Fluorine for Hydrogen Exchange in the Hydrofluorobenzene Derivatives C6HxF(6-x), where x = 2, 3, 4 and 5 by Monomeric [1,2,4-(Me3C)3C5H2]2CeH: The Solid State Isomerization of [1,2,4-(Me3C)3C5H2]2Ce(2,3,4,5-C6HF4) to [1,2,4-(Me3C)3C5H2]2Ce(2,3,4,6-C6HF4)
| Autor: | Evan L. Werkema, Richard A. Andersen |
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| Rok vydání: | 2008 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 130:7153-7165 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The reaction between monomeric bis(1,2,4-tri-tert-butylcyclopentadienyl)cerium hydride, Cp′2CeH, and several hydrofluorobenzene derivatives is described. The aryl derivatives that are the primary products, Cp′2Ce(C6H5-xFx) where x = 1,2,3,4, are thermally stable enough to be isolated in only two cases, since all of them decompose at different rates to Cp′2CeF and a fluorobenzyne; the latter is trapped by either solvent when C6D6 is used or by a Cp′H ring when C6D12 is the solvent. The trapped products are identified by GC/MS analysis after hydrolysis. The aryl derivatives are generated cleanly by reaction of the metallacycle, Cp′((Me3C)2C5H2C(Me2)CH2)Ce, with a hydrofluorobenzene, and the resulting arylcerium products, in each case, are identified by their 1H and 19F NMR spectra at 20 °C. The stereochemical principle that evolves from these studies is that the thermodynamic isomer is the one in which the CeC bond is flanked by two ortho-CF bonds. This orientation is suggested to arise from the negative ch... |
| Databáze: | OpenAIRE |
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