Direct ESR evidence for SH2 type reaction of methyl radical with methylsilane and methylgermane in a low temperature solid: A deuterium labeling study

The first ESR spectroscopic evidence of a bimolecular homolytic substitution (SH2) reaction in a 77 K solid phase was presented, where CD3 radicals were substituted for the CH3 group of methylsilane and methylgermane (CH3XD3, X = Si, Ge). The CD3 radicals were generated by in situ UV-photolysis of CD3I in the solid CH3XD3 in an ESR cavity at 77 K. Using the selectively deuterium labeled compounds, it was demonstrated that the SH2 reaction proceeded over a competitive H atom abstraction reaction with a large H/D isotope effect. Ab initio and density functional theory calculations complement the experimental results.