Diacridinium hexachloridoplatinate(IV) dihydrate

The asymmetric unit of the title compound, (C13H10N)2[PtCl6]·2H2O, contains a protonated acridine cation, one half of a [PtCl6]2− dianionic complex and a solvent water molecule. The octahedral [PtCl6]2− dianion is located on an inversion centre. π–π interactions between neighboring acridinium cations produce stacks along the a axis; the shortest distance between the centroids of the six-membered rings within the cations is 3.553 (9) Å. In the crystal, two independent intermolecular O—H⋯Cl hydrogen bonds, both involving the same Cl atom of the anion as acceptor, give rise to chains also running along the a axis; in addition each water molecule, as a hydrogen-bond acceptor, is linked to the acridinium N—H group.

The asymmetric unit of the title compound, (C 13 H 10 N) 2 -[PtCl 6 ]Á2H 2 O, contains a protonated acridine cation, one half of a [PtCl 6 ] 2À dianionic complex and a solvent water molecule. The octahedral [PtCl 6 ] 2À dianion is located on an inversion centre.interactions between neighboring acridinium cations produce stacks along the a axis; the shortest distance between the centroids of the six-membered rings within the cations is 3.553 (9) Å . In the crystal, two independent intermolecular O-HÁ Á ÁCl hydrogen bonds, both involving the same Cl atom of the anion as acceptor, give rise to chains also running along the a axis; in addition each water molecule, as a hydrogen-bond acceptor, is linked to the acridinium N-H group.

Experimental
Crystal data (C 13 Table 1 Hydrogen-bond geometry (Å , ).  The essentially planar acridinium cations [maximum deviation from the least-squares plane is equal to 0.025 (17) Å], are stacked in columns along the a-axis (Fig. 2); the shortest distance between the centroids of the six-membered rings in neighboring cations in the stack is equal to 3.553 (9) Å. Two independent O-H···Cl bonds, both involving atom Cl1 of the anion as acceptor (Table 1), give rise to the chains also running along the a-axis; in addition each water molecule, as an H-bond acceptor is linked to the acridinium N-H group (Fig. 2).

Experimental
To a solution of K 2 PtCl 6 (0.1999 g, 0.411 mmol) in H 2 O (20 ml) was added acridine (0.1548 g, 0.864 mmol) and the mixture was refluxed for 7 h. The precipitate was then separated by filtration, washed with water and acetone, and dried at 50 °C, to give an orange powder (0.2198 g). Crystals suitable for X-ray analysis were obtained by slow evaporation from a CH 3 CN solution.  Fig. 1. The structure of the title compound, with displacement ellipsoids drawn at the 50% probability level; H atoms are shown as small circles of arbitrary radius. Unlabelled atoms are related to the reference atoms by the (1-x, 1-y, -z) symmetry transformation.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.