- Redox-state dependent activation of silanes and ammonia with reverse polarity (PCcarbeneP)Ni complexes: electrophilic vs. nucleophilic carbenes
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A rigidified PCalkylP ligand allowed for the synthesis and characterization of cationic and radical PCCarbeneP nickel complexes in which the carbene anchor of the pincer framework is electrophilic rather than nucleophilic. Alpha-hydride abstraction from a (PCalkylP)nickel halide complex readily leads to the cationic carbene complex, which furnishes the radical carbene complex by one electron reduction. The reactivity of these reverse polarity carbene complexes towards small molecules (H2, CO, CO2, R3SiH, NH3) reveals different modes of activation when compared to previously reported nucleophilic nickel carbene complexes, and a clear dependence on the redox state of the complex. For H2, CO and CO2, no reaction is observed, but silanes react via hydride transfer and formation of solvated silylium ions. Ammonia is activated in a novel way, wherein it coordinates the carbene carbon and is deprotonated to form a robust C-N bond. This is not only a rare example of ammonia activation by a first row transition metal but also evidence of the intermediacy of group 10 carbenes in direct C-N bond forming reactions.
- LaPierre, Etienne A.,Piers, Warren E.,Gendy, Chris
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Read Online
- Activation of SF6 at a Xantphos-Type Rhodium Complex
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As a rather inert gas, sulfur hexafluoride is still used as a dielectric in high-voltage power applications despite its high global warming potential. Its activation at transition metal complexes has been reported, but the fate of the sulfur-containing products is often unknown. The activation of SF6 at [Rh(H){tBuxanPOP}] (tBuxanPOP = 9,9-dimethyl-4,5-bis(ditert-butylphosphino)xanthene) at room temperature leads to the generation of the bifluorido complex [Rh(FHF){tBuxanPOP}]. A subsequent regeneration of [Rh(H){tBuxanPOP}] completes a cyclic process for the degradation of SF6. Furthermore, the SF6 activation at [Rh(H){tBuxanPOP}] in the presence of triethylsilane as a hydrogen source is described, which leads to the formation of the fluorido complex [Rh(F)2(H){tBuxanPOP}] as well as [Rh(SH){tBuxanPOP}] and S(SiEt3)2 as sulfur-containing products.
- Wozniak, Martin,Braun, Thomas,Ahrens, Mike,Braun-Cula, Beatrice,Wittwer, Philipp,Herrmann, Roy,Laubenstein, Reik
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Read Online
- Synthesis of bis(trifluoromethyl)alkylated trisubstituted alkenes via highly regioselective catalyzed hydrosilylation reaction of hexafluoro-2-butyne and their reactivity
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Hydrosilylation reaction of hexafluoro-2-butyne 1 (HFB) with various silanes in the presence of a catalytic amount of transition-metal-catalysts was investigated. The reaction of HFB gave the corresponding bis(trifluoromethyl)containing vinylsilanes in an excellent regioselective manner in high yields. Treatment of the resulting vinylsilanes with various aldehydes and ketones in the presence of fluoride ion sources afforded the coupling products in moderate yields.
- Filatov, Andrey A.,Jackson, Andrew,Kirij, Nataliia V.,Peng, Sheng,Yagupolskii, Yurii L.
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- Bis(perfluoropinacolato)silane: A Neutral Silane Lewis Superacid Activates Si?F Bonds
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Despite the earth abundance and easy availability of silicon, only few examples of isolable neutral silicon centered Lewis superacids are precedent in the literature. To approach the general drawbacks of limited solubility and unselective deactivation pathways, we introduce a Lewis superacid, based on perfluorinated pinacol substituents. The compound is easily synthesized on a gram-scale as the corresponding acetonitrile mono-adduct 1?(MeCN) and was fully characterized, including single crystal X-ray diffraction analysis (SC-XRD) and state-of-the-art computations. Lewis acidity investigations by the Gutmann-Beckett method and fluoride abstraction experiments indicate a Lewis superacidic nature. The challenging Si?F bond activation of Et3SiF is realized and promising catalytic properties are demonstrated, consolidating the potential applicability of silicon centered Lewis acids in synthetic catalysis.
