2-Dichloromethyl-N-ethyl-5-(1-phenylsilolan-1-yl)cyclopent-3-enecarboxamide

In the title compound, C19H25Cl2NOSi, the NH group and the carbonyl O atom of the amide fragment are involved in an intermolecular N—H⋯O hydrogen bond forming chains of molecules. The plane of the benzene ring forms a dihedral angle of 50.5 (2)° with respect to the silolane ring and an angle of 49.74 (2)° with the cyclopentyl moiety.


Comment
It is well known that some silicon-containing compounds show extremely high biological activity, e.g. silatranes, which are much more toxic than strychnine (Tacke & Wannagat, 1975, 1979Voronkov, 1979). In recent years, people have reported that the reaction of diphenyldichlorosilane with magnesium and butadiene yields silacyclopentenes, which are thought to be formed via a diphenylsilylene intermediate (Matthews et al., 2001(Matthews et al., , 2002. As part of this work, we synthesized the title compound derived from 1-(cyclopenta-2,4-dienyl)-1-phenylsilolane (CDP), and its structure is reported here..
The compound crystallized with a structural configuration in which the phenyl ring (C1~C6) forms a dihedral angle of 50.5 (2)° with respect to the silolane ring (C7,C8,C9,C10,Si1). The cyclopentene ring (C11~C15) is almost planar with the largest deviation being 0.074 Å for atom C15. The bond length of C12-C13 (1.294 (6) Å), agrees with the value characteristic of a double bond. in general bond lengths (Allen et al., 1987) and angles are within normal ranges. In the crystal structure, there one intermolecular hydrogen bond (N1-H1···O1) is observed.

Experimental
1-(cyclopenta-2,4-dienyl)-1-phenylsilolane (CDP) was synthesized according to the method reported by Benkeser et al. (1962). 0.5 mol of CDP was dissolved in 20 ml n-hexane and 20 ml triethylamine in a 200 ml round flask. At 0°C 0.6 mol of 2, 2-dichloroacetyl chloride was added to the flask in 30 min. After continually stirring for 1 h, the solvent was removed and the residue was fractionated on a Todd-column (yield: 31.7%). Colourless block-shaped and needlelike crystals were obtained by slow evaporation of the solution in methanol. Colourless block-shaped single crystals suitable for X-ray structure determination were picked up and determined while the needlelike crystals were too thin to perform an X-ray diffraction experiment. Acoording to elemental analysis, colourless block-shaped and needlelike crystals show an identical composition and are therefore considered to be diastereoisomeric forms of the title compound.

Refinement
All H atoms were placed in calculated positions, with C-H = 0.93 Å for phenyl, 0.96 Å for methyl, 0.97 Å for methylene and 0.98 Å for methine H atoms, and refined as riding, with U iso (H) = 1.2 U eq (C) for phenyl, methylene and methine H, and 1.5 U eq (C) for methyl H atoms.  Molecular structure of the title compound with thermal ellipsoids shown at the 30% probability levels).

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 0.94858 (13