A higher yielding route to octasilsesquioxane cages using tetrabutylammonium fluoride, Part 2: further synthetic advances, mechanistic investigations and X-ray crystal structure studies into the factors that determine cage geometry in the solid state

The recently-reported reaction of triethoxysilanes with tetrabutylammonium fluoride in the presence of scarce water provides a higher yielding route to substituted octasilsesquioxane cages. Further cages have now been prepared in good yield using this route and their X-ray crystal structures demonstrate that their cage geometries in the solid state are very similar with the packing constraints of the crystal lattices appearing to have the greatest influence on the geometry of the cage core. The mechanism of the reaction has been examined and the proposed mechanism of cage formation validated, though its exclusivity has not been categorically proven. By careful choice of reaction conditions, dramatic increases in rate and yield have been demonstrated.