Efficient incorporation of a polar comonomer for direct synthesis of hyperbranched polar functional ethylene oligomers

Li, Shuaikang; Lu, Zhou; Fan, Wenbing; Dai, Shengyu

doi:10.1039/d0nj05857b

Cited by 31 publications

(38 citation statements)

References 37 publications

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“…Further, the remote nonconjugated electronic and restricted-rotation effects on the polymerization process were studied. Our previous studies have shown that the remote nonconjugated electron effect significantly affects the polymerization activity, molecular weight, and branching density of the polyolefins in the α-diimine system. , However, in the iminopyridine Ni(II) system, the remote nonconjugated electronic substituents (H, Me, F, Cl) exhibited no significant effect on the polymerization parameters (Figure ). Our recent work has revealed a rotation-restricted dibenzosuberyl substituent can effectively retard the chain transfer during ethylene polymerization, thus, leading to a high molecular weight. ,,, The dibenzosuberyl substituent in the iminopyridine Ni(II) system demonstrated a significant impact on the molecular weight of the generated polyethylene.…”

Section: Resultsmentioning

confidence: 99%

“…The remote nonconjugated electronic effect (H, Me, F, Cl) on the molecular weight and branching density of the obtained products was also investigated. The catalysts with the electron withdrawing substituents (F, Cl) generated the products with lower molecular weight and higher branching density at 30 °C (Table , entries 5 and 7 vs 1 and 3), which was consistent with the previous studies . Similar to the nickel system, the restricted-rotation effect of the dibenzosuberyl substituent on the molecular weight of the obtained polyethylene was also significant in the case of the Pd(II) species.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis of Branched Polyethylene and Ethylene-MA Copolymers Using Unsymmetrical Iminopyridyl Nickel and Palladium Complexes

Wang

et al. 2021

Organometallics

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It is usually challenging to obtain high-molecular-weight polyethylene in the iminopyridyl Ni(II) and Pd(II) system due to the only one side axial steric structure of the iminopyridine ligand. In this study, the effectiveness of the dibenzosuberyl substituent in retarding the chain transfer in the iminopyridyl Ni(II) and Pd(II) catalysts has been demonstrated. The complexes Ni5 and Pd5 with phenyl and dibenzosuberyl substituents are noted to generate polyethylene and ethylene-MA copolymers with significantly higher molecular weight as compared to the complexes Ni1−4 and Pd1−4 with various diarylmethyl moieties. The synergistic effect of phenyl and dibenzosuberyl groups can further enhance the function of the catalyst to suppress the chain transfer. Further, polyethylene, ethylene oligomers, and ethylene-MA co-oligomers obtained in this study are observed to be highly branched. In addition, the iminopyridyl palladium catalysts can effectively promote the copolymerization of ethylene and MA to obtain the polar functionalized ethylene-MA co-oligomers with high incorporation ratios (up to 15.2 mol %).

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Synthesis of Branched Polyethylene and Ethylene-MA Copolymers Using Unsymmetrical Iminopyridyl Nickel and Palladium Complexes

Wang

et al. 2021

Organometallics

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“…However, the pyridine-imine system derived from same diarylmethyl anilines provides only branched ethylene oligomers. ( Chen et al, 2018 ; Li et al, 2021b ; Yan et al, 2021 ; Wang et al, 2020b ; Guo et al, 2019 ). In fact, since Laine et al reported that the first example of pyridine-imine nickel-catalyzed ethylene polymerization yielded low-molecular-weight branched polyethylene, ( Laine et al, 1999 ), many attempts, including the steric tuning of the o -aryl substituents, modifying the pyridine backbone and adjusting ligand electronic effect have been made to improve this situation, but no visible improvement was achieved ( Chart 1A ).…”

Section: Introductionmentioning

confidence: 99%

Synthesis of High-Molecular-Weight Branched Polyethylene Using a Hybrid “Sandwich” Pyridine-Imine Ni(II) Catalyst

Cai

Wang

et al. 2022

Front. Chem.

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Most pyridine-imine Ni(II) and Pd(II) catalysts tend to yield low-molecular-weight polyethylene and ethylene-based copolymers in olefin insertion polymerization, as the unilateral axial steric structure of such complexes often cannot provide effective shielding of the metal center. In this study, we synthesized a series of hybrid “semi-sandwich” and “sandwich” type pyridine-imine Ni(II) complexes by incorporating diarylmethyl or dibenzosuberyl groups onto 8-aryl-naphthyl motif. The as-prepared Ni(II) complexes afforded highly branched polyethylene with high molecular weights (level of 105 g/mol), and moderate activities (level of 105 g/(molh)) in ethylene polymerization. Most interestingly, compared to “semi-sandwich” Ni(II) complexes bearing (2-diarylmethyl-8-aryl)naphthyl units, the “full-sandwich” counterpart containing (2-dibenzosuberyl-8-aryl)naphthyl motif was able to produce higher-molecular-weight polyethylene with higher branching density. In addition, the effect of remote non-conjugated electronic substituents in diarylmethyl groups of the Ni(II) system was also observed in ethylene polymerization.

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“…The early and late transition metals homogeneous catalysts were used to prepare long‐chain olefins with ethylene oligomerization in the industry because they have the uniform and well‐defined active sites, the low electrophilicity, and the good tolerance to polar monomers, especially nickel and palladium metal catalysts. [ 2–5 ] It was well known that Ni/Pd‐based catalysts were prevalently used in olefin oligo‐/polymerization reactions, owing to their higher catalytic activity to guide reaction in the direction of specific objective products. [ 6–8 ] At present, many works focus on the effect of the ligand structure on the catalytic performance for olefin oligo‐/polymerization.…”

Section: Introductionmentioning

confidence: 99%

“…Li et al synthesized a series of iminopyridyl Pd(II) catalysts containing bulky diarylmethyl substituents with various remote nonconjugated electron‐withdrawing or ‐donating groups, and these catalysts possessing high catalytic activities and long half‐life at 50°C are capable of producing hyperbranched ethylene oligomers in ethylene oligomerization. [ 5 ]…”

Section: Introductionmentioning

confidence: 99%

Polynuclear (α‐diimine) nickel(II) complex as catalyst for ethylene oligomerization

Guo

et al. 2021

Applied Organom Chemis

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Late transition metal catalysts with single or multiple active centers have great attention in the ethylene oligomerization application owing to their unique properties. A new polynuclear (α‐diimine) nickel(II) complex (PS‐Ni complex) bearing the conjugated poly(Schiff‐base) ligand (PS‐ligand) was synthesized. The structures and the composition of the PS‐ligand and the PS‐Ni complex were characterized by Fourier transform infrared (FTIR) analysis, X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric (TG) analysis, nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The PS‐Ni complex was used as precatalyst in ethylene oligomerization combined with methylaluminoxane (MAO) and has good catalytic activity for ethylene oligomerization under mild conditions. Compared with the corresponding mononuclear (α‐diimine) nickel(II) complex, the PS‐Ni complex showed higher activity of 17.62 × 105 g/(mol Ni•h), and the main products were C4 and C6 olefins in cyclohexane when the dosage of precatalyst was 2 μmol, the Al/Ni molar ratio was 500, the ethylene pressure was 0.5 MPa, the reaction time was 60 min, and the reaction temperature was 25°C. The main oligomers were α‐olefins, and the selectivity was up to 98.68%, due to the more electron‐deficient catalytic centers of the conjugated structure of poly(Schiff‐base) ligand.

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Efficient incorporation of a polar comonomer for direct synthesis of hyperbranched polar functional ethylene oligomers

Abstract: A series of iminopyridyl Pd(II) catalysts containing bulky diarylmethyl substituents with various remote nonconjugated electron-withdrawing or -donating groups were synthesized and characterized. These catalysts possessing high catalytic activities and long...

Cited by 31 publications

References 37 publications

Synthesis of Branched Polyethylene and Ethylene-MA Copolymers Using Unsymmetrical Iminopyridyl Nickel and Palladium Complexes

Synthesis of Branched Polyethylene and Ethylene-MA Copolymers Using Unsymmetrical Iminopyridyl Nickel and Palladium Complexes

Synthesis of High-Molecular-Weight Branched Polyethylene Using a Hybrid “Sandwich” Pyridine-Imine Ni(II) Catalyst

Polynuclear (α‐diimine) nickel(II) complex as catalyst for ethylene oligomerization

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