Boron triiodide
Boron triiodide is a chemical compound of boron and iodine with chemical formula BI3. It has a trigonal planar molecular geometry.
Preparation
Boron triiodide can be prepared by the reaction of boron with iodine at 209.5 °C or 409.1 °F.It can also be prepared by reacting hydroiodic acid with boron trichloride:
Another method is by reacting lithium borohydride with iodine. As well as boron triiodide, this reaction also produces lithium iodide, hydrogen and hydrogen iodide:
Properties
In its pure state, boron triiodide forms colorless, otherwise reddish, shiny, air and hydrolysis-sensitive crystals, which have a hexagonal crystal structure. Boron triiodide is a strong Lewis acid and soluble in carbon disulfide.Boron triiodide reacts with water and decomposes to boric acid and hydriodic acid:
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.