Zirconium-Catalyzed C-H Alumination of Polyolefins, Paraffins, and Methane

C-H/Et-Al exchange in zirconium-catalyzed reactions of saturated hydrocarbons and AlEt₃ affords versatile organoaluminum compounds and ethane. The grafting of commercially available Zr(OtBu)₄ on silica/alumina gives monopodal ≡SiO-Zr(OtBu)₃ surface pre-catalyst sites that are activated in situ by ligand exchange with AlEt₃. The catalytic C-H alumination of dodecane at 150 °C followed by quenching in air affords n-dodecanol as the major product, revealing selectivity for methyl group activation. Shorter hydrocarbon or alcohol products were not detected under these conditions. Catalytic reactions of cyclooctane and AlEt₃, however, afford ring-opened products, indicating that C-C bond cleavage occurs readily in methyl group-free reactants. This selectivity for methyl group alumination enables the C-H alumination of polyethylenes, polypropylene, polystyrene, and poly-α-olefin oils without significant chain deconstruction. In addition, the smallest hydrocarbon, methane, undergoes selective mono-alumination under solvent-free catalytic conditions, providing a direct route to Al-Me species.