Mechanisms and Energetics of Alkane Activation by Transition Metal Ions in the Gas Phase

The mechanisms and energetics of alkane activation by transition metal ions in the gas phase are studied using an ion beam apparatus. These investigations concentrate on the reactivity of several early first row transition metal ions (Sc+, Ti+, V+) and the second row group 8-10 metal ions (Ru+, Rh+, Pd+). The reaction mechanisms are probed using deuterium labelled alkanes. Experimental and theoretical metal-ligand bond dissociation energies are used to help interpret the observed metal ion reactivities. Chapter II provides a detailed study of the reactions of Ru+, Rh+ and Pd+ with alkanes. The reactivity observed is contrasted to that of their first row congeners Fe+, Co+ and Ni+. Chapter III presents a determination of the heterolytic, M+-H-, and homolytic, M-H, bond dissociation energies for the first and second row group 8-10 metals. A correlation is found between the homolytic bond energies and the metal atom promotion energy to a state derived from an s1dn electronic configuration. Chapter IV examines the reactions of Ti+ and V+ with alkanes and deuterium labelled alkanes. Dehydrogenation mechanisms and deuterium isotope effects are explored. Chapter V reports the unusual reactivity of Sc+ with alkanes. The ability of Sc+ to form two strong metal-ligand sigma bonds results in alkane activation processes which are not observed for most other transition metal ions.