Pyrazolyl-pyrimidine based ligands in palladium catalyzed copolymerization and terpolymerization of CO/olefins

Cationic palladium(II) complexes of the type View the MathML source[PdMe(NCMe)(N–N′)][BAr4′] containing bisnitrogen ligands with a pyrazole moiety were synthesized from the corresponding neutral derivatives [PdClMe(N–N′)]. Their characterization by 1H and 13C NMR spectroscopy in solution evidences the presence of the Pd–Me group cis to the pyrazole ring. The catalytic behaviour of the cationic complexes in CO/4-tert-butylstyrene copolymerization and CO/ethylene/4-tert-butylstyrene terpolymerization was investigated. Productivity was greatly enhanced when the reaction was carried out in 2,2,2-trifluoroethanol (TFE). Molecular weights and polydispersity (Mw/Mn) of the obtained polyketones resulted among the best reported for Cs-bisnitrogen planar ligands.