Density functional theory calculations were carried out in a study of the oxidation of benzene to phenol by N2O on a model (FeO)(1+)-ZSM-5 cluster: the [(SiH3)(4)AlO4(FeO)] cluster. This cluster models the reactivity of Fe3+ oxidic clusters. Results are to be compared with an earlier study (J. Phys. Chem. C 2009, 113, 15307) on a model Fe2+-ZSM-5 cluster. The true activation energies for the elementary reaction step in which phenol is produced appear to be comparable. The major difference between the two systems appears to be the relative stabilities of the intermediate phenolates. On the Fe3+-containing cationic cluster, this appears to be uniquely stable. This result suggests that the experimentally observed preference of Fe2+ sites over (FeO)(1+) on ZSM-5 for benzene oxidation to phenol by N2O is due to the reduced formation of adsorbed phenolate, which is possibly an intermediate for deactivation.