- Reversible Silylene Insertion Reactions into Si?H and P?H σ-Bonds at Room Temperature
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Phosphine-stabilized silylenes react with silanes and a phosphine by silylene insertion into E?H σ-bonds (E=Si,P) at room temperature to give the corresponding silanes. Of special interest, the process occurs reversibly at room temperature. These results demonstrate that both the oxidative addition (typical reaction for transient silylenes) and the reductive elimination processes can proceed at the silicon center under mild reaction conditions. DFT calculations provide insight into the importance of the coordination of the silicon center to achieve the reductive elimination step.
- Rodriguez, Ricardo,Contie, Yohan,Nougué, Raphael,Baceiredo, Antoine,Saffon-Merceron, Nathalie,Sotiropoulos, Jean-Marc,Kato, Tsuyoshi
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Read Online
- Discrete spirobicyclic silicate anions with SiO2N2C, SiN2S2C and SiO4C frameworks
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Bis(2-aminobenzoato)phenylsilicate (1), bis(2-aminothiophenoxy) phenylsilicate (2), and bis(2-hydroxybenzoato) phenylsilicate (3) anions were obtained as their triethylammonium salts from the reactions of phenylsilane with appropriate ligands in the presence of triethylamine. The compounds were characterized by IR, multinuclear (1H, 13C, and 29Si) NMR, and FAB mass spectral data. Th X-ray crystal structure of 1.CH2Cl2 revealed slightly distorted trigonal bipyramidal geometry around silicon. The spirobicyclic silicate anions are the first examples with silicon-heteroatom linkages having six-membered (1) and five-membered (2) rings on silicon. Copyright Taylor & Francis Group, LLC.
- Narula, Suraj P.,Puri, Meenu,Garg, Neena,Puri, Jugal K.,Chadha, Raj K.
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Read Online
- Activations of all Bonds to Silicon (Si-H, Si-C) in a Silane with Extrusion of [CoSiCo] Silicide Cores
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The [BP3iPr]Co(I) synthon Na(THF)6{[BP3iPr]CoI} (1, [BP3iPr] = κ3-PhB(CH2PiPr2)3-) reacts with PhSiH3 or SiH4 to form unusual {[BP2iPr](SiH2R)CoH2}=Si={H2Co[BP3iPr]} species (R = Ph, 2a; R = H, 2b; [BP2iPr] = κ2-PhB(CH2PiPr2)2) that result from activation of all Si - H and Si - C bonds in the starting silanes. Solution-spectroscopic data (multinuclear NMR, IR) for 2a,b, and the solid-state structure of 2a, indicate substantial Co=Si=Co multiple bonding and minimal interaction of the core Si atom with nearby hydride ligands. In the presence of 4-dimethylaminopyridine (DMAP), 1 reacts with PhSiH3 to give [BP3iPr](H)2CoSiHPh(DMAP) (3). Complexes 2a,b eliminate RSiH3 upon thermolysis in the presence of DMAP to generate {[BP2iPr]Co(NC5H3NMe2)}=Si={H2Co[BP3iPr]} (4).
- Handford, Rex C.,Smith, Patrick W.,Tilley, T. Don
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supporting information
p. 8769 - 8772
(2019/06/07)
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- CO Displacement in an Oxidative Addition of Primary Silanes to Rhodium(I)
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The rhodium dicarbonyl {PhB(Ox Me2)2ImMes}Rh(CO)2 (1) and primary silanes react by oxidative addition of a nonpolar Si-H bond and, uniquely, a thermal dissociation of CO. These reactions are reversible, and kinetic measurements model the approach to equilibrium. Thus, 1 and RSiH3 react by oxidative addition at room temperature in the dark, even in CO-Saturated solutions. The oxidative addition reaction is first-Order in both 1 and RSiH3, with rate constants for oxidative addition of PhSiH3 and PhSiD3 revealing kH/kD a 1. The reverse reaction, reductive elimination of Si-H from {PhB(Ox Me2)2ImMes}RhH(SiH2R)CO (2), is also first-Order in [2] and depends on [CO]. The equilibrium concentrations, determined over a 30 °C temperature range, provide ?"H° = a'5.5 ± 0.2 kcal/mol and ?"S° = a'16 ± 1 cal·mol-1K-1 (for 1 a?., 2). The rate laws and activation parameters for oxidative addition (?"Ha§§ = 11 ± 1 kcal·mol-1 and ?"Sa§§ = a'26 ± 3 cal·mol-1·K-1) and reductive elimination (?"Ha§§ = 17 ± 1 kcal·mol-1 and ?"Sa§§ = a'10 ± 3 cal·mol-1K-1), particularly the negative activation entropy for both forward and reverse reactions, suggest the transition state of the rate-Determining step contains {PhB(Ox Me2)2ImMes}Rh(CO)2 and RSiH3. Comparison of a series of primary silanes reveals that oxidative addition of arylsilanes is ca. 5× faster than alkylsilanes, whereas reductive elimination of Rh-Si/Rh-H from alkylsilyl and arylsilyl rhodium(III) occurs with similar rate constants. Thus, the equilibrium constant Ke for oxidative addition of arylsilanes is >1, whereas reductive elimination is favored for alkylsilanes.
