Salicylaldiminato nickel(II) catalysts with 5‐halo‐3‐methoxy groups for ethylene polymerization |
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Authors: | Nikhil A. Kolhatkar Amber M. Monfette Shuo Lin Massoud J. Miri |
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Affiliation: | 1. Center for Materials Science and Engineering, Rochester Institute of Technology, Rochester, New York 14623;2. Department of Chemistry, Rochester Institute of Technology, Rochester, New York 14623 |
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Abstract: | Two neutral salicylaldiminato methyl pyridine nickel(II) complexes were synthesized and evaluated for ethylene polymerization. Each catalyst bears a methoxy group in the 3‐position and a halogen atom in the 5‐position of the salicyl ligand, chlorine in case of catalyst 3a and bromine in 3b . Molecular structures of the catalysts were obtained by X‐ray crystallography. The resulting polymerization activities, for example, indicated by a maximum turnover frequency of 4,870 mol ethylene/(mol Ni × h) for 1‐h runs obtained with 3a , were higher than those of similar catalysts at comparable conditions reported in the literature. Catalyst 3a was slightly more active than catalyst 3b . The polymers are branched as measured by 1H NMR and 13C NMR. This was also reflected in the melting temperatures between 76 and 113 °C obtained by differential scanning calorimetry. By using gel permeation chromatography measurements, it was determined that the Mw of the polymers ranges between about 5,400 and 21,600 g/mol. In particular, the effect of the polymerization temperature on the catalyst activity, degree of branching, and molecular weight properties has been described. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 |
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Keywords: | branched catalysis nickel polyethylene (PE) single‐site catalysts |
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