Absolute rate constants for the gas-phase reactions of silylene with silane, disilane and the methylsilanes

Abstract

Absolute rate constants for reactions of silylene have been determined by time-resolved measurements of its decay at room temperature, following formation by pulsed-laser photolysis of phenylsilane in the presence of various added silanes. For SiH₄ and Si₂H₆ the rate coefficients are pressure dependent and the former reaction is successfully modelled using RRKM theory. High-pressure (or pressure-independent) rate constants (in 10^–10 cm³ molecule^–1 s^–1) are: SiH₄, ca. 4.0; Si₂H₆, ca. 6.5; MeSiH₃, 3.66 ± 0.22; Me₂SiH₂, 3.31 ± 0.26; and Me₃SiH, 2.47 ± 0.14. These results are compared with other determinations and the rate constants for the analogous reactions of SiMe₂. A model for the insertion reaction is proposed in which the nucleophilic stage of the process plays an important role.