Synthesis, Structures, and Thermal Properties of Symmetric and Janus “Lantern Cage” Siloxanes

Abstract

Symmetric and asymmetric (Janus‐type) new “lantern cage” siloxanes (PhSiO1.5)4(Me2SiO)4(RSiO1.5)4 (R=Ph or iBu) were synthesized through reaction of all‐cis‐[PhSi(OSiMe2Br)O]4 with all‐cis‐[RSi(OH)O]4 (R=Ph or iBu). These precursors were obtained by facile two or three‐step reactions from commercially available compounds. The spectroscopic properties of the resulting products were fully characterized and they showed high thermal stability and sublimation without decomposition. The crystal structures clearly indicated that the internal vacancy volumes of the lantern cages are considerably larger than that of octaphenylsilsesquioxane (PhSiO1.5)8. DFT calculations of the lantern cage showed a distinctly different electronic state from that of octasilsesquioxane. These results suggest that lantern cage siloxanes have a characteristic “field” in the molecule.

Zinc Imine Polyhedral Oligomeric Silsesquioxane as a Quattro‐Site Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Low‐Pressure CO2

“…Polyhedral silsesquioxanes, organosilicon compounds described by the chemical formula (RSiO 3/2 ) n , are representatives of a class of cage‐like compounds [1–3] . Polyhedral oligomeric silsesquioxane (POSS) cages include usually T 6 , T 8 , T 10 , and T 12 , structures, however, the most widely studied are the cubic T 8 as well as, recently, the lantern, [4] butterfly, [5] Janus, [6] or double‐decker [7] types of cages. On the basis of their diameters, which range from 1 to 3 nm, they can be considered as the smallest existing silica nanoparticles.…”

Formation of Bifunctional Octasilsesquioxanes via Silylative Coupling and Cross-Metathesis Reaction

“…Nevertheless, hydrosilylation remains one of the most useful methods for obtaining bifunctional silsesquioxanes, and it has been the subject of multiple research papers [ 7 , 8 , 10 , 12 ]. Heck coupling [ 28 , 29 , 30 , 31 ] and condensation reactions [ 32 , 33 , 34 , 35 , 36 ] were also applied in this type of synthesis. There are also single notes on the utilization of thiol-ene [ 37 ], hydration [ 38 , 39 ] and click type reactions [ 40 , 41 , 42 ] for the synthesis of multifunctionalized silsesquioxanes.…”

Synthesis of Polycyclic and Cage Siloxanes by Hydrolysis and Intramolecular Condensation of Alkoxysilylated Cyclosiloxanes

“…[29][30][31][32] However, because the specific reaction processes remainu nknown, at rial-and-errora pproach is necessary to synthesize oligosiloxanes with new structures.T he intermolecular condensation of low-molecular-weight oligosiloxanes has also been investigated, and oligosiloxanes that are challenging to synthesize from monomers have been prepared by this approach. [10,[33][34][35][36][37][38] For example, Unnoa nd co-workerss ynthesized laddersiloxanes by the co-condensation of cyclotetrasiloxanes and disiloxanes. [34,37] Furthermore, they successfully synthesized aJ anus-type cage oligomer (polyhedral oligomeric silsesquioxane, POSS) having different organic groups on the upper and lower sides of the cube by the co-condensation of two cyclotetrasiloxanes bearingp henyla nd isobutyl substituents.…”