Density functional study for the polymerization of ethylene monomer using a new nickel catalyst

Ramos, Javier; Cruz, Víctor L.; Martínez‐Salazar, Javier; Brasse, Mikaël; Palma, Pilar; Cámpora, Juan

doi:10.1002/pola.23874

Cited by 9 publications

(5 citation statements)

References 33 publications

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“…Termination: In a similar way to that observed in the quantum chemical calculations on the square-planar ethylene alkyl complexes (7 a and 7 b, Scheme 4), [70,[84][85][86][87][88][89] the phosphine alkyl complexes (1 a and 1 b, Scheme 4) display preferences with respect to cis/trans isomerization. Higher energies were obtained for isomers with the propyl trans to the more strongly donating and more sterically hindered phosphorus (for I) or nitrogen (for II and III), that is, the relative energies of these isomers were found to be 1 a < 1 b.…”

Section: Resultssupporting

confidence: 69%

“…Propagation: A number of computational investigations have concluded that, in the case of (k 2 -P,O) or (k 2 -N,O) asymmetric bidentate ligands with d 8 square-planar geometries, the energetically most favorable ethylene insertion transition state involves the alkyl chain trans to the more sterically hindered and strongly donating phosphorus or nitrogen of the bidentate ligand, that is, 7 b_TS in Scheme 4. [70,[84][85][86][87][88][89] The energetically most favorable ethylene p complexes, on the other hand, most commonly have the alkyl chain situated cis to the more sterically hindered and strongly donating phosphorus or nitrogen of the bidentate ligand, as in complex 7 a in Scheme 4. For catalysts II and III, however, the relative stabilities of the two isomers are typically very similar (within 1.0 kcal mol À1 ), [70,84,85] consistent with our free-energy differences of 0.8 and À0.1 kcal mol À1 for isomers 7 a and 7 b, respectively (see Table 2).…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

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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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Section: Resultssupporting

confidence: 69%

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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“…The MD method is a deterministic technique that simulates the motion of a system under the influence of a given potential [FF, as that shown in Equation 16] by following molecular conformations according to Newton's equation of motion. The system of equations of motion of N particles is: (17) The time evolution of the particles (trajectory) is obtained by integrating the equations of motion [Equation (17)] over discrete steps in time (time-step, ∆t) using a finite difference method. The time-step must be sufficiently small to avoid discrete integration errors.…”

Section: Molecular Dynamics (Md)mentioning

confidence: 99%

“…With regards to polymer physics, PE is undoubtedly the most studied polymer. The reasons for this are its chemical simplicity, its high level of production in the last 50 years and the availability of model materials obtained by different synthetic routes (long chain paraffins [2], single-site catalyst PE that include modelling reactions [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and hydrogenated polybutadienes [22][23][24]. In addition, architecture is generally well characterized.…”

Section: Introductionmentioning

confidence: 99%

Predicting experimental results for polyethylene by computer simulation

Ramos

Vega

Martínez‐Salazar

2018

European Polymer Journal

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This feature article reviews several aspects of computational approaches to polyethylene melt and solid state properties in relation to existing experimental results. Based on 40 years of experience in the field, we offer a personal view of how computer simulations are helping to understand the physics of polyethylene as a model polymer. The first issue discussed is the molten state of polyethylene, including static and dynamic properties and entanglement features along with their impacts on rheological behaviour. We then examine the glass transition, crystallization process and solid state structure, including the interlamellar region. This is followed by brief descriptions of the latest advances in simulating mechanical properties and of the various methodologies used to simulate the physics of polyethylene. Throughout the manuscript, references are made to our own work and also to studies by many other authors that have nicely contributed to developments in simulating the physics of polyethylene in close agreement with experimental results.

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“…Several studies have also theoretically addressed catalyst behavior during polymerization. − Our group has actively contributed to this field with a number of computational studies. − For this type of study, density functional theory (DFT) has allowed the treatment of polymerization catalyst systems using the computational resources available at the time over the past 20 years.…”

Section: Introductionmentioning

confidence: 99%

3D-QSAR as a Tool for Understanding and Improving Single-Site Polymerization Catalysts. A Review

Cruz

Martínez²,

Ramos

et al. 2014

Organometallics

Self Cite

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This paper reviews the findings of quantitative structure−activity relationship (QSAR) studies focusing on single-site polymerization catalysts, with special attention paid to the use of 3D-QSAR tools. Such tools reveal the fine details of catalyst structure that may be correlated with polymerization activity or the properties of the synthesized polymer. The introduction of effective single-site polymerization catalysts, in addition to allowing scientists to synthesize new tailor-made polymers, has enabled a detailed theoretical analysis of the synthesis process. The benefits of single-site polymerization for theoretical studies include easy elucidation of the catalyst structure, a well-defined mechanism of action, and the fact that experiments can be systematically conducted on catalyst series featuring different substitution patterns. Using QSAR methods, experimental results can be related to theoretical measurements through statistical or chemometric tools. These tools have been extensively and successfully used in the field of drug design.

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Density functional study for the polymerization of ethylene monomer using a new nickel catalyst

Cited by 9 publications

References 33 publications

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

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

Predicting experimental results for polyethylene by computer simulation

3D-QSAR as a Tool for Understanding and Improving Single-Site Polymerization Catalysts. A Review

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