Session: Polymer Division Student Poster Session: Celebrating the Diversity of Macromolecules:

Polyhedral Oligomeric Silsesquioxanes (POSS) are a class of molecules consisting of an inorganic siloxane core surrounded by organic functionality. Controlling the organic groups of the POSS is important for constructing nanomaterials with various applications in materials science and biomedical engineering. Currently, the synthetic methods to access functionalized POSS are limited. To increase the diversity of synthetic methods, we have demonstrated metal-catalyzed carbene insertion into POSS containing one, three and eight Si–H bonds using aryl/ester diazo compounds as carbene precursors. A screen of metal catalysts identified that dirhodium(II) carboxylates provide optimal reactivity to form POSS insertion products that can be isolated in good to excellent yields. A novel POSS-based silane was synthesized and utilized for single carbene insertions. The Rh-catalyzed carbene insertion is applicable for POSS containing up to eight Si–H bonds (up to gram-scale) by simply increasing the equivalents of the diazo compound. A series of diazo compounds have been evaluated to demonstrate the functional diversity that is capable of being installed on both the ester and aryl groups. Several further transformations of POSS-insertion products were completed using both functional handles. Hydrolysis of the POSS ester was achieved to afford carboxylic acid-functionalized POSS under mild conditions. For POSS insertion products containing an aryl bromide, a Suzuki-Miyura coupling was achieved to enable the formation of biphenyl-containing POSS.

Jake Jagannathan

PhD Candidate, University of California, Davis

Appearances