Binding energies and entropies have been measured for the attachment of up to six H-2x ligands to ground-state Cu+ ions (S-1, Ar3d(10)), to electronically excited Cu+* ions (D-1.3, Ar4s(1)3d(9)), and to hydrated H2O . Cu+ ions. The ground-state Cu+ ion added four H-2 ligands in the first solvation shell with bond dissociation energies (BDEs) of 15.4, 16.7, 8.8, and 5.1 kcal/mol. The fifth and sixth ligands begin a new solvation sphere and were very weakly bound. The BDEs for addition of H-2 to electronically excited Cu+* were also small (4.2, 2.5, and 1.4 kcal/mol for the first three ligands). The difference between ground- and excited-state association energies is almost entirely due Co the repulsive nature of the 4s electron. Hydration of the Cu+ ion significantly increased the BDE of the first H-2 ligand. (to 19.6 kcal/mol) but greatly reduced that of the second (to 3.8 kcal/mol). Theoretical calculations with large basis sets at the DFT-B3LYP and MP2 levels were done on all species both to determine geometries and vibration frequencies and to examine the origin of the bonding and its variation with Cu+ coordination. The calculations show that covalent interactions are important in these Cu+ clusters and that the observed changes in BDE as different ligands are added are due to electronic rather than steric effects. These sources of bonding are discussed, and comparisons are made to the Co+(H-2)(n) and Ni+(H2), systems. It is also shown that the M+-ligand interactions are similar for H-2 and CO ligands. Special attention is paid to the origin of the highly symmetric D-3h planar structure found in N+(H-2)(3), Cu+(H-2)(3) and Cu+(CO)(3).