Ethylene Polymerization Characteristics of an Electron-Deficient Nickel(II) Phenoxyiminato Catalyst Modulated by Non-Innocent Intramolecular Hydrogen Bonding

Delferro, Massimiliano; McInnis, Jennifer P.; Marks, Tobin J.

doi:10.1021/om100251j

Cited by 45 publications

(36 citation statements)

References 91 publications

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“…Microstructural analysis of the polyethylenes produced by (CF 3 )FI 2 ‐Ni(OH) indicates lower M w polyethylene with similar branch numbers versus the polyethylenes produced by (CF 3 )FI 2 ‐Ni 2 . In previous work, the effects of installing an intramolecular hydrogen bond directed toward a polymerization‐active Ni II center were investigated,14c and it was concluded that installing the hydrogen bond adjacent to the Ni center leads to a more electron‐deficient catalyst as shown below; see also ref. 14c), increasing ethylene polymerization activity and depressing product polyethylene M w .…”

Section: Discussionmentioning

confidence: 99%

“…In previous work, the effects of installing an intramolecular hydrogen bond directed toward a polymerization‐active Ni II center were investigated,14c and it was concluded that installing the hydrogen bond adjacent to the Ni center leads to a more electron‐deficient catalyst as shown below; see also ref. 14c), increasing ethylene polymerization activity and depressing product polyethylene M w . Similar conclusions can be drawn here when the polymerization results for (CF 3 )FI 2 ‐N i(OH) and (CF 3 )FI 2 ‐N i 2 are compared.…”

Section: Discussionmentioning

confidence: 99%

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Ligand Steric and Fluoroalkyl Substituent Effects on Enchainment Cooperativity and Stability in Bimetallic Nickel(II) Polymerization Catalysts

Weberski

Chen

Delferro

et al. 2012

Chemistry A European J

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114

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The synthesis and characterization of two neutrally charged bimetallic Ni(II) ethylene polymerization catalysts, {2,7-di-[2,6-(3,5-di-methylphenylimino)methyl]1,8-naphthalenediolato}-bis-Ni(II) (methyl)(trimethylphosphine) [(CH(3) )FI(2) -Ni(2) ] and {2,7-di-[2,6-(3,5-di-trifluoromethyl-phenylimino)methyl]-1,8-naphthalenediolato}-bis-Ni(II) (methyl)(trimethyl-phosphine) [(CF(3) )FI(2) -Ni(2) )], are reported. The diffraction-derived molecular structure of (CF(3) )FI(2) -Ni(2) reveals a Ni⋅⋅⋅Ni distance of 5.8024(5) Å. In the presence of ethylene and Ni(COD)(2) or B(C(6) F(5) )(3) co-catalysts, these complexes along with their monometallic analogues [2-tert-butyl-6-((2,6-(3,5-dimethylphenyl)phenylimino)methyl)-phenolate]-Ni(II) -methyl(trimethylphosphine) [(CH(3) )FI-Ni] and [2-tert-butyl-6-((2,6-(3,5-ditrifluoromethyl-phenyl)phenylimino)methyl)phenolato]-Ni(II) -methyl-(trimethylphosphine) [(CF(3) )FI-Ni], produce polyethylenes ranging from highly branched M(w) =1400 oligomers (91 methyl branches per 1000 C) to low branch density M(w) =92 000 polyethylenes (7 methyl branches per 1000 C). In the bimetallic catalysts, Ni⋅⋅⋅Ni cooperative effects are evidenced by increased product polyethylene branching in ethylene homopolymerizations (∼3× for (CF(3) )FI(2) -Ni(2) vs. monometallic (CF(3) )FI-Ni), as well as by enhanced norbornene co-monomer incorporation selectivity, with bimetallic (CH(3) )FI(2) -Ni(2) and (CF(3) )FI(2) -Ni(2) enchaining approximately three- and six-times more norbornene, respectively, than monometallic (CH(3) )FI-Ni and (CF(3) )FI-Ni. Additionally, (CH(3) )FI(2) -Ni(2) and (CF(3) )FI(2) -Ni(2) exhibit significantly enhanced thermal stability versus the less sterically encumbered dinickel catalyst {2,7-di-[(2,6-diisopropylphenyl)imino]-1,8-naphthalenediolato}-bis-Ni(II) (methyl)(trimethylphosphine). The pathway for bimetallic catalyst thermal deactivation is shown to involve an unexpected polymerization-active intermediate, {2,7-di-[2,6-(3,5-di-trifluoromethyl-phenylimino)methyl]-1-hydroxy,8-naphthalenediolato-Ni(II) (methyl)-(trimethylphosphine).

