Four consecutive and reversible one-electron reduction processes are observed as the initial reduction steps in the voltammetry of α-[S 2 Mo 18 O 62 ] 4- in acetonitrile. This contrasts with the initial tour reversible two-electron two-proton reduction process identified previously in acidified acetonitrile. The one- and two-electron reduction products in acetonitrile have been isolated as the green and blue salts, (Bu n 4 N) 6 [S 2 Mo 18 O 12 ] and (Bu n 4 N) 6 [S 2 -Mo 18 O 62 ] respectively.