Tuning the Selectivity of the Oxetane and CO2 Coupling Process Catalyzed by (Salen)CrCl/n-Bu4NX: Cyclic Carbonate Formation vs Aliphatic Polycarbonate Production
Tuning the Selectivity of the Oxetane and CO2 Coupling Process Catalyzed by (Salen)CrCl/n-Bu4NX: Cyclic Carbonate Formation vs Aliphatic Polycarbonate Production
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DOI：
10.1021/ma100896x
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发表时间：
2010-07-27
期刊：
影响因子：
5.5
通讯作者：
Moncada, Adriana I.
中科院分区：
文献类型：
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作者：
Darensbourg, Donald J.;Moncada, Adriana I.
（salen）(CrCl)-Cl-III配合物I，（1,2-环己二胺-N，N'-双（3,5-二叔丁基水杨基）-氯化铬），在N- bu4nx存在下(X = Br， I, Cl, N-3，在配合物I和n-Bu4NBr作为助催化剂存在的情况下，氧辛烷和CO2的偶联反应过程的选择性被有效地调整为直接由预成型碳酸三亚甲基（TMC）的均聚反应生成聚碳酸酯。值得注意的是，在此条件下获得的碳酸盐键的数量非常高（>99%）。ESI质谱分析对参与偶联反应的初始催化物质进行了研究。揭示了（salen）CrCl用两种等量的n-Bu4NBr助催化剂处理后形成的三种可能阴离子的Schlenk（配体重分配）平衡。该催化体系完全由氧乙烷和CO2在温和反应条件下（50℃和10 bar CO2）通过主要涉及金属醇氧化物中间体的反向反应过程偶联产生碳酸三亚甲基
The (salen)(CrCl)-Cl-III complex I, (1,2-cyclohexanediamino-N,N'-bis(3,5-ditert-butylsalicylidene)-chromium(III) chloride), in the presence of n-Bu4NX (X = Br, I, Cl, N-3, NCO) as cocatalyst has been shown to be an effective catalytic system for the coupling of oxetane and CO2 providing the corresponding aliphatic polycarbonate with small quantities of et her linkages at 110 degrees C The selectivity of the oxctane and CO2 coupling process has been effectively tuned for the formation of polycarbonate produced directly from the homopolymerization of preformed trimethylene carbonate (TMC), in the presence of complex I along with n-Bu4NBr as cocatalyst, at temperatures lower than 80 degrees C Notably, under these conditions the amount of carbonate linkages obtained was remarkably high (>99%) An investigation of the initial catalytic species involved in the coupling reaction was performed by ESI mass spectral analysis, revealing a Schlenk (ligand redistribution) equilibrium of the three possible anions formed after treatment of the (salen)CrCl with two equivalents of n-Bu4NBr cocatalyst This catalytic system afforded trimethylene carbonate exclusively from the coupling of oxetane and CO2 at mild reaction conditions (50 degrees C and 10 bar of CO2) via a backbiting process involving mostly a metal alkoxide intermediate