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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 (NEt4)2TeO4. 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.
The E0 or standard reduction potential value is significant as it gives an indication of the strength of the tellurate ion as an oxidizing agent.
Compounds containing the octahedral TeO6−
6 anion are known, these include Ag6TeO6, Na6TeO6 and Hg3TeO6. There are also hydroxyoxotellurates, containing protonated TeO6−
6, such as (NH4)2TeO2(OH)4 (sometimes written as NH4TeO4·2H2O) which contains the octahedral TeO
2(OH)2−
4 ion.
The compound Cs2K2TeO5 contains TeO4−
5 ions which are trigonal bipyramidal. The compound Rb6Te2O9 contains both TeO4−
5 and TeO2−
4 anions. Other compounds whose stoichiometry suggests the presence of TeO4−
5 may contain either the dimeric Te
2O8−
10 made up of two edge-sharing {TeO6} as in Li4TeO5 and Ag4TeO5 or corner-sharing {TeO6} octahedra as in Hg2TeO5.
The dimeric Te
2O8−
10 made up of two edge sharing {TeO6} octahedra is found in the compound Li4TeO5. A similar hydroxy-oxy anion, Te2O6(OH)4 is found in sodium potassium ditellurate(VI) hexahydrate, Na0.5K3.5Te2O6(OH)4·6H2O which contains pairs of edge sharing octahedra.
Polymeric chain anions consisting of corner-shared {TeO6} octahedra (TeO5)4n−
n are found, for example in Li4TeO5.
In aqueous solution tellurate ions are 6 coordinate. In neutral conditions the pentahydrogen orthotellurate ion, H
5TeO−
6, is the most common; in basic conditions, the tetrahydrogen orthotellurate ion, H
4TeO2−
6, and in acid conditions, orthotelluric acid, Te(OH)6 or H6TeO6 is formed.
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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 (NEt4)2TeO4. 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.
The E0 or standard reduction potential value is significant as it gives an indication of the strength of the tellurate ion as an oxidizing agent.
Compounds containing the octahedral TeO6−
6 anion are known, these include Ag6TeO6, Na6TeO6 and Hg3TeO6. There are also hydroxyoxotellurates, containing protonated TeO6−
6, such as (NH4)2TeO2(OH)4 (sometimes written as NH4TeO4·2H2O) which contains the octahedral TeO
2(OH)2−
4 ion.
The compound Cs2K2TeO5 contains TeO4−
5 ions which are trigonal bipyramidal. The compound Rb6Te2O9 contains both TeO4−
5 and TeO2−
4 anions. Other compounds whose stoichiometry suggests the presence of TeO4−
5 may contain either the dimeric Te
2O8−
10 made up of two edge-sharing {TeO6} as in Li4TeO5 and Ag4TeO5 or corner-sharing {TeO6} octahedra as in Hg2TeO5.
The dimeric Te
2O8−
10 made up of two edge sharing {TeO6} octahedra is found in the compound Li4TeO5. A similar hydroxy-oxy anion, Te2O6(OH)4 is found in sodium potassium ditellurate(VI) hexahydrate, Na0.5K3.5Te2O6(OH)4·6H2O which contains pairs of edge sharing octahedra.
Polymeric chain anions consisting of corner-shared {TeO6} octahedra (TeO5)4n−
n are found, for example in Li4TeO5.
In aqueous solution tellurate ions are 6 coordinate. In neutral conditions the pentahydrogen orthotellurate ion, H
5TeO−
6, is the most common; in basic conditions, the tetrahydrogen orthotellurate ion, H
4TeO2−
6, and in acid conditions, orthotelluric acid, Te(OH)6 or H6TeO6 is formed.