THE BINDING-ENERGIES OF CU+-(H2O)N AND CU+-(NH3)N (N = 1-4)

The successive binding energies of up to four H2O and NH3 ligands to CU+ are computed at the self-consistent-field and modified coupled-pair functional levels. The most stable structures are those where all ligands are equivalent. Replacing Cu+ by a point charge gives binding energies that are in good agreement with ab initio and experimental results, and is consistent with bonding that is largely charge dipole in nature. About two-thirds of the large reduction in ligand binding energy between the second and third ligand is due to ligand-ligand repulsion, while one-third is due to increased metal-ligand repulsion resulting from a loss of sd-sigma hybridization. The first and second ligand binding energies increase substantially at the correlated level due to improved description of sd-sigma hybridization.