1-[3,5-Bis(trifluoromethyl)phenyl]-3-(2-pyridyl)thiourea

The title compound, C14H9F6N3S, exhibits a nearly planar conformation in the solid state, with a dihedral angle between the planes of the benzene and pyridine rings of 14.86 (3)°. The pyridine N atom allows for the formation of a six-membered N—H⋯Npy hydrogen-bonded ring, thus forcing the two amide H atoms of the thiourea group to point in opposite directions. The second N—H group forms an intermolecular N—H⋯S hydrogen bond with the S atom of an adjacent molecule. The F atoms of the two trifluoromethyl groups display rotational disorder around the C—CF3 axis, with an occupancy ratio of 0.54 (1):0.46 (1).

The title compound, C 14 H 9 F 6 N 3 S, exhibits a nearly planar conformation in the solid state, with a dihedral angle between the planes of the benzene and pyridine rings of 14.86 (3) . The pyridine N atom allows for the formation of a six-membered N-HÁ Á ÁN py hydrogen-bonded ring, thus forcing the two amide H atoms of the thiourea group to point in opposite directions. The second N-H group forms an intermolecular N-HÁ Á ÁS hydrogen bond with the S atom of an adjacent molecule. The F atoms of the two trifluoromethyl groups display rotational disorder around the C-CF 3 axis, with an occupancy ratio of 0.54 (1):0.46 (1).   Table 1 Hydrogen-bond geometry (Å , ).

1-[3,5-Bis(trifluoromethyl)phenyl]-3-(2-pyridyl)thiourea
Huadong Yue, Yifeng Wang, Aibao Xia, Shuping Luo and Danqian Xu S1. Comment Thiourea compounds have been extensively studied over the last few years due to their pharmacological and biological activities (Struga et al., 2007). Recently, excellent results have been also achieved with the use of the bifunctional thiourea catalysts, which effectively activate carbonyl groups and imines through double hydrogen-bonding interactions in asymmetric synthesis (Akiyama et al., 2006). Herein, we synthesized the title compound (I) and determined its crystal structure (Fig.1). The benzene and pyridine rings in the structural unit of (I) are almost perfectly coplanar with a dihedral angle between their planes of only 14.86 (3)°. Like other 2-pyridyl thioureas, the title compound exhibits both intramolecular and intermolecular hydrogen bonding interactions. The pyridine nitrogen N3 allows for the formation of a six membered N-H···N pyr hydrogen bonded ring which forces the two amide hydrogen atoms of the thiourea group to point in opposite directions. At the same time, the N1-H1 and C9-H9 moieties of the pyridine ring form intermolecular N-H···S and C-H···S hydrogen bonds with the S atom of an adjacent molecule (Fig. 2). This weak hydrogen-bonding network leads to the formation of infinite chains of molecules thus stabilizing the crystal packing.

S2. Experimental
The title compound was synthesized by treating 3,5-bis-trifluoromethyl-phenyl isothiocyanate (2.71 g, 10 mmol) with 2amino pyridine (0.94 g, 10 mmol) in MeCN (30 ml) under stirring at room temperature for 24 h. Suitable crystals of the title compound were obtained by slow evaporation of an actonitrile solution at room temperature (3.28 g, 10 mmol).

S3. Refinement
Large solvent accessible voids are found in the crystal. The volumes (31 Å 3 per cavity, four equivalent cavities per unit cell) of these voids are not quite large enough to host acetonitrile molecules, the solvent of crystallization, and no significant residual electron density is seen in difference Fourier syntheses maps. The largest residual electron density peak and the deepest negative density in these voids are 0.40 (0.97 Å from S1) and -0.30 (1.30 Å from C4), respectively.
Also, an attempted correction for the electron density within the voids using the Squeeze algorithm implemented in the program PLATON (Spek, 2003) does not significantly improve the quality of the dataset or refinement. The fluorine atoms of the two CF 3 groups exhibit conformational disorder around the C4-C13 and C6-C14 bonds with an occupancy ratio of 0.54 (1) to 0.46 (1). They are refined with restraints for the C-F bond lengths and the F···F interatomic distances to maintain nearly tetrahedral geometry. All C-F bond lengths are restrained to 1.35 (5) Å and the displacement parameters of the disordered F atoms are restrained to an approximate isotropic behaviour. All carbon-bond H atoms are placed in calculated positions with C-H = 0.93 Å (aromatic) and refined using a riding model, with U iso (H) = 1.2 eq (C). N-bound H atoms are located in a difference map and refined with an N-H distance restraint of 0.83 (2) Å.    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.