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, for example potassium hexafluorogermanate, K2GeF6.
Germanium is similar to silicon forming many compounds with tetrahedral {GeO4} units although it can also exhibit 5 and 6 coordination. Analogues of all the major types of silicates and aluminosilicates have been prepared. For example the compounds Mg2GeO4 (olivine and spinel forms), CaGeO3(perovskite structure), Be2GeO4 (phenakite structure) show the resemblance to the silicates. BaGe4O9 has a complex structure containing 4 and 6 coordinate germanium 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, for example MnGeO3 has a pyroxene type structure similar to that of MgSiO3 which is a significant mineral in the mantle.
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−. 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.
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