Open‐Shell 3d Transition Metal Nitridophosphates M^IIP₈N₁₄ (M^II=Fe, Co, Ni) by High‐Pressure Metathesis

Abstract

3d transition metal nitridophosphates MIIP8N14 (MII=Fe, Co, Ni) were prepared by high‐pressure metathesis indicating that this route might give a systematic access to a structurally rich family of M‐P‐N compounds. Their structures, which are stable in air up to at least 1273 K, were determined through powder X‐ray diffraction and consist of highly condensed tetra‐layers of PN4 tetrahedra and MN6 octahedra. Magnetic measurements revealed paramagnetic behavior of CoP8N14 and NiP8N14 down to low temperatures while, FeP8N14 exhibits an antiferromagnetic transition at TN=3.5(1) K. Curie–Weiss fits of the paramagnetic regime indicate that the transition metal cations are in a oxidation state +II, which was corroborated by Mössbauer spectroscopy for FeP8N14. The ligand field exerted by the nitride ions in CoP8N14 and NiP8N14 was determined from UV/Vis/NIR data and is comparable to that of aqua‐ligands and oxophosphates.

Comprehensive Investigation of Anion Species in Crystalline Li+ ion Conductor Li27−x[P4O7+xN9−x]O3 (x≈1.9(3))

“…The final structure model is based on SCXRD but uses site occupancies from neutron powder diffraction without further refinement. P−O/N bond lengths in lithium oxonitridophosphates are assumed to be longer than pure P−O bonds and shorter than pure P−N bonds, due to the larger ionic radius of N 3− in contrast to O 2− and stronger covalency of the P−N bond [22,33,34] . Despite the mixed occupancy bond lengths in Li 27− x [P 4 O 7+ x N 9− x ]O 3 can be best compared to lithium ortho‐oxonitridophosphates, Li 7 PN 4 , or Li 3 PO 4 .…”