- Biswas, Abhranil,Ellern, Arkady,Sadow, Aaron D.
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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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- Catalytic Reduction of Alkoxysilanes with Borane Using a Metallocene-Type Yttrium Complex
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The catalytic reduction of alkoxysilanes with the borane HBpin (pin = pinacolato) was achieved using a metallocene-type yttrium complex as a catalyst precursor. Mechanistic study supported the pivotal role of the rigid metallocene structure of the catalyst, which bears two bulky n5-C5Me4SiMe3 ligands, in suppressing the coordination of the side product MeOBpin that is generated during the reaction.
- Aoyagi, Keiya,Matsumoto, Kazuhiro,Shimada, Shigeru,Sato, Kazuhiko,Nakajima, Yumiko
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supporting information
p. 210 - 212
(2019/02/01)
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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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- SYNTHESIS OF ORGANO CHLOROSILANES FROM ORGANOSILANES
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The invention relates to a process for the production of chlorosilanes by subjecting one or more hydndosilanes to the reaction with hydrogen chloride in the presence of at least one ether compound, and a process for the production of such hydndosilanes serving as starting materials.
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Page/Page column 47
(2019/04/16)
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- METHOD FOR PRODUCING HYDROSILANE
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PROBLEM TO BE SOLVED: To provide a method for producing hydrosilane capable of efficiently producing hydrosilane under mild conditions. SOLUTION: Provided is a method for producing hydrosilane where hydrosilane can be efficiently produced by reacting alkoxysilane having a structure represented by formula (a) with hydroborane and/or hydrogen under the presence of a complex with at least one kind of atom selected from the group consisting of a yttrium atom (Y), a zirconium atom (zr) and a hafnium atom (Hf) as a central metal(s)(in the formula (a), R denotes a 1 to 20C hydrocarbon group). SELECTED DRAWING: None COPYRIGHT: (C)2018,JPO&INPIT
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Paragraph 0025
(2019/01/06)
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- Custom Hydrosilane Synthesis Based on Monosilane
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The omnipresence of silicon compounds with carbon substituents in synthetic chemistry hides the fact that, except for certain substitution patterns at the silicon atom, their preparation is often far from trivial. The challenge is rooted in the lack of control over nucleophilic substitution with carbon nucleophiles at silicon atoms with three or four leaving groups. For example, SiCl4 usually converts into intractable mixtures of chlorosilanes, typically requiring several distillation cycles to reach high purity. Accordingly, there is no universal approach to silanes with heteroleptic substitution. Here, using a bench-stable SiH4 surrogate, we introduce a general strategy for the on-demand synthesis of silicon compounds decorated with different aryl and alkyl substituents. Reliable protocols are the basis of the selective and programmable synthesis of dihydro- and monohydrosilanes; aryl-substituted trihydrosilanes are also accessible in a straightforward fashion. These otherwise difficult-to-access hydrosilanes are only three or fewer easy synthetic operations away from the SiH4 surrogate. Synthesizing silicon compounds with different carbon substituents from inorganic silicon precursors, i.e., basic silicon chemicals with hydrogen, halogen, or alkoxy substitution, is an intricate and often insoluble task. It is generally difficult to chemoselectively address one of these groups in chemical reactions, particularly when two or more of those are identical. Complicated separation and purification procedures are the result. The challenge of making these silicon compounds containing silicon–carbon bonds, typically hydro- and chlorosilanes, is accentuated considering their high demand in academia and industry. The present approach is a step forward in solving those limitations. It hinges on the stepwise decoration of the silicon atom of a liquid monosilane surrogate. Further development of this strategy and adjusting it to industrial needs could pave the way to easy access of an even more diverse manifold of silicon compounds for synthetic chemistry and material science. Oestreich and colleagues present an approach to the chemoselective stepwise preparation of hydrosilanes with the general formula R4–nSiHn where n = 1–3 and R can be different aryl and alkyl groups. The starting point is a bench-stable SiH4 surrogate with two Si–H bonds masked as cyclohexa-2,5-dien-1-yl substituents. A sequence of palladium-catalyzed Si–H arylation and B(C6F5)3-promoted deprotection and transfer hydrosilylation enables the programmable synthesis of hydrosilanes, even with three different substituents at the silicon atom.
