| Abstract
| - Fluoride binding to ferrocene-based heteronuclear bidentate Lewis acids was found to lead to unsymmetric reverse chelates, where the fluoride is strongly bound to boron and more weakly to tin.
- A series of μ2-fluoro-bridged heteronuclear bidentate Lewis acid complexes [K(18-crown-6)THF]+ [Fc(BMeF)(SnMe2Cl)F]-(1-2F), [K(18-crown-6)THF]+ [Fc(BMeF)(SnMe2F)F]-(1-3F), [K(18-crown-6)THF]+ [Fc(BMePh)(SnMe2Cl)F]-(2-F),and [K(18-crown-6)THF]+ [Fc(BMePh)(SnMe2F)F]-(2-2F) (Fc = 1,2-ferrocenediyl) was prepared. Compounds 2-Fand 2-2F were obtained as a mixture of diastereomers, which arise due to the generation of a stereocenter atboron in addition to their inherent planar chirality. All compounds have been studied in the solid state by single-crystal X-ray diffraction analysis and by multinuclear NMR spectroscopy in solution. As a result of bridging-fluorideinteractions, tetrahedral boron and distorted trigonal-bipyramidal tin centers are observed. Comparison with thecorresponding monofunctional ferrocenylborates further supports the bridging nature of the fluoride anion. Two-dimensional exchange spectroscopy 19F NMR studies provide evidence for facile intermolecular and intramolecularfluorine exchange processes. All complexes display reversible one-electron oxidation events at lower potentialsthan those of the tricoordinate ferrocenylborane precursors, which is typical of ferrocenylborate complexes.
|
