6533b7d1fe1ef96bd125d619

RESEARCH PRODUCT

Preparative and spectroscopic features of ferricenium tetrachloroferrate(III). Interconversion to diferricenium ?-oxo-bis[trichloroferrate(III)]

subject

description

Ferricenium tetrachloroferrate(III)(1), one of the more frequently cited ferricenium salts, has recently attracted biomedical interest because of its pronounced antineoplastic activity against Ehrlich ascites murine tumor. In this paper, synthetic methods are reinvestigated in an effort to prepare pure(1) free from a common contaminant, diferriceniumμ-oxo-bis(trichloroferrate)(3). The oxodiferrate, or mixtures of this salt with(1), can readily be converted into pure(1) under acidic conditions. Conversely, dimerization of(1) with participation of water to give the oxodiferrate(3) is brought about by recrystallization of the former from moist acetonitrile/methanol in the presence of base; this reaction thus represents a simple procedure for the preparation of pure(3) from crude(1) readily obtainable by the long known interaction of ferrocene and iron(III) chloride in indifferent media. The i.r. and electronic absorption spectra of(1) are presented, as are the Mossbauer and x-ray photoelectron spectra. The room-temperature effective magnetic moment, 6.40μB, of the salt is lower than would be expected on the basis of typical ferricenium cation (2.4μB) and tetrachloroferrate(III) anion (5.9μB) moments determined for related salts. This suggests the possibility of weak inter- or intra-molecular antiferromagnetic interaction in the crystal.