Although int1 is only an early stage intermediate in the mechanism considered here, the FMO framework of understanding the nucleophlicity of [M(O 2 ) 4 ] x -has implications for the more general engineering of CO 4 -containing species from metal-peroxide precursors. In particular, modifications to L n M -O 2 (where L n represents supporting ligands) that raise the energy of the π * HOMO should promote CO 4 2formation. Modifications that achieve this effect, be they through alterations to the metal center, counterion, or environment, represent a rational design strategy for