Cationic para-benzhydryl substituted alpha-diimine nickel catalyzed ethylene and 1-decene polymerizations via controllable chain-walking

摘要

A series of alpha-diimine nickel complexes bearing para-benzhydryl groups, {[(2,6-R-2-4-CHPh2C6H2N = C)(2)Nap] NiBr2, Nap: 1,8-naphthdiyl, R = Me (C1); R = Et (C2); R = Pr-i (C3)}, were synthesized and characterized. Upon activation with AlEt2Cl, these para-benzhydryl substituted catalysts conducted the ethylene and 1-decene polymerizations via controlled chain-walking process. These nickel complexes exhibited good thermal stability and high activities (up to 10(6) g PE (mol Ni h)(-1)) towards ethylene polymerization, producing high molecular weight polyethylenes with a relatively low degree of branching and narrow polydispersities (M-w/M-n = 2.01). The catalytic activities [(0.81-2.42) x 10(6) g PE (mol Ni.h)(-)(1)], polyethylene molecular weights [M-n: (7.9-29.3) x 10(4) g mol(-1)] and total branching densities (57-102/1000C) can be tuned over a wide range. These controlled branching degrees of the obtained polyethylenes were decreased with increasing the bulkiness of the ligand and decreasing the polymerization temperature. Polymerization of 1-decene using these cationic nickel complexes generated branched poly(1-decene)s (69-87/1000C) with high molecular weights and narrow polydispersities (M-w/M-n = 1.18-1.55).