Hydrogen Atom Abstraction Reaction from Silane with Hydrogen and Methyl Radicals: Rate Constants and Kinetic Isotopic Effects

The thermal rate constants and H/D kinetic isotope effects (KIEs) of the reactions SiH₄ + H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>→</mml:mo></mml:math> SiH₃ + H₂ and SiH₄ + CH₃ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>→</mml:mo></mml:math> SiH₃ + CH₄ were calculated with the variational transition state theory including multidimensional tunneling corrections (VTST-MT). The ωB97X-D and CCSD(T) methods were employed to compute the barrier height and reaction energy. The ωB97X-D/aug-cc-pVTZ methodology was used to build reaction paths, and the CCSD(T)/CBS_Q-5 approach was used to improve the energetics of the stationary points in the calculations of CVT/μOMT thermal rate constants. For the SiH₄ + H pathway, the CVT/μOMT rate constants and H/D KIEs are in excellent agreement with previous experimental and theoretical calculations; otherwise, for the SiH₄ + CH₃ pathway, which has few experimental and theoretical data available, it has provided, for the first time, rate constants and kinetic isotope effects using variational transition state theory with multidimensional tunneling corrections.