Development of highly productive nickel–sodium phenoxyphosphine ethylene polymerization catalysts and their reaction temperature profiles

Tran, Thi V.; Nguyen, Yennie H.; H., Loi

doi:10.1039/c9py00610a

Cited by 30 publications

(41 citation statements)

References 26 publications

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“…We had shown previously that conventional nickel phenoxyphosphine complexes lacking ortho PEG groups do not bind secondary metals to an appreciable extent. 51 In contrast, Ni3 produced discrete 1:1 nickel−sodium species in solution and the The examples shown were reported by Brookhart/Johnson (left), 39 Do (middle), 40,41 and Tonks (right) 42 solid state. To investigate whether Ni3 could form adducts with other alkali ions, we performed metal ion titrations using UV− visible absorption spectroscopy.…”

Section: ■ Results and Discussionmentioning

confidence: 91%

“…They include complexes based on phenoxyimine, 40,41 phosphine phosphonate ester, 49,50 and phenoxyphosphine. 51 The PEG groups are integral to our catalyst design because they provide well-defined secondary metal binding pockets for a variety of metal cations. It has also been used successfully as a ligand substituent by Zhang and Chen.…”

Section: ■ Introductionmentioning

confidence: 99%

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Elucidating Secondary Metal Cation Effects on Nickel Olefin Polymerization Catalysts

Tran

Karas

et al. 2020

ACS Catal.

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Secondary metal cations, such as alkali and transition metal ions, have been shown to enhance the catalytic performance of nickel and palladium olefin polymerization catalysts. Their beneficial effects can manifest in different ways, such as increasing rates of polymerization, altering polymer microstructures, enhancing catalyst thermal stability, or a combination of these effects. We have systematically quantified secondary metal ion influences on nickel phenoxyphosphine polyethylene glycol (PEG) complexes. We demonstrate that cation tuning could readily achieve three-dimensional structures and electronic environments that are not easily accessible through conventional ligand tuning. This study led to the development of extremely active ethylene polymerization catalysts. For example, the nickel–lithium complex gave activity and turnover number as high as 7.0 × 104 kg PE/mol Ni·h and 2.5 × 106 mol ethylene/mol Ni, respectively, and the nickel–cesium complex showed unusual thermal stability up to 90 °C (activity = 2.3 × 104 kg/mol h, turnover number = ∼4.1 × 105 mol ethylene/mol Ni, and M n = 1.6 × 104 g/mol). We provide both experimental and computational data showing that secondary metals impact the relative stability of cis and trans isomers, which is a phenomenon not shown previously. Unlike in our earlier work, which was limited by poor nuclearity control and/or secondary metals that were too far from the catalyst center, the nickel phenoxyphosphine–PEG complex is an ideal platform for future studies of cation-controlled polymerization.

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Section: ■ Results and Discussionmentioning

confidence: 91%

Section: ■ Introductionmentioning

confidence: 99%

Elucidating Secondary Metal Cation Effects on Nickel Olefin Polymerization Catalysts

Tran

Karas

et al. 2020

ACS Catal.

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“…Meanwhile the development of low cost nickel-based catalysts for this purpose is highly challenging . In contrast to the rapidly growing family of potent palladium catalysts, only a few nickel catalysts exhibit high activity for ethylene copolymerization with fundamental polar monomers . It is worth noting that some phosphine-containing nickel catalysts have emerged as alternatives for ethylene copolymerization, possessing comparable or even better properties than some palladium catalysts in copolymerization reactions …”

Section: Introductionmentioning

confidence: 99%

Enhancing Chain Initiation Efficiency in the Cationic Allyl-Nickel Catalyzed (Co)Polymerization of Ethylene and Methyl Acrylate

et al. 2020

Inorg. Chem.

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Improving the efficiency of chain initiation is highly important and also highly challenging in the development of olefin polymerization catalysts. A series of 2-methylallyl-based nickel complexes supported by aryl-N-bridged diphosphazane monoxide (PNPO) ligands containing different electronic and steric substituents were prepared and characterized. These nickel complexes are highly active single-component catalysts for ethylene polymerization and copolymerization with methyl acrylate (MA). 2-Methylallyl substituent on the μ-allyl catalysts led to an increase in the efficiency of chain initiation compared with the corresponding allyl-based analogues, improving the catalytic performances with high activity (up to 4.02 × 10 6 g PE (mol Ni) −1 h −1 ). Linear polyethylenes with high molecular weight, narrow PDI values, and high melting temperatures were generated. Most importantly, these 2-methylallyl nickel catalysts can promote ethylene-MA copolymerization to afford functionalized polyethylenes with MA incorporation of up to 7.0 mol %. The current work demonstrates that the change of initiating units can lead to enhancement in catalyst performances. This provides an alternative, simple, and potentially general strategy to improve the properties of different catalyst systems.

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“…Using X-ray structures of Ni-PEG with alkali metals, [28][29] pre-reaction structures (Figure 9, left) with two different geometric isomers A and B were optimized, and their relative stabilities were compared for four kinds of Ni-PEG(M + ) catalytic systems as given in Figure S16 of supplementary material. According to an experiment, phosphine abstraction is the first step in the activation process.…”

Section: Computational Modelsmentioning

confidence: 99%

Exploring the Reaction Mechanism of Heterobimetallic Nickel‐Alkali Catalysts for Ethylene Polymerization: Secondary‐Metal‐Ligand Cooperative Catalysis

et al. 2022

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In this work, we explored the reaction mechanism of heterobimetallic nickel phenoxyphosphine polyethylene glycol (Ni-PEG) with alkali metals (M + = Li + , Na + , K + , and Cs + ) catalysts for ethylene polymerization using the DFT calculations. The activation energy of the necessary step shows the following trend, Li + < Na + < K + < Cs + , which corresponds to experimentally observed activities. Roles of secondary metals (M + ) in Ni-PEG catalysts were clarified. Our findings suggest that the active catalyst should contain strong cooperative metal-metal/metal-ligand interactions and less positive charge on M + cation. Besides, the key role of M + is to control the PEG group which stabilizes the catalyst structure. In addition, we found two key factors (shorter M-O 1 and M-O PEG distances) for designing new catalysts from the pre-reaction state of the Ni-PEG(M + ) catalysts. Finally, Ni-PEG(M 2 + ) catalysts with Be 2 + , Mg 2 + , Co 2 + , and Zn 2 + were suggested for candidates of highly active catalysts for ethylene polymerization.

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Development of highly productive nickel–sodium phenoxyphosphine ethylene polymerization catalysts and their reaction temperature profiles

Abstract: Heterobimetallic nickel–sodium phenoxyphosphine complexes were found to be among one of the most efficient late metal catalysts for ethylene polymerization.

Cited by 30 publications

References 26 publications

Elucidating Secondary Metal Cation Effects on Nickel Olefin Polymerization Catalysts

Elucidating Secondary Metal Cation Effects on Nickel Olefin Polymerization Catalysts

Enhancing Chain Initiation Efficiency in the Cationic Allyl-Nickel Catalyzed (Co)Polymerization of Ethylene and Methyl Acrylate

Exploring the Reaction Mechanism of Heterobimetallic Nickel‐Alkali Catalysts for Ethylene Polymerization: Secondary‐Metal‐Ligand Cooperative Catalysis

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