Recognition of the π-hole donor ability of iodopentafluorobenzene – a conventional σ-hole donor for crystal engineering involving halogen bonding

Iodopentafluorobenzene (IPFB or Ph F I) was co-crystallized with tetra( n -butyl)ammonium tetraiodo-μ,μ′-diiododiplatinate( ii ), [ n -Bu 4 N] 2 [Pt 2 (μ-I 2 )I 4 ] ( 1 ), to give the adduct 1 ·2IPFB. The XRD experiment revealed that 1 ·2IPFB displays previously unreported C⋯I–Pt anion–π interactions formed along with the expected Ph F –I⋯I–Pt II halogen bond (XB); these two interactions join two complexes and two IPFBs in a heterotetrameric cluster. Processing of the available CSD data revealed only one structure (CSD code: IKIYAE) with a heterotetrameric cluster bearing simultaneous two Ph F –I⋯X (X = I–Pt IV , N) XBs and C⋯I lp(I)–π contacts between the two IPFBs. Results of the DFT calculations (M06/DZP-DKH level of theory) followed by the topological analysis of the electron density distribution within the framework of Bader's approach (QTAIM) for both 1 ·2IPFB and IKIYAE confirmed the availability of these (anion/lp)–π weak interactions. The estimated energies of the observed (anion/lp)–π and XBs contacts are in the 0.9–1.3 kcal mol −1 and 1.3–5.3 kcal mol −1 ranges, respectively. π-Hole donor ability of IPFB was additionally confirmed by theoretical calculations of the molecular surface electrostatic potential for the optimized equilibrium structure of IPFB.