Gas phase anion–molecule chemistry of SF6 , SeF6 and TeF6

Abstract

The rate coefficients and anion product branching ratios for the thermal (300 K) reactions of O₂⁻ , O⁻, OH⁻, CF₃⁻ , and F⁻ with SeF₆ and TeF₆ are reported. Non-dissociative and dissociative electron transfer pathways are identified, together with F⁺ abstraction and association. F⁻ does not react with SeF₆ ; all the other reactions proceed at or close to the capture rate. This is in contrast to SF₆ , for which the only observed reaction with the above anions is slow (k = 3.0 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹) electron transfer with O₂⁻ to form SF₆⁻ . The results are shown to be consistent with the available thermochemistry. There is evidence for a substantial intrinsic barrier to F⁺ abstraction, for this pathway is only observed when it is highly exothermic. There is a remarkably fast association reaction between F⁻ and TeF₆ , arising from the high fluoride affinity of TeF₆ and facile expansion of the Te co-ordination sphere to accommodate seven ligands.