- Photochemical reactions of [CH2(η5-C 5H4)2][Rh(C2H4) 2]2 with silanes: Evidence for Si-C and C-H activation pathways
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Photochemical reaction of [CH2(η5-C 5H4)2][Rh(C2H4) 2]2 1 with dmso led to the stepwise formation of [CH 2(η5-C5H4)2] [Rh(C2H4)2][Rh(C2H 4)(dmso)] 2a and [CH2(η5-C 5H4)2][Rh(C2H4)(dmso)] 2 2b. Photolysis of 1 with vinyltrimethylsilane ultimately yields three isomeric products of [CH2(η5-C5H 4)2][Rh(CH2=CHSiMe3) 2]2, 3a,3b and 3c which are differentiated by the relative orientations of the vinylsilane. When this reaction is undertaken in d 6-benzene, H/D exchange between the solvent and the α-proton of the vinylsilane is revealed. In addition evidence for two isomers of the solvent complex [CH2(η5-C5H 4)2][Rh(C2H4)2][Rh(C 2H4)(η2-toluene)] was obtained in these and related experiments when the photolysis was completed at low temperature without substrate, although no evidence for H/D exchange was observed. Photolysis of 1 with Et3SiH yielded the sequential substitution products [CH2(η5-C5H4) 2][Rh(C2H4)2][Rh(C2H 4)(SiEt3)H] 4a, [CH2(η5-C 5H4)2][Rh(C2H4)(SiEt 3)H]2 4b, [CH2(η5-C 5H4)2]-[Rh(C2H4) (SiEt3)H][Rh(SiEt3)2(H)2] 4c and [CH2(η5-C5H4) 2][Rh(SiEt3)2(H)2]2 4d; deuteration of the α-ring proton sites, and all the silyl protons, of 4d was demonstrated in d6-benzene. This reaction is further complicated by the formation of two Si-C bond activation products, [CH2(η 5-C5H4)2][RhH(μ-SiEt 2)]2 5 and [CH2(η5-C 5H4)2][(RhEt)(RhH)(μ-SiEt2) 2] 6. Complex 5 was also produced when 1 was photolysed with Et 2SiH2. When the photochemical reactions with Et 3SiH were repeated at low temperatures, two isomers of the unstable C-H activation products, the vinyl hydrides [CH2(η5- C5H4)2][{Rh(SiEt3)H}{Rh(SiEt 3)}(μ-η1,η2-CH=CH2)] 7a and 7b, were obtained. Thermally, 4c was shown to form the ring substituted silyl migration products [(η5-C5H4)CH 2(C5H3SiEt3)][Rh(SiEt 3)2(H)2]2 8 while 4b formed [CH 2(C5H3SiEt3)2] [Rh(SiEt3)2(H)2]2 (9a and 9b) upon reaction with excess silane. The corresponding photochemical reaction with Me3SiH yielded the expected products [CH2(η 5-C5H4)2][Rh(C2H 4)2][Rh(C2H4)(SiMe3)H] 10a, [CH2(η5-C5H4) 2][Rh(C2H4)(SiMe3)H]2 10b, [CH2(η5-C5H4) 2][Rh(C2H4)(SiMe3)H][Rh(SiMe 3)2(H)2] 10c and [CH2(η 5-C5H4)2][Rh(SiMe3) 2(H)2]2 10d. However, three Si-C bond activation products, [CH2(η5-C5H 4)2][(RhMe)(RhH)(μ-SiMe2)2] 11, [CH2(η5-C5H4) 2][(Rh{SiMe3})(RhMe)(μ-SiMe2)2] 12 and [CH2(η5-C5H4) 2][(Rh{SiMe3})(RhH)(μ-SiMe2)2] 13 were also obtained in these reactions. The Royal Society of Chemistry 2005.
- Cunningham, Jenny L.,Duckett, Simon B.
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Read Online
- Kinetics and Thermochemistry of the Reaction Si(CH3)3 + HBr -->/<-- Si(CH3)3H + Br: Determination of the (CH3)3Si-H Bond Energy
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The reaction Si(CH3)3 + HBr --> Si(CH3)3H + Br (1) has been investigated using flash photolysis/photoionization mass spectrometry detection of Si(CH3)3 and flash photolysis/resonance fluorescence spectroscopy detection of Br.The measured rate constants ar
- Kalinovski, Ilia J.,Gutman, D.,Krasnoperov, Lev N.,Goumri, A.,Yuan, W.-J.,Marshall, Paul
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Read Online
- Co2(CO)8-catalyzed reactions of acetals or lactones with hydrosilanes and carbon monoxide. A new access to the preparation of 1,2-diol derivatives through siloxymethylation
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The Co2(CO)8-catalyzed reaction of acetals with hydrosilanes and CO under mild reaction conditions (an ambient temperature under an ambient CO pressure), leading to the production of vicinal diols is reported. A siloxymethyl group can be introduced via the cleavage of one of two alkoxy groups in the acetal. The effects of the types of hydrosilanes, acetals, solvents, and reaction temperatures on the yield of siloxymethylation products were examined in detail. The reactivity for hydrosilanes is as follows; HSiMe3 > HSiEtMe2 > HSiEt2Me > HSiEt3. Hemiacetal esters are more reactive than dimethyl acetals. The polarity of the solvent used also has a significant effect on both the course of the reaction as well as the reaction rate. The site-selective siloxymethylation can be achieved in the case of cyclic acetals such as tetrahydrofuran (THF) and tetrahydropyrane (THP) derivatives, depending on the nature of the oxygen substituent attached adjacent to the oxygen atom in the ring. When 2-alkoxy THF or THP derivatives are used as substrates, the siloxymethylation takes place with cleavage of the ring C-O bond. In contrast, the reaction of 2-acetoxy THF or THP derivatives results in siloxymethylation with the cleavage of C-OAc bond. The ring-opening siloxymethylation of lactones was also examined.
- Chatani, Naoto,Fujii, Satoru,Kido, Yoichi,Nakayama, Yasuhide,Kajikawa, Yasuteru,Tokuhisa, Hideo,Fukumoto, Yoshiya,Murai, Shinji
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- Unlocking the Catalytic Hydrogenolysis of Chlorosilanes into Hydrosilanes with Superbases
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The efficient synthesis of hydrosilanes by catalytic hydrogenolysis of chlorosilanes is described using an iridium (III) pincer catalyst. A careful selection of a nitrogen base (including sterically hindered guanidines and phosphazenes) can unlock the preparation of Me3SiH, Et3SiH, and Me2SiHCl in high yield (up to 98%) directly from their corresponding chlorosilanes.
