Oxidation of Toluene by CO(lll) Salts -Effect of Added Metal Salts-

Abstract

Although Co(III)acetate oxidizes aromatic compounds in acetic acid solution in the absence of oxygen via an electron transfer process, other metal acetates at higher valence state such as Mn(III), Cu(II) or Ce(IV) acetates show a very low activity in the oxidation of toluene. It has now been found that the activity of Co(III) in the oxidation is remarkably reduced by the addition of other metal acetates at lower valence state as well as at higher valence state. When the molar ratio of other metal acetates to Co(III)exceeds a certain value, Co(III) loses its activity for the oxidation of toluene. The order of inhibition effect is as follows.
Mn(II) Mn(III) - Ce(IV) Cu(II)
Visible absorption spectra suggest that inhibition effects by added salts are due to the formation of polynuclear complex between Co(III) and other metal acetates. However, metal combination Cu(II)-Co(III) which is quite inactive in the oxidation of toluene presents the same activity as that of Co(III) in the oxidation of α-methyl naphthalene. Accordingly, the lower activity in the oxidation of toluene of the polynuclear complexes of Co(III) with added salts can be attributed to a reduced redox pontential of the complexes compared to Co(III) acetate.