Metal-induced Enhancement of Tetrel Bonding. The Case of C···X-IrIII (X = Cl, Br) Tetrel Bond Involving a Methyl Group.

In X-ray structures of the isomorphic mer-[IrX3(THT)(CNXyl)2] (X = Cl 1, Br 2; THT = tetrahydrothiophene; Xyl = 2,6-Me2C6H3-) complexes, we revealed short intermolecular contacts between the C-atom of an isocyanide methyl group and halide ligands of another molecule. Geometrical consideration of the X-ray data and analysis of appropriate DFT studies allowed the attribution of these contacts to CMe···X-IrIII (X = Cl, Br) tetrel bond. Specifically, through the application of DFT calculations and various theoretical models, the presence of tetrel bonding interactions was validated, and the contribution of the CMe···X-IrIII interaction was assessed. The reinforcement of the tetrel bond upon the isocyanide coordination to iridium(III) is substantiated by molecular electrostatic potential (MEP) surface calculations. To distinguish the tetrel bonding characteristics of CMe···X-IrIII (X = Cl, Br) interactions from conventional hydrogen bonding, we employed multiple computational methodologies, including Natural Bond Orbital (NBO) analysis and Electron Localization Function (ELF) analysis. Additionally, Energy Decomposition Analysis (EDA) was applied to selected model systems to explore the underlying physical nature of these interactions.