A screening DFT study of the para-substituent effect on local hyper-softness in bis(phenoxy-imine) titanium complexes to get insights about their catalytic activity in ethylene polymerization Научная публикация
| Журнал |
Molecular Catalysis
ISSN: 2468-8231 |
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| Вых. Данные | Год: 2019, Том: 469, Страницы: 57-67 Страниц : 11 DOI: 10.1016/j.mcat.2019.02.024 | ||||||
| Ключевые слова | Catalytic activity; FI catalysts; Ethylene polymerization; Conceptual density functional theory; Degeneracy in frontier molecular orbitals; Local hyper-softness; Substituent effect; Hammett constant | ||||||
| Авторы |
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Реферат:
Quantum chemical calculations of substituted alpha-Cumyl and Bu-t bis(phenoxy-imine) titanium catalysts were performed at the RBP86/SVP level. The impact of para-substitution in the phenoxy-imine ligands on the electronic structure of the titanium complexes was studied within the framework of the Conceptual density functional theory. We found that such a reactivity descriptor as local hyper-softness on titanium correlates well with the Hammett constant for a series of substituents. The effect of the substitution in three para-positions of the phenoxy-imine ligand for the Cumyl catalysts weakens while passing from the alpha-Cumyl through the salicylic and further to the aniline moiety. By contrast, in the t Bu complexes the presence of a substituent in the salicylic part has similar influence on the local hyper-softness on titanium as compared with the aniline moiety. Moreover, placement of the groups with opposite electronic effects at the termini of the phenoxy-imine framework was shown to provide electronic flexibility in both the alpha-Cumyl and the Bu-t complexes. Within the framework of the "ligand-oriented" concept, such flexibility increases the activity of a bis(phenoxy-imine) catalyst. In addition, we demonstrated that the hyper-conjugation between the pi-system of the phenoxy-imine ligand and the alpha-Cumyl group raises the energy of the highest occupied molecular orbital keeping the lowest unoccupied orbital almost unchanged. This makes the alpha-Cumyl complexes chemically softer than their Bu-t analogs and thereby more active in ethylene polymerization.
Библиографическая ссылка:
Nikitin S.V.
, Sanchez-Marquez J.
, Oleynik I.I.
, Oleynik I.
, Bagryanskaya E.G.
A screening DFT study of the para-substituent effect on local hyper-softness in bis(phenoxy-imine) titanium complexes to get insights about their catalytic activity in ethylene polymerization
Molecular Catalysis. 2019. V.469. P.57-67. DOI: 10.1016/j.mcat.2019.02.024 WOS Scopus РИНЦ
A screening DFT study of the para-substituent effect on local hyper-softness in bis(phenoxy-imine) titanium complexes to get insights about their catalytic activity in ethylene polymerization
Molecular Catalysis. 2019. V.469. P.57-67. DOI: 10.1016/j.mcat.2019.02.024 WOS Scopus РИНЦ
Даты:
| Опубликована в печати: | 1 мая 2019 г. |
Идентификаторы:
| Web of science | WOS:000466253900007 |
| Scopus | 2-s2.0-85062641853 |
| РИНЦ | 41791189 |
| OpenAlex | W2921930821 |