Fe(III)-Based Phenylsilsesquioxane/Acetylacetonate Complexes: Synthesis, Cage-like Structure, and High Catalytic...

Unprecedented iron-based silsesquioxane/acetylacetonate complexes were synthesized. The intriguing cage-like structure of compounds is alkaline metal-dependent: the Fe₂Li₂ complex includes condensed Si₆-silsesquioxane and four acetylacetonate ligands; the Fe₄Na₄ complex exhibits two cyclic Si₄-silsesquioxane and eight acetylacetonate ligands, while the Fe₃K₃ complex features two cyclic Si₃-silsesquioxane and six acetylacetonate ligands. The latter case is the very first observation of small trimeric silsesquioxane ligands in the composition of cage-like metallasilsesquioxanes. The Fe₄Na₄-based complex exhibits a record high activity in the oxidation of inert alkanes with peroxides (55% yield of oxygenates in cyclohexane oxidation). It also acts as a catalyst in the cycloaddition of CO₂ with epoxides, leading to cyclic carbonates in good yields (58-96%).