[Sulfonylbis(bromomethylene)]dibenzene

The title compound crystallizes as the mesomeric isomer, which helped establish that the 1,3 elimination of bromine by triphenylphosphine occurs with inversion of configuration at each chiral carbon atom.


data reports
Bond lengths and angles in the molecular structure of 2 appear normal. As can be seen in Fig. 2, the chirality at C1 is R while that at C9 is S, indicating that this compound is the meso isomer. All molecules in this centrosymmetric crystal will be the same meso isomer, although of course half will have opposite chiralities at C1 and C9. The C1-Br1 entity is gauche with respect to S-C2, whereas C2-Br2 is trans to S-C1, with conformational angles of À58.3 (5) and 171.3 (4) , respectively.
The packing diagram (Fig. 3) shows the sulfone O atoms and the Br atoms projecting into hydrophobic areas of the crystal. A number of putative C-HÁ Á ÁO and C-HÁ Á ÁBr intermolecular hydrogen-bonding contacts are given in Table 1. The CÁ Á ÁO distances range from 3.46 (2) to 3.55 (2) Å while angles at the H atom are in the general range of 120-130 . The three CÁ Á ÁBr distances listed are longer, with a range of 3.74 (2) to 3.79 (2) Å and there is more variation in the angles at the H atoms. Intermolecular HÁ Á ÁH contacts are all greater than 2.5 Å except for H6Á Á ÁH10(x À 1 2 , y, 3 2 À z), which is 2.36 Å .

Synthesis and crystallization
Details of the synthesis of the title compound are not given in the Bordwell papers, but details of two methods of preparing the compound are given in Carpino et al. (1971).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.
In 1967, when this dataset was collected, mechanical failures were frequent enough that minimum redundancy was sought. This accounts for the low resolution of the data and the lack of symmetry-equivalents. An empirical absorption correction involving a 24-parameter fit was made with XABS2 (Parkin et al., 1995), which led to a much smoother difference-Fourier map. The H atoms attached to chiral C1 and C2 atoms were located as the two highest peaks on a difference map calculated without their contributions.
In the final refinements, the phenyl ring carbon atoms were refined as rigid groups in order to keep a reasonable ratio of observations to refined parameters. The C-C distance in the phenyl rings was set at 1.372 Å to minimize the weighted R factor. Although this distance is a little less than the average 1.39 Å usually found, a number of well-refined sulfone structures in the Cambridge Structural Database (Groom et al., 2016) have C-C distances less than 1.39 Å , see: TUXFIC02 (Eccles et al., 2011), BECRAE (Malwal & Chakrapani, 2015), GIPQON (Periasamy et al., 2013), HEXLOO (Matsumoto et al., 2018). The phenyl and H atoms attached to chiral C atoms all were constrained to lie in their expected positions, with C-H distances of 0.93 and 0.98 Å respectively, and displacement parameters set at 1.2U eq for the adjoining carbon atoms. Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
View of the title molecule showing the atomic numbering and displacement ellipsoids at the 50% probability level.

Figure 3
Projection of the crystal structure of 2 down the b axis. An arbitrary sphere size is given for C and H atoms, and a 50% probability level for the displacement ellipsoids of Br, S and O atoms. The reference molecule has Br and S atoms identified.

data-2
IUCrData (2022). 7, x211351 Refinement. After the empirical absorption correction with XABS2, a difference map based upon all of the atoms except H1 and H2 clearly revealed H1 and H2 as the two highest peaks.