Rivalry under Pressure: The Coexistence of Ambient‐Pressure Motifs and Close‐Packing in Silicon Phosphorus Nitride Imide SiP2N4NH

Non‐metal nitrides such as BN, Si₃N₄, and P₃N₅ meet numerous demands on high‐performance materials, and their high‐pressure polymorphs exhibit outstanding mechanical properties. Herein, we present the silicon phosphorus nitride imide SiP₂N₄NH featuring sixfold coordinated Si. Using the multi‐anvil technique, SiP₂N₄NH was obtained by high‐pressure high‐temperature synthesis at 8 GPa and 1100 °C with in situ formed HCl acting as a mineralizer. Its structure was elucidated by a combination of single‐crystal X‐ray diffraction and solid‐state NMR measurements. Moreover, SiP₂N₄NH was characterized by energy‐dispersive X‐ray spectroscopy and (temperature‐dependent) powder X‐ray diffraction. The highly condensed Si/P/N framework features PN₄ tetrahedra as well as the rare motif of SiN₆ octahedra, and is discussed in the context of ambient‐pressure motifs competing with close‐packing of nitride anions, representing a missing link in the high‐pressure chemistry of non‐metal nitrides.