Germanes

Germanes are the class of chemical compounds formed between germanium and hydrogen. The best known member is germane, GeH4, but the term also covers higher hydrides such as digermane Ge2H6, as well as related organogermanes and polymeric germanes with Ge–Ge backbones or Ge–C bonds. Collectively, germanes are the hydrogen-containing germanium compounds studied for their structural diversity and potential in materials chemistry.

In terms of structure, GeH4 is a tetrahedral molecule with Ge–H bonds. Ge2H6 consists of two germanium centers linked by a Ge–Ge single bond, each bearing terminal hydrogens. Higher hydrides and polymers exhibit various Ge–Ge connectivity patterns and can include organic substituents. The bonding in germanes is related to that in silicon and carbon hydrides, but with greater polarizability and different reactivity.

Preparation of germanes typically involves reduction of germanium halides or oxides, or hydrogermylation and related methods for organogermanes. Germane is often prepared by reductive processes using hydride donors, while organogermanes are made through reactions that introduce Ge–C bonds. Polymeric germanes and related materials are accessed by polymerization of germane or by assembly of Ge-containing monomers.

Reactions and properties vary across the class. Germane is a colorless, highly flammable gas that hydrolyzes to form germanium oxides and hydrogen. Heavier or more complex germanes may be gases or liquids with variable air and moisture sensitivity. Many germanes are reactive and require careful handling.

Applications of germanes include precursors for chemical vapor deposition of germanium-containing films and materials, syntheses of organogermanes for catalysis, and investigations into polymeric germanes for electronic and optoelectronic uses. Safety considerations emphasize toxicity, flammability, and potential explosiveness when handling volatile germane.