Mixed Tin Valence in the Tin(II/IV)‐Nitridophosphate Sn3P8N16

Sn3P8N16 combines the structural versatility of nitridophosphates and Sn within one compound. It was synthesized as dark gray powder in a high‐pressure high‐temperature reaction at 800 °C and 6 GPa from Sn3N4 and P3N5. The crystal structure was elucidated from single‐crystal diffraction data (space group C2/m (no. 12), a = 12.9664(4), b = 10.7886(4), c = 4.8238(2) Å, β = 109.624(1)°) and shows a 3D‐network of PN4 tetrahedra, incorporating Sn in oxidation states +II and +IV. The Sn cations are located within eight‐membered rings of vertex‐sharing PN4 tetrahedra, stacked along the [001] direction. A combination of solid‐state nuclear magnetic resonance spectroscopy, 119Sn Mössbauer spectroscopy and density functional theory calculations was used to confirm the mixed oxidation of Sn. Temperature‐dependent powder X‐ray diffraction measurements reveal a low thermal expansion of 3.6 ppm/K up to 750 °C, beyond which Sn3P8N16 starts to decompose.