Wolfium Bond Catalysis: Electronic Reprogramming and Transition State Stabilization in Aza-Diels-Alder Reactions

The catalytic potential of wolfium bonds, a σ-hole interaction involving Group 6 elements, remains largely unexplored. Herein, we present a systematic theoretical investigation into the mechanism of wolfium bond donors (WnF₄O, Wn = Cr, Mo, W) as catalysts for the aza-Diels-Alder reaction between imine and 1,3-butadiene. Computations performed at the ωB97XD/aug-cc-pVTZ level reveal that these catalysts function via a prestabilization mechanism, forming strong wolfium bonds with the imine reactant. This interaction not only significantly lowers the apparent activation barrier but also reprograms the reaction pathway toward an asynchronous, charge-separated transition state. Catalytic efficiency follows the order Cr < Mo < W, which originates from the enhanced electrostatic and polarization components of the wolfium bond with increasing metal electronegativity and polarizability. Energy decomposition and AIM analyses confirm the electrostatic-dominated, partially covalent nature of these interactions. Crucially, solvent effect studies identify WF₄O as an effective modulator of the reaction pathway in both nonpolar and polar media. Compared to conventional hydrogen and halogen bonds, wolfium bonds exhibit a more pronounced ability to regulate the reaction mechanism, offering a new perspective on the role of noncovalent interactions in pericyclic reactions.