Ni+(H2)n: Ligand bond energies for ground state ions

The H2 ligand binding energies in Ni+(H2)n were measured to be 17.3, 17.6, 11.3, 7.1 and 4.2 kcal/mol, for n=1–5, respectively. The very weakly bound sixth ligand begins a new solvation sphere. Association entropies were also measured. MP2 calculations were done to determine geometries and vibration frequencies as well as the origin of the bonding. The observed changes in BDE with ligation are due to electronic rather than steric effects. Comparisons are made to the Fe+(H2)n, Co+(H2)n, Cu+(H2)n and Ni+(CO)n systems. A highly symmetric D3h planar structure is found in Ni+(H2)3 and forms the core of the Ni+(H2)4, 5 ions.