Synthesis, Characterization, and Reactivity of Cobalt ACHTUNGTRENNUNG(III)–Oxygen Complexes Bearing a Macrocyclic N-Tetramethylated Cyclam Ligand

Oxygen-coordinating metal species, such as metal–peroxo, –hydroperoxo, and –oxo complexes (Scheme 1), have been frequently invoked as reactive intermediates in the catalytic cycles of dioxygen activation by metalloenzymes, such as heme and nonheme iron monooxygenases and copper-containing enzymes. In biomimetic studies, synthetic analogues of these active oxygen intermediates have been intensively investigated to understand their structures, mechanisms of interconversion, and the factors that control their chemical reactivities in oxidation reactions. In those studies, it has been shown that supporting ligands play an important role in tuning the geometric and electronic structures, stabilities, and reactivities of the oxygen-coordinating metal complexes. One notable example of the supporting ligands is N-tetramethylated cyclam (TMC) and its derivatives, which have proved to be versatile ligands in the biomimetic chemistry of dioxygen activation by metal complexes (see Scheme 2 for the ligand structures of n-TMC). A variety