Wolfium Bonds with π Systems as Electron Donors

The term "wolfium bond" is employed to denote attractive interactions between group 6 elements and electron-rich moieties. A theoretical investigation of the wolfium bond involving the compounds WnF₄O or WnF₂O, where Wn represents Cr, Mo or W, and π systems such as C₂H₂, C₂H₄ and C₆H₆, was conducted using density functional theory (DFT) at the ωB97XD/aug-cc-pVTZ level of theory. Interaction energies range from -3.74 to -10.86 kcal/mol upon formation of the π-Wn bond. The electrostatic contributions to the interaction energy were found to be dominant. Notably, the WnF₄O system exhibits greater stability than its WnF₂O counterpart, with the exception of the CrF_xO system. The charge transfer between the interacting molecules lies between 0.0114 and 0.0946e in magnitude. The predominant type of orbital interaction is π_C-C→BD*_Wn-O. Our theoretical investigation revealed the presence of weak, but significant, wolfium bonds between group 6 elements and electron-rich π systems.