- Light-Promoted Transfer of an Iridium Hydride in Alkyl Ether Cleavage
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A catalytic, light-promoted hydrosilylative cleavage reaction of alkyl ethers is reported. Initial studies are consistent with a mechanism involving heterolytic silane activation followed by delivery of a photohydride equivalent to a silyloxonium ion generated in situ. The catalyst resting state is a mixture of Cp*Ir(ppy)H (ppy = 2-phenylpyridine-κC,N) and a related hydride-bridged dimer. Trends in selectivity in substrate reduction are consistent with nonradical mechanisms for C-O bond scission. Irradiation of Cp*Ir(ppy)H with blue light is found to increase the rate of hydride delivery to an oxonium ion in a stoichiometric test. A comparable rate enhancement is found in carbonyl hydrosilylation catalysis, which operates through a related mechanism also involving Cp*Ir(ppy)H as the resting state.
- Fast, Caleb D.,Schley, Nathan D.
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supporting information
p. 3291 - 3297
(2021/10/12)
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- High Production of Hydrogen on Demand from Silanes Catalyzed by Iridium Complexes as a Versatile Hydrogen Storage System
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The catalytic dehydrogenative coupling of silanes and alcohols represents a convenient process to produce hydrogen on demand. The catalyst, an iridium complex of the formula [IrCp?(Cl)2(NHC)] containing an N-heterocyclic carbene (NHC) ligand functionalized with a pyrene tag, catalyzes efficiently the reaction at room temperature producing H2 quantitatively within a few minutes. As a result, the dehydrogenative coupling of 1,4-disilabutane and methanol enables an effective hydrogen storage capacity of 4.3 wt % that is as high as the hydrogen contained in the dehydrogenation of formic acid, positioning the silane/alcohol pair as a potential liquid organic hydrogen carrier for energy storage. In addition, the heterogenization of the iridium complex on graphene presents a recyclable catalyst that retains its activity for at least 10 additional runs. The homogeneous distribution of catalytic active sites on the basal plane of graphene prevents diffusion problems, and the reaction kinetics are maintained after immobilization.
- Ventura-Espinosa, David,Sabater, Sara,Carretero-Cerdán, Alba,Baya, Miguel,Mata, Jose A.
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p. 2558 - 2566
(2018/03/13)
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- Metal-Free Catalytic Reductive Cleavage of Enol Ethers
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In contrast to the well-known reductive cleavage of the alkyl-O bond, the cleavage of the alkenyl-O bond is much more challenging especially using metal-free approaches. Unexpectedly, alkenyl-O bonds were reductively cleaved when enol ethers were reacted with Et3SiH and a catalytic amount of B(C6F5)3. Supposedly, this reaction is the result of a B(C6F5)3-catalyzed tandem hydrosilylation reaction and a silicon-assisted β-elimination. A mechanism for this cleavage reaction is proposed based on experiments and density functional theory (DFT) calculations.
- Chulsky, Karina,Dobrovetsky, Roman
-
supporting information
p. 6804 - 6807
(2018/11/02)
-
- Wettability-Driven Palladium Catalysis for Enhanced Dehydrogenative Coupling of Organosilanes
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Direct coupling of Si-H bonds has emerged as a promising strategy for designing chemically and biologically useful organosilicon compounds. Heterogeneous catalytic systems sufficiently active, selective, and durable for dehydrosilylation reactions under mild conditions have been lacking to date. Herein, we report that the hydrophobic characteristics of the underlying supports can be advantageously utilized to enhance the efficiency of palladium nanoparticles (Pd NPs) for the dehydrogenative coupling of organosilanes. As a result of this prominent surface wettability control, the modulated catalyst showed a significantly higher level of efficiency and durability characteristics toward the dehydrogenative condensation of organosilanes with water, alcohols, or amines in comparison to existing catalysts. In a broader context, this work illustrates a powerful approach to maximize the performance of supported metals through surface wettability modulation under catalytically relevant conditions.
