Incompletely condensed silsesquioxanes: Formation and reactivity

Hydrolysis reaction products from aryltrialkoxysilanes were studied in various solvents with alkali and alkaline earth metal hydroxides. Definite products could be isolated when sodium hydroxide was used. Reaction of trimethoxy- or triethoxyphenylsilane with equimolar amounts of sodium hydroxide to the silicon compound in refluxing water-i-propanol gave cyclic sym-cis tetraphenylsilsesquioxanetetraoI tetrasodium salt as the principal product. When a little excess of sodium hydroxide than half molar amounts to the silicon compound was used, only small amounts of the cyclic tetramer was noticed among the initial products together with cubic octaphenylsilsesquioxane, evidenced by mass spectroscopy. Heptaphenylsilsesquioxanetriol trisodium salt was formed after refluxing for 4 h and following stirring for 15 h at room temperature. With longer reaction time, a double-decker octaphenyl silsesquiox-anetetraol tetrasodium salt was obtained in high yield with the consumption of heptaphenylsilsesquioxanetriol. While the silanols of double-decker octaphenyl silsesquioxanetetraol were thermally stable against condensation up to 230 degrees C, the sodium salt smoothly reacted with dimethyldichlorosilane to give completely condensed cage, 7,7,17,17-tetramethyl-1,3,5,9,11,13,15,19-octaphenylhexacyclo[9.13.1(1,9). 1(3.15). 1(5.13).1(11,19)]decasiloxane.