Two new ammonium diphosphates: crystal structure of Mn_0.5NH₄H₂P₂O₇·H₂O and MnNaNH₄P₂O₇·3H₂O

Abstract

Two new ammonium diphosphates, Mn_0.5NH₄H₂P₂O₇·H₂O (1) and MnNaNH₄P₂O₇·3H₂O (2), have been synthesized and investigated by single crystal X-ray diffraction. Compound (1) crystallizes in the triclinic space group P1̅, and the unit cell dimensions are a = 7.0029(2) Å, b = 7.4401(2) Å, c = 7.8771(2) Å, α = 80.444(1)°, β = 71.359(1)°, γ = 87.408(1)°, V = 383.48(2) ų, Z = 2; compound (2) crystallizes in the monoclinic space group Cc, with the following unit cell dimensions: a = 10.1124(4) Å, b = 16.4448(7) Å, c = 5.6000(3) Å, β = 104.304(2)°, V = 902.39(7) ų, Z = 4. Final residuals are: R = 0.0281 and w_R = 0.0769, by using 2356 reflections with I > 2σ(I), for (1); R = 0.0301 and w_R = 0.0682, by using 2322 reflections with I > 2σ(I), for (2). The crystal packing of Mn_0.5NH₄H₂P₂O₇·H₂O consists of layers parallel to ac plane formed by MnO₆ regular octahedra, H₂P₂O₇ double tetrahedra and ammonium cations. Strong hydrogen bonds embed the dihydrogendiphosphate groups in the framework. The crystal packing of MnNaNH₄P₂O₇·3H₂O is made up of layers of P₂O₇ double tetrahedra, NaO₇ monocapped octahedra and MnO₆ regular octahedra down c. Water and ammonium cations molecules fill up the cavities between the above mentioned polyhedra. Strong hydrogen bonds complete the network.