Tetrakis(3,5-xylidinium) dihydrogen cyclohexaphosphate dihydrate

In the title compound, 4C8H12N+·H2P6O18 4−·2H2O, the complete cyclohexaphosphate anion is generated by inversion symmetry. Crystal cohesion and stability are supported by electrostatic interactions which, together with N—H⋯O and O—H⋯O hydrogen bonds, build up a three-dimensional network.


Experimental
Crystal data
The title compound, is built up from H 2 P 6 O 18 4anion, four organic 3,5-xylidiniuium cations and two water molecules ( Fig. 1). A half of the anion, two organic cations and a water molecule constitute the asymmetric unit of (I).
The atomic arrangement is a typical organization in layers as shows the figure 2. These corrugated layers are constituted of anions and water molecules that develop in the same way to plans (b,c) in x = 0. Charge compensation of these layers is achieved by the incorporation of the protonated 3,5-xylidinium cation in the interlayer spaces establishing H-bonds via their NH 3 groups with H 2 P 6 O 18 rings and water molecules. Inside such a structure, the phosphoric ring has an -1 internal symmetry. It develops around the inversion centers (0,0,0) and (0,1/2,1/2), so it is built up by only three independent tetrahedra. With regards to the organic cation arrangement, these groups are in opposition, by creating thus a local invesion center.
Interatomic bond lengths and angles of these groups spread within the respective ranges of 1.371 (3)-1.466 (2) Å and 118.2 (2)-122.1 (2)°. These values are similar to those obtained with the same isomers [Khederi, et al., 2001, Rayes, et al., 2004, Amri, et al., 2008 The aromatic ring of the protonated used amine display an almost coplanar configuration with mean plane deviation of 0.000085 Å and 0.000245 Å. The interplanar distance between the aryl rings of the organic cations is in the vicinity of 4.00 Å, which is significantly longer than 3.80 Å for the π-π interaction (Janiak, 2000). The cohesion forces in this compound are assured by electrostatic interactions, van der Waals contacts and hydrogen bonds (O-H···O, N-H···O).

Experimental
The title  in a less acidic medium (Khederi, et al., 2001). Then this solution was slowly evaporated at room temperature for several days until the formation of transparent prisms of (I) were obtained. Fig. 1. A view of (I) with displacement ellipsoids drawn at the 30% probability level. Symmetry code: (i) -x, -y, -z.