- Greb, Lutz,Hanusch, Franziska,Inoue, Shigeyoshi,Thorwart, Thadd?us,Tschernuth, Florian S.
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supporting information
p. 25799 - 25803
(2021/11/09)
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- Visible-light photoredox-catalyzed selective carboxylation of C(sp3)?F bonds with CO2
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It is highly attractive and challenging to utilize carbon dioxide (CO2), because of its inertness, as a nontoxic and sustainable C1 source in the synthesis of valuable compounds. Here, we report a novel selective carboxylation of C(sp3)?F bonds with CO2 via visible-light photoredox catalysis. A variety of mono-, di-, and trifluoroalkylarenes as well as α,α-difluorocarboxylic esters and amides undergo such reactions to give important aryl acetic acids and α-fluorocarboxylic acids, including several drugs and analogs, under mild conditions. Notably, mechanistic studies and DFT calculations demonstrate the dual role of CO2 as an electron carrier and electrophile during this transformation. The fluorinated substrates would undergo single-electron reduction by electron-rich CO2 radical anions, which are generated in situ from CO2 via sequential hydride-transfer reduction and hydrogen-atom-transfer processes. We anticipate our finding to be a starting point for more challenging CO2 utilization with inert substrates, including lignin and other biomass.
- Bo, Zhi-Yu,Chen, Lin,Gao, Tian-Yu,Jing, Ke,Lan, Yu,Liu, Shi-Han,Luo, Shu-Ping,Yan, Si-Shun,Yu, Bo,Yu, Da-Gang
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supporting information
p. 3099 - 3113
(2021/11/16)
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- Isolable Silicon-Based Polycations with Lewis Superacidity
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Molecular silicon polycations of the types R2Si2+ and RSi3+ (R=H, organic groups) are elusive Lewis superacids and currently unknown in the condensed phase. Here, we report the synthesis of a series of isolable terpyridine-stabilized R2Si2+ and RSi3+ complexes, [R2Si(terpy)]2+ (R=Ph 12+; R2=C12H8 22+, (CH2)3 32+) and [RSi(terpy)]3+ (R=Ph 43+, cyclohexyl 53+, m-xylyl 63+), in form of their triflate salts. The stabilization of the latter is achieved through higher coordination and to the expense of reduced fluoride-ion affinities, but a significant level of Lewis superacidity is nonetheless retained as verified by theory and experiment. The complexes activate C(sp3)?F bonds, as showcased by stoichiometric fluoride abstraction from 1-fluoroadamantane (AdF) and the catalytic hydrodefluorination of AdF. The formation of the crystalline adducts [2(F)]+ and [5(H)]2+ documents in particular the high reactivity towards fluoride and hydride donors.
- Hermannsdorfer, André,Driess, Matthias
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supporting information
p. 23132 - 23136
(2020/10/19)
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- PROCESS FOR PRODUCING SULFONIC ACID GROUP-CONTAINING MONOMER
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The present disclosure is directed to provide a process capable of producing a sulfonic acid group-containing monomer in a good yield, which can be used as a raw material of fluorine-based polymer electrolytes, such as membranes for fuel cells, catalyst binder polymers for fuel cells, and membranes for chlor-alkali electrolysis. A process for producing a sulfonic acid group-containing monomer represented by the general formula (3) includes the step of mixing and stirring a cyclic compound represented by the general formula (1) and a silanol compound represented by the general formula (2).
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- Ligand-Controlled Regiodivergent Silylation of Allylic Alcohols by Ni/Cu Catalysis for the Synthesis of Functionalized Allylsilanes
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The first Ni/Cu-catalyzed regiodivergent synthesis of allylsilanes directly from allylic alcohols through modulating the steric and electronic properties of the ligands on the nickel catalyst has been developed. Good yields and excellent selectivity were obtained regardless of whether linear or α-branched allylic alcohols were utilized. Mechanistic studies indicate that an allyloxyboronate species is formed during the reaction, which likely serves as an activated intermediate toward the oxidative addition of the C(allyl)-O bond.
