2-Ferrocenyl-N-(2-ferrocenylbenzoyl)-N-(4-methyl-2-pyridyl)benzamide

The title compound, [Fe2(C5H5)2(C30H22N2O2)], a 2:1 product of the reaction of 2-ferrocenylbenzoic acid and 2-amino-4-methylpyridine, forms a twisted molecular structure in the solid state due to steric effects from the two benzene rings ortho-substituted with ferrocenyl and carbonyl-derived groups. A short intramolecular C—H⋯π interaction is observed involving a substituted η5-C5H4 ring and an ortho H atom of the benzene ring on the opposite side of the molecule. In the crystal structure, there are no classical hydrogen bonds: interactions comprise a short C6—H⋯π(C6) interaction involving substituted benzene rings and two C—H⋯O=C interactions per molecule.

The title compound, [Fe 2 (C 5 H 5 ) 2 (C 30 H 22 N 2 O 2 )], a 2:1 product of the reaction of 2-ferrocenylbenzoic acid and 2-amino-4methylpyridine, forms a twisted molecular structure in the solid state due to steric effects from the two benzene rings ortho-substituted with ferrocenyl and carbonyl-derived groups. A short intramolecular C-HÁ Á Á interaction is observed involving a substituted 5 -C 5 H 4 ring and an ortho H atom of the benzene ring on the opposite side of the molecule. In the crystal structure, there are no classical hydrogen bonds: interactions comprise a short C 6 -HÁ Á Á(C 6 ) interaction involving substituted benzene rings and two C-HÁ Á ÁO C interactions per molecule.
The parent compound 2-(Dibenzoylamino)pyridine has been reported previously (Weng et al., 2006). A review of the literature suggests that structures of this type are rare despite the large number of substituted benzamides reported in the literature. Recently, the crystal structures of two compounds N-  et al., 2009a,b), but these differ substantially from (I) in the quinone scaffold or more specifically in the chloro-1,4-naphthoquinone skeleton. The molecular structure of a related compound which has been examined for protonation-controlled regulation of electronic communication, namely, N-Ferrocenecarbonyl-N-(2-pyridyl)ferrocenecarboxamide (Moriuchi & Hirao, 2007) is of interest for comparisons with (I) and also the parent compound (Weng et al., 2006).
(I) crystallizes in the triclinic system in space group P1 (No. 2) and forms an interesting twisted molecular structure in the solid state due to the steric demands of two ortho-substituted benzene rings (Figs. 1-2).
A short intramolecular hydrogen bond is present in (I) involving a substituted η 5 -(C 5 H 4 ) ring and an ortho-H atom of the benzene ring on the opposite side of the molecule. The geometric data are H33B···Cg1 of 2.58 Å, C33B-H33B···Cg1 144° and C33B···Cg1 3.387 (5) Å (Cg1 is the centroid of the C11A-C15A ring). This is quite short and comparable to intramolecular ar C-H···η 5 -(C 5 ) ring interactions present in ferrocene-derived crystal structures deposited on the CSD (Allen, 2002). However, in the vast majority of crystal structures analysed (for such intramolecular interactions) the C-H is only 4/5 bonds from the C 5 ring and oriented on steric grounds to overlap with the cp ring whether this is energetically favourable or not. The intramolecular interaction in (I) is such that the C-H and substituted cyclopentadienyl ring can be considered to be 8 bonds from each other. However, given the steric demands within (I) a similar situation exists whereby the C-H is oriented towards the ring on steric grounds.
The crystal structure also contains three intermolecular interactions comprising a short C-H···π-(C 6 ) interaction {C 6 is the C31B-C36B ring system, with centroid Cg2} and two C-H···O=C weak interactions per molecule. The former is centrosymmetric and has the effect of (I) joining to form a dimer: the other interactions are less significant in terms of crystal structure packing.
supplementary materials sup-2 Experimental Compound (I) was synthesized via standard condensation procedures and similar to the related syntheses reported (Gallagher et al., 2009a,b). Separation of the 1:1 and 2:1 derivatives was undertaken by using flash chromatography using CHCl 3 :ethyl acetate. Typical organic workup and washing gave the product (I) in modest yield of 30-40% as a 2:1 component of the mixture. Crystals suitable for X-ray diffraction were grown from CHCl 3 as colourless blocks over a period of 1-2 weeks.
The compounds gave clean 1 H and 13 C NMR spectra in CDCl 3 and infrared spectra (in CHCl 3 solution, and as KBr disks).

Refinement
Molecule (I) crystallized in the triclinic system; space group P1 (No. 2) and confirmed by the analysis.
H atoms attached to C atoms were treated as riding using the SHELXL97 (Sheldrick, 2008) defaults at 150 (1) K with C-H = 0.95 Å (aromatic) and 0.98 Å (CH 3 ) and U iso (H) = 1.2U eq (C) (aromatic) and 1.5U eq (CH 3 ). Fig. 1. A view of (I) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. The intramolecular C-H···η(C 5 H 4 ) interaction is depicted with a dashed line. Fig. 2. A view of (I) with atoms displayed at the 30% probability level with the intramolecular C-H···π interaction (top centre) and enveloped with an azure coloured van der Waals surface.

Refinement
Refinement on F 2 Hydrogen site location: inferred from neighbouring sites Least-squares matrix: full H-atom parameters constrained