Kinetics and mechanism of oxidation of two new chromium(lll) complexes by hydrogen peroxide

Abstract

The kinetics and mechanism of oxidation of [Cr(1,3-diaminopropane)₂(NCS)₂]NCS.4H₂O and [CrLCl₂]Cl.2H₂O(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°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) oxo-product. Different kinetic parameters of the reactions have been calculated and the general mechanism of the reactions has been postulated.