1,4-Bis[4-(dimethylsilyl)phenyl]benzene

The complete molecule of the title compound, C22H26Si2, is generated by a crystallographic centre of symmetry. The central benzene ring makes a dihedral angle of 26.7 (4)° with the 4-(dimethylsilyl)phenyl ring. There are weak C—H⋯π interactions in the crystal structure.

The complete molecule of the title compound, C 22 H 26 Si 2 , is generated by a crystallographic centre of symmetry. The central benzene ring makes a dihedral angle of 26.7 (4) with the 4-(dimethylsilyl)phenyl ring. There are weak C-HÁ Á Á interactions in the crystal structure.
The title molecules are situated on the crystallographic centres of symmetry ( Fig. 1). Two dimethylsilylphenyl-rings are linked to the central benzene ring in its 1,4 (para) positions. The rings are not coplanar; the dihedral angle between the dimethylsilylphenyl-ring and the central benzene ring equals to 26.7 (4)°. There are C-H···π-electron ring interactions in the structure (Tab. 1).
The distance Si1-H1 (1.39 (3)Å) is in a fair accordance to the structures with the R-factor < 0.06 that have been retrieved from the Cambridge Crystallographic Database (version 5.31 from December 2009 with updates up to February 2010). (Allen, 2002). The average retrieved distance is 1.419 (14) Å for 21 observations. [The searched structures contained Sifragment as it is in the title structure: 2 C atoms in sp 3 state, 1 in sp 2 state, 1 H. The structures with extensively deviated distances (ROLDIF, ROLDIF01, POZNEX, CODVOH, YOYBOD) have been suppressed.]

Experimental
The reaction scheme is shown in Fig. 2. A solution of n-BuLi in hexane (1.6 M, 0.88 ml) was added dropwise to a solution of 1,4-bis(4-iodophenyl)benzene (192 mg, 0.40 mmol) in anhydrous tetrahydrofuran (THF) (80 ml) at -78 °C. After the solution having been stirred for 1 h, dimethylchlorosilane (152 mg, 1.60 mmol), also cooled to the same temperature, was added by syringe. The mixture was allowed to warm to room temperature and it was stirred overnight. After it had been 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 recrystallized from ethanol to give 92 mg of the title product in 67% yield. The crystals were colourless needles with the average length of about 3 mm.

Refinement
All the hydrogens were discernible in the difference electron density maps. Nevertheless, all the hydrogens except the hydrogen attached to Si that was refined freely, were constrained by the riding-hydrogen formalism with U iso (H)=1.2U eq (C aryl ) or U iso (H)=1.5U eq (C methyl ). The C-H distances were constrained to 0.95 and 0.98 Å for the aryl and the methyl hydrogens, respectively.
supplementary materials sup-2 Figures   Fig. 1. The title molecule, showing 50% probability displacement ellipsoids and the atomnumbering scheme. The atoms without labels are related to the labelled ones by -x, -y+1, -z+2.

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 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 > 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.