Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups

Half-titanocenes are well known to show high activity for ethylene polymerization and good capability for copolymerization of ethylene with other olefins, and the ancillary ligands can crucially affect the catalytic performance. In this paper, the mechanisms of ethylene polymerization catalyzed by t...

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Autores principales:	Yang Li, Xiaoling Lai, Xiaowei Xu, Yat-Ming So, Yijing Du, Zhengze Zhang, Yu Pan
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	ethylene polymerization DFT half-titanocene reaction mechanism Chemical technology TP1-1185 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/3b67e17cfd284e26b4056b70b8af021a
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spelling	oai:doaj.org-article:3b67e17cfd284e26b4056b70b8af021a2021-11-25T17:06:42ZTheoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups10.3390/catal111113922073-4344https://doaj.org/article/3b67e17cfd284e26b4056b70b8af021a2021-11-01T00:00:00Zhttps://www.mdpi.com/2073-4344/11/11/1392https://doaj.org/toc/2073-4344Half-titanocenes are well known to show high activity for ethylene polymerization and good capability for copolymerization of ethylene with other olefins, and the ancillary ligands can crucially affect the catalytic performance. In this paper, the mechanisms of ethylene polymerization catalyzed by three half-metallocenes, (<i>η</i><sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)TiCl<sub>2</sub>(O-2,6-<i><sup>i</sup></i>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) (<b>1</b>), (<i>η</i><sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)TiCl<sub>2</sub>(N=C<i><sup>t</sup></i>Bu<sub>2</sub>) (<b>2</b>) and [Me<sub>2</sub>Si(<i>η</i><sup>5</sup>-C<sub>5</sub>Me<sub>4</sub>)(N<i><sup>t</sup></i>Bu)]TiCl<sub>2</sub> (<b>3</b>), have been investigated by density functional theory (DFT) method. At the initiation stage, a higher free energy barrier was determined for complex <b>1</b>, probably due to the presence of electronegative O atom in phenoxy ligand. At the propagation stage, front-side insertion of the second ethylene is kinetically more favorable than back-side insertion for complexes <b>1</b> and <b>2</b>, while both side insertion orientations are comparable for complex <b>3</b>. The energy decomposition showed that the bridged cyclopentadienyl amide ligand could enhance the rigidity of the active species as suggested by the lowest deformation energy derived from <b>3</b>. At the chain termination stage, <i>β-</i>H transfer was calculated to be a dominant chain termination route over <i>β</i>-H elimination, presumably owing to the thermodynamic perspective.Yang LiXiaoling LaiXiaowei XuYat-Ming SoYijing DuZhengze ZhangYu PanMDPI AGarticleethylene polymerizationDFThalf-titanocenereaction mechanismChemical technologyTP1-1185ChemistryQD1-999ENCatalysts, Vol 11, Iss 1392, p 1392 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	ethylene polymerization DFT half-titanocene reaction mechanism Chemical technology TP1-1185 Chemistry QD1-999
spellingShingle	ethylene polymerization DFT half-titanocene reaction mechanism Chemical technology TP1-1185 Chemistry QD1-999 Yang Li Xiaoling Lai Xiaowei Xu Yat-Ming So Yijing Du Zhengze Zhang Yu Pan Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups
description	Half-titanocenes are well known to show high activity for ethylene polymerization and good capability for copolymerization of ethylene with other olefins, and the ancillary ligands can crucially affect the catalytic performance. In this paper, the mechanisms of ethylene polymerization catalyzed by three half-metallocenes, (<i>η</i><sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)TiCl<sub>2</sub>(O-2,6-<i><sup>i</sup></i>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) (<b>1</b>), (<i>η</i><sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)TiCl<sub>2</sub>(N=C<i><sup>t</sup></i>Bu<sub>2</sub>) (<b>2</b>) and [Me<sub>2</sub>Si(<i>η</i><sup>5</sup>-C<sub>5</sub>Me<sub>4</sub>)(N<i><sup>t</sup></i>Bu)]TiCl<sub>2</sub> (<b>3</b>), have been investigated by density functional theory (DFT) method. At the initiation stage, a higher free energy barrier was determined for complex <b>1</b>, probably due to the presence of electronegative O atom in phenoxy ligand. At the propagation stage, front-side insertion of the second ethylene is kinetically more favorable than back-side insertion for complexes <b>1</b> and <b>2</b>, while both side insertion orientations are comparable for complex <b>3</b>. The energy decomposition showed that the bridged cyclopentadienyl amide ligand could enhance the rigidity of the active species as suggested by the lowest deformation energy derived from <b>3</b>. At the chain termination stage, <i>β-</i>H transfer was calculated to be a dominant chain termination route over <i>β</i>-H elimination, presumably owing to the thermodynamic perspective.
format	article
author	Yang Li Xiaoling Lai Xiaowei Xu Yat-Ming So Yijing Du Zhengze Zhang Yu Pan
author_facet	Yang Li Xiaoling Lai Xiaowei Xu Yat-Ming So Yijing Du Zhengze Zhang Yu Pan
author_sort	Yang Li
title	Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups
title_short	Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups
title_full	Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups
title_fullStr	Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups
title_full_unstemmed	Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups
title_sort	theoretical study on ethylene polymerization catalyzed by half-titanocenes bearing different ancillary groups
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/3b67e17cfd284e26b4056b70b8af021a
work_keys_str_mv	AT yangli theoreticalstudyonethylenepolymerizationcatalyzedbyhalftitanocenesbearingdifferentancillarygroups AT xiaolinglai theoreticalstudyonethylenepolymerizationcatalyzedbyhalftitanocenesbearingdifferentancillarygroups AT xiaoweixu theoreticalstudyonethylenepolymerizationcatalyzedbyhalftitanocenesbearingdifferentancillarygroups AT yatmingso theoreticalstudyonethylenepolymerizationcatalyzedbyhalftitanocenesbearingdifferentancillarygroups AT yijingdu theoreticalstudyonethylenepolymerizationcatalyzedbyhalftitanocenesbearingdifferentancillarygroups AT zhengzezhang theoreticalstudyonethylenepolymerizationcatalyzedbyhalftitanocenesbearingdifferentancillarygroups AT yupan theoreticalstudyonethylenepolymerizationcatalyzedbyhalftitanocenesbearingdifferentancillarygroups
_version_	1718412707827286016

Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups

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