The influence of electron-donating monodentate ligands L-2, such as hexamethylphosphoric triamide (HMPA) and dimethylformamide (DMF), on the mechanism of tris(acetylacetonato) iron(III)-catalyzed oxidation of ethylbenzene with molecular oxygen was kinetically studied. It was found that the admixtures of L-2 cause a nonadditive (synergistic) increase in the rate of ethylbenzene oxidation catalyzed by Fe(III)(acac)(3), as well as a growth in the alpha-phenylethyl hydroperoxide selectivity (S-PEH) and/or ethylbenzene conversion (C) relative to the Fe(III)(acac)(3) catalysis in the absence of L-2, changes that are due to the formation of more active complexes, mFe(III)(acac)(3) center dot n L-2 and Fe(II)(acac)(2) center dot L-2 (L-2 is HMPA or DMF) and products of Fe(II)(acac)(2) center dot L-2 (L-2 is DMF) transformation. The most significant effects of ligands L-2 on SPEH and C was revealed in the case of catalysis by the {Fe(III)(acac)(3)-HMPA} system at 80 degrees C. In the presence of the {Fe(III)(acac)(3)-DMF} catalyst system, methyl phenyl carbinol (MPC) was produced at a selectivity of S-MPC congruent to 58%, a value that exceeds SPEH = 25-30% at the initial steps of ethylbenzene oxidation. The formation mechanism for the principal products-ethylbenzene hyroperoxide, acetophenone, and methyl phenyl carbinol-of ethylbenzene oxidation catalyzed by Fe(III)(acac)(3) in the presence of HMPA and DMF was established. The activity of the Fe(II)(acac)(2) center dot L-2 complexes formed during ethylbenzene oxidation catalyzed by {Fe(III)(acac)(3)-L-2} (L-2 is HMPA or DMF) at the microsteps of chain initiation (O-2 activation) and propagation in the presence of the catalyst (Ct) (Ct + RO2 center dot ->) was evaluated, and the role of these steps in the mechanism of the iron-catalyzed oxidation of ethylbenzene to a-phenylethyl hydroperoxide was discussed.