On the problem of two-electron reduction of arenecyclopentadienyliron cations

Abstract

The naphthalene-cp-iron cation (cp  cyclopentadienyl) has been studied polarographically under strictly aprotic conditions to prove the existence of the two-electron reduction product, the anion [C 10H 8FeC 5H 5] −. The reduction of the biphenyl- and benzene-cp-iron cations with sodium amalgam in proton donor media (pentane/water) is shown to yield, together with the electroneutral arene π-complexes AreneFeC 5H 5, the corresponding iron cyclohexadienyl-cp derivatives, endo-1-C 6H 5C 6H 6FeC 5H 5 and C 6H 7FeC 5H 5. The suggestion is made that the latter are formed from the two-electron reduction products, [AreneFeC 5H 5] −, under the action of protons. The [AreneFeC 5H 5] − anions cannot be detected in the reduction of [AreneFeC 5H 5] + with sodium amalgam in aprotic media as these anions react with excess [AreneFeC 5H 5] + to give two molecules of AreneFeC 5H 5.