Structural elucidations of T8 and Q8 silsesquioxane cages containing two types of pendant group using 29Si NMR spectroscopy

The products from the reaction of octahydrosilsesquioxane (T8-H) with different molar ratios of phenol and undec-1-ene or methyl 3,3-dimethylpent-4-enoate (MDP) in the presence of chloroplatinic acid have been analysed by 29Si NMR spectroscopy. The distribution of the two different pendant groups leads to tetrad patterns where the relative chemical peak intensities reflect the selectivity for particular patterns of substitution. As well as analysing the cause of these tetrad patterns we also discuss how the regioselectivity of hydrosilylation can be determined.Key words: T8, Q8, silsesquioxane, 29Si NMR, hydrosilylation, tetrad pattern, regioselectivity, statistical modelling.