Nickel reaction with polar monomers

While cationic catalysts 16 are an effective and important class of catalysts, their electrophilicity still hampers their ability to tolerate polar functions. The less electrophilic neutral 17-19 and zwitterionic 20 nickel catalysts have been examined in an effort to enhance compatibility with polar monomers and co-monomers. Again, bulky ligands are necessary not only to promote olefin insertion, but also to discourage ligand-redistribution reactions resulting in deactivated bis-ligand complexes and decomposition products. For a typical neutral Ni(ii) system, such as 19, Brookhart has shown that the mechanism involves (i) associative displacement of the PR3 ligand by ethylene to... 

Twieg and coworkers, reported preparation of poly(norbomene) copolymers functionalized with nonlinear optical chromophore side groups. Use was made of (ri -toluene)Ni(C6F5)2, catalyst in the polymerization of norbomene. The nickel complex used to polymerize the norbomene monomers is tolerant to many functional groups found in nonlinear optical chromophores. On the other hand, nitriles and amines other than trisubstituted amines strongly inhibit the reaction. A copolymer of hexylnorbomene and a norbomene-functionalized Disperse Red I chromophore was scaled up and studied in detail. Initial studies indicate that electric field poling is effective but that relaxation of polar order in the poly(norbomene) is faster than in a comparable methacrylate copolymer. The copolymer can be illustrated as follows ... 

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