Li Ruei-En, Sheu Jeng-Horng, Su Ming-Der
Department of Applied Chemistry, National Chiayi University, Chiayi 60004, Taiwan.
Inorg Chem. 2007 Oct 29;46(22):9245-53. doi: 10.1021/ic7012446. Epub 2007 Sep 15.
The potential energy surfaces for the reactions of stable silylenes with carbon tetrachloride have been characterized in detail using density functional theory [B3LYP/6-311G(d)], including zero-point corrections. Five stable silylene species (1-5) have been chosen in this work as model reactants. The activation barriers and enthalpies of the reactions are compared to determine the relative reactivity of the stable silylenes on the reaction potential energy surface. Our theoretical findings suggest that stable silylene 5, which has two carbon atoms bonded to the silicon center and does not contain a resonance structure, is relatively unstable with respect to the reaction with haloalkanes, in comparison with the other stable silylenes (1-4). Of the three possible reaction paths, Cl abstraction (path 1), CCl3 abstraction (path 2), and CCl4 insertion (path 3), path 1 is found to be most favorable, with a very low activation energy and a large exothermicity. In short, electronic as well as steric factors play a dominant role in determining the chemical reactivity of the stable silylene species kinetically as well as thermodynamically. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. The results obtained allow a number of predictions to be made.
利用密度泛函理论[B3LYP/6 - 311G(d)]，包括零点校正，详细表征了稳定硅烯与四氯化碳反应的势能面。本工作中选择了五种稳定的硅烯物种（1 - 5）作为模型反应物。比较反应的活化能垒和焓，以确定稳定硅烯在反应势能面上的相对反应活性。我们的理论研究结果表明，与其他稳定硅烯（1 - 4）相比，稳定硅烯5与卤代烷烃反应时相对不稳定，其硅中心与两个碳原子相连且不包含共振结构。在三种可能的反应路径中，即氯原子夺取（路径1）、三氯甲基夺取（路径2）和四氯化碳插入（路径3），发现路径1最有利，具有非常低的活化能和大量放热。简而言之，电子因素和空间因素在动力学和热力学上决定稳定硅烯物种的化学反应活性方面起着主导作用。此外，基于Pross和Shaik的工作使用了构型混合模型来合理化计算结果。所获得的结果使得能够做出许多预测。
