Synthesis and crystal structure of double-three ring (D3R)-type cage siloxanes modified with dimethylsilanol groups

Abstract

Two types of cage-type oligosiloxanes with double-three ring (D3R) structures are modified with dimethylsilanol groups to form crystalline supramolecular assemblies.

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

“…Synthesis of alkoxysilylated cyclotetrasiloxanes 4MR-1, 4MR-2, and 4MR-3:C yclotetrasiloxanes bearing dimethyl(ethoxy)silyl, methyldiethoxysilyl, and triethoxysilyl groups (denoted as 4MR-1, 4MR-2,a nd 4MR-3,r espectively) were prepared as follows. Crystals of sodium phenylsiloxanolate, which have been reported to give trimethylsilylated cyclotetrasiloxane, [47] were dried under reduced pressure at 80 8Cf or 2h.T he resulting white solid (0.5499, 0.9645, and 1.0390 g, respectively) was then added to am ixture of dehydrated toluene (25,17, and 50 mL, respectively), dehydrated pyridine (10, 10, and 20 mL, respectively), and the silylating agent (obtained by partial ethoxylation of Me 2 SiCl 2 (6.9 mL), MeSiCl 3 (8.8 mL), and SiCl 4 (22.7 mL), respectively,a sd escribed above) in aS chlenk flask at low temperature (À95, 0, and À95 8Cf or 4MR-1, 4MR-2, and 4MR-3,r espectively;n ote that silylation at low temperature is crucial to avoid condensation of the siloxanolates [48] ). The mixtures were stirred for more than 12 ha tr oom temperature under an atmosphere of N 2 .T hen, excesses of dehydrated pyridine and dehydrated EtOH were added to the mixtures to eliminate the SiÀCl groups of the unreacted silylating agents.…”

Alkoxy- and Silanol-Functionalized Cage-Type Oligosiloxanes as Molecular Building Blocks to Construct Nanoporous Materials

“…A D3R siloxane modified with dimethylsilanol groups (Si 6 O 9 (OSiMe 2 OH) 6 ) was also synthesized to form molecular crystals [56]. In this case, dimethylsilylation of Si 6 O 9 6− at a low temperature (−94 • C) was crucial for suppressing the deterioration of the relatively unstable D3R cages.…”

“…However, this crystal had no open channels; therefore, a microporous material was not obtained. H-bonded molecular crystals have also been obtained from dimethylsilanol-modified cage organosiloxane containing methylene groups in the framework [56]. Although microporous crystals have so far been obtained only from the dimethylsilanol-modified D4R siloxanes [55], regular arrangement of cage siloxanes by H-bonding of silanol groups is expected as a new soft chemical approach to the construction of crystalline zeolitic materials.…”