Gas phase activation of carbon dioxide by niobium and niobium monoxide cations

Guided ion beam mass spectrometry is used to investigate the kinetic energy dependence of the reactions of Nb+ (D-5) and NbO+ ((3)Sigma(-)) with CO2, and the reverse pathways, NbO+ ((3)Sigma(-)) and NbO2+ with CO. These systems exhibit complicated behavior because the ground states of the reactants and products have different spins. To further probe the potential energy surfaces for these reaction systems, NbO2+ and the intermediates, ONb(CO)(+), ONb(CO2)(+), and O2Nb(CO)(+), are studied by collisional activation experiments with Xe. Analysis of the reaction cross sections obtained in this study yield (in eV) D-0(Nb+-CO) = 0.99 +/- 0.05, D-0(ONb+-CO) = 1.10 +/- 0.05, D-0 (ONb+-CO2)= 0.88 +/- 0.03, D-0(O2Nb2-CO) = 1.11 +/- 0.05, and D-0(ONb+-O) = 5.71 +/- 0.17. Speculative determinations of electronic excitation energies for two states each of NbO+ and of NbO2+ are also made. Combining the results obtained from this study and those obtained from the literature, we are able to generate a fairly complete potential energy surface for the Nbi reaction system. We also compare the reactivities of Nb+, NbO+, and NbO2+ with respect to the interconversion of CO and CO2. (C) 1998 Elsevier Science B.V.