Gallium(III) bromide

Gallium(III) bromide (dimer)

Names
Other names gallium tribromide
Identifiers
CAS Number	13450-88-9 N
3D model (JSmol)	Interactive image
ChemSpider	75315 Y
ECHA InfoCard	100.033.267
PubChem CID	83477
InChI InChI=1S/3BrH.Ga/h3*1H;/q;;;+3/p-3 Y Key: SRVXDMYFQIODQI-UHFFFAOYSA-K Y InChI=1/3BrH.Ga/h3*1H;/q;;;+3/p-3 Key: SRVXDMYFQIODQI-DFZHHIFOAJ
SMILES Br[Ga](Br)Br
Properties
Chemical formula	GaBr3
Molar mass	309.435 g/mol
Appearance	white powder
Density	3.69 g/cm3
Melting point	121.5 °C (250.7 °F; 394.6 K)
Boiling point	278.8 °C (533.8 °F; 552.0 K)
Solubility in water	soluble
Hazards
EU classification (DSD) (outdated)	not listed
NFPA 704	0 4 0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Gallium(III) bromide (GaBr₃) is a chemical compound, and one of four Gallium trihalides.

Gallium(III) Tribromide is, at room temperature and atmospheric pressure, a white, crystalline powder which reacts favorably and exothermically with water. Solid gallium tribromide is stable at room temperature and can be found primarily in its dimeric form. GaBr₃ can form an intermediate halide, Ga₂Br_7; however, this is not as common as with GaCl₃. It is a member of the Gallium trihalide group and is similar to GaCl₃, and GaI₃, but not GaF₃, in its preparation and uses. GaBr₃ is a milder Lewis acid than AlBr₃, and has more versatile chemistry due to the comparative ease of reducing Gallium, but is more reactive than GaCl₃.

GaBr₃ is similar spectroscopically to Aluminum, Indium, and Thallium trihalides excluding trifluorides.

One method of preparing GaBr₃ is to heat elemental gallium in the presence of bromine liquid under vacuum. Following the highly exothermic reaction, the mixture is allowed to rest and then subjected to various purifying steps. This method from the turn of the twentieth century remains a useful way of preparing GaBr_3. Historically Gallium was obtained by electrolysis of its hydroxide in KOH solution, however today it is obtained as a byproduct of Aluminum and Zinc production.

GaBr₃ can be synthesized by exposing Ga(s) to Br(g) in a water, oxygen, organic, and grease-free environment. The result is a gas which must be crystallized in order to form the GaBr₃ solid purchased by laboratories. Below is the mechanism:

Ga(s) + 3Br(l) ⟶ GaBr₃(g)

The GaBr₃ monomer has trigonal planar geometry, but when it forms the dimer Ga₂Br₆ the geometry around the Gallium center distorts to become roughly tetrahedral. As a solid, GaBr₃ forms a monoclinic crystalline structure with a unit cell volume of 524.16ų. Additional specifications for this unit cell are as follows: A=8.87Å, B=5.64Å, C=11.01Å, α=90˚, β=107.81˚, γ=90˚

Gallium is the lightest Group 13 metal with a filled d-shell, and has an electronic configuration of (Ar 3d10 4s2 4p1) below the valence electrons that could take part in d-π bonding with ligands. The somewhat high oxidation state of Ga in Ga(III)Br₃, low electronegativity, and high polarizability allow GaBr₃ to behave as a "Soft Acid" in terms of the Hard-Soft-Acid-Base (HSAB) theory. The Lewis acidity of all the Gallium Trihalides, GaBr₃ included, has been extensively studied thermodynamically, and the basicity of GaBr₃ has been established with a number of donors.