Germanate
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]
Contents
Germanate oxy compounds
Germanium is similar to silicon forming many compounds with tetrahedral {GeO4}[2] units although it can also exhibit 5[3] and 6[2] coordination. Analogues of all the major types of silicates and aluminosilicates have been prepared.[4] For example the compounds Mg2GeO4 (olivine and spinel forms), CaGeO3(perovskite structure), Be2GeO4 (phenakite structure) show the resemblance to the silicates.[4][5] BaGe4O9 has a complex structure containing 4 and 6 coordinate germanium [5] 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 earths mantle,[6] for example MnGeO3 has a pyroxene type structure similar to that of MgSiO3 which is a significant mineral in the mantle.[7][8][9]
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.[10]
Germanate zeolites
Microporous germanate zeolites were first prepared in the 1990s.[11][12] A common method of preparation is hydrothermal synthesis using an organic amine as a template (structure determining agent).[13] 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.[14] A zeolite reported in 2005[15] has large pores – 18.6 × 26.2 Å interconnected by channels defined by 30-membered rings (the naturally occurring zeolite faujasite with channels defined by 12-membered rings [16]). Zeolites with frameworks containing silicon and germanium (silicogermanates), aluminium and germanium (aluminogermanates) and zirconium and germanium (zirconogermanates) are all known.[13][17]
See also
- Bismuth germanate (bismuth germanium oxide, BGO)
- Sodium germanate
References
- ↑ Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005 – Full text (PDF)
- ↑ 2.0 2.1 2.2 2.3 Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 4.0 4.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 5.0 5.1 Encyclopedia of alkaline earth compounds R.C Ropp, Elsevier 2013 ISBN 978-0-444-59550-8
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ "Germanium: Inorganic Chemistry" F Glockling Encyclopedia of Inorganic Chemistry Editor R Bruce King (1994) John Wiley and Sons ISBN 0-471-93620-0
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 13.0 13.1 Zeolites and Related Materials: Trends Targets and Challenges(SET), 1st Edition, 4th International FEZA Conference, 2008, Paris, France; Eds. Gedeon, Massiani,Babonneau; Elsevier Science; ISBN 9780444532961
- ↑ Introduction to Zeolite Molecular Sieves, Jiri Cejka, Herman van Bekkum, A. Corma, F. Schueth, Elsevier, 2007
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Handbook Of Molecular Sieves: Structures, Rosemarie Szostak, 1992, Van Nostrand Reinhold, ISBN 0442318995, ISBN 978-0442318994
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
