Beryllium iodide is an inorganic compound with the chemical formula . It is a hygroscopic white solid. The cation, which is relevant to salt-like BeI2, is characterized by the highest known charge density (Z/r = 6.45), making it one of the hardest cations and a very strong Lewis acid.
Beryllium iodide can be prepared by reacting beryllium metal with elemental iodine at temperatures of 500 °C to 700 °C:
When the oxidation is conducted on an ether suspension of elemental Be, one obtains colorless dietherate:[1]
The same dietherate is obtained by suspending beryllium iodide in diethyl ether:[1]
This ether ligands in can be displaced by other Lewis bases.
Beryllium iodide reacts with fluorine giving beryllium fluoride and fluorides of iodine, with chlorine giving beryllium chloride, and with bromine giving beryllium bromide.
Two forms (polymorphs) of are known. Both structures consist tetrahedral centers interconnected by doubly bridging iodide ligands. One form consist of edge-sharing polytetrahedra. The other form resembles zinc iodide with interconnected adamantane-like cages.[2]
Beryllium iodide can be used in the preparation of high-purity beryllium by the decomposition of the compound on a hot tungsten filament.