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Preparation and in situ chain-end-functionalization of branched ethylene oligomers by monosubstituted α-diimine nickel catalysts

Abstract

By utilizing an efficient strategy on the combination of the most bulky and the least bulky substituents into the ortho-N-aryl groups of alfa-diimine ligands, a new class of unsymmetrically monosubstituted (H/CHAr2) alfa-diimine nickel complexes Ni-1~5 and palladium complexes Pd-1~5 with trans- and cis- forms was synthesized and comprehensively identified by NMR spectroscopy, single crystal X-ray diffraction, mass spectroscopy, and elemental analysis. In the presence of excess MAO, all these nickel complexes Ni-1~5 were thermally stable (-10~70 °C) and exhibited extremely high activities of 1000~10000 kg mol-1 h-1 for ethylene polymerization. By readily varying the reaction temperature, highly linear polyethylenes (< 2/1000C, Tm = 132~140 °C) with moderate molecular weights (Mn: 10 kg mol-1) and (highly) branched ethylene oligomers (up to 73/1000C) with Mn of 1000 g mol-1 could be produced with broad bimodal molecular weight distributions respectively. More remarkably, chain-end-functionalzition of these generated oligoethylenes could be achieved in situ by the Friedel-Crafts addition to the aromatic compounds as the reaction solvent (such as toluene and anisole) and could be also tuned from 0% to 100% conversion by temperature, solvent, and catalyst. As a comparison, under the activation of NaBArF, all these palladium complexes Pd-1~5 displayed a good acitivity (10 kg mol-1 h-1) for ethylene polymerization to yield low molecular weight branched ethylene oligomers (52~70/1000C) and also were active for the copolymerization of ethylene and methyl acrylate (MA) to generate ethylene/MA co-oligomers with ester functional group at the end of branches (0.87~3.65 mol%).

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Publication details

The article was received on 21 Mar 2019, accepted on 12 Apr 2019 and first published on 15 Apr 2019


Article type: Paper
DOI: 10.1039/C9PY00433E
Citation: Polym. Chem., 2019, Accepted Manuscript

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    Preparation and in situ chain-end-functionalization of branched ethylene oligomers by monosubstituted α-diimine nickel catalysts

    X. Ma, X. Hu, Y. Zhang, H. Mu, L. Cui and Z. Jian, Polym. Chem., 2019, Accepted Manuscript , DOI: 10.1039/C9PY00433E

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