A Silica-Supported Monoalkylated Tungsten Dioxo Complex Catalyst for Olefin Metathesis

A well-defined silica-supported monoalkylated tungsten dioxo complex [(≡Si–O−)W(═O)2(CH2–tBu)] was prepared by treatment of highly dehydroxylated silica (SiO2-700: silica treated at 700 °C under high vacuum) with an ionic precursor complex [NEt4][W(═O)3(CH2–tBu)]. The identity of the resulting neutral monoalkylated tungsten dioxo surface complex was established by means of elemental microanalysis and spectroscopic studies (IR, solid-state NMR, Raman, and X-ray absorption spectroscopies). The supported tungsten complex was found to act as a precatalyst for the self-metathesis of 1-octene in a batch reactor. The mechanistic implications of this reaction are discussed with the support of DFT calculations highlighting the potential occurrence of thus-far unexplored mechanistic pathways.