Telluride (chemistry)

The telluride ion is the anion Te²⁻ and its derivatives. It is analogous to the other chalcogenide anions, the lighter O²⁻, S²⁻, and Se²⁻, and the heavier Po²⁻.^[1]

In principle, Te²⁻ is formed by the two-e⁻ reduction of tellurium. The redox potential is −1.14 V.^[2]

Te(s) + 2 e⁻ ↔ Te²⁻

Although solutions of the telluride dianion have not been reported, soluble salts of bitelluride (TeH⁻) are known.^[3]

Tellurides also describe a class of organotellurium compounds formally derived from Te²⁻. An illustrative member is dimethyl telluride, which results from the methylation of telluride salts:

2 CH₃I + Na₂Te → (CH₃)₂Te + 2 NaI

Dimethyl telluride is formed by the body when tellurium is ingested. Such compounds are often called telluroethers because they are structurally related to ethers with tellurium replacing oxygen, although the length of the C–Te bond is much longer than a C–O bond. C–Te–C angles tend to be closer to 90°.^[4]

Many metal tellurides are known, including some telluride minerals. These include natural gold tellurides, like calaverite and krennerite (AuTe₂), and sylvanite (AgAuTe₄). They are minor ores of gold, although they comprise the major naturally occurring compounds of gold. (A few other natural compounds of gold, such as the bismuthide maldonite (Au₂Bi) and antimonide aurostibite (AuSb₂), are known). Although the bonding in such materials is often fairly covalent, they are described casually as salts of Te²⁻. Using this approach, Ag₂Te is derived from Ag⁺ and Te²⁻. Catenated Te anions are known in the form of the polytellurides. They arise by the reaction of telluride dianion with elemental Te:

Te^2- + n Te → Te_n+1^2-

Tellurides have no large scale applications aside from cadmium telluride photovoltaics.^[5] Both bismuth telluride and lead telluride are exceptional thermoelectric materials.^[6][7] Some of these thermoelectric materials have been commercialized.^[8][9][10]