- Hydride transfer reactions between penta- and tetra-coordinate silicon derivatives
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K has been found to reduce Ph3SiF and Ph3SiCl and to induce H/D exchange with Ph3SiD and Ph2SiD2.The mechanism of this exchange seems to be a one-step concerted mechanism through an intermediate with bridging hydrogen and deuterium atoms.
- Corriu, R.J.P.,Guerin, C.,Henner, B.J.L.,Wang, Q.
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Read Online
- The Role of (tBuPOCOP)Ir(I) and Iridium(III) Pincer Complexes in the Catalytic Hydrogenolysis of Silyl Triflates into Hydrosilanes
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Hydrosilanes are convenient reductants for a large variety of organic substrates, but they are produced via energy-intensive processes. These limitations call for the development of general catalytic processes able to transform Si-O into Si-H bonds. We report here the catalytic hydrogenolysis of R3SiOTf (R = Me, Et, and Ph) species in the presence of a base (e.g., NEt3), by the hydride complexes [(tBuPOCOP)IrH(X)] (X = H and OTf; (tBuPOCOP = [C6H3-2,6(OPtBu)2]. Syntheses and crystal structures of new iridium(I) and iridium(III) complexes are presented as well as their role in the R3SiOTf to R3SiH transformation. The mechanisms of these reactions have been examined by DFT studies, revealing that the active species involved in the reduction of the Si-OTf vs Si-Cl bond are different. The rate-determining transition state is a base-assisted splitting of H2, forming an iridium(III) dihydride species.
- Berthet, Jean-Claude,Cantat, Thibault,Durin, Gabriel,Nicolas, Emmanuel,Thuéry, Pierre
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supporting information
(2021/12/09)
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- Continuous-flow Si-H functionalizations of hydrosilanesviasequential organolithium reactions catalyzed by potassiumtert-butoxide
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We herein report an atom-economic flow approach to the selective and sequential mono-, di-, and tri-functionalizations of unactivated hydrosilanesviaserial organolithium reactions catalyzed by earth-abundant metal compounds. Based on the screening of various additives, we found that catalytic potassiumtert-butoxide (t-BuOK) facilitates the rapid reaction of organolithiums with hydrosilanes. Using a flow microreactor system, various organolithiums bearing functional groups were efficiently generatedin situunder mild conditions and consecutively reacted with hydrosilanes in the presence oft-BuOK within 1 min. We also successfully conducted the di-funtionalizations of dihydrosilane by sequential organolithium reactions, extending to a gram-scale-synthesis. Finally, the combinatorial functionalizations of trihydrosilane were achieved to give every conceivable combination of tetrasubstituted organosilane libraries based on a precise reaction control using an integrated one-flow system.
- Lee, Hyune-Jea,Kwak, Changmo,Kim, Dong-Pyo,Kim, Heejin
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supporting information
p. 1193 - 1199
(2021/02/26)
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- Organocalcium Complex-Catalyzed Selective Redistribution of ArSiH3or Ar(alkyl)SiH2to Ar3SiH or Ar2(alkyl)SiH
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Calcium is an abundant, biocompatible, and environmentally friendly element. The use of organocalcium complexes as catalysts in organic synthesis has had some breakthroughs recently, but the reported reaction types remain limited. On the other hand, hydrosilanes are highly important reagents in organic and polymer syntheses, and redistribution of hydrosilanes through C-Si and Si-H bond cleavage and reformation provides a straightforward strategy to diversify the scope of such compounds. Herein, we report the synthesis and structural characterization of two calcium alkyl complexes supported by β-diketiminato-based tetradentate ligands. These two calcium alkyl complexes react with PhSiH3 to generate calcium hydrido complexes, and the stability of the hydrido complexes depends on the supporting ligands. One calcium alkyl complex efficiently catalyzes the selective redistribution of ArSiH3 or Ar(alkyl)SiH2 to Ar3SiH and SiH4 or Ar2(alkyl)SiH and alkylSiH3, respectively. More significantly, this calcium alkyl complex also catalyzes the cross-coupling between the electron-withdrawing substituted Ar(R)SiH2 and the electron-donating substituted Ar′(R)SiH2, producing ArAr′(alkyl)SiH in good yields. The synthesized ArAr′(alkyl)SiH can be readily transferred to other organosilicon compounds such as ArAr′(alkyl)SiX (where X = OH, OEt, NEt2, and CH2SiMe3). DFT investigations are carried out to shed light on the mechanistic aspects of the redistribution of Ph(Me)SiH2 to Ph2(Me)SiH and reveal the low activation barriers (17-19 kcal/mol) in the catalytic reaction.
- Li, Tao,McCabe, Karl N.,Maron, Laurent,Leng, Xuebing,Chen, Yaofeng
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p. 6348 - 6356
(2021/05/29)
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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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- Highly selective redistribution of primary arylsilanes to secondary arylsilanes catalyzed by Ln(CH2C6H4NMe2-: O)3@SBA-15
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Rare-earth metal tris(aminobenzyl) complexes Ln(CH2C6H4NMe2-o)3 (Ln = La, Y) were grafted onto the dehydroxylated periodic mesoporous silica support SBA-15 to generate the organometallic-inorganic hybrid materials Ln(CH2C6H4NMe2-o)3@SBA-15 (Ln = La (2a), Y (2b)), which demonstrated extremely high selectivity (>99%) in catalyzing the redistribution of primary arylsilanes to secondary arylsilanes without the requisition of strict control of the reaction conditions. The hybrid materials still showed a perfect selectivity and activity after three catalytic cycles.
