Large- and Small-Scale Syntheses of Donor-Free Rare-Earth Triiodides from the Metals and Ammonium Iodide

Rare-earth triiodides free of donor solvents, LnI₃ (Ln = Sc, Y, La-Lu), have been prepared in quantities as high as 76 g and in yields between 72% (Sc) and 98% (La) by the reaction between the corresponding metal and excess ammonium iodide in a two-step, one-pot procedure that is conducted in borosilicate glassware at temperatures of 350-430 °C in commercial tube furnaces. Procedures for both large-scale and small-scale syntheses are described, with specific examples for Ln = Sc, Y, La, Pr, Nd, Gd, Dy, Ho, and Lu. While the large-scale synthesis described here utilizes specialized glassware, the small-scale preparation may be performed in commercially available glassware.