Crystal structure of 1,1-di-acetyl-ferrocene dihydrazone.

The title compound, [Fe(C7H9N2)2], crystallizes with two crystallographically independent mol-ecules in the unit cell. These represent the chiral atropoisomers distinguished by the mutual arrangement of the two acet-yl-hydrazone groups with a cis conformation of the C=N bonds. The two cyclo-penta-dienyl (Cp) rings are planar and nearly parallel, the tilt between the two rings being 3.16 (16)° [4.40 (18)° for the second independent mol-ecule]. The conformation of the Cp rings is close to eclipsed, the twist angle being 0.1 (2)° [3.3 (2)°]. The two acet-yl-hydrazone substituents are also planar and are inclined at 13.99 (15)/9.17 (16)° [6.83 (17)/14.59 (15)°] relative to the Cp rings. The Fe-C bond lengths range from 2.035 (3) to 2.065 (2) Å, with an average of 2.050 (3) Š[2.036 (3) to 2.069 (2), average 2.046 (3) Å], which agrees well with those reported for most ferrocene derivatives. In the crystal, the mol-ecules form dimers via two strong N-H⋯N hydrogen bonds. The dimers are linked into a three-dimensional framework by weak N-H⋯N hydrogen bonds.