A new family of well-defined cobalt complexes (–) bearing -bidentate chelate aldimine imidazolidine-2-imine/guanidine ancillary ligands were designed and successfully synthesized. All of the target metal complexes were structurally characterized by single-crystal X-ray diffraction analysis. It revealed that the Co atom adopted distorted tetrahedral coordination geometry and formed a unique six-membered chelate ring which exhibited structural distinctions with traditional N^N-based -diimine and -diimine Co complexes. In combination with a very low amount of EtAlCl (as low as 50 equiv.), these Co complexes exhibited high activity (up to 99 % yield within 6 hrs) and good thermal stability (up to 80 °C) in the coordination polymerizations of isoprene to afford -1,4/3,4-polyisoprenes with adjustable molecular weights (25.9–138.4 kg/mol) and -1,4 contents (64.7–73.3 %). The different substituents on these Co catalysts also exerted influence on catalytic behaviors, chain microstructures, and polymer properties. This study represents the first example of imidazolidine-imine/guanidine analog ligated Cobalt complexes for the polymerization of isoprene.

中文翻译：

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用于异戊二烯聚合的具有 N,N-二齿醛亚胺咪唑烷-2-亚胺/胍辅助配体的稳健钴催化剂


设计并成功合成了一个新的明确的钴配合物（-）家族，其带有双齿螯合醛亚胺咪唑烷-2-亚胺/胍辅助配体。所有目标金属配合物均通过单晶 X 射线衍射分析进行了结构表征。结果表明，Co原子采用扭曲的四面体配位几何形状，形成独特的六元螯合环，与传统的N^N基-二亚胺和-二亚胺Co配合物表现出结构上的区别。与极少量的 EtAlCl（低至 50 当量）相结合，这些 Co 配合物在配位聚合中表现出高活性（6 小时内产率高达 99%）和良好的热稳定性（高达 80 °C）。异戊二烯生成具有可调分子量 (25.9–138.4 kg/mol) 和 -1,4 含量 (64.7–73.3%) 的 -1,4/3,4-聚异戊二烯。这些Co催化剂上的不同取代基也对催化行为、链微观结构和聚合物性能产生影响。这项研究代表了咪唑烷-亚胺/胍类似物连接的钴配合物用于异戊二烯聚合的第一个例子。