Tellurate

In chemistry tellurate is a compound containing an oxyanion of tellurium where tellurium has an oxidation number of +6. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central tellurium atom.

Historically the name tellurate was only applied to oxyanions of tellurium with oxidation number +6, formally derived from telluric acid Te(OH)₆, and the name tellurite referred to oxyanions of tellurium with oxidation number +4, formally derived from tellurous acid (HO)₂TeO and these names are in common use. However tellurate and tellurite are often referred to as tellurate(VI) and tellurate(IV) respectively in line with IUPAC renaming recommendations. The metatellurate ion is TeO2−
4 and the orthotellurate ion is TeO6−
6. Other oxyanions include pentaoxotellurate, TeO4−
5, ditellurate, Te
2O8−
10 and polymeric anions with 6-coordinate tellurium such as (TeO4−
5)_n.

The metatellurate ion TeO2−
4 is analogous to the sulfate ion, SO2−
4 and the selenate ion, SeO2−
4. Whereas many sulfates and selenates form isomorphous salts the tetrahedral metatellurate ion is only found in a few compounds such as the tetraethylammonium salt NEt₄TeO₄. Many compounds with a stoichiometry that suggests the presence of a metatellurate ion actually contain polymeric anions containing 6-coordinate tellurium(VI), for example sodium tellurate, Na₂TeO₄ which contains octahedral tellurium centers sharing edges.

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