- Yuan, Weiming,Smirnov, Polina,Oestreich, Martin
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p. 1443 - 1450
(2018/04/20)
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- Organometallic Complexes of Bulky, Optically Active, C 3-Symmetric Tris(4 S -isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate (ToP)
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A bulky, optically active monoanionic scorpionate ligand, tris(4S-isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate (ToP), is synthesized from the naturally occurring amino acid l-valine as its lithium salt, Li[ToP] (1). That compound is readily converted to the thallium complex Tl[ToP] (2) and to the acid derivative H[ToP] (3). Group 7 tricarbonyl complexes ToPM(CO)3 (M = Mn (4), Re (5)) are synthesized by the reaction of MBr(CO)5 and Li[ToP] and are crystallographically characterized. The νCO bands in their infrared spectra indicate that π back-donation in the rhenium compounds is greater with ToP than with non-methylated tris(4S-isopropyl-2-oxazolinyl)phenylborate (ToP). The reaction of H[ToP] and ZnEt2 gives ToPZnEt (6), while ToPZnCl (7) is synthesized from Li[ToP] and ZnCl2. The reaction of ToPZnCl and KOtBu followed by addition of PhSiH3 provides the zinc hydride complex ToPZnH (8). Compound 8 is the first example of a crystallographically characterized optically active zinc hydride. We tested its catalytic reactivity in the cross-dehydrocoupling of silanes and alcohols, which provided Si-chiral silanes with moderate enantioselectivity (Chemical Equation).
- Xu, Songchen,Magoon, Yitzhak,Reinig, Regina R.,Schmidt, Bradley M.,Ellern, Arkady,Sadow, Aaron D.
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p. 3508 - 3519
(2015/08/06)
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- Base-catalyzed hydrosilylation of ketones and esters and insight into the mechanism
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Simple bases (KOtBu, KOH) catalyze the silane-promoted reduction of ketones and esters to alcohols and of aldimines to amines. The inexpensive silane PMHS (polymethylhydrosiloxane) can be used as the reducing reagent. Double and triple bonds, as well as nitro- and cyano-groups are tolerated. Careful dosing of the silane allows for chemoselective reduction of a more reactive group in the presence of a less reactive group (for example, aldehyde reduction in the presence of ketone/ketone reduction in the presence of ester group). Mechanistic studies showed that addition of base to silanes leads to silicate species, which are the acting reducing agents. Under basic conditions, hydrosiloxanes (tetramethyldisiloxane, TMDS; PMHS) convert into simple silanes (H 2SiMe2, H3SiMe), making this a practical method to generate these challenging silanes. Copyright
- Revunova, Kseniya,Nikonov, Georgii I.
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supporting information
p. 839 - 845
(2014/01/23)
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- Synthesis of phenylsilocane tritium-labeled at the benzene ring
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A strategy for synthesis of the 2-phenyl-2-hydro-1,3-oxa-6-aza-2-silacyclooctane doubly tritium-labeled (2,4- or 2,6-) at the benzene ring has been elaborated. The products are sources of the silyl cations having the atrane structure.
