Studies on the interaction of selenite and selenium with sulfur donors. Part 3. Sulfite

Abstract

Elemental selenium dissolves in sulfite solution to form selenosulfate ion: Se + SO 3 2− = SeSO 3 2− .The formation constants for this equilibrium at temperatures from 0 to 35 °C are reported for the first time. The isomeric thioselenate anion, SSeO 3 2− , is not, however, produced by the reaction of sulfur with selenite nor is the selenoselenate ion, Se 2 O 3 2− , formed from selenium and selenite. Selenotrithionate is formed rapidly from the reaction of selenous acid with sulfite and hydrogen sulfite according to: HSeO 3 − + 3 HSO 3 − = Se(SO 3 ) 2 2− + SO 4 2− + 2H 2 O.Two isomers of the selenotrithionate ion are observed by Se-77 NMR and Raman spectroscopy, one with O-bonded Se, Se(OSO 2 ) 2 2− , and the other with S-bonded Se, Se(SO 3 ) 2 2− . Both isomers are formed in reactions with hydrogen sulfite but only the O-bonded isomer is formed in sulfite solutions at ambient temperatures. The Raman and Se-77 NMR spectra of the various sulphur–selenium anions formed are given and the parallel with the reactions of selenous acid and thiols is discussed. Keywords: selenium, sulfite, selenosulfate, selenotrithionate, Se-77 NMR, Raman spectroscopy, equilibria, aqueous solutions.