A unique lithium halide complex, [(LiBr)₂·3HMPA·toluene]: synthesis from reaction of solid NH₄Br with BuⁿLi in HMPA (hexamethylphosphoramide)/toluene media, crystal structure showing two Li–Br units linked by three µ₂-HMPA ligands, and detection of⁷Li ⋯³¹P coupling in solutions of the complex

Abstract

Reaction of solid NH4Br with BunLi and HMPA (hexamethylphosphoramide)(1 : 1 : 2 ratio) in toluene produces (LiBr)2·3HMPA·toluene, (1), shown by X-ray crystallography to contain (LiBr)2·3HMPA molecules whose two terminal Li–Br units are linked by three µ2-HMPA ligands and with toluene molecules lying between these units in the lattice; in arene solutions, the (LiBr)2·3HMPA units remain intact, giving rise in 7Li n.m.r. spectra to 1 : 3 : 3 : 1 quartets caused by through-bond (OP) coupling of each 7Li nucleus to three 31P(HMPA) centres.