Synthesis of (N−O)-Ligated Palladium(II) Complexes and Their Use in Ethene Homopolymerization and Norbornene Copolymerizations

Cyclic olefin copolymers are an important class of polymeric materials. Here, we report the synthesis and characterization of several (N−O)-ligated palladium(II) complexes and their use in ethene homopolymerization, as well as ethene/norbornene and carbon monoxide/norbornene copolymerizations. Most notably, these catalysts show relatively high activity toward ethene/functional norbornene copolymerizations, and a high level of incorporation of the norbornene derivative was observed. The molecular weight of the copolymers can be controlled by adjusting the ethene/norbornene feed ratio. The ethene/nonpolar functional norbornene copolymerizations have the characteristics of a “living” polymerization at low ethene/norbornene feed ratios. Finally, the successive stepwise insertions of carbon monoxide and norbornene into a preformed palladium−carbon bond were observed by NMR spectroscopy.