Dimethyl pyrocarbonate (dmpc) [dimethyl µ-oxo-bis(dioxocarbonate)] and diethyl pyrocarbonate (depc) were catalytically decomposed to dimethyl and diethyl carbonate respectively and carbon dioxide in the presence of [CoL(OR)]+ [L = cis,cis-1,3,5-tris(E,E-cinnamylideneamino)cyclohexane, R = methyl or ethyl] which we propose to be generated in situ during reaction in dichloromethane. The activity of the catalyst is undiminished after 60 000 turnovers. In both cases the catalytic rate enhancement for the decomposition is in excess of 107 dm3 molâ1 of catalyst. The catalytic process follows MichaelisâMenten type kinetics and kobs is 2.2(2) sâ1 for dmpc decomposition and 1.3(2) sâ1 for depc decomposition. Activation energies for the catalytic decomposition are Edmpc = 113(5) and Edepc = 120(11) kJ molâ1. A mechanism involving cobalt-bound alkoxide attack on dialkyl pyrocarbonate is proposed. The crystal structure of [CoL(Cl)] BPh4 has been determined by single-crystal X-ray diffraction.
二甲基过
碳酸酯(dmpc)[二甲基μ-氧基双(二氧
碳酸酯)]和
二乙基过
碳酸酯(depc)在[CoL(OR)]+的存在下催化分解为二甲基和
二乙基碳酸酯以及
二氧化碳,其中[L = cis,cis-1,3,5-三(E,E-肉桂基
氨基)
环已烷,R = 甲基或乙基],我们假设该物质是在反应过程中在
二氯甲烷中原位生成的。催化剂在经历60,000次循环后活性未减。在这两种情况下,分解的催化速率增加超过107 dm³ mol⁻¹的催化剂。催化过程遵循Michaelis-Menten型动力学,dmpc分解的kobs为2.2(2) s⁻¹,而depc分解的kobs为1.3(2) s⁻¹。催化分解的活化能分别为Edmpc = 113(5)和Edepc = 120(11) kJ mol⁻¹。提出一种涉及
钴配位烷氧基对二烷基过
碳酸酯攻击的机制。[CoL(Cl)] BPh4的晶体结构通过单晶X射线衍射法确定。