A zwitterionic nickel–olefin initiator for the preparation of high molecular weight polyethylene

Chen, Yaofeng; Boardman, Brycelyn M.; Bazan, Guillermo C.

doi:10.1016/j.jorganchem.2007.05.016

Cited by 18 publications

(7 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[53][54][55][56][57] Nevertheless, most of the aforementioned metal catalysts, both early and late metal ones, required the activation of a large amount of aluminium compounds, the residue of which proved to be detrimental to the resulting polymer materials; catalytic systems that do not need the help of aluminum compounds were thus highly desirable. Thanks to its unique property, Lewis acidic B(C 6 F 5 ) 3 has been widely used as an activator in ethylene polymerization, [58][59][60][61][62][63][64][65] and thus is also attractive in norbornene polymerizations. Janiak's group reported that nickel(II) complexes bearing bidentate phosphane ligands showed activities of 10 3 -10 4 g PNB mol Ni −1 h −1 when activated with B(C 6 F 5 ) 3 /TEA, which was similar to that of the MAO promoted systems 66 and it was possible to activate some of these complexes with B(C 6 F 5 ) 3 alone.…”

Section: Introductionmentioning

confidence: 99%

Well-defined phosphino-phenolate neutral nickel(ii) catalysts for efficient (co)polymerization of norbornene and ethylene

Zhang

et al. 2015

Dalton Trans.

View full text Add to dashboard Cite

Phosphino-phenolate neutral nickel catalysts 1-3/B(C6F5)3, without the help of any organoaluminum compound, were found to be efficient catalytic systems for norbornene polymerization and its copolymerization with norbornene derivatives. The amount of B(C6F5)3 required for achieving a high efficiency (3 equiv.) was markedly lower compared to previous reports, and high molecular weight polymers were obtained (>10(6) g mol(-1)). Efficient incorporation of polar monomers NBC, NBA, and NBM was also achieved in a controllable fashion, yielding high molecular weight copolymers. Catalysts 1-3 were highly active for ethylene polymerization as single component catalysts, with an activity of up to 10(7) g molNi(-1) h(-1), and catalyst 3 was more readily initiated at lower temperature. Catalysts 1-3 were also efficient in incorporating norbornene (up to 30%) into the polyethylene backbone. Bisligated phosphino-phenolate nickel complex 4 and salicylaldimine complex 5 were also studied for comparison, which further verified the unique performance of catalysts 1-3. Preliminary NMR analyses were conducted to explore the norbornene polymerization mechanism.

show abstract

Section: Introductionmentioning

confidence: 99%

Well-defined phosphino-phenolate neutral nickel(ii) catalysts for efficient (co)polymerization of norbornene and ethylene

Zhang

et al. 2015

Dalton Trans.

View full text Add to dashboard Cite

show abstract

“…A direct conversion from a neutral to a cationic active site was possible by binding of a Lewis acidic borane in a remote position of the ligand framework. Bazan et al reported neutral catalysts, which can be converted to a zwitterionic structure with a formal cationic charge on the metal ion. − For various different structures studied, the formation of the zwitterionic structure leads to an increase in ethylene polymerization activity. A similar approach was possible for Pd(II) phosphine-sulfonato catalysts .…”

Section: Introductionmentioning

confidence: 99%

The Impact of Charge in a Ni(II) Polymerization Catalyst

et al. 2021

View full text Add to dashboard Cite

A direct comparison between neutral active sites and their corresponding cationic analogues is enabled by protonation of neutral bis(imino)phenoxy complexes, active for ethylene polymerization. The additional imine motif compared to parent salicylaldiminato catalysts does not influence the microstructure of the products in ethylene polymerization, but allows for the incorporation of a proton right next to the active center in an N•••H + •••O bridge yielding cationic complexes. These show an increased Ni−O bond length and a drastically reduced electron density on the Ni atom. In pressure reactor experiments, two different catalysts that produce linear HDPE or undergo extensive chain walking, respectively, in their neutral version, both produce short chain oligomers when the catalyst is charged cationically. A mechanistic analysis by DFT methods reveals an increased propensity for β-hydride elimination compared to ethylene insertion chain growth for the cationic complexes. This results from a higher relative stability of β-agostic species vs olefin-coordinated species.

show abstract

“…Such stimuli include redox reagents, light, applied voltage or current, and mechanical force, each of which will be a focus of this review. However, it should also be noted that several other stimuli have been explored within the literature, including addition and/or removal of Cl, metal cations, − borane − to induce allosteric effects, CO 2 − and O 2 − as sources of gas-regulated systems, and acids and/or bases for pH-regulated systems, − but they fall outside the scope of topics discussed in this review.…”

Section: Introductionmentioning

confidence: 99%

Advances in Polymerizations Modulated by External Stimuli

et al. 2020

View full text Add to dashboard Cite

Synthetic polymer chemistry endeavors to imitate the spatial and temporal control exhibited within biological systems to obtain well-defined polymeric materials with unique structures, properties, and applications. This is often approached through the development of dynamic catalyst (or initiator) systems that use external stimuli to elicit discrete, site-specific transformations that impact the polymerization. Herein we highlight developments in polymerizations that are modulated by external stimuli, with particular focus on those systems that enable notable changes in kinetics, monomer selectivity, polymer architecture, or tacticity. Examples of external stimuli include chemical oxidants or reductants, light, applied voltage, and mechanical force.

show abstract

A zwitterionic nickel–olefin initiator for the preparation of high molecular weight polyethylene

Cited by 18 publications

References 25 publications

Well-defined phosphino-phenolate neutral nickel(ii) catalysts for efficient (co)polymerization of norbornene and ethylene

Well-defined phosphino-phenolate neutral nickel(ii) catalysts for efficient (co)polymerization of norbornene and ethylene

The Impact of Charge in a Ni(II) Polymerization Catalyst

Advances in Polymerizations Modulated by External Stimuli

Contact Info

Product

Resources

About