- Guo, Chenjun,Li, Min,Chen, Jue,Luo, Yunjie
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supporting information
p. 117 - 120
(2019/12/25)
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- Synthesis of hydrosilanes: Via Lewis-base-catalysed reduction of alkoxy silanes with NaBH4
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Hydrosilanes were synthesized by reduction of alkoxy silanes with BH3 in the presence of hexamethylphosphoric triamide (HMPA) as a Lewis-base catalyst. The reaction was also achieved using an inexpensive and easily handled hydride source NaBH4, which reacted with EtBr as a sacrificial reagent to form BH3in situ.
- Aoyagi, Keiya,Ohmori, Yu,Inomata, Koya,Matsumoto, Kazuhiro,Shimada, Shigeru,Sato, Kazuhiko,Nakajima, Yumiko
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supporting information
p. 5859 - 5862
(2019/05/27)
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- Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes
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The ligand-redistribution reactions of aryl- and alkoxy-hydrosilanes can potentially cause the formation of gaseous hydrosilanes, which are flammable and pyrophoric. The ability of generic nucleophiles to initiate the ligand-redistribution reaction of commonly used hydrosilane reagents was investigated, alongside methods to hinder and halt the formation of hazardous hydrosilanes. Our results show that the ligand-redistribution reaction can be completely inhibited by common electrophiles and first-row transition metal pre-catalysts.
- Docherty, Jamie H.,Dominey, Andrew P.,Thomas, Stephen P.
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p. 3330 - 3335
(2019/05/10)
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- Electrochemical properties of arylsilanes
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In the past, the electrochemical properties of organosilicon compounds were investigated for both fundamental reasons and synthesis purposes. Little is, however, known about the electrochemical behaviour of hydrogen-bearing arylsilanes. Here, we throw light on the electrochemical properties of 11 arylsilanes compounds, 2 of them synthesized for the first time. The oxidation potentials are found to depend on both the nature and number of the aryl groups. Based on these findings it was possible to establish some variation trends that match the expected structure–property correlations. Furthermore, we present first insights into the electrochemical reaction kinetics behind and identify several soluble electrochemical oxidation products.
- Biedermann, Judith,Wilkening, H. Martin R.,Uhlig, Frank,Hanzu, Ilie
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- Distinct Catalytic Performance of Cobalt(I)- N -Heterocyclic Carbene Complexes in Promoting the Reaction of Alkene with Diphenylsilane: Selective 2,1-Hydrosilylation, 1,2-Hydrosilylation, and Hydrogenation of Alkene
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Selectivity control on the reaction of alkene with hydrosilane is a challenging task in the development of non-precious-metal-based hydrosilylation catalysts. While the traditional way of selectivity control relies on the use of different ligand type and/or different metals, we report herein that cobalt(I) complexes bearing different N-heterocyclic carbene ligands (NHCs) exhibit distinct selectivity in catalyzing the reaction of alkene with Ph2SiH2. [(IAd)(PPh3)CoCl] (IAd = 1,3-diadamantylimidazol-2-ylidene) is an efficient catalyst for anti-Markovnikov hydrosilylation of monosubstituted alkenes. [(IMes)2CoCl] (IMes = 1,3-dimesitylimidazol-2-ylidene) shows Markovnikov-addition selectivity in promoting the hydrosilylation of aryl-substituted alkenes. [(IMe2Me2)4Co][BPh4] (IMe2Me2 = 1,3-dimethyl-4,5-dimethylimidazol-2-ylidene) can catalyze hydrogenation of alkenes with Ph2SiH2 as the terminal hydrogen source. Mechanistic studies in combination with the knowledge on the steric nature of cobalt-NHC species suggest that (NHC)cobalt(I) silyl species and bis(NHC)cobalt(I) hydride species are the probable key intermediates for these hydrosilylation and hydrogenation reactions, respectively. The different steric nature of IAd versus IMes and the potential of IMes incurring π···π interaction with aryl-substituted alkenes are thought to be the causes of the observed 1,2- and 2,1-addition selectivity.
- Gao, Yafei,Wang, Lijun,Deng, Liang
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p. 9637 - 9646
(2018/10/02)
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- A silicon hydrogenation for the preparation of compounds
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The invention relates to a method for preparing silicon hydrides. Under the protection of Ar gas, THF and/or HMPA are/is used as a solvent, chlorosilane or derivatives of chlorosilane reacts with magnesium metal to prepare the silicon hydrides. The method has the characteristics of being cheap in raw materials, easy to get the raw materials, easy to operate, mild in reaction conditions and low in cost.
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Paragraph 0034; 0035; 0036; 0037
(2018/03/09)
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- METHOD FOR PRODUCING SILICON HYDRIDE COMPOUND
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PROBLEM TO BE SOLVED: To provide a method for producing a silicon hydride compound by converting a silicon-halogen bond to a silicon-hydrogen bond with a boron hydride, wherein the method allows the reaction to proceed quickly and can be applied to a variety of substrates. SOLUTION: A method for producing a silicon hydride compound includes the step of converting a silicon-halogen bond to a silicon-hydrogen bond with a boron hydride, in the presence of an organic solvent containing nitrogen. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0039; 0040
(2017/11/01)
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- A method to derivatize surface silanol groups to Si-alkyl groups in carbon-doped silicon oxides
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A carbon-doped silicon oxide (CDO) finds use as a material with a low dielectric constant (k) for copper interconnects in multilayered integrated circuits (ICs). Hydrophilic silanol groups (Si-OH) on its surface, however, can attract moisture, thereby causing an undesirable increase in the dielectric constant. Modification of the exposed hydrophilic surface to a hydrophobic functional group provides one solution to this problem. We report here a strategy for converting surface Si-OH to hydrophobic silicon hydride (Si-H) without affecting the internal oxide network in CDO. The approach involves esterification of the exposed silanol to its triflate (silyltrifluoromethanesulfonate, Si-O-Tf), followed by reduction to Si-H with diisobutylaluminum hydride. Si-H is further modified by a photochemical reaction with an alkene (1-octadecene) to yield Si-R (R = -C18H37) to provide a more moisture resistant, and less polar Si-C as opposed to the Si-O backbone. Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectrometry (XPS), and measurements of the contact angle with water substantiated the successful conversion. The reaction scheme is versatile, transforming silanol groups to silicon hydride in widely varying chemical sites, from small molecules to the surfaces of silica gels, SiOx and CDO wafers. A comparison with the films (self-assembled monolayers) derivatized with the octadecyltrichlorosilane indicated that the new method leads to a thicker (≈5 nm) but more loosely packed hydrocarbon film with slightly lower contact angles.
