Bis(pyrazole)- and bis(pyrazolyl)-palladium complexes as phenylacetylene polymerization catalysts |
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Authors: | Kelin Li M. Sarah Mohlala Tebogo V. Segapelo Poslet M. Shumbula Ilia A. Guzei James Darkwa |
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Affiliation: | 1. Department of Chemistry, University of The Western Cape, Private Bag X17, Bellville 7535, South Africa;2. Department of Chemistry, University of Johannesburg, Auckland Park Kingsway Campus, P.O. Box 524, Johannesburg 2006, South Africa;3. Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA |
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Abstract: | Two types of pyrazole-based palladium complexes were used to catalyze the polymerization of phenylacetylene. Catalysts with electron-withdrawing linkers, [{1,3-(3,5-R2pzCO)2C6H4}Pd2Cl2(μ-Cl)2] (R = tBu (1), Ph (2), Me (3), [{2,6-(3,5-R2pzCO)2C5H3N)}PdCl2] (R = tBu (4), Me (5)), show high conversion; whilst those with simple pyrazole ligands, [(3,5-R2pz)2PdCl2] (R = H (6), Me (7), tBu (8)), [(3,5-tBu2pz)2PdCl(Me)] (9), have much lower conversions. Conversion greatly improved when 9 was used to catalyze the co-polymerization of sulfur dioxide and phenylacetylene. Both types of catalysts produce predominantly trans–cisoidal polyphenylacetylene. |
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Keywords: | Pyrazole Pyrazolyl Palladium complexes Catalysts Phenylacetylene Polymerization |
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