Crystal structure of 3-ferrocenyl-1-phenyl-1H-pyrrole, [Fe(η5-C5H4 cC4H3 NPh)(η5-C5H5)]

The molecular structure of 3-ferrocenyl-N-phenylpyrrole, [Fe(η5-C5H4 cC4H3 NPh)(η5-C5H5)] has an L-type shape, with the N-phenylpyrrole moiety fused with the cyclapentadienyl ring being approximately coplanar.

The molecular structure of the title compound, [Fe(C 5 H 5 )(C 15 H 12 N)], consists of a ferrocene moiety with an N-phenylpyrrole heterocycle bound to one cyclopentadienyl ring. The 1,3-disubstitution of the pyrrole results in an Lshaped arrangement of the molecule with plane intersections of 2. 78 (17) between the pyrrole and the N-bonded phenyl ring and of 8.17 (18) between the pyrrole and the cyclopentadienyl ring. In the crystal, no remarkable intermolecular interactions are observed

Structural commentary
The 1,3-disubstitution of the pyrrole ring in compound (I) results in an L-type shape of the molecule with a bending of 34.882 (2) of the three catenated ring systems, as calculated by the angle between the centroids of the respective cyclopentadienyl, pyrrole and phenyl rings. The three rings are nearly coplanar, with plane intersections of 8.17 (18) between the central pyrrole ring with the cyclopentadienyl ring and of 2.78 (17) between the pyrrole ring and the N-bound phenyl ring (Fig. 1). The ferrocenyl substituent itself exhibits a nearly eclipsed conformation with a torsion angle of À12.2 (2) . The 3-substitution affects the lengths of the C C bonds in the pyrrole ring, resulting in a shortening to 1.349 (4) Å of the H3C3 C4H4 bond compared to 1.378 (4) Å for the C2 C1H1 bond. However, the unsymmetrical substitution pattern does not significantly affect the C-N bonds of the pyrrole ring system.

Supramolecular features
In the crystal packing of (I), the N-phenylpyrrole moieties are directed along [101] with alternating directions for adjacent rows (Fig. 2). The bent shape caused by the 3-substitution pattern furthermore results in a corrugated arrangement of the molecules along [001] (Fig. 3). Interestingly, no remarkable intra-or intermolecular interactions, e.g. in the form of interactions, are observed. Therefore it appears that the crystal packing is mainly dominated by van der Waals forces.
However, a single substituted pyrrole bearing just one ferrocenyl substituent in the 3-position has not been reported so far. It should be noted that related structures like 3-ferrocenyl maleimides (Mathur et al., 2012) and a 3-ferrocenyl boron-dipyrromethene (Dhokale et al., 2013) are reported bearing one ferrocenyl substituent.
The smallest intersection between the phenyl and pyrrole rings are reported with 5.4 for a 3-ferrocenyl-pyrrolo[1,2-a]quinoxaline (Guillon et al., 2011), due to the hindered rotation of the N-C Ph bond. However, comparable derivatives with free rotable N-aromatics exhibit torsions above 35 (Hildebrandt et al., 2012). The molecular structure of (I), with displacement ellipsoids drawn at the 50% probability level. All H atoms have been omitted for clarity.

Figure 2
Packing of the molecules in the crystal structure of (I) in a view along [010]. All H atoms have been omitted for clarity.

Figure 3
Packing of the molecules in the crystal structure of (I) resulting in a wavetype arrangement along [001]. All H atoms have been omitted for clarity.
Synthesis of (I): Ferrocene (0.35 g, 1.88 mmol) and 0.125 eq of KO t Bu (0.03 g, 0.23 mmol) were dissolved in 20 ml of tetrahydrofuran and the respective solution was cooled to 193 K. Afterwards, 2 eq of t butyllithium (2.4 ml, 3.76 mmol, 1.6 M in n pentane) were added dropwise via a syringe and the reaction solution was stirred for 1 h. Then, 1 eq of [ZnCl 2 Á2thf] (0.53 g, 1.88 mmol) was added in a single portion. The reaction mixture was stirred for additional 30 min at 273 K. Afterwards, 0.25 mol-% of [Pd(CH 2 C(CH 3 ) 2 P( t C 4 H 9 ) 2 )(-Cl)] 2 (3.2 mg, 0.47 mmol) and 3-bromo-N-phenylpyrrole (0.27 g, 1.24 mmol) were added in a single portion and stirring was continued overnight at 333-343 K. After evaporation of all volatiles, the crude product was worked-up by column chromatography (silica, column size: 1.5 x 10 cm) using an n-hexane/diethyl ether mixture (ratio 10:1; v/v) as the eluent. The first fraction contained ferrocene, while thereafter compound (I) was eluted as an orange phase. Single crystals of (I), suitable for single crystal diffraction analysis, were obtained by slow evaporation of a saturated dichloromethane/ methanol (ratio 1:1 v/v) solution containing (I) at ambient temperature. Yield: 0.16 g (0.48 mmol, 39% based on 3-bromo-N-phenylpyrrole

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. C-bonded aromatic hydrogen atoms were placed in calculated positions and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C) and a C-H distance of 0.93 Å .  (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and SHELXTL (Sheldrick, 2008); software used to prepare material for publication: WinGX (Farrugia, 2012) and publCIF (Westrip, 2010). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.50 e Å −3 Δρ min = −0.75 e Å −3 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.