The synthesis and characterization of [Fe-2(mu-O2CArTol)(4)L-2] complexes, where L is benzylamine or 4-methoxybenzylamine (BA(p-OMe)), are described. The reaction of the latter diiron(II) complex with dioxygen at -78 degreesC affords a metastable mixed-valent Fe(II)Fe(III) green intermediate. When 02 is introduced at ambient temperature, N-dealkyation occurs to yield anisaldehyde, eliminating N-oxidation as a viable pathway for the reaction. Use of [Fe-2(mu-CAr (Tol))(4)(alpha-d(1)-BA(p-OMe))(2)] allowed a deuterium kinetic isotope of similar to3 to be determined.