Abstract

The existence of two different manganese (III)-cyanide complexes in cyanide solution is detected when manganese (II)-cyanide solutions are oxidized with hydrogen peroxide. A brown solution is obtained first which colour fades to give a nearly colourless solution. Manganese (III) is present both before and after this process.

The electrochemical oxidation of the brown complex at a stationary platinum electrode in a stirred cyanide solution gives two one-electron reversible anodic waves with half-wave potentials at about 0.03 and 0.60 volt. vs S. C. E. respectively. Both anodic waves are diffusion-controlled. A tentative mechanism is proposed for the diffusion processes controlling both electrode reactions. A binuclear manganese (III) cyanide complex is oxidized by a one-electron process into a mixed Mn(III). Mn(IV) species in the first reaction, which is oxidized to a Mn(IV). Mn(IV) binuclear species in the second reaction. The diamagnetic behaviour shown by the brown manganese (III) complex confirms its binuclear structure.