Polymerization of α-Olefins Using a Camphyl α-Diimine Nickel Catalyst at Elevated Temperature

Chiral (1S)- and (1R)-camphyl alpha-diimine nickel complexes were synthesized respectively with (1S)-(+) camphorquinone and (1R)-(-) camphorquinone as raw reagents and used as catalyst precursors for olefin polymerizations. It is found that the ligand chirality has no influence on catalytic activity and regioselectivity for olefin polymerizations. Ethylene, propylene, 1-hexene, and 4-methyl-1-pentene polymerizations with the camphyl alpha-diimine nickel activated by AlEt2CI can exhibit some living characteristics under the optimized conditions. The resultant polypropylenes and poly(1-hexene)s have significantly narrow molecular weight distributions (PDI < 1.2) in a wide temperature range, even at an elevated temperature of 70 degrees C. Sustainable period of the linear relationship of M-n vs polymerization time depends on temperature for propylene and 1-hexene polymerizations. Additionally, high 1,3-enchainment fraction of 45% is observed even at -60 degrees C for propylene polymerization using the camphyl alpha-diimine catalyst due to 2,1-insertion of propylene and chain walking.