Summary
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 Mössbauer and x-ray photoelectron spectra. The room-temperature effective magnetic moment, 6.40μ B, of the salt is lower than would be expected on the basis of typical ferricenium cation (2.4μ B) and tetrachloroferrate(III) anion (5.9μ B) moments determined for related salts. This suggests the possibility of weak inter- or intra-molecular antiferromagnetic interaction in the crystal.
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P. Köpf-Maier, H. Köpf and E. W. Neuse,Angew. Chem., 96, 446 (1984);J. Cancer Res. Clin. Oncol, in press.
R. Prins, A. R. Korswagen and A. G. T. G. Kortbeek,J. Organometal. Chem., 39, 335 (1972).
J. Spilners,J. Organometal. Chem., 11, 381 (1968).
A. N. Nesmeyanov, E. G. Perevalova, R. V. Golovnya, T. V. Nikitina and N. A. Simukova,Izv. Akad. Nauk SSSR, Old. Khim. Nauk, 739 (1956).
L. P. Motz and R. P. Pinnell,J. Organometal. Chem., 54, 255 (1973).
H. P. Fritz and L. Schäfer,Z. Naturforsch., 19b, 169 (1964).
O. Traverso, R. Rossi and V. Carassiti,Synth. React. Inorg. Metal-Org. Chem., 4, 309 (1974).
L. Wilputte-Steinert,J. Mol. Catal, 4, 113 (1978).
R. Prins and A. G. T. G. Kortbeek,J. Organometal. Chem., 33, C33 (1971).
P. Sohár and J. Kuszmann,J. Mol. Struct., 3, 359 (1969). Although the salt prepared by these authors was indeed the tetrachloroferrate(1), the structure assigned in that work was later proven incorrect (see refs. 13 and 31).
M. R. Churchill, A. G. Landers and A. L. Rheingold,Inorg. Chem., 20, 849 (1981).
A. N. Nesmeyanov, E. G. Perevalova and L. P. Yureva,Chem. Ber., 93, 2729 (1960).
R. A. Stukan and L. P. Yureva,Dokl. Akad. Nauk SSR, 167, 1311 (1966).
P. Maitlis and J. D. Brown,Z. Naturforsch., 20b, 597 (1965).
Room-temperature data for FeCl2 · H2O and FeCl2 · 2H2O are, respectively,δ = 1.13 and 1.03 mms−1, ΔEq = 2.03 and 2.50 mms−1: N. N. Greenwood and T. C. Gibb,Mössbauer Spectroscopy, Chapman and Hall Ltd., London, 1971, p. 119. In contrast, a hexachlorodiferrate anion structure, implying an average-valence FeII/FeIII system, should produce more negative isomer shifts and appreciably smaller quadrupole splittings. Thus, ferrous/ferric electron delocalization in ilvaite, melanite and other minerals possessing suitable Fe2+ and Fe3+ sites causes room-temperature isomer shifts in the vicinity of 0.7–0.8 mms−1, with quadrupole splittings in the range of 1.5–1.8 mms−1:
D. A. Nolet and R. G. Burns,Geophys. Res. Lett., 5, 821 (1978);Phys. Chem. Minerals, 4, 221 (1979).
K. B. Schwartz, D. A. Nolet and R. G. Burns,Amer. Mineral, 65, 142 (1980).
Room-temperature data reported for FeCl2 areδ = 1.26 rams−1 and ΔEq = 0.80 mms−1: K. Ôno, A. Ito and T. Fujita,J. Phys. Soc. Jap., 19, 2119 (1964).
J. C. A. Boeyens, P. C. Lalloo, E. W. Neuse and H. H. Wei,S. Afr. J. Chem., 37, 32 (1984).
J. C. A. Boeyens, F. B. D. Khan and E. W. Neuse,S. Afr. J. Chem., 37, 187 (1984).
Preliminary measurements place the room-temperature effective magnetic moment of(3) in the vicinity of 3.3 μB.
The formation of(3) from ferrocene and FeCl3 becomes feasible if the reaction is performed in a mutual solvent for product and reactants under anaerobic conditions, followed by oxidation of intermediary ferricenium trichloroferrate(II) (Ref. 17; see also S. M. Aharoni and M. H. Litt,J. Organometal. Chem., 22, 171 (1970)).
C. A. McCammon and R. G. Burns,Amer. Mineral, 65, 301 (1980); E. Mattievich and J. Danon,J. Inorg. Nucl. Chem., 39, 569 (1977).
T. B. Swanson and V. W. Laurie,J. Phys. Chem., 69, 244 (1965).
I. Pavlík and J. Klikorka,Coll. Czech. Chem. Commun., 30, 664 (1965). These authors list additional medium-strong to strong maxima at 1594, 1192, 1114 and 412 cm−1 (determined on Nujol mulls), which in our spectra are absent or, at best, of very low intensity (1114, 412 cm−1).
B. F. Gächter, J. A. Koningstein and V. T. Aleksanjan,J. Chem. Phys., 62, 4628 (1975).
Y. S. Sohn, D. N. Hendrickson and H. B. Gray,J. Am. Chem. Soc., 93, 3603 (1971).
E. W. Neuse and M. G. Meirim,Transition Met. Chem., 9, 205 (1984).
T. N. Mzimela and E. W. Neuse,S. Afr. J. Chem., 34, 47 (1981); binding energies recalculated with Eb(Cls) = 284.6 eV used for calibration.
T. Birchall and I. Drummond,Inorg. Chem., 10, 399 (1971).
I. Motoyama, M. Watanabe and H. Sano,Chem. Lett., 513 (1978).
P. R. Edwards and C. E. Johnson,J. Chem. Phys., 49, 211 (1968).
C. A. Clausen and M. L. Good,Inorg. Chem., 9, 220 (1970).
G. M. Bancroft, A. G. Maddock, W. K. Ong and R. H. Prince,J. Chem. Soc., A., 723 (1966).
E. F. Paulus and L. Schäfer,J. Organometal Chem., 144, 205 (1978).
R. Prins,Mol. Phys., 19, 603 (1970).
A. P. Ginsberg and M. B. Robin,Inorg. Chem., 2, 817 (1963).
A. Earnshaw,Introduction to Magnetochemistry, Academic Press, London, 1968.
Assessed by comparison with spectra of synthetic mixtures of (1) and (3) at various mixing ratios.
Attempts to achieve enhanced recoveries were frustrated by the tendency of ferricenium salts to degrade in aged solutions, thus crystallizing from the final mother-liquors in a highly impure state.
The precipitation of Prussian Blue in the presence of K3Fe(CN)6, similarly observed with (3), is entirely unexpected for the ferric iron in the anion of (1). As no rapid precipitation occurs with other tetrachloroferrates(III), such as NMe4FeCl4 or PhCH2N(Me)3FeCl4, one is led to conclude that the ferricenium cation plays a vital part in some rapid redox mechanism generatingin situ the FeII" species required for Prussian Blue formation. Cyanide anion reduces ferricenium cation to ferrocene, which conceivably may be reoxidized with concomitant reduction of FeIIICl −4 to FeIICl 2−4 .
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Neuse, E.W., Mojapelo, B.S. & Ensling, J. Preparative and spectroscopic features of ferricenium tetrachloroferrate(III). Interconversion to diferricenium μ-oxo-bis[trichloroferrate(III)]. Transition Met Chem 10, 135–141 (1985). https://doi.org/10.1007/BF00641583
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DOI: https://doi.org/10.1007/BF00641583