1,1'-(Ethane-1,2-di-yl)dipyridinium dichromate(VI).

In the cation of the title salt, (C(12)H(14)N(2))[Cr(2)O(7)], the two pyridinium moieties are in an anti orientation with respect to one another. The dihedral angle between the pyridine rings is 6.3 (2)°. The N-C-C-N torsion angle is 177.5 (2)°. In the dianion, the Cr(VI) ions are in a slightly distorted tetra-hedral coordination environment and the bond angles at the independent Cr(VI) ions are in the ranges 105.93 (10)-110.60 (11) and 107.35 (11)-111.07 (12)°. The Cr-O-Cr angle is 127.96 (12)°. The crystal used was an inversion twin with refined components of 0.510 (19) and 0.490 (19).

In the cation of the title salt, (C 12 H 14 N 2 )[Cr 2 O 7 ], the two pyridinium moieties are in an anti orientation with respect to one another. The dihedral angle between the pyridine rings is 6.3 (2) . The N-C-C-N torsion angle is 177.5 (2) . In the dianion, the Cr VI ions are in a slightly distorted tetrahedral coordination environment and the bond angles at the independent Cr VI ions are in the ranges 105.93 (10)-110.60 (11) and 107.35 (11)-111.07 (12) . The Cr-O-Cr angle is 127.96 (12) . The crystal used was an inversion twin with refined components of 0.510 (19) and 0.490 (19).

Experimental
Crystal data (C 12 (Fig. 1), was performed as a part of a project on the synthesis of a new hybrid compound containing an organic cation and an inorganic oxidant anion.
In the dication, two pyridinium moieties are anti-oriented with respect to one another similar to those observed in the 1,1′-(ethane-1,2-diyl)dipyridinium salts with iodate and periodate counter ions (Gholizadeh, Maleki et al., 2011;Gholizadeh, Hojati et al., 2011). In the dianion, each Cr VI ion is in a slightly distorted tetrahedral coordination environment. The two pyridinium fragments in the cation and the two CrO 3 units in the anion are not symmetrically equivalent.
The Cr-O bonds (with lengths of 1.777 (2)  Orange crystals, suitable for X-ray crystallography, were obtained from a solution of the title salt in H 2 O at room temperature.

Refinement
All H atoms were placed in their calculated positions and then refined using the riding model with atom-H lengths of 0.950 Å (CH) or 0.990 Å (CH 2 ). Isotropic displacement parameters for these atoms were set to 1.20 times U eq of the parent atoms.  The molecular structure of the title compound. Ellipsoids are given at the 50% probability level.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 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.