Stoccoro, Sergio and Alesso, Giuseppe Andrea and Cinellu, Maria Agostina and Minghetti, Giovanni and Zucca, Antonio and Bastero Rezola, Amaya and Claver, Carmen and Manassero, Mario (2002) New complexes of palladium(II) with chelating heterocyclic nitrogen ligands: characterization and catalytic activity in CO-styrene copolymerization: crystal structure of [Pd(bipy)2][BAr'4]2; Ar'[3,5-(CF3)2C6H3]. Journal of Organometallic Chemistry, Vol. 664 (1-2), p. 77-84. ISSN 0022-328X. Article.
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New bis-chelated palladium(II) derivatives [Pd(bipyR)2]2+ and [Pd(bipy)(bipyR)]2+ (bipy=2,2'-bypiridine, bipyR= 6-Me, 6-Et, 6-i -Pr-2,2'-bipyridine) have been isolated as [BAr'4]- salts (Ar'=[3,5-(CF3)2C6H3]) and tested as catalyst precursors in the CO- styrene or 4-tert -butylstyrene (TBS) copolymerization. The comparison of their activity with that of [Pd(bipy)2][BAr'4]2 prepared for comparative purpose shows that the presence of a 6-substituent on the bipy has a negative effect. On the other hand, comparison of the activities of [Pd(bipy)2][BAr'4]2 and [Pd(bipy)2][PF6]2, reported to be one of the best catalytic precursors for this reaction, shows that the [BAr'4] anion increases the activity under various reaction conditions. The results obtained with [Pd(bipy)2][BAr'4 ]2 at low pressure (pCO/10 atm) are among the best reported for this type of precatalysts. A study related to the use of 2,2,2-trifluoroethanol (TFE), as solvent, allows the optimisation of the amount of alcohol required for the copolymerization reaction. The X-ray structure of [Pd(bipy)2][BAr'4]2 shows that the conformation of the cation is similar to that observed in the corresponding [BF4] salt, but remarkably different from that of [Pd(bipy)2][PF6]2.
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