Developing Neutral Bidentate (N,O) Nickel(II) Catalysts for Ethylene Homo- and Copolymerization

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  • March 20, 2019
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  • Zhang, Lei
    • Affiliation: College of Arts and Sciences, Department of Applied Physical Sciences, Materials Science Graduate Program
Abstract
  • Research on polymerizations catalyzed by late metal complexes has been rejuvenated since our lab reported cationic 9-diimine Ni/Pd catalysts which are active to polymerize ethylene into high molecular weight polymers with unique branched microstructures. Compared with early metals, the reduced oxophilicity of late metals has also enabled these catalysts to copolymerize ethylene with polar olefins. Neutral coordinated bidentate Ni(II) catalysts are expected to exhibit enhanced polar group tolerance compared with their cationic counterparts, due to the weakened metal-oxygen bond. New neutral (N,O)Ni(II) catalysts, each of which has a bulky N-aryl group have been reported and studied for ethylene homoand copolymerization. Chapter 2 describes the synthesis, characterization and polymerization studies of new neutral anilinoenone-based (N,O)Ni(II) catalysts having a strong electron-withdrawing trifluoromethyl group. These catalysts are active for ethylene polymerization to form branched polymer in the presence of an activator. Changes in the substitution pattern affect the catalytic activities and polymer properties. Polymerization results are compared and discussed. Chapter 3 presents mechanistic investigations of ethylene insertion and coordination with neutral anilinoenone (N,O)Ni(II) catalysts. An ethylene insertion barrier is derived by bulk ethylene polymerizations at various pressures at 60 °C. Preliminary results of copolymerization of ethylene with polar and nonpolar olefins indicate a reduced catalytic activity compared to ethylene homopolymerization. Chapter 4 details a study to enhance the catalytic activity of anilinotropone (N,O)Ni(II) catalysts by adding strong electron-withdrawing nitro groups to the ligand backbone. These modified catalysts display dramatically enhanced activity for ethylene polymerization. The results are compared with the unnitrated parent catalysts. Copolymerization of ethylene and polar or nonpolar olefins and oligomerization of 9-olefins using these catalysts are also performed and presented.
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  • In Copyright
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  • Brookhart, Maurice
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  • Open access
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  • October 19, 2010

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