The Monoammoniate of Lithium Borohydride, Li(NH3)BH4: An Effective Ammonia Storage Compound

Lithium borohydride absorbs anhydrous ammonia to form four stable ammoniates; Li(NH3)(n)BH4, mono-, di-, tri-, and tertraammoniate. This paper focuses on the monoammoniate, Li(NH3)BH4, which is readily formed on exposure of LiBH4 to ammonia at room temperature and pressure. Ammonia loss from Li(NH3)BH4 commences around 40 degrees C and the compound transforms directly to LiBH4. The crystal structure of Li(NH3)BH4 is reported here for the first time. Its close structural relationship with LiBH4 provides a clear insight into the facile nature and mechanism of ammonia uptake and loss. These materials not only represent an excellent high weight-percent ammonia system but are also potentially important hydrogen stores.