Solvent effect in the kinetics of cobaloxime(II)-catalyzed oxidative dehydrogenation of 3,5-di-tert-butylcatechol by O2

Abstract

In the presence of triphenylphosphine~obaloxime(I]), 3,5-di-tert-butylcatechol undergoes catalytic oxidative dehydrogenation to the corresponding 1,2-be~zoquinone (DTBQ) at room temperatm:_o and atmospheric dioxygen pressure. The semiquinone anion radical (DBSQ') and its cobaloxime(lII) complex conI(DBSQ ") have been detected as intermediates by ESR spectroscopy. The kinetics were followed in benzene by measuring the dioxygen uptake as a function of time. The reaction is somewhat faster in MeOH, which is due to the greater stability of the hydrogen-bonded intermediate (X) formed from superoxocobaloxime (como~) and the catechol. H-atom abstraction occurs in the rate-determining decomposition of X.The system investigated is a functional model of catecholase (oxidase) activity, based on free-radical intermediates, a possibility recently demonstrated for certain oxidoreductases.

Co(III) and Ni(II) complexes of an anthracene appended aroyl hydrazone: Synthesis, crystal structures, DNA binding and catecholase activity

“…Mononuclear cobalt complexes showing catecholase activity are relatively rare in the literature [64][65][66][67][68][69]. So, cobalt(III) complex 1 is one of the few examples of a mononuclear cobalt(III) complex having catecholase activity for which both the single crystal X-ray structure and k cat value have been determined.…”

Iron-assisted, base-catalyzed biomimetic activation of dioxygen by dioximatoiron(II) complexes

“…Our earlier work was concerned with the biomimetic catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-H 2 dtbc), using the functional catecholase models [bis(dimethyl-glyoximato) cobalt(II)] [12][13][14][15] and [bis(dimethylglyoximato)iron(II)] [16,17] complexes (also known as cobaloxime(II) and ferroxime(II) derivatives, respectively). Kinetic investigations of these models were carried out to help elucidate the mechanism of the underlying biological catecholase reaction.…”

Synthesis and Characterization of Novel Organocobaloximes as Potential Catecholase and Antimicrobial Activity Agents

“…The catalytic activity of cobaloxime(II) derivatives[Co(Hdmg) 2 L 2 ], where H 2 dmg is dimethylglyoxime and L is Ph 3 P, py, and Et 3 N, in the oxidative dehydrogenation of hydroquinone and hydrazobenzene and in oxygen insertions into some organic substrates at room temperature and atmospheric dioxygen pressure has first been recognized in the 1980s . Oxidation of 3,5‐di‐ tert ‐butylcatechol by O 2 to the corresponding 1,2‐benzoquinone is catalyzed by the cobaloxime [Co(Hdmg) 2 (PPh 3 ) 2 ] in methanol and benzene . The overall stoichiometry is given by the equation: …”