Complexes of 4,4′-bipyridine with some iron(III) salts

Abstract

Hydrated iron(III) chloride, nitrate, and perchlorate form octahedral co-ordination polymers with 4,4′-bipyridine (4,4′-bipy) in ethanol and methanol media. The iron: 4,4′-bipy ratio is 1 : 1 in all these complexes. In ethanol, FeCl₃·6H₂O forms a polymer of empirical formula Fe(4,4′-bipy)O_0.5Cl₂ containing a linear Fe–O–Fe bridge, while a polymer of empirical formula Fe(4,4′-bipy)Cl₃ precipitates from methanol. Hydrated iron(III) nitrate and perchlorate give rise to complexes of empirical formulae Fe(4,4′-bipy)(NO₃)₃ and Fe(4,4′-bipy)(OH₂)₃(ClO₄)₃, respectively, independent of the solvent (ethanol or methanol) employed in their preparations. Infrared spectra Indicate the presence of only bidentate (bridging) 4,4′-bipy in the complexes Fe(4,4′-bipy)O_0.5Cl₂ and Fe(4,4′-bipy)Cl₃. Unrdentate (terminal) as well as bidentate (bridging) 4,4′-bipy molecules are present in Fe(4,4′-bipy)(NO₃)₃ and Fe(4,4′-bipy)(OH₂)₃(ClO₄)₃. Co-ordrnation of chloride and nitrate is also indicated by the i.r. spectra, while perchlorate is present only as the ionic form.