- Durin, Gabriel,Berthet, Jean-Claude,Nicolas, Emmanuel,Cantat, Thibault
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p. 10855 - 10861
(2021/09/08)
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- Hydrogenolysis of Polysilanes Catalyzed by Low-Valent Nickel Complexes
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The dehydrogenation of organosilanes (RxSiH4?x) under the formation of Si?Si bonds is an intensively investigated process leading to oligo- or polysilanes. The reverse reaction is little studied. To date, the hydrogenolysis of Si?Si bonds requires very harsh conditions and is very unselective, leading to multiple side products. Herein, we describe a new catalytic hydrogenation of oligo- and polysilanes that is highly selective and proceeds under mild conditions. New low-valent nickel hydride complexes are used as catalysts and secondary silanes, RR′SiH2, are obtained as products in high purity.
- Comas-Vives, Aleix,Eiler, Frederik,Grützmacher, Hansj?rg,Pribanic, Bruno,Trincado, Monica,Vogt, Matthias
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supporting information
p. 15603 - 15609
(2020/04/29)
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- DISILANE-, CARBODISILANE-AND OLIGOSILANE CLEAVAGE WITH CLEAVAGE COMPOUND ACTING AS CATALYST AND HYDROGENATION SOURCE
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The invention relates to a process for the manufacture of monosilanes of formula (I): MexSiHyClz (I), comprising: the step of subjecting a silane substrate (methyldisilanes, methyloligosilanes, or carbodisilanes) to a cleavage reaction of the silicon-silicon bond(s) or the silicon- carbon bonds in silane substrates the reaction involving a cleavage compound selected from a quaternary Group 15 onium compound R4 QX, a heterocyclic amine, a heterocyclic ammonium halide, or a mixture of R3P and RX. The starting material disilanes to be cleaved has the formula (II): MemSi2HnClo (II) The starting material oligosilanes to be cleaved have the general formula (III): MepSiqHrCIs (II I), The starting material carbodisilanes to be cleaved have the general formula (IV): (MeaSiHbCle)-CH2-(MecSiHdClf) (IV)
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Page/Page column 39; 40
(2019/04/16)
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- Dual Role of Doubly Reduced Arylboranes as Dihydrogen- and Hydride-Transfer Catalysts
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Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M2[DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC8. In the first step, the ambiphilic M2[DBA] activate H2 in a concerted, metal-like fashion. The rates of H2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li+ ions, which form persistent contact ion pairs with [DBA]2-, slow the H2-addition rate to a higher extent than more weakly coordinating Na+/K+ ions. For the hydrogenation of unsaturated compounds, we identified Li2[4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)CNtBu, Ph2CCH2, and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na2[4]. The latter protocol provides facile access also to Me2Si(H)Cl, a most important silicone building block. Whereas the H2-transfer reaction regenerates the dianion [4]2- and is thus immediately catalytic, the H--transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process).
- Von Grotthuss, Esther,Prey, Sven E.,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
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supporting information
(2019/04/17)
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- Dual Role of Doubly Reduced Arylboranes as Dihydrogen- and Hydride-Transfer Catalysts
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Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M2[DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC8. In the first step, the ambiphilic M2[DBA] activate H2 in a concerted, metal-like fashion. The rates of H2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li+ ions, which form persistent contact ion pairs with [DBA]2-, slow the H2-addition rate to a higher extent than more weakly coordinating Na+/K+ ions. For the hydrogenation of unsaturated compounds, we identified Li2[4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)C=NtBu, Ph2C=CH2, and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na2[4]. The latter protocol provides facile access also to Me2Si(H)Cl, a most important silicone building block. Whereas the H2-transfer reaction regenerates the dianion [4]2- and is thus immediately catalytic, the H--transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process).
- Von Grotthuss, Esther,Prey, Sven E.,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
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supporting information
p. 6082 - 6091
(2019/04/17)
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- Disilane Cleavage with Selected Alkali and Alkaline Earth Metal Salts
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The industry-scale production of methylchloromonosilanes in the Müller–Rochow Direct Process is accompanied by the formation of a residue, the direct process residue (DPR), comprised of disilanes MenSi2Cl6-n (n=1–6). Great research efforts have been devoted to the recycling of these disilanes into monosilanes to allow reintroduction into the siloxane production chain. In this work, disilane cleavage by using alkali and alkaline earth metal salts is reported. The reaction with metal hydrides, in particular lithium hydride (LiH), leads to efficient reduction of chlorine containing disilanes but also induces disproportionation into mono- and oligosilanes. Alkali and alkaline earth chlorides, formed in the course of the reduction, specifically induce disproportionation of highly chlorinated disilanes, whereas highly methylated disilanes (n>3) remain unreacted. Nearly quantitative DPR conversion into monosilanes was achieved by using concentrated HCl/ether solutions in the presence of lithium chloride.
- Santowski, Tobias,Sturm, Alexander G.,Lewis, Kenrick M.,Felder, Thorsten,Holthausen, Max C.,Auner, Norbert
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supporting information
p. 13202 - 13207
(2019/10/22)
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- METHOF FOR PRODUCING HYDRIDOSILANES
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The invention relates to a method for producing hydridosilanes, in which siloxanes containing Si—H groups are reacted in the presence of a cationic Si(II) compound as a catalyst.
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Paragraph 0061-0062
(2019/11/22)
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- Synthesis of Functional Monosilanes by Disilane Cleavage with Phosphonium Chlorides
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The Müller–Rochow direct process (DP) for the large-scale production of methylchlorosilanes MenSiCl4?n (n=1–3) generates a disilane residue (MenSi2Cl6?n, n=1–6, DPR) in thousands of tons annually. This report is on methylchlorodisilane cleavage reactions with use of phosphonium chlorides as the cleavage catalysts and reaction partners to preferably obtain bifunctional monosilanes MexSiHyClz (x=2, y=z=1; x,y=1, z=2; x=z=1, y=2). Product formation is controlled by the reaction temperature, the amount of phosphonium chloride employed, the choice of substituents at the phosphorus atom, and optionally by the presence of hydrogen chloride, dissolved in ethers, in the reaction mixture. Replacement of chloro by hydrido substituents at the disilane backbone strongly increases the overall efficiency of disilane cleavage, which allows nearly quantitative silane monomer formation under comparably moderate conditions. This efficient workup of the DPR thus not only increases the economic value of the DP, but also minimizes environmental pollution.
