COLLISION-INDUCED DISSOCIATION STUDIES OF V(CO)(X)(+), X=1-7 - SEQUENTIAL BOND-ENERGIES AND THE HEAT OF FORMATION OF V(CO)(6)

The sequential bond energies of V(CO)(x)(+), x = 1-7, are determined by collision-induced dissociation with xenon in a guided ion beam tandem mass spectrometer. Bond energies (in eV) at 0 K are determined to be D[V+-CO] = 1.17 +/- 0.03, D[(COV+-CO] = 0.94 +/- 0.04, D[(COV+-CO] = 0.72 +/- 0.04, D[(COV+-CO] = 0.89 +/- 0.10, D[(COV+-CO] = 0.94 +/- 0.03, D[(COV+-CO] = 1.03 +/- 0.07, D[(COV+-CO] = 0.52 +/- 0.09, and D[V+-Xe] = 0.83 +/- 0.07. The values here, along with the established heats of formation for V+ and CO and the ionization energy of V(CO)(6), indicate that the 298 K heat of formation of V(CO)(6)(+) is -60 +/- 16 kJ/mol and that of V(CO)6 is -792 +/- 21 kJ/mol. These values are somewhat lower than those in the literature, which are extrapolated from electron impact appearance energy measurements. The nonmonotonic trends in the sequential bond energies are discussed in terms of spin conservation and ligand field theory.