Hydrogen sensitivity – A systematic computational study of electronic effects

Budzelaar, Peter H. M.; Coussens, Betty; Friederichs, Nic

doi:10.1016/j.jorganchem.2007.04.030

Cited by 6 publications

(2 citation statements)

References 35 publications

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“…Termination barriers, as a function of metal and monomer, are illustrated in Figure . As expected, the barriers are low, about 10 kJ/mol, which is in accordance with experiments and with previous calculations of molecular hydrogen being efficient in terminating the chain growth. Notwithstanding the small barriers, there is a systematic difference between the metals, the barriers being higher for the zirconocene.…”

Section: Resultssupporting

confidence: 92%

Comparative Theoretical Study on Homopolymerization of α-Olefins by Bis(cyclopentadienyl) Zirconocene and Hafnocene: Elemental Propagation and Termination Reactions between Monomers and Metals

et al. 2010

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A comparative quantum chemical study has been performed to shed light on the fundamental differences between hafnocenes and zirconocenes concerning reactions between the metals and R-olefin monomers, namely, ethene, propene, 1-butene, and 1-hexene. Analogous species along the R-olefin polymerization pathways were studied for bis(cyclopentadienyl) zirconocene and hafnocene, taking into account the structural variations of the first two monomer insertion steps and of the competitive chain-termination reactions. The results were analyzed as a function of both the metal and the monomer, the metal showing more distinct differences. The most notable difference in the reactions of the zirconocene and hafnocene can be seen in β-hydrogen transfer to metal, activation energies for which are significantly higher for the hafnocene.

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Section: Resultssupporting

confidence: 92%

Comparative Theoretical Study on Homopolymerization of α-Olefins by Bis(cyclopentadienyl) Zirconocene and Hafnocene: Elemental Propagation and Termination Reactions between Monomers and Metals

et al. 2010

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“…Finally, in a comparative study between different polyolefin catalysts (models for heterogeneous systems but also metallocenes), researchers from DSM and SABIC discuss hydrogen sensitivity, which is the reactivity ratio between metal alkyl hydrogenolysis and the normal olefin insertion propagation, see again Scheme . From the calculations, it is concluded that there is a correlation between this property and complexation of the model donor ammonia, that is, the more exothermic the reaction with ammonia (due to higher electrophilicity of metal centers), the lower the hydrogen sensitivity of a catalyst.…”

Section: Chemical Reactivity and Catalysismentioning

confidence: 99%

Application of quantum calculations in the chemical industry—An overview

Deglmann¹,

Schäfer²,

Lennartz³

2014

Int J of Quantum Chemistry

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The field of quantum chemistry experienced huge progress in the past two decades. The drivers for this have been the availability of more and more powerful computer hardware, the development and implementation of improved methods with a better balanced compromise between accuracy and efficiency, as well as pioneering work how these methods are successfully applied to real-world problems. Thus, quantum calculations, in particular via density functional theory, became an essential tool in many branches of chemical research. This article tries to give an overview how quantum chemical modeling is used in chemical industry, which is done by reviewing papers written by authors from chemical companies. Various topics of particular industrial relevance are introduced together with strategies how to address them via quantum calculations. Examples are the computation of reaction thermodynamics and kinetics as the key ingredients to understand and predict chemical reactivity, but also solvation models as well as methods to describe electronically excited states.

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Mechanisms of branch formation in metal‐catalyzed ethene polymerization

Budzelaar

2011

WIREs Comput Mol Sci

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Branches are an important aspect of the structure of real polyethylene. Branches can be short (Me, Et) or longer; long-chain branches (LCB, >100 carbons), in particular, are important because they can have a dramatic effect on polymer properties. In this review, we summarize mechanistic information from organometallic and computational chemistry and use this to examine the most probable sources of each type of branch. Short branches can be introduced deliberately by copolymerization with an α-olefin (possibly formed in situ from ethene). Me branches may be formed by one-carbon chain walking and propagation, and/or from insertion of an oligomer/macromer in an M Me bond formed via chain transfer to the cocatalyst [Me3Al or methylaluminoxane (MAO)]. Et branches are most likely formed through β-hydrogen transfer to ethene, followed immediately by\ud reinsertion of the newly formed macromer. LCBs have usually been ascribed to reinsertion of macromers. However, certain catalysts exhibit LCB formation patterns that are hard to reconcile with this model, and a ‘two-monomer’ model was recently proposed to explain the observations for these systems. In this review, we present an alternative explanation (chain walking) that would fit the same facts for these catalysts

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Hydrogen sensitivity – A systematic computational study of electronic effects

Cited by 6 publications

References 35 publications

Comparative Theoretical Study on Homopolymerization of α-Olefins by Bis(cyclopentadienyl) Zirconocene and Hafnocene: Elemental Propagation and Termination Reactions between Monomers and Metals

Comparative Theoretical Study on Homopolymerization of α-Olefins by Bis(cyclopentadienyl) Zirconocene and Hafnocene: Elemental Propagation and Termination Reactions between Monomers and Metals

Application of quantum calculations in the chemical industry—An overview

Mechanisms of branch formation in metal‐catalyzed ethene polymerization

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