Electrochemical and Catalytic Properties of oxo-ruthenate(VI) in Aqueous Alkaline Medium

摘要

The complex K2[Ru(III)Cl5(H2O)] has been prepared and characterized by different spectroscopic techniques (IR and UV-VIS). The electrochemical properties of this complex were investigated at different pH's using Robinson buffer solutions. The cyclic voltammograms exhibited three redox different oxidation and potential peaks due to generation of Ru(III), Ru(IV), Ru(V) and Ru(VI) ions. The catalytic activity of K2[Ru(III)Cl5(H2O)] towards the hydration of some aromatic and three heterocyclic nitriles to their corresponding amides was investigated with excess of three co-oxidants K2S2O8, NaOCl and KBrO3. A number of factors have been investigated and the best yields were obtained with K2S2O8 as a co-oxidant in a 1.0 M KOH at 80 °C. Both spectroscopic and electrochemical techniques were used to establish the nature of active species in this catalytic reaction and the active catalyst was found to be K2[Ru(VI)O3(OH)2], as well as to explain the possible reaction mechanism. The suggested mechanism included the coordination of nitrile to ruthenium center followed by liberation of the corresponding amide and the active complex again.