2-Ferrocenyl-3-nitro-2H-chromene

In the title compound, [Fe(C5H5)(C14H10NO3)], the cyclopentadienyl rings are in an eclipsed conformation and the pyran ring adopts a half-chair conformation. The mean plane of the pyran ring makes dihedral angles of 79.33 (1) and 80.73 (1)°, respectively, with the substituted and unsubstituted cyclopentadienyl rings. In the crystal, pairs of C—H⋯O hydrogen bonds link the molecules into inversion dimers with R 2 2(16) motifs.

In the title compound, [Fe(C 5 H 5 )(C 14 H 10 NO 3 )], the cyclopentadienyl rings are in an eclipsed conformation and the pyran ring adopts a half-chair conformation. The mean plane of the pyran ring makes dihedral angles of 79.33 (1) and 80.73 (1) , respectively, with the substituted and unsubstituted cyclopentadienyl rings. In the crystal, pairs of C-HÁ Á ÁO hydrogen bonds link the molecules into inversion dimers with R 2 2 (16) motifs.

supplementary materials
Ferrocenyl derivatives exhibit antibacterial (Fouda et al., 2007), antitumor (Jaouen et al., 2004), antifungal and antimalarial (Biot et al., 2004) activities. It was proved that the replacement of the aromatic group by the ferrocenyl moiety in penicillins and cephalosporins could improve their antibiotic activity (Edwards et al., 1975). Against this background, the title compound was chosen for X-ray structure analysis (Fig. 1).

Experimental
To a solution of salicylaldehyde (2 equiv) and (E)-(2-nitrovinyl) ferrocene (1 equiv), 1,4 diazabicyclo[2.2.2]octane (DABCO) (0.5 equiv) was added, and in the absence of solvent the reaction mixture was stirred at 45 °C for 2 h. After completion of the reaction as indicated by TLC, the crude product was extracted with ethylacetate, The organic layer was dried with anhydrous sodium sulfate and concentrated in vacuo. Then the crude product was purified by column chromatography using hexane/EtOAc (9:1) as eluent.

Refinement
Hydrogen atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93-0.98 Å, and with U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title compound, showing the atom-numbering scheme and displacement ellipsoids drawn at the 30% probability level.   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.27 e Å −3 Δρ min = −0.27 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0231 (10) 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.

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