MH4P6N12 (M = Mg, Ca): New Imidonitridophosphates with an Unprecedented Layered Network Structure Type

Isotypic imidonitridophosphates MH4P6N12 (M = Mg, Ca) have been synthesized by high-pressure/high-temperature reactions at 8 GPa and 1000 degrees C starting from stoichiometric amounts of the respective alkaline-earth metal nitrides, P3N5, and amorphous HPN2. Both compounds form colorless transparent platelet crystals. The crystal structures have been solved and refined from single-crystal X-ray diffraction data. Rietveld refinement confirmed the accuracy of the structure determination. In order to quantify the amounts of H atoms in the respective compounds, quantitative solid-state H-1 NMR measurements were carried out. EDX spectroscopy confirmed the chemical compositions. FTIR spectra confirmed the presence of NH groups in both structures. The crystal structures reveal an unprecedented layered tetrahedral arrangement, built up from all-side vertex-sharing PN4 tetrahedra with condensed dreier and sechser rings. The resulting layers are separated by metal atoms.