Heterometallic cooperativity is an emerging strategy to elevate polymerisation catalyst performance. Here, we report the first heterotrimetallic Na/Zn₂ and K/Zn₂ complexes supported by a ProPhenol ligand, which deliver “best of both” in cyclic ester ring-opening polymerisation, combining the outstanding activity (Na/K) and good control (Zn₂) of homometallic analogues. Detailed NMR studies and density-functional theory calculations suggest that the Na/Zn₂ and K/Zn₂ complexes retain their heterometallic structures in the solution-state. To the best of our knowledge, the K/Zn₂ analogue is the most active heterometallic catalyst reported for rac-lactide polymerisation (k_obs = 1.7 × 10⁻² s⁻¹), giving activities five times faster than the Na/Zn₂ complex. These versatile catalysts also display outstanding performance in ε-caprolatone and δ-valerolactone ring-opening polymerisation. These studies provide underpinning methodologies for future heterometallic polymerisation catalyst design, both in cyclic ester polymerisation and other ring-opening (co)polymerisation reactions.

中文翻译：

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结合碱金属和锌以利用环酯开环聚合中的杂金属协同性

杂金属的协同作用是提高聚合催化剂性能的新兴策略。在这里，我们报道了首个由ProPhenol配体支持的杂三金属Na / Zn ₂和K / Zn ₂配合物，它们在环状酯开环聚合中提供了“两者中的最佳”，结合了出色的活性（Na / K）和良好的控制性（Zn ₂）的同金属类似物。详细的NMR研究和密度泛函理论计算表明，Na / Zn ₂和K / Zn ₂配合物在溶液态保留其杂金属结构。据我们所知，K / Zn ₂类似物是报道的最活跃的rac杂金属催化剂-丙交酯聚合（k _obs = 1.7×10 ^-2 s ^-1），其活性比Na / Zn ₂络合物快五倍。这些多功能催化剂还在ε-己内酯和δ-戊内酯开环聚合反应中显示出卓越的性能。这些研究为环状酯聚合反应和其他开环（共）聚合反应中未来的杂金属聚合催化剂设计提供了基础方法。