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Original scientific paper

Monothiocyanatoiron(III) Complex in Dichloromethane–Methanol Solvent Mixture

Branka Mihaljević ; Ruđer Bošković Institute, Bijenička 54, P.O. Box 180, 10000 Zagreb, Croatia
Dušan Ražem ; Ruđer Bošković Institute, Bijenička 54, P.O. Box 180, 10000 Zagreb, Croatia

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page 249-255

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Complexation of FeIII ion with thiocyanate in dichloromethane–methanol solvent mixture was studied because of our interest in the analytical uses of FeII-to-FeIII transformations in non-aqueous media. Molar absorptivity and composition of the complex, as well as the solvolysis constant and the stability constant of the complex as a function of the solution composition were determined by spectrophotometry. The composition of the complex throughout the solubility range of the components was that of a monocomplex, [FeNCS]2+. In highly acidic solutions, molar absorptivity of the complex was not influenced by acid concentration and was (13 700 ± 700) dm3 mol-1 cm-1. The solvolysis constant was similar to the value in water, Ks = 7.0 × 10-3 mol dm-3. The stability constant of the complex, on the other hand, was strongly influenced by acid concentration. Extrapolation to the infinite acid concentration yielded the stability constant 40 500 dm3 mol-1, which is adequate for analytical uses of the complex in non-aqueous media.


iron(III), thiocyanate, thiocyanatoiron(III) complex, stability constant, spectrophotometry, non-aqueous medium

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