THEORETICAL-STUDY ON THE SILYLIDYNE INSERTION INTO NH3, H2O, HF, PH3,H2S, AND HCL

The reaction paths of the silylidyne insertion into NH3, H2O, HF, PH3, H2O, HF, and HCl have been studied by means of ab initio molecular or bital calculations incorporating electron correlation with Moller-Ples set perturbation theory up to the second and fourth order and using po larization basis sets augmented by diffuse functions. All these reacti ons involve the initial formation of an intermediate complex followed by a hydrogen-migration process via a transition state. Analyses for t he reactivity of the six substrates in the SiH insertion reactions ind icate that the reaction with the hydride of the right-hand group has a less stable complex and is more exothermic than with the hydride of t he left-hand group and that the reaction with the second-row hydride h as a lower overall barrier and is less exothermic than with the first- row hydride. Comparison with the CH and SiH2 insertion reactions has b een made, and it is noted that the CH, SiH2, and SiH insertion reactio ns have similar reaction processes. The energetic results (for the bar riers and reaction enthalpies) indicate that the SiH radical is less r eactive than the CH radical in the insertion reactions.