[12136-60-6] · Li2Se · Lithium Selenide · (MW 92.84)
Physical Data: d 2.91 g cm-3; red-brown solid or milky white crystalline suspension in THF.
Solubility: sol water; sparingly sol THF.
Preparative Methods: reduction of Selenium with Lithium in liquid ammonia produces red-brown Li2Se after NH3 evaporation.3 Reaction of Se with 2 equiv Lithium Triethylborohydride in THF gives a suspension of Li2Se. The method is somewhat limited by scale and produces flammable byproducts.1 For large-scale preparations, reduction of Se with Li in THF in the presence of naphthalene as a catalyst is safe and more economical.2
Handling, Storage, and Precautions: should be used directly as prepared. Use in a fume hood.
The reaction of Li2Se with alkyl halides gives dialkyl selenides in high yields. It is less reactive than K2Se or Sodium Selenide.1,2 Benzyl, 4-chlorobenzyl, 2-phenylethyl, and pentyl bromides give selenides in yields of above 54% (eq 1), but no selenide is obtained when 2-octyl bromide is used as a substrate.1,2 Bis(trialkylsilyl) selenides are obtained when trialkylchlorosilanes are treated with Li2Se (eq 2).4,5
Jacek Mlochowski & Ludwik Syper
Technical University of Wroclaw, Poland