selenolate

A selenolate refers to the conjugate base of a selenol (R-Se-H). In organic chemistry, the term most often denotes the anion R-Se−, generated by deprotonation of a selenol. The inorganic analogue is the hydroselenide anion, HSe−. Selenolates are soft, highly polarizable nucleophiles. When isolated as salts (for example NaSeR or KSeR), they are typically handled under inert atmosphere in polar aprotic solvents.

Preparation and properties: Selenolates are usually prepared by treating a selenol with a strong base such as sodium hydride, n-butyllithium, or potassium tert‑butoxide. The exact choice of base and solvent depends on the substrate and the desired counterion. They can also be generated in situ for subsequent reaction. Selenolates exhibit high nucleophilicity and can be stabilized by chelating or bulky substituents, but are often sensitive to air and moisture, tending to oxidize to diselenides.

Reactivity and applications: In organic synthesis, selenolates readily attack alkyl halides to form selenides (R-Se-R′) and can react with acyl chlorides to give selenoesters. They participate in substitution and various selenium‑containing functionalization strategies, and on oxidation they form diselenides (R-Se-Se-R). As ligands, selenolates can coordinate to metal centers, providing soft donor sites that influence the properties of certain transition‑metal complexes and catalytic systems. In biological contexts, the selenolate form of selenocysteine plays a role in enzyme active sites at physiological pH.

Safety and handling: Selenium compounds can be toxic in excess, and selenolates are often air‑ and moisture‑sensitive. Appropriate precautions and disposal are advised.

See also: selenol, selenocysteine, diselenide, selenoester.