Reversible C–H Bond Activation of Unactivated Arenes by a Nickel-Silylene Complex

A nickel-silylene complex is shown to reversibly activate benzene via C–H bond activation at ambient temperature. The benzene C–H bond formally adds across the Ni–Si core to form a nickel-silyl complex with an H–Si–Ni–Ph linkage bearing a highly covalent Ni–Si bond (2.2363(6) Å). Dissolution of this product in neat arene solvent, e.g., toluene, trifluorotoluene, or anisole, resulted in the complete conversion to the aryl C–H activated product of the solvent and, thereby, demonstrates the facile reversibility of C–H bond activation across the Ni–Si core. The various arene C–H bond activations by the reactive Ni(0)-silylene species were investigated using density functional theory calculations. In all cases, the arene initially forms an η2-adduct to Ni(0), and then C–H activation proceeds via a concerted oxidative addition at only the Ni center. The Si center assists C–H bond activation by sharing the redox burden with Ni while stabilizing the resultant hydride.