Tetrachloroplatinate(ii) anion as a square-planar tecton for crystal engineering involving halogen bonding

Abstract

In the X-ray structures of the 1 : 1 adduct of [Ph3PNPPh3]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 σ-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 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 σ-hole donor centers forms an extended structure, including the bridging [PtCl4]2-, whereas the [Ph3PCH2I]+ cation with a σ-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 ωB97XD/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·FIB and 2.6-2.9 kcal mol-1 for compound 2. This journal is