanding of stability and other differences between thiolate- and acetylide-protected gold clusters. Here it is shown that acetylide-for-thiolate ligand exchange is facile when using either a lithium phenylacetylide or a gold( i )-phenylacetylide complex as incoming ligand to thiolate-protected gold clusters, whereas the reaction fails when using phenylacetylene. Both partial and full exchange are possible, as is the reverse reaction. While the overall reaction resembles ligand exchange, it may be better described as a metathesis reaction. Notably, while the simple thiolate-for-acetylide exchange reaction is enthalpically unfavorable, metathesis reactions between these ligands are enthalpically favorable. Intercluster exchange is also observed between thiolate-protected and acetylide-protected clusters. New ligand-exchange reactions are reported for thiolate- and acetylide-protected gold nanoclusters, which are rationalized through bond strengths and enthalpy arguments.