Supported Ru olefin metathesis catalysts via a thiolate tether.

Thiolate-coordinated ruthenium alkylidene complexes can give high Z-selectivity and stereoretentivity in olefin metathesis. To investigate their applicability as heterogeneous catalysts, we have successfully developed a methodology to easily immobilize prototype ruthenium alkylidenes onto hybrid mesostructured silica via a thiolate tether. In contrast, the preparation of the corresponding molecular complexes appeared very challenging in solution.

Thermal restructuring of silica-grafted TiCl(x) species and consequences for epoxidation catalysis.

TiCl4 grafted to dehydrated silica is an industrially applied catalyst for the epoxidation of propylene. As with many heterogeneous catalysts, the precise nature of the surface species is not yet fully known, prohibiting reliable structure-activity correlations. In this study, the speciation and restructuring of site-isolated Ti(IV) Lewis acid centers was carefully investigated by using a variety of techniques.

Thermal restructuring of silica-grafted -CrO2Cl and -VOCl2 species.

The volatile molecular precursors CrO2Cl2 and VOCl3 were grafted to thermally dehydrated silica in order to obtain site-isolated, monopodal ≡SiO-MO(x)Cl(y-1) species (M = V, Cr). Thermal restructuring under dynamic vacuum was investigated up to 450 °C with different spectroscopic techniques (viz., NMR, UV-Vis, IR, Raman and XPS).

Understanding selective oxidations.

Functionalizing organic molecules is an important value-creating step throughout the entire chemical value-chain. Oxyfunctionalization of e.g.