- Gan, Yi,Xu, Wei,Liu, Yuanhong
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supporting information
p. 9652 - 9657
(2019/11/28)
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- Axially Chiral, Electrophilic Fluorophosphonium Cations: Synthesis, Lewis Acidity, and Reactivity in the Hydrosilylation of Ketones
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Axially chiral [(C6F5)3PF][B(C6F5)4] analogues based on dihydrophosphepines with a binaphthyl backbone were prepared and structurally characterized by X-ray diffraction analysis. Computational calculations of FIA and GEI values attest that these new fluorophosphonium cations have a higher Lewis acidity compared to the ubiquitous B(C6F5)3. Furthermore, application of these highly electrophilic compounds in the catalytic hydrosilylation of ketones and an investigation of the mechanism lead to a refined picture of the role of highly electrophilic fluorophosphonium cations.
- Süsse, Lars,Lafortune, James H. W.,Stephan, Douglas W.,Oestreich, Martin
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supporting information
p. 712 - 721
(2019/02/17)
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- Catalytic Hydrodefluorination of C?F Bonds by an Air-Stable PIII Lewis Acid
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Catalytic hydrodefluorination (HDF) of unactivated fluoroalkanes or CF3-substituted aryl species is performed using the PIII Lewis acids, [(bipy)PPh]2+ (12+) and [(terpy)PPh]2+ (22+) under
- Chitnis, Saurabh S.,Krischer, Felix,Stephan, Douglas W.
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p. 6543 - 6546
(2018/04/26)
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- Metal-free pincer ligand chemistry polycationic phosphonium Lewis acids
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Oxidation of 2,6-bis(diphenylphosphine)methyl pyridine with MeO3SCF3, yields the dication [2,6-(CH2PMePh2)2C5H3N][CF3SO3]22, while subsequent treatment with two equivalents of [K(THF)n][B(C6F5)4] (n = 1.3-1.5) afforded [2,6-(CH2PMePh2)2C5H3N][B(C6F5)4]23. Analogous treatment using XeF2 afforded 2,6-(CH2PF2Ph2)2C5H3N 4, while subsequent fluoride abstractions afford the corresponding [BF4], [CF3SO3] and [B(C6F5)4] salts, 5-7, respectively. Compound 4 reacts with an excess of MeO3SCF3 to give [2,6-(CH2PF2Ph2)2C5H3N(CH3)][CF3SO3] 8 while subsequent reaction with [Et3Si·2C7H8][B(C6F5)4] gave the related tricationic species, 9. The Lewis acidity of these di- and triphosphonium cations 3, 7 and 9 was examined and their utility as Lewis acid catalysts was assessed in the dimerization of 1,1-diphenylethylene, the hydrodefluorination of 1-fluoroadamantane, and the dehydrocoupling of phenol and silane.
- Szkop, Kevin M.,Stephan, Douglas W.
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supporting information
p. 3921 - 3928
(2017/03/27)
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- Catalytic reduction of CO2with organo-silanes using [Ru3(CO)12]
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The reaction of carbon dioxide with Et3SiH in the presence of catalytic amounts of [Ru3(CO)12] as a catalytic precursor was achieved to produce silyl formate (Et3SiOCOH) 1s with a TON of 9000. A similar reaction in the presence of KF yielded potassium formate (8s) in a one-pot protocol with high selectivity using water or MeCN as the solvent. In the current report the complete reduction of carbon dioxide to methane was achieved, with the use of a more reactive silane (phenylsilane). A catalytically relevant species was the ruthenium cluster [H4Ru4(CO)12]. This is the second report on the hydrosilylation of carbon dioxide catalyzed by highly active and readily available ruthenium clusters and this is the first report of hydrosilylation of CO2to methane.
- Jurado-Vázquez, Tamara,Ortiz-Cervantes, Carmen,García, Juventino J.
