MoO-14
LASER GENERATED NIOBIUM OXIDE ANIONS: STRUCTURES FROM CID AND ION-MOLECULE REACTION STUDIES
Phillip Jackson, Keith J. Fisher and Gary D. Willett
School of Chemistry, University of New South Wales, Sydney, NSW, 2052
Although niobium has a low terrestrial abundance, it is of considerable commercial interest due to the potential catalytic/superconducting properties of crystalline phases of the polymorphic oxide Nb2O5. It is understood that the niobium-oxygen double bond is principally responsible for the catalytic activity of the oxide surface [J. M. Jengh and I. E. Wachs, Catal. Today 8 (1990) 37], and in order to investigate this further at a molecular level, we have used laser ablation to generate and study the anions NbO3-, Nb2O5-, Nb2O6H-, Nb3O8-, Nb4O10-, Nb5O13-, and Nb6O15-. The neutral analogues of these ions may represent important subunits in the condensation of Nb-O vapours.
Structural trends were evident from the ion-molecule reaction studies with the small primary alcohols CH3OH and CH3CH2OH. In particular, extraction of OH, H2O facilitates further addition of either the methylene/ethylene ligand to the smaller ions via condensation reactions. CID results will be compared with recent quadrupole-MS results for the analogous cation series [H. T. Deng, K. P. Kerns, and A. W. Castleman, J. Phys. Chem. 100 (1996) 13386]. Some thermochemical results will also be discussed.
Representative negative ion ablation spectrum. A, B - no. of Nb, no. of O atoms