Digermane is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

with the chemical formula Ge₂H₆. One of the few hydrides of

germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors ...

, it is a colourless liquid. Its molecular geometry is similar to

ethane Ethane ( , ) is an organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petroc ...

Synthesis

Digermane was first synthesized and examined in 1924 by Dennis, Corey, and Moore. Their method involves the hydrolysis of magnesium germanide using hydrochloric acid. Many of the properties of digermane and trigermane were determined in the following decade using electron diffraction studies. Further considerations of the compound involved examinations of various reactions such as pyrolysis and oxidation. Digermane is produced together with

germane Germane is the chemical compound with the formula Ge H4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is ...

by the reduction of

germanium dioxide Germanium dioxide, also called germanium(IV) oxide, germania, and salt of germanium, is an inorganic compound with the chemical formula Ge O2. It is the main commercial source of germanium. It also forms as a passivation layer on pure germaniu ...

with

sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula Na BH4. This white solid, usually encountered as an aqueous basic solution, is a reducing agent that finds applica ...

. Although the major product is

, a quantifiable amount of digermane is produced in addition to traces of trigermane. It also arises by the

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysi ...

of magnesium-germanium alloys.

Reactions

The reactions of digermane exhibit some differences between analogous compounds of the Group 14 elements carbon and silicon. However, there are still some similarities seen, especially in regards to pyrolysis reactions. The

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

of digermane takes place at lower temperatures than monogermane. The product of the reaction, germanium oxide, has been shown to act in turn as a catalyst of the reaction. This exemplifies a fundamental difference between germanium and the other Group 14 elements carbon and silicon (carbon dioxide and silicon dioxide do not exhibit the same catalytic properties). 2Ge₂H₆+ 7O₂ → 4GeO₂ + 6H₂O In liquid ammonia, digermane undergoes

disproportionation In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. More generally, the term can ...

. Ammonia acts as a weakly basic catalyst. Products of the reaction are hydrogen, germane, and a solid polymeric germanium hydride.

Pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements '' ...

of digermane is proposed to follow multiple steps: :Ge₂H₆→ 2GeH₃ :GeH₃ + Ge₂H₆→ GeH₄ + Ge₂H₅ :Ge₂H₅→ GeH₂ + GeH₃ :GeH₂ → Ge + H₂ :2GeH₂ → GeH₄ + Ge :nGeH₂ → (GeH₂)_n This pyrolysis has been found to be more endothermic than the pyrolysis of disilane. This difference is attributed to the greater strength of the Ge-H bond vs the Si-H bond. As seen in the last reaction of the mechanism above, pyrolysis of digermane may induce polymerization of the GeH₂group, where GeH₃ acts as a chain propagator and molecular hydrogen gas is released. The dehydrogenation of digermane on gold leads to the formation of germanium

nanowires A nanowire is a nanostructure in the form of a wire with the diameter of the order of a nanometre (10−9 metres). More generally, nanowires can be defined as structures that have a thickness or diameter constrained to tens of nanometers or less ...

. Digermane is a precursor to Ge₂H₅ECF₃, where E is either sulfur or selenium. These trifluoromethylthio and trifluoromethylseleno derivatives possess a markedly higher thermal stability than digermane itself.

Applications

Digermane has a limited number of applications; germane itself is the preferred volatile germanium hydride. Generally, digermane is primarily used a precursor to germanium for use in various applications. Digermane can be used to deposit Ge-containing semiconductors via

chemical vapor deposition Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. In typical CVD, the wafer (subst ...

References

{{Hydrides by group Germanium compounds Metal hydrides Substances discovered in the 1920s Chemical compounds containing metal–metal bonds