“…Further modification to these catalysts by Brookhart, Jordan, Nozaki, Shimizu, Carrow, Chen, Cai, Jian, Li, etc., led to enhanced catalytic properties. Reviews have been extensively summarized based on catalyst classifications by Chen [11,[28][29][30], Jian [10,31,32], Nozaki [2,33], Li [34], Cao [35], etc., including advanced catalytic tuning strategies containing external stimuli [36] and secondary interactions [37][38][39][40], the coordination-insertion mechanism [3,41] containing the monomer poisoning effect [42] and the functions of custom-made polar monomers [31,32]. Except for the most challenging substrates such as fundamental polar monomers, a variety of nickel catalysts with bidentate ligands have also been developed for the effective copolymerization of olefins with nonvinyl polar monomers [33], including disubstituted ethene comonomers, ester-disubstituted carbene and CO [43][44][45][46], e.g., the nonalternating copolymerization of ethylene with CO to incorporate in-chain keto groups in polyethylene chains with high molecular weight while retaining desirable material properties [44].…”