- Avrorin,Fominykh,Ignat'Ev,Sinotova,Kochina
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p. 2125 - 2129
(2015/02/02)
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- One-pot synthesis and structural characterization of poly(alkoxysilane)s catalyzed by silver-gold complexes
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Combinative one-pot Si-Si/Si-O dehydrocoupling of hydrosilanes with alcohols (1:1.5 mole ratio), mediated by a mixture of AgNO3-AuCl 3 (100/1 mole ratio) rapidly produced poly(alkoxysilane)s in reasonably high yield. The addition of small amount of gold complex to the reaction mixture effectively accelerated the coupling reaction compared to the reaction rate with AgNO3 alone. The hydrosilanes include p-X-C 6H4SiH3 (X = H, CH3, OCH 3, F), PhCH2SiH3, and (PhSiH2) 2. The alcohols include MeOH, EtOH, iPrOH, PhOH, and CF 3(CF2)2CH2OH. The weight average molecular weight and polydispersity of the poly(alkoxysilane)s were in the range of 1,600~8,000 Dalton and 1.4~3.5, respectively. The dehydrocoupling reactions of phenylsilane with ethanol (1:3 mole ratio) in the presence of the Ag-Au complexes gave only triethoxyphenylsilane. Copyright
- Cheong, Hyeonsook,Roh, Sung-Hee,Cho, Myong-Shik,Kim, Myoung-Hee,Woo, Hee-Gweon,Yang, Kap-Seung,Kim, Bo-Hye,Jun, Jin,Sohn, Honglae
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p. 702 - 705
(2013/06/26)
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- METHOD OF REDUCING A HALOSILANE COMPOUND IN A MICROREACTOR
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A method of producing a hydrosilane compound in a microreactor comprises reducing a halosilane compound in the microreactor and in the presence of a reducing agent to produce the hydrosilane compound.
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Paragraph 0037-0042
(2013/08/28)
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- Reversible addition of the Si-H bond of phenylsilane to the Sc=N bond of a scandium terminal imido complex
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The facile and reversible addition of the Si-H bond of phenylsilane to the Sc=N bond of the scandium terminal imido complex [LSc=NDIPP(DMAP)] (1; L = [MeC(N(DIPP))CHC(Me)(NCH2CH2NMe)]-, DIPP = 2,6-iPr2C6H3) is reported. The reaction gives the scandium anilido hydride [LSc(H)(N(DIPP)(SiH2Ph))] (2), and a labeling experiment shows a rapid σ-bond metathesis between Sc-H of the formed scandium anilido hydride and Si-H of phenylsilane during the reaction. 2 was trapped by an insertion reaction with diphenylcarbodiimide, giving the stable scandium anilido amidinate [LSc(N(DIPP)(SiH 2Ph))(κ2(N,N′)-PhNCHNPh)] (3). Furthermore, the scandium terminal imido complex can efficiently catalyze the hydrosilylation of N-benzylidenepropan-1-amine. The reaction was completed within 2 h at 50 C with 5 mol % of catalyst loading and highly selectively produced the monoaminosilane.
- Chu, Jiaxiang,Lu, Erli,Chen, Yaofeng,Leng, Xuebing
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supporting information
p. 1137 - 1140
(2013/05/21)
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- Borane-catalyzed Si-H activation routes to polysilanes containing thiolato side chains
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Dehydrocoupling and hydrosilation reactions of the Si-H bonds in poly(phenylsilane) catalyzed by B(C6F5)3 allow the preparation of new polymers containing both Si-H and Si-SR side chains. This postpolymerization modification takes place without any observable competing Si-Si bond cleavage, unlike other Lewis acid, transition-metal, or radical mediated routes. The -SR-functionalized polymers have been characterized by GPC, IR, UV-vis, elemental analysis, and 1H, 13C, and 29Si NMR.
- Lee, Peter T. K.,Skjel, Miranda K.,Rosenberg, Lisa
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supporting information
p. 1575 - 1578
(2013/05/09)
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- Synthesis, structure, and reactivity of a mononuclear organozinc hydride complex: Facile insertion of CO2 into a Zn-H bond and CO 2-promoted displacement of siloxide ligands
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Tris(2-pyridylthio)methane, [Tptm]H, has been employed to synthesize the mononuclear alkyl zinc hydride complex, [κ3-Tptm]ZnH, which has been structurally characterized by X-ray diffraction. [κ3- Tptm]ZnH provides access to a variety of other [Tptm]ZnX derivatives. For example, [κ3-Tptm]ZnH reacts with (i) R3SiOH (R = Me, Ph) to give [κ4-Tptm]ZnOSiR3, (ii) Me 3SiX (X = Cl, Br, I) to give [κ4-Tptm]ZnX, and (iii) CO2 to give the formate complex, [κ4-Tptm]ZnO 2CH. The bis(trimethylsilyl)amide complex [κ3-Tptm] ZnN(SiMe3)2 also reacts with CO2, but the product obtained is the isocyanate complex, [κ4-Tptm]ZnNCO. The formation of [κ4-Tptm]ZnNCO is proposed to involve initial insertion of CO2 into the Zn-N(SiMe3)2 bond, followed by migration of a trimethylsilyl group from nitrogen to oxygen to generate [κ4-Tptm]ZnOSiMe3 and Me3SiNCO, which subsequently undergo CO2-promoted metathesis to give [κ4-Tptm]ZnNCO and (Me3SiO)2CO.
- Sattler, Wesley,Parkin, Gerard
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p. 9708 - 9711
(2011/08/03)
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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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- Nonhydride mechanism of metal-catalyzed hydrosilylation
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A 1:1:1 reaction between complex (Tp)(ArN=)Mo(H)(PMe3) (3), silane PhSiD3, and carbonyl substrate established that hydrosilylation catalyzed by 3 is not accompanied by deuterium incorporation into the hydride position of the catalyst, thus ruling out the conventional hydride mechanism based on carbonyl insertion into the M-H bond. An analogous result was observed for the catalysis by (O=)(PhMe2SiO)Re(PPh 3)2(I)(H) and (Ph3PCuH)6.
- Shirobokov, Oleg G.,Kuzmina, Lyudmila G.,Nikonov, Georgii I.
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supporting information; experimental part
p. 6487 - 6489
(2011/06/23)
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- Synthesis and structure of PNP-supported iridium silyl and silylene complexes: Catalytic hydrosilation of alkenes
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Oxidative addition of bulky primary, secondary, and tertiary silanes to PNP (PNP ) [N(2-PiPr2-4-Me-C6H3) 2]-) iridium complexes (PNP)IrH2 and (PNP)Ir(COE) (11) afforded iridium silyl hydride complexes (PNP)Ir(H) (SiRR′R″) (3-8). Addition of 2 equiv of PhSiH3 or (3,5-Me2C6H3)SiH3 to (PNP)IrH 2 or 11 yielded disilyl complexes (PNP)Ir(SiH2R) 2 (R ) Ph (9), 3,5-Me2C6H3 (10)). Hydride abstraction from (PNP)Ir-(H)(SiH2R) (R = Trip (5), Dmp (6)) by [Ph3C][B(C6F5)4] afforded iridium silylene complexes [(PNP)(H)Ir=SiR(H)][B(C6F5) 4] (R ) Trip (12), Dmp (13)) exhibiting downfield 29Si NMR resonances (234 ppm (12), 226 ppm (13)) and downfield 1H NMR resonances for the Si-H group (10.76 ppm (12), 9.76 ppm (13)). Thermally stable disubstituted silylene complexes [(PNP)(H)Ir=SiPh2][A] (A = -B(C 6F5)4 (14), -CB11H 6Br6 (16)) were isolated via hydride abstraction from (PNP)Ir(H)(SiHPh2). The X-ray structure of 16 confirmed sp 2 hybridization at silicon and revealed a short Ir-Si bond of 2.210(2) A. Catalytic hydrosilation of alkenes by hydrogen-substituted silylene complexes [(PNP)(H)Ir=SiMes(H)][B(C6F5) 4] (1) and 14 exhibited anti-Markovnikov regioselectivity with an array of alkene substrates. Addition of H3SiMes to complex 1 afforded [(PNP)(SiH(Mes)(Hex))IrH(SiH2Mes)][B(C6F 5)4] (19), featuring a β-agostic interaction demonstrated by a JSiH of 102 Hz for the N-SiH hydrogen. Similarly, addition of H2SiPh2 to 16 afforded the structurally characterized Ir(V) disilyl complex [(PNP)(SiPh2)Ir(SiPh 2H)(H)2][CB11H6Br6] (20). Complex 20 was found to be catalytically active for the hydrosilation of alkenes, which is consistent with its intermediacy in the catalytic cycle.