- Lin, Jian-Dong,Bi, Qing-Yuan,Tao, Lei,Jiang, Tao,Liu, Yong-Mei,He, He-Yong,Cao, Yong,Wang, Yang-Dong
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p. 1720 - 1727
(2017/08/15)
-
- Synthesis of nitrogen and sulfur co-doped hierarchical porous carbons and metal-free oxidative coupling of silanes with alcohols
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Hierarchically porous N and S co-doped carbon was prepared by using 2,5-dihydroxy-1,4-benzoquinone as the carbon source, thiourea as the N and S source, and SiO2 particles as the template. Using the material as the catalyst, oxidative coupling of silanes with alcohols was conducted for the first time under metal-free conditions.
- Chen, Bingfeng,Li, Fengbo,Mei, Qingqing,Yang, Youdi,Liu, Huizhen,Yuan, Guoqing,Han, Buxing
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supporting information
p. 13019 - 13022
(2017/12/15)
-
- Silica-supported ultra small gold nanoparticles as nanoreactors for the etherification of silanes
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Ultra small gold nanoparticles supported by porous silica (Au-SiO2) were successfully synthesized. Due to enrichment of reactants by silica, the Au-SiO2 particles functioned as nanoreactors for catalytic etherification of silanes wit
- Wang, Cui,Lin, Xijie,Ge, Yuzhen,Shah, Zameer Hussain,Lu, Rongwen,Zhang, Shufen
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p. 102102 - 102108
(2016/11/09)
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- Catalytic reduction of CO2with organo-silanes using [Ru3(CO)12]
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The reaction of carbon dioxide with Et3SiH in the presence of catalytic amounts of [Ru3(CO)12] as a catalytic precursor was achieved to produce silyl formate (Et3SiOCOH) 1s with a TON of 9000. A similar reaction in the presence of KF yielded potassium formate (8s) in a one-pot protocol with high selectivity using water or MeCN as the solvent. In the current report the complete reduction of carbon dioxide to methane was achieved, with the use of a more reactive silane (phenylsilane). A catalytically relevant species was the ruthenium cluster [H4Ru4(CO)12]. This is the second report on the hydrosilylation of carbon dioxide catalyzed by highly active and readily available ruthenium clusters and this is the first report of hydrosilylation of CO2to methane.
- Jurado-Vázquez, Tamara,Ortiz-Cervantes, Carmen,García, Juventino J.
-
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- Dehydrogenative coupling of alcohol with hydrosilane catalyzed by an iron complex
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Silane alcoholysis of triethylsilane (Et3SiH) with alcohol (ROH) with the help of CpFe(CO)2Me (1) has been achieved to produce triethylsilyl ether (ROSiEt3) under the thermal condition. For some alcohols, the iron complex
- Fukumoto, Kozo,Kasa, Michiho,Nakazawa, Hiroshi
-
p. 219 - 221
(2015/03/30)
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- Photo Lewis acid generators: Photorelease of B(C6F5)3 and applications to catalysis
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A series of molecules capable of releasing of the strong organometallic Lewis acid B(C6F5)3 upon exposure to 254 nm light have been developed. These photo Lewis acid generators (PhLAGs) can now serve as photoinitiators for several important B(C6F5)3-catalyzed reactions. Herein is described the synthesis of the triphenylsulfonium and diphenyliodonium salts of carbamato- and hydridoborates, their establishment as PhLAGs, and studies aimed at defining the mechanism of borane release. Factors affecting these photolytic reactions and the application of this concept to photoinduced hydrosilylation reactions and construction of siloxane scaffolds are also discussed.
- Khalimon, Andrey Y.,Shaw, Bryan K.,Marwitz, Adam J. V.,Piers, Warren E.,Blackwell, James M.,Parvez, Masood
-
supporting information
p. 18196 - 18206
(2015/10/28)
-
- N-heterocyclic carbene organocatalysts for dehydrogenative coupling of silanes and hydroxyl compounds
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Go organic! N-Heterocyclic carbene (NHC) 1,3-diisopropyl-4,5- dimethylimidazol-2-ylidene (IiPr) has been found to be an efficient and selective catalyst for the dehydrogenative coupling of a wide range of silanes and hydroxyl groups to form Si-O bonds under mild and solvent-free conditions (see scheme). Mechanistic studies indicated that the activation of hydroxyl groups by the NHC is the most plausible initial step for the process. Copyright
- Gao, Dongjing,Cui, Chunming
-
supporting information
p. 11143 - 11147
(2013/09/02)
-
- METHODS AND COMPOUNDS FOR PHOTO LEWIS ACID GENERATION AND USES THEREOF
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There are disclosed masked Lewis acids into compounds in which the Lewis acid can be released by exposure of the compound to light, especially ultraviolet light. These compounds can be represented by the following formula (I): ([(AEX(3-n))(n+1)Yn](n+1)-)m(Qm+)(n+1) (I). wherein briefly, E represents boron or aluminium, X is an aryl group and Y is -Ar'EAX,. These compounds are used as catalyst for hydrosilylation reaction, crosslinking of polymers, or ester deprotection reactions as photo Lewis acid generator (PhLAG).
