A theoretical study of the addition of silyl radicals to olefinic monomers

Abstract

SUMMARY: In this paper, the high reactivity of silyl macroradicals toward double bonds of olefinic compounds has been explained by means of quantum-mechanical calculations through their frontier orbital characteristics. In this way, the main orbital interaction corresponds to the overlapping between the SOMO of the disilyl radical and the LUMO of the olefin. In order to obtain more accurate results of differential reactivity, an orbitalic SOMO-HOMO interaction should be included in addition to the main SOMO-LUMO one. Also, we theoretically studied the regioselectivity of the addition of silyl radicals to double bonds obtaining similar results as for carbon centered radicals where the reaction takes place on the less hindered carbon of the olefin. Regarding to the geometrical and electronic parameters, it has been shown that carbon radicals have a sp 2 geometry and a negative charge on the radical center whilst silyl radicals have a sp 3 goemetry and a positive charge. Both factors contribute to the enhanced reactivity of silyl radicals with respect to carbon ones.

Silyl Radicals

“…Calculations for the addition of trimethylsilyl and dimethyl(trimethylsilyl)silyl radicals to olefinic monomers using AM1 and PM3 semiempirical techniques have been reported 57 …”