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.