Ammonia-mediated, large-scale synthesis of ammonia borane

A simple, large-scale synthesis of ammonia borane from NaBH4 and (NH4)(2)SO4 at 0 degrees C-rt in THF containing 5% NH3 is described. The presence of ammonia is critical for the reaction to proceed and allows the reaction at high concentrations and ambient temperature without the need for anhydrous solvent or inert atmosphere.