Palladium/IzQO-Catalyzed Coordination–Insertion Copolymerization of Ethylene and 1,1-Disubstituted Ethylenes Bearing a Polar Functional Group

Coordination–insertion copolymerization of ethylene with 1,1-disubstituted ethylenes bearing a polar functional group, such as methyl methacrylate (MMA), is a long-standing challenge in catalytic polymerization. The major obstacle for this process is the huge difference in reactivity of ethylene versus 1,1-disubstituted ethylenes toward both coordination and insertion. Herein we report the copolymerization of ethylene and 1,1-disubstituted ethylenes by using an imidazo­[1,5-a]­quinolin-9-olate-1-ylidene-supported palladium catalyst. Various types of 1,1-disubstituted ethylenes were successfully incorporated into the polyethylene chain. In-depth characterization of the obtained copolymers and mechanistic inferences drawn from stoichiometric reactions of alkylpalladium complexes with methyl methacrylate and ethylene indicate that the copolymerization proceeds by the same coordination–insertion mechanism that has been postulated for ethylene.乙烯与带有极性官能团的1,1-二取代乙烯（如甲基丙烯酸甲酯（MMA））的配位插入共聚，长期以来都是催化聚合领域的经典难题。该过程的主要阻碍在于，乙烯与1,1-二取代乙烯在配位和插入步骤上的反应活性存在巨大差异。本文报道了一种基于咪唑并[1,5-a]喹啉-9-醇盐-1-亚基负载钯催化剂的乙烯与1,1-二取代乙烯共聚方法。多种类型的1,1-二取代乙烯均可成功接入聚乙烯链中。对所得共聚物的深入表征，以及通过烷基钯配合物与甲基丙烯酸甲酯、乙烯的计量反应所推导的机理推断表明，该共聚反应遵循此前针对乙烯所提出的配位插入机理。