Nucleophilicity\nof the Nitrile N Atom Whose Lone Pair\nIs Blocked by Metal Coordination. The π‑Hole Interaction\nbetween an Arene Carbon and the Metal-Bound Nitrile Nitrogen

Cocrystallization of CuI with NCNMe<sub>2</sub> in the\npresence\nof substituted perfluoroarenesiodoperfluorobenzene (IFB),\n4,4′-diiodoperfluorobiphenyl (4,4′-FIBP), and 4-bromoperfluorobenzonitrile\n(4-BrFBN)led to the formation of three types of adducts <b>1</b>·2(IFB), <b>1</b>·4,4’FIBP, and <b>1</b>·4-BrFBN (<b>1</b> is Cu<sub>4</sub>I<sub>4</sub>(NCNMe<sub>2</sub>)<sub>4</sub>), all studied by X-ray crystallography.\nIn these cocrystals, the coordinated nitrile N atom (whose electron\npair is engaged in metal coordination) still acts as an electron donor,\nforming π-hole interactions, specifically, π-hole<sub>arene</sub>···N<sub>nitrile</sub>, with the perfluoroarenes.\nThese interactions were examined in the context of their occurrence\nalongside other interactions involving C atoms of the electron-deficient\naromatic rings and nucleophilic atoms of the copper cluster. Comprehensive\ntheoretical calculations, including MEP, QTAIM/NCI plot analysis,\nEDA, ELF projections, and ETS-NOCV calculations, revealed that the\nnitrile ligand N atom maintains significant negative potential and\nthat π-hole interactions are energetically more favorable than\nσ-hole interactions in the studied systems. This nucleophilicity\nis based on a noticeable contribution of the heterocumulene form,\nCu–N<sup>–</sup>CN<sup>+</sup>Me<sub>2</sub>, in the resonance hybrid of Cu-bound NCNMe<sub>2</sub>: a\nphenomenon influenced by both the coordination and the conjugation\nbetween the NR<sub>2</sub> and CN groups The discovery of π-hole<sub>arene</sub>···N<sub>nitrile</sub> contacts adds a\nnew dimension to our understanding of coordinated push–pull\nnitriles, in particular dialkylcyanamides, revealing that the coordinated\nnitrile N atom can still function as a nucleophile in noncovalent\nbinding.