- Darmakkolla, Srikar Rao,Tran, Hoang,Gupta, Atul,Rananavare, Shankar B.
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p. 93219 - 93230
(2016/10/11)
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- Bis(acetylacetonato)Ni(II)/NaBHEt3-catalyzed hydrosilylation of 1,3-dienes, alkenes and alkynes
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The utility of commercially available Ni(II) salts, Ni(acac)2 (acac = acetylacetonato) (1a) and its derivatives bis(hexafluoroacetylacetonato)nickel(II) (1b) and bis(2,2,6,6-tetramethyl-3,5-heptanedionato)nickel(II) (1c) as versatile hydrosilylation catalyst precursors is described. Complexes 1a-c catalyze 1,4-selective hydrosilylation of 1,3-dienes in the presence of NaBHEt3 at ambient temperature. The reactions exhibit good regioselectivity to give the branched isomers as major products. The catalytic system also catalyzes hydrosilylation of alkenes including industriary important siloxy-, amino-, and epoxy-substituted ones as well as both terminal and internal alkynes.
- Srinivas, Venu,Nakajima, Yumiko,Ando, Wataru,Sato, Kazuhiko,Shimada, Shigeru
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- Activation of Si-H bonds across the nickel carbene bond in electron rich nickel PCcarbeneP pincer complexes
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Silicon-hydrogen bonds are shown to add to a nickel carbon double bond to yield nickel α-silylalkyl hydrido complexes. Kinetic and isotope labeling studies suggest that a concerted 4-centred addition across the NiC bond is operative rather than a mechanism involving Si-H oxidative addition. This constitutes an example of Si-H bond activation via ligand cooperativity.
- LaPierre, Etienne A.,Piers, Warren E.,Spasyuk, Denis M.,Bi, David W.
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p. 1361 - 1364
(2016/01/25)
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- Hydrogenation of chlorosilanes by NaBH4
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Hydrogenation of chlorosilane was achieved in acetonitrile using NaBH4, a safe and easy-to-handle reagent. This reaction converted Si-Cl portion(s) in organosilanes into Si-H portion(s) without hydrogenation of cyano, chloro, and aldehyde groups on an alkyl substituent of the Si reagents. In addition, the Si-Cl/Si-H exchange reaction was applicable to dichlorodisilane without Si-Si bond cleavage.
- Ito, Masaki,Itazaki, Masumi,Abe, Takashi,Nakazawa, Hiroshi
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p. 1434 - 1436
(2016/12/03)
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- Rearrangement Reactions of Tritylcarbenes: Surprising Ring Expansion and Computational Investigation
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As a rule, acetylides and sulfonyl azides do not undergo electrophilic azide transfer because 1,2,3-triazoles are usually formed. We show now that treatment of tritylethyne with butyllithium followed by exposure to 2,4,6-triisopropylbenzenesulfonyl azide leads to products that are easily explained through the generation of short-lived tritylethynyl azide and its secondary product cyanotritylcarbene. Furthermore, it is demonstrated that tritylcarbenes generally do not produce triphenylethenes exclusively, as was stated in the literature. Instead, these carbenes always yielded also (diphenylmethylidene)cycloheptatrienes (heptafulvenes) as side products. This result is supported by static DFT, coupled cluster, and ab initio molecular dynamics calculations. From these investigations, the fused bicyclobutane intermediate was found to be essential for heptafulvene formation. Although the bicyclobutane is also capable of rearranging to the triphenylethene product, only the heptafulvene pathway is reasonable from the energetics. The ethene is formed straight from cyanotritylcarbene.
- Banert, Klaus,Hagedorn, Manfred,Pester, Tom,Siebert, Nicole,Staude, Cornelius,Tchernook, Ivan,Rathmann, Katharina,Holl?czki, Oldamur,Friedrich, Joachim
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p. 14911 - 14923
(2015/10/19)
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- Iridium Pincer Catalysts for Silane Dehydrocoupling: Ligand Effects on Selectivity and Activity
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Catalytic reactions of bisphosphinite pincer-ligated iridium compounds p-XR(POCOP)IrHCl (POCOP) [2,6-(R2PO)2C6H3, R = iPr, X = H (1); R = tBu, X = COOMe (2); = H (3); = NMe2 (4)] with primary and secondary silanes have been performed. Complex 1 is primarily a silane redistribution precatalyst, but dehydrocoupling catalysis is observed for sterically demanding silane substrates or with aggressive removal of H2. The bulkier compounds (2-4) are silane dehydrocoupling precatalysts that also undergo competitive redistribution with less hindered substrates. Products generated from reactions utilizing 2-4 include low molecular weight oligosilanes with varying degrees of redistribution present or disilanes when employing more sterically demanding silane substrates. Selectivity for redistribution versus dehydrocoupling depends on the steric and electronic environment of the metal but can also be affected by reaction conditions. (Chemical Equation Presented).
