The Metallocene/Methylaluminoxane Catalysts Formation: EPR Spin Probe Study of Lewis Acidic Sites of Methylaluminoxane Научная публикация
| Журнал |
Journal of Molecular Catalysis A: Chemical
ISSN: 1381-1169 |
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| Вых. Данные | Год: 1999, Том: 139, Номер: 2-3, Страницы: 131-137 Страниц : 7 DOI: 10.1016/S1381-1169(98)00194-0 | ||||
| Ключевые слова | EPR, Lewis acidity, Metallocene catalysts, Methylaluminoxane, Spin probe | ||||
| Авторы |
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| Организации |
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Информация о финансировании (1)
| 1 | Российский фонд фундаментальных исследований | 97-03-32546 |
Реферат:
Using stable nitroxyl radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) as a spin probe, Lewis acidic sites of methylaluminoxane (MAO) were identified. It was found that MAO contains two types of acidic sites. TEMPO, coordinated to the sites I and II, exhibits in the EPR spectra triplet (go=2.0047, aN=18.6 G) and triplet of sextets (go=2.0045, aN=19.6 G and aAl=1.7 G), respectively (aN and aAl are constants of hyperfine structure from the corresponding nucleus). According to EPR measurements, concentration of sites I is close to that of sites II, and MAO contains one site of each type per 100±30 aluminium atoms. The adducts of TEMPO with sites I are less stable than those with sites II. Based on the values of aAl and relative stabilities of the adducts with TEMPO, the acidic sites I and II were attributed to coordinatively unsaturated aluminium atoms in AlOMe2 and AlO2Me environment, respectively. From the EPR spectra of coordinated TEMPO, the average radius of MAO oligomers (AlOMe)n was evaluated to be 5.8 Å at 20°C, which corresponds to the value of n=15–20. Thus, the major part of MAO contains not more than one Lewis acidic site per one oligomeric (AlOMe)n molecule.
Библиографическая ссылка:
Talsi E.P.
, Semikolenova N.V.
, Panchenko V.N.
, Sobolev A.P.
, Babushkin D.E.
, Shubin A.A.
, Zakharov V.A.
The Metallocene/Methylaluminoxane Catalysts Formation: EPR Spin Probe Study of Lewis Acidic Sites of Methylaluminoxane
Journal of Molecular Catalysis A: Chemical. 1999. V.139. N2-3. P.131-137. DOI: 10.1016/S1381-1169(98)00194-0 WOS Scopus РИНЦ CAPlusCA OpenAlex
The Metallocene/Methylaluminoxane Catalysts Formation: EPR Spin Probe Study of Lewis Acidic Sites of Methylaluminoxane
Journal of Molecular Catalysis A: Chemical. 1999. V.139. N2-3. P.131-137. DOI: 10.1016/S1381-1169(98)00194-0 WOS Scopus РИНЦ CAPlusCA OpenAlex
Даты:
| Поступила в редакцию: | 26 янв. 1998 г. |
| Принята к публикации: | 18 мая 1998 г. |
| Опубликована online: | 26 янв. 1999 г. |
| Опубликована в печати: | 5 мар. 1999 г. |
Идентификаторы БД:
| Web of science: | WOS:000078361700003 |
| Scopus: | 2-s2.0-0033525378 |
| РИНЦ: | 13315771 |
| Chemical Abstracts: | 1999:45709 |
| Chemical Abstracts (print): | 130:223628 |
| OpenAlex: | W2065997654 |