Mass spectrometric characterization of polyhedral oligosilsesquioxanes and heterosilsesquioxanes

Abstract

Silsesquioxanes constitute a diverse range of Si-O frameworks with a wide variety of intriguing possibilities as models for catalysis. These topologically interesting molecules are formed by the hydrolytic condensation of trifunctional organosilanes. Heterosilsesquioxanes are formally derived by substitution of a main-group, transition-metal, or f-element atom for one or more Si atoms in a silsesquioxane. A number of silsesquioxanes and their metal-containing derivatives, metallasilsesquioxanes (Si-O-M), were characterized using atmospheric pressure chemical ionization (APCI) and turbo ion-spray (TISP) mass spectrometry. The use of n-hexane or n-hexane/ethanol (90:10, v/v) allowed the techniques to be utilized to characterize a large number of complexes. In some cases addition of trace amounts of ammonium acetate, sodium chloride, or sodium acetate to the ethanolic portion of the solvent allowed the detection of [M + NH4]+ or [M + Na]+ ions. Copyright © 1999 John Wiley & Sons, Ltd.