Theoretical Study of Sc2+, Ti2+, V2+, Cr2+, and Mn2+ Bound to H2

Abstract

The binding energies, vibration frequencies, and geometry of the high spin complexes of the dipositive transition metals, Sc2+, Ti2+, V2+, Cr2+, and Mn2+, with molecular H2 have been determined for all states correlating to the lowest term of the dipositive ion using multireference CI techniques. As expected, the bonding in these complexes is dominated by electrostatics (that is, enhanced by electron correlation) and varies smoothly across the sequence from Sc to Mn. The high spin complexes for Sc2+, Ti2+, V2+, and Mn2+ are the thermodynamic ground states for the MH22+ system. For Cr2+, however, the large second ionization energy of Cr results in the charge exchange reaction Cr2+ + H2 → Cr+ + H2+ being competitive with the electrostatic complex. The computed properties are compared with those for the corresponding monopositive ions.