56-33-7Relevant articles and documents
The cyclopropylmethylsilane terminated prins reaction: Stereoelectronic controlled formation of (E)-skipped dienes
Braddock,Badine,Gottschalk
, p. 1909 - 1912 (2001)
The reaction of 1-phenyldimethylsilylmethyl-2-vinyl cyclopropane with acetals under the influence of TMSOTf proceeds smoothly to provide skipped dienes with exclusive E-olefin geometry regardless of the initial cis/trans configuration of the starting cyclopropane. The reaction is under stereoelectronic control where the intermediate Prins cation formed is stabilised by the adjacent cyclopropane grouping in a bisected conformation before undergoing silyl-directed collapse.
Experimental and theoretical investigations on the catalytic hydrosilylation of carbon dioxide with ruthenium nitrile complexes
Deglmann, Peter,Ember, Erika,Hofmann, Peter,Pitter, Stephan,Walter, Olaf
, p. 2864 - 2879 (2007)
Ruthenium complexes, mer-[RuX3(MeCN)3] and cis/trans-[RuX2-(MeCN)4] with X = Br, Cl, were investigated as precatalysts in homogeneously catalyzed hydrosilylation of CO2, The oxidation state of ruthenium and nature of the halide in the precatalysts were found to influence the catalytic activity in the conversion of Me2PhSiH to the formoxysilane Me2PhSiOCHO, with Ru III having chloride ligands being most active. Monitoring the reactions by in-situ IR spectroscopy in MeCN as the solvent indicates an interaction of the precatalyst with the silane prior to activation of CO 2. In the absence of CO2, hydrosilylation of the MeCN solvent occurs. Catalytic activity in CO2 hydrosilylation is enhanced by Me2PhSiCl, generated during reduction of RuIII in mer-[RuX3(MeCN)3] to RuII or, when added as promoter to RuII precatalysts. The reaction mechanism for the catalytic cycle has been calculated by DFT methods for the reaction of Me 3SiH. The key steps are: Transfer of the Me3Si moiety to a coordinated halide ligand, resulting in an LnRuH-(XSiMe3) intermediate → CO2 coordination → Me3Si transfer to CO2 → reductive elimination of formoxysilane product. This reaction sequence is more favorable energetically for chloride complexes than for the analogous bromide complexes, which accounts for their differences in catalytic activity. Calculations also explain the rate increase observed experimentally in the presence of Me2PhSiCl. A parallel reaction pathway leads to (Me3Si)2O as a minor byproduct which arises from the condensation of two initially formed Me3SiOH molecules.
Volumetric and Refractive Properties of the Mixtures of 1,1,3,3-Tetramethyl-1,3-diphenyldisiloxane with Various Organosilicon Compounds at T = (308.15 to 328.15) K
Dong, Hong,Yu, Lijiao,Hu, Yuqian,Wu, Chuan
, p. 1485 - 1495 (2016)
The density and refractive index were determined for four binary mixtures of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane with 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, and 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane at different temperatures (T = 308.15, 313.15, 318.15 323.15 and 328.15 K) and atmospheric pressure using a DMA4500/RXA170 combined system. The excess molar volume, partial excess volume at infinite dilution, isobaric coefficient of thermal expansion, excess refraction indices, Lorentz-Lorenz molar refraction, and the deviation in molar refraction have been calculated using these data. The results have been incorporated into the Redlich-Kister equation and used to estimate the binary interaction parameters and standard deviation. The values of partial excess volume at infinite dilution and excess refraction indices for the four binary systems at different temperatures were calculated using the adjustable parameters of the Redlich-Kister smoothing equation. The factors that affect these excess quantities have been discussed.
Silylating Disulfides and Thiols with Hydrosilicones Catalyzed by B(C6F5)3
Brook, Michael A.,Liao, Mengchen,Zheng, Sijia
supporting information, p. 2694 - 2700 (2021/06/25)
Hydrosilanes and silicones, catalyzed with B(C6F5)3, may be used to silylate thiols or cleave disulfides giving silyl thio ethers. Alcohols were found to react faster than thiols or disulfides, while alkoxysilanes (the Piers-Rubinsztajn reaction) were slower such that the overall order of reactivity was found to be HO>HS>SS>SiOEt. The resulting silane and silicone-protected thio ethers produced from the sulfur-based functional groups could be cleaved to thiols using alcohols or mild acid with rates that depend on the steric bulk of the siloxane.
Metal-free hydrogen evolution cross-coupling enabled by synergistic photoredox and polarity reversal catalysis
Cao, Jilei,Lu, Kanghui,Ma, Lishuang,Yang, Xiaona,Zhou, Rong
supporting information, p. 8988 - 8994 (2021/11/23)
A synergistic combination of photoredox and polarity reversal catalysis enabled a hydrogen evolution cross-coupling of silanes with H2O, alcohols, phenols, and silanols, which afforded the corresponding silanols, monosilyl ethers, and disilyl ethers, respectively, in moderate to excellent yields. The dehydrogenative cross-coupling of Si-H and O-H proceeded smoothly with broad substrate scope and good functional group compatibility in the presence of only an organophotocatalyst 4-CzIPN and a thiol HAT catalyst, without the requirement of any metals, external oxidants and proton reductants, which is distinct from the previously reported photocatalytic hydrogen evolution cross-coupling reactions where a proton reduction cocatalyst such as a cobalt complex is generally required. Mechanistically, a silyl cation intermediate is generated to facilitate the cross-coupling reaction, which therefore represents an unprecedented approach for the generation of silyl cationviavisible-light photoredox catalysis.
