Synthesis, characterization, electrochemical behavior, and catalytic activity of cobalt(II) metal complexes with pincer-type methylbenzamide derivative ligands

The pincer type new benzamide derivative ligands; N,N'-(2,2'-azenidiil-bis(2,1-phenylene))bis(2-methyl-benzamide) (H3L1), N,N'-(2,2'-azenidiil-bis(2,1-phenylene))bis(3-methylbenzamide) (H3L2), and N,N'-(2,2'-aze-nidiil-bis(2,1-phenylene))bis(4-methylbenzamide) (H3L3) were successfully synthesized from bis(2-aminophenyl) amine with addition of different substituent benzoyl chloride derivatives. Cobalt complexes of these ligands were synthesized in an inert atmosphere Glove-Box system. The synthesized compounds have been characterized by H-1 NMR, C-13 NMR, COSY, HMQC, UV-Vis, and FT-IR techniques. Crystal structure of suitable compounds was also determined by single crystal X-ray diffraction analysis. Electrochemical properties of the ligands and their cobalt complexes were investigated by cyclic voltammetry. The catalytic activities of ligands and K-2[Co(H3L1)(2)], K-2[Co(H3L2)(2)], K-2[Co(H3L3)(2)] complexes were also examined by aerobic oxidation reaction. Triphenylphosphine and diphenyl sulfide were used as substrates in these oxidation reactions. After 24 h, K-2[Co(H3L1)(2)] pincer complex showed highest catalytic activity with 81% conversion of triphenylphosphine to triphenylphosphine oxide.