Three Co(III)–Fe(II) complexes based on hexacyanoferrates: Syntheses, spectroscopic and structural characterizations

Red or orange crystals of [Co(NH3)6]2Cl2[Fe(CN)6] · 4H2O (1), [Co(en)3]2Cl2[Fe(CN)6] · 2H2O (2) and [Co(en)3]4[Fe(CN)6]3 · 21.6H2O (3) were isolated from the aqueous systems Co3+–LN–[Fe(CN)6]4− (LN = NH3, en = 1,2-diaminoethane). In all isolated samples the combination of Mössbauer (δ values were from the range −0.07 to −0.08 mm/s) and IR spectra (ν(Ctriple bond; length of mdashN) stretching vibrations in the range 2015–2047 cm−1) confirms the presence of low spin Fe(II) in [Fe(CN)6]4− anions. X-ray structure analyses corroborate the ionic character of all studied compounds. These contain diamagnetic [Co(NH3)6]3+ (1) or [Co(en)3]3+ (2 and 3) complex cations and diamagnetic [Fe(CN)6]4− complex anions. In compounds 1 and 2 chloride anions are present, too. All three compounds contain water of crystallization, in compound 3 as many as 21.6 molecules per formula unit.