2-[(Cyclopenta-1,3-dien-2-yl)diphenylmethyl]-1-methyl-1H-imidazole

The title compound, C22H20N2, (Ib), forms along with 2-[(cyclopenta-1,3-dien-1-yl)diphenylmethyl]-1-methyl-1H-imidazole, (Ia), which differs with respect to the position of the double-bonds in the C5H5 ring, in an approximately 3:7 ratio (Ia:Ib; NMR spectroscopy data). However, in a single crystal, only compound (Ib) is present. H atoms of the CH2 group (C5H5 ring) were found from the difference Fourier synthesis and refined isotropically using the riding model. Hypothesis on possible presence of the (Ia) isomer in crystal lattice (model with a C5H5 ring disordered between two positions) was especially checked and rejected due to its inconsistency. In the crystal structure, no significant hydrogen-bonding interactions between the CH2 groups of the C5H5 rings and nonsubstituted N-atoms of the imidazole rings were observed. Despite the fact that the chemically achiral compound (I) crystallizes in a chiral space group P212121, neither the absolute structure determination nor assignment of the inversion twinning was possible in the absence of a heavy atom.

The title compound, C 22 H 20 N 2 , (Ib), forms along with 2-[(cyclopenta-1,3-dien-1-yl)diphenylmethyl]-1-methyl-1Himidazole, (Ia), which differs with respect to the position of the double-bonds in the C 5 H 5 ring, in an approximately 3:7 ratio (Ia:Ib; NMR spectroscopy data). However, in a single crystal, only compound (Ib) is present. H atoms of the CH 2 group (C 5 H 5 ring) were found from the difference Fourier synthesis and refined isotropically using the riding model. Hypothesis on possible presence of the (Ia) isomer in crystal lattice (model with a C 5 H 5 ring disordered between two positions) was especially checked and rejected due to its inconsistency. In the crystal structure, no significant hydrogenbonding interactions between the CH 2 groups of the C 5 H 5 rings and nonsubstituted N-atoms of the imidazole rings were observed. Despite the fact that the chemically achiral compound (I) crystallizes in a chiral space group P2 1 2 1 2 1 , neither the absolute structure determination nor assignment of the inversion twinning was possible in the absence of a heavy atom.
However, in a single-crystal, only compound (Ib) is present. H-atoms of the CH 2 -group (C 5 H 5 -ring) were found from the difference Fourier synthesis and refined isotropically using the riding model. Hypothesis on possible presence of the (Ia) isomer in crystal lattice (model with a C 5 H 5 -ring disordered between two positions) was especially checked and rejected due to its inconsistency. The Cp-ring is planar within 0.004 Å, with the bridging carbon C5 deviating from the r.m.s. C11 through C15 plane by 0.084 (4) Å. As for the rest of the molecule, all the bond lengths and angles are within normal ranges (see Related literature section). Both phenyl rings C21 through C26 and C31 through C36 are planar within 0.02 Å. The imidazole moiety C1/N1/C2/C3/N2/ is planar within 0.005 Å, with atoms C4 (1-methyl group) and C5 (bridging carbon atom) deviating from the imidazole ring plane by 0.091 (5) and 0.021 (4) Å, respectively. No special intermolecular contacts in the crystal lattice were observed. Despite the fact that a chemically achiral compound (I) crystallizes in a chiral space group P2 1 2 1 2 1 , neither the absolute structure determination nor approval of the inversion twinning was possible due to evident reasons (Mo-Kα radiation with no atoms heavier than nitrogen).

Experimental
All operations were performed on an Ar-vacuum line using the conventional Schlenk technique. -NMR spectra were recorded on Varian INOVA-400 instrument in CDCl 3 at 298 K. For 1 H and 13 C{ 1 H} spectra, the TMS resonances (δ H = 0.0 and δ C = 0.0) were used as internal reference standards. -Chromato-mass spectrum was measured on Agilent 6890 Series GC system equipped with HP 5973 mass-selective detector. -The elemental analysis was performed on the Vario ELIII CHNOS automated analyzer.
To a solution of 1-methyl-1H-imidazole (1.23 g, 15.0 mmol) in tetrahydrofuran (THF; 60 ml), a solution of n-BuLi in hexane (8.3 ml, 1.82 M, 15.1 mmol) was added under stirring at 195 K (acetone bath) during 30 min. The reaction mixture was stirred at the same temperature for additional 45 min, that gave a bright-yellow solution. To this slurry, a solution of 6,6-diphenylfulvene (3.45 g, 15.0 mmol) in THF (45 ml) was added dropwise during 30 min. The color of the reaction mixture turned brown. The reaction mixture was allowed to warm up gradually up to ambient temperature and the stirring was continued for the next 12 h. The mixture was quenched with water (50 ml; ice-bath cooling), the organic phase was separated, the water phase was extracted with CH 2 Cl 2 (3 × 30 ml), and the combined extracts were dried with Na 2 SO 4 .
Concentrating of the organic extracts on a rotary evaporator gave crude (I) as a brown solid. Crude (I) was refluxed with supplementary materials sup-2 Et 2 O (10 ml) cooled down to room temperature and the filtered-off solid was recrystallized from CH 2 Cl 2 -Et 2 O mixture (1.8: 10) that gave pure (I) as yellowish crystals. Yield 1.6 g, (34%  suitable for X-ray diffraction analysis was obtained by crystallization of (I) from CH 2 Cl 2 -Et 2 O mixture (1: 6 vol.)

Refinement
Non-H atoms were refined anisotropically. H atoms were treated as riding atoms with distances C-H = 0.96 (CH 3 ), 0.97 (CH 2 ), 0.93 Å (C Ar H), and U iso (H) = 1.5 U eq (C), 1.2 U eq (C), and 1.2 U eq (C), respectively. The components of the anisotropic displacement parameters (ADP-s) for C12 through C15-atoms of the C 5 H 4 -group along 1,2-and 1,3-directions were restrained to be the same with su of 0.002 Å 2 (DELU instruction). Despite the fact that an achiral compound (I) crystallizes in a chiral space group P2 1 2 1 2 1 , neither the absolute structure determination nor approval of the inversion twinning was possible due to evident reasons (Mo-Kα radiation with no atoms heavier than nitrogen). Thus, the Friedel opposites were merged and treated as equivalents. Fig. 1. A view of the molecule of compound (I). Displacement ellipsoids are shown at the 50% probability level. All H-atoms except of those in the C 5 H 5 -ring are omitted for clarity.  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 Rfactors(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.

Figures
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )