Crystal structure of tetraethylammonium chloride 3,4,5,6-tetrafluoro-1,2-diiodobenzene

Equimolar quantities of tetraethylammonium chloride (Et4NCl) and 3,4,5,6-tetrafluoro-1,2-diiodobenzene (o-DITFB or o-C6F4I2) have been co-crystallized in a solution of dichloromethane yielding a pure halogen-bonded compound, 3,4,5,6-tetrafluoro-1,2-diiodobenzene–tetraethyl ammonium chloride (2/1), Et4N+·Cl−·2C6F4I2, in the form of translucent needles. [(Et4NCl)(o-C6F4I2)2] packs in the C2/c space group. The asymmetric unit includes one molecule of DITFB, one Et4N+ cation located on a twofold rotation axis, and one chloride anion also located on a twofold rotation symmetry axis. This compound has an interesting halogen-bonding environment surrounding the halide. Here, the chloride anion acts as a tetradentate halogen bond acceptor and forms a distorted square-pyramidal geometry, with I⋯Cl−⋯I angles of 80.891 (6) and 78.811 (11)°, where two crystallographically distinct iodine atoms form halogen bonds with the chloride anion. Resulting from that square-pyramidal geometry are short contacts between some of the adjacent F atoms. Along the b axis, the halogen-bonding interaction results in a polymeric network, producing a sheet in which the two closest chloride ions are 7.8931 (6) Å apart. The Et4N+ cation alternates in columns with the halide ion. The expected short contacts (shorter than the sum of their van der Waals radii) are observed for the halogen bonds [3.2191 (2) and 3.2968 (2) Å], as well as almost linear angles [170.953 (6) and 173.529 (6)°].

Data collection: APEX2 (Bruker, 2009); cell refinement: APEX2 and SAINT (Bruker, 2009); data reduction: SAINT and XPREP (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.  (Bruker, 2009). Diffraction data were collected with a sequence of 0.3° ω scans at 0, 120, and 240° in φ. Due to lower symmetry in order to ensure adequate data completeness and redundancy the initial unit cell parameters were determined from 60 data frames with 0.3° ω scan each collected at the different sections of the Ewald sphere. Semiempirical absorption corrections based on equivalent reflections were applied.

S2. Refinement details
Systematic absences in the diffraction data set and unit cell parameters were consistent with the monoclinic C2/c (No.15) space group for [(Et 4 NCl)(o-C 6 F 4 I 2 )]. The solution in the centrosymmetric space group yielded chemically reasonable and computationally stable results of refinement. The structure was solved by direct methods, completed with difference Fourier synthesis, and refined with full-matrix least-squares procedures based on F 2 .
The structural model for [(Et 4 NCl)(o-C 6 F 4 I 2 )] contains one ammonium cation and one chlorine atom located on two different two-fold axis symmetry elements of the space group while aromatic molecules are located in general positions.
In this structural model, the hydrogen atom positions were located from the differences in Fourier maps. However, after initial positioning, all hydrogen atomic positions were constrained to suitable geometries and subsequently treated as idealized contributions. All scattering factors are contained in several versions of the SHELXTL program library, with the latest version used being v.6.12 (Sheldrick, 2008

Special details
Experimental. Data collection is performed with three batch runs at phi = 0.00 ° (650 frames), at phi = 120.00 ° (650 frames), and at phi = 240.00 ° (650 frames). Frame width = 0.30 ° in omega. Data is merged, corrected for decay (if any), and treated with multi-scan absorption corrections (if required). All symmetry-equivalent reflections are merged for centrosymmetric data. Friedel pairs are not merged for noncentrosymmetric data. 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.