Targeting polyethylene waxes: 9-(2-cycloalkylphenylimino)-5,6,7,8-tetrahydrocycloheptapyridylnickel halides and their use as catalysts for ethylene polymerization

A series of 9-(2-cycloalkylphenylimino)-5,6,7,8-tetrahydrocycloheptapyridine derivatives (L1–L3) was synthesized, and reacted with nickel halides to form their corresponding nickel complexes (bromide: Ni1–Ni3; chloride: Ni4–Ni6). All organic compounds and nickel complexes were well characterized. The structure of a representative complex Ni1 was determined by a single crystal X-ray study, revealing a distorted trigonal bipyramidal geometry at the nickel centre. Upon activation with either modified methylaluminoxane (MMAO) or diethylaluminium chloride (Et2AlCl), all nickel complexes showed high activities toward ethylene polymerization. The obtained polymers were confirmed to be polyethylene waxes with low molecular weights (in the range of 1.83 to 6.78 kg mol−1) and narrow polydispersity (PDI: 1.38–1.78); moreover, the obtained polyethylenes were highly branched ones. These polyethylene waxes have potential application as functional adducts of lubricants or pour-point depressants.

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