Kinetics of dissociation of iron(III) complexes of Tiron in aqueous acid

The kinetics of dissociation of the mono, bis, and tris complexes of 1,2-dihydroxy-3,5-benzenedisulfonate (Tiron) have been examined as a function of (H+) and temperature. The rate constants and activations parameters for the forward and reverse reactions were obtained and indicated the presence of monoprotonated Tiron complexes. A mechanism has been proposed which involves the substitution of Fe(L)2 and Fe(L)3 complexes by dissociative activation, promoted by catecholate ligands.