Isostructural Molecular and Surface Mimics of the Active Sites of the Industrial WO₃/SiO₂ Metathesis Catalysts

In classical, ill-defined WO₃/SiO₂ alkene metathesis catalysts, isolated, silica-supported tungsten oxo alkylidene species are suspected to represent the catalytically active species. Here, we report the synthesis and the characterization of molecular and supported isostructural mimics of these active sites. The good activities at room temperature of these well-defined oxo alkylidene complexes indicate that the lower activity of WO₃/SiO₂, even after preactivation, is likely due to the difficulty to generate active alkylidene sites from W oxo species in the classical system.