类硅烯H2SiLiF 和 CH3XHn-1 (X=F, Cl, Br, O, N; n=1, 1, 1, 2, 3)取代和插入反应的理论研究

he substitution and insertion reactions of silylenoid H2SiLiF and CH3XHn-1 (X=F, Cl, Br, O, N; n=1, 1, 1, 2, 3) have been studied by using density functional theory at the B3LYP/6-311+G (d, p) level. There are two paths for the substitution reactions, and the activation barriers decrease in the order ofCH3NH2 > CH3OH > CH3F > CH3Cl > CH3Br in both paths. H2SiFCH3 and LiX are final products of substitution reactions. Calculations about solvent effects on the substitution reactions show that the reaction barriers increase with the the solvent polarity. H2SiCH3X and LiF are the final insertion products of the insertion reactions of silylenoid H2SiLiF into the C-X, and the barriers increase in the order of C-Br < C-F < C-Cl < C-O < C-N. Comparisons between the substitution and insertion reactions indicate substitution reactions prevail over the corresponding insertion reactions.