烯烃连续插入和碳氢活化的对比理论研究

Comparative Theoretical Study on Continuous Olefin Insertion and Hydrocarbon Activation

本论文使用密度泛函的方法,对2-乙基吡啶与异戊二烯反应过程中异戊二烯的连续插入和碳氢活化路径进行了详细的理论研究。计算表明,相比于异戊二烯的配位,由于2-乙基吡啶的强配位能力,后者形成的配位络合物能量更低,结构更加稳定;与两分子异戊二烯插入后的2-乙基吡啶的碳氢键活化过程相比,连续三分子异戊二烯插入过程需克服更高的能垒,动力学及热力学上更为不利。

In this paper,the density functional theory studies on the continuous isoprene insertion and hydrocarbon activation have been conducted for the direct C(sp 2)-H alkylation of 2-ethylpyridine with isoprene catalyzed by a cationic half-sandwich yttrium alkyl complex.The calculations results support the mechanism based on experiments.Compared with isoprene coordination,due to the strong coordination ability of 2-ethylpyridine,the latter forms a coordination complex with lower energy and more stable structure.By comparison with the carbon-hydrogen bond activation process,one or two isoprene molecules insertion occurs more easily,which is in line with the experimental observation.However,the continuous three-molecule isoprene insertion process needs to overcome a higher energy barrier,which is more unfavorable both kinetically and thermodynamically.