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Research article - Peer-reviewed, 2014

Speciation and structure of tin(II) in hyper-alkaline aqueous solution

Bajnoczi, Eva G.; Czegledi, Eszter; Kuzmann, Erno; Homonnay, Zoltan; Balint, Szabolcs; Dombi, Gyoergy; Forgo, Peter; Berkesi, Otto; Painko, Istvan; Peintler, Gabor; Sipos, Pal; Persson, Ingmar


The identity of the predominating tin(II)-hydroxide complex formed in hyper-alkaline aqueous solutions (0.2 <= C-NaOH <= 12 mol dm(-3)) is determined by potentiometric titrations, Raman, Mossbauer and XANES spectroscopy, supplemented by quantum chemical calculations. Thermodynamic studies using a H-2/Pt electrode up to free hydroxide concentrations of 1 mol dm(-3) showed the presence of a single monomeric complex with a tin(II) : hydroxide ratio of 1 : 3. This observation together with Raman and Mossbauer spectroscopic measurements supplemented by quantum mechanical calculations proved that the predominating complex is [Sn(OH)(3)](-), and that the presence of the other possible complex, [SnO(OH)](-), could not be proven with either experiments or simulations. The structure of the trihydroxidostannate(II) complex, [Sn(OH)(3)](-), was determined by EXAFS and was found to be independent of the applied hydroxide and tin(II) concentrations. The mean Sn-O bond distance is short, 2.078 angstrom, and in very good agreement with the only structure reported in the solid state. It is also shown that at pH values above 13 the speciation of the predominant trihydroxidostannate(II) complex is not affected by the presence of high concentrations of chloride ions.


Hyper-alkaline aqueous solution, tin(II), speciation, structure

Published in

Dalton Transactions
2014, volume: 43, number: 48, pages: 17971–17979

Authors' information

Bajnóczi, Éva G. (Bajnóczi, Éva G.)
University of Szeged
Sipos, Pál
University of Szeged
Swedish University of Agricultural Sciences, The Department of Chemistry and Biotechnology

UKÄ Subject classification

Inorganic Chemistry

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