(44f) Synthesis, Characterization, and Catalytic Activity of Nanostructured Tin(IV) and Tungsten(VI) Catalysts

Our group has developed a broadly applicable methodology for synthesizing nanostructured, single site heterogeneous catalysts based on the building block (Me₃SnO)₈Si₈O₁₂. Reacting the building block (bb) with high valent metal chlorides results in the formation of atomically dispersed metal centers that sit between building blocks and act as cross-linking agents. Following the insertion of the high valent metal centers into the bb matrix, silyl chlorides are used to further cross link the matrix creating a rigid and robust high surface area support (>300 m²/g). At this point any remaining trimethyltin groups are removed using a silyl chloride. When the appropriate stoichiometric ratio of metal chloride to building block is used, tin tetrachloride and tungsten hexachloride produce exclusively 4-connected tin and 6-connected tungsten centers, respectively. Atomically dispersed tin(IV) and tungsten(VI) centers in silicate matrices can function as both solid acid and selective oxidation catalysts. The acid-base properties of these catalysts have been characterized via alcohol dehydration/dehydrogenation. The catalytic activity of our nanostructured catalysts in both solid acid and selective oxidation reactions will be compared to the catalytic activity of similar heterogeneous catalysts found in the literature. Our current efforts to connect the nanostructuring in these catalysts to the observed catalytic activity will also be discussed.