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Ligand Steric and Fluoroalkyl Substituent Effects on Enchainment Cooperativity and Stability in Bimetallic Nickel(II) Polymerization Catalysts

Weberski

Chen

Delferro

et al. 2012

Chemistry A European J

Self Cite

114

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“…This means the approximate [eth] of 1 m is an underestimation and b is therefore somewhat overestimated, but still small enough to meet the experimental requirement. The lower molecular weights observed from polymerizations in the absence of phosphine but in the presence of coordinating solvents (for example, tetrahydrofuran, di-A C H T U N G T R E N N U N G methyl ether, and acetone) or additives (for example, ethyl oleate, pyridine, and tetrahydrothiophene) [56,72,111] naturally lead to speculation that these molecules may play a role similar to phosphine in the termination pathway described in Scheme 4. However, this aspect is outside the scope of this paper but could be an interesting subject for a future study.…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

Neutral Nickel Oligo‐ and Polymerization Catalysts: The Importance of Alkyl Phosphine Intermediates in Chain Termination

Heyndrickx¹,

Occhipinti²,

Minenkov³

et al. 2011

Chemistry A European J

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An unconventional chain termination reaction has been explored for the SHOP (Shell higher olefin process)-type, anilinotropone, and salicylaldiminato nickel-based oligo- and polymerization catalysts by using density functional theory (DFT). Starting from the tetracoordinate alkyl phosphine complex, the termination reaction was found to involve a rearrangement of the alkyl chain to form a pentacoordinate β-agostic complex, β-hydride elimination, and olefinic chain dissociation and to compete with propagation at sufficiently high phosphine concentration and/or basicity. It provides the first complete and convincing mechanistic rationale for the decreasing chain lengths observed upon increasing phosphine concentration and basicity. The unconventional reaction was found to be a major termination pathway for the SHOP-type catalyst and is very unlikely to lead to branching and olefin isomerization, which is critical for explaining why the SHOP catalyst, in contrast to the anilinotropone and salicylaldiminato catalysts, tends to lead to the oligomerization of ethylene to form linear α-olefins. Based on our results we have proposed a new and extended catalytic cycle for the SHOP-type ethylene oligomerization catalyst. Finally, the importance of the new termination reaction for the SHOP-type catalyst suggests that this reaction may also operate with other ethylene oligomerization nickel catalysts. This prediction was confirmed for a pyrazolonatophosphine catalyst, for which the new termination route was found to be even more facile, which explains the short oligomers produced by this catalyst.

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“…Thus, the presence of bulky substituents in the backbone of the salicylamidinato ligand is a key requirement to generate highly active nickel catalysts for olefin polymerization. [55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71] On the other hand, the use of less sterically encumbered phenoxy-imine ligands afforded predominantly nickel catalysts for ethylene oligomerization. [72][73][74][75][76] Selected examples are presented in Chart 1.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of Ni (II) complexes supported by phenoxy/naphthoxy‐imine ligands with pendant N‐ and O‐donor groups and their use in ethylene oligomerization

Oliveira

Silva

Casagrande

et al. 2018

Applied Organom Chemis

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A series of new Ni(II) complexes of general formula Ni{ZNO} Br (2a‐i) (ZNO = phenoxy/naphthoxy‐imine with pendant N‐ and O‐donor groups) were prepared and characterized by elemental analysis, IR spectroscopy, ESI‐HRMS, and by X‐ray crystallography for 2e. In the solid state, 2e features a monomeric structure with κ3 coordination of the monoanionic naphthoxy‐imine‐quinoline ligand onto the nickel center. Upon activation with MAO, both classes of nickel catalysts were able to produce selectively 1‐butene (81.5–92.1 wt%) with turnover frequencies (TOFs) varying from 3,100 to 24,300 mol(C2H4) mol (Ni)−1 h−1. Nickel precatalysts bearing phenoxy‐imine ligands were much more active than its naphthoxy analogous under the same conditions. The use of a mixture of cocatalysts (MAO/TMA or MAO/TiBA) resulted in poor activities; however the presence of TiBA in the milieu led to a significant improvement on selectivity for 1‐hexene (25.5 wt%). Under optimized conditions ([Ni] = 10 μmol, 30 °C, oligomerization time = 5 min, 20 bar ethylene, [Al]/[Ni] = 600), precatalyst 2c led to TOF = 59,900 mol(C2H4) mol(Ni)−1 h−1 and selectivity for 1‐butene of 89.5 wt%.

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Ethylene Polymerization Characteristics of an Electron-Deficient Nickel(II) Phenoxyiminato Catalyst Modulated by Non-Innocent Intramolecular Hydrogen Bonding

Cited by 45 publications

References 91 publications

Ligand Steric and Fluoroalkyl Substituent Effects on Enchainment Cooperativity and Stability in Bimetallic Nickel(II) Polymerization Catalysts

Ligand Steric and Fluoroalkyl Substituent Effects on Enchainment Cooperativity and Stability in Bimetallic Nickel(II) Polymerization Catalysts

Neutral Nickel Oligo‐ and Polymerization Catalysts: The Importance of Alkyl Phosphine Intermediates in Chain Termination

Synthesis and characterization of Ni (II) complexes supported by phenoxy/naphthoxy‐imine ligands with pendant N‐ and O‐donor groups and their use in ethylene oligomerization

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