Reactions of transition-metal ions with sulfur hexafluoride in the gas phase

The inertness of SF[sub 6] is well-known to be associated with the protective layer of F atoms which obstructs the access to the reactive S center by an attacking species. Previous gas-phase studies of SF[sub 6] involved reactants having high ionization energies, such as He[sup +], Ar[sup +], and N[sub 2][sup +], which are observed to yield predominantly SF[sub 5][sup +] either via F[sup [minus]] abstraction or dissociative charge transfer. This study shows that early transition metal ions, despite their low ionization potentials, can react with SF[sub 6] yielding product distributions much different from those of the reactions studied previously. In contrast, the reduced reactivity and mainly absence of reactivity observed for the late transition metal ions indicates that an empty d orbital is required for reaction. Rate constants for some selected early transition metal ion reactions are determined. Sc[sup +] was chosen to be studied in detail because a complete set of thermodynamic data on ScF[sub n][sup +/0] were available in the literature. The reaction pathways are derived and a reaction mechanism involving oxidative addition is proposed. 44 refs., 3 figs., 7 tabs.