The influence of the ligand structure on activation of hafnocene polymerization catalysts: A theoretical study

Karttunen, Virve A.; Linnolahti, Mikko; Turunen, Anniina; Pakkanen, Tapani A.; Severn, John R.; Maaranen, Janne; Kokko, Esa; Pitkänen, Päivi

doi:10.1016/j.jorganchem.2007.10.037

Cited by 13 publications

(24 citation statements)

References 42 publications

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“…1 ) to active catalysts but the precise action mechanism of MAO are unclear. Computational study of the initiation process is challenging due to the elusive MAO, which could be one of reasons why computational studies of olefin polymerization often did not include counterion . Nevertheless, there were computational attempts to attack the issue.…”

Section: Resultsmentioning

confidence: 99%

“…In the past decades, many computational studies have been reported to understand the mechanisms of transition metal‐catalyzed olefin polymeriza‐tions . Karttunen et al studied the influences of the ligands on hafnocene‐catalyzed polymerization computationally, and found that steric effects of the ligand affect the activation energy in chain propagation. Yang et al's DFT study of Ti‐catalyzed copolymerization of ethylene and styrene indicated that styrene prefers 1,2‐insertion to 2,1‐insertion initially, but the subsequent styrene insertion is dominated by 2,1‐insertion mode.…”

Section: Introductionmentioning

confidence: 99%

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DFT mechanistic study of the H₂-assisted chain transfer copolymerization of propylene andp-methylstyrene catalyzed by zirconocene complex

Zhang

et al. 2014

J. Polym. Sci. Part A: Polym. Chem.

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DFT computations have been performed to investigate the mechanism of H 2 -assisted chain transfer strategy to functionalize polypropylene via Zr-catalyzed copolymerization of propylene and p-methylstyrene (pMS). The study unveils the following: (i) propylene prefers 1,2-insertion over 2,1-insertion both kinetically and thermodynamically, explaining the observed 1,2-insertion regioselectivity for propylene insertion. (ii) The 2,1-inserion of pMS is kinetically less favorable but thermodynamically more favorable than 1,2-insertion. The observation of 2,1-insertion pMS at the end of polymer chain is due to thermodynamic control and that the barrier difference between the two insertion modes become smaller as the chain length becomes longer. (iii) The pMS insertion results in much higher barriers for subsequent either propylene or pMS insertion, which causes deactivation of the catalytic system. (iv) Small H 2 can react with the deactivated [Zr]2pMS2PP n facilely, which displace functionalized pMS2PP n chain and regenerate [Zr]AH active catalyst to continue copolymerization. The effects of counterions are also discussed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

DFT mechanistic study of the H₂-assisted chain transfer copolymerization of propylene andp-methylstyrene catalyzed by zirconocene complex

Zhang

et al. 2014

J. Polym. Sci. Part A: Polym. Chem.

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“…The effective core potential double-ζ basis set (LANL2DZ) [6] was used for Zr atom, while a double-ζ basis set (6–31G(d)) for all non-metal atoms (C, H, O, F, Si, and Ge). This DFT/mixed basis set method has been shown to reproduce the X-ray structure [7] and has been widely applied in the field of transition metal complexes [7] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] . Frequency calculations were performed on all optimized structures to confirm the nature of stationary points as minima or transition states.…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

Data on electronic structures for the study of ligand effects on the zirconocene-mediated trimethylene carbonate polymerization

Jitonnom

Meelua

2018

Data in Brief

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The data presented in this paper are related to the research article entitled “Effect of ligand structure in the trimethylene carbonate polymerization by cationic zirconocene catalysts: A “naked model” DFT study” (Jitonnom and Meelua, 2017) [1]. In this data article, we present 3D molecular information of 29 zirconocene catalysts that differ in electronic and steric properties. The data contains all cationic species along the initiation and first propagation step of the polymerization, which are provided in a PDB format that can be used for further studies.

