Insight into group 4 metallocenium-mediated olefin polymerization reaction coordinates using a metadynamics approach

Alessandro Motta, Ignazio L. Fragalà, Tobin J Marks

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

We report here the first application of the computationally efficient metadynamics approach for analyzing single-site olefin polymerization mechanisms. The mechanism of group 4 metallocenium catalysis for ethylene homopolymerization is investigated by modeling the ethylene insertion step at the cationic (η5-C5H5)Zr(CH 3)2+ center using molecular dynamics simulations within the Density Functional Theory (DFT) framework. In particular, the metadynamics formalism is adopted to enable theoretical characterization of covalent bond forming/breaking processes using molecular dynamics ab initio tools. Analysis of the ethylene insertion step free energy surface indicates a slightly exoergic process (-3.2 kcal/mol) with a barrier of 8.6 kcal/mol, in good agreement with conventional ab initio static calculations. Analysis of the structural and dynamic aspects of the simulated reaction coordinate reveals a preferred olefin configuration which aligns parallel to the Zr-CH3 vector in concert with insertion and a slightly bent conformation of the product n-propyl chain to avoid nonbonded repulsion between methylene groups. It is found that the unsaturated/electrophilic CpZr(CH3)2 + center drives the insertion step, thus promoting the formation of the Zr-alkyl bond. The metadynamics analysis uniquely encompasses all energetically possible reaction coordinates, thus providing a more detailed mechanistic picture. These results demonstrate the potential of metadynamics in the conformational and geometrical analysis of transition metal-centered homogeneous catalytic processes.

Original languageEnglish
Pages (from-to)3491-3497
Number of pages7
JournalJournal of Chemical Theory and Computation
Volume9
Issue number8
DOIs
Publication statusPublished - Aug 13 2013

Fingerprint

Alkenes
alkenes
Olefins
insertion
Ethylene
polymerization
Polymerization
ethylene
Molecular dynamics
Covalent bonds
molecular dynamics
Homopolymerization
Catalysis
Free energy
Transition metals
Density functional theory
Conformations
covalent bonds
methylene
catalysis

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Computer Science Applications

Cite this

Insight into group 4 metallocenium-mediated olefin polymerization reaction coordinates using a metadynamics approach. / Motta, Alessandro; Fragalà, Ignazio L.; Marks, Tobin J.

In: Journal of Chemical Theory and Computation, Vol. 9, No. 8, 13.08.2013, p. 3491-3497.

Research output: Contribution to journalArticle

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