GAS-PHASE REACTIONS OF MOLYBDENUM OXIDE IONS WITH SMALL HYDROCARBONS

The gas-phase ion/molecule reactions of Mo+, MoO+, and MoO2+ with small alkanes, alkenes, and C6 hydrocarbons have been investigated using Fourier transform ion cyclotron resonance mass spectrometry. Product branching ratios and reaction rate constants are reported. Dehydrogenation dominates the reactions, with little cleavage of the strong Mo+-O and OMo+-O bonds. Aside from the production of MoO(CO)+ from MoO2+ and ethene, no evidence is found for the formation of oxygenated hydrocarbons, either as neutral reaction products or as ligands bound to Mo+. However, the reactions of Mo+, MoO+, and MoO2+ differ in terms of both rates and pathways. In contrast to the slow reaction rates of the d5 system Mo+, several MoO+ and MoO2+ reactions proceed at or near the collision rate. Variations are also seen in product ion distributions, and for MoO2+, unique reaction pathways involving dehydration and the elimination of small hydrocarbons occur. While Mo+ and MoO+ yield only products which are the result of C-H insertion, MoO2+ is capable of inserting into the C-C bonds of organic molecules.