Stopped-flow kinetic studies of the oxidation of FeIII-TAML catalysts, [⌈F⌈e{1,2-X2C6H2-4,5-(⌉NCOCMe2NCO)2CMe2}(OH2)]- (1), by t-BuOOH and H2O2 in water affording FeIV species has helped to clarify the mechanism of the interaction of 1 with primary oxidants. The data collected for substituted FeIII-TAMLs at pH 6.0-13.8 and 17-45 °C has confirmed that the reaction is first order both in 1 and in peroxides. Bell-shaped pH profiles of the effective second-order rate constants kI have maximum values in the pH range of 10.5-12.5 depending on the nature of 1 and the selected peroxide. The "acidic" part is governed by the deprotonation of the diaqua form of 1 and therefore electron-withdrawing groups move the lower pH limit of the reactivity toward neutral pH, although the rate constants kI do not change much. The dissection of kI into individual intrinsic rate constants k1 ([FeL(OH2)2]- + ROOH), k2 ([FeL(OH2)OH)]2- + ROOH), k3 ([FeL(OH2)2]- + ROO-), and k4 ([FeL(OH2)OH)]2- + ROO-) provides a model for understanding the bell-shaped pH-profiles. Analysis of the pressure and substituent effects on the reaction kinetics suggest that the k2 pathway is (i) more probable than the kinetically indistinguishable k3 pathway, and (ii) presumably mechanistically similar to the induced cleavage of the peroxide O-O bond postulated for cytochrome P450 enzymes. The redox titration of 1 by IrIV and electrochemical data suggest that under basic conditions the reduction potential for the half-reaction [FeIVL(=O)(OH2)]2- + e- + H2O → [FeIIIL(OH)(OH2)]2- + OH- is close to 0.87 V (vs NHE). [ABSTRACT FROM AUTHOR]