Octahedral Co(III) complexes of 2-(phenylimino)pyrrolyl ligands: Synthesis and structural characterisation

The reactions of CoCl2 with three equivalents of 2-(phenylimino)pyrrolyl sodium salts, performed under a nitrogen atmosphere, lead to the formation of the Co(III) complexes [Co(κ2N,N′-NC4H3C(H)N–C6H5)3] (2a), [Co(κ2N,N′-NC4H3C(CH3)N–C6H5)3] (2b) and [Co(κ2N,N′-NC16H9C(H)N–C6H5)3] (2c), accommodating three chelating iminopyrrolyl ligands. Complexes 2a–c were obtained in moderate yields, and their characterisation by 1H, 13C NMR and X-ray diffraction show they are diamagnetic and have an octahedral geometry about the cobalt centre, respectively. Uncharacterised products were obtained in the same reaction involving ligand precursors such as 2-(2,6-dimethylphenylimino)pyrrolyl sodium salts, which is attributed to a greater steric hindrance in the coordination of three of these bulkier ligands. The redox behaviour of complexes 2a–c shows an irreversible reduction wave with a peak potential in the range −3.2 to −3.7 V. Upon reduction, the complexes decompose giving rise, in the case of 2a, to a redox pattern compatible with the formation of [Co(κ2N,N′-NC4H3C(H)N–C6H5)2].