New complexes of palladium(II) with chelating heterocyclic nitrogen ligands. Characterization and catalytic activity in CO-styrene copolimerization. Crystal structure of [Pd(bipy)2][BAr’4]2, Ar’ = [3,5-(CF3)2C6H3]

New bis-chelated palladium(II) derivatives [Pd(bipy(R))(2) ](2+) and [Pd(bipy)(bipy(R))](2+) (bipy = 2,2'-bypiridine, bipy(R) = 6-Me, 6-Et, 6-i -Pr-2,2'-bipyridine) have been isolated as [BAr'(4)](-) salts (Ar' = [3,5-(CF3)(2)C6H3]) 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)][BAr4'](2) at low pressure (p(co) = 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). (C) 2002 Elsevier Science B.V. All rights reserved.

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.