Cage-type siloxanes have attracted increasing attention as building blocks for silica-based nanomaterials as their corners can be modified with various functional groups. Cubic octasiloxanes incorporating both Si−H and Si−OtBu groups [(tBuO)nH8−nSi8O12; n=1, 2 or 7] have been synthesized by the reaction of octa(hydridosilsesquioxane) (H8Si8O12) and tert-butyl alcohol in the presence of a Et2NOH catalyst. The Si−H and Si−OtBu groups are useful for site-selective formation of Si−O−Si linkages without cage structure deterioration. The Si−H group can be selectively hydrolyzed to form a Si−OH group in the presence of Et2NOH, enabling the formation of the monosilanol compound (tBuO)7(HO)Si8O12. The Si−OH group can be used for either intermolecular condensation to form a dimeric cage compound or silylation to introduce new reaction sites. Additionally, the alkoxy groups of (tBuO)7HSi8O12can be treated with organochlorosilanes in the presence of a BiCl3catalyst to form Si−O−Si linkages, while the Si−H group remains intact. These results indicate that such bifunctional cage siloxanes allow for stepwise Si−O−Si bond formation to design new siloxane-based nanomaterials.
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