螯合型羰基铑配合物催化甲醇羰基化反应的机理研究

报道了螯合型正方平面羰基铑配合物催化甲醇羰基化反应的机理研究. 通过含有两种与铑具有不同配位能力的授体的配体, 与四羰基二氯二铑形成螯合型正方平面阳离子配合物. 研究证明, 该类配合物在催化甲醇羰基化反应过程中, 其活性物种区别于文献报道的Rh(CO)2I2]－阴离子. 配合物中铑与吡啶环上共轭N形成的N→Rh配键, 在羰基化反应过程中并非通常认为的断裂而是形成新的活性物种, 即配体与铑作为整体参与了CH3I的氧化加成及CH3COI的生成过程. 通过对相应的聚合物配体铑催化剂的研究, 进一步证实了这个反应机理. 这一结果, 对该类催化剂分子设计, 以及克服其工业使用中的催化剂沉淀失活等现象均有重要意义.

Mechanism of Methanol Carbonylation Catalyzed by Chelated Carbonyl Rhodium Complex

The mechanism of methanol carbonylation catalyzed by a chelated square planar carbonyl rhodium complex was studied. The chelated square planar cationic complex was formed via the coordination of Rh(CO)2Cl]2 with the ligand, which has two donors with different coordination capacity. Experimental results showed that the active species of the catalyst in methanol carbonylation differed from Rh(CO)2I2]－ reported in other literature. Other than conventional concept, the N→Rh bond, formed by rhodium in the complex and nitrogen at pyridine ring in the ligand, did not break in the course of the carbonylation reaction, but formed into new active species instead, i.e., the ligand and rhodium as a whole participated in the oxidative addition of CH3I and the formation of CH3COI. Via the investigation of the corresponding catalyst with polymer ligand, the mechanism was further demonstrated. The result is of significance towards the molecular design of such catalysts, and the solution to their deactivation due to precipitation in industrial application as well.