Bis(triethylammonium) chloranilate

In the crystal structure of the title compound [systematic name: bis(triethylammonium) 2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-diolate], 2C6H16N+·C6Cl2O4 2−, the chloranilate anion lies on an inversion center. The triethylammonium cations are linked on both sides of the anion via bifurcated N—H⋯(O,O) and weak C—H⋯O hydrogen bonds to give a centrosymmetric 2:1 aggregate. The 2:1 aggregates are further linked by C—H⋯O hydrogen bonds into a zigzag chain running along [01-1].

In the crystal structure of the title compound, an acid-base interaction involving proton transfer is observed between chloranilic acid and triethylamine, and one chloranilate anion and two triethylammnoium cations are linked by bifurcated N-H···O and weak C-H···O hydrogen bonds (Table 1) to afford a centrosymmetric 2:1 aggregate (Fig. 1). The 2:1 aggregates are further linked by intermolecular C-H···O hydrogen bonds, forming a zigzag chain running along the [011] direction (Fig. 2).

Experimental
Single crystals were obtained by slow evaporation from an acetonitrile solution (100 ml) of chloranilic acid (100 mg) and triethylamine (97 mg) at room temperature.

Refinement
C-bound H atoms were positioned geometrically (C-H = 0.98 or 0.99 Å) and refined as riding, allowing for free rotation of the methyl group. U iso (H) values were set at 1.2U eq (C) or 1.5U eq (methyl C). The N-bound H atom was found in a difference Fourier map and refined isotropically. The refined N-H distance is 0.867 (18) Å.

Computing details
Data collection: PROCESS-AUTO (Rigaku/MSC, 2004); cell refinement: PROCESS-AUTO (Rigaku/MSC, 2004); data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: CrystalStructure (Rigaku/MSC, 2004) and PLATON (Spek, 2009   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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq