Polyhedral oligomeric silsesquioxanes (POSSs) consist of an inorganic Si–O core and organic substituents. They combine the tunability of organic compounds with the stability of inorganic materials. Double-decker siloxanes (DDSQs) are one type of POSS.

Armelle Ouali, Gunma University, Kiryu, Japan, and Institut Charles Gerhardt Montpellier, France, Masafumi Unno, Gunma University, and colleagues have prepared new tetravinyl- and tetraallyl-substituted closed DDSQs (pictured, R = CH=CH₂, CH₂–CH=CH₂). The team started from (Ph₈Si₈O₈)(ONa)₄ and performed a hydrolytic condensation with either divinyldichlorosilane or diallyldichlorosilane in toluene. The desired vinyl- and allyl-substituted products were obtained in yields of 67 % and 50 %, respectively.

The products could be further functionalized via hydrosilylation. According to the researchers, the synthesized DDSQs have potential as building blocks for inorganic/organic hybrid materials.

• Synthesis, Characterization, and Functionalization of Tetrafunctional Double-Decker Siloxanes,
  Yujia Liu, Nobuhiro Takeda, Armelle Ouali, Masafumi Unno,
  Inorg. Chem. 2019.
  https://doi.org/10.1021/acs.inorgchem.9b00416