Kinetics of reaction with hydroxide ions and solubilities of iron(II) complex cations in aqueous urea solutions. Derivation of transfer chemical potentials for initial and transition states
Abstract
The solubilities in water at 298.15 K of perchlorates formed by three iron(II) complex cations containing di-imine ligands increase when urea is added. The complex salts are [Fe(phen)3](ClO4)2, [Fe(gmi)3](ClO4)2 and [Fe(bsb)3](ClO4)2. The solubility data are combined with solubility data for other salts in aqueous urea solutions, and analysed to obtain transfer chemical potentials for single ions using the tetraphenylarsonium tetraphenylboronate (TATB) extrathermodynamic assumption. The transfer parameters for the first two iron(II) complex cations listed above and for hydroxide ions are combined with kinetic data to yield the effects of added urea on transfer parameters for initial and transition states. The modest change in rate constants for reaction between hydroxide ions and iron(II)–phen complex in aqueous solution masks quite striking changes in reference chemical potentials of initial and transition states when urea is added.