Branched polyethylenes attainable using thermally enhanced bis(imino)acenaphthene-nickel catalysts: Exploring the effects of temperature and pressure

Abstract

The 4,4'-difluorobenzhydryl-containing nickel(II) bromide and chloride chelates, [1-[2,6-{(4-F-C6H4)2CH}2-4-{C(CH3)3}-C6H2N]-2-(ArN)C2C10H6]NiX2 (X = Br:

Enhancing performance of α‐diiminonickel precatalyst for ethylene polymerization by substitution with the 2,4‐bis(4,4'‐dimethoxybenzhydryl)‐6‐methylphenyl group

“…In comparison to the bromide‐containing species, the catalytic systems based on dichloronickel(II) complexes ( Ni6 – Ni10 ) exhibited relatively lower activities (with negligible variation between the particular precatalysts), ranging from 3.65 to 3.99 × 10 6 g of PE (mol of Ni) −1 h −1 . In addition, the resultant high‐molecular‐weight polyethylene shows evidence of a moderate molecular weight distribution ( M w / M n = 2.15–4.20), in certain cases approaching the behavior of a single‐site catalyst 21–24 …”

“…The following order of activity was devised for the bromide precatalysts: Ni1 [2,6‐di(Me)] > Ni4 [2,4,6‐tri(Me)] > Ni2 [2,6‐di(Et)] > Ni5 [2,6‐di(Et)‐4‐Me] > Ni3 [2,6‐di( i ‐Pr)]. It was also observed that the presence of the methyl group at the para‐ position has a negative effect on the catalytic activity, but the difference is that with Me 2 AlCl as a cocatalyst, Ni3 has the lowest activity, which may be due to the steric hindrance 21 . For the chloride precatalysts Ni6 – Ni10 , these displayed relatively lower activities when compared with the bromides, but showed a similar order of activity with respect to the substituents: Ni6 [2,6‐di(Me)] > Ni9 [2,4,6‐tri(Me)] > Ni7 [2,6‐di(Et)] > Ni10 [2,6‐di(Et)‐4‐Me] > Ni8 [2,6‐di(i‐Pr)].…”

Paradox of Late Transition-Metal Catalysts in Ethylene Polymerization

“…Very recently, our group have investigated the difference between homogeneous and immobilized 1-(2,6-dibenzhydryl-4nitrophenylimino)-2-mesityliminoacenaphthylnickel bromide as a precatalyst in ethylene polymerization and found that the activity was also improved. [47] We have also developed nickel precatalyst 5 [48,49] and 6 [50,51] incorporating difluorobenzhydryl groups at the 2-position, 2,6-position or 2,4-position of either one or both N-aryl groups. All these systems showed good thermal stability by maintaining high activity.…”

Facile synthesis of sterically demanding SHOP‐type nickel catalysts for ethylene polymerization

“…Nickel and palladium based complexes supported by different types of ligands have been extensively utilized as olefin oligo/polymerization catalysts for decades both in academia and industry because of their low oxophilicity and copolymerizing capability of the olefin with polar comonomers . The chain‐walking process has received extensive researches in ethylene oligo−/polymerization using these catalysts to produce polyethylene (PE) possessing unique branched structures . These catalysts were usually ligated by α‐ diimine, iminopyridyl, iminopyrrolyl, salicylaldimine, and many others .…”