Recent progress in preparation of branched polyethylene with nickel, titanium, vanadium and chromium catalytic systems and EPR study of related catalytic systems

Xing, Yusheng; Wang, Li; Yu, Haojie; Khan, Amin; Haq, Fazal; Zhu, Longgen

doi:10.1016/j.eurpolymj.2019.109339

Cited by 15 publications

(6 citation statements)

References 121 publications

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“…Redox-active ligands 1,2 in combination with redox-active transition metals are still top in coordination chemistry and widely used in many areas of chemistry [3][4][5][6][7] due to their unique electronic structure. 8,9 In this series, bis(imino)acenaphthenes (BIANs) lead the list.…”

Section: Introductionmentioning

confidence: 99%

Cobalt(ii) coordination to an N₄-acenaphthene-based ligand and its sodium complex

et al. 2023

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Section: Introductionmentioning

confidence: 99%

Cobalt(ii) coordination to an N₄-acenaphthene-based ligand and its sodium complex

et al. 2023

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“…Such effects arise due to the competition between the propagation, migration, and termination processes [6]. In this sense, α-diimine-based complexes, as well-known structures proposed by Brookhart, are endowed with an excellent performance for preparation of branched PE products [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…Researchers such as Brookhart [7][8][9] and Drent [7,10] have further found that branching density can be manipulated with the ligand structure of some catalysts under polymerization conditions.…”

Section: Introductionmentioning

confidence: 99%

Ethylene/α-olefin homo- and copolymerization using a dinuclear catalyst of nickel

Nokandi,

Zohuri,

Ramezanian

et al. 2023

Preprint

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Considering the essence of high electron density of ligands, frameworks with high electron donating groups are important in the transition-metal catalytic systems. As benzhydrol groups have been investigated for their beneficial electronic effects, a novel homo-dinuclear Ni (II) catalyst based on benzhydrol-substituted ligand was synthesized, characterized, and used for ethylene polymerization. The catalyst was further examined and compared with its mononuclear analogue. The maximum activity for the polymerization was then obtained at molar ratio of Al/Ni: 1500/1, polymerization temperature of 15 ℃ and the monomer pressure of 1.5 bar within 5 min of the polymerization which was 2.64×106 g mol-1Ni h-1. Effects of cocatalyst type (e. g., modified methylalumoxane (MMAO), triisobutylaluminum (TiBA), and triethylaluminum (TEA)) in the polymerization were also investigated wherein MMAO outperformed in terms of the greatest activity. As the polymerization temperature elevated, the polyethylene (PE) microstructure changed from crystalline into amorphous form, while both of the activity of the catalyst and the Viscosity Average Molecular Weight (M̅v) of the obtained polymer were diminished. With regard to increasing of ethylene pressure in the reactor (up to 4 bars), the M̅v increased and reached to the maximum value of 1.44 ×106 g mol-1. The catalyst was also active in the presence of the long-chain α-olefin monomers, such as 1-hexene and 1-octene, the comonomers. The co-monomer addition decreased crystallinity of the polymer (from 25 to 15%) and led to higher branching density of the obtained copolymers.

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“…Polymerization of ethylene catalyzed by transition-metal complexes is one of the most industrially relevant synthetic reactions, and the development of high-performance catalysts continues to be a major driving force to access different polyethylene (PE) grades. − Beyond early and late transition-metal catalysts, − chromium catalysts are also of great interest, both homogeneous − and heterogeneous. − The peculiarity of homogeneous organochromium complexes is the ability to give linear α-olefins (selective tri- and tetramerization), high-density PE (HDPE) and even ultrahigh-molecular weight PE (UHMWPE) from ethylene. The selectivity may be obtained either by tuning the steric and electronic properties of the ligand , or by employing neutral donor molecules covalently linked to the chromium complex. , Generally, chromium complexes are renowned for their ability in the oligomerization of ethylene, , while examples of chromium complexes for UHMWPE production are rare. These include chromium complexes bearing β-ketoimines and β-diketimines, half-metallocene Cr(III) complexes bearing a N Λ O ligand, and salicylaldiminate Cr(III) complexes …”

Section: Introductionmentioning

confidence: 99%

“…11−13 The peculiarity of homogeneous organochromium complexes is the ability to give linear α-olefins (selective tri-and tetramerization), high-density PE (HDPE) and even ultrahigh-molecular weight PE (UHMWPE) from ethylene. The selectivity may be obtained either by tuning the steric and electronic properties of the ligand 8,9 or by employing neutral donor molecules covalently linked to the chromium complex. 14,15 Generally, chromium complexes are renowned for their ability in the oligomerization of ethylene, 16,17 while examples of chromium complexes for UHMWPE production are rare.…”

Section: Introductionmentioning

confidence: 99%

NEt₃-Triggered Synthesis of UHMWPE Using Chromium Complexes Bearing Non-innocent Iminopyridine Ligands

Zanchin¹,

Piovano

Amodio

et al. 2021

Macromolecules

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Chromium complexes bearing non-innocent iminopyridine ligands were investigated as precatalysts for the polymerization of ethylene using different aluminum cocatalysts and Lewis base NEt 3 as additive. Beyond confirming the key role of the chromium to ligand synergy in accessing the active complex, other factors that play a crucial role are (i) the nature of the aluminum activator that influences the ion pair generated, (ii) the presence of the additive that boosts the synthesis of UHMWPE with narrow and unimodal molecular weight distribution even at 40 °C, and (iii) the polymerization temperature that affects the polymerization catalysis and the polymer molecular weight. UV−vis−NIR and Fourier transform infrared (FT-IR) spectroscopic techniques have been applied to inspect the activation process and to understand the mode of action by which NEt 3 affects the catalytic conversion of ethylene. NEt 3 interacts with the aluminum cocatalyst (rather than with the chromium complex) to form an Et 3 N*AlR x adduct, thus affecting the catalytic ion pair.

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Recent progress in preparation of branched polyethylene with nickel, titanium, vanadium and chromium catalytic systems and EPR study of related catalytic systems

Cited by 15 publications

References 121 publications

Cobalt(ii) coordination to an N₄-acenaphthene-based ligand and its sodium complex

Cobalt(ii) coordination to an N₄-acenaphthene-based ligand and its sodium complex

Ethylene/α-olefin homo- and copolymerization using a dinuclear catalyst of nickel

NEt₃-Triggered Synthesis of UHMWPE Using Chromium Complexes Bearing Non-innocent Iminopyridine Ligands

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Recent progress in preparation of branched polyethylene with nickel, titanium, vanadium and chromium catalytic systems and EPR study of related catalytic systems

Cited by 15 publications

References 121 publications

Cobalt(ii) coordination to an N4-acenaphthene-based ligand and its sodium complex

Cobalt(ii) coordination to an N4-acenaphthene-based ligand and its sodium complex

Ethylene/α-olefin homo- and copolymerization using a dinuclear catalyst of nickel

NEt3-Triggered Synthesis of UHMWPE Using Chromium Complexes Bearing Non-innocent Iminopyridine Ligands

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Product

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Cobalt(ii) coordination to an N₄-acenaphthene-based ligand and its sodium complex

Cobalt(ii) coordination to an N₄-acenaphthene-based ligand and its sodium complex

NEt₃-Triggered Synthesis of UHMWPE Using Chromium Complexes Bearing Non-innocent Iminopyridine Ligands