Abstract
We report superoxide-bridged dicobalt(III) complex 1 supported by 13-membered amide-based macrocyclic ligand H2LH. Complex 1 displays a sharp radical-type EPR spectrum (g = 2.031) and a short O-O distance (1.303 angstrom). Complex 1 can be synthesized by the reaction of in situ generated [Co2+(L-H)] species with O-2 or KO2 as well as by the reaction of (Et4N)[Co3+(L-H)(Cl)(2)] (2) with KO2. In contrast, analogous macrocyclic ligands carrying Cl and CH3 substituents on the aromatic ring produced the mononuclear Co3+ complexes Co(L-Cl)(Cl)(dmf)] (3) and [Co(L-Me)(Cl)(dmf)] (4) under identical reaction conditions. Furthermore, the reaction of H2LH with Co(OAc)(2) yielded the mononuclear Co3+ complex [Co(L-H)(eta(2)-OAc)] (5) with a unique bidentate acetate group and a highly distorted six-coordinate geometry around the metal. Steric factors induced by the endogenous and exogenous ligands are believed to control the formation of the distinct cobalt complexes.