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 (1b–f; 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 (2b–g; n = 1–6) in good yields. The TBAF-driven condensation reactions of the silanetriols CH₃(CH₂)_n(CH₃)₂CSi­(OH)₃ (1a–c; 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 (4a–d; n = 0–3), which was not possible via the condensation of their alkoxysilane counterparts so far. The resulting compounds 2b–g and 4a–d have been characterized by multinuclear NMR, MS, and single-crystal X-ray diffraction.