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

Cationic palladium(II) complexes of the type [PdMed(NCMe)(N-N')][BAr'(4)] containing bisnitrogen ligands with a pyrazole moiety were synthesized from the corresponding neutral derivatives [PdClMe(N-N')]. Their characterization by H-1 and C-13 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 (M-w/M-n) of the obtained polyketones resulted among the best reported for C-s-bisnitrogen planar ligands. (C) 2008 Published by Elsevier B.V.