Abstract
New dumbbell‐shaped octasilsesquioxanes (T8‐POSS) are obtained by the condensation of organobridged silane precursors with partially condensed T7‐triol. The synthesis based on corner‐capping proceeds under mild reaction conditions (60 °C in toluene) upon a nucleophilic fluoride‐catalyzed condensation of the T7‐triol with the alkoxysilyl organics. Two dumbbell‐type T8‐POSS, one with a non‐symmetrical urea‐thiourea linker and the other one with a symmetrical malonamide linker, are described. Their formation is monitored by FTIR, their structures are investigated by NMR spectroscopy (1H, 13C and 29Si) and confirmed by mass spectrometry.The corner‐capping of the partially condensed T7‐triol with an urea‐thiourea and a malonamide organo‐bridged silane linker using fluoride anion as a catalyst afforded a non‐symmetrical and a symmetrical functional dumbbell‐shaped T8‐POSS, respectively.