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

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 Full article

Journal

Molecular Catalysis
ISSN: 2468-8231

Output data

Year: 2019, Volume: 469, Pages: 57-67 Pages count : 11 DOI: 10.1016/j.mcat.2019.02.024

Tags

Catalytic activity; FI catalysts; Ethylene polymerization; Conceptual density functional theory; Degeneracy in frontier molecular orbitals; Local hyper-softness; Substituent effect; Hammett constant

Authors

Nikitin Sergey, V ^1,2 , Sanchez-Marquez Jesus ³ , Oleynik Ivan I. ^1,2 , Oleynik Irina ^1,2 , Bagryanskaya Elena G. ^1,2

Affiliations

1	(Данные Web of science) NN Vorozhtsov Novosibirsk Inst Organ Chem SB RAS, 9 Lavrentieva Ave, Novosibirsk 630090, Russia
2	(Данные Web of science) Novosibirsk State Univ, 2 Pirogova St, Novosibirsk 630090, Russia
3	(Данные Web of science) Univ Cadiz, Fac Ciencias, Dept Quim Fis, Campus Univ Rio San Pedro, Cadiz 11510, Spain

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.

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

Published print:

May 1, 2019

Web of science	WOS:000466253900007
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