- Santowski, Tobias,Sturm, Alexander G.,Lewis, Kenrick M.,Felder, Thorsten,Holthausen, Max C.,Auner, Norbert
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supporting information
p. 3809 - 3815
(2019/02/13)
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- CLEAVAGE OF METHYLDISILANES TO METHYLMONOSILANES
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The invention relates to a process for the manufacture of methylmonosilanes comprising the step of subjecting one or more methyldisilanes to the cleavage reaction of the silicon-silicon bond, and optionally a step of separating the resulting methylmonosilanes.
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Page/Page column 29
(2019/04/16)
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- Making Use of the Direct Process Residue: Synthesis of Bifunctional Monosilanes
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The industrial production of monosilanes MenSiCl4?n (n=1–3) through the Müller–Rochow Direct Process generates disilanes MenSi2Cl6?n (n=2–6) as unwanted byproducts (“Direct Process Residue”, DPR) by the thousands of tons annually, large quantities of which are usually disposed of by incineration. Herein we report a surprisingly facile and highly effective protocol for conversion of the DPR: hydrogenation with complex metal hydrides followed by Si?Si bond cleavage with HCl/ether solutions gives (mostly bifunctional) monosilanes in excellent yields. Competing side reactions are efficiently suppressed by the appropriate choice of reaction conditions.
- Sturm, Alexander G.,Santowski, Tobias,Schweizer, Julia I.,Meyer, Lioba,Lewis, Kenrick M.,Felder, Thorsten,Auner, Norbert,Holthausen, Max C.
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supporting information
p. 8499 - 8502
(2019/06/13)
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- Method for preparing hydrogen silane by using calcium hydride to conduct reduction on chlorosilane
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The invention discloses a method for preparing hydrogen silane by using calcium hydride to conduct reduction on chlorosilane and belongs to the technical field of chlorosilane reduction. The problemsof harsh reaction conditions, low reaction speed and the like of chlorosilane reduction through CaH2 in the prior art are solved. In an organic solvent, under catalysis of a catalyst, calcium hydrideis used as a reducing agent, and chlorosilane is reduced into hydrogen silane; the catalyst is borane or borohydride or lithium aluminum hydride, and the organic solvent is tetrahydrofuran or diethylene glycol dimethyl ether or other ether solvents. The method can be applied to hydrogen silane preparation through chlorosilane reduction.
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Paragraph 0092-0093
(2018/07/30)
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- Hydrosilane synthesis via catalytic hydrogenolysis of halosilanes using a metal-ligand bifunctional iridium catalyst
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Hydrogenolysis of various halosilanes was catalysed by iridium amido complexes to produce hydrosilanes. Selective monohydrogenolysis of di- and trichlorosilanes similarly proceeded, resulting in the formation of chlorohydrosilanes (R2SiHCl or RSiHCl2) as synthetically important building blocks for various organosilicon compounds. A mechanistic study supported the in-situ formation of an iridium hydride species as a key intermediate, which could transfer the hydride to the silicon atom through a metal–ligand bifunctional mechanism. One-pot hydrotrimethylsilylation of olefins was achieved via successive hydrogenolysis and hydrosilylation reactions starting from Me3SiCl.
- Beppu, Teruo,Sakamoto, Kei,Nakajima, Yumiko,Matsumoto, Kazuhiro,Sato, Kazuhiko,Shimada, Shigeru
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- PRODUCTION METHOD OF HYDROSILANE
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PROBLEM TO BE SOLVED: To provide a production method of hydrosilane capable of producing hydrosilane efficiently. SOLUTION: Silane having a structure shown by formula (a) is reacted with hydrogen in the presence of iridium complex shown by formula (I) and organic base, to thereby produce hydrosilane efficiently. SELECTED DRAWING: None COPYRIGHT: (C)2018,JPOandINPIT
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Paragraph 0037; 0047
(2018/10/03)
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- Hydrosilane Synthesis by Catalytic Hydrogenolysis of Chlorosilanes and Silyl Triflates
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Hydrogenolysis of the chlorosilanes and silyl triflates (triflate = trifluoromethanesulfonate, OTf-) Me3-nSiX1+n (X = Cl, OTf; n = 0, 1) to hydrosilanes at mild conditions (4 bar of H2, room temperature) is reported using low loadings (1 mol %) of the bifunctional catalyst [Ru(H)2CO(HPNPiPr)] (HPNPiPr = HN(CH2CH2P(iPr)2)2). Endergonic chlorosilane hydrogenolysis can be driven by chloride removal, e.g., with NaBArF4 [BArF4- = B(C6H3-3,5-(CF3)2)4-]. Alternatively, conversion to silyl triflates enables facile hydrogenolysis with NEt3 as the base, giving Me3SiH, Me2SiH2, and Me2SiHOTf, respectively, in high yields. An outer-sphere mechanism for silyl triflate hydrogenolysis is supported by density functional theory computations. These protocols provide key steps for synthesis of the valuable hydrochlorosilane Me2SiClH, which can also be directly obtained in yields of over 50% by hydrogenolysis of chlorosilane/silyl triflate mixtures.
