反式-二氯四吡啶合钌催化CO_2制备碳酸丙烯酯机理探讨

Investigation of Reaction Mechanism for Formation Propylene Carbonate from CO_2 Catalyzed by Trans-RuCl_2(py)_4

在研究反式-二氯四吡啶合钌[trans-RuCl2(py)4]催化二氧化碳与环氧丙烷反应制备碳酸丙烯酯的基础上,利用电喷雾质谱(ESI-MS)进一步分析了催化反应过程中催化剂的结构变化,并通过对trans-RuCl2(py)4的晶体结构数据分析、键能计算等手段,探讨了trans-RuCl2(py)4催化反应机理.结果显示,trans-RuCl2(py)4催化二氧化碳和环氧丙烷反应,首先是通过环氧丙烷与trans-RuCl2(py)4中的氯进行配体交换引发的,发生配体交换的氯离子作为亲核试剂进攻环氧丙烷开环,二氧化碳插入Ru-O键,继而进行分子内关环、消去反应生成碳酸丙烯酯.

Based on research of the coupling reaction of CO2 and propylene oxide to afford propylene carbonate catalyzed by trans-dichlorotetrapyridineruthenium[trans-RuCl2（py）4],the reaction mechanism has been studied by means of electrospray ionization mass spectrometry（ESI-MS）,crystal structure analysis and calculating bond-energ of trans-RuCl2（py）4.Experimental results suggested that the initial coordination of propylene oxide is likely to occur first through the chloride ligand replacement in trans-RuCl2（py）4;a nucleophilic attack of the chloride anion on the less sterically hindered-carbon atom of the coordinated propylene oxide is responsible for the epoxide ring-opening;CO2 is succeedingly inserted into the Ru-O bond and ring-closure happens subsequently yielding the cyclic carbonate.