Equimolar mixtures of trivalent metal perchlorates as constant-ionic-strength media in studies of complex formation in dimethyl sulphoxide. Iron(III) and aluminium(III) thiocyanate complex formation

Abstract

Equimolar mixtures of aluminium(III) and iron(III) perchlorates in dimethyl sulphoxide have been used as constant-ionic-strength media for studying the formation of complexes of the metal cations with the thiocyanate anion by spectrophotometric methods. Formation of the complexes has also been studied calorimetrically. The derived thermodynamic parameters are as follows: ΔG^⊖=–23.2±0.5 kJ mol^–1, ΔH^⊖= 5.04±0.04 kJ mol^–1 and ΔS^⊖= 95±1.8 J K^–1 mol^–1 for FeSCN(DMSO)²⁺₅ and ΔG^⊖=–15.2±1.7 kJ mol^–1, ΔH^⊖= 15.42±0.11 kJ mol^–1 and ΔS^⊖= 103±6 J K^–1 mol^–1 for AlSCN(DMSO)²⁺₅.