The catalytic coupling and polymerization of CO 2 and epoxides has been studied for over 50 years. While traditionally dominated by catalytic systems containing cobalt, chromium, and zinc, the use of iron catalysts has emerged in the past 10 years. This review provides an overview of the homogeneous iron-catalyzed transformations of carbon dioxide and epoxides to yield cyclic and/or polycarbonates. It is important to note the potential for cyclic carbonates to be used as monomers for polymer formation via transesterification or by ring-opening polymerization in some cases, e.g., cyclohexene carbonate. Typical catalytic systems are composed of a Lewis acidic iron center and an anionic nucleophilic source, either through an anionic group weakly bound to the metal center or the addition of an external cocatalyst, cooperatively described as a binary catalytic system. This review is divided into two sections: (1) iron catalysts for cyclic carbonates and (2) iron catalysts for polycarbonates. At the end of each section, a table summarizes each catalytic system and the reaction conditions utilized in an attempt to provide a clearer comparison across the literature. Focus is given to highlighting differences in product selectivity, reaction conditions, and relative amounts of cocatalyst used. The use of iron catalysts in CO 2 /epoxide chemistry has been less explored compared with zinc, cobalt, and chromium catalysts. This review highlights recent examples including iron complexes that deoxygenate epoxides in situ and geometry-dependent selectivity towards either polycarbonate or cyclic carbonate production. Reaction conditions (temperature, CO 2 pressure, and amount of nucleophilic cocatalyst) and catalyst structure are all critical in accessing efficient catalysis for polycarbonate formation.

中文翻译：

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CO2 和环氧化物的铁催化反应生成环状和聚碳酸酯

CO 2 和环氧化物的催化偶联和聚合已经研究了 50 多年。虽然传统上以含钴、铬和锌的催化系统为主，但铁催化剂的使用在过去 10 年中已经出现。这篇综述概述了二氧化碳和环氧化物的均相铁催化转化，以产生环状和/或聚碳酸酯。重要的是要注意环状碳酸酯可用作通过酯交换或在某些情况下通过开环聚合形成聚合物的单体，例如碳酸环己烯。典型的催化体系由路易斯酸性铁中心和阴离子亲核源组成，通过弱结合金属中心的阴离子基团或添加外部助催化剂，合作描述为二元催化系统。本综述分为两部分：（1）环状碳酸酯的铁催化剂和（2）聚碳酸酯的铁催化剂。在每个部分的末尾，一个表格总结了每个催化系统和所使用的反应条件，以试图在文献中提供更清晰的比较。重点是突出产品选择性、反应条件和所用助催化剂的相对量方面的差异。与锌、钴和铬催化剂相比，在 CO 2 /环氧化物化学中使用铁催化剂的研究较少。这篇综述重点介绍了最近的例子，包括原位使环氧化物脱氧的铁配合物，以及对聚碳酸酯或环状碳酸酯生产的几何依赖性选择性。反应条件（温度、CO 2 压力、