Fluoride Ion Entrapment in Octasilsesquioxane Cages as Models for Ion Entrapment in Zeolites. Further Examples, X-ray Crystal Structure Studies, and Investigations into How and Why They May Be Formed

Two fluoride-encapsulated octasilsesquioxane cage compounds have been prepared using the TBAF route as important molecular models for studying ion entrapment in siliceous zeolites. Analyses by X-ray crystal structure and solution 19F/29Si NMR spectroscopy reveal very similar environments for the encapsulated fluoride ion perfectly centered within each cage with evidence of weak silicon−fluoride ion interactions. By comparing our NMR and X-ray data with those of nonencapsulated cage analogues from the literature, we observe the effect the fluoride ion has on the geometry of the cage and use the findings of related studies in the literature to suggest reasons fluoride ion may be becoming entrapped in the silsesquioxane core.