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-Me2C 6H3, 3a; Ar = 2,4,6-Me3C6H 2 3b; Ar = 2,6-Me2-4-tBuC6H2, 3c; Ar = 2,6-Me2-4-BrC6H2, 3d; Ar = 2,6-Me 2-4-ClC6H2, 3e; Ar = 2,6-iPr2C 6H3, 3f; Ar = 2,4,6-iPr3C6H 2, 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.