Structure cristalline du cyclotétraphosphate triple de lithium sodium et d'éthylène diammonium trihydrate NaLi[NH 3(CH 2) 2NH 3]P 4O 12.3H 2O

Abstract

Classical methods extensively used for the synthesis of inorganic condensed phosphates are known to give compounds that are intermediate between inorganic and organic. We prepared the title compound to examine the possibility of using, in this new field, the ion exchange resin method. The cyclotetraphosphate is the first condensed phosphate associated with the ethylenediammonium ion and mixed monovalent cations. We describe its chemical preparation and crystal structure. The orthorhombic unit cell has the following dimensions: a = 13.135(3) Å, b = 7.737(2) Å, c = 15.478(4) Å, V = 1573(2)Å 3, D m = 2.020 g/cm 3, D x = 1.951 g/cm 3, μ = 0.297 mm −1, space group is Pcca with Z = 4. The crystal structure has been solved by using 2005 unique reflections with a final R value of 0.043 ( R w = 0.045). The principal feature of this compound lies in its linear atomic arrangement of the monovalent cations with different coordination polyhedra. The lithium cation is statistically distributed on two general positions with 0.5 occupancy, or moves very rapidly between these two positions. The P 4O 4− 12 ring anion is located around the twofold axis. The cohesiveness and the stability of the crystal result from two kinds of weak hydrogen bonds: NH---O and O(W)H---O. The structure of this compound is compared to that of Na 2[NH 3(CH 2) 2NH 3]P 4O 12.2H 2O; half the sodium positions are occupied by lithium cations.