[en] Complete text of publication follows. The involvement of high-valent iron-oxo intermediates in biological, environmental, and industrial processes is of current interest. Fe^VIO₄^2- is relatively stable and is a potential oxidant in 'green' treatment of polluted waters. By contrast, Fe(V) and Fe(IV) are short-lived transients when produced in aqueous solution in the absence of strongly bonding ligands other than hydroxide, a feature that has limited studies of its reactivity. Fe^VO₄^3- and Fe^IVO₄^4- have been suggested to be the intermediates in the oxidation of inorganic and organic compounds by Fe^VIO₄^3-. Fe^VO₄^3- can be generated easily in the presence of excess Fe^VIO₄^2- through the use of reducing carbon-centered radicals produced in pulse radiolysis. The decay of the oxyiron(V) species is dependent on pH, where completely deprotonated Fe^VO₄^3- decays to a longer lived transient (t_1/2 ∼ seconds) via a first-order process. However, as the pH is lowered, oxyiron(V) disappears by second-order kinetics to form ferric ions and hydrogen peroxide. The second order rate constant observed in the disappearance of Fe(V) increases as the pH is lowered and is of the order of 10⁷ M^-1s^-1. Oxyiron(IV) complex with a simple inorganic ligand, P₂O₇^4- in basic medium can be generated from the corresponding parent complex by oxidation with OH/O^- radical in aqueous solutions. The pyrophosphate complex of iron(IV), formed at pH ≥ 10 is short lived (t_1/2 = 100-600 ms). This complex of iron(IV) disappears by a second order process to form a Fe(III) pyrophosphate complex and molecular oxygen. A premix pulse radiolysis was used to measure the reactivity of Fe^VIO₄^2-, Fe^VO₄^3-, and Fe^IVO₄^4- with cyanides, oxysulfur species, and aminopolycarboxylates (APCs) and their radicals. The oxidation rates decrease with increase in pH and are, in the order of Fe^VO₄^3- > Fe^IVO₄^4- > Fe^VIO₄^2-. Reduction rate constants of Fe^VIO₄^2- to Fe^VO₄^3- by ^·CONH₂, ^·SO₃^- and S₄O₆^·3- radicals were found to be 2.6 ± 0.6 x 10⁹, 1.9 ± 0.3 x 10⁸ and 7.5 ± 0.8 x 10⁷ M^-1 s^-1. The oxidation of cyanides by Fe(V) indicate a two-electron transfer with SCN^- while one-electron reduction of Fe^V to Fe^IV to Fe^III takes place in case of CN^-. The formation of a Fe(IV)-cyano complex in reduction of Fe^V by metalcyanide will be discussed. The reaction rates of Fe^VO₄^3- with the two oxysulfur ions were separated by an order of magnitude, with SO₃^2- reacting at 3.9 ± 0.3 x 10⁴ while S₂O₃^2- reacted with Fe(V) at 2.1 ± 0.1 x 10³ M^-1 s^-1 at pH 11.4. Measurements for Fe^VO₄^3- reactivity with oxy-sulfur species suggest two-electron reduction. Fe(V) reactivity with APCs at pH 12.5 increase in order tertiary < secondary < primary amines and proceed via a two-electron oxidation.