Kinetic of Reaction with Hydroxide Ions and Solubilities of Salts of Cobalt(III) Schiff Base Complexes in Water-Methanol Mixtures

Department of Chemistry, Faculty of Science, Assiut University, Sohag, Egypt

Manuscript received 7 April 1989, accepted 7 June 1989

Heterocyclic Schiff base complexes of Co^III are synthesised. The Schiff bases are tridentate and have dinitrogen and oxygen donors. SoIubilities and transfer chemical potentials of perchlorate, thiocyanate and nitrate salt of the (O^III complexes in watermethanol mixtures are reported. Transfer chemical potentials for the Co^III Schiff base cations are calculated Trends with solvent composition suggest that preferential solvation varies from negligible to very strong by methanol depending on the ligand structure and hydrophilic/hydrophobic character of the inorganic ions. Kinetics of reactions between hydroxide ion and the Schiff base complexes of Co^III in aqueous methanol mixtures follow a rate law with Kobs -K₁+K₂ [OH] or Kobs -K₂[OH^-] The analyses of the reactivity trends to initial and transition state show that the small increase of the rate constant is ascribed to a greater effect of solvent on the transition state.