(2-Bromoacetyl)ferrocene

In the title molecule, [Fe(C5H5)(C7H6BrO)], the C atoms of the substituted ring have disparate Fe—C bond lengths compared with the unsubstituted ring. In the bromoacetyl residue, the Br and O atoms are co-planar [the O—C—C—Br torsion angle is 5.7 (4)°] and are syn to each other. Helical supramolecular chains along the b axis are formed in the crystal structure mediated by C—H⋯O contacts; the carbonyl-O atom is bifurcated. The chains are linked into layers by C—H⋯π(unsubstituted ring) interactions that stack along the a-axis direction.

In the title molecule, [Fe(C 5 H 5 )(C 7 H 6 BrO)], the C atoms of the substituted ring have disparate Fe-C bond lengths compared with the unsubstituted ring. In the bromoacetyl residue, the Br and O atoms are co-planar [the O-C-C-Br torsion angle is 5.7 (4) ] and are syn to each other. Helical supramolecular chains along the b axis are formed in the crystal structure mediated by C-HÁ Á ÁO contacts; the carbonyl-O atom is bifurcated. The chains are linked into layers by C-HÁ Á Á(unsubstituted ring) interactions that stack along the a-axis direction.

Comment
Ferrocenyl derivatives continue to attract attention owing to their applications as biosensors and drugs (Arezki et al., 2011;Huang et al., 2008;Yang et al., 2007). The title compound, (I), is a synthetic precursor for such molecules.
The molecular structure of (I), Fig. 1, features substituted and unsubstituted cyclopentadienyl rings which form a dihedral angle of 1.14 (18)° indicating an almost parallel relationship; the rings are almost eclipsed when viewed down the ring centroid···Fe···ring centroid axis. The Fe-C bond distances formed by the C atoms in the unsubstituted ring are equal within experimental error, i.e. 2.040 (3) to 2.053 (3) Å, but a disparity is evident in the Fe-C bond distances formed by the substituted ring, range of Fe-C is 2.027 (3) Å, for the C atom carrying the substituent, to 2.060 (3) Å; Table 1. The average Fe-C bond distances are experimentally equivalent as is reflected in the Fe···ring centroid distances of 1.6480 (14), for the C1-ring, compared to 1.6447 (14) Å for the C6-ring; the ring centroid···Fe···ring centroid angle is 179.68 (7)

Experimental
A flask was charged with ferrocene (281 mg, 1.51 mmol) and 2-bromoacetyl bromide (305 mg, 1.51 mmol) in dichloromethane (30 ml); the flask was chilled in an ice-bath. To the solution was added anhydrous aluminium chloride (221 mg, 1.66 mmol) under a nitrogen atmosphere. The reaction mixture, which turned deep-violet, was stirred for an hour. Water was added and the organic phase was extracted with dichloromethane (3 × 15 ml). The organic layer was dried over anhydrous sodium sulfate. The solvent was removed and the product purified by flash column chromatography (ethyl acetate/hexane, 1:9) to give the product as a brown solid; crystals were grown from its solution in dichloromethane.

Refinement
Carbon-bound H-atoms were placed in calculated positions [C-H 0.99 to 1.00 Å, U iso (H) 1.2U eq (C)] and were included in the refinement in the riding model approximation.