Upon examination of the reaction of l, 12-dimethyil.lferrocenophane with the strong non-oxidizing acid boron trifluoride, a dication was formed. Upon dilution widi H2O, a bridge carbocation results. A mixture of exo-exo l, 12-dimethyll.lferro-cenophane and exo-endo l, 12-dimethyll.lferrocenophane should be observed, if the hydride is added direcdy back to the methylene bridge carbocation. However, when the hydride is added, retention of configuration is realized, indicating a significandy more complex mechanism of reaction. We propose that the iron centers and the methylene bridge participate through an intramolecular hydride migration which leads to retention of configuration.
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