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-
Page/Page column 37; 38
(2013/10/21)
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- Ruthenium carbonyl-catalysed Si-heteroatom X coupling (X = S, O, N)
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Ru3(CO)12 has been shown to catalyse the coupling of silanes with thiols, alcohols and amines with turnover number (TON) and turnover frequency (TOF) of up to 200 and 50 h-1 at 80 °C. IR, NMR and mass spectroscopic studies have identified a ruthenium dimer complex, [Ru(CO)4(SiEt3)]2 as a likely resting state of the catalyst. A mechanism involving this complex has been proposed for the silicon-thiol coupling process.
- Toh, Chun Keong,Poh, Hwa Tiong,Lim, Ching Si,Fan, Wai Yip
-
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- Catalytic hydrosilylation of carbonyls via Re(CO)5Cl photolysis
-
The hydrosilylation reaction between silanes and various carbonyl substrates such as aldehyde, ketone, ester, and carbonate has been catalyzed by Re(CO)5Cl UV photolysis. Kinetic studies have shown that the reaction is favored for the least sterically hindered silanes with aldehydes followed by aliphatic ketones. The IR spectrum of the rhenium carbonyl dimer HRe 2(CO)9(SiR3) has been recorded in the reaction mixture. This complex is believed to be the resting state of the active catalyst Re(CO)4SiR3, which could be released upon photactivation. A catalytic mechanism involving this species has been proposed and shown to be thermodynamically feasible using computational studies. In addition, the relative hydrosilylation rates among the various carbonyl substrates can be explained using the same mechanism.
- Toh, Chun Keong,Sum, Yin Ngai,Fong, Wai Kit,Ang, Siau Gek,Fan, Wai Yip
-
experimental part
p. 3880 - 3887
(2012/07/02)
-
- A photo Lewis acid generator (PhLAG): Controlled photorelease of B(C 6F5)3
-
A molecule that releases the strong organometallic Lewis acid B(C 6F5)3 upon irradiation with 254 nm light has been developed. This photo Lewis acid generator (PhLAG) now enables the photocontrolled initiation of several reactions catalyzed by this important Lewis acid. Herein is described the synthesis of the triphenylsulfonium salt of a carbamato borate based on a carbazole function, its establishment as a PhLAG, and the application of the photorelease of B(C6F5) 3 to the fabrication of thin films of a polysiloxane material.
- Khalimon, Andrey Y.,Piers, Warren E.,Blackwell, James M.,Michalak, David J.,Parvez, Masood
-
supporting information; experimental part
p. 9601 - 9604
(2012/07/14)
-
- Using the nonaqueous electrolytic solution and secondary battery
-
PROBLEM TO BE SOLVED: To provide nonaqueous electrolyte solution capable of improving at least either large-current charge/discharge characteristics or charge/discharge capacity, and a nonaqueous electrolyte solution secondary battery using it. SOLUTION: Electrolyte solution that is liquid electrolyte is immersed in a separator 23. The electrolyte solution contains a liquid solvent, for instance, a nonaqueous solvent such as an organic solvent, and electrolyte salt dissolved in the nonaqueous solvent. Further, as additives, it contains at least one type selected from tris (penta-fluorophenyl) borane (TPFPB) and tris-borate (2H-hexafluoro isopropyl) (THFPB), and at least one type selected from vinylene carbonate (VC) and vinyl ethylene carbonate (VEC). COPYRIGHT: (C)2008,JPO&INPIT
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- [NiX2(NHC)2]complexes in the hydrosilylation of internal alkynes
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A number of nickel(II) dihalide complexes with small monodentate N-heterocyclic carbene ligands was synthesized and tested for their catalytic activity in the hydrosilylation of internal alkynes. The nickel(0) active species was obtained from the starting
- Berding, Joris,Van Paridon, John A.,Van Rixel, Vincent H. S.,Bouwman, Elisabeth
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scheme or table
p. 2450 - 2458
(2011/08/03)
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- Cationic silane δ-complexes of ruthenium with relevance to catalysis
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Hydrosilylation of carbonyls catalyzed by 2 goes via intermediate formation of cationic silane σ-complexes 4 which undergo nucleophilic abstraction of the silylium cation studied by DFT calculations.
- Gutsulyak, Dmitry V.,Vyboishchikov, Sergei F.,Nikonov, Georgii I.
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supporting information; experimental part
p. 5950 - 5951
(2010/07/05)
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- Hydrosilylation of carbonyl-containing substrates catalyzed by an electrophilic η1-silane iridium(III) complex
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Hydrosilylation of a variety of ketones and aldehydes using the cationic iridium catalyst (POCOP)Ir(H)(acetone)+, 1 (POCOP = 2,6-bis(di-tert-butylphosphinito)phenyl), is reported. With triethyl silane, all but exceptionally bulky ketones undergo quantitative reactions employing 0.5 mol % catalyst in 20-30 min at 25 °C. Hydrosilylation of esters and amides results in over-reduction and cleavage of C-O and C-N bonds, respectively. The diastereoselectivity of hydrosilylation of 4-tert-butyl cyclohexanone has been examined using numerous silanes and is highly temperature dependent. Using EtMe2SiH, analysis of the ratio of cis:trans hydrosilylation products as a function of temperature yields values for ΔΔH ? (ΔH?(trans) - ΔH ?(cis)) and ΔΔS? (ΔS ?(trans) - ΔS?(cis)) of -2.5 kcal/mol and -6.9 eu, respectively. Mechanistic studies show that the ketone complex (POCOP)Ir(H)(ketone)+ is the catalyst resting state and is in equilibrium with low concentration of the silane complex (POCOP)Ir(H)(HSiR 3)+. The silane complex transfers R3Si + to ketone, forming the oxocarbenium ion R3SiOCR' 2+, which is reduced by the resulting neutral dihydride 3, (POCOP)Ir(H)2, to yield product R3SiOCHR'2 and (POCOP)IrH+, which closes the catalytic cycle.
- Park, Sehoon,Brookhart, Maurice
-
experimental part
p. 6057 - 6064
(2011/02/26)
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- Catalysis by cationic oxorhenium(v): Hydrolysis and alcoholysis of organic silanes
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The cationic [2-(2′-hydroxyphenyl)-2-oxazolinato(-2)]oxorhenium(v) complex 1 promotes oxidative dehydrogenation of organosilanes with water and alcohols in a catalytic manner to give excellent yields of silanols and silyl ethers, respectively. The reactions proceed conveniently under ambient and open-flask conditions with low catalyst loading (≤1 mol%). The scope of the reaction with water is quite broad and includes aliphatic, aromatic, tertiary, secondary and primary silanes. The rate of reaction depends on the catalyst and silane concentrations and kinetic isotope effect measurements demonstrate involvement of the Si-H bond in the activated complex. The most influential factor on the silane affecting reactivity is steric hindrance and a quantitative correlation with the Taft steric parameter (E) is presented. A combination of kinetic data and isotope labelling results are used to discuss plausible mechanisms for the oxidative dehydrogenation reaction pathway.
- Corbin, Rex A.,Ison, Elon A.,Abu-Omar, Mahdi M.
