Antimonate

In chemistry an antimonate is a compound which contains a metallic element, oxygen, and antimony in an oxidation state of 5. These compounds adopt polymeric structures with M-O-Sb linkages. They can be considered to be derivatives of the hypothetical antimonic acid H₃SbO₄, or combinations of metal oxides and 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.

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−).

Examples

Some examples of antimonates and their structures are shown below:

Li₃SbO₄ has a NaCl superstructure with isolated Sb
₄O¹²⁻
₁₆ units.
Sodium antimonate, NaSbO₃, has the ilmenite structure, with hexagonal close packed oxide ions with each ion, Na and Sb⁵ occupying a third of the octahedral sites.
MgSb₂O₆ has the trirutile structure, which is similar to the rutile structure except that there are two different cations in the lattice.
AlSbO₄ has the rutile structure with random occupancy.
Lead antimonate, Pb₂Sb₂O₇, Naples yellow, has the pyrochlore structure.
Calcium antimonate, Ca₂Sb₂O₇, has the weberite structure.
Ferric ortho-antimonate, Fe₂O₃·Sb₂O₅ or FeSbO₄, has the rutile structure with random occupancy.