锗烯X2Ge与环硫乙烷硫转移反应的密度泛函研究

利用量子化学密度泛函理论(DFT)的B3LYP方法, 在6-311++G(d, p)的水平上对锗烯X2Ge(X=H、CH3、F、Cl、Br、OH、OCH3)与SC2H4的硫转移反应进行了计算研究. 结果表明, 锗烯的基态是单重态, 取代基的电负性越强, 单-三态的能量差越大; 反应的活化能越高, 放热越少; 控制反应的因素是电子效应, 而不是立体效应; 该硫转移反应由两步组成, 第一步生成中间配合物, 是一个无势垒的放热过程, 第二步经过渡态生成产物. 并用组态混合模型对反应机理和势垒进行了解释. 同时讨论了该反应中环硫乙烷的C—S键解离过程.

Quantum Chemistry Study on the Abstraction Reaction of Germylene and Its Substituted Species with Thiirane

The potential energy surfaces for the abstraction reaction of germylene with thiirane have been char-acterized in detail using density functional theory (DFT). All the stationary points were determined at the B3LYP/6-311++G (d, p) level of the theory. The transition states both to the reactants and the product direction in the reaction paths were examined by using the intrinsic reaction coordinate (IRC). The major conclusion is as follows: the reaction is in two steps, (1) germylenes and thiirane form an intermediate complex through an exothermal reaction without any barrier; (2) the intermediate complexes isomerize to give the products. Furthermore, the stronger the π-donation is or the more electronegative the substituents are the bigger the ΔEST of X2Ge, the higher the activation energy for the abstraction reactions will be. In other words, it is the electronic factors, rather than the steric factors, that play a decisive role in the chemistry of the germylene species. A configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results.