1,3-Bis(3-phenylpropyl)-1H-1,3-benzimidazole-2(3H)-selone

The title molecule, C25H26N2Se, has mirror symmetry, with the mirror plane passing through the atoms of the C=Se bond and the mid-points of the two C—C bonds of the benzene ring of the benzimidazole group. The dihedral angle between the benzimidazole ring system and the phenyl ring is 71.62 (14)°.

The title molecule, C 25 H 26 N 2 Se, has mirror symmetry, with the mirror plane passing through the atoms of the C Se bond and the mid-points of the two C-C bonds of the benzene ring of the benzimidazole group. The dihedral angle between the benzimidazole ring system and the phenyl ring is 71.62 (14) .   Electron-rich olefins (EROs) have been attracted considerable attention in both organic and inorganic preparative literature due to their unique properties as reagent and reaction intermediates since their first report by Wanzlick in 1960(Wanzlick & Schikora, 1960Böhm & Herrmann, 2000).

Experimental
Benzimidazolium salts are convenient precursors for EROs through reacting with a strong base such as NaH comparing with other methods such as reacting a secondary amine (N,N'-disubstituted-1,2-diaminobenzene) with an acetal, chloral or triethyl orthoformate. We have synthesized and isolated first time the ERO, bis(1,3-dimethybenzimidazolidine-2-ylidene) (Çetinkaya et al., 1994). We have also synthesized a number of EROs using different synthesis methods and used them to synthesize many organic or organometallic compounds (Küçükbay et al., 1996, Küçükbay et al., 1997, Çetinkaya et al., 1998Aydın et al., 1998Yıldırım et al., 2006Yılmaz & Küçükbay, 2009). Their electron-richness confers on them a very high reactivity as strong nucleophiles, which assist in the preparation of numerous products by reaction, amongst others, with group 16 elements, transition metals, and many protic compounds (Lappert et al., 2009). It is known that the ultimate oxidation product of EROs with air is urea; sulfur, selenium and tellurium react similarly to give the corresponding analogues. The objective of the present study was to elucidate the crystal structure of the title compound which is new ERO derivative.
supplementary materials sup-2 Refinement All H atoms were positioned geometrically with C-H = 0.93-0.97 Å, and refined using a riding model with U iso (H) = 1.2U eq (C). The absolute configuration of the title compound was established by refinement of the Flack (1983) parameter.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and tor-

sion angles
Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.