Mechanistic Aspects of Olefin-polymerization Catalysis

Piers, Warren E.; Collins, Scott

doi:10.1016/b0-08-045047-4/00006-6

Cited by 2 publications

(3 citation statements)

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“…The discovery that homogeneous late transition metal catalysts can exhibit olefin polymerization activity similar to that of early transition metal catalysts led to a major paradigm shift in olefin polymerization catalysis. − Because late transition metal catalysts (e.g., Ni, Pd) are far less susceptible to inhibition by heteroatom donors compared to their early transition metal counterparts (e.g., Ti, Hf, Zr), the former typically exhibit greater tolerance of polar monomers, solvents, and impurities compared to the latter. Although recent developments in nickel and palladium catalysis have led to the creation of systems that can copolymerize ethylene and polar vinyl monomers through a coordination–insertion mechanism, − the resulting polymers tend to have low molecular weight and the catalyst activity tends to be poor.…”

Section: Introductionmentioning

confidence: 99%

Fine-Tuning Nickel Phenoxyimine Olefin Polymerization Catalysts: Performance Boosting by Alkali Cations

Cai

Xiao

2015

J. Am. Chem. Soc.

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To gain a better understanding of the influence of cationic additives on coordination-insertion polymerization and to leverage this knowledge in the construction of enhanced olefin polymerization catalysts, we have synthesized a new family of nickel phenoxyimine-polyethylene glycol complexes (NiL0, NiL2-NiL4) that form discrete molecular species with alkali metal ions (M(+) = Li(+), Na(+), K(+)). Metal binding titration studies and structural characterization by X-ray crystallography provide evidence for the self-assembly of both 1:1 and 2:1 NiL:M(+) species in solution, except for NiL4/Na(+) which form only the 1:1 complex. It was found that upon treatment with a phosphine scavenger, these NiL complexes are active catalysts for ethylene polymerization. We demonstrate that the addition of M(+) to NiL can result in up to a 20-fold increase in catalytic efficiency as well as enhancement in polymer molecular weight and branching frequency compared to the use of NiL without coadditives. To the best of our knowledge, this work provides the first systematic study of the effect of secondary metal ions on metal-catalyzed polymerization processes and offers a new general design strategy for developing the next generation of high performance olefin polymerization catalysts.

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Section: Introductionmentioning

confidence: 99%

Fine-Tuning Nickel Phenoxyimine Olefin Polymerization Catalysts: Performance Boosting by Alkali Cations

Cai

Xiao

2015

J. Am. Chem. Soc.

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“…Second, although the Ni catalysts all successfully catalyzed ethylene and MA copolymerization, they typically showed low activity (<5 kg mol –1 h –1 ) with the exception of J (86 kg mol –1 h –1 ). The reduced reactivity of metal catalysts in the presence of functional olefins is attributed to σ-coordination of the polar group to the active catalyst or back-chelation by an inserted polar monomer . Third, symmetric catalyst I appears to perform just as well as, if not better than, most of the asymmetric catalysts.…”

Section: Resultsmentioning

confidence: 97%

“…The reduced reactivity of metal catalysts in the presence of functional olefins is attributed to σ-coordination of the polar group to the active catalyst or back-chelation by an inserted polar monomer. 50 Third, symmetric catalyst I appears to perform just as well as, if not better than, most of the asymmetric catalysts. Thus, it is unclear if asymmetric catalysts have any intrinsic advantages over symmetric ones in terms of their ability to copolymerize polar monomers.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Rigidifying Cation-Tunable Nickel Catalysts Increases Activity and Polar Monomer Incorporation in Ethylene and Methyl Acrylate Copolymerization

Tahmouresilerd

Xiao

2021

Inorg. Chem.

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In this study, we synthesized and characterized two nickel complexes featuring conformationally rigid bisphosphine mono-oxide ligands, where one has an o-methoxyphenyl (Ni2) and the other has an o-(2-methoxyethoxy)phenyl (Ni3) substituent on the PO moiety. We performed metal binding studies using Ni3 and found that its reaction with Li+ and Na+ most likely produced 1:1 and 1:1/2:1 nickel:alkali species in solution, respectively. The nickel complexes were competent catalysts for ethylene homopolymerization and copolymerization, with activities up to 3.8 × 103 and 8.1 × 10 kg mol–1 h–1, respectively. In reactions of ethylene with methyl acrylate (1.0 M), the addition of Li+ to Ni3 led to a 5.4-fold enhancement in catalyst activity and a 1.9-fold increase in polar monomer incorporation in comparison to those by Ni3 alone under optimized conditions. A comparison with other nickel catalysts reported for ethylene and methyl acrylate copolymerization revealed that our nickel–alkali catalysts are competitive with some of the most efficient Ni-based systems developed thus far.

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Mechanistic Aspects of Olefin-polymerization Catalysis

Cited by 2 publications

References 293 publications

Fine-Tuning Nickel Phenoxyimine Olefin Polymerization Catalysts: Performance Boosting by Alkali Cations

Fine-Tuning Nickel Phenoxyimine Olefin Polymerization Catalysts: Performance Boosting by Alkali Cations

Rigidifying Cation-Tunable Nickel Catalysts Increases Activity and Polar Monomer Incorporation in Ethylene and Methyl Acrylate Copolymerization

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