MS13-P07 Intergrowth of new phosphorus nitride oxide high-pressure phases elucidated using synchrotron radiationWhereas silicates are among the most thoroughly investigated classes of compounds, much less is known about the closely related oxonitridophosphates and phosphorus oxide nitrides. Different O/N ratios and flexible bonding to N atoms enable a rich structural chemistry, further enhanced by the possibility of including H atoms. Yet, access to new compounds in the system P/O/N/(H) is difficult and often involves high pressure and high temperature. Starting from amorphous phosphorus imide nitride oxide, various SiO2-like modifications of PON can be obtained. Yet, syntheses at 1400 °C and up to 16 GPa yielded microcrystalline samples with complex diffraction patterns. Powder diffraction patterns being inconclusive, first information was obtained by electron diffraction and suitable crystallites of new compounds could be identified. Microfocused synchrotron radiation (ID11, ESRF, Grenoble) enables unique insight into the crystal chemistry of such compounds with unprecedented accuracy. Diffraction data from intergrown micrometer-sized crystallites correspond to the superposition of diffraction patterns of H3P8O8N9  and new phosphorus oxide nitrides.
The compound with the idealized formula P74O59N84 (monoclinic, C2, V = 4878 Å³) exhibits a 3D network of P(O,N)4 tetrahedra, some sharing three vertices. P40O31N46 (monoclinic, C2, V = 2651 Å³) contains similar building blocks and exhibits a higher degree of disorder. Both compounds contain a motif that is similar to the unit cell content of H3P8O8N9, but, in contrast, does not involve an interrupted network. This motif is characterized by 8-ring layers interconnected by additional pairs of tetrahedra. In P74O59N84 and P40O31N46, these patterns are interconnected by additional building blocks. These build up arrays of layers perpendicular to two crystallographic directions. These intersecting layers form channels along , in which the H3P8O8N9-like motifs are embedded. The additional layers mainly contain vierer rings. In P40O31N46, one type of these additional layers is thicker and less corrugated than in P74O59N84. Taken as a whole, all structures are mainly built up from dreier, vierer, sechser and achter rings.
 S. J. Sedlmaier, V. R. Celinski, J. Schmedt auf der Günne, W. Schnick, Chem. Eur. J. 2012, 18, 4358-4366.Keywords: microfocus diffraction, phosphorus nitride oxide, tertrahedra networks