Charge Modified Porous Organic Polymer Stabilized Ultrasmall Platinum Nanoparticles for the Catalytic Dehydrogenative Coupling of Silanes with Alcohols
Chen, Chao,Cheng, Dan,Ding, Shunmin,Liang, Sanqi,Liu, Senqun,Ma, Xiaohua,Su, Tongtong,Wu, Shaohua,Zeng, Rong
, (2021/08/12)
Developing an ideal stabilizer to prevent the aggregation of nanoparticles is still a big challenge for the practical application of noble metal nanocatalysts. Herein, we develop a charge (NTf2?) modified porous organic polymer (POP-NTf2) to stabilize ultrasmall platinum nanoparticles. The catalyst is characterized and applied in the catalytic dehydrogenative coupling of silanes with alcohols. The catalyst exhibits excellent catalytic performance with highly dispersed ultrasmall platinum nanoparticles (ca. 2.22?nm). Moreover, the catalyst can be reused at least five times without any performance significant loss and Pt NPs aggregation. Graphic Abstract: [Figure not available: see fulltext.]
Hydrosilylative reduction of carbon dioxide by a homoleptic lanthanum aryloxide catalyst with high activity and selectivity
Chang, Kejian,Maron, Laurent,Xu, Xin,Zheng, Xizhou,del Rosal, Iker
supporting information, p. 7804 - 7809 (2021/06/16)
An efficient tandem hydrosilylation of CO2, which uses a combination of a simple, homoleptic lanthanum aryloxide and B(C6F5)3, was performed. Use of a less sterically hindered silane led to an exclusive reduction of CO2to CH4, with a turnover frequency of up to 6000 h?1at room temperature. The catalytic system is robust, and 19?400 turnovers could be achieved with 0.005 mol% loading of lanthanum. The reaction outcome depended highly on the nature of the silane reductant used. Selective production of the formaldehyde equivalent,i.e., bis(silyl)acetal, without over-reduction, was observed when a sterically bulky silane was used. The reaction mechanism was elucidated by stoichiometric reactions and DFT calculations.
Novel Si(II)+and Ge(II)+Compounds as Efficient Catalysts in Organosilicon Chemistry: Siloxane Coupling Reaction ?
Fritz-Langhals, Elke,Kneissl, Sotirios,Piroutek, Phillip,Werge, Sven
, (2020/09/02)
Novel catalytically active cationic Si(II) and Ge(II) compounds were synthesized and isolated in pure form. The Ge(II)+-based compounds proved to be stable against air and moisture and therefore can be handled very easily. All compounds efficiently catalyze the oxidative coupling of hydrosil(ox)anes with aldehydes and ketones as oxidation reagents and simultaneously the reductive ether coupling at very low amounts of 0.01 mol %. Because the catalysts also catalyze the reversible cyclotrimerization of aldehydes, paraldehyde can be used as a convenient source for acetaldehyde in siloxane coupling. It is shown that the reaction is especially suitable to make siloxane copolymers. Moreover, a new fluorine-free weakly coordinating boronate anion, B(SiCl3)4-, was successfully combined with the Si(II) and Ge(II) cations to give the stable catalytically active ion pairs Cp*Si:+B(SiCl3)4-, Cp*Ge:+B(SiCl3)4-, and [Cp(SiMe3)3Ge:+]B(SiCl3)4-.
Catalytic Disproportionation of Formic Acid to Methanol by using Recyclable Silylformates
Cantat, Thibault,Chauvier, Clément,Imberdis, Arnaud,Thuéry, Pierre
supporting information, p. 14019 - 14023 (2020/06/09)
A novel strategy to prepare methanol from formic acid without an external reductant is presented. The overall process described herein consists of the disproportionation of silyl formates to methoxysilanes, catalyzed by ruthenium complexes, and the production of methanol by simple hydrolysis. Aqueous solutions of MeOH (>1 mL, >70 percent yield) were prepared in this manner. The sustainability of the reaction has been established by recycling of the silicon-containing by-products with inexpensive, readily available, and environmentally benign reagents.
Cobalt-Catalyzed Selective Synthesis of Disiloxanes and Hydrodisiloxanes
Pattanaik, Sandip,Gunanathan, Chidambaram
, p. 5552 - 5561 (2019/06/05)
Selective syntheses of symmetrical siloxanes and cyclotetrasiloxanes are attained from reactions of silanes and dihydrosilanes, respectively, with water, and the reactions are catalyzed by a NNNHtBu cobalt(II) pincer complex. Interestingly, when phenylsilane was subjected to catalysis with water, a siloxane cage consisting 12 silicon and 18 oxygen centers was obtained and remarkably the reaction proceeded with liberation of 3 equiv of molecular hydrogen (36 H2) under mild experimental conditions. Upon reaction of silane with different silanols, highly selective and controlled syntheses of higher order monohydrosiloxanes and disiloxymonohydrosilanes were achieved by cobalt catalysis. The liberated molecular hydrogen is the only byproduct observed in all of these transformations. Mechanistic studies indicated that the reactions occur via a homogeneous pathway. Kinetic and independent experiments confirmed the catalytic oxidation of silane to silanol, and further dehydrocoupling processes are involved in syntheses of symmetrical siloxanes, cyclotetrasiloxanes, and siloxane cage compounds, whereas the unsymmetrical monohydrosiloxane syntheses from silanes and silanols proceeded via dehydrogenative coupling reactions. Overall these cobalt-catalyzed oxidative coupling reactions are based on the Si-H, Si-OH, and O-H bond activation of silane, silanol, and water, respectively. Catalytic cycles consisting of Co(II) intermediates are suggested to be operative.
