氢甲酰化反应过渡金属络合催化剂有机膦配体调变效应的理论研究

应用量子化学半经验PM3计算方法,对十几种不同结构的有机膦配体结构做了计算,研究了有机膦配体的磷原子的电荷,分析了有机膦配体对中心金属原子的作用原理,提出了一种用于各种改性膦配体对金属有机催化剂催化活性与选择性影响大小的估算方法。计算结果表明, (1)有机膦配体上用于配位的磷原子电子电荷越大,配体的授电子能力越弱,与中心金属原子形成的配位化合物对氢甲酰化反应活性越高; (2)有机膦配体的三个取代基所形成的截面面积是在氢甲酰化催化反应中影响同一类催化剂选择性的一个重要因素,有机膦配体三个取代基所形成的截面面积S越大,反应的选择性就越好;(3)结合氢甲酰化催化反应速率常数k值和线性率n值, 对磷原子电荷Q值和S面积作了回归分析, 由回归方程可知, 有机膦配体并不是单独地以电子效应或立体效应来影响有机金属络合物的活性和选择性的, 两者是协同作用的。

A theoretical study on electronic and steric effects of phosphorus ligands in homogeneous catalysts

A semi-empirical molecular orbital calculation, PM3 method has been employed to study the relation between the charge ρ of P atom in phosphorus ligands and the activity of homogeneous catalysts related to hydroformylation, and also to study the relation between the area S of three substituents bonding with P atom in phosphorus ligands and the selectivity of catalysts related to hydroformylation. The results indicate that, for the catalysts modified by phosphorus ligands which have semilar structural characters , the P atom charge Q and the area S have a good linear relationship with the activity and selectivity of homogeneous catalyst s related to hydroformylation , respectively. Here a reasonable method to predict the activity and selectivity of homogeneous catalyst s modified by phosphorus ligands by means of quantum chemist ry calculation is provided.