KINETICS AND MECHANISM OF THE DECOMPOSITION OF HYDROGEN-PEROXIDE CATALYZED BY MN(II)-BIS-SALICYLALDIMINE COMPLEXES

The tetradentate Schiff bases N,N'-bis(salicylidene) ethylenediamine ( salen), N,N-bis-(salicylidene) hexylenediamine (salhex), and N,N'-bis( salicylidene)-o-phenylenediamine (sal-o-phen) are very strongly adsorb ed by cation exchange resins (Dowex-50W) with manganese(II) as a count er ion, forming stable complexes. The kinetics of the catalytic decomp osition of H2O2 in presence of these complexes has been studied in aqu eous medium. The decomposition reaction is first order with respect to H2O2 in the case of salen and sal-o-phen and third order in the case of salhex. The greater the ligand methylene chain length or the greate r the steric effect of the ligand, the greater will be the rate of rea ction. The reaction is governed by the entropy of activation. A reacti on mechanism is proposed.