Erbium(III) chloride
Erbium(III) chloride is a violet solid with the formula ErCl. It is used in the preparation of erbium metal. Preparation. Anhydrous erbium(III) chloride can be produced by the ammonium chloride route. In the first step, erbium oxide is heated with ammonium chloride to produce the ammonium salt of the pentachloride: In the second step, the ammonium chloride salt is converted to the trichlorides by heating in a vacuum at 350-400 ºC: Structural data. Erbium chloride forms crystals of the AlCl type, with monoclinic crystals and the point group "C"2/m. Erbium(III) chloride hexahydrate also forms monoclinic crystals  with the point group of "P"2/"n" ("P"2/"c") - "C". The erbium is octa-coordinated to form [Er(HO)Cl] ions with the isolated Cl completing the structure. Optical properties. Erbium(III) chloride solutions show a negative nonlinear absorption effect. Catalytic properties. The use of erbium(III) chloride as a catalyst has been demonstrated in the acylation of alcohols and phenols and in an amine functionalisation of furfural. It is a catalyst for Friedel–Crafts-type reactions, and can be used in place of cerium(III) chloride for Luche reductions.