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| Names | |
|---|---|
| IUPAC name Cobalt(II) iodide | |
| Other names cobaltous iodide, cobalt diiodide | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.035.697 |
| EC Number |
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| UNII | |
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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 | |
Otheranions | Cobalt(II) fluoride Cobalt(II) chloride Cobalt(II) bromide |
Othercations | Nickel(II) iodide Copper(I) iodide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Cobalt(II) iodide orcobaltous iodide are theinorganic compounds with theformulaCoI2 and thehexahydrate CoI2(H2O)6. These salts are the principal iodides of cobalt.[2]
Cobalt(II) iodide is prepared by treating cobalt powder withgaseoushydrogen iodide[2] The hydrated form CoI2.6H2O can be prepared by the reaction ofcobalt(II) oxide (or related cobalt compounds) withhydroiodic acid.
Cobalt(II) iodide crystallizes in twopolymorphs, 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. 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]
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. incarbonylations. It catalyzes the reaction ofdiketene withGrignard reagents, useful for the synthesis ofterpenoids[6]
