Polyhedral silsesquioxane anions are economically prepared by reaction of a silica source derived from combusted organic material with a quaternary ammonium hydroxide compound. Reaction of the resulting anions with chlorosilanes may be effected in near stoichiometric fashion in organic solvent containing reactive quantities of organic acids such as formic acid. The functional groups on the resulting functionalized silsesquioxanes may be substituted for other functional groups by reaction with di- or polysiloxanes in the presence of a synthetic ion exchange resin.