Synthesis, characterization and electrochemistry of carboxamido Co(III) complexes: The crystal structure of [CoIII(Mebpb)(N-MeIm)2]BPh4·CH3OH

Three cobalt(III) complexes of the type trans-[CoIII(Mebpb)(amine)2]X {Mebpb2− = N,N′-bis(pyridine-2-carboxamido)-4-methylbenzene dianion, and amine = N-methylimidazole (N-MeIm) (1), 3-methylpyridine (3-MePy) (2), 3-acetylpyridine (3-AcPy) (3), X = BPh4- (1), ClO4- (2, 3)} were synthesized and characterized by elemental analyses, IR, UV–Vis, and 1H NMR spectroscopy. The structure of 1·CH3OH was determined by X-ray crystallography and was found to have a distorted octahedral geometry around Co. The electrochemical behavior of these complexes with the goal of evaluating the effect of axial ligation on the redox properties is also reported. The reduction potential of Co(III), ranging from −0.63 V for (1) to −0.20 V for (3) shows a relatively good correlation with the σ-donor ability of the axial ligands.

Graphical abstractCo(III) complexes of pyridine carboxamide ligand, H2Mebpb, with two axial amine ligands have been synthesized and characterized, and the X-ray crystal structure of trans-[Co(Mebpb)(N-MeIm)2]BPh4·CH3OH has been determined. The CoIII/II redox potentials in these complexes are sensitive to the donor strength of the axial ligands. The irreversible CoIII/II redox process shows tendency towards becoming quasi-reversible in the presence of excess amine.Figure optionsDownload full-size imageDownload as PowerPoint slide