The calculated H2 adsorption enthalpy, -∆H°DFT, is 31.6, 26.7, and 24.0 kJ/mol for the Cu I Zn4, Cu I Mn4, and Cu I Cd4 clusters, respectively (Table ). These values are close to the isosteric enthalpy of H2 adsorption, -∆Hads, obtained from the Clausius-Clapeyron analysis discussed above. While the computational results are obtained for a Cu1M4Cl3(bta)6 cluster with only one Cu I per cluster, computation for clusters with either two or three Cu I sites yield similar results in coordination structures around Cu I -H2 and the thermodynamics for H2 binding (Tables and).