Mechanism of Dimethylzirconocene Activation with Methylaluminoxane: NMR Monitoring of Intermediates at High Al/Zr Ratios Full article
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Macromolecular Chemistry and Physics
ISSN: 1022-1352 , E-ISSN: 1521-3935 |
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| Output data | Year: 2000, Volume: 201, Number: 5, Pages: 558-567 Pages count : 10 DOI: 10.1002/(SICI)1521-3935(20000301)201:5<558::AID-MACP558>3.0.CO;2-N | ||
| Tags | OLEFIN POLYMERIZATION; CATALYSTS; COMPLEXES; EQUILIBRIA | ||
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| Affiliations |
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Funding (1)
| 1 | Russian Foundation for Basic Research | 97-03-32546 |
Abstract:
Using 1H and 13C NMR spectroscopy, the interaction between Cp2ZrMe2 and MAO in toluene solution was investigated in a wide range of Al/Zr ratios (10–4 000). Several intermediates (I–IV) were detected in the reaction. The structures of these intermediates were elucidated from detailed analysis of 13C-1H NMR data. Intermediate I is a weak complex of Cp2ZrMe2 with MAO. Intermediate II is the complex contact ion-pair [Cp2ZrMe(μ-Me)Cp2ZrMe]+[Me-MAO]– with symmetric binuclear cationic part. Species III a and III b are the heterodinuclear complex [Cp2Zr(μ-Me)2AlMe2]+[Me-MAO]– contact ion-pairs and the similar separated ion-pairs. Species IV are represented by the unsymmetrically Me-bridged complex Cp2(Me)Zr+ ← Me–-Al ≡ (MAO). Reaction equilibria involving intermediates I–IV were studied with varying Al/Zr ratio, MAO concentration and Al2Me6 content. With increasing Al/Zr ratio, complexes I, II, and free Cp2ZrMe2 gradually disappear and at high Al/Zr ratios at conditions, close to the usual polymerization conditions, only species III and IV were detected. At high Al/Zr ratios the molar ratio IV/III appears to be 1–4 depending on the Al2Me6 content, whereas at low Al/Zr (10–40) it is much greater and III is present only in very small amounts. These observations are rationalized assuming a gradual decrease of the average dissociation tendency of IV as the diverse Lewis acidic sites of MAO become occupied. A possible scheme of Cp2ZrMe2 interaction with MAO is suggested. Data on the interaction between Cp2ZrCl2 and MAO are given for comparison.
Cite:
Babushkin D.E.
, Semikolenova N.V.
, Zakharov V.A.
, Talsi E.P.
Mechanism of Dimethylzirconocene Activation with Methylaluminoxane: NMR Monitoring of Intermediates at High Al/Zr Ratios
Macromolecular Chemistry and Physics. 2000. V.201. N5. P.558-567. DOI: 10.1002/(SICI)1521-3935(20000301)201:5<558::AID-MACP558>3.0.CO;2-N WOS Scopus РИНЦ ANCAN OpenAlex
Mechanism of Dimethylzirconocene Activation with Methylaluminoxane: NMR Monitoring of Intermediates at High Al/Zr Ratios
Macromolecular Chemistry and Physics. 2000. V.201. N5. P.558-567. DOI: 10.1002/(SICI)1521-3935(20000301)201:5<558::AID-MACP558>3.0.CO;2-N WOS Scopus РИНЦ ANCAN OpenAlex
Dates:
| Submitted: | Apr 1, 1999 |
| Accepted: | Jun 25, 1999 |
| Published print: | Mar 1, 2000 |
| Published online: | Mar 14, 2000 |
Identifiers:
| Web of science: | WOS:000086217700011 |
| Scopus: | 2-s2.0-0000105871 |
| Elibrary: | 13343082 |
| Chemical Abstracts: | 2000:241870 |
| Chemical Abstracts (print): | 133:17862 |
| OpenAlex: | W2070072788 |