PHOSPHORUS(V) NITRIDE ALPHA-P3N5 - SYNTHE SIS STARTING FROM TETRAAMINOPHOSPHONIUM IODIDE AND CRYSTAL-STRUCTURE DETERMINATION BY SYNCHROTRONPOWDER DIFFRACTION

Pure phosphorus(V) nitride alpha-P3N5 was synthesized by thermal conde nsation of tetraaminophosphonium iodide [P(NH2)(4)]I at 825 degrees C as a fine crystalline solid. The crystal structure was solved by direc t methods and refined by a Rietveld algorithm on the basis of synchrot ron 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) p m, 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 ne twork structure and similar R values the crystal structure may also be described with space group C2/c. In solid alpha-P3N5 there are PN4 te trahedra which are connected through common edges and corners. Two out of five nitrogen each are bridging three and the remaining N are brid ging 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 so lutions.