Phosphorus(V) nitride α-P3N5:: Synthesis starting from tetraaminophosphonium iodide and crystal structure determination by synchrotron powder diffraction

Pure phosphorus(V) nitride alpha-P3N5 was synthesized by thermal condensation of tetraaminophosphonium iodide [P(NH2)(4)]I at 825 degrees C as a fine crystalline solid. The crystal structure was solved by direct methods and refined by a Rietveld algorithm on the basis of synchrotron powder diffraction data obtained at the ESRF Grenoble, on beamline BM1 (alpha-P3N5, Cc, a = 812.077(4), b = 583.433(4), c = 916.005(5) pm, beta = 115.809(1)degrees, Z = 4, 699 observed reflections, wR(P) = 0.113, R-P = 0.091, R-F = 0.060). With the same topology of the P-N network structure and similar R values the crystal structure may also be described with space group C2/c. In solid alpha-P3N5 there are PN4 tetrahedra which are connected through common edges and corners. Two out of five nitrogen each are bridging three and the remaining N are bridging two neighbouring P atoms. In a nonoxidizing atmosphere alpha-P3N5 is stable up to 800 degrees C. Furthermore the compound is insoluble in all common solvents and resistant against hot acids and alkaline solutions.