Cobalt(II) bromide
| Cobalt(II) bromide | |
|---|---|
 | |
| Identifiers | |
| CAS number | 7789-43-7  |
| PubChem | 24610 |
| ChemSpider | 23012 |
| RTECS number | GF9595000 |
| Jmol-3D images | {{#if:[Co](Br)Br|Image 1 |
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| Properties | |
| Molecular formula | CoBr2, CoBr2.6H2O, CoBr2.2H2O |
| Molar mass | 218.7412 g/mol (anhydrous) 326.74 g/mol (hexahydrate) |
| Appearance | Bright green crystals (anhydrous) Red-purple crystals (hexahydrate) |
| Density | 4.909 g/cm3 (anhydrous) 2.46 g/cm3 (hexahydrate) |
| Melting point | 678 °C (anhydrous) 47 °C (hexahydrate) |
| Solubility in water | anhydrous: 66.7 g/100 mL (59 °C) 68.1 g/100 mL (97 °C) hexahydrate: 113.2 g/100 mL (20 °C) |
| Solubility | 77.1 g/100 mL (ethanol, 20 °C) 58.6 g/100 mL (methanol, 30 °C) soluble in methyl acetate, ether, alcohol, acetone |
| Structure | |
| Crystal structure | Rhombohedral, hP3, SpaceGroup = P-3m1, No. 164 |
| Coordination geometry |
octahedral |
| Hazards | |
| MSDS | Fisher Scientific |
| EU Index | Not listed |
| R-phrases | R36, R37, R38 |
| S-phrases | S26, S37, S39, S45, S28A |
| NFPA 704 |
 0
2
1
|
| Flash point | Non-flammable |
| LD50 | 406 mg/kg (oral, rat) |
| Related compounds | |
| Other anions | cobalt(II) fluoride cobalt(II) chloride cobalt(II) iodide |
| Other cations | iron(II) bromide nickel(II) bromide |
(verify) (what is: / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | |
| Infobox references | |
Cobalt(II) bromide (CoBr2) is an inorganic compound. It is a red solid that is soluble in water, used primarily as a catalyst in some processes.
Properties
When anhydrous, cobalt(II) bromide appears as green crystals. The hexahydrate loses four waters of crystallization molecules at 100 °C forming the dihydrate:
- CoBr2.6H2O → CoBr2.2H2O + 4 H2O
Further heating to 130 °C produces the anhydrous form:
- CoBr2.4H2O → CoBr2
The anhydrous form melts at 678 °C.[1][2] At higher temperatures, cobalt(II) bromide reacts with oxygen, forming cobalt(II,III) oxide and bromine vapor.
Preparation
Cobalt(II) bromide can be prepared as a hydrate by the reaction of cobalt hydroxide with hydrobromic acid:
- Co(OH)2(s) + 2HBr(aq) → CoBr2.6H2O(aq)
Anhydrous cobalt(II) bromide may be prepared through the direct reaction of elemental cobalt and liquid bromine.[3][4][5]
Reactions and uses
The classical coordination compound bromopentaamminecobalt(III) bromide is prepared by oxidation of a solution of cobalt(II) bromide in aqueous ammonia.[6]
- 2 CoBr2 + 8 NH3 + 2 NH4Br + H2O2 → 2 [Co(NH3)5Br]Br2 + 2 H2O
Triphenylphosphine complexes of cobalt(II) bromide have been used as a catalysts in organic synthesis.
Safety
Exposure to large amounts of cobalt(II) can cause cobalt poisoning.[7] Bromide is also mildly toxic.
References
- ↑ Cobalt Bromide Supplier & Tech Info American Elements
- ↑ WebElements Periodic Table of the Elements
- ↑ WebElements Periodic Table of the Elements | Cobalt | Essential information
- ↑ Chemical Properties and Reaction Tendencies
- ↑ Pilgaard Solutions: Cobalt
- ↑ Diehl, Harvey; Clark, Helen; Willard, H. H.; Bailar, John C. (1939). "Bromopentamminocobalti Bromide". Inorganic Syntheses. Inorganic Syntheses 1. p. 186. doi:10.1002/9780470132326.ch66. ISBN 9780470132326.
- ↑ http://www.chrismanual.com/C/COB.pdf
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