The potential energy surfaces for the insertion of silylene into C-H bond of methane were studied using density functional theory (DFT). All the stationary points were determined at the BELYP/6-311G level of the theory. The transition state both to the reactant and the product direction in the reaction paths was examined by using the intrinsic reaction coordinate (IRC). A configuration mixing model has been used to explain the barrie height and the reaction enthalpy. The results show that the single-triplet splitting △Est of the SiXY species plays an mportant role to predict its activity for the insertion reactions. The major conclusion is as follows: the more strong the π-donation is or the more electronegative the substituents are the larger the △Est of SiXY, the higher the activation energy, and the smaller the exothermicity for the insertion of SiXY into saturated C-H bonds will be. In other words, it is the electronic factors, rather than the steric factors, that play a decisive role in determinning the chemical reactivity of the silylene species.

Key words: SILYLENE, INSERTION REACTION, TRANSITION STATE THEORY, METHANE, EXCITED STATE