Nickel cyclopentadienyl complexes as catalysts for ethylene polymerization

Nickel cyclopentadienyl phenyl phosphine complexes CpNi(Ph) (PPh3) (Cp = cyclopentadienyl, and iminoaryl-substituted cyclopentadienyl) are used as catalysts for ethylene polymerization in the presence of methylaluminoxane (MAO). The catalytic performances were studied under a variety of reaction conditions in which Al/Ni molar ratio, ethylene pressure, temperature, time and catalyst loading were varied. The catalytic activities and the molecular weights increase with increasing Al/Ni molar ratio and ethylene pressure. The catalysts are the thermal stable. Even at 76 °C, the activity reaches to 109.0 kg PE (mol Ni)−1h−1 with the molecular weights of Mn = 20.6 × 104. The effect of the bulkiness of cyclopentadienyl ligands on ethylene polymerization was also investigated. The catalytic activities and the molecular weights of polyethylene decrease as the iminoaryl substituents are introduced into the cyclopentadienyl ring. The polymers obtained from these catalysts are linear polyethylene with 6–8 branches per thousand carbons.

Graphical abstractNickel cyclopentadienyl complexes CpNi(Ph) (PPh3) (Cp = cyclopentadienyl, and iminoaryl-substituted cyclopentadienyl) are used as catalysts for ethylene polymerization in the presence of methylaluminoxane. Linear high molecular polyethylenes with 6–8 branches per thousand carbons are produced.Figure optionsDownload full-size imageDownload as PowerPoint slide