Cobalt(II) bromide
4.svg.png) Structure of cobalt(II) bromide tetrahydrate
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-bromide-xtal-packing-3D-bs-17.png) Crystal structure of cobalt(II) bromide
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_bromide.jpg) Anhydrous cobalt(II) bromide in a vial
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| Identifiers | |
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CAS Number
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.029.242 |
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PubChem CID
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| UNII | |
| UN number | 3077 |
CompTox Dashboard (EPA)
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InChI
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SMILES
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| Properties | |
Chemical formula
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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 (1,252 °F; 951 K) (anhydrous)[1][2] 47 °C (hexahydrate) |
Solubility in water
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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 |
Magnetic susceptibility (χ)
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+13000·10−6 cm3/mol |
| Structure | |
Crystal structure
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Rhombohedral, hP3, SpaceGroup = P-3m1, No. 164 |
Coordination geometry
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octahedral |
| Hazards | |
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Pictograms
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Signal word
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Danger |
Hazard statements
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H302, H312, H315, H317, H319, H332, H334, H335, H350 |
Precautionary statements
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P201, P202, P261, P264, P270, P271, P272, P280, P281, P285, P301+P312, P302+P352, P304+P312, P304+P340, P304+P341, P305+P351+P338, P308+P313, P312, P321, P322, P330, P332+P313, P333+P313, P337+P313, P342+P311, P362, P363, P403+P233, P405, P501 |
| NFPA 704 (fire diamond) | 
2
0
1 |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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406 mg/kg (oral, rat) |
| Safety data sheet (SDS) | Fisher Scientific |
| Related compounds | |
Other anions
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cobalt(II) fluoride cobalt(II) chloride cobalt(II) iodide |
Other cations
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iron(II) bromide nickel(II) bromide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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Cobalt(II) bromide refers to inorganic compounds with the formula CoBr2·(H2O)n. The anhydrous form (n = 0) is a green solid and the hexahydrate (n = 6) is a red solid.[3] These compounds find some use as catalysts.[4]
Structure
The anhydrous compound has a cadmium iodide structure. The tetrahydrate is molecular, with the formula trans-[CoBr2(H2O)4].[5]
Preparation and reactions
Cobalt(II) bromide form by treating an aqueous suspension of cobalt(II) carbonate with hydrobromic acid according to the following idealized equation:[3]
- CoCO3 + 2 HBr + 5 H2O → CoBr2(H2O)6 + CO2
Anhydrous cobalt(II) bromide is hygroscopic. Air exposure eventually forms the hexahydrate in air,[6] which appears as red-purple crystals. The hexahydrate loses four water of crystallization molecules at 100 °C forming the dihydrate:
- CoBr2·6H2O → CoBr2·2H2O + 4 H2O
The anhydrous compound forms by heating any of the hydrates to >150 °C in a vacuum:
- CoBr2(H2O)6 → CoBr2 + 6 H2O
The resulting solid can be purified by vacuum sublimation at > 500 °C.[3]
Further heating to 130 °C produces the anhydrous form:
- CoBr2·2H2O → CoBr2 + 2 H2O
At higher temperatures, cobalt(II) bromide reacts with oxygen, forming cobalt(II,III) oxide and bromine vapor.
The coordination compound bromopentaamminecobalt(III) bromide is prepared by oxidation of an aqueous solution of cobalt(II) bromide and ammonia.[7]
- 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.[8]
Safety
Exposure to large amounts of cobalt(II) can cause cobalt poisoning.[9] Bromide is also mildly toxic.
References
- ^ Cobalt Bromide Supplier & Tech Info American Elements
- ^ WebElements Periodic Table of the Elements
- ^ a b c O. Glemser (1963). "Cobalt(II) bromide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. p. 1517.
- ^ Le Gall, Erwan; Martens, Thierry (2012). "Multicomponent Synthesis of Tertiary Diarylmethylamines: 1-((4-Fluorophenyl)(4-methoxyphenyl)methyl)piperidine". Organic Syntheses. 89: 283. doi:10.15227/orgsyn.089.0283.
- ^ Waizumi, Kenji; Masuda, Hideki; Ohtaki, Hitoshi (1992). "X-ray Structural Studies of FeBr2·4H2O, CoBr2·4H2O, NiCl2·4H2O and CuBr2·4H2O. Cis/Trans Selectivity in Transition Metal(II) Dihalide Tetrahydrate". Inorganica Chimica Acta. 192 (2): 173–181. doi:10.1016/S0020-1693(00)80756-2.
- ^ Perry, Dale L. (2011). Handbook of Inorganic Compounds (2nd ed.). Boca Raton: Taylor & Francis. p. 130. ISBN 978-1-4398-1461-1. OCLC 587104373.
- ^ Diehl, Harvey; Clark, Helen; Willard, H. H.; Bailar, John C. (1939). "Bromopentamminocobalti Bromide". Inorganic Syntheses. Vol. 1. p. 186. doi:10.1002/9780470132326.ch66. ISBN 978-0-470-13232-6.
{{cite book}}: ISBN / Date incompatibility (help) - ^ Gund, Tamara M.; Thielecke, Wilfried; R. Schleyer, Paul v. (1973). "Diamantane: Pentacyclo[7.3.1.14,12.02,7.06,11]Tetradecane". Organic Syntheses. 53: 30. doi:10.15227/orgsyn.053.0030.
- ^ "Cobalt Bromide (OUS)" (PDF). Archived from the original (PDF) on 2007-06-25. Retrieved 2008-04-10.