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.