Silanetriols as Powerful Starting Materials for Selective Condensation to Bulky POSS Cages

Controlled condensation reactions of tertiary silanetriols CH3(CH2)n(CH3)2CSi­(OH)3 (1bf; n = 1–5) in the presence of trifluoroacetic acid and the hydrolysis of CH3(CH2)6(CH3)2CSiCl3 (3) lead to the selective formation of the corresponding disiloxane tetrols [CH3(CH2)n(CH3)2CSi­(OH)2]2O (2bg; n = 1–6) in good yields. The TBAF-driven condensation reactions of the silanetriols CH3(CH2)n(CH3)2CSi­(OH)3 (1ac; n = 0–2) as well as of the disiloxane-1,1,3,3-tetrol 2d (n = 3) yield in the selective formation of the first T8 cages bearing tertiary carbon substituents, CH3(CH2)n(CH3)2C (4ad; n = 0–3), which was not possible via the condensation of their alkoxysilane counterparts so far. The resulting compounds 2bg and 4ad have been characterized by multinuclear NMR, MS, and single-crystal X-ray diffraction.