Soluble methane monooxygenase (sMMO) carries out methane oxidation at 4 degrees C and under ambient pressure in a catalytic cycle involving the formation of a peroxodiiron(III) intermediate (P) from the oxygenation of the diiron(II) enzyme and its subsequent conversion to Q the diiron(IV) oxidant that hydroxylates methane. Synthetic diiron(IV) complexes that can serve as models for Q are rare and have not been generated by a reaction sequence analogous to that of sMMO. In this work, we show that [Fe-II(Me3NTB)(CH3CN)](CF3SO3)(2) (Me3NTB = tris((1-methyl-1H-benzo[d]imidazol-2-yl)methypamine) (1) reacts with O-2 in the presence of base, generating a (mu-1,2-peroxo)diiron(III) adduct with a low O-O stretching frequency of 825 cm(-1) and a short Fe center dot center dot center dot Fe distance of 3.07 angstrom. Even more interesting is the observation that the peroxodiiron(III) complex undergoes O-O bond cleavage upon treatment with the Lewis acid Sc3+ and transforms into a bis(mu-oxo)diiron(IV) complex, thus providing a synthetic precedent for the analogous conversion of P to Qin the catalytic cycle of sMMO.