Germanate

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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[edit]

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[edit]

The alkali metal orthogermanates, M4GeO4,containing discrete GeO44– ions, form acidic solutions containing GeO(OH)3, GeO2(OH)22– 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, GeO2(OH)22– are present.[10]

Germanate zeolites[edit]

Microporous germanates 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 X 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]

References[edit]

  1. ^ Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005 - Full text (PDF)
  2. ^ a b c d Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
  3. ^ Nguyen, Quang Bac; Lii, Kwang-Hwa (2011). "Cs4UGe8O20: A Tetravalent Uranium Germanate Containing Four- and Five-Coordinate Germanium". Inorganic Chemistry 50 (20): 9936–9938. doi:10.1021/ic201789f. ISSN 0020-1669. 
  4. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419. 
  5. ^ a b Encyclopedia of alkaline earth compounds R.C Ropp, Elsevier 2013 ISBN 978-0-444-59550-8
  6. ^ Ringwood, A.E. (1970). "Phase transformations and the constitution of the mantle". Physics of the Earth and Planetary Interiors 3: 109–155. doi:10.1016/0031-9201(70)90047-6. ISSN 0031-9201. 
  7. ^ Ringwood, A. E.; Seabrook, Merren (1962). "Some High-pressure Transformations in Pyroxenes". Nature 196 (4857): 883–884. doi:10.1038/196883a0. ISSN 0028-0836. 
  8. ^ Hirose, Kei; Nagaya, Yukio; Merkel, Sébastien; Ohishi, Yasuo (2010). "Deformation of MnGeO3post-perovskite at lower mantle pressure and temperature". Geophysical Research Letters 37 (20). doi:10.1029/2010GL044977. ISSN 0094-8276. 
  9. ^ Matsumura, Hisashi; Mamiya, Mikito; Takei, Humihiko (2000). "Growth of pyroxene-type MnGeO3 and (Mn,Mg)GeO3 crystals by the floating-zone method". Journal of Crystal Growth 210 (4): 783–787. doi:10.1016/S0022-0248(99)00850-7. ISSN 0022-0248. 
  10. ^ "Germanium: Inorganic Chemistry" F Glockling Encyclopedia of Inorganic Chemistry Editor R Bruce King (1994) John Wiley and Sons ISBN 0-471-93620-0
  11. ^ Cheng, Jun; Xu, Ruren; Yang, Guangdi (1991). "Synthesis, structure and characterization of a novel germanium dioxide with occluded tetramethylammonium hydroxide". Journal of the Chemical Society, Dalton Transactions (6): 1537. doi:10.1039/dt9910001537. ISSN 0300-9246. 
  12. ^ Li, Hailian; Yaghi, O. M. (1998). "Transformation of Germanium Dioxide to Microporous Germanate 4-Connected Nets". Journal of the American Chemical Society 120 (40): 10569–10570. doi:10.1021/ja982384n. ISSN 0002-7863. 
  13. ^ a b 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
  14. ^ Introduction to Zeolite Molecular Sieves, Jiri Cejka, Herman van Bekkum, A. Corma, F. Schueth, Elsevier, 2007
  15. ^ Zou, Xiaodong; Conradsson, Tony; Klingstedt, Miia; Dadachov, Mike S.; O'Keeffe, Michael (2005). "A mesoporous germanium oxide with crystalline pore walls and its chiral derivative". Nature 437 (7059): 716–719. doi:10.1038/nature04097. ISSN 0028-0836. 
  16. ^ Handbook Of Molecular Sieves: Structures, Rosemarie Szostak, 1992, Van Nostrand Reinhold, ISBN 0442318995, ISBN 978-0442318994
  17. ^ Plévert, Jacques; Sanchez-Smith, Rebeca; Gentz, Travis M.; Li, Hailian; Groy, Thomas L.; Yaghi, Omar M.; O'Keeffe, Michael (2003). "Synthesis and Characterization of Zirconogermanates". Inorganic Chemistry 42 (19): 5954–5959. doi:10.1021/ic034298g. ISSN 0020-1669.