Germanium dichloride

Germanium dichloride is a chemical compound of germanium and chlorine with the formula GeCl2. It is a yellow solid. Germanium dichloride is an example of a compound featuring germanium in the +2 oxidation state.

Preparation
Solid germanium dichloride can be produced by comproportionation by passing germanium tetrachloride, GeCl4, over germanium metal at 300 °C and reduced pressure (0.1 mmHg).
 * GeCl4 + Ge -> 2 GeCl2

Germanium dichloride is also formed from the decomposition of trichlorogermane, GeHCl3, at 70 °C. Trichlorogermane is generated when germanium reacts with hydrogen chloride. This reaction involves dehydrohalogenation.
 * GeHCl3 -> GeCl2 + HCl

Another route to germanium dichloride is the reduction of germanium tetrachloride with hydrogen at 800 °C.
 * GeCl4 + H2 -> GeCl2 + 2HCl

Reactions
GeCl2 is hydrolysed to give yellow germanium(II) hydroxide, which on warming gives brown germanium monoxide:
 * GeCl2 + 2 H2O ⇌ Ge(OH)2(s) + 2 HCl
 * Ge(OH)2 -> GeO + H2O

Alkalizing a solution containing germanium(II) ions:
 * Ge(2+) + 2 OH- → Ge(OH)2

Germanium oxides and hydroxides are amphoteric. Solutions of GeCl2 in HCl are strongly reducing. With chloride ion, ionic compounds containing the pyramidal GeCl3- ion have been characterised, for example With rubidium and caesium chloride compounds, e.g. RbGeCl3 are produced; these have distorted perovskite structures.

Germanium dichloride reacts with tetraethylammonium chloride to give the trichlorogermanate:
 * GeCl2 + Et4NCl ->  Et4NGeCl3

Dichlorogermylene
Molecular GeCl2 is often called dichlorogermylene, highlighting its resemblance to a carbene. The structure of gas-phase molecular GeCl2 shows that it is a bent molecule, as predicted by VSEPR theory. The dioxane complex, GeCl2*dioxane, has been used as a source of molecular GeCl2 for reaction syntheses, as has the in situ reaction of GeCl4 and Ge metal. GeCl2 is quite reactive and inserts into many types of chemical bonds. Usually, germanium dichloride is generated from germanium dichloride dioxane.