Synthesis of amorphous boron nitride from the molecular precursor ammonia-monochloroborane

Ammonia-monochloroborane, NH₃BH₂Cl, has been synthesized from the reaction of ammonia-borane with HCl in Et₂O. Decomposition of the solid under NH₃ to 600 °C produced amorphous BN in 97% yield. The ¹¹B magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectrum of the amorphous BN is indicative of boron in the same environment as in hexagonal BN. Subsequent pyrolysis of the amorphous BN to 1000 °C produced turbostratic BN. Pyrolysis of NH₃BH₂Cl under vacuum to 1100 °C led to the formation of turbostratic BN as confirmed by x-ray diffraction (XRD) analysis. Gas evolution during this pyrolysis confirmed that the precursor loses H₂ and HCl.