- Calimano, Elisa,Tilley, T. Don
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body text
p. 11161 - 11173
(2009/12/05)
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- Electrochemical synthesis of symmetrical difunctional disilanes as precursors for organofunctional silanes
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Difunctional disilanes of the general type XR2SiSiR2X (1-5) (X = OMe, H; R = Me, Ph, H) have been synthesized by electrolysis of the appropriate chlorosilanes XR2SiCl in an undivided cell with a constant current supply and in the absence of any complexing agent. Reduction potentials of the chlorosilane starting materials derived from cyclic voltammetry measurements were used to rationalize the results of preparative electrolyses. Organofunctional silanes of the general formula MeO(Me 2)SiC6H4Y (6a-c, 7) were subsequently obtained by the reaction of sym-dimethoxytetramethyldisilane (1) with NaOMe in the presence of p-functional aryl bromides BrC6H4Y (Y = OMe, NEt2, NH2).
- Grogger, Christa,Loidl, Bernhard,Stueger, Harald,Kammel, Thomas,Pachaly, Bernd
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p. 105 - 110
(2007/10/03)
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- One-pot synthesis of poly(alkoxysilane)s by Si-Si/Si-O dehydrocoupling of silanes with alcohols using Group IV and VIII metallocene complexes
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Si-Si/Si-O dehydrocoupling reactions of silanes with alcohols (1:1.5 mole ratio), catalyzed by Cp2MCl2/Red-Al (M=Ti, Zr) and Cp2M′ (M′=Co, Ni), produced poly(alkoxysilane)s in one-pot in high yield. The silanes included p-X-C6H4SiH3 (X=H, CH3, OCH3, F), PhCH2SiH3, and (PhSiH2)2. The alcohols were MeOH, EtOH, iPrOH, PhOH, and CF3(CF2) 2CH2OH. The weight average molecular weight of the poly(alkoxysilane)s ranged from 600 to 8000. The dehydrocoupling reactions of phenylsilane with ethanol (1:1.5 mole ratio) using Cp2HfCl2/Red-Al and phenylsilane with ethanol (1:3 mole ratio) using Cp2TiCl2/Red-Al gave only triethoxyphenylsilane as product.
- Kim, Bo-Hye,Cho, Myong-Shik,Kim, Mi-Ae,Woo, Gee-Gweon
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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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- Synthesis of difunctional 1,4-dimethyl-1,4-disilacyclohexanes
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Transformations of HVinSiCl2, HVinSi(Me)Cl, HVinSi(Me)Ph, and HVinSi(Me)NEt2 in the presence of Pt catalyst were studied. In dilute solutions, the reaction gave a mixture of structural and stereoisomers of five- and six-membered disilacyclanes, resulting from intramolecular cyclization of the initially formed linear dimer. In the case of methyl(phenyl)disilacyclane, the structural isomers were separated and tran.s-1,4-dimethyl-1,4-diphenyl-1,4-disilacyclohexane was isolated. The reaction of this product with HCI in the presence of AlCl3 followed by hydrolysis resulted in the synthesis of trans-1,4-dichloro- and trans-1,4-dihydroxy-1,4-dimethyl-1,4-disilacyclohexanes. The structures of the structural and stereoisomers synthesized were confirmed by 1H, 13C, and 29Si NMR and IR spectroscopies and mass spectrometry.
