FREE-RADICAL CHEMISTRY ASSOCIATED WITH H(RSIH)(N)H

Polysilanes of the type H(RSiH)(n)H, 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 pr ocesses. The repetitive hydrogen transfer from the same molecule of H( RSiH)(n)H allows these compounds to be used in small quantities. Lower (5 X 10(4) M-1 s(-1)) and higher (6 x 10(5) M-1 s(-1)) limit values f or the rate constant of the reaction of primary alkyl radicals with ea ch SiH moiety of H(PhSiH)(n)H have been obtained by using unimolecular radical reactions as timing devices. The photochemical behavior of th ese polysilanes in the presence or absence of di-tert-butyl peroxide h ave been studied by EPR spectroscopy, and the -SiHR-SiR-SiHR radical ( R = n-hexyl) has been identified as a transient species. Silyl radical s, obtained from H(RSiH)(n)H and thermally generated tert-butoxyl radi cals, add to a variety of substrates containing double bonds to give t he corresponding adducts for which EPR spectra have been recorded. (C) 1997 Elsevier Science S.A.