Sodium telluride

Sodium telluride is the chemical compound with the formula Na₂Te. This salt is the conjugate base of the thermally unstable acid hydrogen telluride, but it is usually prepared by reduction of tellurium with sodium. Na₂Te is a challenging material to handle because it is very sensitive to air. Air oxidizes it initially to polytellurides, which have the formula Na₂Te_x (x > 1), and ultimately Te metal. Samples of Na₂Te, which are colourless when absolutely pure, generally appear purple or dark gray due to the effects of air oxidation.

Synthesis, structure, and solution properties

The synthesis is typically conducted using ammonia as the solvent.

Na₂Te, like many related compounds with the formula M₂X, adopts the antifluorite structure. Thus, in solid Na₂Te each Te^{2−} ion is surrounded by eight Na⁺ ions and each Na⁺ ion is surrounded by four Te^{2−} ions.

Simple salts of the type M₂X, where X is a monatomic anion, are not typically soluble in any solvent because they have a high lattice energy. Upon addition of water - even moist air - or treatment with alcohols, Te^{2−} protonates:

Na₂Te + H₂O → NaHTe + NaOH

Because of this reaction, many processes attributed to Na₂Te may involve NaHTe (CAS # 65312-92-7), which is more soluble and formed readily.

Applications in organic chemistry

Na₂Te finds use in organic synthesis, both as a reagent for reductions and as a source of Te in the synthesis of organotellurium compounds. Aryl halides are substituted to diaryl tellurides, as illustrated by the synthesis of dinaphthyltelluride:

Na₂Te + 2 C₁₀H₇I → (C₁₀H₇)₂Te + 2 NaI

Na₂Te reacts with 1,3-diynes to give the corresponding tellurophene, which are structurally analogous to thiophenes:

Na₂Te + RC≡C-C≡CR + 2 H₂O → TeC₄R₂H₂ + 2 NaOH

As a reducing agent, Na₂Te converts nitro groups to amines and will cleave certain C-X bonds.

References