tellurates

Tellurates are salts and esters derived from telluric acid, traditionally formulated as containing the tellurate oxoanions of tellurium in the +6 oxidation state. The most common tellurate anion is TeO4^2−, and salts with alkali metals such as Na2TeO4, K2TeO4, and Cs2TeO4 are well known. Tellurates contrast with tellurites, which involve tellurium in the +4 oxidation state (TeO3^2−).

In aqueous solution, tellurate species exist in equilibrium with various protonated forms depending on pH. Under basic conditions TeO4^2− is the dominant species, while in more acidic media protonated tellurate or mixed oxoanions can form. Tellurates can also assemble into more complex, condensed anions in concentrated solutions or in the solid state, giving polymeric and layered structures in which TeO6 or TeO4 units share oxygens.

Preparation of tellurates typically involves the oxidation of tellurite or telluric acid under appropriate conditions, or the neutralization of telluric acid with alkali bases to yield alkali tellurates. Commercially convenient examples include sodium tellurate and potassium tellurate, which readily crystallize from alkaline media.

Structurally, TeO4 tetrahedra are a common motif. These units can link by corner or edge sharing to form one-dimensional chains, two-dimensional sheets, or three-dimensional networks, depending on cation size and synthesis conditions. Such polymerization affects properties like solubility and lattice energy and is a focus of solid-state tellurate chemistry.

Tellurates find use as precursors to other tellurium oxoanions and in materials science, where their rich structural chemistry informs the development of oxide-based materials and related applications.