Germanium(II) hydroxide
File:Germanium(II)_hydroxide.png Germanium(II) hydroxide, normally written as Ge(OH)2, is a poorly characterised compound, sometimes called hydrous germanium(II) oxide or germanous hydroxide. It was first reported by Winkler in 1886.{{cite journal|last1=Everest|first1=David A.|last2=Terrey|first2=Henry|title=467. Germanous oxide and sulphide|journal=Journal of the Chemical Society (Resumed)|year=1950|pages=2282|issn=0368-1769|doi=10.1039/jr9500002282}}
Properties and preparation
Germanium(II) hydroxide is formed as a white or yellow precipitate when base is added to solutions containing GeII, produced for example by the reduction of an acid solution of germanium dioxide, GeO2, with hypophosphorous acid, H3PO2,{{cite journal|last1=Babich|first1=Olga A.|last2=Ghosh|first2=Manik C.|last3=Gould|first3=Edwin S.|title=Preparation of aqueous solutions of hypovalent germanium; reactions involving germanium-(ii) and -(iii)|journal=Chemical Communications|issue=11|year=2000|pages=907–908|issn=1359-7345|doi=10.1039/b000401o}} or alternatively by hydrolysis of GeCl2.{{Greenwood&Earnshaw}} The initial precipitate, which has no definite stoichiometry, can be represented by GeO·xH2O, Ge(OH)2·xH2O, or loosely Ge(OH)2. It is only slightly soluble in water or alkali{{cite journal|last1=Yang|first1=Duck J.|last2=Jolly|first2=William L.|last3=O'Keefe|first3=Anthony.|title=Conversion of hydrous germanium(II) oxide to germynyl sesquioxide, (HGe)2O3|journal=Inorganic Chemistry|volume=16|issue=11|year=1977|pages=2980–2982|issn=0020-1669|doi=10.1021/ic50177a070}} and not appreciably soluble in perchloric acid, HClO4, but is soluble in hydrochloric acid, HCl. On digestion with sodium hydroxide, NaOH, it yields a brown insoluble compound, which after drying in vacuo forms a brown pyrophoric substance with the approximate stoichiometry of (HGe)2O3. On the basis of the infrared spectrum, (HGe)2O3 may contain a germanium hydrogen bond, Ge-H.