- Mucha, Neil T.,Waterman, Rory
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supporting information
p. 3865 - 3872
(2015/08/19)
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- Hydrosilylation catalysis by an earth alkaline metal silyl: Synthesis, characterization, and reactivity of bis(triphenylsilyl)calcium
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Bis(triphenylsilyl)calcium [Ca(SiPh3)2(thf)] obtained in high yield as a crystalline ether adduct catalyzes the hydrosilylation of activated C-C double bonds efficiently and regioselectively. The Royal Society of Chemistry 2014.
- Leich, Valeri,Spaniol, Thomas P.,Maron, Laurent,Okuda, Jun
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supporting information
p. 2311 - 2314
(2014/03/21)
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- Structural and mechanistic investigation of a cationic hydrogen-substituted ruthenium silylene catalyst for alkene hydrosilation
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The cationic ruthenium silylene complex [Cp*(iPr 3P)Ru(H)2(SiHMes)][CB11H6Br 6], a catalyst for olefin hydrosilations with primary silanes, was isolated and characterized by X-ray crystallography. Relatively strong interactions between the silylene Si atom and Ru-H hydride ligands appear to reflect a highly electrophilic silicon center. The mechanism of olefin hydrosilation was examined by kinetics measurements and other experiments to provide the first experimentally determined mechanism for the catalytic cycle. This mechanism involves a fast, initial addition of the Si-H bond of the silylene complex to the olefin. Subsequent elimination of the product silane produces an unsaturated intermediate, which can be reversibly trapped by olefin or intercepted by the silane substrate. The latter reaction pathway involves activation of the reactant silane by Si-H oxidative addition and α-hydrogen migration to regenerate the key silylene intermediate.
- Fasulo, Meg E.,Lipke, Mark C.,Tilley, T. Don
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p. 3882 - 3887
(2013/09/23)
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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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- General and practical one-pot synthesis of dihydrobenzosiloles from styrenes
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A one-pot synthesis of dihydrobenzosiloles from styrenes has been developed. The reaction involves the nickel-catalyzed hydrosilylation of styrene with diphenylsilane, followed by the iridium-catalyzed dehydrogenative cyclization. This method is efficient for both electron-rich and -deficient styrenes and exhibits good functional group tolerance, as well as excellent regioselectivity. The forming dihydrobenzosiloles can be efficiently converted into valuable benzosiloles or 2-hydroxyphenethyl alcohols.
- Kuznetsov, Alexey,Gevorgyan, Vladimir
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supporting information; experimental part
p. 914 - 917
(2012/05/05)
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- Catalytic and stoichiometric reactivity of β-silylamido agostic complex of Mo: Intermediacy of a silanimine complex and applications to multicomponent coupling
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The reaction of complex (ArN=)2Mo(PMe3)3 (Ar = 2,6-diisopropylphenyl) with PhSiH3 gives the β-agostic NSi-H ...Msilyamido complex (ArNd)Mo(SiH2Ph) (PMe3)- (η3-ArN-SiHPh-H) (3) as the first product. 3 decomposes in the mother liquor to a mixture of hydride compounds, including complex {η3-SiH(Ph)-N(Ar)-SiHPh-H ... }MoH 3(PMe3)3 characterized by NMR. Compound 3 was obtained on preparative scale by reacting (ArN=)2Mo(PMe 3)3 with 2 equiv of PhSiH3 under N2 purging and characterized by multinuclear NMR, IR, and X-ray diffraction. Analogous reaction of (Ar′N=)2Mo(PMe3)3 (Ar′ = 2,6-dimethylphenyl) with PhSiH3 affords the nonagostic silylamido derivative (Ar′N=)Mo(SiH2Ph)(PMe3) 2(NAr′{SiH2Ph}) (5) as the first product. 5 decomposes in the mother liquor to a mixture of {η3-PhHSi- N(Ar′)-SiHPh-H ... }MoH3(PMe3)3, (Ar′N=)Mo(H)2(PMe3)2(η2- Ar′N=SiHPh), and other hydride species. Catalytic and stoichiometric reactivity of 3 was studied. Complex 3 undergoes exchange with its minor diastereomer 3′ by an agostic bond-opening/closing mechanism. It also exchanges the classical silyl group with free silane by an associative mechanism which most likely includes dissociation of the Si-H agostic bond followed by the rate-determining silane σ-bond metathesis. However, labeling experiments suggest the possibility of an alternative (minor) pathway in this exchange including a silanimine intermediate. 3 was found to catalyze dehydrogenative coupling of silane, hydrosilylation of carbonyls and nitriles, and dehydrogenative silylation of alcohols and amines. Stoichiometric reactions of 3 with nitriles proceed via intermediate formation of η2- adducts (ArN=)Mo(PMe3)(η2-ArN=SiHPh) (η2-NtCR), followed by an unusual Si-N coupling to give (ArN=)Mo(PMe3)(κ2-NAr-SiHPh-C(R)=N-). Reactions of 3 with carbonyls lead to η2-carbonyl adducts (ArN=) 2Mo(OdCRR0)(PMe3) which were independently prepared by reactions of (ArN=)2Mo(PMe3)3 with the corresponding carbonyl OdCRR′. In the case of reaction with benzaldehyde, the silanimine adduct (ArN=)Mo(PMe3)(η2-ArN=SiHPh)- (η2-O=CHPh) was observed by NMR. Reactions of complex 3 with olefins lead to products of Siag-C coupling, (ArN=)Mo(Et)(PMe 3)(η3-NAr-SiHPh-CH=CH2) (17) and (ArN=)Mo(H)(PMe3)(η3-NAr-SiHPh-CH=CHPh), for ethylene and styrene, respectively. The hydride complex (ArN=)Mo(H)(PMe 3)(η3-NAr-SiHPh-CH=CH2) was obtained from 17 by hydrogenation and reaction with PhSiH3. Mechanistic studies of the latter process revealed an unusual dependence of the rate constant on phosphine concentration, which was explained by competition of two reaction pathways. Reaction of 17 with PhSiH3 in the presence of BPh3 leads to agostic complex (ArN=)Mo(SiH2Ph)(η3-NAr-Si(Et)Ph-H) (η2-CH2=CH2) (24) having the Et substituent at the agostic silicon. Mechanistic studies show that the Et group stems from hydrogenation of the vinyl substituent by silane. Reaction of 24 with PMe 3 gives the agostic complex (ArN=)Mo(SiH2Ph)(PMe 3)(η3-NAr-Si(Et)Ph-H), which slowly reacts with PhSiH3 to furnish silylamide 3 and the hydrosilylation product PhEtSiH2. A mechanism involving silane attack on the imido ligand was proposed to explain this transformation.