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“…Many of them opt for a base-free Cp 2 ZrMe + (or analogous L 2 ZrMe + ; Cp= cyclopentadienyl) cations, [5] whereas others take into account the insertion of the second monomer unit, [4a, 6] or the influence of chain-termination reactions. [7] The complexity of the polymerisation systems, including components such as the organometallic compound, co-catalyst, monomer and solvent, present in these kinds of catalytic processes means that theoretical studies are not straightforward.…”

Section: Introductionmentioning

confidence: 99%

Toward the Prediction of Activity in the Ethylene Polymerisation of ansa‐Bis(indenyl) Zirconocenes: Effect of the Stereochemistry and Hydrogenation of the Indenyl Moiety

et al. 2015

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A combined experimental and quantum chemical study has been performed on rac‐ and meso‐[Zr{1‐Me2Si(3‐η5‐C9H5Et)2}Cl2] (rac‐ and meso‐1) and their hydrogenated forms (rac‐ and meso‐2) to understand ligand effects and guide ligand design for more active ansa‐bis(indenyl) zirconocenes for the polymerisation of ethylene. The rac‐ansa‐zirconocene rac‐[Zr(1‐Me2Si{3‐Et‐(η5‐C9H9)}2)Cl2] (rac‐2) has been prepared and fully characterised by NMR spectroscopy and elemental analysis. The molecular structure of rac‐2 has also been determined by single‐crystal XRD. The behaviour of the catalysts was analysed in the polymerisation of ethylene and higher activities were obtained for rac‐1 and its hydrogenated form rac‐2. The influence of the stereochemistry and hydrogenation of the indenyl ligand on the experimental activities has been evaluated by computational studies. The differences along the reaction pathway are dominated by changes in the relative stabilities of the catalytic intermediates. A hybrid density functional B3LYP study, in the presence of toluene as the solvent, indicates that the rac forms give rise to more active species than their meso counterparts. The hydrogenation of the rac forms is a very promising approach to increase activities in polymerisation, in contrast to the meso forms. Finally, the global mechanism rate constants for the polymerisation reaction for each metallocene were calculated by using the thermodynamic formulation of transition‐state theory to complement the computational study.

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The influence of the ligand structure on activation of hafnocene polymerization catalysts: A theoretical study

Cited by 13 publications

References 42 publications

DFT mechanistic study of the H₂-assisted chain transfer copolymerization of propylene andp-methylstyrene catalyzed by zirconocene complex

DFT mechanistic study of the H₂-assisted chain transfer copolymerization of propylene andp-methylstyrene catalyzed by zirconocene complex

Data on electronic structures for the study of ligand effects on the zirconocene-mediated trimethylene carbonate polymerization

Toward the Prediction of Activity in the Ethylene Polymerisation of ansa‐Bis(indenyl) Zirconocenes: Effect of the Stereochemistry and Hydrogenation of the Indenyl Moiety

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The influence of the ligand structure on activation of hafnocene polymerization catalysts: A theoretical study

Cited by 13 publications

References 42 publications

DFT mechanistic study of the H2-assisted chain transfer copolymerization of propylene andp-methylstyrene catalyzed by zirconocene complex

DFT mechanistic study of the H2-assisted chain transfer copolymerization of propylene andp-methylstyrene catalyzed by zirconocene complex

Data on electronic structures for the study of ligand effects on the zirconocene-mediated trimethylene carbonate polymerization

Toward the Prediction of Activity in the Ethylene Polymerisation of ansa‐Bis(indenyl) Zirconocenes: Effect of the Stereochemistry and Hydrogenation of the Indenyl Moiety

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DFT mechanistic study of the H₂-assisted chain transfer copolymerization of propylene andp-methylstyrene catalyzed by zirconocene complex

DFT mechanistic study of the H₂-assisted chain transfer copolymerization of propylene andp-methylstyrene catalyzed by zirconocene complex