The controlled synthesis of polyesters via epoxide/anhydride ring-opening copolymerization is a versatile and generally applicable method to make many sustainable polymers, but catalyst activities are limited and the required catalyst loadings are typically high. Here, novel heterodinuclear complexes, featuring Al(III)/M(I) (M = Na, K, Rb, Cs), show exceptional activities for phthalic anhydride and cyclohexene oxide copolymerization (catalyst = Al(III)/K(I), turnover frequency = 1072 h^–1, 0.25 mol % catalyst loading vs anhydride, 100 °C). The Al(III)/K(I) catalyst is also tolerant to low loadings, maintaining a good performance at 0.025 mol % catalyst vs anhydride loading and 0.005 mol % vs epoxide. It rapidly polymerizes other epoxide/anhydride combinations yielding various semi-aromatic, rigid, and/or functionalizable polyesters and also shows activity in carbon dioxide/epoxide copolymerizations. The results of structure–activity, X-ray crystallography, polymerization kinetics, and density functional theory investigations support a mechanism with chain growth alternation between the metals. The rate-limiting step is proposed to involve epoxide coordination at Al(III) with K(I) carboxylate attack. Future exploitation of abundant and inexpensive Group 1 metals to deliver synergic polymerization catalysts is recommended.

中文翻译：

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使用 Al(III) 和第 1 族金属的催化协同作用加速环氧化物和酸酐开环共聚反应

通过环氧化物/酸酐开环共聚可控合成聚酯是一种通用且普遍适用的方法，可用于制造许多可持续聚合物，但催化剂活性有限且所需的催化剂负载量通常很高。在这里，具有 Al(III)/M(I)（M = Na、K、Rb、Cs）的新型异双核配合物对邻苯二甲酸酐和氧化环己烯共聚（催化剂 = Al（III）/K（I） , 周转频率 = 1072 h ^–1, 0.25 mol % 催化剂负载对酸酐, 100 °C)。Al(III)/K(I) 催化剂也耐受低负载，在 0.025 mol% 催化剂与酸酐负载和 0.005 mol% 与环氧化物负载下保持良好的性能。它可以快速聚合其他环氧化物/酸酐组合，产生各种半芳族、刚性和/或可官能化聚酯，并且在二氧化碳/环氧化物共聚中也显示出活性。结构-活性、X 射线晶体学、聚合动力学和密度泛函理论研究的结果支持金属之间链增长交替的机制。建议限速步骤涉及 Al(III) 处的环氧化物配位与 K(I) 羧酸盐攻击。建议未来开发丰富且廉价的第 1 族金属以提供协同聚合催化剂。