Chromium(II) Chloride: CrCl₂

Since the discovery of Nozaki and Hiyama in 1977, who found that Cr(II) ion promotes chemoselective C-C coupling in aprotic solvents, extensive studies has been devoted to organochromium(III) reagents. These compounds are prepared by oxidative insertion of CrCl₂ into allyl, alkenyl, alkynyl, propargyl and aryl halides or sulfonates which are well behaved nucleophiles for highly selective organic transformations. Recently, Fürstner has demonstrated that these reactions could be performed with a catalytic amount of CrCl₂ or CrCl₃. Chromium chloride reagent is commercially available and can be used without further purification. It is very hygroscopic, stable in dry air but oxidizes rapidly in the presence of oxygen. Anhydrous chromous chloride could be prepared by the reduction of CrCl₃ with LiAlH₄ or other suitable reducing agents.