Lanthanum(III) Chloride, Complex with Lithium Chloride, Solution in Tetrahydrofuran

Abstract

[405204-22-0] Li2LaCl5 (MW 327.78) 1S/5ClH.La.2Li/h5*1H;;;/q;;;;;+3;2*+1/p-5 InChIKey = YSKOYVQYUJUXCN-UHFFFAOYSA-I (Soluble lanthanide salt, useful as an additive1 to reduce side reactions in the addition of lithium or Grignard reagents to carbonyl compounds) Physical Data: white, hygroscopic solid. Solubility: sol tetrahydrofuran. Form Supplied in: generally as a 0.3–0.5 M solution in tetrahydrofuran; in preparation, it is initially isolated as a hygroscopic white solid. Purification: filtration under argon through a Schlenk filter. See Preparative Methods. Handling, Storage, and Precautions: anhydrous LaCl3·2LiCl should be kept under an inert atmosphere and dissolved in anhydrous tetrahydrofuran as soon as possible after drying. Lanthanum(III) chloride is corrosive to metals and irritating to the skin and eyes. It can also be a skin sensitizer, and can be damaging to aquatic environments. Preparative Methods: commercially available LaCl3·6H2O is dissolved in water with 2 equiv of lithium chloride in a Schlenk flask, and then evaporated to a powder under high vacuum. While stirring, the powder is gradually warmed from ambient temperature by 20 °C increments every 4 h to a final temperature of 160 °C.1, 2 The solid is then cooled and dissolved in anhydrous tetrahydrofuran. The resulting solution is subsequently stirred under argon for 24 h in the presence of 4 A molecular sieves. The solution is then filtered through a Schlenk filter to remove any insoluble materials, and can be used directly. The solution of LaCl3·2LiCl so obtained is stable under argon indefinitely.1 Another method, apparently used industrially, is to add anhydrous LaCl3 powder to a commercially available 0.5 M solution of lithium chloride in tetrahydrofuran, followed by warming at reflux for 12 h. The majority of the tetrahydrofuran is removed by distillation, and then the solution is diluted with fresh dry tetrahydrofuran until it is approximately 0.8 M in concentration as measured by ICP-MS. The solution is then held under nitrogen prior to use.3