Kinetics And Mechanism Of Oxidation Of Two New Chromium(Iii) Complexes By Hydrogen Peroxide

The kinetics and mechanism of oxidation of [Cr(1,3-diaminopropane)(2)(NCS)(2)]NCS.4H(2)O and [CrLCl(2)]Cl.2H(2)O (L = Schiff base, C17H24N4S2 derived, from condensation of N,N-bis-(2-aminoethyl)-1,3-propanediamine and thiophen-2-aldehyde) by hydrogen peroxide have been investigated spectrophotometrically at 30 degrees C. The reactions proceed through a rapid pre-equilibrium formation of a peroxide adduct which dissociates through cleavage of oxygen-hydrogen, metal-chlorine (rate-determining) and oxygen-oxygen bonds to give a dioxo Cr(IV) product which on further oxidation by a second H2O2 molecule gives Cr(VI) ore-product. Different kinetic parameters of the reactions have been calculated and the general mechanism of the reactions has been postulated.