EFFECT OF LIGAND STRUCTURAL CHANGES ON REVERSIBLE REDUCTION OF ARENE-IRONCYCLOPENTADIENYL CATIONS

The polarographic reduction of the arene-ironcyclopentadienyl compounds (arene = benzene, naphthalene, fluorene, diphenyl, phenanthrene) was investigated on the dropping mercury electrode. The first step of the reduction was found to involve a one-electron reversible reduction resulting in an uncharged formally univalent iron complex. The cyclohexadienyl complex is believed to be a reduction product of the second step. A study of the structural changes of the ligand shows that the effects of substituents in the π-C5H5 and π-C6H6 rings on the reaction center-iron atom-are of the same nature and magnitude. Exact correlations between E 1 2 and σ0p constants indicate that of the total polar effect of a substituent in the aromatic ring the inductive component alone is effectively transferred by a substituted aromatic ring in the direction of the metal atom. © 1969.