Chromium(II) sulfate

Chromium(II) sulfate

Crystalline sample wet with ethanol

Structure of chromium(II) sulfate pentahydrate (CrSO4·5H2O)
  Chromium, Cr
  Sulfur, S
  Oxygen, O
  Hydrogen, H
Names
IUPAC name
Chromium(2+) sulfate
Other names
chromous sulfate, chromous sulphate
Identifiers
3D model (JSmol)
ChemSpider
UNII
  • Key: RYPRIXSYXLDSOA-UHFFFAOYSA-L
  • Key: RYPRIXSYXLDSOA-NUQVWONBAQ
  • anhydrous: [Cr+2].[O-]S(=O)(=O)[O-]
  • pentahydrate: [OH2+][Cr-3]([OH2+])([OH2+])([OH2+])O(S(=O)(=O)[O-]).O
Properties
CrSO4 (anhydrous)
CrSO4·5H2O (pentahydrate)
Molar mass 148.05 g/mol (anhydrous)
238.13 g/mol (pentahydrate)
Appearance Blue crystalline solid (pentahydrate)
21 g/(100 mL) (0°C, pentahydrate)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Chromium(II) sulfate is an inorganic compound with the chemical formula CrSO4. It often comes as hydrates CrSO4·nH2O. Several hydrated salts are known. The pentahydrate CrSO4·5H2O is a blue solid that dissolves readily in water. Solutions of chromium(II) are easily oxidized by air to Cr(III) species. Solutions of Cr(II) are used as specialized reducing agents of value in organic synthesis.[1]

The salt is produced by treating chromium metal with aqueous sulfuric acid:[2]

Cr + H2SO4 + 5 H2O → CrSO4·5H2O + H2

It can be produced through the reaction of sulfate salts and chromium(II) acetate[3] or, for in situ use, the reduction of chromium(III) sulfate with zinc.[1]

Structure

In aqueous solutions chromium(II) sulfate forms metal aquo complexes, presumably with six water ligands. The structures of the crystalline salts are similar to the corresponding hydrates of copper(II) sulfate: pentahydrate, trihydrate, monohydrate, and anhydrous derivatives of chromous sulfate are known. In all of these compounds, the Cr(II) centre adopts octahedral coordination geometry, being coordinated to six oxygen centers provided by a combination of water and sulfate ligands.[4][5]

References

  1. ^ a b A. Zurqiyah and C. E. Castro "Reduction of Conjugated Alkenes With Chromium(II) Sulfate: Diethyl Succinate" Organic Syntheses, Vol. 49, p.98 (1969).doi:10.15227/orgsyn.049.0098
  2. ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 2. p. 1365.
  3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. ^ Hitchman, Michael A.; Lichon, Michael; McDonald, Robbie G.; Smith, Peter W.; Stranger, Robert (1987). "Crystal and Molecular Structure of Chromium(II) Sulfate Pentahydrate and Single-Crystal Electronic Spectra and Bonding of CrSO4·5 H2O, Copper Sulfate Pentahydrate and CuSO4·5 D2O". Journal of the Chemical Society, Dalton Transactions: 1817–22. doi:10.1039/DT9870001817.
  5. ^ Dahmen, T.; Glaum, R.; Schmidt, G.; Gruehn, R. (1990). "Zur Darstellung und Kristallstruktur von CrSO4·3H2O" [Preparation and Crystal Structure of Chromium(2+) Sulfate Trihydrate]. Zeitschrift für Anorganische und Allgemeine Chemie. 586: 141–8. doi:10.1002/zaac.19905860119.