4.svg) Structure of cobalt(II) bromide tetrahydrate | |
-bromide-xtal-packing-3D-bs-17.png) Crystal structure of cobalt(II) bromide | |
_bromide.jpg) Anhydrous cobalt(II) bromide in a vial | |
| Identifiers | |
|---|---|
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.029.242 |
| EC Number |
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| RTECS number |
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| UNII | |
| UN number | 3077 |
| |
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| Properties | |
| 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) 47 °C (hexahydrate) |
| 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 inmethyl acetate,ether,alcohol,acetone |
| +13000·10−6 cm3/mol | |
| Structure | |
| Rhombohedral,hP3, SpaceGroup = P-3m1, No. 164 | |
| octahedral | |
| Hazards | |
| GHS labelling: | |
   | |
| Danger | |
| H302,H312,H315,H317,H319,H332,H334,H335,H350 | |
| 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) | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 406 mg/kg (oral, rat) |
| Safety data sheet (SDS) | Fisher Scientific |
| Related compounds | |
Otheranions | cobalt(II) fluoride cobalt(II) chloride cobalt(II) iodide |
Othercations | iron(II) bromide nickel(II) bromide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Cobalt(II) bromide (CoBr2) is an inorganic compound. In its anhydrous form, it is a green solid that is soluble in water, used primarily as acatalyst in some processes.
Whenanhydrous, cobalt(II) bromide appears as green crystals. It ishygroscopic and eventually forms the hexahydrate in air,[1] which appears as red-purple crystals. The hexahydrate loses four water of crystallization molecules at 100 °C forming the dihydrate:
Further heating to 130 °C produces the anhydrous form:
The anhydrous form melts at 678 °C.[2][3] At higher temperatures, cobalt(II) bromide reacts withoxygen, formingcobalt(II,III) oxide andbromine vapor.
The tetrahydrate is molecular, with the formulatrans-[CoBr2(H2O)4].[4]
Cobalt(II) bromide can be prepared as a hydrate by the reaction ofcobalt hydroxide withhydrobromic acid:
The classicalcoordination compoundbromopentaamminecobalt(III) bromide is prepared by oxidation of an aqueous solution of cobalt(II) bromide and ammonia.[5]
Triphenylphosphine complexes of cobalt(II) bromide have been used as acatalysts in organic synthesis.[citation needed]
Exposure to large amounts of cobalt(II) can causecobalt poisoning.[6] Bromide is also mildly toxic.
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