- Khalimon, Andrey Y.,Simionescu, Razvan,Nikonov, Georgii I.
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experimental part
p. 7033 - 7053
(2011/06/25)
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- Reactions of (Et2NCH2CH2NEt 2)·H2SiCl2 with selected diorganometallic reagents of magnesium and lithium
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Addition of the THF-insoluble di-Grignard reagent from 2,2′-dibromo- 4,4′-tert-butylbiphenyl (1) to a solution of [(teeda)·H 2SiCl2] in CH2Cl2/THF produced 2,7-di-tert-butyl-9H-9-silafluorene (3) in isolated, recrystallized yields of 2O, when reacted with [(teeda)·H2SiCl2] in CH2Cl 2/Et2O, gave similar yields of 5,10-dihydro-2,5,8- trimethylphenazasiline (4). In the absence of CH2Cl2 the major product produced from 1 was the spirocycle 2,2′,7,7′-tetra- tert-butyl-9,9′-spirobi[9H-9-silafluorene] both in a solvent-free form (5′) and as an ethanol solvate (5), both of which were crystallographically characterized. The spirocycle 2,2′,5,5′,8, 8′-hexamethyl-5,10-dihydro-10,10-spirobiphenazasiline (6) was formed from the reaction of the dilithio reagent of 2 in the absence of CH 2Cl2.
- Corey, Joyce Y.,Trankler, Kevin A.,Braddock-Wilking, Janet,Rath, Nigam P.
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experimental part
p. 5708 - 5713
(2011/02/16)
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- Silane-controlled diastereoselectivity in the tris(pentafluorophenyl) borane-catalyzed reduction of α-diketones to silyl-protected 1,2-diols
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(Figure presented) B(C6F5)3-catalyzed bis(hydrosilylation) of α-diketones can give high diastereomeric excess of either meso/anti (small silanes and disilane reagents) or dl/syn (bulky silanes) silyl-protected 1,2-diols. This easily tuned diastereoselectivity is rationalized based on the classic Felkin-Anh model applied to a mechanism relying on Si-H abstraction by the electrophilic borane reagent.
- Skjel, Miranda K.,Houghton, Adrian Y.,Kirby, Andrea E.,Harrison, Daniel J.,McDonald, Robert,Rosenberg, Lisa
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supporting information; experimental part
p. 376 - 379
(2010/03/25)
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- Silyl-directed, iridium-catalyzed ortho-borylation of arenes. A one-pot ortho-borylation of phenols, arylamines, and alkylarenes
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The regioselectivity of the borylation of arenes catalyzed by the combination of 4,4′-di-tert-butylbipyridine (dtbpy) and [Ir(cod)Cl]2 has typically been governed by steric effects. We describe a strategy that makes use of a new substituent for ortho-functionalization to overcome this bias. We show that arenes containing hydrosilyl substituents on an atom attached to the arene ring undergo borylation at the position ortho to the hydrosilyl group. Using iridium-catalyzed formation of silyl ethers and silylamines from silanes and either phenols or arylamines, we have developed the ortho-borylation into a one-pot conversion of free phenols and monoprotected anilines into hydroxy- and amino-substituted organoboron derivatives. Copyright
- Boebel, Timothy A.,Hartwig, John F.
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p. 7534 - 7535
(2008/12/22)
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- Sequential C-F activation and borylation of fluoropyridines via intermediate Rh(i) fluoropyridyl complexes: A multinuclear NMR investigation
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The C-F bond activation of fluoropyridines by [Rh(SiPh3) (PMe3)3] afforded Rh(i) fluoropyridyl complexes of the type [Rh(ArF)(PMe3)3] with concomitant formation of fluorotriphenylsilane; subsequent treatment with bis-catecholatodiboron yielded fac-[Rh(Bcat)3(PMe3) 3] and the free fluoropyridyl boronate esters (ArFBcat). The Royal Society of Chemistry.
- Lindup, Richard J.,Marder, Todd B.,Perutz, Robin N.,Whitwood, Adrian C.
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p. 3664 - 3666
(2008/03/14)
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- Efficient preparation of monohydrosilanes using palladium-catalyzed Si-C bond formation
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(Chemical Equation Presented) The arylation of dihydrosilanes with aryl iodides or heteroaryl iodides in the presence of a palladium catalyst provides the corresponding monohydrosilanes in good to high yield. Moderate to good yields are obtained even in the presence of a variety of reactive functional groups, such as -NH2, -OH, or -CN, without their protection.
- Yamanoi, Yoshinori,Taira, Takafumi,Sato, Jun-Ichi,Nakamula, Ikuse,Nishihara, Hiroshi
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p. 4543 - 4546
(2008/03/13)
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- Palladium(II) catalysed silicon-oxygen bond formation versus rearrangement reactions
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Phenylsilane and diphenylsilane undergoes rearrangement reactions by palladium catalysts such as Pd(TMEDA)Cl2, Pd(TEEDA)Cl2, [Pd(PPh3)]2Cl2 (where TMEDA = tetramethylethylenediamine, TEEDA = tetraethylethylenediamine) at room temperature. However, the reductive Si-O bond forming reaction can be performed on hydrosilanes through competitive paths. The reactions of phenylsilane and quinonic compounds are catlaysed by Pd(TMEDA)Cl2 (such as 1,4-benzoquinone, 1,4-napthoquinone) to give siloxanes, backbone of these siloxanes which contains rearranged phenylsilane units. The thin films of such oligomers has plot of resistance vs temperature profile resembling semiconductor.
