Tetrachloroplatinate(II) Anion as a Square-planar Tecton for Crystal Engineering Involving Halogen Bonding
In the X-ray structures of the 1:1 adduct of [Ph3P=N=PPh3]2[PtCl4] with 1,4- diiodotetrafluorobenzene (1·FIB) and the salt [Ph3PCH2I]2[PtCl4] (2), the tetrachloroplatinate(II) anion behaves as a halogen bond (XB)-accepting tecton toward -hole-donating organohalogen species to form either C–I···Cl–PtCl2–Cl···I–C or C–I···Cl–PtCl3 moieties, respectively. All XB contacts are clearly observed on the Hirshfeld surfaces; in addition, intermolecular contacts are visualized using the Noncovalent Interactions (NCI) analysis. The steric factor and the number of XB donor centers play important roles in the supramolecular organization of compounds 1·FIB and 2: the bifunctional FIB with two -hole donor centers forms an extended structure, including the bridging [PtCl4]2–, whereas the [Ph3PCH2I]+ cation with a -hole donor center in the sterically encumbered environment forms only one terminal XB with [PtCl4]2–. The results of the DFT calculations followed by topological analysis of the electron density distribution within the framework of the QTAIM method at the ωB97XD/DZP-DKH level of theory reveal that the energies of the attractive intermolecular noncovalent interactions are 6.3–6.4 kcal/mol for compound 1·FIB and 2.6–2.9 kcal/mol for compound 2.