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,'-= SeSo3'-. The formation constants for this equilibrium at temperatures from 0 to 35°C are reported for the first time. The isomeric thioselenate anion, SseO,*-, is not, however, produced by the reaction of sulfur with selenite nor is the selenoselenate ion, Se20,'-, formed from selenium and selenite. Selenotrithionate is formed rapidly from the reaction of selenous acid with sulfite and hydrogen sulfite according to: HSe0,-+ 3 HS0,-= s~(so,),~-+ SO: -+ 2 H20. Two isomers of the selenotrithionate ion are observed by Se-77 NMR and Raman spectroscopy, one with 0-bonded Se, s~(oso,),~-, and the other with S-bonded Se, Se(.SO,),'-. Both isomers are formed in reactions with hydrogen sulfite but only the 0-bonded isomer is formed in sulfite solutions at ambient temperatures. The Raman and Se-77 NMR spectra of the various sulfur-selenium anions formed are given and the parallel with the reactions of selenous acid and thiols is discussed.Key words: selenium, sulfite, selenosulfate, selenotrithionate, Se-77 NMR, Raman spectroscopy, equilibria, aqueous solutions.Resum6 : Le stltnium Cltmentaire se dissout dans une solution de sulfite pour former l'ion sClCnosulfate : Se + SO,'-= S~SO?-. On a d6terminC pour la premikre fois les constantes de formation pour cet Cquilibre, B des temperatures allant de 0 B 35°C. Toutefois, l'ion isomkre thiosCICnate, SS~O,'-, n'est pas produit par la reaction du soufre avec le selenite; l'ion ~ClenosClCnate, se20,'-, ne se forme pas non plus i partir du sClCnium et du sC1tnite. Le sClCnotrithionate se forme rapidement par la rtaction de l'acide sClCneux avec le sulfite et le sulfite d'hydrogkne, suivant I'tquation : HSe0,-+ 3 HSO< = s~(so,),~-+ SO,' -+ 2 H'O. On a observt deux isomkres de l'ion stltnotrithionate par RMN du 7 7~e et par spectroscopie Raman; l'un comporte un 0 lit au Se, Se(oS0,);-, et l'autre comporte un S liC au Se, Se(~0,);-. Les deux isomkres se forment au cours de rCactions avec le sulfite d'hydrogkne; toutefois, B la temptrature ambiante, en solutions dans le sulfite, il ne se forme que l'isomkre comportant une liaison 0 . On rapporte les spectres RMN du 7 7~e des divers anions soufre-sCltnium obtenus et on discute du parallkle qui existe avec les rtactions de I'acide sCltneux et des thiols.

Studies on the interaction of selenite and selenium with sulphur donors. Part 4. Thiosulfate

“…sulfite reaction takes place initially over oxygen (10). he importance of Se in these mechanisms, i.e., the initial coordination of sulfite or thiosulfate to selenium in the three-chalcogen chain of the selenopolythionate ions, seems likely in view of the relative inertness of the central sulphur in trithionate to attack by thiosulfate to form tetrathionate in these studies.…”

“…The selenopentathionate ion in solution exhibits linkage isomerism like that of the selenotrithionate ion but it appears that only SSeS and OSeS linkages are formed for the selenopentathionate, compared to all three possible linkages to selenium in the case of selenotrithionate (10). The compounds isolated from these solutions show only SSeS linkages.…”

“…The Se-77 NMR spectrum of a 1:4:4 molar ratio solution of SeO,lNa,S,O,/HCl (c(Se0,) = 0.5 M), prepared by dropwise addition of a Na,S,O, solution to SeO, in HCI at O°C, exhibits a single chemical shift at 774.3 ppm, which lies in the range of chemical shifts for Se(I1) bound to two sulphur neighbours (10). The Raman spectrum of a solution prepared in the same way but with c(Se0,) = 0.43 M is shown in Fig.…”

“…Although the formation of the selenopentathionate anion and the reaction stoichiometry have been established for reaction [I], spectroscopic methods have not been used and the precise nature of the sulphur oxoanion is not known. Moreover, the possibility of linkage isomerism, like that observed for selenotrithionate ion (10) and for thiosulfatc~metal coordination complexes (1 I), has not been explored for the selenopentathionate ion. For these reasons, we undertook an investigation of reaction [I] by Raman and Se-77 NMR spectroscopy.…”

Redox reaction of aqueous selenite with As-rich pyrite from Jiguanshan ore mine (China): Reaction products and pathway

“…Alternatively, selenite can interact with thiosulfate, leading to the formation of seleno-polythionates, such as selenotrithionate, Se(SO 3 ) 2 2À or selenopentathionate, Se(S 2 O 3 ) 2 2À (Ball and Milne, 1995;Rahim and Milne, 1996). These soluble Se(0) containing species could further decompose with the release of elemental selenium and sulfate, a process known to be catalyzed by thiosulfate.…”