- Purkayastha,Baruah
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- Disproportionation reactions of organohydrosilanes in the presence of base catalysts
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Alkoxides, alkyl compounds, amides and hydrides of alkali metals (M) and barium, such as MOR, Ba(OR)2, n-BuM, PhM, MN(SiMe3)2 and MAlH4 showed high catalytic activities versus the disproportionation reactions of PhSiH3 to produce SiH4, Ph2SiH2 and Ph3SiH. A good correlation between the catalyst basicities and the catalytic activities was observed, and a reaction mechanism involving the metal hydride and alkyl metal was proposed. A considerable amount of SiH4 was produced in the reduction of PhSiCl3 with LiAlH4 when over three moles of LiAlH4 was used.
- Itoh, Masayoshi,Inoue, Koji,Ishikawa, Jun-Ichi,Iwata, Kenji
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- Selective synthesis of monohydrosilanes by the reactions of organoytterbium iodides with dihydrosilanes
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Monohydrosilanes can be prepared selectively in high yields from the reaction of various aryl and alkyl iodides with ytterbium metal followed by the reaction with dihydrosilanes.
- Jin, Wu-Song,Makioka, Yoshikazu,Kitamura, Tsugio,Fujiwara, Yuzo
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p. 955 - 956
(2007/10/03)
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- Synthesis and characterization of the first Niobocene germyl complexes and reactivity of triphenylsilyl-, triphenylgermyl-, and triphenylstannylniobocene derivatives. X-ray molecular structures of d0 Nb(η5-C5H4SiMe3) 2(H)2(EPh3) (E = Ge, Sn)
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Thermal treatment of Nb(η5-C5H4SiMe3) 2(H)3 (1) with the appropriate organogermanium hydrides (HGeR3) and HSnPh3 gives the corresponding niobocene germyl hydrides Nb(η5-C5H4SiMe3) 2(H)2(GeR3), GeR3=GePh3 (2), GePh2H (3), GeEt3 (4), Ge(C6H13)3 (5), GeiAm3 (iAm = CH2CH2CH(CH3)2) (6), Ge(C6H13)2Cl (7), GeiAm2Cl (8), Ge(C6H13)2H (9), GeiAm2H (10), and Nb(η5-C5H4SiMe3) 2(H)2(SnPh3) (11) in good yields. Spectroscopic data indicate the presence of only one of the two possible structural isomers in which the germyl or stannyl group is in the equatorial plane with a symmetrical structure. Reactivity studies on the series Nb(η5-C5H4SiMe3) 2(H)2(ER3), E = Si (12), Ge (2), Sn (11), were carried out. 12 reacts with H2 to give 1, but 2 and 11 were unreactive toward this reagent. Furthermore, a similar behavior was observed with CO and CN(2,6-Me2C6H3). Thus, 12 reacts with these reagents to give rise, after elimination of HSiPh3, to Nb(η5-C5H4SiMe3) 2(H)(CO) and Nb(η5-C5H4SiMe3) 2-(H)(CN(2,6-Me2C6H3)), respectively, while 2 and 11 do not react. Reactions of 12 with HGePh3 and HSnPh3 and of 2 with HSnPh3 gave σ-bond metathesis products, but no reactions were observed between 2 and HSiPh3 or between 11 and HSiPh3 or 11 and HGePh3. The kinetics of these processes have been studied by 1H NMR spectroscopy and indicated the following reactivity trends Nb-SiPh3 > Nb-GePh3 > Nb-SnPh3 for the different processes considered. The X-ray molecular structures of 2 and 11 were established by diffraction studies The two isostructural complexes show a bent-sandwich coordination with the two hydrides flanking either side of the Nb-Ge and Nb-Sn bonds (2.710(1), 2.830(1) A? in 2 and 11, respectively).
- Antin?olo,Carrillo-Hermosilla,Castel,Fajardo,Ferna?ndez-Baeza,Lanfranchi,Otero,Pellinghelli,Rima,Satge?,Villasen?or
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p. 1523 - 1529
(2008/10/08)
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- Samarium-mediated redistribution of silanes and formation of trinuclear samarium-silicon clusters
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The samarium complex Cp*2SmCH(SiMe3)2 (Cp* = C5Me5), unlike the related alkyls Cp*2LnCH(SiMe3)2 (Ln = Y, Nd), mediates the redistribution of hydrosilanes while being converted to trisamarium clusters, including Cp*6Sm3(μ-SiH3)(μ 3-η1,η1,η2-SiH 2-SiH2).
- Radu, Nora S.,Hollander, Frederick J.,Tilley, T. Don,Rheingold, Arnold L.
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p. 2459 - 2460
(2007/10/03)
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- A systematic analysis of the structure-reactivity trends for some 'cation-like' early transition metal catalysts for dehydropolymerization of silanes
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The use of 'cation-like' metallocene combination catalysts (Cp′2MCl2-2BuLi-B(C6F5)3; Cp′ = η5-cyclopentadienyl, or substituted η5-cyclopentadienyl; M = Ti, Zr, Hf, U) for dehydropolymerization of silanes significantly improves the polymer molecular weight. For example, under the same conditions a Cp(C5Me5)ZrCl2-2BuLi catalyst gives Mn = 1890, while a Cp(C5Me5)ZrCl2-2BuLi-B(C6F5)3 gives Mn = 7270. The influence of various factors (steric and electronic effects of the cyclopentadienyl ligands, the nature of the metal, temperature, solvent, concentration and structure of silane) on the build-up of polysilane chains are systematically analyzed.
