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 center dot FIB) and the salt [Ph3PCH2I](2)[PtCl4] (2), the tetrachloroplatinate.II) anion behaves as a halogen bond (XB)-accepting tecton toward s-hole-donating organohalogen species to form either C-I center dot center dot center dot Cl-PtCl2-Cl center dot center dot center dot I-C or C-I center dot center dot center dot Cl-PtCl3 moieties, respectively. All XB contacts are clearly observed on the Hirshfeld surfaces; in addition, intermolecular contacts are visualized using noncovalent interactions (NCI) analysis. The steric factor and the number of XB donor centers play important roles in the supramolecular organization of compounds 1 center dot FIB and 2: the bifunctional FIB with two s-hole donor centers forms an extended structure, including the bridging [PtCl4](2-), whereas the [Ph3PCH2I](+) cation with a sigma-hole donor center in a sterically encumbered environment forms only one terminal XB with [PtCl4](2-). The results of DFT calculations followed by topological analysis of the electron density distribution within the framework of the QTAIM method at the omega B97XD/DZP-DKH level of theory reveal that the energies of the attractive intermolecular noncovalent interactions are 6.3-6.4 kcal mol-1 for compound 1 center dot FIB and 2.6-2.9 kcal mol(-1) for compound 2.