4,4′-Oxybis(2,6-dimethylpyridinium) bis(trifluoromethanesulfonate)

In the asymmetric unit of the title salt, C14H18N2O2+·2CF3O3S−, the components are linked by two N—H⋯O and one C—H⋯O hydrogen bonds. The dipyridinium salt demonstrates a skew conformation based upon C—O—C—C torsion angles of 61.5 (3) and 15.1 (4)°. A C—O—C angle of 119.3 (2)° and C—O bond distances of 1.364 (3) and 1.389 (3) Å are consistent with other dipyridyl ethers. The planes of the pyridyl rings exhibit a twist angle of 67.89 (8)°. One of the trifluoromethanesulfonate ions shows disorder of the F atoms [in a 0.52 (7):0.48 (7) occupancy ratio] and an O atom [0.64 (8):0.36 (8) occupancy ratio]. In the crystal, the components are linked by C—H⋯O interactions, which form chains along [101].

In the asymmetric unit of the title salt, C 14 H 18 N 2 O 2+ Á-

Comment
The structures of bridged diaryls have been examined for many years and here we submit another structure into this data set. Based upon dissimilar C-O-C-C torsion angles of 61.5 (3)° and 15.1 (4)°, this structure exhibits a skew conformation (van der Heijden et al. 1975). The previously reported structures of 4,4′-oxybisdipyridyls and their cations (Dunne et al. 1996, Maas, 1985, Constable et al., 1995  The structure of the title salt is shown in Figure 1. N-H···O hydrogen bonds between the dication and the two anions are seen between N1-H1N···O4 and N2-H2N···O7. There are no π-π interactions between pyridinium rings of the dications observed. One of the trifluoromethanesulfonate ions shows a disorder at the fluorines with a 52.0:48.0 percentage distribution and at one oxygen with a 64:36 percentage distribution.

Experimental
Colorless crystals of the title compound formed from the slow decomposition of neat 2,6-dimethyl-4-triflatopyridine.

Refinement
All non-hydrogen atoms were refined anisotropically by full matrix least squares on F 2 . Fluorine atoms F1, F2, and F3 were disordered over two positions (52.0/48.0) and were refined anisotropically with similar distances and amplitudes using SADI restraints and EADP constraints. Oxygen atom O2 was found to be disordered over two sites (63.5/36.5) and was refined with DFIX restraints for S-O bond length of 1.44(0.01) Å and O-O distances of 2.41(0.02) Å and ISOR restraint for O2 and O2′. Hydrogen atoms H1N and H2N were found from a Fourier difference map and were refined isotropically with N-H distance of 0.87 (2) Å and 1.20 U eq of parent N atom. All other hydrogen atoms were placed in calculated positions with appropriate carbon hydrogen bond lengths; C-H(Ar) 0.950 Å and CH 3 0.980 Å and 1.20 and 1.50 U eq of parent C atom.

4,4′-Oxybis(2,6-dimethylpyridinium) bis(trifluoromethanesulfonate)
Crystal data 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.