Germanate

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The orthogermanate anion

In chemistry, germanate is a compound containing an oxyanion of germanium. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central germanium atom,[1] for example potassium hexafluorogermanate, K2GeF6.[2]

Germanate oxy compounds

Germanium is similar to silicon forming many compounds with tetrahedral {GeO4}

perovskite structure), Be2GeO4 (phenakite structure) show the resemblance to the silicates.[4] BaGe4O9 has a complex structure containing 4 and 6 coordinate germanium.[citation needed] Germanates are important for geoscience as they possess similar structures to silicates and can be used as analogues for studying the behaviour of silicate minerals found in the Earth's mantle;[5] for example, MnGeO3 has a pyroxene type structure similar to that of MgSiO3 which is a significant mineral in the mantle.[6][7][8]

Germanates in aqueous solutions

The alkali metal orthogermanates, M4GeO4, containing discrete GeO4−
4 ions, form acidic solutions containing GeO(OH)−
3, GeO
2(OH)2−
2 and [(Ge(OH)4)8(OH)3]3−.[2] Neutral solutions of germanium dioxide contain Ge(OH)4, but at high pH germanate ions such as GeO(OH)−
3, GeO
2(OH)2−
2 are present.[9]

Germanate zeolites

Microporous germanate zeolites were first prepared in the 1990s.[10][11] A common method of preparation is hydrothermal synthesis using an organic amine as a template (structure determining agent).[12] The frameworks are negatively charged due to extra oxide ions which leads to higher coordination numbers for germanium of 5 and 6. The negative charge is balanced by the positively charged amine molecules.

In addition to the ability of germanium to exhibit 4, 5 or 6 coordination, the greater length of the Ge–O bond in the {GeO4} tetrahedral unit compared to Si–O in {SiO4} and the narrower Ge–O–Ge angle (130°–140°) between corner shared tetrahedra allow for unusual framework structures.

Å interconnected by channels defined by 30-membered rings (the naturally occurring zeolite faujasite with channels defined by 12-membered rings[15]). Zeolites with frameworks containing silicon and germanium (silicogermanates), aluminium and germanium (aluminogermanates) and zirconium and germanium (zirconogermanates) are all known.[12][16]

See also

References

  1. ^ Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005 – Full text (PDF)
  2. ^
    ISBN 0123526515
  3. PMID 21939186
    .
  4. ^
    ISBN 978-0-08-037941-8
    .
  5. ISSN 0031-9201
    .
  6. S2CID 4183493
    .
  7. ISSN 0094-8276
    .
  8. ISSN 0022-0248
    .
  9. ISBN 0-471-93620-0
  10. ISSN 0300-9246
    .
  11. ISSN 0002-7863
    .
  12. ^
    ISBN 9780444532961
  13. ^ Introduction to Zeolite Molecular Sieves, Jiri Cejka, Herman van Bekkum, A. Corma, F. Schueth, Elsevier, 2007
  14. S2CID 4411828
    .
  15. ISBN 978-0442318994
  16. PMID 12971765
    .
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