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首页> 外文期刊>Chemistry: A European journal >Mechanistic Aspects of the Metal Catalyzed Alternating Copolymerization of Epoxides and Carbon Monoxide
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Mechanistic Aspects of the Metal Catalyzed Alternating Copolymerization of Epoxides and Carbon Monoxide

机译：金属催化的环氧化物和一氧化碳交替共聚的机理

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摘要

The cobalt-catalyzed alternating copolymerization of epoxides and CO is a novel,direct approach to aliphatic polyesters,such as poly(hy-droxybutyrate)(PHB).This reaction was found to be catalyzed by Ph_3Si-[Co(CO)_4](4)and pyridine affording in a first step the stable mono-insertion product Ph_3Si-O-CH(CH_3)-CH_2-CO-Co(CO)_4(5).However,a profound mechanistic understanding,especially of the role of pyridine as the key component for the polymerization reaction was missing.ATR-IR online monitoring under catalytic conditions and DFT calculations were used to show that an acylpyridinium cation is formed by cleavage of the cobalt-acyl bond of 5 in the presence of pyridine.The Lewis acid thus generated activates the next incoming epoxide monomer for ring opening through[Co(CO)_4]~-.The catalytic cycle is completed by a subsequent CO insertion in the new cobalt- alkyl bond.The calculations are used to explore the energetic hypersurface of the polymerization reaction and are complemented by extended experimental investigations that also support the mechanistic hypotheses.
机译：钴与环氧化物的钴交替共聚是一种新颖，直接的方法，用于脂族聚酯，如聚羟基丁酸酯（PHB）。该反应被Ph_3Si- [Co（CO）_4]（ 4）和吡啶，第一步提供稳定的单插入产物Ph_3Si-O-CH（CH_3）-CH_2-CO-Co（CO）_4（5）。但是，对机理的理解非常深刻，尤其是吡啶的作用催化条件下的ATR-IR在线监测和DFT计算表明，吡啶存在下裂解5的钴-酰基键形成酰基吡啶鎓阳离子。如此生成的酸通过[Co（CO）_4]〜-激活下一个进入的环氧化物单体。通过新的钴烷基键中随后的CO插入来完成催化循环。该计算用于探索高能超表面聚合反应，并辅以ext结束了也支持机理假说的实验研究。

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