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- Aryl(triethyl)silanes for Biaryl and Teraryl Synthesis by Copper(II)-Catalyzed Cross-Coupling Reaction
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Aryl(triethyl)silanes are found to undergo cross-coupling with iodoarenes in the presence of catalytic amounts of CuBr2and Ph-Davephos, as well as cesium fluoride as a stoichiometric base. Because the silicon reagents are readily accessible through catalytic C?H silylation of aromatic substrates, the net transformation allows coupling of aromatic hydrocarbons with iodoarenes via triethylsilylation.
- Komiyama, Takeshi,Minami, Yasunori,Hiyama, Tamejiro
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supporting information
p. 15787 - 15791
(2016/12/16)
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- Evidence of a Donor-Acceptor (Ir-H)→SiR3 Interaction in a Trapped Ir(III) Silane Catalytic Intermediate
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The ionic iridacycle [(2-phenylenepyridine-κN,κC)IrCp?(NCMe)][BArF24] ([2][BArF24]) displays a remarkable capability to catalyze the O-dehydrosilylation of alcohols at room temperature (0.4 × 103 3, 8 × 103 i 5 h-1 for primary alcohols) that is explained by its exothermic reaction with Et3SiH, which affords the new cationic hydrido-Ir(III)-silylium species [3][BArF24]. Isothermal calorimetric titration (ITC) indicates that the reaction of [2][BArF24] with Et3SiH requires 3 equiv of the latter and releases an enthalpy of -46 kcal/mol in chlorobenzene. Density functional theory (DFT) calculations indicate that the thermochemistry of this reaction is largely dominated by the concomitant bis-hydrosilylation of the released MeCN ligand. Attempts to produce [3][BF4] and [3][OTf] salts resulted in the formation of a known neutral hydrido-iridium(III) complex, i.e. 4, and the release of Et3SiF and Et3SiOTf, respectively. In both cases formation of the cationic μ-hydrido-bridged bis-iridacyclic complexes [5][BF4] and [5][OTf], respectively, was observed. The structure of [5][OTf] was established by X-ray diffraction analysis. Conversion of [3][BArF24] into 4 upon reaction with either 4-N,N-dimethylaminopyridine or [nBu4][OTf] indicates that the Ir center holds a +III formal oxidation state and that the Et3Si+ moiety behaves as a Z-type ligand according to Green's formalism. [3][BArF24], which was trapped and structurally characterized and its electronic structure investigated by state-of-the-art DFT methods (DFT-D, EDA, ETS-NOCV, QTAIM, ELF, NCI plots and NBO), displays the features of a cohesive hydridoiridium(III)→silylium donor-acceptor complex. This study suggests that the fate of [3]+ in the O-dehydrosilylation of alcohols is conditioned by the nature of the associated counteranion and by the absence of Lewis base in the medium capable of irreversibly capturing the silylium species.
- Hamdaoui, Mustapha,Ney, Marjolaine,Sarda, Vivien,Karmazin, Lydia,Bailly, Corinne,Sieffert, Nicolas,Dohm, Sebastian,Hansen, Andreas,Grimme, Stefan,Djukic, Jean-Pierre
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p. 2207 - 2223
(2016/07/21)
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- Stoichiometric and catalytic C-F bond activation by the trans-dihydride NHC complex [Ru(IEt2Me2)2-(PPh3)2H2] (IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)
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The room temperature reaction of C6F6 or C6F5H with [Ru(IEt2Me2)2(PPh3)2H2] (1; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) generated a mixture of the trans-hydride fluoride complex [Ru(IEt2Me2)2(PPh3)2HF] (2) and the bis-carbene pentafluorophenyl species [Ru(IEt2Me2)2(PPh3)(C6F5)H] (3). The formation of 3 resulted from C-H activation of C6F5H (formed from C6F6via stoichiometric hydrodefluorination), a process which could be reversed by working under 4 atm H2. Upon heating 1 with C6F5H, the bis-phosphine derivative [Ru(IEt2Me2)(PPh3)2(C6F5)H] (4) was isolated. A more efficient route to 2 involved treatment of 1 with 0.33 eq. of TREAT-HF (Et3N·3HF); excess reagent gave instead the [H2F3]- salt (5) of the known cation [Ru(IEt2Me2)2(PPh3)2H]+. Under catalytic conditions, 1 proved to be an active precursor for hydrodefluorination, converting C6F6 to a mixture of tri, di and monofluorobenzenes (TON = 37) at 363 K with 10 mol% 1 and Et3SiH as the reductant.
