page_title: Germanium
section_title: Chemistry
hierarchical_section_title: Germanium / Characteristics / Chemistry
caption_attribution_description: English: Nucleophilic Addition With Organogermanium
context_page_description: Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard-brittle, grayish-white metalloid in the carbon group, chemically similar to its group neighbours silicon and tin. Pure germanium is a semiconductor with an appearance similar to elemental silicon. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature.
  Because it seldom appears in high concentration, germanium was discovered comparatively late in the history of chemistry. Germanium ranks near fiftieth in relative abundance of the elements in the Earth's crust. In 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position on his periodic table, and called the element ekasilicon. Nearly two decades later, in 1886, Clemens Winkler found the new element along with silver and sulfur, in a rare mineral called argyrodite. Although the new element somewhat resembled arsenic and antimony in appearance, the combining ratios in compounds agreed with Mendeleev's predictions for a relative of silicon. Winkler named the element after his country, Germany.
context_section_description: Elemental germanium starts to oxidize slowly in air at around 250 °C, forming GeO₂ . Germanium is insoluble in dilute acids and alkalis but dissolves slowly in hot concentrated sulfuric and nitric acids and reacts violently with molten alkalis to produce germanates ([GeO
  ₃]²⁻
  ). Germanium occurs mostly in the oxidation state +4 although many +2 compounds are known. Other oxidation states are rare: +3 is found in compounds such as Ge₂Cl₆, and +3 and +1 are found on the surface of oxides, or negative oxidation states in germanides, such as −4 in Mg
  ₂Ge. Germanium cluster anions (Zintl ions) such as Ge₄²⁻, Ge₉⁴⁻, Ge₉²⁻, [(Ge₉)₂]⁶⁻ have been prepared by the extraction from alloys containing alkali metals and germanium in liquid ammonia in the presence of ethylenediamine or a cryptand. The oxidation states of the element in these ions are not integers—similar to the ozonides O₃⁻.
  Two oxides of germanium are known: germanium dioxide (GeO
  ₂, germania) and germanium monoxide, (GeO). The dioxide, GeO₂ can be obtained by roasting germanium disulfide (GeS
  ₂), and is a white powder that is only slightly soluble in water but reacts with alkalis to form germanates. The monoxide, germanous oxide, can be obtained by the high temperature reaction of GeO₂ with Ge metal. The dioxide (and the related oxides and germanates) exhibits the unusual property of having a high refractive index for visible light, but transparency to infrared light. Bismuth germanate, Bi₄Ge₃O₁₂, (BGO) is used as a scintillator.
  Binary compounds with other chalcogens are also known, such as the disulfide (GeS
  ₂), diselenide (GeSe
  ₂), and the monosulfide (GeS), selenide (GeSe), and telluride (GeTe). GeS₂ forms as a white precipitate when hydrogen sulfide is passed through strongly acid solutions containing Ge(IV). The disulfide is appreciably soluble in water and in solutions of caustic alkalis or alkaline sulfides. Nevertheless, it is not soluble in acidic water, which allowed Winkler to discover the element. By heating the disulfide in a current of hydrogen, the monosulfide (GeS) is formed, which sublimes in thin plates of a dark color and metallic luster, and is soluble in solutions of the caustic alkalis. Upon melting with alkaline carbonates and sulfur, germanium compounds form salts known as thiogermanates.
  Four tetrahalides are known. Under normal conditions GeI₄ is a solid, GeF₄ a gas and the others volatile liquids. For example, germanium tetrachloride, GeCl₄, is obtained as a colorless fuming liquid boiling at 83.1 °C by heating the metal with chlorine. All the tetrahalides are readily hydrolyzed to hydrated germanium dioxide. GeCl₄ is used in the production of organogermanium compounds. All four dihalides are known and in contrast to the tetrahalides are polymeric solids. Additionally Ge₂Cl₆ and some higher compounds of formula GeₙCl₂ₙ₊₂ are known. The unusual compound Ge₆Cl₁₆ has been prepared that contains the Ge₅Cl₁₂ unit with a neopentane structure.
  Germane (GeH₄) is a compound similar in structure to methane. Polygermanes—compounds that are similar to alkanes—with formula GeₙH₂ₙ₊₂ containing up to five germanium atoms are known. The germanes are less volatile and less reactive than their corresponding silicon analogues. GeH₄ reacts with alkali metals in liquid ammonia to form white crystalline MGeH₃ which contain the GeH₃⁻ anion. The germanium hydrohalides with one, two and three halogen atoms are colorless reactive liquids.
  The first organogermanium compound was synthesized by Winkler in 1887; the reaction of germanium tetrachloride with diethylzinc yielded tetraethylgermane (Ge(C
  ₂H
  ₅)
  ₄). Organogermanes of the type R₄Ge (where R is an alkyl) such as tetramethylgermane (Ge(CH
  ₃)
  ₄) and tetraethylgermane are accessed through the cheapest available germanium precursor germanium tetrachloride and alkyl nucleophiles. Organic germanium hydrides such as isobutylgermane ((CH
  ₃)
  ₂CHCH
  ₂GeH
  ₃) were found to be less hazardous and may be used as a liquid substitute for toxic germane gas in semiconductor applications. Many germanium reactive intermediates are kno
caption: Nucleophilic addition with an organogermanium compound.
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