The aerial oxidation of cobalt(II) salt, in a methanolic solution, containing a hydrazone ligand, (E)-N′-(4-oxo-4-phenylbutan-2-ylidene)benzohydrazide (condensation product of benzoyl acetone and benzhydrazide, LH₂) leads to the coupling of two such ligand units through the formation of a rather long C–C bond [1.601(6) Å] giving rise to a dinuclear Co (III) hydrazone complex, [Co₂(L)₂(L′)₂]·0.25H₂O (L′ = C–C coupled hydrazone ligand). The structure of the complex has been determined by X-ray crystallography and IR, UV-Vis spectroscopy and elemental analysis have characterized the complex.