Metal-involving halogen bonding was detected in a series of associates of CHI ₃ with trans -[PtX ₂ (NCNAlk ₂ ) ₂ ] (X = Cl, Br).

Iodopentafluorobenzene (IPFB or Ph^FI) was co-crystallized with tetra(n-butyl)ammonium tetraiodo-μ,μ′-diiododiplatinate(II), [n-Bu₄N]₂[Pt₂(μ-I₂)I₄] (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.

This review highlights recent studies discovering unconventional halogen bonding (HaB) that involves positively charged metal centers. These centers provide their filled d‐orbitals for HaB, and thus behave as nucleophilic components toward the noncovalent interaction. This role of some electron‐rich transition metal centers can be considered an oxymoron in the sense that the metal is, in most cases, formally cationic; consequently, its electron donor function is unexpected. The importance of Ha⋅⋅⋅d‐[M] (Ha=halogen; M is Group 9 (Rh, Ir), 10 (Ni, Pd, Pt), or 11 (Cu, Au)) interactions in crystal engineering is emphasized by showing remarkable examples (reported and uncovered by our processing of the Cambridge Structural Database), where this Ha⋅⋅⋅d‐[M] directional interaction guides the formation of solid supramolecular assemblies of different dimensionalities.