Bismuth tribromide is an inorganic compound of bismuth and bromine with the chemical formula BiBr3.

Preparation

It may be formed by the reaction of bismuth oxide and hydrobromic acid.[1]

Bi2O3 + 6 HBr ⇌ 2 BiBr3 + 3 H2O

Bismuth tribromide can also be produced by the direct oxidation of bismuth in bromine.[1]

2 Bi + 3 Br2 → 2 BiBr3

Structure

Bismuth tribromide adopts two different structures in the solid state: a low-temperature polymorph α-BiBr3 that is stable below 158 °C and a high-temperature polymorph β-BiBr3 that is stable above this temperature. Both polymorphs are monoclinic, but α-BiBr3 is in space group P21/a whereas β-BiBr3 is in C2/m. α-BiBr3 consists of pyramidal molecules whereas β-BiBr3 is polymeric and adopts the AlCl3 structure. BiBr3 is the only group 15 trihalide that can adopt both molecular and polymeric structures.[3]

Reactivity

Bismuth bromide is highly water-soluble. It is a Lewis acid and accepts bromide ions to form monomeric and oligomeric anionic complexes (bromobismuthates), e.g. [BiBr6]3−, [Bi2Br10]4−, (BiBr−
4)n and (BiBr2−
5)n.[4]

References

  1. ^ a b c d e f g Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 558–561. ISBN 978-0-08-037941-8.
  2. ^ "Sigma-Aldrich: 654981 Bismuth(III) bromide anhydrous, powder, 99.999% trace metals basis". Archived from the original on 2012-02-11.
  3. ^ von Benda, Heike (1980). "Zur Polymorphie des Wismuttribromids". Zeitschrift für Kristallographie - Crystalline Materials. 151 (1–4): 271–286. doi:10.1524/zkri.1980.151.14.271. S2CID 96552131.
  4. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 564–568. ISBN 978-0-08-037941-8.