Kinetics and mechanisms of complex formation of gallium(III) and indium(III). The reactions with 4-(2-pyridyiazo)resorcinol in water and other mixed solvents

Abstract

The reactions of 4-(2-pyridylazo)resorcinol (H₂ par) with Ga ^III and In^III have been studied in water and aqueous mixtures with methanol, acetonitrile, dimethyl sulphoxide, and NN-dimethylformamide at 25.0 °C and / 0.80 mol dm^–3(NaClO₄). The equilibrium constant, K_c, for M(Hpar)²⁺ formation (M = In or Ga) has been evaluated spectrophotometrically and its variation with the medium composition has been discussed with reference to different properties of the solvents. The kinetics of dissociation of M(Hpar)²⁺ by H⁺ have been investigated. The derived formation rate constants are discussed with reference to the mechanisms which operate for the different reacting metal species.