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

Abstract

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.

Keywords

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

Hrčak ID:

103175

URI

https://hrcak.srce.hr/103175

Publication date:

29.8.2003.

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