- Volkova,Petrova,Chizhova,Petrovskii,Vinogradova,Makarova
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p. 1712 - 1716
(2007/10/03)
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- Synthesis, structure and photoluminescence of 1,2-disila-acenaphthene Si2C10H10 and 1,2-diaryldisilane reference compounds
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For the synthesis of the diaryldisilanes Ar-SiH2SiH2-Ar (la, Ar = phenyl; Ib, Ar = p-tolyl; le, Ar = mesityl; Id, Ar = p-anisyl) two convenient preparative routes are reported. The crystal structures of le and Id have been determined in Xray diffraction studies; the disilanes have a staggered transconformation with a crystallographically imposed center of inversion. For la-d no photoluminescence phenomena can be observed. 1,2-Disila-acenaphthene (2) is synthesized in acceptable yield by treatment of 1,8-dilithionaphthalene with 1 equivalent of l,2-bis[((trifluoromethyl)sulfonyl)oxy]disilane Tf-SiH2SiH2-Tf. The crystal structure of 2 has also been determined by X-ray diffraction. The molecule has no crystallographically imposed symmetry but closely follows the symmetry elements of point group C2v. Solutions of 2 exhibit intense fluorescence in the near UV region at room temperature. The fluorescence spectra are discussed in comparison with data on acenaphthene and naphthalene. WILEY-VCH Verlag GmbH 1997.
- Soeldner, Marcus,Sandor, Mario,Schier, Annette,Schmidbaur, Hubert
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p. 1671 - 1676
(2007/10/03)
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- Carbanion mechanisms XX. Is there charge delocalization in phenyl-substituted Group 4 anions? Evidence from electronic absorption spectroscopy
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From the electronic absorption spectra of the triphenyl silyl, germyl, stannyl and plumbyl anions Ph3E- (E = Si, Ge, Sn or Pb), it is concluded that there exists in these species almost no conjugation between the Group 4 element and the phenyl group substituents, contrasting with the Ph3C- carbanion. A similar conclusion can be drawn from the near constancy of λmax values in the series Ph3Si-, Ph2SiH- and PhSiH-2.
- Buncel, Erwin,Gordon, Robert D.,Venkatachalam, T. Krishnan
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- Primary Reaction Channels and Kinetics of the Thermal Decomposition of Phenylsilane
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The thermally induced decomposition of phenylsilane has been investigated by three different experimental methods: a static method, a comparative rate-single pulse shock tube (CR-SPST) method, and a very low-pressure pyrolysis (VLPP) method.Decomposition is mainly heterogeneous under static conditions but appears homogeneous in the other two systems.Homogeneous dissociations occur by two channels with yields, PhSiH3H2+PhSiH, φ1 ca. 0.84; PhSiH3PhH+SiH2, φ2 ca.0.16 +/-0.04.Coupling of CR-SPST and homogeneous static reactor data spanning temperatures from 693 to 1236 K for the benzene formation channel and adjusting for falloff by RRKM methods gives high-pressure Arrhenius parameters of A1 = 1014.0+/-0.4, E1 = 59.3 +/- 2.1 and A2 = 1013.9+/-0.2, E2 = 62.0 +/- 0.9 (A in s-1 and E in kcal/mol) for the two primary dissociation channels.These parameters yield RRKM calculated rate constant under VLPP conditions which agree within the errors with experimental rate constants.
- O'Neal, H. E.,Ring, M. A.,Kim, D.,King, K. D.
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p. 9397 - 9402
(2007/10/02)
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- Dehydrogenative polymerization of silanes to polysilanes by zirconocene and hafnocene catalysts. A new polymerization mechanism
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We have found that a number of zirconium and hafnium siyl complexes of the type Cp′2M(SiR3)R′ (Cp′ = η5-C5H5, Cp (η5-C5Me5); M = Zr, Hf; R = Me, Ph, SiMe3; R′ = Cl, alkyl, silyl) are catalyst precursors for this dehydrogenative coupling reaction and that polymer molecular weights can vary as a function of reaction conditions and catalyst. Improvement of this method relies heavily on an understanding of the polymerization mechanism, which has remained obscure. This report describes observations that suggest a mechanism for dehydrogenative silane polymerization by zirconocene and hafnocene catalysts.