- Cybulski, Mateusz K.,Riddlestone, Ian M.,Mahon, Mary F.,Woodman, Timothy J.,Whittlesey, Michael K.
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p. 19597 - 19605
(2015/11/27)
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- The highly lewis acidic dicationic phosphonium salt: [(SIMes)PFPh 2][B(C6F5)4]2
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The dicationic imidazolium-phosphonium salt [(SIMes)PFPh 2][B(C6F5)4]2 has been prepared and shown to exhibit remarkable Lewis acidity in stoichiometric reactions and acting as an effective Lewis acid catalyst for the hydrodefluorination of fluoroalkanes and the hydrosilylation of olefins.
- Holthausen, Michael H.,Mehta, Meera,Stephan, Douglas W.
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supporting information
p. 6538 - 6541
(2014/06/24)
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- S-F and S-C activation of SF6 and SF5 derivatives at rhodium: Conversion of SF6 into H2S
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The degradation of SF6 and SF5 organyls by S-F and S-C bond-activation reactions at [{Rh(μ-H)(dippp)}2] under mild conditions is reported. Fluorido and thiolato species were identified as products or intermediates, and were characterized by X-ray diffraction analysis and multinuclear NMR spectroscopy. An unprecedented cyclic process for the conversion of the potent greenhouse gas SF6 into H2S was developed. Activation of the stable greenhouse gas SF6: The rhodium hydrido complex [{Rh(μ-H)(dippp)}2] effected defluorination at the sulfur atom of SF6 and organic SF5 compounds under mild conditions. The reduction of SF6 in the presence of HSiEt3 led exclusively to the thiolato complex [Rh2(μ-H)(μ-SSiEt 3)(dippp)2] and FSiEt3 (see Scheme). A cyclic process was developed for the conversion of SF6 into H2S.
- Zamostna, Lada,Braun, Thomas,Braun, Beatrice
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supporting information
p. 2745 - 2749
(2014/03/21)
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- Nickel-catalyzed hydrosilylation of CO2 in the Presence of Et3B for the synthesis of formic acid and related formates
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The reaction of CO2 with Et3SiH catalyzed by the nickel complex [(dippe)Ni(μ-H)]2 (1) afforded the reduction products Et3SiOCH2OSiEt3 (12%), Et 3SiOCH3 (3%), and CO, which were characterized by standard spectroscopic methods. Part of the generated CO was found as the complex [(dippe)Ni(CO)]2 (2), which was characterized by single-crystal X-ray diffraction. When the same reaction was carried out in the presence of a Lewis acid, such as Et3B, the hydrosilylation of CO2 efficiently proceeded to give the silyl formate (Et3SiOC(O)H) in high yields (85-89%), at 80 C for 1 h. Further reactivity of the silyl formate to yield formic acid, formamides, and alkyl formates was also investigated.
- Gonzalez-Sebastian, Lucero,Flores-Alamo, Marcos,Garcia, Juventino J.
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p. 7186 - 7194
(2014/01/06)
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- C6F5XeY Molecules (Y = F and Cl): New synthetic approaches. first structural proof of the organoxenon halide molecule C 6F5XeF
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The arylxenonium salt [C6F5Xe][BF4] reacts with different sources of nucleophiles, Y (naked fluoride, [N(CH 3)4]F, the silanes, (CH3)3SiCl and (C2H5)3SiH, and the cadmiumorganyl, Cd(C 6F5)2), in coordinating solvents (C 2H5CN, CH3CN, CD3CN). While the products C6F5XeF, C6F5XeCl, and (C6F5)2Xe are well defined molecules, in reactions with (C2H5)3SiH only decomposition products presumably derived from 6F5XeH6F5XeC2H56F5XeF are discussed.
