A Dicobalt Coordination Complex with a Short Cobalt-Cobalt Distance

The existence of a metal-metal bond in organometallic and coordination complexes is a very important aspect. Metal-carbonyl, carbene-metal-carbonyl and metal-carbene complexes were studied for having this feature. Herein, an air stable dark green color dicobalt coordination complex [Co(III)2(hep)3(N3)3] (1) [hepH = 2-(2-ethylhydroxy)pyridine] with three μ-alkoxide bridges has been synthesized and characterized by X-ray single crystal diffraction, NMR and UV/vis spectroscopy. Complex 1 has a short Co⋅⋅⋅Co distance (2.595(6) Å) and thus it has been studied by theoretical calculations. QTAIM (quantum theory of atoms in molecules) as well as EDA-NOCV analysis (energy decomposition analysis - natural orbitals for chemical valence) do not indicate any significant metal-metal interaction. The bonding in 1 can be best represented by the interaction of two alkokxy bridged valence electrons fragment Co(III)(hep)2N3 (3d6) with Co(III)(hep)(N3)2 (3d6) where the donation of the lone pair of electrons from three bridging Ohep-atoms stabilizes the dinuclear Co(III) complex. Additionally, thermolysis of 1 at 550 oC led to the formation sponge like Co3O4 oxide.