Pd(II) complexes with 3,3′-substituted bipyridine ligands: Synthesis, crystal structure, DFT calculations and catalytic studies in compressed carbon dioxide

Cationic bis(chelated) complexes [Pd(N-N)2][BArF]2 with N-N = 3,3′-diester-2,2′-bipyridine ligands were prepared and tested as catalyst for the CO/tert-butylstyrene copolymerization using compressed carbon dioxide as a solvent. The NMR analysis of these complexes suggests the formation of several species in solution. A detailed DFT calculation analysis indicated that these species correspond to different relative orientations of the carbonyl group. These complexes showed poor catalytic activity towards the formation of polyketones, producing only poly(tert-butylstyrene) when trifluoroethanol was used as a solvent. The use of compressed carbon dioxide favored the formation of the polyketones when the complexes with methyl and isopropyl ester derivatives were employed as catalysts.