The reactions of dialkyl and diarylethoxysilanes with T6 silsesquioxane cages: X-ray crystallographic studies of the mono-T6D1 and bis-T6D2 insertion ring expansion products

Successful ring-expanding insertion reactions of T6 silsesquioxane cages using dialkyl and diarylethoxysilanes have been performed to give the first reported mixed T6D1 and T6D2 silsesquioxane cages. The reactions of hexacyclohexylsilsesquioxane (T6) with dialkyl and diaryldiethoxysilanes give predominantly T6D2 bis-insertion compounds while the reaction of T6 with dimethylethoxysilane gives one T6D1 mono-insertion product and various T6D2 bis-insertion products as isolable components. Three of the ring-expanded products are chiral and it has been shown from their X-ray crystal structures that the pairs of enantiomers, formed as racemic mixtures, co-crystallise together. As well as comparing these structures with related ones in the literature, the possible mechanism of their formation is discussed.