Free radical chemistry associated with H(RSiH) nH

Article abstract of DOI:10.1016/S0022-328X(97)00344-6

Polysilanes of the type H(RSiH)_nH, where R = n-hexyl or phenyl, have been used as radical-based reducing agents for organic halides. They rival the effectiveness of the other group 14 hydrides in reduction processes. The repetitive hydrogen transfer from the same molecule of H(RSiH)_nH allows these compounds to be used in small quantities. Lower (5 × 10⁴ M^-1 s^-1) and higher (6 × 10⁵ M^-1 s^-1) limit values for the rate constant of the reaction of primary alkyl radicals with each SiH moiety of H(PhSiH)_nH have been obtained by using unimolecular radical reactions as timing devices. The photochemical behavior of these polysilanes in the presence or absence of di-tert-butyl peroxide have been studied by EPR spectroscopy, and the -SiHR-SiR-SiHR radical (R = n-hexyl) has been identified as a transient species. Silyl radicals, obtained from H(RSiH)_nH and thermally generated tert-butoxyl radicals, add to a variety of substrates containing double bonds to give the corresponding adducts for which EPR spectra have been recorded.