Gas-phase reactions of tantalum carbide cluster ions with deuterium and small hydrocarbons

Article abstract of DOI:10.1021/ja00168a025

The gas-phase ion/molecule reactions of tantalum carbide cluster ions (TaC_y⁺, y = 0-14) with D₂, CH₄, C₂H₄, and C₂H₆ have been investigated by Fourier transform mass spectrometry. Product branching ratios and reaction rate constants are reported. The addition of tantalum dramatically alters the reactivity relative to that of the corresponding carbon clusters (C_y⁺), leading to the conclusion that the TaC_y⁺ reactions are initiated on the metal. In addition, the extensive dehydrogenation and secondary reactivity that characterize the reactions of Ta⁺ with hydrocarbons are observed for TaC_y⁺. Experiments with isotopically labeled precursors were performed, as well as low-energy collision-induced dissociation studies of major reaction products. The implications of these studies with respect to TaC_y⁺ structures and reaction mechanisms are discussed. Total scrambling of the labeled carbon occurred during the TaC_y⁺ reactions with ¹³CH₄. This indicates that the mechanism involves incorporation of the methane carbon into the C_y ligand(s) prior to elimination of a neutral and suggests the possibility of cyclic TaC_y⁺ structures. Evidence is also presented for two structural isomers of TaC₇⁺, TaC₈⁺, and TaC₉⁺.