- Bilir, Vural,Frohn, Hermann-Josef
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p. 505 - 512
(2013/09/23)
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- Catalytic hydrodefluorination of fluoroaromatics with silanes as hydrogen source at a binuclear rhodium complex: Characterization of key intermediates
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Stoichiometric and catalytic hydrodefluorination reactions of fluorinated aromatic substrates on using [Rh(μ-H)(dippp)]2 (1) (dippp = 1,3-bis(diisopropylphosphino)propane) as catalyst and HSiEt3 as a hydrogen source are reported. Treatment of the hydrido complex 1 with the fluoroarenes gave the fluorido complex [Rh(μ-F)(dippp)]2 (2) and organic hydrodefluorination products. An unusual ortho-selectivity was observed in the reaction of 2,3,5,6-tetrafluoropyridine and pentafluorobenzene giving the 1,2-hydrodefluorinated products. The binuclear structure of complex 2 in the solid state was confirmed by X-ray diffraction. The fluorido complex 2 reacted with HSiEt3 and HSiiPr3 by elimination of the corresponding fluorosilanes to afford the η2-silane hydrido complexes [Rh(H)(η2-HSiEt3)(dippp)] (3) and [Rh(H)(η2-HSiiPr3)(dippp)] (4), respectively. The structures of the complexes 3 and 4 were derived from NMR data and DFT calculations. Catalytic reactions of pentafluoropyridine, 2,3,5,6-tetrafluoro- pyridine or 2,3,5,6-tetra-fluoropyridine, hexa- and pentafluorobenzene with HSiEt3 in the presence of 5 mol% of 1 afforded hydrodefluorination products with up to 19 turnovers after 48 h at 50 C. In contrast to the stoichiometric reactions, the catalytic transformations resulted predominantly in hydrodefluorinations at the para-position of the nitrogen atom in the heterocycles giving evidence for two different C-F activation pathways. Compound 3 can be considered to be an intermediate in the catalytic hydrodefluorinations of the fluoroarenes.
- Zámostná, Lada,Ahrens, Mike,Braun, Thomas
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p. 132 - 142
(2013/10/01)
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- Catalytic hydrodefluorination of fluoromethanes at room temperature by silylium-ion-like surface species
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'Al'l about F: Aluminum chlorofluoride (ACF) catalyzes the hydrodefluorination, as well as Friedel-Crafts reactions of fluorinated methanes in the presence of Et3SiH. A surface-bound silylium-ion-like species is considered to be a crucial intermediate in achieving the C-F bond cleavage. Copyright
- Ahrens, Mike,Scholz, Gudrun,Braun, Thomas,Kemnitz, Erhard
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supporting information
p. 5328 - 5332
(2013/06/27)
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- π-π Interaction assisted hydrodefluorination of perfluoroarenes by gold hydride: A case of synergistic effect on C-F bond activation
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Synergistic effect is prevalent in natural metalloenzymes in activating small molecules, and the success has inspired the development of artificial catalysts capable of unprecedented organic transformations. In this work, we found that the attractive π-π interaction between organic additives (as electron-donors) and the perfluorinated arenes (as electron acceptors) is effective in gold hydride catalyzed activation of C-F bonds, specifically hydrodefluorination (HDF) of perfluoroarenes catalyzed by the Sadighi's gold hydrides [(NHC)AuH] (NHC = N-heterocyclic carbene). Although a weak interaction between [(NHC)AuH] and perfluoroarenes was observed from 1H NMR and UV-vis spectroscopies, low reactivity of [(NHC)AuH] toward HDF was found. In contrast, in the presence of p-N,N-dimethylaminopyridine (DMAP), the HDF of perfluoroarenes with silanes can be efficiently catalyzed by [(NHC)AuH], resulting in mainly the para-hydrodefluorinated products with up to 90% yield and 9 turnovers. The yield of the reaction increases with the more electron-withdrawing groups and degree of fluorination on the arenes, and the HDF reaction also tolerates different function groups (such as formyl, alkynyl, ketone, ester, and carboxylate groups), without reduction or hydrogenation of these function groups. To reveal the role of DMAP in the reactions, the possible π-π interaction between DMAP and perfluoroarenes was suggested by UV-vis spectral titrations, 1H NMR spectroscopic studies, and DFT calculations. Moreover, 1H and 19F-NMR studies show that this π-π interaction promotes hydrogen transfer from [(NHC)AuH] to pyridyl N atom, resulting in C-F bond cleavage. The interpretation of π-π interaction assisted C-F activation is supported by the reduced activation barriers in the presence of DMAP (31.6 kcal/mol) than that in the absence of DMAP (40.8 kcal/mol) for this reaction. An analysis of the charge distribution and transition state geometries indicate that this HDF process is controlled by the π-π interaction between DMAP and perfluoroarenes, accompanied with the changes of partial atomic charges.
