新型烯烃复分解催化剂催化反应机理的理论研究

DFT Studies on the Mechanisms for Metathesis Reaction Catalyzed by the New Type of Olefin Metathesis Catalysts

采用密度泛函理论(DFT),计算研究了闭环烯烃复分解反应的机理,该反应在新型邻取代苯二酚做配体的催化剂催化下进行。在BP86水平下,优化反应路径的中间体,求得反应途径的系列过渡态,并通过振动分析和内禀反应坐标(IRC)加以确认。基于此,确定了此反应的可能反应路径:首先五配位的金属催化剂释放出吡啶配体,然后1,6-己二烯双键从N-杂环卡宾的侧面配位到金属催化剂上,形成四方锥的金属卡宾化合物;金属卡宾经过两次[2+2]环加成反应和逆环加成反应生成产物环戊烯。此反应控速步为第二次逆环加成生成金属卡宾中间体的过程,能垒是80.9 kJ·mol-1。

The detailed mechanisms of ring closing metathesis reaction （RCM） catalyzed by pyrocatechol lig- and catalysts were studied using density functional theory （DFT）. All of the transition states and intermediates were also performed with the BP86 method. Vibration analysis and intrinsic reaction coordinates （IRC） were calculated for the transition states to confirm that such structures indeed connect two relevant minima. The computational re- suits give a mechanism as followings. The reaction begins with the dissociation of pyridine ligand from Ru penta-co- ordinated catalyst. Subsequently, 1,6-hexadiene coordinates to the Ru center through the side-bound pathway, generating a metal carbene complex with tetragonal-pyramid geometry. Then, twice [ 2 ＋ 2 ] addition and retro-cy- cloaddition reaction occur, giving the product cyclopentene. The rate-determining stage of the entire reaction is found to be the second inverse cycloaddition, which takes place with a barrier of 80. 9 kJ· mol- 1.