Origin of Bonding Interactions in Cu₂⁺(H₂)<i>_n</i> Clusters: An Experimental and Theoretical Investigation

Abstract

Equilibrium methods were used to measure binding energies and entropies for the attachment of up to six H2 ligands to ground-state Cu2+ (2Σg, 3d20 σ1). Bond dissociation energies (BDEs) of the first five H2 ligands added to ground-state Cu2+ are 12.4, 10.1, 4.9, 3.8, and 2.1 kcal/mol respectively, with the BDE of the sixth ligand approximated to be 1.7 kcal/mol. Entropy measurements indicated all six of the H2 ligands were in the first solvation shell. Theoretical calculations at the DFT-B3LYP level were done on Cu2+ for the first four H2 ligands. Vibrational frequencies and geometries were determined, and the origin of the bonding and its variation with Cu2+ coordination was examined. Comparisons are made to the Cu+(H2)n and Zn+(H2)n systems.