Methyllithium Complex with Lithium Bromide (MeLi–LiBr)

Abstract

CH 3 Li · LiBr [332360‐06‐2] CH 3 Li · LiBr or Br · CH 3 Li · Li (MW 108.821) InChI =  1S/CH3.BrH.2Li/h1H3;1H;;/q;;;+1/p‐1 InChIKey =  XLIKYFMMLMHLKL‐UHFFFAOYSA‐M (metalating agent, preparation of organolithium species, including carbenoids) Solubility : methyllithium lithium bromide complex shows comparable solubility to methyllithium in ethereal solvents in which both are usually supplied. Toluene exhibits sufficient solubility properties, but it can slowly undergo decomposition due to the activation of lithiation processes. MeLi–LiBr reacts exothermically with water and protic solvents. Form Supplied in : methyllithium lithium bromide is supplied as a complex solution (1.5 or 2.2 M) in diethyl ether; density 0.85 g mL −1 at 25 °C. Handling, Storage, and Precautions : it is advised to store MeLi–LiBr in an explosion‐proof refrigerator at temperatures <10 °C in order to minimize major hazards (corrosivity, pyrophoricity, and flammability) also because of the presence of flammable solvents. Due to air and moisture sensitivity, the reagent should be stored under an inert atmosphere. 1 Preparative Methods : a method reported by Parkins deal with the preparation of MeLi · LiBr starting from MeBr and Li metal. 2 Lithium lumps are flattened with a hammer to 1.5 mm thickness and cut into chips (2 × 10 × 1.5 mm) and then placed in a flask containing 800 mL of dry diethyl ether. Thereafter, the mixture is cooled at −25 °C and the flask is purged with dry nitrogen or argon (2 L min −1 during 1–2 min). Through a cooled dropping funnel, MeBr (104.4 g, 1.1 mol) is added and the appearance of turbidity and the increase of internal temperature are diagnostic for the beginning of the reaction. After the addition is complete, the reaction is kept at −15 °C under stirring for an additional hour and subsequently the temperature is slowly increased to 0 °C. The obtained solution is poured into the storage flask, which previously has been filled with inert gas. During the filtration, a fast stream of inert gas is passed through the reaction flask to preserve the solution from oxidative phenomena. After solvent filling and gentle swirling, the titration of the solution indicates approximately 1 M, which corresponds to a chemical yield of 90%.