DIENYL COMPLEXES OF TRANSITION METALS .4. STEREOCHEMISTRY OF ADDITION OF METHYL-LITHIUM AND OTHER NUCLEOPHILES TO ARENECYCLOPENTADIENYLIROON CATIONS AND OF HYDRIDE ABSTRACTION FROM RESULTING CYCLOHEXADIENYL COMPLEXES

The addition of methanide to arenecyclopentadienyliron cations is shown to be subject in most cases to the same directive influences as for the hydride addition studied previously. However, hexamethylbenzenecyclopentadienyliron cation undergoes addition at the cyclopentadienyl ring giving a neutral complex, which was identified by conversion into hexamethylbenzenemethylcyclopentadienyliron cation, a rare example of enedo-hydride abstraction. Extensive spectroscopic correlations strengthen previous evidence of the highly stereospecific exo-direction of such addition reactions and of exo-hydride removal from the cyclohexadienyl products.