Data: 30 de Novembro de 2023

Horário: 16h

Palestrante: Prof. Dr. John Bartlett (Western Sidney University)

Local: Anfiteatro “Prof. Milan Trsic” – Instituto de Química de São Carlos, Edifício Q1 – 2º. andar

Resumo:

“Among the family of well-defined silsesquioxane oligomers, the cage silsesquioxanes (also referred to as polyhedral oligomeric silsesquioxanes, POSS) have been widely studied, with a particular focus on the T₈ cage.¹ These have been described with various organic substituents at the silicon atoms (e.g. chloropropyl, vinyl, phenyl, etc.), with the reactivity of such compound being controlled by the organic moiety. However, few articles report the synthesis and characterization of larger cages, with the largest previously isolated and fully characterized being the T₁₄ cage.²

This presentation will explore the synthesis of a new family of styryl-substituted cage silsesquioxanes. In contrast to previous report,³ the styryl group in these compounds is linked to the silicon atom via the phenylene group, with the free vinyl group being readily functionalizable by hydrosilylation, Heck’s, thiol-ene, or metathesis reactions. In addition to the more common T₈, T₈‑F, T₁₀ and T₁₂ cages,^4,5 the isolation and characterisation of an unprecedented T₁₈ cage silsesquioxane as a pure product is also described.⁶ The structures and properties of the compounds were established by single crystal X-ray crystallography (T_n, n<12), multinuclear NMR, mass spectrometry, etc, and the structure of the T₁₈ cage was determined from ²⁹Si data using a ring-strain model.⁶

 

The T₈, T₈‑F and T₁₀ compounds were subsequently functionalised via thiol-ene Click reactions to introduce hydrolysable thiopropyltriethoxysilane moieties on each of the styryl arms attached to the POSS core. Following addition of aqueous HCl to the precursors, monolithic gels were rapidly formed in which the POSS cages remained intact within the hybrid networks, with no Si-C cleavage being observed. To the best of our knowledge, this is the first report of the incorporation of T₈‑F and T₁₀ cages in such gels.

References

1. Cordes D. B., Lickiss P. D., Rataboul F. (2010) Chem. Rev. 110: 2081–2173.
2. Agaskar P. A., Klemperer W. G. (1995) Inorganica Chim. Acta 229: 355–364.
3. Hwan Jung J., Furgal J. C., Goodson T., Mizumo T., Schwartz M., Chou K., Vonet J.-F. F., Laine R. M. (2012) Chem. Mater. 24: 1883–1895.
4. Laird M., Van Der Lee A., Dumitrescu D. G., Carcel C., Ouali A., Bartlett J. R., Unno M., Wong Chi Man M. (2020) Organometallics 39: 1896-1906.
5. Laird, M., Totée, C., Gaveau, P., Silly, G., Van der Lee, A., Carcel, C., Unno, M., Bartlett, J.R., Wong Chi Man, M. (2021) Dalton Trans., 50: 81-89.
6. Laird M., Herrmann N., Ramsahye N., Totée C., Carcel C., Unno M., Bartlett J. R., Wong Chi Man M. (2021) Angew. Chemie – Int. Ed. 60: 3022-3027.”