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Supported metallocene catalysts by surface organometallic chemistry. Synthesis, characterization, and reactivity in ethylene polymerization of oxide-supported mono- and biscyclopentadienyl zirconium alkyl complexes: establishment of structure/reactivity relationships

Supported metallocene catalysts by surface organometallic chemistry. Synthesis, characterization, and reactivity in ethylene polymerization of oxide-supported mono- and biscyclopentadienyl zirconium alkyl complexes: establishment of structure/reactivity relationships
Supported metallocene catalysts by surface organometallic chemistry. Synthesis, characterization, and reactivity in ethylene polymerization of oxide-supported mono- and biscyclopentadienyl zirconium alkyl complexes: establishment of structure/reactivity relationships
The reactions of Cp*Zr(CH3)(3), 1, and Cp2Zr(CH3)(2), 2, with partially dehydroxylated silica, silica-alumina, and alumina surfaces have been carried out with careful identification of the resulting surface organometallic complexes in order to probe the relationship between catalyst structure and polymerization activity. The characterization of the supported complexes has been achieved in most cases by in situ infrared spectroscopy, surface microanalysis, qualitative and quantitative analysis of evolved gases during surface reactions with labeled surface, solid state H-1 and C-13 NMR using C-13-enriched compounds, and EXAFS. 1 and 2 react with silica(500) and silica-alumina(500) by simple protonolysis of one Zr-Me bond by surface silanols with formation of a single well-defined neutral compound. In the case of silica-alumina, a fraction of the supported complexes exhibits some interactions with electronically unsaturated surface aluminum sites. 1 and 2 also react with the hydroxyl groups of gamma -alumina(500), leading to several surface structures. Correlation between EXAFS and 13C NMR data suggests, in short, two main surface structures having different environments for the methyl group: [Al](3)-OZrCp*(CH3)(2) and [Al](2)-OZrCp*(CH3)(mu -CH3)-[Al] for the monoCp series and [Al](2)-OZrCp2(CH3) and [Al]-OZrCp2(mu -CH3)-[Al] for the bisCp series. Ethylene polymerization has been carried out with all the supported complexes under various reaction conditions. Silica-supported catalysts in the absence of any cocatalyst exhibited no activity whatsoever for ethylene polymerization. When the oxide contained Lewis acidic sites, the resulting surface species were active. The activity, although improved by the presence of additional cocatalysts, remained very low by comparison with that of the homogeneous metallocene systems. This trend has been interpreted on the basis of various possible parameters, including the (p-pi)-(d-pi) back-donation of surface oxygen atoms to the zirconium center.
sio2-supported zirconocene catalysts, ziegler-natta catalysts, group-iv metallocene, olefin polymerization, propylene polymerizations, molecular-structure, elastomeric poly(propylene), pentamethylenespacers, alkene polymerization, arene complexes
0002-7863
3520-3540
Jezequel, Michelle
921d3987-5ee6-4f1a-9ec2-268810b48612
Dufaud, Véronique
cd43c507-3426-4a51-89e8-00e7575751c6
Ruiz-Garcia, Maria José
d909a477-c478-4c39-b630-19df769b2abe
Carrillo-Hermosilla, Fernando
a482323a-7220-42d2-a41b-83ca7d2b9a5d
Neugebauer, Ute
5ccd7866-cb10-4cf3-9a67-a90cb6acb2be
Niccolai, Gerald P.
4f15c129-5cef-480b-88c0-cb1224bbb3f7
Lefebvre, Frédéric
ab459241-b0e6-4b11-8dc6-03daa5454fc4
Bayard, François
b63f1021-5f0f-4f33-be60-c32f068e0d3b
Corker, Judith
238f65f3-bd3c-4da8-95a8-ec4fd6d0f832
Fiddy, Steven
4bd733e0-36d4-4d9f-8f2b-d1ccad3b867c
Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
Broyer, Jean-Pierre
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Malinge, Jean
15340737-d631-42e6-8aee-dd689cd804a6
Basset, Jean-Marie Basset
37defb96-4833-4d37-9d5f-947a9836df7f
Jezequel, Michelle
921d3987-5ee6-4f1a-9ec2-268810b48612
Dufaud, Véronique
cd43c507-3426-4a51-89e8-00e7575751c6
Ruiz-Garcia, Maria José
d909a477-c478-4c39-b630-19df769b2abe
Carrillo-Hermosilla, Fernando
a482323a-7220-42d2-a41b-83ca7d2b9a5d
Neugebauer, Ute
5ccd7866-cb10-4cf3-9a67-a90cb6acb2be
Niccolai, Gerald P.
4f15c129-5cef-480b-88c0-cb1224bbb3f7
Lefebvre, Frédéric
ab459241-b0e6-4b11-8dc6-03daa5454fc4
Bayard, François
b63f1021-5f0f-4f33-be60-c32f068e0d3b
Corker, Judith
238f65f3-bd3c-4da8-95a8-ec4fd6d0f832
Fiddy, Steven
4bd733e0-36d4-4d9f-8f2b-d1ccad3b867c
Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
Broyer, Jean-Pierre
961e7a55-7ebe-43de-a38c-d6dc84d1694f
Malinge, Jean
15340737-d631-42e6-8aee-dd689cd804a6
Basset, Jean-Marie Basset
37defb96-4833-4d37-9d5f-947a9836df7f

Jezequel, Michelle, Dufaud, Véronique, Ruiz-Garcia, Maria José, Carrillo-Hermosilla, Fernando, Neugebauer, Ute, Niccolai, Gerald P., Lefebvre, Frédéric, Bayard, François, Corker, Judith, Fiddy, Steven, Evans, John, Broyer, Jean-Pierre, Malinge, Jean and Basset, Jean-Marie Basset (2001) Supported metallocene catalysts by surface organometallic chemistry. Synthesis, characterization, and reactivity in ethylene polymerization of oxide-supported mono- and biscyclopentadienyl zirconium alkyl complexes: establishment of structure/reactivity relationships. Journal of the American Chemical Society, 123 (15), 3520-3540. (doi:10.1021/ja000682q).

Record type: Article

Abstract

The reactions of Cp*Zr(CH3)(3), 1, and Cp2Zr(CH3)(2), 2, with partially dehydroxylated silica, silica-alumina, and alumina surfaces have been carried out with careful identification of the resulting surface organometallic complexes in order to probe the relationship between catalyst structure and polymerization activity. The characterization of the supported complexes has been achieved in most cases by in situ infrared spectroscopy, surface microanalysis, qualitative and quantitative analysis of evolved gases during surface reactions with labeled surface, solid state H-1 and C-13 NMR using C-13-enriched compounds, and EXAFS. 1 and 2 react with silica(500) and silica-alumina(500) by simple protonolysis of one Zr-Me bond by surface silanols with formation of a single well-defined neutral compound. In the case of silica-alumina, a fraction of the supported complexes exhibits some interactions with electronically unsaturated surface aluminum sites. 1 and 2 also react with the hydroxyl groups of gamma -alumina(500), leading to several surface structures. Correlation between EXAFS and 13C NMR data suggests, in short, two main surface structures having different environments for the methyl group: [Al](3)-OZrCp*(CH3)(2) and [Al](2)-OZrCp*(CH3)(mu -CH3)-[Al] for the monoCp series and [Al](2)-OZrCp2(CH3) and [Al]-OZrCp2(mu -CH3)-[Al] for the bisCp series. Ethylene polymerization has been carried out with all the supported complexes under various reaction conditions. Silica-supported catalysts in the absence of any cocatalyst exhibited no activity whatsoever for ethylene polymerization. When the oxide contained Lewis acidic sites, the resulting surface species were active. The activity, although improved by the presence of additional cocatalysts, remained very low by comparison with that of the homogeneous metallocene systems. This trend has been interpreted on the basis of various possible parameters, including the (p-pi)-(d-pi) back-donation of surface oxygen atoms to the zirconium center.

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More information

Published date: 18 April 2001
Keywords: sio2-supported zirconocene catalysts, ziegler-natta catalysts, group-iv metallocene, olefin polymerization, propylene polymerizations, molecular-structure, elastomeric poly(propylene), pentamethylenespacers, alkene polymerization, arene complexes

Identifiers

Local EPrints ID: 19530
URI: http://eprints.soton.ac.uk/id/eprint/19530
ISSN: 0002-7863
PURE UUID: 45b5edea-abda-4f99-804f-359b15576395

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Date deposited: 15 Feb 2006
Last modified: 15 Jul 2019 19:27

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Contributors

Author: Michelle Jezequel
Author: Véronique Dufaud
Author: Maria José Ruiz-Garcia
Author: Fernando Carrillo-Hermosilla
Author: Ute Neugebauer
Author: Gerald P. Niccolai
Author: Frédéric Lefebvre
Author: François Bayard
Author: Judith Corker
Author: Steven Fiddy
Author: John Evans
Author: Jean-Pierre Broyer
Author: Jean Malinge
Author: Jean-Marie Basset Basset

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