Unusual stabilization of manganese(III) during the cooxidation of dimethylformamide and manganese(II) by chromium(VI)

The kinetics of the formation and decomposition of Mn-III have been investi gated spectrophotometrically in acidic media at 25 degreesC. The complete r ate law for Mn-III formation is Cr-VI + DMF + Mn-II (H+) under right arrow Mn-III + CO2 + Me2NH + Cr-III (1 ) Mn-III + DMF (H+) under right arrow Mn-II + CO2 + Me2NH (2) expressed by k(obs1) = k(1)k(1)'K-a1[H+][DMFH+][Mn-II]/{1 + K-a1[H+]}. Mn-I II reduction by DMF follows the rate law k(obs2) = k(2)K(h)[DMF][H+](2)/{[H +] + K-h}. The above results are accounted for by a mechanism involving the intermediacy of Cr-IV.