OXYGEN-TRANSFER FROM PH(4)PHSO(5) TO MANGANESE PORPHYRINS - KINETICS AND MECHANISM OF THE FORMATION OF THE OXO SPECIES IN HOMOGENEOUS SOLUTION

The kinetics and mechanism of the oxygenation of Mn(TMP)Cl, Mn(TDCPP)C l and Mn(Br(8)TMP)Cl by Ph(4)PhSO(5) has been investigated in 1.2-dich loroethane and acetonitrile. In both solvents the reaction takes place only in the presence of species acting as axial ligands. of the manga nese porphyrins, e.g. imidazole or 4-tert-butylpyridine whose associat ion constants to the metal have: been measured. The rates of disappear ance of the manganese porphyrin and of the appearance of the oxo-speci es, obtained by the stopped-flow, technique, are identical within the experimental error. This finding, together with the determination of t he kinetic law of the reaction allows us to suggest that the oxygen tr ansfer process may be a simple bimolecular reaction or that, if an int ermediate is formed, it is rather short lived.