We report that redox-inactive Sc3+ can trigger O-2 activation by the Fe-II(TMC) center (TMC = tetramethylcyclam) to generate the corresponding oxoiron(IV) complex in the presence of BPh4- as an electron donor. To model a possible intermediate in the above reaction, we generated an unprecedented Sc3+ adduct of [Fe-III(eta(2)-O-2)(TMC)](+) by an alternative route, which was found to have an Fe3+-(mu-eta(2):eta(2)-peroxo)-Sc3+ core and to convert to the oxoiron(IV) complex. These results have important implications for the role a Lewis acid can play in facilitating O-O bond deavage during the course of O-2 activation at non-heme iron centers.