Cobalt(II) iodide
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| Names | |
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| IUPAC name
Cobalt(II) iodide
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| Other names
cobaltous iodide, cobalt diiodide
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| Identifiers | |
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.035.697 |
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PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| CoI2 | |
| Molar mass | 312.7421 g/mol (anhydrous) 420.83 g/mol (hexahydrate) |
| Appearance | α-form: black hexagonal crystal β-form: yellow powder |
| Density | α-form: 5.584 g/cm3 β-form: 5.45 g/cm3 hexahydrate: 2.79 g/cm3 |
| Melting point | α-form: 515-520 °C under vacuum β-form: converts to α-form at 400 °C |
| Boiling point | 570 °C (1,058 °F; 843 K) |
| 67.0 g/100 mL[1] | |
| +10,760·10−6 cm3/mol | |
| Hazards | |
| GHS labelling: | |
 
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| Warning | |
| H302, H312, H315, H319, H332, H335 | |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Other anions
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Cobalt(II) fluoride Cobalt(II) chloride Cobalt(II) bromide |
Other cations
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Nickel(II) iodide Copper(I) iodide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cobalt(II) iodide or cobaltous iodide are the inorganic compounds with the formula CoI2 and the hexahydrate CoI2(H2O)6. These salts are the principal iodides of cobalt.[2]
Synthesis
[edit]Cobalt(II) iodide is prepared by treating cobalt powder with gaseous hydrogen iodide.[2] The hydrated form CoI2.6H2O can be prepared by the reaction of cobalt(II) oxide (or related cobalt compounds) with hydroiodic acid.
Cobalt(II) iodide crystallizes in two polymorphs, the α- and β-forms. The α-polymorph consists of black hexagonal crystals, which turn dark green when exposed to air. Under a vacuum at 500 °C, samples of α-CoI2 sublime, yielding the β-polymorph as a yellow crystals. β-CoI2 also readily absorbs moisture from the air, converting into green hydrate. At 400 °C, β-CoI2 reverts to the α-form.[2]
Structures
[edit]The anhydrous salts adopt the cadmium halide structures.
The hexaaquo salt consists of separated [Co(H2O)6]2+ and iodide ions as verified crystallographically.[3][4]
Reactions and applications
[edit]Anhydrous cobalt(II) iodide is sometimes used to test for the presence of water in various solvents.[5]
Cobalt(II) iodide is used as a catalyst, e.g. in carbonylations. It catalyzes the reaction of diketene with Grignard reagents, useful for the synthesis of terpenoids[6]
References
[edit]- ^ Perry, Dale L.; Phillips, Sidney L. (1995), Handbook of Inorganic Compounds, San Diego: CRC Press, pp. 127–8, ISBN 0-8493-8671-3, retrieved 2008-06-03
- ^ a b c O. Glemser "Cobalt, Nickel" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1518.
- ^ “Structure Cristalline et Expansion Thermique de L’Iodure de Nickel Hexahydrate“ (Crystal structure and thermal expansion of nickel(II) iodide hexahydrate) Louër, Michele; Grandjean, Daniel; Weigel, Dominique Journal of Solid State Chemistry (1973), 7(2), 222-8. doi:10.1016/0022-4596(73)90157-6
- ^ "The crystal structure of the crystalline hydrates of transition metal salts. The structure of CoI2·6H2O" Shchukarev, S. A.; Stroganov, E. V.; Andreev, S. N.; Purvinskii, O. F. Zhurnal Strukturnoi Khimii 1963, vol. 4, pp. 63-6.<!no doi in CAS-->
- ^ Armarego, Wilfred L. F.; Chai, Christina L. L. (2003), Purification of Laboratory Chemicals, Butterworth-Heinemann, p. 26, ISBN 0-7506-7571-3, retrieved 2008-06-03
- ^ Agreda, V. H.; Zoeller, Joseph R. (1992), Acetic Acid and Its Derivatives, CRC Press, p. 74, ISBN 0-8247-8792-7, retrieved 2008-06-03