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

O2-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 tBu3tacn (1,4,7-tri-tert-butyl-1,4,7-triazacyclononane) supports a dicopper­(II) μ-η2:η2-peroxo species with the highest solution stability outside of an enzyme. Decomposition of this species proceeds without oxidation of the tBu3tacn 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.