- Glüer, Arne,Schweizer, Julia I.,Karaca, Uhut S.,Würtele, Christian,Diefenbach, Martin,Holthausen, Max C.,Schneider, Sven
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p. 13822 - 13828
(2018/10/24)
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- METHOD FOR PRODUCING HYDROSILANE USING BORANE REDUCTION
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PROBLEM TO BE SOLVED: To provide a method for producing hydrosilane that can efficiently produce the hydrosilane. SOLUTION: In the presence of a Lewis base, a silane having a structure represented by a formula (a) reacts with a borane complex or diborane, to efficiently produce hydrosilane (in the formula (a), R1 is a C1 to C20 hydrocarbon group, or a C1 to C10 acyl group). SELECTED DRAWING: None COPYRIGHT: (C)2018,JPOandINPIT
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Paragraph 0022
(2018/07/28)
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- B(C6F5)3-Catalyzed C-Si/Si-H Cross-Metathesis of Hydrosilanes
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The substituent redistribution of hydrosilanes on silicon through C-Si and Si-H bond cleavage and reformation is of great interest and importance, but this transformation is usually difficult to achieve in a selective fashion. By using electron-rich aromatic hydrosilanes, we have achieved for the first time the selective C-Si/Si-H bond homo- and cross-metathesis of a series of hydrosilanes in the presence of a boron catalyst B(C6F5)3. This protocol features simple reaction conditions, high chemoselectivity, wide substrate scope, and high functionality tolerance, offering a new pathway for the synthesis of multisubstituted functional silanes.
- Ma, Yuanhong,Zhang, Liang,Luo, Yong,Nishiura, Masayoshi,Hou, Zhaomin
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supporting information
p. 12434 - 12437
(2017/09/25)
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- DMF-activated chlorosilane chemistry: Molybdenum-catalyzed reactions of R3SiH, DMF and R′3SiCl to initially form R′3SiOSiR′3 and R3SiCl
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The room temperature reactions between R3SiH (R3?=?Et3, PhMe2, Ph2Me) and R′3SiCl (R′3?=?Me3, PhMe2, Ph2Me), with an excess of dimethylformamide (DMF) in the presence of (Me3N)Mo(CO)5 as a catalyst, result in the initial formation of R3SiCl, R′3SiOSiR′3 and Me3N as detected by 29Si, 13C, 1H NMR spectroscopy and GC/MS. As the reaction proceeds, the more so if the reaction temperature is raised, mixed disiloxanes R3SiOSiR′3 and ultimately lesser amounts of R3SiOSiR3 may be detected. A mechanism involving the activation of chlorosilanes by the nucleophilic DMF is proposed to produce transient imminium siloxy ion pairs, [Me2N[dbnd]CHCl]+[R′3SiO]? ? [Me2N[dbnd]CH(OSiR′3)]+Cl? which react with R3SiH to form Me2NCH2OSiR′3 and R3SiCl. A secondary reaction of Me2NCH2OSiR′3 with R′3SiCl produces the symmetrical disiloxane R′3SiOSiR′3 and ClCH2NMe2. The final stage of the reaction is the reduction of ClCH2NMe2 by R3SiH, a reaction which is reported for the first time. The newly created chlorosilane R3SiCl can become involved in the initial DMF activation chemistry thereby forming the other disiloxanes observed as the reaction proceeds.
- Gonzalez, Paulina E.,Sharma, Hemant K.,Pannell, Keith H.
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p. 376 - 381
(2017/06/30)
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- One-Step Synthesis of Siloxanes from the Direct Process Disilane Residue
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The well-established Müller–Rochow Direct Process for the chloromethylsilane synthesis produces a disilane residue (DPR) consisting of compounds MenSi2Cl6?n(n=1–6) in thousands of tons annually. Technologically, much effort is made to retransfer the disilanes into monosilanes suitable for introduction into the siloxane production chain for increase in economic value. Here, we report on a single step reaction to directly form cyclic, linear, and cage-like siloxanes upon treatment of the DPR with a 5 m HCl in Et2O solution at about 120 °C for 60 h. For simplification of the Si?Si bond cleavage and aiming on product selectivity the grade of methylation at the silicon backbone is increased to n≥4. Moreover, the HCl/Et2O reagent is also suitable to produce siloxanes from the corresponding monosilanes under comparable conditions.
- Neumeyer, Felix,Auner, Norbert
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supporting information
p. 17165 - 17168
(2016/11/23)
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- PRODUCTION METHOD OF HYDROSILANE COMPOUND
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PROBLEM TO BE SOLVED: To provide a new production method of a hydrosilane compound. SOLUTION: A hydrosilane compound can be efficiently produced by making an iridium complex having a dialkyl benzimidazole-2-ylidene ligand represented by formula (L1) and a phosphine ligand represented by formula (L2) coexist with a base and gaseous hydrogen so that a nucleophilic substitution reaction (hydride-reduction) of a silane compound, being a raw material compound, with a hydride ion (H-) proceeds (in formulas (L1) and (L2), each of R4 independently represents a 1-6C hydrocarbon group, each of R5 independently represents a 1-6C hydrocarbon group, each of R6 independently represents a 1-10C hydrocarbon group, and n represents an integer of 0-4). SELECTED DRAWING: None COPYRIGHT: (C)2016,JPOandINPIT
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Paragraph 0020; 0021
(2016/10/07)
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- METHOD FOR PREPARING AN ORGANO-FUNCTIONAL SILANE
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A process includes reacting an organometallic cuprate and a silicon precursor in the presence of a solvent. The process produces a reaction product including an organo-functional silane.
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Paragraph 0027
(2014/05/24)
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- Activation of Si-Si and Si-H bonds at Pt: A catalytic hydrogenolysis of silicon-silicon bonds
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The activation of Ph2HSiSiHPh2 and Me 3SiSiMe3 at [Pt(PEt3)3] (1) yielded the products of oxidative addition. The formation of [Pt(SiHPh2) 2(PEt3)2] (2) as a mixture of the cis and trans isomers appears to proceed quantitatively, whereas a conversion to give cis-[Pt(SiMe3)2(PEt3)2] (3) was not complete. Treatment of 1 with one equivalent of H2SiPh2 led to cis-and trans-[Pt(H)(SiHPh2)(PEt3)2] (cis-4, trans-4) together with the dinuclear complex [(Et3P) 2(H)Pt(μ-SiPh2)(μ-η2-HSiPh 2)Pt(PEt3)] (5). In contrast, HSiMe3 reacts with [Pt(PEt3)3] to yield cis-[Pt(H)(SiMe 3)(PEt3)2] (7) exclusively. Catalytic reactions of dihydrogen with the disilanes Ph2HSiSiHPh2 or Me 3SiSiMe3 in the presence of catalytic amounts of [Pt(PEt3)3] (1) led to the products of hydrogenolysis, H2SiPh2 and HSiMe3. The conversion of Me 3SiSiMe3 is much slower and needs higher temperature to proceed.
