Английская Википедия:Cobalt(II) bromide
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 a catalyst in some processes.
Properties
When anhydrous, cobalt(II) bromide appears as green crystals. It is hygroscopic 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:
- CoBr2·6H2O → CoBr2·2H2O + 4 H2O
Further heating to 130 °C produces the anhydrous form:
- CoBr2·2H2O → CoBr2 + 2 H2O
The anhydrous form melts at 678 °C.[2][3] At higher temperatures, cobalt(II) bromide reacts with oxygen, forming cobalt(II,III) oxide and bromine vapor.
The tetrahydrate is molecular, with the formula trans-[CoBr2(H2O)4].[4]
Preparation and reactions
Cobalt(II) bromide can be prepared as a hydrate by the reaction of cobalt hydroxide with hydrobromic acid:
- Co(OH)2 + 2HBr → CoBr2·6H2O
The classical coordination compound bromopentaamminecobalt(III) bromide is prepared by oxidation of an aqueous solution of cobalt(II) bromide and ammonia.[5]
- 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.Шаблон:Cn
Safety
Exposure to large amounts of cobalt(II) can cause cobalt poisoning.[6] Bromide is also mildly toxic.
References
Шаблон:Reflist Шаблон:Cobalt compounds Шаблон:Bromine compounds
