Palladium (II)-bisphosphine catalyzed copolymerization of CO and ethylene was studied in detail. The results showed that DPPPr/Pd (II) mole ratio, CF3COOH/Pd (II) mole ratio and solvent greatly influence the catalytic activity. Solvent effects were studied and in detail through end group analysis. With high pressure in situ 1H-NMR technique, the signals of coordinated ethylene at 4.4 ppm and methylene linked with Pd (II)(Pd—CH2-) at 0.6 ppm ...