- Voigt, Jan,Chilleck, Maren A.,Braun, Thomas
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p. 4052 - 4058
(2013/04/10)
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- 3-silylated cyclohexa-1,4-dienes as precursors for gaseous hydrosilanes: The B(C6F5)3-catalyzed transfer hydrosilylation of alkenes
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Set Me3SiH free! The strong Lewis acid B(C6F 5)3 catalyzes the release of hydrosilanes from 3-silylated cyclohexa-1,4-dienes with concomitant formation of benzene. Subsequent B(C 6F5)3
- Simonneau, Antoine,Oestreich, Martin
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supporting information
p. 11905 - 11907
(2013/11/19)
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- Intermolecular β-hydrogen abstraction in ytterbium, calcium, and potassium tris(dimethylsilyl)methyl compounds
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A series of organometallic compounds containing the tris(dimethylsilyl) methyl ligand are described. The potassium carbanions KC(SiHMe2) 3 and {KC(SiHMe2)3TMEDA}2 are synthesized by deprotonation of the hydrocarbon HC(SiHMe2) 3 with potassium benzyl. {KC(SiHMe2)3TMEDA} 2 crystallizes as a dimer with two types of three-center-two-electron K-H-Si interactions: side-on coordination of SiH (∠K-H-Si = 102(2)) and more obtuse K-H-Si structures (∠K-H-Si ≈ 150). The divalent calcium and ytterbium compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = 2THF, TMEDA) are prepared from MI2 and 2 equiv of KC(SiHMe2)3. Low 1JSiH coupling constants in the NMR spectra, low-energy νSiH bands in the IR spectra, and short M-Si distances and small M-C-Si angles in the crystal structures suggest β-agostic interactions on each C(SiHMe2) 3 ligand. The IR assignments of M{C(SiHMe2) 3}2L (L = 2THF, TMEDA) are supported by DFT calculations. The compounds M{C(SiHMe2)3}2L react with 1 or 2 equiv of B(C6F5)3 to give the 1,3-disilacyclobutane {Me2SiC(SiHMe2)2} 2 and MC(SiHMe2)3HB(C6F 5)3L or M{HB(C6F5)3} 2L, respectively. In addition, M{C(SiHMe2) 3}2L compounds react with BPh3 to give β-H abstracted products. The compounds M{C(SiHMe2)3} 2THF2 react with SiMe3I to yield Me 3SiH and disilacyclobutane as the products of β-H abstraction, while M{C(SiHMe2)3}2TMEDA and Me3SiI form a mixture of Me3SiH and the alkylation product Me 3SiC(SiHMe2)3 in a 1:3 ratio.
- Yan, Kaking,Schoendorff, George,Upton, Brianna M.,Ellern, Arkady,Windus, Theresa L.,Sadow, Aaron D.
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p. 1300 - 1316
(2013/05/21)
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- Reactions of amine-and phosphane-borane adducts with frustrated Lewis pair combinations of Group 14 triflates and sterically hindered nitrogen bases
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The ability of trialkyl Group 14 triflates in combination with amine and pyridine bases to dehydrogenate amine-and phosphane-borane adducts has been investigated. By using multinuclear NMR spectroscopy, it has been shown that Me2NH ·BH3 (11) is efficiently converted to [Me2N-BH2]2 (12) by the so-called "frustrated Lewis pair" (FLP) of nBu3SnOTf (4, -OTf = -OSO2CF3) and 2,2,6,6-tetramethylpiperidine (6). Within the scope of the study, exchange of the Lewis acid effects the rate of dehydrogenation in the order: 4 gt; Me3Si-OTf (2) gt; Et 3SiOTf (3). Exchange of the Lewis base for 2,6-di-tert-butylpyridine (5) has also been shown to reduce the rate of reaction, whereas 1,3-di-tert-butylimidazol-2-ylidene (7) reacted directly with 2 to afford 1,3-bis-tert-butyl-4-(trimethylsilyl)imidazolium triflate (8[OTf]). For FLP combinations for which dehydrogenation reaction times are longer, detectable quantities of [H2B(μ-H)(μ-NMe2)BH2] (14) are observed. Both the dehydrogenation reaction and competitive formation of this product are proposed to proceed by initial hydride abstraction by the Lewis acid, followed by deprotonation by the Lewis base, or combination with further dimethylamine-borane and elimination of [Me2NH2]OTf (18[OTf]), respectively. In contrast to 11, MeNH2·BH 3 (22) was not found to cleanly dehydrogenate to either [MeNH-BH 2]3 or [MeN-BH]3 under the same conditions. An alternative reaction pathway was observed with either 2 or 4 and 6 with Ph 2PH ·BH3 (23), resulting in P-silylation or P-stannylation of the phosphane-borane, respectively.
- Whittell, George R.,Balmond, Edward I.,Robertson, Alasdair P. M.,Patra, Sanjib K.,Haddow, Mairi F.,Manners, Ian
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experimental part
p. 3967 - 3975
(2011/01/11)
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- Effect of catalyst structure on the reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane
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Reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane in the presence of the complexes of platinum(II), palladium(II) and rhodium(I) is explored. It is established that in the presence of platinum catalyst predominantly occurs hydrosilylation of α-methylstyrene leading to formation of β-adduct, on palladium catalysts proceeds reduction of α-methylstyrene, on rhodium catalysts both the processes take place. In the reaction mixture proceeds disproportion and dehydrocondensation of 1,1,3,3-tetramethyldisiloxane that leads to formation of long chain linear and cyclic siloxanes of general formula HMe2Si(OSiMe2) n H and (-OSiMe2-)m (n = 2-6, m = 3-7), respectively. Platinum catalysts promotes formation of linear siloxanes, while both rhodium and palladium catalysts afford linear and cyclic siloxanes as well. Structure of intermediate metallocomplexes is studied.
- De Vekki,Skvortsov
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body text
p. 762 - 777
(2009/09/26)
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- METHODS AND APPARATUS FOR FORMING GASEOUS ORGANOSILICON COMPOUNDS
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The present application is directed to a method for producing, from a solid organosilane compound, a mixture of gaseous organosilicon compounds having a desired molar ratio, the method comprising the step of pyrolysing the solid organosilane while maintaining a predetermined pressure which is selected to provide the desired molar ratio of gaseous organosilicon compounds. Associated apparatus and control mechanisms are also disclosed.
