GeO4

GeO4 commonly denotes the tetra-oxo germanate unit GeO4^4- in aqueous chemistry. It is the tetrahedral anion form of germanium in the +4 oxidation state and is analogous to the orthogermanate concept found for silicon in silicate chemistry (SiO4^4-). GeO4^4- arises from the deprotonation of the corresponding germanic acid H4GeO4 in strongly basic conditions.

In solution, the germanate system can be viewed as a series of protonation states. Starting from the neutral acid H4GeO4, successive deprotonations yield H3GeO4^−, H2GeO4^2−, HGeO4^3−, and finally GeO4^4− under high pH. The central atom remains germanium in the +4 oxidation state, coordinated tetrahedrally to four oxide ligands.

Salts of GeO4^4- can be prepared by neutralizing solutions of the germanic acid with suitable cations, including alkali metals. In coordination chemistry, GeO4^4- can act as a ligand and form complexes with various metals, expanding the chemistry beyond simple inorganic salts.

GeO4-related species are of interest in geochemistry and materials science. In natural settings, germanate species can occur where germanium is mobilized under alkaline conditions. In materials chemistry, germanate units and derivatives contribute to the properties of certain glasses and crystalline materials, with potential applications in optics and photonics.

See also: Silicate, Stannate, Germanate minerals.