Homo‐ and Copolymerization of Norbornene with Allyl Palladium and Nickel Complexes Bearing Imidazo[1,5‐a]pyridine Sulfonate Ligands

Abstract

AbstractA series of allyl palladium and nickel complexes based on imidazo[1,5‐a]pyridine sulfonate ligands were synthesized. All these complexes were fully characterized by 1H and 13C NMR, elemental analysis, and high‐resolution mass spectrometry (HRMS). By treatment with Me2AlCl, palladium complexes showed high activities (up to 4.5×107 g of PNB (mol of Pd)−1 h−1) in norbornene polymerization, and the steric hindrance of the catalysts had little effect on the catalytic activities. They could also catalyze the copolymerization of norbornene with butyl vinyl ether (BVE) and ester monomers, but could not catalyze the copolymerization of norbornene with allyl butyl ether (ABE). In addition, the catalytic activities of nickel complexes for norbornene polymerization were similar to that of palladium complexes upon activation with MAO. They could catalyze copolymerization of norbornene with BVE and ABE, but not with ester monomers. In nickel system, the lower steric hindrance of the substituent led to higher activity.