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Page/Page column 35-39
(2009/07/03)
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- Early main-group metal catalysts for the hydrogenation of alkenes with H2
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(Chemical Equation Presented) Transition-metal-free hydrogenation of alkenes can be carried out with simple organocalcium catalysts (20 bar H 2, 20°C). Both steps in the proposed catalytic cycle, hydride addition to the double bond and σ-bond metathesis with H2, have been confirmed. Alkenes sensitive to polymerization are also hydrogenated in good yields.
- Spielmann, Jan,Buch, Frank,Harder, Sjoerd
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body text
p. 9434 - 9438
(2009/05/06)
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- METHOD FOR PRODUCING ORGANOSILANE
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By reducing an organosilane represented by the formula (1), €?€?€?€?€?€?€?€?SiX n R 4-n €?€?€?€?€?(1) (wherein X represents a halogen or alkoxide, n represents an integer of 1-3, and R represents an alkyl group or aryl group), there is produced a corresponding organosilane represented by the formula (2), €?€?€?€?€?€?€?€?SiH n R 4-n €?€?€?€?€?(2) (wherein n represents an integer of 1-3, and R represents an alkyl group or aryl group). In this production method, an aromatic hydrocarbon series organic solvent is used as a reaction solvent, and aluminum lithium hydride is used as a hydrogenating agent.
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Page/Page column 4
(2008/06/13)
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- Synthesis, structure, and reactivity of hydridobis(silylene)ruthenium(IV)- xantsil complexes (xantsil = (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilyl)) - A stabilized form of key intermediates in the catalytic oligomerization- deoligomerization of hydrosilanes
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Ru {K2(Si,Si)-xantsil}(CO)(η6-C6H 5CH3) (1) was found to be a catalyst for oligomerization-deoligomerization of HSiMe2SiMe3 to give H(SiMe2)nMe (n = 1-8 at 90°C for 2 days). Treatment of 1 with HSiMe2SiMe2OR (R = Me, f-Bu) led to quantitative formation of Ru{κ3(O,Si,Si)-xantsil}(CO)(H) {(SiMe2...O(R)...SiMe2)} (R = Me (2a), t-Bu (2b)), which also worked as a catalyst for oligomerization-deoligomerization of HSiMe2SiMe3. Based on these experimental results, a mechanism involving silyl(silylene) intermediates was proposed for the oligomerization-deoligomerization of HSiMe2SiMe3. Complex 2a reacted with MeOH in toluene-d8 to give Ru{κ 2(Si,Si)-xantsil}(CO)(η6-toluene-d8) and Me2Si(OMe)2 with evolution of H2. Under a CO atmosphere, 2a was smoothly converted to its CO adduct Ru{κ 2(Si-Si)-xantsil}(CO)2(H){(SiMe2...O(Me) ...SiMe2)} (3).
- Okazaki, Masaaki,Minglana, Jim Josephus Gabrillo,Yamahira, Nobukazu,Tobita, Hiromi,Ogino, Hiroshi
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p. 1350 - 1358
(2007/10/03)
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- Novel catalytic hydrogenolysis of silyl enol ethers by the use of acidic ruthenium dihydrogen complexes
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Treatment of 1-trimethylsilyloxy-1-cyclohexene (1a) in the presence of a catalytic amount of the acidic dihydrogen complex [RuCl(η2-H2)(dppe)2]OTf (4a) [dppe=1,2-bis(diphenylphosphino)ethane, OTf=OSO2CF3] (10 mol.%) under 1 atm of H2 in anhydrous ClCD2CD2Cl at 50 °C for 8 h afforded cyclohexanone (3a) and Me3SiH in quantitative NMR yields. Silyl enol ethers such as 1-triethylsilyloxy-1-cyclohexene (1b), 1-t-butyldimethylsilyloxy-1-cyclohexene (1c), and other trimethylsilylethers (1d, 1e, and 1f) reacted similarly with H2 to afford the corresponding ketones and trialkylsilanes. The direct proton transfer from H2 to the trimethylsilyl enol ethers (1a and 1d-1f) was confirmed by the experiments employing D2 gas, where α-monodeuterated ketones (3a′ and 3d′-3f′) were obtained in high yields. The enantioselective protonation of prochiral silyl enol ethers with 1 atm of H2 by employing [RuCl(η2-H2) ((S)-BINAP)2]OTf (4e) [BINAP=2,2′-bis (diphenylphosphino)-1,1′-binaphthyl] and [RuCl(η2-H2)((R, R)-CHIRAPHOS)2]OTf (4f) [CHIRAPHOS=2,3-bis(diphenylphosphino)butane] showed that no enantioselectivity was observed in either catalytic or stoichiometric protonation reactions under various reaction conditions. The reaction of [RuHCl(dppe)2] (5a) with one equivalent of Me3SiOTf under 1 atm of H2 produced rapidly 4a, concurrent with the formation of Me3SiH. Based on these studies, the mechanism for this novel hydrogenolysis of silyl enol ethers is proposed which involves heterolytic cleavage of the coordinated H2 on the ruthenium atom caused by the nucleophilic attack of the oxygen atom of enol ethers to give ketones and Me3SiOTf, and the subsequent reaction of the resultant complex 5a with Me3SiOTf under 1 atm of H2 to regenerate the original dihydrogen complex 4a. On the other hand, the stoichiometric reaction of a lithium enolate 6e with one equivalent of 4e at -78 °C in CH2Cl2 under 1 atm of H2 afforded 2-methyl-1-tetralone (3e) with 75% ee (S) in >95% yield, together with the formation of [RuHCl((S)-BINAP)2] (5e).
- Takei, Izuru,Nishibayashi, Yoshiaki,Ishii, Youichi,Mizobe, Yasushi,Uemura, Sakae,Hidai, Masanobu
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- Coordinatively unsaturated Ru(II) species Ru(xantsil)(CO): A new active catalyst for oligomerization/deoligomerization of HSiMe2SiMe3 [xantsil = (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilyl)]. Isolation of a stabilized form of the silyl(silylene) intermediates
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Ru(xantsil)(CO)(η6-C6H5CH3) (1) was found to be a catalyst for the oligomerization/deoligomerization of HSiMe2SiMe3 to give H(SiMe2)nMe (n = 1-8). A possible mechanism involving a silyl(silylene) intermediate was strongly supported by the isolation of its stabilized form, i.e., alkoxy-bridged bis(silylene) complex which was characterized by X-ray crystal structure analysis.
