Lu Xiuhui, Xu Yuehua, Yu Haibin, Wu Weirong
School of Chemistry and Chemical Engineering, Jinan University, Jinan, Shandong, 250022, People's Republic of China.
J Phys Chem A. 2005 Aug 11;109(31):6970-3. doi: 10.1021/jp0515075.
The mechanism of the cycloaddition reaction of forming a germanic hetero-polycyclic compound between singlet alkylidenegermylene and ethylene has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6-31G* method. From the surface energy profile, it can be predicted that the dominant reaction pathway for this reaction consists of three steps: the two reactants first form a three-membered ring intermediate INT1 through a barrier-free exothermic reaction of 35.4 kJ/mol; this intermediate then isomerizes to an active four-membered ring product P2.1 via a transition-state TS2.1 with a barrier of 57.6 kJ/mol; finally, P2.1 further reacts with ethylene to form the germanic hetero-polycyclic compound P3, for which the barrier is only 0.8 kJ/mol. The rate of this reaction path considerably differs from other competitive reaction paths, indicating that the cycloaddition reaction has an excellent selectivity.
采用MP2/6-31G方法研究了单重态亚烷基锗与乙烯形成锗杂多环化合物的环加成反应机理，包括对势能面上相关驻点的几何结构优化和振动分析。不同构象的能量通过CCSD(T)//MP2/6-31G方法计算。从表面能量剖面图可以预测，该反应的主要反应途径包括三个步骤：两种反应物首先通过35.4 kJ/mol的无势垒放热反应形成三元环中间体INT1；该中间体然后通过势垒为57.6 kJ/mol的过渡态TS2.1异构化为活性四元环产物P2.1；最后，P2.1进一步与乙烯反应形成锗杂多环化合物P3，其势垒仅为0.8 kJ/mol。该反应路径的速率与其他竞争反应路径有很大差异，表明环加成反应具有优异的选择性。
