Co(III)/Alkali-Metal(I) Heterodinuclear Catalysts for the Ring-Opening Copolymerization of CO2 and Propylene Oxide,Journal of the American Chemical Society

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Co(III)/Alkali-Metal(I) Heterodinuclear Catalysts for the Ring-Opening Copolymerization of CO2 and Propylene Oxide
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-10-27 , DOI: 10.1021/jacs.0c07980
Arron C Deacy ₁ , Emma Moreby ₁ , Andreas Phanopoulos ₁ , Charlotte K Williams ₁

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The ring-opening copolymerization of carbon dioxide and propene oxide is a useful means to valorize waste into commercially attractive poly(propylene carbonate) (PPC) polyols. The reaction is limited by low catalytic activities, poor tolerance to a large excess of chain transfer agent, and tendency to form byproducts. Here, a series of new catalysts are reported that comprise heterodinuclear Co(III)/M(I) macrocyclic complexes (where M(I) = Group 1 metal). These catalysts show highly efficient production of PPC polyols, outstanding yields (turnover numbers), quantitative carbon dioxide uptake (>99%), and high selectivity for polyol formation (>95%). The most active, a Co(III)/K(I) complex, shows a turnover frequency of 800 h–1 at low catalyst loading (0.025 mol %, 70 °C, 30 bar CO2). The copolymerizations are well controlled and produce hydroxyl telechelic PPC with predictable molar masses and narrow dispersity (Đ < 1.15). The polymerization kinetics show a second order rate law, first order in both propylene oxide and catalyst concentrations, and zeroth order in CO2 pressure. An Eyring analysis, examining the effect of temperature on the propagation rate coefficient (kp), reveals the transition state barrier for polycarbonate formation: ΔG‡ = +92.6 ± 2.5 kJ mol–1. The Co(III)/K(I) catalyst is also highly active and selective in copolymerizations of other epoxides with carbon dioxide.

中文翻译：

Co(III)/碱金属(I)异双核催化剂用于CO2和环氧丙烷的开环共聚

二氧化碳和环氧丙烷的开环共聚是将废物转化为具有商业吸引力的聚（碳酸亚丙酯）（PPC）多元醇的有用方法。该反应受到催化活性低、对大量过量链转移剂的耐受性差以及容易形成副产物的限制。在此，报道了一系列包含异双核 Co(III)/M(I) 大环配合物（其中 M(I) = 第 1 族金属）的新型催化剂。这些催化剂显示出 PPC 多元醇的高效生产、出色的产率（周转数）、定量二氧化碳吸收 (>99%) 以及多元醇形成的高选择性 (>95%)。最活跃的是 Co(III)/K(I) 络合物，在低催化剂负载量（0.025 mol%、70 °C、30 bar CO2）下显示出 800 h–1 的周转频率。共聚反应得到良好控制，产生具有可预测摩尔质量和窄分散度 (Đ < 1.15) 的羟基遥爪 PPC。聚合动力学显示二阶速率定律，环氧丙烷和催化剂浓度均为一阶，CO2 压力为零阶。 Eyring 分析检查了温度对传播速率系数 (kp) 的影响，揭示了聚碳酸酯形成的过渡态势垒：ΔG‡ = +92.6 ± 2.5 kJ mol–1。 Co(III)/K(I)催化剂在其他环氧化物与二氧化碳的共聚中也具有高活性和选择性。

更新日期：2020-10-27

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