Synthesis and Catalytic Reactivity of a Dicopper(II) μ-η2:η2-Peroxo Species Supported by 1,4,7-Tri-tert-butyl-1,4,7-triazacyclononane

O-2-derived CunO2 adducts are attractive targets for aerobic oxidation catalysis because of their remarkable reactivity, but oxidation of the supporting ligand limits catalytic turnover. We report that (t)Bu(3)tacn (1,4,7-tri-tert-butyl-1,4,7-triazacydononane) supports a dicopper(II) mu-eta(2):eta(2)-peroxo species with the highest solution stability outside of an enzyme. Decomposition of this species proceeds without oxidation of the (t)Bu(3)tacn ligand. Additive-free catalytic aerobic oxidation reactions at or above room temperature are described, highlighting the potential of oxidatively robust ligands in aerobic copper catalysis.