Boron triiodide

Boron triiodide is a chemical compound of boron and iodine with chemical formula BI₃. It has a trigonal planar molecular geometry.

Boron triiodide^[1]

Names
IUPAC name triiodoborane
Identifiers
CAS Number	13517-10-7 N
3D model (JSmol)	Interactive image
ChemSpider	75378 Y
ECHA InfoCard	100.033.492
PubChem CID	83546
RTECS number	ED7400000
CompTox Dashboard (EPA)	DTXSID0065519
InChI InChI=1S/BI3/c2-1(3)4 Y Key: YMEKEHSRPZAOGO-UHFFFAOYSA-N Y InChI=1/BI3/c2-1(3)4 Key: YMEKEHSRPZAOGO-UHFFFAOYAR
SMILES IB(I)I
Properties
Chemical formula	BI3
Molar mass	391.52 g/mol
Appearance	crystalline solid
Density	3.35 g/cm3 (50 °C)
Melting point	49.9 °C (121.8 °F; 323.0 K)
Boiling point	210 °C (410 °F; 483 K)
Solubility in water	soluble,hydrolysis
Solubility	soluble in CCl4, CS2, benzene, chloroform
Dipole moment	0D
Structure
Crystal structure	hexagonal
Thermochemistry
Heat capacity (C)	71 J/mol K
Std molar entropy (S⦵298)	200 J/mol K
Std enthalpy of formation (ΔfH⦵298)	−37.2 kJ/mol
Hazards
NFPA 704 (fire diamond)	3 0 0
Flash point	−18 °C (0 °F; 255 K)
Safety data sheet (SDS)	Sigma-Aldrich
Related compounds
Related compounds	Boron trifluoride Boron trichloride Boron tribromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Preparation

Boron triiodide can be prepared by the reaction of boron with iodine at 209.5 °C or 409.1 °F.^{[citation needed]} It can also be prepared by reacting hydroiodic acid with boron trichloride:

3HI + BCl₃ → BI₃ + 3HCl (reaction requires high temperature)

Another method is by reacting lithium borohydride with iodine. As well as boron triiodide, this reaction also produces lithium iodide, hydrogen and hydrogen iodide:^[2]

3LiBH₄ + 8I₂ → 3LiI + 3BI₃ + 4H₂ + 4HI

Properties

In its pure state, boron triiodide forms colorless, otherwise reddish, shiny, air and hydrolysis-sensitive^[3] crystals, which have a hexagonal crystal structure (a = 699.09 ± 0.02 pm, c = 736.42 ± 0.03 pm, space group P6₃/m (space group no. 176)).^[4] Boron triiodide is a strong Lewis acid and soluble in carbon disulfide.^[2]

Boron triiodide reacts with water and decomposes to boric acid and hydriodic acid:

BI₃ + 3H₂O ⇌ B(OH)₃ + 3HI

Its dielectric constant is 5.38 and its heat of vaporization is 40.5 kJ/mol. At extremely high pressures, BI₃ becomes metallic at ~23 GPa and is a superconductor above ~27 GPa.^[5]

Applications

Boron triiodide can be used to produce other chemical compounds and as a catalyst (for example in coal liquefaction).^[6]