Cooperative Heterobimetallic Catalysts in Coordination Insertion Polymerization

Cai, Zhongzheng; Xiao, Dawei; H., Loi

doi:10.1080/02603594.2019.1570165

Cited by 28 publications

(25 citation statements)

References 86 publications

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“…17,18 However, the concept remains underexplored in cyclic ester ROP despite heterometallic complexes with a M-O-M 0 (M s M 0 ) framework (and thus intermetallic electronic communication via the O heteroatom) having the potential to enhance monomer coordination by increasing the metal Lewis acidity and accelerate propagation by enhancing the metal-alkoxide nucleophilicity. 17,19 To date, the best performing heterometallic catalysts for LA and 3-CL ROP have generally comprised metals with large ionic radii and signicant electronegativity differences between the metals, e.g. Al/Zn, 20 La/Mg, 21 Li/In, 22 Li/Mg and Li/Zn, 23 Li/Sm, 24 Na/Sm, 25 Sm/Al 26 and Ti/Zn 27 (Fig.…”

Section: Introductionmentioning

confidence: 99%

Combining alkali metals and zinc to harness heterometallic cooperativity in cyclic ester ring-opening polymerisation

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Combining alkali metals and zinc to harness heterometallic cooperativity in cyclic ester ring-opening polymerisation

et al. 2020

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“…The metal‐metal and metal‐ligand interactions were introduced to explain the cooperative heterobimetallic catalysts in different platforms [15] . In a previous study, [24] it has been demonstrated that the addition of M + to NiL (L is phenoxyligand) can increase the catalytic efficiency up to 20 fold as well as polymer molecular weight and branching frequency in comparison to those without coadditives.…”

Section: Resultsmentioning

confidence: 99%

“…In the last decade, heterobimetallic catalysts which contain two different metals in a single platform have significantly improved the catalytic reactivity. [15][16][17] The heterobimetallic catalysts can enhance polymerization reactivity by multiple explicit interactions. [18] The use of two different metals possibly affects the olefin insertion and increases/decreases the rate of polymerization.…”

Section: Introductionmentioning

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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“…This approach, wherein two transition metal centers are present in close proximity, can thus elicit pronounced cooperative effects engendering greater polymerization activities and high molecular weight polymers . Polymerization catalysts in which redox-active metals like titanium or zirconium are paired with highly Lewis acidic metals like aluminum have attracted significant interest. − Along this line, Do and co-workers have prepared two families of heterobimetallic Ni and Pd complexes featuring pendant poly(ethylene glycol) that house Li + , Na + , and K + as Lewis acids. Their polymerization data display a significant increase in the polymerization activity, molecular weight, and branching frequency in contrast to their monometallic counterparts.…”

Section: Introductionmentioning

confidence: 99%

Heterobimetallic [Ti, Al] Complexes: Divergent Synthesis, Redox Properties, and Ethylene Polymerization Catalysis

et al. 2021

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Treatment of (Ind)(tBu 3 P = N)TiCl 2 (1; Ind = indenyl) with AlR 3 (R = Et, iBu, Me) affords heterobimetallic species of the form [(Ind)(tBu 3 PN)Ti(μ 2 -Cl) 2 AlR 2 ] (R = Et, 2-Et; iBu, 2-iBu; Me, 2-Me). The formation of these compounds occurs chemically or can be selectively triggered by electrochemical reduction of 1 in THF electrolyte solution containing AlR 3 . Cyclic voltammetry studies indicate that 1 undergoes one-electron reduction at ca. −2.0 V vs ferrocenium/ferrocene; in the presence of AlR 3 , reduction initiates coordination of [AlR 2 ] to the nascent [Ti III ] core and formation of 2-Me, 2-Et, and 2-iBu. Oxidation of these heterobimetallic species occurs at more positive potentials and leads to regeneration of 1. Single-crystal X-ray diffraction (XRD) analysis and magnetic resonance experiments confirm the formation of paramagnetic [Ti III , Al III ] species with each AlR 3 reagent. However, spectroscopic results and gas chromatography show that 2-Me is significantly less stable than 2-iBu and that 2-iBu is less stable than 2-Et. 2-Me, 2-Et, and 2-iBu are all active precatalysts for ethylene polymerization, but the diminished stability of 2-Me and 2-iBu in comparison with 2-Et is reflected in unique polymerization results in each case. 2-iBu produces polyethylene with a particularly broad molecular weight distribution (MWD), suggesting useful formation of multiple active species during catalysis. Conversely, 2-Me is a poor catalyst, suggesting detrimental speciation occurs with this system under the polymerization conditions.

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Cooperative Heterobimetallic Catalysts in Coordination Insertion Polymerization

Cited by 28 publications

References 86 publications

Combining alkali metals and zinc to harness heterometallic cooperativity in cyclic ester ring-opening polymerisation

Combining alkali metals and zinc to harness heterometallic cooperativity in cyclic ester ring-opening polymerisation

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

Heterobimetallic [Ti, Al] Complexes: Divergent Synthesis, Redox Properties, and Ethylene Polymerization Catalysis

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