A new α-diimine ligand 1a, bis[N,N′-(4-tert-butyl-2,6-dimethylphenyl)imino]-2,3-butanediylidene and its corresponding Ni(II) complex 2a, {bis[N,N′-(4-tert-butyl-2,6-dimethylphenyl)imino]-2,3-butanediylidene}dibromo- nickel were successfully synthesized, and characterized by 1H NMR, 13C NMR, Fourier transform infrared spectroscope(FTIR), elemental analysis and X-ray photoelectron spectroscopy(XPS). α-Diimine ligand 1b, bis[N,N′-(2,6- dimethylphenyl)imino]-2,3-butanediylidene and its corresponding Ni(II) complex 2b, {bis[N,N′-(2,6-dimethyl- phenyl)imino]-2,3-butanediylidene}dibromonickel were also synthesized and characterized for comparison. The pre-catalyst 2a with sterically bulky, electron-donating group tert-butyl, activated by diethylaluminum chloride (DEAC) and tested in the polymerization of ethylene, was very highly active[2.01×107 g PE/(mol Ni?h?0.1 MPa)] and led to a very highly branched polyethylene(ca. 35―103 branches/1000 C). The state of the polyethylene obtained varied from plastic, elastomer polymers to the oil-like hyperbranched polymers.
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