Synthesis, Characterization and X-Ray Crystal Structure of a Cobalt(III) Complex with 2-Bis(pyridine-2-carboxamido)-4,5-dimethylbenzene Ligand

An octahedral cobalt(III) complex, trans-[(Me2bpb)Co(bzlan)2]ClO4 (1), with H2Me2bpb = N,N’-(4,5-dimethyl-1,2- phenylene)dipicolinamide and bzlan = benzylamine, has been synthesized and characterized by elemental analyses, IR, UV-Vis, and 1H NMR spectroscopy. The structure of this complex has been determined by X-ray crystallography. The Me2bpb^2- is a di-anionic tetradentate ligand furnishing a N4 set, such that two N atoms of the two pyridine rings and two amido N atoms occupy four equatorial positions. The two benzylamine ligands occupy the two axial positions leading to a distorted octahedral geometry around the central cobalt ion. The electrochemical behavior of this complex in acetonitrile solution indicates that the irreversible oxidation of 4,5-dimethylorthophenylene moiety and reduction of pyridine rings of the free ligand appear as reversible waves in the cyclic voltammogram of its cobalt(III) complex. Concomitant Co(III)/Co(II) redox process and solvolysis in acetonitrile solution is observed. This irreversible redox process becomes reversible in the presence of excess benzylamine.