Chameleonic metal-bound isocyanides: a π-donating CuI-center imparts nucleophilicity to the isocyanide carbon toward halogen bonding

In the structures of the isostructural cocrystals [CuI3(CNXyl)(3)]center dot CHX3 (X = Br, I), two adjacent Cu-I-bound isocyanide groups, whose carbon lone pairs are blocked by ligation, exhibit nucleophilic properties induced by a pi-donating d(10)[Cu-I] center and function as an integrated two-center halogen bond acceptor forming bifurcated mu(2)-XMIDLINE HORIZONTAL ELLIPSIS(C,C) halogen bonds. This bonding includes the electronegative regions of the two isocyanide ligands and a sigma-hole of an X center of CHX3 and it is not supported by any attractive XMIDLINE HORIZONTAL ELLIPSISCu interactions. The true halogen bonding nature of the mu(2)-XMIDLINE HORIZONTAL ELLIPSIS(C_-Cu-C_) contacts was confirmed theoretically by DFT calculations using several computational tools (QTAIM, NCIplot, IRIPlot and IGMPlot indexes, MEP surfaces, ELF analysis, and electron density/electrostatic potential plots). Noncovalent interaction patterns of CNR ligands and also their metal-dependent chameleonic behavior toward noncovalent interactions were analyzed, considering the electronic properties of coordinating metal centers.

Automated summary

In the isostructural cocrystals [CuI3(CNXyl)(3)]center dot CHX3 (X = Br, I), the blocked carbon lone pairs of the adjacent Cu-I-bound isocyanide groups exhibit nucleophilic properties induced by a pi-donating d(10)[Cu-I] center and form bifurcated halogen bonds with the sigma-hole of an X center of CHX3. This halogen bonding is not supported by any attractive XMIDLINE HORIZONTAL ELLIPSISCu interactions. The true halogen bonding nature of the contacts was confirmed theoretically by DFT calculations using multiple computational tools.