The reactions of dialkyl and diarylethoxysilanes with T 6 silsesquioxane cages : X-ray crystallographic studies of the mono-T 6D 1 and bis-T 6D 2 insertion ring expansion products

Abstract

Successful ring-expanding insertion reactions of T 6 silsesquioxane cages using dialkyl and diarylethoxysilanes have been performed to give the first reported mixed T 6D 1 and T 6D 2 silsesquioxane cages. The reactions of hexacyclohexylsilsesquioxane (T 6) with dialkyl and diaryldiethoxysilanes give predominantly T 6D 2 bis-insertion compounds while the reaction of T 6 with dimethylethoxysilane gives one T 6D 1 mono-insertion product and various T 6D 2 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.