5256-79-1Relevant articles and documents
Higher polyhedral silsesquioxane (POSS) cage by amine-catalyzed condensation of silanols and related siloxanes
Kawakami, Yoshiteru,Yamaguchi, Kazuo,Yokozawa, Tsutomu,Serizawa, Takanori,Hasegawa, Minoru,Kabe, Yoshio
, p. 792 - 793 (2007)
Amine-catalyzed condensation of silanols (1a and 1b) and related siloxanes (1c-1f) provided polyhedral oligomeric silsesquioxane (POSS) (2a, 2e, 3f, 4a, 4f, and 5f) in moderate yields. Although phenyl, o-methylphenyl (o-MePh) and vinyl (Vi) substituted silanols (1a and 1b) and siloxanes (1c-1f) gave a separable mixture of cage compounds, amine catalyst showed the selectivity of higher cage formation. Copyright
Mechanistic Insights into the Synthesis of Fully Condensed Polyhedral Octaphenylsilsesquioxane
Qin, Zhao-Lu,Yang, Rong-Jie,Zhang, Wen-Chao,Jiao, Qing-Jie
, p. 1051 - 1056 (2019)
A comprehensive study on the efficient one-pot synthesis of polyhedral octaphenylsilsesquioxane (OPS) is reported via the hydrolytic condensation of phenyltrimethoxysilane (PTMS) in the presence of basic catalyst to investigate the specific synthesis mechanism. The synthetic reactions are monitored with real time infrared (RTIR) spectroscopy. Then RTIR coupled with 29Si nuclear magnetic resonance spectroscopy (NMR) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) are used to monitor the reactions and identify the intermediary species during the reaction. The rapid hydrolysis of PTMS is detected by RTIR. Contrary to previous reports, the ladder-like structured species are identified as intermediates during the reaction process. It is suggested that formation of caged T8 OPS is realized through the chain break and rearrangement of the ladder-like phenyltrimethoxysilanes. Accordingly, a scheme from hydrolysis of the PTMS to formation of the OPS is provided.
Synthetic application of silicates/silanolates and their hydrolyzed polysilanol siloxanes for polyhedral oligomeric silsesquioxanes (POSSs)
Kawakami, Yoshiteru,Seino, Hirofumi,Ohtaki, Kazushi,Kabe, Yoshio
, (2017/06/27)
Several types of silicate and their hydrolyzed polysilanols were applied to the synthesis of polyhedral oligomeric silsesquioxanes (POSSs). Silicate cubic octasilicate [Si8O20]8? 5 was silylated with trimethylchlorosilane to yield the incompletely trimethylsilylated cubic octasilicate [Si8O20](SiMe3)7H 1b bearing one silanol in addition to the totally trimethylsilylated derivative [Si8O20](SiMe3)8 1a. Further silylation of the monosilanol 1b with dimethylchlorosilane and α,ω-hydridochlorooctamethyltetrasiloxane resulted in the formation of POSSs 1c,d, which have hydrosilyl groups as elongated siloxane side chain. Attempts to generate an amino-substituted POSS via chloromethyldimethylsilylation of silicate 5 followed by reaction with amine as well as lithium amide failed. Amino-substitution was accomplished via the use of amine as a catalyst for the capping reaction of incompletely condensed trisilanol 10b with γ-aminopropyltrimethoxysilane affording mono amino-functionalized POSSs 2b,c in moderate yields. Another group of silanolates 7-9 was hydrolyzed with AcOH or HCl to give the corresponding cyclic polysilanol siloxanes 11a-c, respectively. Amine-catalyzed condensation of several of these polysilanol siloxanes 11a-c resulted in the formation of POSSs in high yields depending on the structure of substrates.
D5h [PhSiO1.5]10 synthesis via F- catalyzed rearrangement of [PhSiO1.5]n. An experimental/computational analysis of likely reaction pathways
Furgal, Joseph C.,Goodson, Theodore,Laine, Richard M.
supporting information, p. 1025 - 1039 (2016/01/15)
We describe here the synthesis and analysis of the reaction pathways leading to formation of the rare D5h decaphenylsilsesquioxane (SQ) [PhSiO1.5]10via F- catalyzed rearrangement of [PhSiO1.5]nn = 8, 12, and oligomers initially synthesized from PhSi(OEt)3. Isolated yields of ～50% [PhSiO1.5]10 are obtained via rearrangement of all starting materials. The recovered starting materials can be re-equilibrated using catalytic F- to generate similar yields in second batches. These yields arise because [PhSiO1.5]10 exhibits higher solubility and better energy stabilization (10 kcal mol-1 theory) in CH2Cl2 compared to [PhSiO1.5]8 or [PhSiO1.5]12. Reaction intermediates were identified using time dependent 19F NMR and MALDI-ToF mass spectrometry eventually equilibrating to form the 8 : 10 : 12 cages in a 1 : 3 : 1.3 equilibrium in CH2Cl2. Experimental results coupled with modeling using the Gamess computational package provide multiple reasonable pathways for SQ rearrangements to [RSiO1.5]10, starting from [RSiO1.5]8. Heats of reaction for interconversion of the model intermediates [HSiO1.5]x determined computationally, were used to select the most reasonable reaction pathways. The findings support a mechanism involving activation and cleavage of a T8 cage corner by F- attachment, followed by the corners stepwise removal as [i.e. RSi(OH)3], followed thereafter by reinsertion forming [RSiO1.5]9-OH followed by, insertion of another corner to form [RSiO1.5]10-(OH)2 and finally condensation to give [RSiO1.5]10. The most enthalpically favorable path (-24 kcal mol-1) involves a hybrid mechanism.
