Simulation of Selective Chemical Reactions and Theoretical Elucidation of their Mechanisms.

为了分析过渡金属络合物催化选择性反应的机理，为催化剂的设计提供有用的信息，我们采用量子力学和分子力学计算相结合的方法，对几个模型化学反应进行了理论计算。模型反应有：1)钯与联苯并二磷酸盐配合物催化的丙烯与一氧化碳的改性共聚合；2)Sm配合物催化的丙烯等规聚合；3)Rh-联二磷酸盐催化的氢甲酰化反应。对于第一个反应，我们首先用密度泛函方法研究了丙烯插入Pd(CoCH_3)(PH_3)(P(OH)_3)+的PdC键，以阐明反应机理，并用MO-THEN-MM方法研究了联苯并膦配体的再选择性和立体选择性。我们发现，BINAPHOS配体的立体效应实际上控制了立体选择性和区域选择性。在取代三茂铁烷基络合物Sm-C键插入丙烯的MO-THEN-MM计算中，我们发现丙烯插入是等规性的，与d嵌段过渡金属络合物催化的反应不同，二次插入更有利。不同的控制机制是可操作的。

In order to analyze the mechanism of selective reactions catalyzed by transition metal complexes and obtain useful information on devising catalysts, we have performed theoretical calculations of several model chemical reactions using the methods combining quantum mechanical and molecular mechanics calculations. The model reactions are 1) altering copolymerization of propylene with carbon monoxide catalyzed by Pd complexes with BINAPHOS ligand, 2) isotactic propylene polymerization catalyzed by a Sm complex, and 3) hydroformylation catalyzed by Rh-BINAPHOS catalysts. As to the first reaction, we first studied with the DFT method the propylene insertion into the PdC bond of Pd(COCH_3)(PH_3)(P(OH)_3)+ to clarify the reaction mechanism and with the MO-then-MM method the retio- and stereoselectivity due to the BINAPHOS ligand. We found that the steric effect due to the BINAPHOS ligand actually controls the stereo- and regioselectivity. In the MO-then-MM calculations of propylene insertion into the Sm-C bond of substituted samarocene alkyl complex, we have found that the propylene insertion would be isotactic, and different from the reaction catalyzed by the d block transition metal complexes, secondary insertion is more favorable. The different control mechanism is operational.