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

The title compound, C25H26N2Te, was synthesized from bis[1,3-bis(3-phenylpropyl)benzimidazolidin-2-ylidene] and Te in a toluene solution. The molecule possesses a twofold rotation axis passing through the Te atom and the center of the benzimidazole ring system. The benzimidazole ring system makes an angle of 67.9 (4)° with the phenyl rings.

The title compound, C 25 H 26 N 2 Te, was synthesized from bis[1,3-bis(3-phenylpropyl)benzimidazolidin-2-ylidene] and Te in a toluene solution. The molecule possesses a twofold rotation axis passing through the Te atom and the center of the benzimidazole ring system. The benzimidazole ring system makes an angle of 67.9 (4) with the phenyl rings.  Sadekov et al. (1998); Singh et al. (2006).  (Lappert, 1988). It is known that the ultimate oxidation products of electron-rich olefins with air are ureas; sulfur and selenium react similarly to form the corresponding analogues (Roeterdink et al., 1983;Lappert et al., 1980). The conversion of an electron-rich olefin into a tellurourea has a parallel in these known olefin reactions (Lappert et al., 1980). There are extensive studies of cyclic ureas containing imidazolidine groups, including their X-ray crystal structures. However, there is no example of an X-ray crystal structure study for the cyclic tellurourea containing a benzimidazole group. The objective of this study was to elucidate the first crystal structure of such a cyclic tellurourea and compare the results to the corresponding analogues contain sulfur (İngeç et al., 1999) and selenium (Aydın et al., 1999;Akkurt et al., 2004a).

Experimental
The molecular structure of the title compound (I) is shown in Fig. 1. The molecule has a twofold screw axis through the midpoints of the C2-C2a and C4-C4a bonds and containing the atoms Te1 and C1 of the benzimidazole ring. The Te-C single bond length generally varies between 2.120 and 2.170 Å depending on the electron releasing effect of the ligand bonding to Te atom (Lappert et al., 1980;Sadekov et al., 1998;Närhi et al., 2004;Singh et al., 2006). In the title compound (I), the Te-C bond length [2.058 (4) Å] is short, which agrees with the results reported by Lappert et al. (1980). Tellurourea metal complexes may be described in terms of the resonance hybrids as shown in the scheme 2. For this reason, the Te═C bond may have partial double bond character.

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 R-factors 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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq