Trifluoroethanol: key solvent for palladium-catalyzed polymerization reactions |
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Authors: | Alessandro Scarel Davide Franchi Giovanni Mestroni Serafino Gladiali Barbara Binotti Tania Gragnoli |
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Institution: | a Dipartimento di Scienze Chimiche, Università di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy b Dipartimento di Chimica, Università di Sassari, Via Vienna 2, 07100, Sassari, Italy c Istituto di Scienze Chimiche, Università di Urbino, Piazza, Rinascimento 6, Urbino, Italy d PolyLab-INFM-Pisa c/o, Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy e Dipartimento di Chimica e Chimica Industriale, Università di Pisa c/o Waste Recycling, Via Risorgimento 35, 56126 Pisa, Italy |
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Abstract: | A series of cationic palladium complexes of general formula Pd(CH3)(NCCH3)(N-N)]X] (N-N = phen 1, 3-sec-butyl-1,10-phenanthroline (3-sBu-phen) 2, bpy 3, (−)-(S,S)-3,3′-(1,2-dimethylethylenedioxy)-2,2′-bipyridine (bbpy) 4, (+)-(R)-3,3′-(1-methylethylenedioxy)-2,2′-bipyridine (pbpy) 5, N,N′-bis(2,6-diisopropylphenyl)-2,3-butanediimine (iso-DAB) 6; , OTf (OTf = triflate) b) containing different nitrogen-donor ligands were prepared from the corresponding neutral chloro derivatives Pd(CH3)(Cl)(N-N)] (1c-6c). They were characterized by 1H NMR spectroscopy and elemental analysis. Single crystals suitable for X-ray determination were obtained for complexes Pd(CH3)(NCCH3)(bbpy)]PF6] (4a), Pd(CH3)(NCCH3)(iso-DAB)]PF6] (6a) and Pd(Cl)2(bbpy)] (4c′). The latter is the result of an exchange reaction of the methyl group, present in complex 4c, with a chloride, that occurred after dissolution of 4c in CDCl3, for 1 week at 0 °C. The catalytic behavior of complexes 1a-5a and 1b-5b in the CO/styrene copolymerization was studied in CH2Cl2 and 2,2,2-trifluoroethanol (TFE) evidencing the positive effect of the fluorinated alcohol both in terms of productivity and molecular weight values of the polymers obtained. Influence of the nitrogen ligand, the anion and the reaction time in both solvents were investigated and is discussed in detail. Encouraging preliminary results were also obtained in the synthesis of polyethylene, in TFE, catalyzed by Pd(CH3)(NCCH3)(iso-DAB)]PF6] (6a). |
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Keywords: | Palladium Nitrogen-donor ligands Carbon monoxide Olefins Polyketone Catalysis |
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