DFT modeling of the post-titanocene catalytic system LTiCl2-Bu2Mg-Et2AlCl for alkene polymerization: The role of alkyl bridge Mg–C–Ti and β-agostic C–H–Ti bonds in the formation of active centers
| Autor: | Leila Yu. Ustynyuk |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
chemistry.chemical_classification
Agostic interaction Ethylene 010405 organic chemistry Alkene Stereochemistry Process Chemistry and Technology 010402 general chemistry 01 natural sciences Medicinal chemistry Catalysis 0104 chemical sciences Active center chemistry.chemical_compound chemistry Polymerization Physical and Theoretical Chemistry Isomerization Alkyl |
| Zdroj: | Journal of Molecular Catalysis A: Chemical. 426:600-609 |
| ISSN: | 1381-1169 |
| DOI: | 10.1016/j.molcata.2016.09.027 |
| Popis: | DFT modeling of the active centers formation in the catalytic system LTiCl2-Bu2Mg-Et2AlCl for alkene polymerization, where L is a bidentate ligand of saligenin type, suggests the three-step mechanism of this process. This mechanism includes the addition of the most probable alkylating agent, RMg(μ-Cl)2AlR2 or RMg(μ-Cl)2MgR (R = alkyl), to LTiCl2 with the formation of the trinuclear heterocomplex with the alkyl bridge bond Mg–C–Ti, followed by its two-step isomerization into the active center via the β-agostic intermediate. The free energy changes at the stages of the addition and isomerization are negative; the maximal energy barrier on the reaction pathway is small. In the Mg-free system LTiCl2-AlR3, the isomerization proceeds through the single energy barrier with a significantly higher amplitude. This could be the reason for a relatively high activity of the Mg-containing system and inactivity of the Mg-free system. |
| Databáze: | OpenAIRE |
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