Zwitterionic Design Principle of Nickel(II) Catalysts for Carbonylative Polymerization of Cyclic Ethers
Zwitterionic Design Principle of Nickel(II) Catalysts for Carbonylative Polymerization of Cyclic Ethers
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DOI：
10.1002/anie.201808507
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发表时间：
2018-10-22
影响因子：
16.6
通讯作者：
Jia, Li
中科院分区：
文献类型：
--
作者：
Dai, Yiwei;He, Shiyu;Jia, Li
两性离子结构是Ni-II配合物催化环醚羰基化聚合所必需的。Ni-II中心的阳离子电荷赋予Ni-酰基键足够的亲电性，使其与环醚反应，得到酰基-环醚氧鎓中间体，而配体中心的阴离子电荷确保所得氧鎓阳离子与Ni-O亲核试剂离子配对。目前的催化剂产生一氧化碳和环醚的非交替共聚物，并且当环氧乙烷和四氢呋喃都作为环醚单体存在时是最有效的。
Zwitterionic structure is necessary for Ni-II complexes to catalyze carbonylative polymerization (COP) of cyclic ethers. The cationic charge at the Ni-II center imparts sufficient electrophilicity to the Ni-acyl bond for it to react with cyclic ethers to give an acyl-cyclic ether oxonium intermediate, while the ligand-centered anionic charge ensures that the resultant oxonium cation is ion-paired with the Ni-0 nucleophile. The current catalysts give non-alternating copolymers of carbon monoxide and cyclic ethers and are the most effective when both ethylene oxide and tetrahydrofuran are present as the cyclic ether monomers.