- Minglana, Jim Josephus G.,Okazaki, Masaaki,Tobita, Hiromi,Ogino, Hiroshi
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p. 406 - 407
(2007/10/03)
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- Cobalt(II) and iron(II) tris(trimethylsilyl)siloxides: synthesis, structure and reactivity
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A series of cobalt(II) and iron(II) siloxide complexes, [(Me3Si)3SiO]2M(Ln) {M=Co, Ln=none (1), (THF) (3), (THF)2 (4), (DME) (5), (MeCN)2 (6), (PhCN)2 (7), (2,2′-dipyridyl) (8), 4,4′-dipyridyl (9), (Ph3P)2 (10); M=Fe, Ln=none (2), (2,2′-dipyridyl) (11) were prepared by the reaction of metal silylamides [(Me3Si)2N]2M (M=Co, Fe) with tris(trimethylsilyl)silanol. The crystal structures of compounds 1 and 11 have been determined by the X-ray diffraction method. Complex 1 has a dimeric structure with two [(Me3Si)3SiO]2Co units bonded via the two μ2-O atoms. The central [Co(μ2-O)]2 cycle has a 'butterfly shape' being bent along the bridging oxygen atoms. The dihedral angle between the Co(1)O(4)Co(2) and Co(1)O(3)Co(2) planes is 143.1°. The μ2-bridging and terminal CoO distances are 1.945(7)-1.963(7) and 1.781(8), 1.793(7) A?, respectively. The Co?Co distance in 1 is relatively short, 2.735(2) A?. However, the high value of magnetic moment (6.0 μB) of compound 1 indicates the absence of a direct interaction between the Co atoms in 1. The molecule of 11 is monomeric. The Fe atom is bonded to 2,2′-dipyridyl and two terminal OSi(SiMe3)3 groups and has a distorted tetrahedral environment. The FeN(1), FeN(2) and FeO(1), FeO(2) distances in 11 are 2.148(1), 2.164(1) and 1.863(1), 1.900(1) A?, respectively. Addition of one equivalent of PhCCH to 7 results in the substitution of one tris(trimethylsilyl)siloxy-group with the formation of the diamagnetic dimer {(PhCN)(PhC2)CoOSi(SiMe3)3}2. Subsequent addition of PhC2H causes its oligomerisation. Complexes 1, 3 and 10 absorb carbon monoxide at ambient temperature and pressure while the others remain unreactive. Electronic spectra show fluxional behavior of complexes 1, 3 and 4 in solution.
- Chesnokova, Tatiana A,Zhezlova, Elena V,Kornev, Alexander N,Fedotova, Yana V,Zakharov, Lev N,Fukin, Georgy K,Kursky, Yurii A,Mushtina, Tatiana G,Domrachev, Georgy A
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- Novel catalytic hydrogenolysis of trimethylsilyl enol ethers by the use of an acidic ruthenium dihydrogen complex
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The heterolytic cleavage of H2 is the key to the novel catalytic hydrogenolysis of trimethylsilyl enol ethers catalyzed by [RuCl(η2- H2)(dppe)2]OTf (dppe = 1,2-bis(diphenylphosphanyl)ethane, OTf = trifluoromethanesulfonate), which results in the formation of a ketone and Me3SiH (see scheme). In addition, the stoichiometric, ruthenium-assisted protonation of a prochiral lithium enolate with H2 gave a chiral ketone with high enantioselectivity (up to 75 % ee).
- Nishibayashi, Yoshiaki,Takei, Izuru,Hidai, Masanobu
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p. 3047 - 3050
(2007/10/03)
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Bu3SnH is an effective reagent for partial conversion of Si-Cl into Si-H groups. The presented hydrogenation mechanism postulates the coordination of the catalyst (Lewis bases) or the solvent to silicon, giving an intermediate with higher coordinated silicon atom in the first step, followed by the attack of tributyltin hydride by a single electron transfer. This mechanism implies that the intermediate having a hypervalent silicon atom reacts more rapidly than the starting tetracoordinated silane.
- Paetzold,Roewer,Herzog
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p. 147 - 152
(2007/10/03)
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- Gas-phase reactions of silicon-centred intermediates with chlorofluorocarbons
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Pyrolysis of pentamethyldisilane in the presence of a CFC, dichlorodifluoromethane, efficiently replaced chlorine by hydrogen in the CFC, with concomitant formation of chlorosilanes. Although the primary intermediate in this pyrolysis is dimethylsilylene, there was strong evidence that conversions resulted from reactions of organosilyl and alkyl radicals. Experiments to confirm this conclusion are described, and mechanisms are discussed. Two independent measurements of the activation energy difference between chlorine-and fluorine-abstraction from dichlorodifluoromethane by trimethylsilyl radicals gave concordant values of 52 ± 5 kJ mol-1. The reactions described are of interest in relation to the environmental importance of dechlorinating CFCs.
- Clarke, Michael P.,Conqueror, Martin,Morgan, Geraint H.,Davidson, Iain M.T.
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p. 395 - 396
(2007/10/03)
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- Concurrent preparation of dimethylchlorosilane and triorganochlorosilane
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Dimethylchlorosilane and a triorganochlorosilane of the formula: R1 R2 R3 SiCl wherein R1, R2, and R3 are independently selected from monovalent hydrocarbon groups are concurrently prepared by reacting dimethyldichlorosilane with a SiH bond-containing silane compound of the formula: R1 R2 R3 SiH in the presence of a Lewis acid catalyst. The method is especially effective for concomitant preparation of dimethylchlorosilane and trimethylchlorosilane or t-butyldimethylchlorosilane in an inexpensive, simple, safe manner and in high yields.
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- Platinum Catalysed Regioselective ortho-Silylation of Benzylideneamines via Intramolecular C-H Activation
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The Pt-P(OCH2)3CEt complex catalyses the ortho-silylation of benzylideneamines with disilanes via intramolecular C-H activation; both mono- and bis-silylated products are obtained.
