Ketonization of methylene of bis(benzimidazol-2-yl)methane by molecular oxygen under the catalysis of cobalt(II) ion

A cobalt(II) complex [Co((bnzim)2CO)Cl2] (1) (where (bnzim)2COdouble bond; length as m-dash; bis(benzimidazol-2-yl)methanone), was obtained by reacting cobalt(II) chloride with bis(benzimidazol-2-yl)methane ((bnzim)2CH2) in CH3OH/CH3CN and characterized using EA, IR, XRD and X-ray single crystal diffraction. The process of ketonization of methylene of (bnzim)2CH2 was investigated using spectroscopy and electrochemistry method. The experimental results reveal that there were new species forming in the reaction system and the formation of new species was related to the dissolving oxygen in the mixture. Oxygenation mechanism was thus proposed, in which oxygen atom transfer from a superoxo intermediate species {((bnzim)2CH2)Co(III)–O–Oradical dot} to the methylenic carbon of (bnzim)2CH2, and then goes O–O hemolytic cleavage and hydrogen migration to give intermediate species [Co((bnzim)2CHOH)]2+. The ketonization was achieved after [Co((bnzim)2CHOH)]2+repeating the process.