Highly Active New α-Diimine Nickel Catalyst for Polymerization of Ethylene

A new alpha-diimine ligand la, 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 (1)H NMR, (13)C NMR, Fourier transform infrared spectroscope(FTIR), elemental analysis and X-ray photoelectron spectroscopy(XPS). alpha-Diimine ligand 1b, bis[N,N'-(2,6-dimethylphenypimino]-2,3-butanediyhdene and its corresponding Ni(II) complex 2b, {bis[N,N'-(2,6-dimethylphenyl)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 x10(7) g PE/(mol Ni.h.01 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.