Molecular weight control of polyethylene waxes using a constrained imino-cyclopenta[ b]pyridyl-nickel catalyst.

ABSTRACT Five examples of nickel(II) bromide complexes bearing N,N-imino-cyclopenta[ b]pyridines, [7-(ArN)-6,6-Me2C8H5N]NiBr2 (Ar = 2,6-Me2C6H3 ( Ni1), 2,6-Et2C6H3 ( Ni2), 2,6- i-Pr2C6H3 ( Ni3), 2,4,6-Me3C6H2 ( Ni4), 2,6-Et2-4-MeC6H2 ( Ni5)), have been prepared by the reaction of the corresponding ligand, L1- L5, with NiBr2(DME) (DME = 1,2-dimethoxyethane). On crystallization from bench dichloromethane, Ni1 underwent adventitious reaction with water to give the aqua salt, [ L1NiBr(OH2)3][Br] ( Ni1'). The molecular structures of Ni1' and Ni3 have been structurally characterized, the latter revealing a bromide-bridged dimer. On activation with either MMAO or Et2AlCl, Ni1, Ni2, Ni4, and Ni5, all exhibited high activities for ethylene polymerization (up to 3.88 × 106 g(PE) mol−1(Ni) h−1); the most sterically bulky Ni3 gave only low activity. Polyethylene waxes are a feature of the materials obtained which typically display low molecular weights ( Mws), narrow Mw distributions and unsaturated vinyl and vinylene functionalities. Notably, the catalyst comprising Ni1/Et2AlCl produced polyethylene with the lowest Mw, 0.67 kg mol−1, which is less than any previously reported data for any class of cycloalkyl-fused pyridine-nickel catalyst. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3494-3505 [ABSTRACT FROM AUTHOR]