Ethylene polymerization by (α‐diimine)nickel(II) complexes bearing different substituents on para‐position of imines activated with MMAO

Abstract A series of (α‐diimine)nickel(II) complexes [ArN = C(Nap)C = NAr]NiBr2 (Nap = 1,8‐naphthdiyl, Ar = 2,6‐Me2C6H3, 3a; Ar = 2,4,6‐Me3C6H23b; Ar = 2,6‐Me2‐4‐tBuC6H2, 3c; Ar = 2,6‐Me2‐4‐BrC6H2, 3d; Ar = 2,6‐Me2‐4‐ClC6H2, 3e; Ar = 2,6‐iPr2C6H3, 3f; Ar = 2,4,6‐iPr3C6H2, 3g; Ar = 2,6‐iPr‐4‐BrC6H2, 3h) have been synthesized, characterized, and investigated as precatalysts for ethylene polymerization in the presence of modified methylaluminoxane (MMAO). The substituents of α‐diimine ligands and their positions located significantly influence catalyst activity and polymer property. It is found that the catalytic activities of the nickel complex/MMAO systems and the microstructure of the polymer obtained are dominated by not only hindering effect of ortho‐position substituents but also electronical effect of para‐position substituents. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008