Antimonate

In chemistry an antimonate is a compound which contains a metallic element, oxygen and antimony in an oxidation state of +5. These compounds can be considered to be salts of the hypothetical acid H₃SbO₄, or combinations of metal oxides, antimony pentoxide, Sb₂O₅. Historically these compounds were assumed to be analogous to the phosphates and formulas such as LiSbO₃·3H₂O and Na₂H₂Sb₂O₇·5H₂O were used and the compounds described as hydrated meta-antimonates and pyro-antimonates. LiSbO₃.3H₂O is now known to be LiSb(OH)₆ and contain the Sb(OH)₆⁻ anion and that Na₂H₂Sb₂O₇·5H₂O is actually NaSb(OH)₆.^[1]

Some examples of anhydrous antimonates and their structures are shown below:-

• Li₃SbO₄ has an NaCl superstructure with isolated Sb₄O₁₆¹²⁻ units^[2]
• NaSbO₃ has the ilmenite structure, with hexagonal close packed oxide ions with each ion, Na⁺ and Sb⁵⁺ occupying a third of the octahedral sites^[1]
• MgSb₂O₆ has the trirutile structure, which is similar to the rutile structure except that there are two different cations in the lattice.^[1]
• AlSbO₄ has the rutile with random occupancy^[1]
• Pb₂Sb₂O₇ has the pyrochlore structure.^[1]
• Ca₂Sb₂O₇ has the weberite structure^[1]
• FeSbO₄ has the rutile with random occupancy^[1]

Antimonate in chemical nomenclature

IUPAC recommendations are that compounds with anions containing antimony(V) have the antimonate(V) suffix or antimonate followed by a charge number, for example the Sb(OH)₆⁻ ion would be called hexahydridoxidoantimonate(V) or alternatively hexahydroxidoantimonate(1–).^[3]

References