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experimental part
p. 2850 - 2855
(2009/06/27)
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- Scope and mechanism of the iridium-catalyzed cleavage of alkyl ethers with triethylsilane
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The cationic iridium pincer complex [(POCOP)lr(H)(acetone)] +[B(C6F5)4]- {1, POCOP = 2,6 [OP(tBu)2]2C6H3} was found to be a highly active catalyst for the room-temperature cleavage and reduction of a wide variety of unactivated alkyl ethers including primary, secondary, and tertiary alkyl ethers as well as aryl alkyl ethers by triethylsilane. Mechanistic studies have revealed the full details of the catalytic cycle with the catalyst resting state(s) depending on the basicity of the alkyl ether. During the catalytic reduction of diethyl ether, cationic iridium silane complex, [(POCOP)lr(H)(n1-Et3SiH)]+[B(C 6F5]- (3), andEt20 are in rapid equilibrium with neutral dihydride, (POCOP )lr(H)2 (5) and diethyl(triethylsilyl)oxonium ion, [Et3SiOEt2] +[B(C6F5)4]- (7), with 5 + 7 strongly favored. Species 7 has beenisolated from the reaction mixture and fully characterized. The turnove r-limiting step in this cycle is the reduction of 7 by the neutral dihydride 5. The relative rates of reduction of 7 by dihydride 5 and Et3SiH were determined to be ~30,000: 1. In the cleavage of the less basic ethers anisole and EtOSiEt3, the cationic iridium silane complex, 3, was found to be the catalyst resting state. The hydride reduction of the intermediate oxonium ion EtO(SiEt3) 2+, 9, occurs via attack by Et3SiH. In the case of anisole, the intermediate PhMeOSiEt3+, 10, is reduced by 5 and/or Et3SiH.
- Yang, Jian,White, Peter S.,Brookhart, Maurice
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experimental part
p. 17509 - 17518
(2009/09/08)
-
- Catalysts for hydrogenation and hydrosilylation, methods of making and using the same
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A compound is provided including an organometallic complex represented by the formula I: [CpM(CO)2(NHC)Lk]+A???I wherein M is an atom of molybdenum or tangsten, Cp is substituted or unsubstituted cyclopentadienyl radical represented by the formula [C5Q1Q2Q3Q4Q5], wherein Q1to Q5are independently selected from the group consisting of H radical, C1-20hydrocarbyl radical, substituted hydrocarbyl radical, halogen radical, halogen-substituted hydrocarbyl radical, —OR, —C(O)R′, —CO2R′, —SiR′3and —NR′R″, wherein R′ and R″ are independently selected from the group consisting of H radical, C1-20hydrocarbyl radical, halogen radical, and halogen-substituted hydrocarbyl radical, wherein said Q1to Q5radicals are optionally linked to each other to form a stable bridging group, NHC is any N-heterocyclic carbene ligand, L is either any neutral electron donor ligand, wherein k is a number from 0 to 1 or L is an anionic ligand wherein k is 2, and A?is an anion. Processes using the organometallic complex as catalyst for hydrogenation of aldehydes and ketones are provided. Processes using the organometallic complex as catalyst for the hydrosilylation of aldehydes, ketones and esters are also provided.
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-
Page column 19
(2008/06/13)
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- Continuous and batch organomagnesium synthesis of ethyl-substituted silanes from ethylchloride, tetraethoxysilane, and organotrichlorosilane for production of polyethylsiloxane liquids. 2. Continuous one-step synthesis of ethylethoxy- and ethylchlorosilanes
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Development of a continuous one-step manufacturing process for ethylethoxy- and ethylchlorosilanes is described. The methodology of synthesis of ethyl-substituted silanes has been improved. The important factors for the successful synthesis have been determined. Among them are (1) the replacement of some tetraethoxysilane 3 by ethyltrichlorosilane 10, (2) the optimum concentration of 3 and 10, (3) the excess of the granulated magnesium (the supply rate 50-110 g h-1), and, finally, (4) the columnar apparatus with the stirrer, resulting in high yields of di-and triethylsilanes, low duration of synthesis, and high selectivity of Grignard reagent. Continuous one-step synthesis has been assimilated into industry (up to a scale 7-40 kg h-1 of magnesium) for production of oligoethylsiloxanes with low (5-20%) and high content (up to 40%) of the terminal triethylsiloxy groups. The rules for R/D process of the Grignard synthesis are described.
- Klokov, Boris A.
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p. 234 - 240
(2013/09/07)
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- Continuous single-stage organomagnesium synthesis of a mixture of ethylethoxysilanes and dimethylethylethoxysilane
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Simultaneous synthesis of ethylethoxysilanes and dimethylethylethoxysilane from a mixture of ethyl chloride, tetraethoxysilane, and dimethyldichlorosilane with magnesium (supply rate 75-100 g h-1) was studied. Schemes of intermediate processes are proposed. Reactivity of dimethyldichlorosilane and diethyldichlorosilane relative to each other is evaluated. Various grades of magnesium are tested. To reduce the amount of regenerated solvent (toluene) its mixtures with oligodiethylsiloxanes are used. The mixture of ethyl-substituted silanes can be used in subsequent preparation of oligo-ethylsiloxane liquids modified with the terminal dimethylethylsiloxy groups, which are characterised by improved lubricating properties.
