Synthesis and conversions of metallocycles. 22. NMR studies of the mechanism of Cp2ZrCl2-catalyzed cycloalumination of olefins with triethylaluminum to form aluminacyclopentanes |
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| Authors: | Khalilov L. M. Parfenova L. V. Rusakov S. V. Ibragimov A. G. Dzhemilev U. M. |
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| Affiliation: | (1) Institute of Petrochemistry and Catalysis, Bashkortostan Republic Academy of Sciences, Russian Federation;(2) Ufa Research Center, Russian Academy of Sciences, 141 prosp. Oktyabrya, 450075 Ufa, Russian Federation |
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| Abstract: | The mechanism of cycloalumination of olefins under the action of AlEt3 in the presence of Cp2ZrCl2 giving rise to aluminacyclopentanes was investigated by dynamic 1H and 13C NMR spectroscopy. The bimetallic complex Cp2ZrEtCl–AlEt3 is formed initially and is converted into the bridged complex Cp2Zr(Cl)CH2CH2AlEt2 as a result of beta-hydride shift and elimination of the ethane molecule. The resulting complex adds a molecule of the initial olefin yielding aluminacyclopentanes. Under the action of Et2AlCl in the presence of an excess of AlEt3, zirconacyclopentanes give rise to intermediate bimetallic complexes stable at -70 °C. Under the reaction conditions, the latter compounds are converted into aluminacyclopentanes. |
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| Keywords: | reaction mechanism metal-complex catalysis cyclometallation aluminacyclopentanes dynamic NMR spectroscopy |
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