Structural and Stereochemical Studies of Tris[2-(trifluoromethyl)phenyl]borane: Spontaneous Resolution, Stereodynamics, and Intramolecular C-F···B Interactions
| Autor: | Michinori Oki, Fumio Toda, Mitsuhiro Asakura, Shinji Toyota |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Bulletin of the Chemical Society of Japan. 73:2357-2362 |
| ISSN: | 1348-0634 0009-2673 |
| DOI: | 10.1246/bcsj.73.2357 |
| Popis: | The structure and stereochemistry of the title organoboron compound, prepared from the corresponding organolithium compound and BCl3, were studied by spectroscopic methods and molecular orbital calculations. The X-ray crystal structure analysis shows that molecules take a propeller-shaped structure of nearly C3 symmetry, in which three CF3 groups lie at the same side of the boron sp2 plane. This compound crystallizes as conglomerates to give single crystals consisting of one or the other enantiomeric forms, both of which are CD active in the solid state. In solutions, molecules exist as a mixture of two conformational isomers, the C3 and C1 symmetric forms. Interconversion between the two isomers was observed by the variable temperature 19F NMR, the barriers to isomerization being 8 and 6 kcal mol-1 for two independent processes in the two ring flip mechanism. The presence of C-F···B interactions was supported by the short F···B contacts (ca. 2.80 A) in the X-ray structure and by the chemical shift of 19F... |
| Databáze: | OpenAIRE |
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