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

This study discovered a novel mechanism for the formation of bifurcated mu(2)-XMIDLINE HORIZONTAL ELLIPSIS(C,C) halogen bonds, induced by the nucleophilic properties of two Cu-I-bound isocyanide groups. The theoretical calculations further confirmed the nature of this bonding.