Gas Phase Anion Molecule Chemistry of SeF₆ and TeF₆

The rate coefficients and anion product branching ratios for the thermal (300 K) reactions of O-2(-), 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 SF, for which the only observed reaction with the above anions is slow (k=3.0x10(-11) cm(3) molecule(-1) s(-1)) electron transfer with O-2(-) 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.