Synthesis and ligand properties of silsesquioxane‐caged phosphite T7Ph7P

The synthesis of the phosphorus‐capped heptaphenylsilsesquioxane T7Ph7P is reported. We show that, unlike previous examples, it readily forms Lewis acid‐base adducts with boranes of different steric demand and the FeCO4 fragment. All complexes were characterized by multinuclear NMR and IR spectroscopy in solution and the solid state. The molecular structures of the adducts with BPh3 and B(C6F5)3 were determined from XRD suitable single crystals. The relative conformation of the Ph and C6F5 rings in T7Ph7P‐B(C6F5)3 suggests favorable π‐interactions, stabilizing the adducts to such a degree that attempts to activate H2 or CO2 were unsuccessful.