- Dioumaev, Vladimir K.,Harrod, John F.
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p. 133 - 143
(2007/10/03)
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- Access to Stabilized Silyl Anions by Electroreduction of Chlorosilanes
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Using the sacrificial anode technique, the electroreduction of arylchlorosilanes into the corresponding arylhydrosilanes occurs via a silylaluminium intermediate characterized for the first time in such reactions.
- Duprat, C.,Biran, C.,Bordeau, M.,Constantieux, T.,Gerval, P.,Dunogues, J.
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p. 2107 - 2108
(2007/10/02)
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- Synthesis, characterization, and reactivity of triphenylsilyl, triphenylgermyl, and triphenylstannyl derivatives of zirconium and hafnium
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The crystalline lithium silyl compound (THF)3LiSiPh3 (1) was isolated from the reaction of Ph3SiSiPh3 with lithium in tetrahydrofuran. This compound and tetrahydrofuran solutions of LiEPh3 (E = Ge, Sn
- Woo, Hee-Gweon,Freeman, William P.,Don Tilley
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p. 2198 - 2205
(2008/10/08)
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- Convenient route to di- and triorganosilyl ethyl ethers and the corresponding di- and triorganosilanes
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Tetraethoxysilane was treated with alkyl- and aryllithium reagents for the reparation of organosilyl ethyl ethers of the type R3SiOEt, R2R'SiOEt, and R2Si(OEt)2, that can be reduced to the organosilanes R3SiH, R2R'SiH, and R2SiH2, respectively, Compounds of the type RR'R''SiOEt cannot be cleanly formed.The reduction procedure involves treatment of the silyl alkoxy ethers with diisobutylaluminium hydride (DIBALH) and hydrolysis of the remaining alkylaluminium compounds with Na2SO4*10H2O.This hydrolysis provides a convenient method for the isolation of R3SiH, R2R'SiH, and R2SiH2 compounds without hydrolysis of the Si-H moiety that often occurs in standard aqueous work-up procedures of unhindered silanes.
- Tour, James M.,John, Jens A.,Stephens, Eric B.
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p. 301 - 310
(2007/10/02)
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- Amino acid protecting groups
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This invention relates to compounds of the formula a compound of the formula STR1 wherein X is O, CR7 R8, S or NR9 wherein R7 and R8 are independently hydrogen, or lower alkyl, and R9 is lower alkyl; n is 0 or 1; R1 and R2 are independently hydrogen, lower alkyl, monoorganosilyl, diorganosilyl, triorganosilyl, halogen, aryl, or nitro; R3 is hydrogen, lower alkyl, monoorganosilyl, diorganosilyl, triorganosilyl, halogen, 9-fluorenylalkyl, cycloalkyl, aryl or aralkyl; R4 and R5 are independently hydrogen, lower alkyl, or aryl or one of R4 and R5 is 9-fluorenyl; R6 is H or COZ wherein Z is an amino acid, a peptide residue or a leaving group; and with the provisos that when n is 0 and R3 is hydrogen, R1 and R2 are not hydrogen, halogen or nitro; that when n is 0 and R3 is lower alkyl, R1 and R2 are not hydrogen; and that when X is O or CR7 R8 wherein R7 and R8 are H, that R1, R2, R3, R4, R5, and R6 are not all simultaneously H. The compounds of the present invention are useful in peptide synthesis as blocking or protecting groups for reactive groups. The present invention is also directed to a method of protecting a reactive group of an organic molecule during a reaction which modifies a portion of the molecule other than the protected group.
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- Pentacoordinate silicon compounds. Reactions of silatranes with nucleophiles
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The reactions of hydro, organyl and halosilatranes with nucleophiles have been studied.Substitution involving cleavage of equatorial Si-O bonds is always observed.Silitranes exhibit reactivity quite different from that of analogous trialkoxysilanes or anionic pentacoordinate silicon compounds.
- Cerveau, G.,Chuit, C.,Corriu, R. J. P.,Nayyar, N. K.,Reye, C.
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p. 159 - 168
(2007/10/02)
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- Tri(η-cyclopentadienyl)uranium(IV) Silyl and Siloxide Compounds. Crystal Structure of 5-C5H5)3(OSiPh3)>. Insertion of Isocyanide into a Uranium-Silicon Bond
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The complex 5-C5H5)3(SiPh3)> (1) has been synthesized from 5-C5H5)Cl> and Li(SiPh3) and fully characterized.The direct U-Si bond in (1) is quite reactive towards proton acidic molecules, moreover it reacts with 2,6-dimethylphenyl iscyanide to give the insertion product 5-C5H5)3(C(NC6H3Me2-2,6)SiPh3)> (3), the (1)H n.m.r. and i.r. data for which show that the isocyanide ligand is η2-co-ordinated to the uranium atom.The synthesis of 5-C5H5)3(OSiPh3)> (2) by reaction of 5-C5H5)3(NEt2)> with SiPh3(OH) and its X-ray structural determination are also reported.Compound (2) crystallizes from diethyl ether in the monoclinic space group P21/n with a=15.368(5), b=17.333(5), c=10.778(5) Angstroem, and β=106.27(3) deg for Z=4.The main features are the almost linear U-O-Si bond angle of 172.6(6) deg and the short U-O distance of 2.135(8) Angstroem.
- Porchia, Maria,Brianese, Nicola,Casellato, Umberto,Ossola, Franco,Rossetto, Gilberto,at al.
