1,4-Bis(dimethylsilyl)-2,5-diphenylbenzene

The molecule of the title compound, C22H26Si2, is centrosymmetric. The dihedral angle between the central benzene ring and its phenyl substituents is 67.7 (2)°. The crystal packing is stabilized by van der Waals forces.

The molecule of the title compound, C 22 H 26 Si 2 , is centrosymmetric. The dihedral angle between the central benzene ring and its phenyl substituents is 67.7 (2) . The crystal packing is stabilized by van der Waals forces.

Comment
As part of our ongoing investigation on the effect of silyl substituents on the photophysics of p-terphenyls, we present the title compound bearing silyl substituents at the central phenyl ring (2,5-positions). Though analogues of the title compound were reported elsewhere (Feng et al., 2007), their structures were not fully studied. The molecular structure of the title compound is shown in Fig.1. It is centrosymmetric, the centroid of the central benzene ring is located on an inversion center at 0,1,0. The dihedral angle between the benzene ring and phenyl substituents is 67.7 (2)°. The crystal packing is mainly stabilized by van der Waals forces.

Experimental
A solution of 2,5-dibromo-1,4-diphenylbenzene (120 mg, 0.31 mmol) in anhydrous THF (10 ml) was added dropwise to a hexane solution of n-BuLi (2.5 M, 0.44 ml, 1.08 mmol) dropwise at -78 °C. The reaction mixture was stirred for 1 h and dimethylchlorosilane (118 mg, 1.24 mmol) was added via syringe at the same temperature and the mixture was allowed to warm to room temperature and stirred overnight. After being quenched with saturated NaHCO 3 solution, the mixture was extracted with Et 2 O. The organic layer was washed with brine, dried over anhydrous MgSO 4 , filtered, and concentrated under reduced pressure. The mixture was passed through a silica gel column with hexane as an eluent, followed by further purification by recrystallization from ethanol to give 98 mg of the white product in 91% yield.

Refinement
All H-atoms were located in electron-density difference maps. Carbon-bound H atoms were placed geometrically in idealized positions and refined using a riding model with C-H (methyl) 0.98, C-H (aromatic) 0.95 Å and with U iso (H) =1.2U eq (C).
Located in the electron-density difference map H atom from the silyl group was refined using riding model with U iso (H) =1.2U eq (Si). Fig. 1. The structure of the title compound showing 50% probability displacement ellipsoids and the atom-numbering scheme. The unlabelled atoms can be generated by the symmetry operation -x, -y+2, -z.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds supplementary materials sup-3 in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2σ(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.