orthostannate

An orthostannate is a chemical compound containing the orthostannate anion, which has the formula [Sn(OH)6]2-. This anion is characterized by a central tin atom coordinated to six hydroxide ligands, arranged in an octahedral geometry. Orthostannates are derivatives of orthostannic acid, Sn(OH)4, though this acid is not typically isolated. The orthostannate anion is considered the fully hydrated form of stannic acid, SnO2·nH2O.

These compounds are typically formed by the reaction of tin(IV) oxide or stannic acid with strong alkaline solutions. For example, reacting tin dioxide with concentrated sodium hydroxide can yield sodium orthostannate. The solubility of orthostannates in water varies depending on the cation. Alkali metal orthostannates are generally soluble, while those with divalent or trivalent cations are often insoluble or sparingly soluble.

Orthostannates are stable in alkaline solutions but tend to hydrolyze in acidic conditions, regenerating stannic acid or tin(IV) oxide. They are important in the study of tin chemistry and have potential applications in areas such as catalysts and materials science, although their use is not widespread. Examples of orthostannates include sodium orthostannate (Na2[Sn(OH)6]) and potassium orthostannate (K2[Sn(OH)6]).