Diaryliodonium Tetracyanidometallates Self-Assemble into Halogen-Bonded Square-Like Arrays

Two diphenyliodonium tetracyanidometallates, [Ph2I](2)[M(CN)(4)] (M = Ni and Pd), were prepared through anion metathesis. Their X-ray structural analyses show that the structure-defining contact for both crystals is the charge-assisted I center dot center dot center dot N halogen bond (HaB) formed between the I atom of the iodonium cations and the N atoms of the CN- ligands. These HaBs assemble the bidentate and 90 degrees-orienting HaB donor Ph2I+ and the tetradentate, square planar, and 90/180 degrees-orienting HaB acceptors [M(CN)(4)](2-) into supramolecular rectangles, which further assemble into infinite chains by sharing the vertexes occupied by the [M(CN)(4)](2-) anions. The noncovalent nature of these contacts was confirmed by density functional theory calculations (M06/def2-TZVP) followed by combined topological analysis of the electron density distribution in the quantum theory of the atoms-in-molecules approach and noncovalent interaction analysis. The philicities of the HaB partners were further verified by the analysis of electron localization function projections, electron density/electrostatic potential profiles along the I center dot center dot center dot N bond paths, natural bond orbital analysis, and the natural population analysis or atoms-in-molecules charge sums in model systems.