- Klokov, Boris A.
-
p. 122 - 128
(2013/09/07)
-
- Continuous and batch organomagnesium synthesis of ethyl-substituted silanes from ethylchloride, tetraethoxysilane, and organotrichlorosilane for production of polyethylsiloxane liquids. 1. Batch one-step synthesis of ethylethoxysilanes and ethylchlorosilanes
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Development of batch one-step manufacturing process for ethylethoxy- and ethylchlorosilanes is desribed. The methodology of synthesis of ethyl-substituted silanes has been improved. The important factors for the successful synthesis have been determined. Among them are the replacement of the part tetraethoxysilane 3 by ethyltrichlorosilane 10, the optimum concentration of 3 and 10 resulting in high yield of triethylsilanes, low duration of synthesis, and high selectivity of Grignard reagent. Batch one-step synthesis has been assimilated into industry (up to a scale 240 kg of magnesium) for production of oligoethylsiloxanes with the high content (>40%) of a terminal triethylsiloxy group. The rules for R/D process of the Grignard synthesis are described.
- Klokov, Boris A.
-
-
- Stepwise organomagnesium synthesis of mixtures of ethyletoxysilanes and ethylchlorosilanes
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Mixture of ethylethoxy- and ethylchlorosilanes was prepared in a toluene solution by successive reaction of magnesium with a mixture of ethyl chloride and tetraethoxysilane and then with a mixture of ethyl chloride and tetrachlorosilane.
- Klokov
-
p. 1863 - 1865
(2007/10/03)
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- Continuous single-stage organomagnesium synthesis of a mixture of ethylethoxysilanes with methylethylphenylethoxysilane
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A continuous reaction of ethyl chloride, tetraethoxysilane, and methylphenyldichlorosilane with magnesium in toluene or in a mixture of toluene with oligoethylsiloxanes was performed in a column apparatus with a stirrer under conditions of counterflow of magnesium and the reagent mixture.
- Klokov
-
p. 1587 - 1592
(2007/10/03)
-
- Continuous organomagnesium synthesis of a mixture of ethylethoxysilanes and methylethyl(thienyl- or haloorgano)ethoxysilane
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Simultaneous synthesis of ethylethoxysilanes and methylethyl(thienyl- or haloorgano)ethoxysilane from a mixture of ethyl chloride, tetraethoxysilane, and methyl(thienyl- or haloorgano)dichlorosilane with magnesium (supply rate 75-100 g h-1) was studied. The mixture of these compounds can be used in subsequent preparation of oligoethylsiloxane liquids modified with the terminal methylethyl(thienyl- or haloorgano)siloxy groups, which are characterized by improved lubricating properties.
- Klokov
-
p. 479 - 482
(2007/10/03)
-
- 2-Ethoxyvinyllithiums and diethoxyvinyllithiums: What makes them stable or fragile?
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The elusive (E)-2-ethoxyvinyllithium can be readily generated in tetrahydrofuran at -75 °C from (E)-1-bromo-2-ethoxyethylene by halogen/metal exchange and subsequently trapped with electrophiles. Alkylation opens a convenient entry to (E)-configurated enethers. (E)-2-Ethoxyvinyllithium decomposes rapidly at -50 °C whereas its (Z)-isomer, which lacks the possibility to eliminate lithium ethoxide in a favorable anti-periplanar process, is stable under the same conditions. (E)-1,2-Diethoxyvinyllithium even sustains reflux temperatures (approximately 75 °C). 2,2-Diethoxyvinyllithium and (Z)-1,2-diethoxyvinyllithium can be conserved at 0 °C although this time loss of alcoholate can occur in the anti-mode. Obviously it matters whether the energy-rich ethoxyacetylene is formed as the elimination product or simple acetylene, as in the case of (E)-2-ethoxyvinyllithium.