- Woo, Hee-Gweon,Tilley, T. Don
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p. 8043 - 8044
(2008/10/08)
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- Reactivity of Hypervalent Species: Reactions of Anionic Penta-Coordinated Silicon Complexes towards Nucleophiles
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The reactivity of anionic penta-coordinated silicon complexes 4-O)2>-Na+ 1 with nucleophilic reagents has been studied. 1 can be reduced to organosilanes RSiH3 by metallic hydrides.Reactions with an excess of Grignard or organolithium reagents (R'MgX or R'Li) gave tetraorganosilanes RSiR'3.When only two molar equivalents of Grignard reagents (R'MgX) or lithium reagents (R'Li) are added to complexs 1 functional silanes RR'2SiX can be prepared.
- Boudin, Alain,Cerveau, Genevieve,Chuit, Claude,Corriu, Robert J. P.
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p. 101 - 106
(2007/10/02)
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- Process for the preparation of hydrogenosilanes or halogenosilanes
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A process for the preparation of hydrogenosilanes or halogenosilanes corresponding to the general formula I:
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- Deuterium Isotope Effects on Silicon-29 Chemical Shifts
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The deuterium isotope effects on the 29Si chemical shifts in several organosilanes and siloxanes have been determined.For silanes, the one-bond effects are approximately -0.2 ppm per deuterium and follow an additivity relationship.The two-bond effect is small.
- Berchier, Fabienne,Pai, Yi-Ming,Weber, William P.,Servis, Kenneth L.
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p. 679 - 680
(2007/10/02)
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- Alkyl and Silyl Derivatives of Benzene Radical-cations formed by Radiolysis : an Electron Spin Resonance Study
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Exposure of dilute solutions of variuos alkyl- and silyl-benzenes in trichlorofluoromethane to 60CoSg-rays at 77 K gave species whose e.s.r. spectra are characteristic of substituted benzene cations.For the ethyl derivative large hyperfine coupling to the methyl protons establishes a preferred conformation in which the methyl group lies in the plane of the benzene ring.For the isopropyl derivative, and particularly for p-cymene cations, several conformes were detected, the sterically most favourable being the least stable.This is interpreted in terms of strong electron-donation from the C-H ?-orbitals into the ring ?-orbital with is greater than that from C-Me ?-orbitals so that ?-overlap with the C-H bonds is maximised.The energy difference is slightly greater than the steric energy differences.The SOMO for the silyl derivatives (SiH3, SiHMe2, and SiMe3) is also the a1 orbital (ΠSa) which places maximum spin-density on the position of the substituent.However, the degree of hyperconjugation involving Si-H ?-orbitals is reduced by a factor of ca. 2, as judged by the 1H hyperfine coupling constants.Nevertheless, it was not found necessary to invoke a mixture of the a1 and a2 orbitals (ΠSS and ΠSA) to explain the results.These results are compared wiyh those for the corresponding radical-anions and for the neutral cyclopentadienyl radicals.
- Ramakrishna Rao, D. N.,Chandra, Harish,Symons, Martyn C. R.
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p. 1201 - 1206
(2007/10/02)
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- CARBON-SILICON BOND CLEAVAGE OF ORGANOTRIALKOXYSILANES AND ORGANOSILATRANES WITH m-CHLOROPERBENZOIC ACID AND N-BROMOSUCCINIMIDE. NEW ROUTE TO PHENOLS, PRIMARY ALCOHOLS AND BROMIDES
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Alkyl- and aryltriethoxysilanes undergo oxidative carbon-silicon bond cleavage smoothly with m-chloroperbenzoic acid (MCPBA) to afford the corresponding alcohols.Silatranes similarly gave alcohols and bromides with MCPBA and N-bromosuccinimide, respectively.
- Hosomi, Akira,Iijima, Susumu,Sakurai, Hideki
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p. 243 - 246
(2007/10/02)
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- Vibrational spectra and structure of some silicon containing compounds-IV1 1 For Part III, see J. Mol. Struct. 6, 315 (1970). Normal vibrations and free rotation in phenylsilane
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The i.r. spectra of liquid and gaseous phenylsilane and gaseous phenylsilane-d3 have been recorded from 3500 to 33 cm-1. The Raman spectra of the liquids have also been recorded and depolarization values have been measured. The vapor
- Durig,Hellams,Mulligan
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p. 1039 - 1057
(2007/10/06)
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