2-(2,4-Difluorophenyl)-5-nitropyridine

In the title molecule, C11H6F2N2O2, the benzene and pyridine rings form a dihedral angle of 32.57 (6)°. The nitro group is tilted with respect to the pyridine ring by 12.26 (9)°. An intramolecular C—H⋯F hydrogen bond is present. In the crystal, molecules interact through π–π stacking interactions [centroid–centroid distances = 3.7457 (14) Å], forming columnar arrangements along the b axis. The crystal packing is further enforced by intermolecular C—H⋯O and C—H⋯N hydrogen bonds.

In the title molecule, C 11 H 6 F 2 N 2 O 2 , the benzene and pyridine rings form a dihedral angle of 32.57 (6) . The nitro group is tilted with respect to the pyridine ring by 12.26 (9) . An intramolecular C-HÁ Á ÁF hydrogen bond is present. In the crystal, molecules interact throughstacking interactions [centroid-centroid distances = 3.7457 (14) Å ], forming columnar arrangements along the b axis. The crystal packing is further enforced by intermolecular C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds.
It has been concluded that ppy-containing Ir III complexes can emit lights covering a full range of visible colors by introducing electron-donating or -withdrawing groups to the pyridyl or phenyl rings, which can adjust the HOMO-LUMO energy gaps of the complexes (Shen et al., 2011). As a contribution to this research field, we report herein the synthesis and crystal structure of the title compound. The electron-withdrawing fluoro and nitro groups have been introduced on the phenyl and pyridine rings, respectively, of the title compound, and investigations on Ir III complexes containing the title compound will be carried out soon.
The X-ray analysis of the title compound ( Fig. 1) shows that the molecule is non-planar, the phenyl and pyridine rings forming a dihedral angle of 32.57 (6)°. The nitro group is slightly skewed with respect to the pyridine ring with a dihedral angle of 12.26 (9)%. An intramolecular C-H···F hydrogen bond (Table 1) stabilizes the molecular conformation. In the crystal structure ( Fig. 2), π-π stacking interactions involving overlapping benzene and pyridine rings with centroid-tocentroid distances of 3.7457 (14) Å pack the molecules in columnar arrays running parallel the b axis. Furthermore, the columns interact via intermolecular C-H···O and C-H···N hydrogen bonds (Table 1).
Experimental 2-Chloro-5-nitropyridine (3.18 g, 20.0 mmol), 2,4-difluorophenylboric acid (4.00 g, 25.0 mmol) and triphenylphosphine (0.524 g, 2.0 mmol) were dissolved in THF (50 ml). After an aqueous solution of sodium carbonate (2 M, 30 ml) and palladium diacetate (0.122 g, 0.5 mmol) were added in, the mixture was refluxed under argon atmosphere for 24 h. After being cooled to room temperature, the reacted mixture was poured into water (50 ml) and was further extracted with dichloromethane (50 ml × 3). The combined extract was washed with saturated brine, dried over magnesium sulfate, and then evaporated to dryness. The crude product was purified by silica gel column chromatography (eluant: petroleum ether/ethyl acetate, 6:1 v/v), and colourless crystals of the title compound were at last obtained by recrystallization from ethanol in a yield of 70.5% (3.32 g).

Refinement
All H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 Å for phenyl and pyridyl H-atoms. The U iso (H) were allowed at 1.2U eq (C).

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids.

Data collection
Bruker APEXII CCD diffractometer Radiation source: fine-focus sealed tube Graphite monochromator ω scans Absorption correction: multi-scan (SADABS; Sheldrick, 1996)  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.14 e Å −3 Δρ min = −0.12 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin (2θ) 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.