engleski

Monothiocyanatoiron(III) complex in dichloromethane: methanol solvent mixture.

Complexation of ferric ion with thiocyanate in dichloromethane:methanol solvent mixture was studied because of our interest in the analytical uses of ferrous-to-ferric transformations in non-aqueous media. Molar absorptivity and composition of the complex, as well as solvolysis constant and stability constant of the complex as function of the composition of the solution were determined by spectrophotometry. The composition of the complex throughout the range of solubility 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 (13700 &plusmn ; ; 700) dm3 mol-1 cm-1. Solvolysis constant was similar to the value in water, Ks = 7.0 ´ 10-3 mol dm-3. Stability constant of the complex, on the other hand, was strongly influenced by concentration of the acid. The extrapolation to the infinite acid concentration yielded stability constant 40500 dm3 mol-1, which is adequate for the analytical use of the complex in non-aqueous medium.

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

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