Hydrogen bonds to Au atoms in coordinated gold clusters

It is well known that various transition elements can form M···H hydrogen bonds. However, for gold, there has been limited decisive experimental evidence of such attractive interactions. Herein we demonstrate an example of spectroscopically identified hydrogen bonding interaction of C–H units to Au atoms in divalent hexagold clusters ([Au6]2+) decorated by diphosphine ligands. X-ray crystallography reveals substantially short Au–H/Au–C distances to indicate the presence of attractive interactions involving unfunctionalized C–H moieties. Solution 1H and 13C NMR signals of the C–H units appear at considerably downfield regions, indicating the hydrogen-bond character of the interactions. The Au···H interactions are critically involved in the ligand-cluster interactions to affect the stability of the cluster framework. This work demonstrates the uniqueness and potential of partially oxidised Au cluster moieties to participate in non-covalent interaction with various organic functionalities, which would expand the scope of gold clusters.