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p. 677 - 682
(2007/10/02)
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- A general route to five-coordinate hydridosilicates
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Five-coordinate potassium hydridosilicates, - K+ (R=Et, i-Pr, Ph), have been obtained in good yield from the reaction of a trialkoxy- or triaryloxy-silane with the corresponding potassium alkoxide or aryloxide, and characterized spectroscopically.Reaction of the hydrosilicates with an excess of Grignard reagent gives the corresponding triorganosilanes.
- Becker, B.,Corriu, R.,Guerin, C.,Henner, B.,Wang, Q.
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p. C33 - C35
(2007/10/02)
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- Five-coordinate potassium dihydridosilicates: synthesis and some aspects of their reactivity
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Five-coordinate potassium dihydridosilicates, K+- (R = Et, i-Pr) have been obtained by reaction of a trialkoxysilane with potassium hydride.Reaction of the dihydridosilicate with an excess of a Grignard reagent gives the corresponding diorganosilane.The ease of reduction of carbonyl compounds by the dihydridosilicate in the absence of a catalyst is indicative of the high reactivity of the Si-H bond in such species.
- Becker, B.,Corriu, R. J. P.,Guerin, C.,Henner, B.,Wang, Q.
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p. C25 - C28
(2007/10/02)
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- Cp2TiPh2-Catalyzed Dehydrogenative Coupling of Polyhydromonosilanes
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The Cp2TiPh2-catalyzed reaction of dihydrosilanes afforded dehydrogenative coupling products, disilanes and/or trisilanes.The reaction using phenylsilane produced hydride-terminated poly(phenylsilylene) polymers with Mn=730 and Mw=960, which exhibited the longest UV absorption maximum at 245 nm (ε, 5.7x104).
- Nakano, Taichi,Nakamura, Hidehisa,Nagai, Yoichiro
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- Hypervalent silicon hydrides: evidence for their intermediacy in the exchange reactions of di- and tri-hydrogenosilanes catalysed by hydrides (NaH, KH and LiAlH4)
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Di and tri-hydrogenosilanes, RR'SiH2 and RSiH3 (R=aryl, allyl or benzyl; R'=aryl or alkyl), readily undergo exchange reactions, involving silicon-carbon bonds and silicon-hydrogen bonds, in the presence of hydrides (LiAlH4, KH and NaH) as catalysts.These results are discussed in terms of five-coordinate silicon hydrides as intermediates in the reaction.
- Becker, B.,Corriu, R. J. P.,Guerin, C.,Henner, B. J. L.
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p. 147 - 154
(2007/10/02)
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- New mechanisms for the base-catalyzed cleavage of Si-Si bonds in organopolysilanes: the base-catalyzed solvolysis of pentaphenyldisilanecarboxylic acid and pentaphenyldisilanol in ethanol/water media
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A kinetic investigation of the base-catalyzed decomposition of pentaphenyldisilanecarboxylic acid (1) and pentaphenyldisilanol (2) in ethanol/water media is reported.The solvolysis of the Si-Si bond in 2, which also is formed on the base-catalyzed decarbonylation of 1, proceeds by concurrent first-order and second-order processes.At low base concentrations where the first-order process predominates, the intermediate, triphenylsilane (3), has been isolated.Solvent isotope effects and activation parameters have been determined.Mechanisms are proposed for the two kinetically distinguishable processes for Si-Si bond cleavage in which the pentaphenyldisilanolate ion undergoes either an internal nucleophilic displacement reaction or nucleophilic attack at Si by base in the rate-determining step.A general mechanistic approach for the cleavage of Si-Si bonds in polysilanes by aqueous-alcoholic base is proposed in which polysilonate ions are formed by nucleophilic attack by base at Si which undergo internal nucleophilic attack resulting in cleavage of the Si-Si bond adjacent to the anionic termini.Subsequently, polysilanolate ions are regenerated in which the number of Si atoms is reduced by one.
- Steward, Omar W.,Williams, James L.
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p. 199 - 212
(2007/10/02)
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- Siliciumhaltige Carben-Komplexe IX. Thermische Fragmentierung von Alkoxy(triphenylsilyl)carben-Komplexen, (CO)5MC(OR)SiPh3 (M=Cr, Mo, W)
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On thermolysis of (CO)3M=C(OEt)SiPh3 (M=W, Mo, Cr) in the solid state or in solution three different decomposition pathways are observed, which are unusual for Fischer-type carbene complexes; fragmentation of the complex to give triphenylsilane, ethylene
- Schubert, Ulrich,Hoernig, Hannelore
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p. 307 - 316
(2007/10/02)
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- A Thermally Induced Novel Fragmentation Reaction of Transition Metal Silylcarbene Complexes
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The carbene complexes (CO)5WC(OEt)SiPh3 (1) and (CO)5WC(NEt2)SiPh3 (2) thermally decompose to give triphenylsilane, ethylene, and W(CO)6 or (CO)5WCNEt, respectively, while in the presence of moist CO, 2O is formed, believed to arise via the ketene intermediate, Ph3Si(EtO)C=C=O.
- Schubert, Ulrich,Hoernig, Hannelore,Erdmann, Kai-Uwe,Weiss, Karin
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- Ylide Reactions of Benzyldimethylammonium Halides
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Deprotonation of benzyldimethylammonium halides (10) with sodium amide or n-butyllithium afforded silylated ylide intermediates 11, which were rearranged into N,N-dimethyl-2-benzylamines (13) accompanied by the formation of Sommelet-Hauser and Stevens rearrangement products (12 and 22).The ylide formation by the cleavage of carbon-silicon bonds also is discussed in the reaction of 10 with sodium amide and lithium aluminum hydride.
- Sato, Yoshiro,Yagi, Yoko,Koto, Masami
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p. 613 - 617
(2007/10/02)
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