Bis[(1RS,2RS)-4,4′-(1-azaniumyl-2-hydroxyethane-1,2-diyl)dipyridinium] tris[tetrachloridopalladate(II)]

The asymmetric unit of the title compound, (C12H16N3O)2[PdCl4]3, consists of a 4,4′-(1-azaniumyl-2-hydroxyethane-1,2-diyl)dipyridinium dication and one and a half tetrachloridopalladate(II) anions; the latter has inversion symmetry. In the cation, the pyridinium rings attached to the central 1-azaniumyl-2-hydroxyethane fragment show an anti conformation, as indicated by the central C—C—C—C torsion angle of −178.1 (4)°, and they are inclined to one another by 25.7 (2)°. In the crystal, the cations and anions are linked through N—H⋯Cl and O—H⋯Cl hydrogen bonds. There are also π–π contacts [centroid–centroid distance = 3.788 (3) Å] and a number of C—H⋯O and C—H⋯Cl interactions are present, consolidating the formation of a three-dimensional structure.


Experimental
Crystal data (C 12
The asymmetric unit of the title compound consists of one threefold charged organic cation in a general position and two independent [PdCl 4 ] 2dianions, one of which is located on a crystallographic inversion center (Fig. 1). In the cation, the pyridinium rings attached to the central 2-ammoniumethanol fragment show an anti conformation, as indicated by the C8-C1-C2-C3 torsion angle of -178.1 (4)°, and form a dihedral angle of 25.7 (2)°. The Pd atoms have square-planar coordination environments with Pd-Cl distances ranging from 2.2760 (10) to 2.3056 (11) Å.
For the preparation of the palladium complex, a solution of 2,4,5-tris(pyridin-4-yl)-4,5-dihydro-1,3-oxazole (0.05 g, 0.16 mmol) in methanol and concentrated HCl (37%, 3 ml) was added dropwise to a stirring solution of potassium tetrachloridopalladate (0.05 g, 0.16 mmol) in water (5 ml). The resulting yellow solution was stirred for 30 min at 333 K, whereupon the solution was left to evaporate slowly at room temperature. After two weeks, red crystals were isolated [Yield: 30%]. Spectroscopic and TGA data for the title compound are available in the archived CIF.

Figure 1
The molecular structure of the asymmetric unit of the title compound, with the atom-labelling. Displacement ellipsoids are drawn at the 50% probability level. [symmetry code: (i) -x + 1, -y + 2, -z + 1].  A view along the a axis of the crystal packing of the title compound, with the hydrogen bonds shown as dashed lines (see Table 1 for details).

Special details
Experimental. Spectroscopic and TGA data for the title compound: IR(KBr, cm -1 ): 3440,3211,3064,2937,2888,1669,1630,1509,1421,1358,1294,999,832. TGA: Calcd. for HCl: 3.08. Found: 3.26% (303-448 K); Calcd. for PdCl 2 : 15.49. Found: 15.85% (448-523 K). Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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 > σ(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.