Reduction of selenium(IV) and complexation of selenium(0) with 2-mercaptoethanol

Abstract

Selenium(IV) can be reduced to the elemental state with 2-mercaptoethanol in weakly acidic, neutral and alkaline media. In this redox reaction, 2-mercaptoethanol is oxidised to bis(2-hydroxyethyl) disulphide. The reaction rate for the reduction of H₂SeO₃ with 2-mercaptoethanol is directly proportional to the square of the ligand concentration and inversely proportional to the square root of the hydrogen ion concentration. When the ligand, L, is in excess, the elemental Se can re-dissolve in the form of a complex, i.e., SeL₆, where the zero valency of Se is retained as in metal carbonyl compounds. The SeL₆ complex is stable only in polar solvents. The maximum absorption of the complex in aqueous solution was measured at 380 nm.