锗烯与乙烯环加成反应的理论研究

Theoretical Study on the Cycloaddition Reaction of Germylene and Ethylene

用RHF/6-31G^(?)解析梯度方法研究了单重态锗烯与乙烯环加成反应的机理,用二级微扰方法对各构型的能量进行了相关能校正,并用统计热力学方法和过渡态理论计算了该反应在不同温度下的热力学函数的变化和动力学性质.结果表明,此反应历程由两步组成:1)锗烯与乙烯生成了一中间配合物,是-无势垒的放热反应,2)中间配合物异构化为产物锗杂环丙烷,此步势垒经零点能校正后为26.9kJ·mol^(-1)(MP2/6-31G^(?)//6-31G^(?));从热力学和动力学的综合角度考虑,该反应在200～300K温度下进行为宜,如此,反应既有较大的自发趋势和平衡常数,又具有较快的反应速率.

The mechanism of the cycloaddition reaction of singlet germylene with ethylene has been studied by RHF/6 - 31G* gradient method. The electron correlation energies of all the structures are calculated by using second- order Moller - Plesset perturbation theory(MP2) . We have also calculated the changes of thermodynamic functions and the quality of kinetic properties for this reaction at different temperatures by using statistical thermodynamics method and transition state theory,The results show that this reaction proceeds in two steps: (1) germylene and ethylene form an intermediate complex through a kind of exothermal reaction without any barrier; (2) the intermediate complex isomerized to give the product, after being corrected for the zero point energies, the barrier is 26. 9kJ·mol-1 ( MP2/6 -31G*//6 - 31G* ). In view of dynamics and thermodynamics, it is between 200 - 300K that the reaction will have not only the larger spontaneous tendency and equilibrum constant but also higher reaction rate.