Dicyclohexylammonium 3,5-dinitrobenzoate

The asymmetric unit of the title salt, C12H24N+·C7H3N2O6 −, contains two cations and two anions. In the crystal, the cations and anions are connected by N—H⋯O hydrogen bonds, forming a 12-membered ring with an R 4 4(12) graph-set motif. The center of this 12-membered ring coincides with an inversion centre. π–π stacking is observed between parallel benzene rings [centroid–centriod distance = 3.771 (2) Å].

The asymmetric unit of the title salt, C 12 H 24 N + ÁC 7 H 3 N 2 O 6 À , contains two cations and two anions. In the crystal, the cations and anions are connected by N-HÁ Á ÁO hydrogen bonds, forming a 12-membered ring with an R 4 4 (12) graph-set motif. The center of this 12-membered ring coincides with an inversion centre.stacking is observed between parallel benzene rings [centroid-centriod distance = 3.771 (2) Å ].  Table 1 Hydrogen-bond geometry (Å , ).  Intermolecular H-bonding interactions were observed in the crystal lattice. Two cations and two anions were connected by intermolecular N-H···O H-bonding to form a 12-membered ring, with a graph set assignment, R 4 4 (12). The center of this ring coincide with an inversion centre. π···π interactions also help to stack the 3,5-dinitrobenzoates in the lattice.

Experimental
To a 250 ml round bottom flask fitted with a condenser was added dicyclohexyl amine (0.01 mol), dichloromethane (15 ml), triethylamine (0.5 ml)with magnetic stirring. 3,5-Dinitrobenzoyl chloride (0.01 mol) was added gradually. The reaction mixture was stirred at room temperature for 1 h and then refluxed for 2 h. The product precipitated out as yellow powder, which was washed three times with water. Recrystallization from ethyl acetate produced the crystals of the title compound.

Refinement
The structure was solved by direct methods (SHELXS97, Sheldrick, 2008) and expanded using Fourier techniques. All non-H atoms were refined anisotropically.
The C-bound H atoms are all placed at geometrical positions with C-H = 0.93, 0.97 and 0.98 Å for phenyl, methylene and methine H-atoms respectively. All C-bound phenyl, methylene and methine H-atoms are refined using riding model with U iso (H) = 1.2U eq (Carrier). The N-bound H-atoms are located from difference Fourier map and refined using isotropically with bond distance restraints.
A total of 7 restraints have been used in the refinement, they were bond distances restraints. The N-H bond distances will become too long, 1.00-1.07 Å if not restrained. Thus, the N5-H1N distance was restrained to be 0.87 (1) Å, and the other three N-H distances were restrained to be the same within standard uncertainty of 0.01.

Figure 1
The title compound was shown at 50% probability thermal ellipsoids with the atom numbering scheme.

Figure 2
The packing diagram of the unit cell was projected along the a axis and shown at 50% probability thermal ellipsoids.  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. The structure was solved by direct methods (SHELXS97, Sheldrick, 2008) and expanded using Fourier techniques. All non-H atoms were refined anisotropically. The C-bound H atoms are all placed at geometrical positions with C-H = 0.93, 0.97 and 0.98 Å for phenyl, methylene and methine H-atoms respectively. All C-bound phenyl, methylene and methine H-atoms are refined using riding model with U iso (H) = 1.2U eq (Carrier). The N-bound H-atoms are located from difference Fourier map and refined using isotropically with bond distance restraints. A total of 7 restraints have been used in the refinement, they were bond distances restraints. The N-H bond distances will become too long, 1.00-1.07 (1) Å if not restrained. Thus, the N5-H1N distance was restrained to be 0.87 (1)