A DFT Quantum-Chemical Study of Ion-Pair Formation for the Catalyst Cp2ZrMe2/MAO Full article
| Journal |
Macromolecular Theory and Simulations
ISSN: 1022-1344 , E-ISSN: 1521-3919 |
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| Output data | Year: 2002, Volume: 11, Number: 3, Pages: 352-358 Pages count : 7 DOI: 10.1002/1521-3919(20020301)11:3<352::AID-MATS352>3.0.CO;2-2 | ||
| Tags | Calculations, Density functional theory (DFT), Ion pair, Metallocene catalysts, Methylaluminoxane, Polyolefins | ||
| Authors |
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| Affiliations |
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Funding (2)
| 1 | Russian Foundation for Basic Research | 00-15-97441 |
| 2 | International Association for the Promotion of Co-operation with Scientists from the New Independent States of the Former Soviet Union | 00-00841 |
Abstract:
A process of ion-pair formation in the system Cp2ZrMe2/methylaluminoxane (MAO) has been studied by means of density functional theory quantum-chemical calculations for MAOs with different structures and reactive sites. An interaction of Cp2ZrMe2 with a MAO of the composition (AlMeO)6 results in the formation of a stable molecular complex of the type Al5Me6O5Al(Me)O–Zr(Me)Cp2 with an equilibrium distance r(Zr–O) of 2.15 Å. The interaction of Cp2ZrMe2 with “true” MAO of the composition (Al8Me12O6) proceeds with a tri-coordinated aluminum atom in the active site (OAlMe2) and yields the strongly polarized molecular complex or the μ-Me-bridged contact ion pair (d) [Cp2(Me)Zr(μMe)Al≡MAO] with the distances r(Zr–μMe) = 2.38 Å and r(Al–μMe) = 2.28 Å. The following interaction of the μ-Me contact ion pair (d) with AlMe3 results in a formation of the trimethylaluminum (TMA)-separated ion pair (e) [Cp2Zr(μMe)2AlMe2]+–[MeMAO]– with r[Zr–(MeMAO)] equal to 4.58 Å. The calculated composition and structure of ion pairs (d) and (e) are consistent with the 13C NMR data for the species detected in the Cp2ZrMe2/MAO system. An interaction of the TMA-separated ion pair (e) with ethylene results in the substitution of AlMe3 by C2H4 in a cationic part of the ion pair (e), and the following ethylene insertion into the Zr–Me bond. This reaction leads to formation of ion pair (f) of the composition [Cp2ZrCH2CH2CH3]+–[Me-MAO]– named as the propyl-separated ion pair. Ion pair (f) exhibits distance r[Zr–(MeMAO)] = 3.88 Å and strong Cγ-agostic interaction of the propyl group with the Zr atom. We suppose this propyl-separated ion pair (f) to be an active center for olefin polymerization.
Cite:
Zakharov I.I.
, Zakharov V.A.
A DFT Quantum-Chemical Study of Ion-Pair Formation for the Catalyst Cp2ZrMe2/MAO
Macromolecular Theory and Simulations. 2002. V.11. N3. P.352-358. DOI: 10.1002/1521-3919(20020301)11:3<352::AID-MATS352>3.0.CO;2-2 WOS Scopus РИНЦ ANCAN OpenAlex
A DFT Quantum-Chemical Study of Ion-Pair Formation for the Catalyst Cp2ZrMe2/MAO
Macromolecular Theory and Simulations. 2002. V.11. N3. P.352-358. DOI: 10.1002/1521-3919(20020301)11:3<352::AID-MATS352>3.0.CO;2-2 WOS Scopus РИНЦ ANCAN OpenAlex
Dates:
| Submitted: | Sep 17, 2001 |
| Accepted: | Jan 21, 2002 |
| Published print: | Mar 1, 2002 |
| Published online: | Mar 28, 2002 |
Identifiers:
| Web of science: | WOS:000174973000010 |
| Scopus: | 2-s2.0-0037187810 |
| Elibrary: | 13394570 |
| Chemical Abstracts: | 2002:298745 |
| Chemical Abstracts (print): | 137:79281 |
| OpenAlex: | W2081486191 |