Endogenous and Exogenous Ligand‐Dependent Formation of a Superoxide‐Bridged Dicobalt(III) Complex and Mononuclear CoIII Complexes with Amide‐Based Macrocyclic Ligands

Abstract

AbstractWe 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 Å). Complex 1 can be synthesized by the reaction of in situ generated [Co2+(LH)] species with O2 or KO2 as well as by the reaction of (Et4N)[Co3+(LH)(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(LCl)(Cl)(dmf)] (3) and [Co(LMe)(Cl)(dmf)] (4) under identical reaction conditions. Furthermore, the reaction of H2LH with Co(OAc)2 yielded the mononuclear Co3+ complex [Co(LH)(η2‐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.