(R,R)-(N,N′-Diferrocenylcyclohexane-1,2-diyldiimino)dibenzonitrile

In the title compound, [Fe2(C5H5)2(C34H34N4)], two ferrocenes are bridged by a cyclohexane-1,2-diamine unit. The cyclopentadienyl rings of the two ferrocene units are almost parallel [dihedral angles of 0.7 (4) and 1.0 (4)° in the two units] and eclipsed, as is typically found for similar monosubstituted ferrocene derivatives. The dihedral angle formed by the two benzene rings is 20.2 (3)°. The Fe—C bond lengths to the two substituted Cp rings vary from 2.014 (4) to 2.070 (3) Å, and are in the normal range. In the crystal, molecules are linked by C—H⋯N interactions, forming an infinite two-dimensional network.

In the title compound, [Fe 2 (C 5 H 5 ) 2 (C 34 H 34 N 4 )], two ferrocenes are bridged by a cyclohexane-1,2-diamine unit. The cyclopentadienyl rings of the two ferrocene units are almost parallel [dihedral angles of 0.7 (4) and 1.0 (4) in the two units] and eclipsed, as is typically found for similar monosubstituted ferrocene derivatives. The dihedral angle formed by the two benzene rings is 20.2 (3) . The Fe-C bond lengths to the two substituted Cp rings vary from 2.014 (4) to 2.070 (3) Å , and are in the normal range. In the crystal, molecules are linked by C-HÁ Á ÁN interactions, forming an infinite two-dimensional network.  Table 1 Hydrogen-bond geometry (Å , ). This work was supported by a start-up grant from Southeast University.

Related literature
The chemistry of ferrocene has received much attention because of its applications in many fields, such as in catalysis (Yang et al., 2002), organic or organometallic synthesis and materials, non-linear optical (NLO) materials (Long, 1995;Roberto et al., 2000), and medicinal materials. As a part of our ongoing investigations of ferrocene derivatives we have prepared the title compound and report herein on its structure in the solid state.
The molecular structure of the title compound is illustrated in Fig. 1, and the geometrical parameters are given in the archived CIF. The cyclopentadienyl rings in the two ferrocene moieties (involving atoms Fe1 and Fe2) are almost parallel, with dihedral angles of 0.7 (4) ° and 1.0 (4) °, respectively, and eclipsed as viewed down the normal to the Cp ring. The cyclohexane ring has a chair configuration and the two ferrocenemethylamino groups are equatorially bonded to it, as expected. The dihedral angle formed by the two benzene rings is 20.2 (3)°. The Fe-C bond lengths to the two substituted Cp ring vary from 2.014 (4) to 2.070 (3) Å, and are in agreement with the values reported for related compounds (Hess et al., 1999;Base et al., 2002).
In the crystal the molecules are linked by C-H···N interactions, involving the nitrile N-atoms, so forming an infinite two-dimensional network (Table 1).

Experimental
The preparation of the precursors of the title compound has been reported on previously (Cho et al., 1999;Sutcliffe et al., 2002). For the preparation of the title compound, K 2 CO 3 (10 mmol) was added to a mixture of (R,R)-N,N'-Bis(ferrocenylmethyl)cyclohexane-1, 2-diamine (5 mmol) and 3-(bromomethyl)benzonitrile (10 mmol) in acetone (40 ml), and the mixture was heated to reflux for 6 h. The mixture was then cooled, filtered, and the filtrate evaporated to dryness.
The yellow solid obtained was recrystallized from a mixture of acetone and petroleum ether (yield: 68%). Yellow crystals, suitable for X-ray diffraction analysis, were obtained by slow evaporation of a dichloromethane solution at rt after 3 days.

Refinement
The H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.93 -0.98 Å, with U iso (H) = 1.2U eq (parent C-atom

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.