- Lv, Hongbin,Zhan, Jin-Hui,Cai, Yuan-Bo,Yu, Yi,Wang, Bingwu,Zhang, Jun-Long
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supporting information
p. 16216 - 16227,12
(2020/09/09)
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- Exhaustive chlorination of [B12H12]2- without chlorine gas and the use of [B12Cl12]2- as a supporting anion in catalytic hydrodefluorination of aliphatic C-F bonds
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The fully chlorinated closo-dodecaborate salt Cs2[B 12Cl12] was prepared in high yield from Cs 2[B12H12] and SO2Cl2 in acetonitrile at refluxing temperature. [Ph3C]2[B 12Cl12] was obtained by simple metathesis reactions. Catalytic hydrodefluorination of benzotrifluoride sp3 C-F bonds was accomplished using [Ph3C]2[B12Cl12] as a precatalyst and Et3SiH as a stoichiometric reagent. Full consumption of the sp3 C-F bonds in p-FC6H 4CF3 and C6F5CF3 with a turnover number up to 2000 was achieved.
- Gu, Weixing,Ozerov, Oleg V.
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scheme or table
p. 2726 - 2728
(2011/05/14)
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- Borenium cations derived from BODIPY dyes
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Fluoride abstraction from a BODIPY dye gives a well defined borenium ion which can be converted to a borenium hydride via treatment with DIBAL-H. The Royal Society of Chemistry.
- Bonnier, Catherine,Piers, Warren E.,Parvez, Masood,Sorensen, Ted S.
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supporting information; experimental part
p. 4593 - 4595
(2009/03/11)
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- The Reaction of 2-X-1,2-Difluoroalk-1-enyldifluoroboranes with Xenon Difluoride. A Methodical Approach to 1,2-Difluoroalk-1-enylxenon(II) Salts
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2-X-1,2-Difluoroalk-1-enylxenon(II) salts were prepared by the reaction of XeF2 with XCF=CFBF2 (X = F, trans-H, cis-Cl, trans-Cl, cis-CF3, cis-C2F5) but no organoxenon(II) compounds were obtained when the trans-isomers of boranes, trans-XCF=CFBF 2 (X = CF3, C4F9, C 4H9, Et3Si), were used under similar conditions.
- Frohn, Hermann-Josef,Adonin, Nicolay Yu.,Bardin, Vadim V.
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p. 2499 - 2508
(2008/10/09)
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- Oxidative fluorination of S, Se and Te compounds
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The synthesis and mechanism of formation of cis- and trans-Ph2SF4 is described. Starting compounds are Ph2S or Ph2SF2 and the oxidizing agent is XeF2 in the presence of Et4NCl. Also described is the synthesis of related chalcogen(IV and VI) fluorides such as t-butylSF3, difluorodibenzothiophene, PhSeF3, Ph2SeF2, PhSF5, p-MeC6H4SF5, PhSeF5, and PhTeF5. The reactions of Ph2S(O)F2 with alcohols and with the H2O-HF-glass system are briefly described.
- Ou, Xiaobo,Janzen, Alexander F.
