Chemistry:Cobalt(III) chloride

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Cobalt(III) chloride
Names
IUPAC name
Cobalt(III) chloride
Other names
Cobaltic chloride
Cobalt trichloride
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 233-574-8
Properties
CoCl3
Molar mass 165.2913 g/mol (anhydrous)
Melting point Solid decomposes over −60°C
Solubility soluble in ethanol, diethyl ether
Hazards
GHS pictograms GHS06: Toxic
GHS Signal word Danger
H300, H330
P260, P264, P270, P271, P284, P301+310, P304+340, P310, P320, P321, P330, P403+233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Cobalt(III) chloride or cobaltic chloride is an unstable and elusive compound of cobalt and chlorine with formula CoCl3. In this compound, the cobalt atoms have a formal charge of +3.[1]

The compound has been reported to exist in the gas phase at high temperatures, in equilibrium with cobalt(II) chloride and chlorine gas.[2][3] It has also been found to be stable at very low temperatures, dispersed in a frozen argon matrix.[4]

Some articles from the 1920s and 1930s claim the synthesis of bulk amounts of this compound in pure form;[5][6] however, those results do not seem to have been reproduced, or have been attributed to other substances like the hexachlorocobaltate(III) anion CoCl3−6.[1] Those earlier reports claim that it gives green solutions in anhydrous solvents such as ethanol and diethyl ether, and that it is stable only a very low temperatures (below −60 °C).[7]

Structure and properties

The infrared spectrum of the compound in frozen argon indicates that the isolated CoCl3 molecule is planar with D3h symmetry.[4]

A theoretical study of the stability of this and other metal trihalides at 25 °C was published by Nelson and Sharpe in 1966.[8]

Thermodynamic properties for the gas phase have been determined by the Glushko Thermocenter of the Russian Academy of Sciences.[9]

Preparation

Cobalt trichloride was detected in 1952 by Schäfer and Krehl in the gas phase when cobalt(II) chloride CoCl2 is heated in an atmosphere of chlorine Cl2. The trichloride is formed through the equilibrium

2CoCl2 + Cl2 ↔ 2 CoCl3

At 918 K (below the melting point of CoCl2, 999 K), the trichloride was the predominant cobalt species in the vapor, with partial pressure of 0.72 mm Hg versus 0.62 for the dichloride. However, equilibrium shifts to the left at higher temperatures. At 1073 K, the partial pressures were 7.3 and 31.3 mm Hg, respectively.[2][10][3]

Cobalt trichloride, in amounts sufficient to study spectroscopically, was obtained by Green and others in 1983, by sputtering cobalt electrodes with chlorine atoms and trapping the resulting molecules in frozen argon at 14 K.[4]

A report from 1969 claims that treatment of solid cobalt(III) hydroxide CoOOH·H2O with anhydrous ether saturated with HCl at −20 °C produces a green solution (stable at −78 °C) with the characteristic spectrum of CoCl3.[1]

In a 1932 report, the compound was claimed to arise in the electrolysis of cobalt(II) chloride in anhydrous ethanol.[7]

Related compounds

The hexachlorocobaltate(III) anion CoCl3−6 has been identified in preparations of cobalt(III) salts and hydrochloric acid HCl in glacial acetic acid.[1]

In solutions of cobalt(III) salts with chloride ions, the anionic complexes (H2O)5Co(Cl)2+ and (H2O)4(OH)Co(Cl)+ are present.[11]

Trichlorides of cobalt(III) complexed with various ligands, such as organic amines, can be quite stable. In particular, hexamminecobalt(III) chloride Co(NH3)6Cl3 is the archetypal Werner complex and has uses in biological research. Another classical example is tris(ethylenediamine)cobalt(III) chloride Co(H2N–C2H4–NH2)3Cl3.

References

  1. 1.0 1.1 1.2 1.3 Arthur W. Chester, El-Ahmadi Heiba, Ralph M. Dessau, and William J. Koehl Jr. (1969): "The interaction of cobalt(III) with chloride ion in acetic acid". Inorganic and Nuclear Chemistry Letters, volume 5, issue 4, pages 277-283. doi:10.1016/0020-1650(69)80198-4
  2. 2.0 2.1 Harald Schäfer and Kurt Krehl (1952): "Das gasförmige Kobalt(III)‐chlorid und seine thermochemischen Eigenschaften". Zeitschrift für anorganische und allgemeine Chemie, volume 268, issue 1‐2, pages 25-34. doi:10.1002/zaac.19522680105
  3. 3.0 3.1 W. D. Halstead (1975): "A review of saturated vapour pressures and allied data for the principal corrosion products of iron, chromium, nickel and cobalt in flue gases". Corrosion Science, volume 15, issues 6–12, pages 603-625. doi:10.1016/0010-938X(75)90027-X
  4. 4.0 4.1 4.2 David W. Green, Dana P. McDermott, and Adelle Bergman (1983): "Infrared spectra of the matrix-isolated chlorides of iron, cobalt, and nickel." Journal of Molecular Spectroscopy, volume 98, issue 1, pages 111-124. doi:10.1016/0022-2852(83)90206-0
  5. C. Schall and H. Markgraf (1924). Transactions of the American Electrochemical Society, volume 45, page 161.
  6. D. Hibert and C. Duval (1937): Comptes rendues, volume 204, page 780.
  7. 7.0 7.1 C. Schall (1932): "Zur anodischen Oxydation von Co und Ni‐Dichlorid (Nachtrag)." Zeitschrift für Elektrochemie, volume 38, page 27.
  8. P. G. Nelson and A. G. Sharpe (1966): "The variations in the thermal stabilities of the trichlorides, tribromides, and tri-iodides of the metals of the first transition series at 25 °C". Journal of the Chemical Society A: Inorganic, Physical, Theoretical, volume 1966,pages 501-511 doi:10.1039/J19660000501
  9. Scientific Group Thermodata Europe (2001): "Thermodynamic Properties of Compounds, CoCl3 to {[chem|NpCl|3}}". In: Landolt-Börnstein - Group IV Physical Chemistry, Part 3: Compounds from CoCl3g to Ge3N4; volume 19 A3. doi:10.1007/10551582_3 ISBN:978-3-540-66796-4
  10. Harald Schäfer and Günther Breil (1956): "Über die Neigung zur Bildung gasförmiger Trichloride bei den Elementen Cr, Mn, Fe, Co, Ni, untersucht mit der Reaktion MeCl2 gas + 1/2 Cl2 = MeCl3 gas". Zeitschrift für anorganische und allgemeine Chemie, volume 283, issue 1‐6, pages 304-313. doi:10.1002/zaac.19562830130
  11. T. J. Conocchioli, G. H. Nancollas, and N. Sutin (1965): "The kinetics of the formation and dissociation of the monochloro complex of cobalt(III)". Inorganic Chemistry, volume 5, issue 1, pages 1-5. doi:10.1021/ic50035a001