Crystal Structure and Infrared Spectrum of New Magnesium Tetra-Ammonium Cyclotriphosphate Tetrahydrate Mg(NH4)4(P3O9)2 · 4 H2O

Abstract The new cyclotriphosphate Mg(NH4)4(P3O9)2 · 4 H2O was synthesized by the metathesis reaction of Boullé and characterized by single crystal X-ray diffraction and infrared spectroscopy. The compound crystallizes in the monoclinic system, space group P21/c, with the following unit cell parameters: a = 8.6120(5), b = 14.6390(10), and c = 8.8610(17) Å; β = 95.330(8)°; V = 1112.3(2) Å3. The crystal structure was refined up to a final R value of 0.0277 using 2543 independent reflections. Magnesium cation is coordinated by two P3O9 3– ring anions and four water molecules, displaying quite regular octahedral geometry. Ammonium polyhedra NH41O6 and NH42O6 are, respectively, connected to the MgO6 octahedron by O10—O4 edge and the O11 water molecule. The three-dimensional framework is built up from [Mg(P3O9)2(H2O)4]4– complex anions linked together via hydrogen bonds interactions made up by (NH4)+ cations. Last, the infrared spectrum of title compound was recorded and interpreted.