Germanium(II) iodide

Germanium(II) iodide is an iodide of germanium, with the chemical formula of GeI2.

Preparation
Germanium(II) iodide can be produced by reacting germanium(IV) iodide with hydriodic acid and hypophosphorous acid and water:


 * GeI4 + H2O + H3PO2 -> GeI2 + H3PO3 + 2 HI

It can also be formed by the reaction of germanium monosulfide or germanium monoxide and hydrogen iodide.


 * GeO + 2 HI -> GeI2 + H2O


 * GeS + 2 HI -> GeI2 + H2S}

It can also be produced from the direct reaction of germanium and iodine at 200 – 400 °C:


 * Ge + I2 -> GeI2

Germanium(II) iodide can also be formed from the decomposition of HGeI3, which can be prepared by reacting HGeCl3 with hydroiodic acid:


 * HGeCl3 + 3 HI -> HGeI3 + HCl


 * HGeI3 -> GeI2 + HI

Properties
Germanium(II) iodide is a yellow crystal that slowly hydrolyzes into germanium(II) hydroxide in the presence of moisture. It is insoluble in hydrocarbons and slightly soluble in chloroform and carbon tetrachloride. It has a cadmium iodide structure with lattice parameters a = 413 pm and c = 679 pm. It disproportionates to germanium and germanium tetraiodide at 550 °C.

Applications
Germanium(II) iodide can react with carbene to form stable compounds. It is also used in the electronics industry to produce germanium layers epitaxially through disproportionation reactions.