Hydroxyalkyl-substituted double-decker silsesquioxanes: effective separation of cis and trans isomers

In this work, we report the preparation, isolation, and characterization of a family of double-decker silsesquioxane architectures starting from the previously reported DDSQ-Me2H2 precursor, a mixture of cis and trans isomers. Using such a starting material results in a subsequent mixture of isomers when hydrosilylation reactions using DDSQ-Me2H2 and hydroxyalkyl-substituted alkenes catalyzed by Karstedt catalyst are performed. We describe a procedure to sequentially crystallize the two isomers from one another, affording a protocol potentially applicable to other closely related derivatives. The ability to access pure cis and trans isomers of double-decker silsesquioxanes may result in the preparation of new materials and polymers with well-defined properties. All resulting silsesquioxanes were characterized by multinuclear (H-1, C-13, and Si-29) NMR spectroscopy, FT-IR, and HR-MS. Additionally, we report five crystal structures of geometrical isomers, including two cis forms described in the literature for the first time. This is a breakthrough in itself and sets a new strategy for obtaining such exiting organosilicon-based systems.

Automated summary

In this study, the preparation, isolation, and characterization of a family of double-decker silsesquioxane architectures were reported. A method to obtain pure cis and trans isomers of double-decker silsesquioxanes was described, which may lead to the preparation of new materials and polymers with well-defined properties.