- Williams, Neil A.,Uchimaru, Yuko,Tanaka, Masato
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p. 1129 - 1130
(2007/10/02)
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- Hydrogenation of Silicium-Halogen-Compounds with Trialkylstannyl Chloride/Sodium Hydride
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Organotinchlorides of the general formula R3SnCl and R2SnCl2 (R = Me, n-Bu, Ph) can easily be converted into the corresponding hydrides R3SiH and R2SiH2 employing NaH in diethylene glycol dialkyl ethers.Using trialkyltinhydrides like Bu3SnH in combination with a catalyst (tertiary amines, N-heterocycles, phosphonium or ammonium salts), Si-Cl bonds in mono- and disilanes are hydrogenated.In the case of disilanes, Si-Si bond cleavage and concurrent hydrogenation can be afforded with strongly nucleophilic catalysts.Partial hydrogenation is also possible.The whole process can be run cyclically. - Keywords: Alkylstannylhydride; Hydrogenation; Organochlorsilane.
- Hengge, E.,Grogger, C.,Uhlig, F.,Roewer, G.,Herzog, U.,Paetzold, U.
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p. 549 - 556
(2007/10/02)
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- Peculiarities in the cleavage by methyllithium of unsymmetrical disilanes
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The title reactions did not produce the more stable silyl anions from the disilanes studied, they either occurred by attack at the more electrophilic silicon atom, or led to unexpected products.
- Hevesi,Dehon
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p. 8031 - 8032
(2007/10/02)
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- Photochemical reactions of 2-(pentamethyldisilanyl)furan and 2-(pentamethyldigermanyl)furan. Formation of a radical pair
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Photochemical reactions of 2-(pentamethyldisilanyl)furan and 2-(pentamethyldigermanyl)furan have been investigated by chemical trapping experiments and laser flash-photolysis.On irradiation, the furylated catenates of Group 14 elements undergo silicon-silicon ? bond and germanium-germanium ? bond homolysis to give a pair of silyl radicals and germyl radicals, respectively.In CCl4, these radicals are converted to the corresponding chlorides by abstraction of a chlorine atom.In nonhalogenated solvents (cyclohexane and other hydrocarbons), the silyl radical pair undergoes a disproportionation to give as main products a monosilane and a silene.The trimethylgermyl radical mainly couples at the ipso-position of the furyl group of the pairing radical to yield the corresponding diradical.This diradical undergoes elimination of a divalent species, dimethylgermylene, with concomitant formation of 2-(trimethylgermyl)furan. Key words: Photochemistry; Silanyl; Germanyl; Radical
- Mochida, Kunio,Kimijima, Kohichi,Wakasa, Masanobu,Hayashi, Hisaharu
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p. 101 - 108
(2007/10/02)
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- Excimer laser photolysis of hexamethyldisialazane
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ArF laser-induced photolysis of hexamethyldisilazane (Me3Si)2NH in the gas phase yields methane, trimethylsilane, and deposited layers of hydrolysable organosilicon oligomers.Experiments with (Me3Si)2ND reveal that early stages of the photolysis are controlled by abstraction of H or N atoms by (CH3)3Si* and CH3* radicals from H(C) and D(N) bonds and by 1,1-elimination of Me3SiD.
- Pola, Josef,Taylor, Roger
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p. 131 - 134
(2007/10/02)
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- Generation, characterization, and properties of iron-silylene and iron-silene cationic complexes in the gas phase
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Generation, characterization, and properties of iron-silylene (Fe=SiRR′) and iron-silene (Fe(CH2=SiRR′)) cations (R, R′ = H, CH3) are describe in the gas phase by using Fourier transform mass spectrometry (FTMS). Iron-(silylene/silene) cations were formed by reaction of Fe+ with appropriate silanes. Structures of these ions were probed by using both collision-activated dissociation (CAD) and ion/molecule reactions. CAD failed to yield structural information; however, reaction with isotopically labeled ethene provides compelling evidence for formation of iron-silene and iron-silylene species. There is no evidence for the interconversion of iron-silylene and iron-silene species, even upon slow collisional activation or by formation of ethene collision complexes (ca. 40 kcal/mol of excess energy). This indicates that there is a prohibitive barrier for iron mediated interconversion of silene and silylenes. Reactions of iron-silylene and iron-silene species with water and benzene are described. The nature of the bonding is presented and bond dissociation limits are obtained.
- Jacobson,Bakbtiar
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p. 10830 - 10844
(2007/10/02)
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- Investigation of the Chemical Vapor Deposition of Silicon Carbide from Tetramethylsilane by in Situ Temperature and Gas Composition Measurements
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The chemical vapor deposition (CVD) of silicon carbide (SiC) from tetramethylsilane Si(CH3)4(TMS) on a graphite susceptor at 1200-1500 K is studied in a low pressure (ca. 100 Pa) cold-wall reactor under laminar flow conditions.In addition to material characterizations (electron microscopy and chemical analysis), the gas-phase temperature distribution and composition are investigated by combining several in situ and ex situ diagnostics.Coherent anti-Stokes Raman spectrosopy (CARS) on TMS and H2 (produced from TMS decomposition) in the hot zone of the reactor gives the rotational temperature distribution of the molecules and their concentrations.Within a few mean free paths from the surface, the H2 gas temperature is lower than the surface temperature.This is due to a nonunity accommodation coefficient α of H2 on SiC.A simple analytical model yields α = 0.05 for H2 on SiC.Using gas transport coefficients and the experimental value of α for H2, a two-dimensional numerical code is used to compute the gas flow and temperature profiles in the reactor.The increase of the H2 concentration and the decrease of TMS concentration close to the surface reveals that gas-phase pyrolysis of TMS occurs within a few millimeters from the hot surface.The gas composition at the outlet of the reactor is analyzed by mass spectrometry and IR absorption spectroscopy.The global gas conversion and material balance between deposited SiC, powders, and exhaust gases is obtained.Si atoms of TMS molecules are mostly converted into solid SiC and powders.In the gaseous products a small fraction of trimethylsilane SiH(CH3)3 is detected.Other gases in decreasing order of importance are H2, CH4, C2H4, and C2H2.These results are compared with predictions of some thermodynamic models and chemical mechanisms reported in the literature.
- Herlin, Nathalie,Lefebvre, Michel,Pealat, Michel,Perrin, Jerome
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p. 7063 - 7072
(2007/10/02)
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