A gas-phase kinetic study of the reaction of silylene with germane: absolute rate constants, temperature dependence and mechanism

Abstract

Time-resolved studies of silylene, SiH₂, generated by laser flash photolysis of phenylsilane, have been carried out to obtain rate constants for its bimolecular reaction with monogermane, GeH₄. The reaction was studied in the gas-phase at 10 Torr total pressure in SF₆ bath gas, at five temperatures in the range 295–553 K. The second order rate constants fitted the Arrhenius equation: log(k₃/cm³ molecule⁻¹ s⁻¹) = (−9.88 ± 0.02)+(2.13 ± 0.17 kJ mol⁻¹)/RTln10. Experiments at other pressures showed that these rate constants were unaffected by pressure. The data are consistent with a fast association process occuring (at 298 K) close to the collision rate. Although the probable initial product is silylgermane, H₃SiGeH₃, thermochemical considerations show that this will decompose to GeH₂ + SiH₄ under experimental conditions. This silylene insertion process is compared to others as well as to the insertion processes of methylene, CH₂ and germylene, GeH₂.