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p. 279 - 283
(2007/10/03)
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- Stereoselective preparation of (Z)-α,β-difluorostyrenes
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Substituted aromatic iodides couple with (E)-HFC = CFZnI, under mild conditions, in the presence of catalytic Pd(PPh3)4 in DMF to give the title compounds in good yield.
- Davis, Charles R.,Burton, Donald J.
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p. 7237 - 7240
(2007/10/03)
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- The covalent nature of trimethylsilyl perchlorate and observation of polarized fluorotrimethylsilane-antimony pentafluoride complexes based on29Si NMR studies. Difficulties in observing long-lived persistent trialkylsilicenium ions
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Trimethylsilyl perchlorate was studied in sulfolane solution by 29Si NMR spectroscopy. The 29Si NMR shift of δ(29Si) 47 remained virtually unchanged by changing the concentrations from 0.584, to 0.29, to 0.15 M. This indicates that (CH3)3SiOClO3 is covalent throughout this concentration range in contrast to the claims by Lambert et al. (J. Am. Chem. Soc. 1988, 110, 6364), who based on 35Cl and 37Cl NMR data suggested an equilibrium of the ionic and covalent forms, with 20, 29, and 35% ionic contribution, respectively, at these concentrations. If such an equilibrium would exist, the 29Si NMR shifts should display significant deshieldings. Upon further dilution in the 0.1 to 0.002 M range the formation of hexamethyldisiloxane was observed, even in highly purified sulfolane, indicative of hydrolysis by residual low-level water impurity. Simultaneously formed perchloric acid which undergoes perchlorate ion exchange with the unhydrolyzed trimethylsilyl perchlorate would seem to explain the reported 35Cl/37Cl NMR behavior, as well as cryoscopic and conductivity data. An investigation of fluorotrialkylsilanes in SbF5-SO2CIF solution at -78 °C by 13C and 29Si NMR spectroscopy showed highly polarized, rapidly exchanging complexes, but no free silicenium ions. The reasons for the inability of observing persistent silicenium ions in the condensed state, despite claims to the contrary, are discussed.
- Olah, George A.,Heiliger, Ludger,Li, Xing-Ya,Surya Prakash
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p. 5991 - 5995
(2007/10/02)
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- METHYLAMMONIUM FLUORIDE (MAF): A CONVENIENT REAGENT FOR Si-O BOND CLEAVAGE
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Crude methylammonium fluoride prepared in a usual way is a very convenient reagent for Si-O bond cleavage.MAF is easy to prepare, easy to store and provides the desired deprotected alcohols without workup.
- Solladie-Cavallo, A.,Khiar, N.
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p. 1335 - 1340
(2007/10/02)
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- STEREOISOTOPIC STUDY OF THE REDUCTION OF 1-PHENYLETHANOL BY ETHERATED BORON TRIFLUORIDE-TRIETHYLSILANE SYSTEM
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The kinetic hydrogen-deuterium isotope effects and the stereochemistry of the deoxygenation of 1-phenylethanol with boron trifluoride and triethylsilane have been studied.The results are consistent with a mechanism that involves of the formation of the phenethyl cation in a rate determining step and its fast reduction with triethylsilane.
- Smonou, Ioulia,Orfanopoulos, Michael
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p. 5793 - 5796
(2007/10/02)
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- PRACTICAL SYNTHESIS AND POLYMERIZATION OF TRIFLUOROVINYLSILANES. A POSSIBLE PRECURSOR OF POLY(DIFLUOROACETYLENE)
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An improved procedure for the preparation of trifluorovinylsilanes was established which involved addition of butyllithium to a mixture of chlorosilanes and commercially readily available chlorotrifluoroethylene at -78 to -130 deg C, and the resulting monomer was polymerized with a catalyst such as CsF or (R2N)3S(1+)*F2SiMe3(1-) to give black metallic polymer which showed conductivity of 1E-9 to 1E-10 Ω-1cm-1.
- Hiyama, Tamejiro,Nishide, Kiyoharu,Obayashi, Michio
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p. 1765 - 1768
(2007/10/02)
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