Synthesis and crystal structures of bromo- and ester-functionalised polyhedral silsesquioxanes

Radical initiated hydrobromination and methoxycarbonylation using a Pd(0) complex have been used to convert octavinylsilsesquioxane to species functionalised with alkyl bromide and linear methyl propanoate groups on all eight reactive sites, respectively. The two new molecules, 1,3,5,7,9,11,13,15-octakis[ethylbromide]octasiloxane and 1,3,5,7,9,11,13,15-octakis[methylpropanoate]octasiloxane, have been characterised using NMR (1H, 13C and 29Si) and IR spectroscopy, elemental analysis and single crystal X-ray diffraction.

Graphical abstractTwo new functionalised octasilsesquioxanes have been prepared using octavinylsiloxane as the starting material. 1,3,5,7,9,11,13,15-octakis[ethylbromide]octasiloxane has been prepared by radical-initiated addition of HBr across the vinyl group and 1,3,5,7,9,11,13,15-octakis[methylpropanoate]octasiloxane has been prepared by direct methoxycarbonylation using a Pd(0) catalyst. Crystal structures of both compounds have been determined.Figure optionsDownload full-size imageDownload as PowerPoint slide