Unprecedented formation of cis- and trans-di[(3-chloropropyl) isopropoxysilyl]-bridged double-decker octaphenylsilsesquioxanes

Silsesquioxane formation competing with the deprotonation of alcohol solvents in the presence of a strong base to form alkoxides is reported for the first time. Evidently, sodium isopropoxide is formed during the synthesis of the sodium salt of a double-decker octaphenylsilsesquioxane tetrasilanolate in 2-propanol as the solvent, which leads to the formation of unexpected cis- and trans-di[(3-chloropropyl)isopropoxysilyl]-bridged double-decker octaphenylsilsesquioxanes after in situ coupling with 3- chloropropyltrichlorosilane. The desired products were characterized by ¹H NMR, ¹³C NMR, and ²⁹Si NMR spectroscopy; ESI-MS; and single-crystal X-ray diffraction. During the synthesis of the sodium salt of double-decker octaphenylsilsesquioxane tetrasilanolate in 2-propanol, sodium isopropoxide is formed, which leads to the formation of unexpected cis- and trans-di[(3-chloropropyl)isopropoxysilyl]-bridged double-decker octaphenylsilsesquioxanes after in situ coupling with 3- chloropropyltrichlorosilane.