Tetraphenylphosphonium iodide–1,3,5-trifluoro-2,4,6-triiodobenzene–methanol (3/4/1)

The crystallization of a 1:1 molar solution of 1,3,5-trifluoro-2,4,6- diiodobenzene (TFTIB) and tetraphenylphosponium iodide (TPPI) from methanol produced tetragonal needles of pure TPPI and tabular pseudo-hexagonal truncated bipyramids of the title compound, 3C24H20P +·3I-·4C6F3I3· CH4O or (TPPI)3(TFTIB)4·MeOH. The asymmetric unit is composed of six TPPI molecules, eight TFTIB molecules and two methanol molecules, overall 16 constituents. The formation of the architecture is essentially guided by a number of C - I⋯I- halogen bonds (XB), whose lengths are in the range 3.276 (1)-3.625 (1) Å. Layers of supramolecular polyanions are formed parallel to (10-1) wherein iodide anions function as penta-, tetra- or bidentate XB acceptors. The structure is not far from being P21/n, but the centrosymmetry is lost due to a different conformation of a single couple of cations and the small asymmetry in the formed supramolecular anion. One methanol molecule is hydrogen bonded to an iodide anion, while the second is linked to the first one via an O - H⋯O contact. This second methanol molecule is more loosely pinned in its position than the first and presents very high anisotropic displacement parameters and a seeming shortening of the C - O bond length. The crystal studied was refined as a perfect inversion twin. © Cavallo et al. 2013