NA+ K+CENTER-DOT(H-2)(1,2) CLUSTERS - BINDING-ENERGIES FROM THEORY AND EXPERIMENT/

Dissociation energies for H-2 loss from Na+.(H-2)(1,2) and K+.(H-2)(1, 2) clusters have been determined via temperature-dependent equilibrium measurements. D-0 = -Delta H-0 degrees = 2.45 +/- 0.2 and 2.25 +/- 0. 2 kcal/mol for Na+-H-2 and H-2.Na+-H-2, respectively, and 1.45 +/- 0.2 and 1.26 +/- 0.4 kcal/mol for K+-H-2 and H-2.K+-H-2, respectively. Al so, ab initio calculations on Na+.H-2 were carried out at the HF and M P2 levels with an extended basis set and compared with previous calcul ations on this system as well as with experiment. By extrapolating the se purely electrostatic results to the first-row transition series, on e can conclude that covalent interactions dominate the bonding in V+-H -2 and Co+-H-2 systems.