Synthesis and Ligand Properties of Silsesquioxane‐Caged Phosphite T 7 Ph 7 P

The synthesis of the phosphorus‐capped heptaphenylsilsesquioxane T 7 Ph 7 P is reported. We show that, unlike previous examples, it readily forms Lewis acid‐base adducts with boranes of different steric demand and the FeCO 4 fragment. All complexes were characterized by multinuclear NMR and IR spectroscopy in solution and the solid state. The molecular structures of the adducts with BPh 3 and B(C 6 F 5 ) 3 were determined from XRD suitable single crystals. The relative conformation of the Ph and C 6 F 5 rings in T 7 Ph 7 P−B(C 6 F 5 ) 3 suggests favorable π‐interactions, stabilizing the adducts to such a degree that attempts to activate H 2 or CO 2 were unsuccessful.