SrH4 P6 N12 and SrP8 N14 : Insights into the Condensation Mechanism of Nitridophosphates under High Pressure.

The (imido)nitridophosphates SrH4 P6 N12 and SrP8 N14 were synthesized as colorless crystals by high-pressure/high-temperature reactions using the multianvil technique (5 GPa, ca. 1075 °C). Stoichiometric amounts of Sr(N3 )2, P3 N5 , and amorphous HPN2 were used as starting materials. Whereas the crystal structure of SrH4 P6 N12 was solved and refined from single-crystal X-ray diffraction data and confirmed by Rietveld refinement, the structure of SrP8 N14 was determined from powder diffraction data. In order to confirm the structures, 1 H and 31 P solid-state NMR spectroscopy and FTIR spectroscopy were carried out. The chemical composition was confirmed with EDX measurements. Both compounds show unprecedented layered network structure types, built up from all-side vertex-sharing PN4 tetrahedra which are structurally related. The structural comparison of both compounds gives first insights into the hitherto unknown condensation mechanism of nitridophosphates under high pressure.