Prediction of strong O-H/M hydrogen bonding between water and square-planar Ir and Rh complexes.

Intermolecular O-H/M interactions, between a water molecule and square-planar acac complexes ([M(acac)L2]), with different types of L ligands (en, H2O, CO, CN-, and OH-) and different types of metal atoms (Ir(i), Rh(i), Pt(ii), and Pd(ii)) were studied by high level ab initio calculations. Among the studied neutral complexes, the [Pd(acac)(CN)(CO)] complex forms the weakest interaction, -0.62 kcal mol-1, while the [Ir(acac)(en)] complex forms the strongest interaction, -9.83 kcal mol-1, which is remarkably stronger than the conventional hydrogen bond between two water molecules (-4.84 kcal mol-1).