Theoretical Investigations on Reactions of a Series of Stable Dialkyl-Substituted Silicon-Chalcogen Doubly Bonded Compounds

摘要

The potential energy surfaces for the formation, addition, and cycloaddition reactions of dialkylsilanechalcogenone (2) species have been studied using three levels of theories, i.e., B3LYP/ LANL2DZdp, CCSD theory, and Gibbs free energy (at the B3LYP level). Four dialkylsilanechalcogenone species with a SidXbond, whereX=O, S, Se, and Te, have been chosen as model reactants in this work. Also, both MeOH addition and isoprene cycloaddition have been used to study the chemical reactivities of these species (2). The present theoretical investigations suggest that the relative reactivity of 2 increases in the order X = O < S < Se , Te. That is, the species with a less electronegative and a heavier chalcogen atom will have a smaller ΔEst, which facilitates its addition with MeOH and its cycloaddition reaction to isoprene. Furthermore, the singlet-triplet energy splitting, as described in the configuration mixing model attributed to the work of Pross and Shaik, can be used as a diagnostic tool to predict the reactivity of species such as 2. The results obtained are consistent with the available experimental observations and allow a number of predictions to be made.