Mechanochemical transformations in NaNH2-MgH2 mixtures

Mechanochemical transformations occurring during ball milling of sodium amide (NaNH2) with magnesium hydride (MgH2) taken in 2:3 and 2:1 molar ratios have been investigated using X-ray powder diffraction (XRD) and solid-state nuclear magnetic resonance (SSNMR) techniques. For the 2NaNH2–3MgH2 system the mechanochemical reaction proceeds via the formation of MgNH as an intermediate, whereas magnesium nitride (Mg3N2), sodium hydride (NaH) and hydrogen (∼5 wt%) form as the final products. The overall solid state reaction for this system is 2NaNH2 + 3MgH2 → Mg3N2 + 2NaH + 4H2. However, the mechanochemical transformation of the 2NaNH2–MgH2 system proceeds through the reaction: 2NaNH2 + MgH2 → Mg(NH2)2 + 2NaH, without any hydrogen release. Comparison of the mechanochemical transformations with the previously studied thermochemical transformations reveals that the two approaches lead to the same final products via different reaction pathways.

► We investigate mechanochemically induced transformations in mixtures of NaNH2 and MgH2.
► ∼5 wt% of H2 is released from 2:3 mixture, no H2 is released from 2:1 mixture.
► Mechanochemical and thermochemical reactions in 2:3 mixture yield identical products via different pathways.