- Schlosser, Manfred,Wei, Heng-Xu
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p. 1735 - 1742
(2007/10/03)
-
- An Efficient Catalyst for the Conversion of Hydrosilanes to Alkoxysilanes
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The copper(I) hydride 6 is an efficient catalyst for the alcoholysis of primary and secondary silanes.The reactions proceed at room temperature within a few hours and give the alkoxysilanes in high yields.Only with bulky alcohols or silanes are longer reaction times and/or increased temperatures required.The presence of air accelarates the reactions and gives rise to higher yields of alkoxysilanes, particularly with bulky alcohols.Diols react with PhRSiH2 (R = Me, Ph) to afford 1,3-dioxo-2-silacycloalkanes and with tertiary silanes to furnish the bissilylated diols.When unsaturated alcohols (2-propen-1-ol or 2-propyn-1-ol) are employed, the double or triple bond is retained. - Keywords: Catalytic silane alcoholysis; Alkoxysilanes
- Lorenz, Catrin,Schubert, Ulrich
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p. 1267 - 1270
(2007/10/03)
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- Continuous Single-Stage Organomagnesium Synthesis of Ethylethoxysilanes and Ethylchlorosilanes from a Mixture of Tetraethoxysilane and Diethylchlorosilane
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Basic parameters are presented of novel highly efficient technology for the synthesis of organosilicon monomers for producing practically useful polyethylsiloxane liquids.
- Klokov, B. A.
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p. 100 - 104
(2007/10/03)
-
- REACTION OF OXYGEN-CONTAINING MONOMERS WITH TRIETHYLSILANE IN THE PRESENCE OF IRON, MANGANESE, AND RHENIUM CARBONYLS
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A study was carried out on the reaction of triethylsilane (TES) with acrolein, the diethyl acetal of acrolein, and allyl alcohol in the presence of Fe(CO)5, Mn2(CO)10, and Re2(CO)10.Acrolein reacts with TES in the presence of Fe(CO)5 to give the 1,4-addition product in high yield.The reaction of the diethyl acetal of acrolein largely features cleavage of the C-O bond and formation of Et3SiOEt.Allyl alcohol reacts with TES in the presence of Fe(CO)5, Mn2(CO)10, and Re2(CO)10 to give the dehydrocondensation product, namely, triethylallyoxysilane, which undergoes hydrogenation and hydroxylation to give triethylpropyloxysilane and γ-(triethylsilyloxy)propyltriethylsilane, respectively.The yields of these products depend on the metal carbonyl used.
- Savos'kina, I. V.,Kuz'mina, N. A.,Galust'yan, G. G.
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p. 420 - 422
(2007/10/02)
-
- Iodine- or Iodine Monobromide-Catalyzed Alkoxy-Alkoxy Exchange Reactions of Alkylalkoxysilanes: Formation of the Catalyst-Alkoxysilane Complexes and the Reaction Mechanism
-
The formation of charge-transfer complexes of iodine and of iodine monobromide with alcohols and alkoxysilanes has been established spectroscopically, and the formation constants of iodine-ethoxytriethylsilane and iodine-diethoxydimethylsilane complexes has been determined as 0.55+/-0.01 and 0.61+/-0.02, respectively.On the basis of these observations and the kinetic information recently reported, the previously proposed mechanism for the iodine or iodine monobromide catalyzed alkoxy-alkoxy exchange reactions of alkoxysilanes is dicussed afresh.It has been confirmed that a mechanism involving a four-centered transition state containing a CT-complex is most favorable.
- Ito, Katsuko,Ibaraki, Takeshi
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p. 2853 - 2858
(2007/10/02)
-
- Alcoholysis Equilibria of Triethylalkoxysilanes Catalyzed by Iodine or Iodine Monobromide
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The equilibrium constants K of alcoholysis of triethylalkoxysilanes were determined at 20 degC and 40 degC.Iodine monobromide was used to promote the reactions associated with the tertiary alkoxyl groups, while the other reactions proceeded in the presence of iodine.The K values of the reaction systems with ethoxyl or propoxyl-primary, secondary, and tertiary alkoxyl pairs were 1 or above, about 0.5, and about 0.05, respectively.These values reflect the extent of the binding abilities of the alkoxyl groups to silicon, which is in the expected order of primary>secondary>tertiary alkoxyl groups.A mechanism is postulated for the reaction which involves participation by the iodine or iodine monobromide.
- Ito, Katsuko,Ibaraki, Takeshi
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p. 2973 - 2975
(2007/10/02)
-