Combining MN6 Octahedra and PN5 Trigonal Bipyramids in the Mica-like Nitridophosphates MP6 N11 (M=Al, In).

Abstract

Layered silicates are a very versatile class of materials with high importance to humanity. The new nitridophosphates MP6 N11 (M=Al, In), synthesized from MCl3 , P3 N5 and NH4 N3 in a high-pressure high-temperature reaction at 1100 °C and 8 GPa, show a mica-like layer setup and feature rare nitrogen coordination motifs. The crystal structure of AlP6 N11 was elucidated from synchrotron single-crystal diffraction data (space group Cm (no. 8), a=4.9354(10), b=8.1608(16), c=9.0401(18) Å, β=98.63(3)°), enabling Rietveld refinement of isotypic InP6 N11 . It is built up from layers of PN4 tetrahedra, PN5 trigonal bipyramids and MN6 octahedra. PN5 trigonal bipyramids have been reported only once and MN6 octahedra are sparsely found in the literature. AlP6 N11 was further characterized by energy-dispersive X-ray (EDX), IR and NMR spectroscopy. Despite the vast amount of known layered silicates, there is no isostructural compound to MP6 N11 as yet.