A concerted double-layer steric strategy enables an ultra-highly active nickel catalyst to access ultrahigh molecular weight polyethylenes

Ji, Xia; Zhang, Yixin; Kou, Shuqing; Jian, Zhongbao

doi:10.1016/j.jcat.2020.07.017

Cited by 60 publications

(40 citation statements)

References 47 publications

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“…In general, with the increase of polymerization temperature (30 °C to 120 °C), catalytic activities gradually dropped, which was also observed for other reported α‐diimine nickel system. [ 63‐67 ] Except Ni1 without steric bulk, Ni2 — Ni5 and Ni5' showed very high activities, which were on a high level of 10 7 g·mol –1 ·h –1 at all polymerization temperatures from 30 °C to a harsh temperature of 120 °C (Table 1, entries 4—24). The results indicated that these α‐diimine nickel catalysts bearing a rigid and bulky structure played an important role on the thermal stability and catalytic activity.…”

Section: Resultsmentioning

confidence: 99%

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Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization^†

Zhang

et al. 2021

Chin. J. Chem.

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Main observation and conclusion Steric bulk plays a significantly paramount role in late transition metal promoted olefin (co)polymerization in terms of polymer molecular weight and catalyst thermal stability. Numerous sterically encumbered nickel and palladium catalysts have been developed, but they are usually uni‐directional. In this contribution, from a bi‐directional side the distinctive horizontally and vertically concerted steric strategy was well‐developed and applied to α‐diimine nickel catalysts. In ethylene polymerization, the increase of vertically steric bulk (H, Ph, Biph) led to an enhanced polymer molecular weight, a slightly ascended branching density; likewise increasing horizontally steric bulk (Ph, Nap, Ant) further resulted in the increase of polymer molecular weight and branching density. As a result, in sharp contrast to Ni1(H) without steric bulk, Ni5(Ant) with horizontally and vertically concerted steric bulk was thermally stable, showed very high activities at a level of 107 g·mol–1·h–1, and produced polyethylenes with the highest molecular weight of 518.8 × 104 g·mol–1 and the broader range of branching density from 2.4/1000C to 27.8/1000C. In the copolymerization of ethylene with methyl 10‐undecenoate, Ni5(Ant) also provided the highest copolymer molecular weight but gave the lowest incorporation of co‐monomer. This work sheds light on the steric effect on olefin (co)polymerization.

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Section: Resultsmentioning

confidence: 99%

“…[ 62‐65 ] Recently, we illuminated a double‐layer steric strategy that endows α‐diimine nickel catalysts with intriguing properties (Chart 1, VII and VIII ). [ 66‐67 ]…”

Section: Background and Originality Contentmentioning

confidence: 99%

Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization^†

Zhang

et al. 2021

Chin. J. Chem.

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“…We were all along interested in the improvement on copolymerization of olefin and polar monomers [6,[78][79][80][81][82] and were engaged in terphenyl-substituted -diimine nickel catalysts (Chart 2) that was first reported in 2001. [64,65] To greatly enhance M n of polyethylene and reach UHMWPE, we envisioned a strategy of installing the secondary sterically encumbered substituents into terphenyl-substituted -diimine nickel catalysts and thus synthesized a new family of nickel catalysts Ni1~Ni4 (Scheme 1).…”

Section: Chart 2 Representative Nickel Catalysts For Producing High Molecular Weight Pe At High Pressurementioning

confidence: 99%

Facile Access to Polar-Functionalized Ultrahigh Molecular Weight Polyethylene at Ambient Conditions

Kang

Zhang

et al. 2022

CCS Chem

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Direct copolymerization of ethylene with polar monomers to produce polar functionalized polyethylene is the most straightforward and potentially ideal route. However, access to high molecular weights of polar copolymers represents one of the biggest challenges. In this contribution, we report a family of well-designed nickel catalysts that readily address the issue at convenient and highly desired ambient conditions. Under 1 bar at 30 o C, polar functionalized ultrahigh number-average molecular weight polyethylenes (UHMWPE, M n = 825~1102 kg mol -1 ) can directly be generated. The highest average number of incorporated polar units per polymer chain is 122. This enhances copolymer molecular weights with up to two orders of magnitude relative to previous reports. Notably, this nickel catalyst family also exceptionally produces the highest number-average molecular weight polyethylenes (M n = 6037 kg mol -1 ) at 1 bar using the nickel species. The Sterimol B 1 steric parameter of nickel catalyst quantitatively correlates to polymer molecular weight. Mechanistic insights from DFT calculation reveal that the low barrier (10.4 kcal mol -1 ) of ethylene insertion as the rate-limiting step should be responsible for high activity and the formation of UHMWPE. This coordination-insertion approach is strikingly contrast to the high energy free-radical approach.

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“…Brookhart and co-workers introduced Ni(II) complexes with N,N-bidentate α-diimine ligands [2], capable of producing branched PE from ethylene as the only feedstock. Since this pioneering discovery, the area has advanced greatly, with the modifications of α-diimine ligands (by tuning both the backbone and substituents) and adjusting proper polymerization conditions providing access to polymers with desired molecular (molecular weight and molecular weight distribution, degree of branching) and mechanical characteristics [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

α-Diimine Ni-Catalyzed Ethylene Polymerizations: On the Role of Nickel(I) Intermediates

2021

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Nickel(II) complexes with bidentate N,N-α-diimine ligands constitute a broad class of promising catalysts for the synthesis of branched polyethylenes via ethylene homopolymerization. Despite extensive studies devoted to the rational design of new Ni(II) α-diimines with desired catalytic properties, the polymerization mechanism has not been fully rationalized. In contrast to the well-characterized cationic Ni(II) active sites of ethylene polymerization and their precursors, the structure and role of Ni(I) species in the polymerization process continues to be a “black box”. This perspective discusses recent advances in the understanding of the nature and role of monovalent nickel complexes formed in Ni(II) α-diimine-based ethylene polymerization catalyst systems.

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A concerted double-layer steric strategy enables an ultra-highly active nickel catalyst to access ultrahigh molecular weight polyethylenes

Cited by 60 publications

References 47 publications

Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization^†

Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization^†

Facile Access to Polar-Functionalized Ultrahigh Molecular Weight Polyethylene at Ambient Conditions

α-Diimine Ni-Catalyzed Ethylene Polymerizations: On the Role of Nickel(I) Intermediates

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A concerted double-layer steric strategy enables an ultra-highly active nickel catalyst to access ultrahigh molecular weight polyethylenes

Cited by 60 publications

References 47 publications

Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization†

Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization†

Facile Access to Polar-Functionalized Ultrahigh Molecular Weight Polyethylene at Ambient Conditions

α-Diimine Ni-Catalyzed Ethylene Polymerizations: On the Role of Nickel(I) Intermediates

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Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization^†

Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization^†