Sodium selenide

Preparation

This colourless solid is prepared by the reaction of selenium with a solution of sodium in liquid ammonia at -40 °C.

Alternatively, sodium selenide can be prepared by the reaction of gaseous hydrogen selenide with metallic sodium at 100 °C.

Reactions

Like other alkali metal chalcogenides, this material is highly sensitive to water, easily undergoing hydrolysis to give mixtures of sodium biselenide (NaSeH) and hydroxide. This hydrolysis occurs because of the extreme basicity of the Se²⁻ ion.

Na₂Se + H₂O → NaHSe + NaOH

Similarly, sodium selenide is readily oxidized to polyselenides, a conversion signaled by off-white samples.

Sodium selenide reacts with acids to produce toxic hydrogen selenide gas.

Na₂Se + 2 HCl → H₂Se + 2 NaCl

The compound reacts with electrophiles to produce the selenium compounds. With alkyl halides, one obtains a variety of organoselenium compounds:

Na₂Se + 2 RBr → R₂Se + 2 NaBr

Organotin and organosilicon halides react similarly to give the expected derivatives:

Na₂Se + 2 Me₃XCl → (Me₃X)₂Se + 2 NaCl (X ∈ Si, Ge, Sn)

Safety

Sodium selenide should be stored and handled away from moisture and air.