Alternative copolymerization of CO and ethylene catalyzed by palladium(II)

With high pressure in situ H-1-NMR technique, the alternative copolymerization of CO with ethylene catalyzed by Pd(II)-DPPPr-CF3COOH catalyst were studied under 2.0MPa CO/ethylene (1:1, molar ratio) using CD3OD and CD3COCD3 as solvents. The H-1-NMR signals of coordinated ethylene anti methylene linked to Pd(II) were observed, which showed that ethylene was activated by coordination with Pd(II) during the copolymerization before it's insertion into Pd-C bond to achieve the chain propagation. But the signal of Pd-H bond was not observed in all the in situ H-1-MMR experiments, which indicated that the copolymerization initiation was not caused by Pd-H bond, or Pd-H initiation was very few in alcoholic solvent.