Catalytic Coupling of Cyclopentene Oxide and CO2 Utilizing Bifunctional (salen)Co(III) and (salen)Cr(III) Catalysts: Comparative Processes Involving Binary (salen)Cr(III) Analogs
Catalytic Coupling of Cyclopentene Oxide and CO2 Utilizing Bifunctional (salen)Co(III) and (salen)Cr(III) Catalysts: Comparative Processes Involving Binary (salen)Cr(III) Analogs
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DOI：
10.1021/cs4008667
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发表时间：
2013-12-01
期刊：
影响因子：
12.9
通讯作者：
Wilson, Stephanie J.
中科院分区：
文献类型：
--
作者：
Darensbourg, Donald J.;Chung, Wan-Chun;Wilson, Stephanie J.
以前，由氧化环戊烯和二氧化碳的交替共聚产生的聚碳酸酯已被证明易于再循环成其单体，因此提供了生产这种聚合物材料的可持续途径。这反过来又需要开发这种共聚物的有效合成方法。使用二元（salen）CrX/PPNX催化剂体系，脂环族环氧化物、氧化环己烯（CHO）和氧化环戊烯（CPO）与CO2的偶联反应显示出提供了显著不同的产物选择性。也就是说，尽管CHO/CO2的偶联提供>99%的完全交替共聚物的选择性，但在相同条件下，CPO/CO2产生>99%的顺式-环戊烯碳酸酯的选择性。通过对比，使用双官能（R，R）-（salen）M（III）催化剂（M = Cr和Co）用于环戊烯氧化物和二氧化碳的偶联反应导致高度选择性合成良好可控的窄分布分子量共聚物。虽然发现铬催化剂的活性低于其钴类似物，但其显示出更热稳定，因此，反应可以在较高温度下进行，而对共聚物生产的选择性几乎没有牺牲。所得聚（碳酸环戊烯酯）的Tg测定为84.5 ℃。
Previously, the polycarbonate produced from the alternating copolymerization of cyclopentene oxide and carbon dioxide has been demonstrated to readily be recyclable to its monomers, hence affording a sustainable route to the production of this polymeric material. This, in turn, necessitates the development of effective synthetic methods for this copolymer. Coupling reactions of the alicyclic epoxides, cyclohexene oxide (CHO) and cyclopentene oxide (CPO), with CO2 were shown to provide grossly different product selectivities utilizing binary (salen)CrX/PPNX catalyst systems. That is, whereas the coupling of CHO/CO2 affords >99% selectivity for completely alternating copolymers, under identical conditions, CPO/CO2 yields >99% selectivity for cis-cyclopentene carbonate. By way of contrast, employing bifunctional (R,R)-(salen)M(III) catalysts (M = Cr and Co) for the coupling reactions of cyclopentene oxide and carbon dioxide results in the highly selective synthesis of well-controllable, narrowly distributed molecular weights copolymers. Although the chromium catalyst was found to be less active than its cobalt analog, it was shown to be thermally more stable, and hence, the reaction could be carried out at higher temperatures with little sacrifice in selectivity for copolymer production. The T-g of the resulting poly(cyclopentene carbonate) was determined to be 84.5 degrees C.