AMMONIA ACTIVATION BY V+ - ELECTRONIC AND TRANSLATIONAL ENERGY-DEPENDENCE

The reaction of V+ with ammonia is studied as a function of translational energy in a guided ion beam tandem mass spectrometer. The effect of electronic energy is also probed by varying the conditions for forming V+. The a3F state of V+ is found to be substantially more reactive than the a5D ground and a5F first excited states. The results indicate that reaction occurs primarily through a triplet H-V+-NH2 intermediate. The reactivities of the different electronic states of V+ can be explained by using molecular orbital and spin conservation concepts. The thresholds for the cross sections of the endothermic reactions are interpreted to give the 298 K bond energies of D°(V+-NH2) = 3.18 ± 0.10, D°(V+-NH) = 4.30 ± 0.16, and D°(V+-N) = 4.65 ± 0.06, all in electronvolts. The large bond strengths of V+-NH2 and V+-NH indicate that the lone pair electrons on the nitrogen atom are involved in the metal-ligand bond. © 1990 American Chemical Society.