Theoretical Studies of Transition-Metal Hydrides. 3. SRH⁺through CdH⁺

Generalized valence bond plus configuration interaction calculations have been carried out on the monopositive diatomic metal hydride ions of the second transition-metal series (YH⁺-CdH⁺, including SrH⁺). We analyze the trends in bond energies, equilibrium geometries, vibrational frequencies, and metal orbital hybridizations. The trends in these quantities can be understood in terms of (1) the low-lying electronic states of the metal, (2) the orbital sizes of the metal, (3) the loss of exchange energy on bonding to the high-spin metal, and (4) the intrinsic bond strengths of bonding H to metal 5s and 4d electrons. We also present bond lengths, vibrational frequencies, and relative energies for selected MH⁺excited states.