- Accessing Two-Coordinate ZnII Organocations by NHC Coordination: Synthesis, Structure, and Use as π-Lewis Acids in Alkene, Alkyne, and CO2 Hydrosilylation
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Discrete two-coordinate ZnII organocations of the type (NHC)Zn?R+ are reported, thanks to NHC stabilization. In preliminary reactivity studies, such entities, which are direct cationic analogues of long-known ZnR2 species,
- Specklin, David,Hild, Frédéric,Fliedel, Christophe,Gourlaouen, Christophe,Veiros, Luis F.,Dagorne, Samuel
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- An efficient iridium catalyst for reduction of carbon dioxide to methane with trialkylsilanes
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Cationic silane complexes of general structure (POCOP)Ir(H)(HSiR 3) {POCOP = 2,6-[OP(tBu)2]2C6H 3} catalyze hydrosilylations of CO2. Using bulky silanes results in formation of bis(silyl)acetals and methyl silyl ethers as well as siloxanes and CH4. Using less bulky silanes such as Me 2EtSiH or Me2PhSiH results in rapid formation of CH 4 and siloxane with no detection of bis(silyl)acetal and methyl silyl ether intermediates. The catalyst system is long-lived, and 8300 turnovers can be achieved using Me2PhSiH with a 0.0077 mol % loading of iridium. The proposed mechanism for the conversion of CO2 to CH4 involves initial formation of the unobserved HCOOSiR3. This formate ester is then reduced sequentially to R3SiOCH2OSiR 3, then R3SiOCH3, and finally to R 3SiOSiR3 and CH4.
- Park, Sehoon,Bezier, David,Brookhart, Maurice
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- Chemoselective Deoxygenation of 2° Benzylic Alcohols through a Sequence of Formylation and B(C6F5)3-Catalyzed Reduction
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A sequence of formylation and B(C6F5)3-catalyzed reduction of the resulting formate with Et3SiH enables the chemoselective deoxygenation of secondary benzylic alcohols. Primary benzylic and tertiary non-benzylic alcohols are not reduced by this protocol. The formyl group fulfills a double role as activator and self-sacrificing protecting group. The deoxygenation of these formates is fast and can be carried out in the presence of other potentially reducible groups. Neighboring-group participation was found in the deoxygenation of certain diol motifs.
- Oestreich, Martin,Richter, Sven C.
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supporting information
p. 2103 - 2106
(2021/07/22)
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- Light-Promoted Transfer of an Iridium Hydride in Alkyl Ether Cleavage
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A catalytic, light-promoted hydrosilylative cleavage reaction of alkyl ethers is reported. Initial studies are consistent with a mechanism involving heterolytic silane activation followed by delivery of a photohydride equivalent to a silyloxonium ion generated in situ. The catalyst resting state is a mixture of Cp*Ir(ppy)H (ppy = 2-phenylpyridine-κC,N) and a related hydride-bridged dimer. Trends in selectivity in substrate reduction are consistent with nonradical mechanisms for C-O bond scission. Irradiation of Cp*Ir(ppy)H with blue light is found to increase the rate of hydride delivery to an oxonium ion in a stoichiometric test. A comparable rate enhancement is found in carbonyl hydrosilylation catalysis, which operates through a related mechanism also involving Cp*Ir(ppy)H as the resting state.
- Fast, Caleb D.,Schley, Nathan D.
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supporting information
p. 3291 - 3297
(2021/10/12)
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- Catalytic Disproportionation of Formic Acid to Methanol by using Recyclable Silylformates
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A novel strategy to prepare methanol from formic acid without an external reductant is presented. The overall process described herein consists of the disproportionation of silyl formates to methoxysilanes, catalyzed by ruthenium complexes, and the production of methanol by simple hydrolysis. Aqueous solutions of MeOH (>1 mL, >70 percent yield) were prepared in this manner. The sustainability of the reaction has been established by recycling of the silicon-containing by-products with inexpensive, readily available, and environmentally benign reagents.
- Cantat, Thibault,Chauvier, Clément,Imberdis, Arnaud,Thuéry, Pierre
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supporting information
p. 14019 - 14023
(2020/06/09)
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- Hydrogenation of silyl formates: sustainable production of silanol and methanol from hydrosilane and carbon dioxide
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A new process for simultaneously obtaining two chemical building blocks, methanol and silanol, was realized starting from silyl formates which can be derived from silane and carbon dioxide. Understanding the reaction mechanism enabled us to improve the reaction efficiency by the addition of a small amount of methanol.
- Koo, Jangwoo,Kim, Seung Hyo,Hong, Soon Hyeok
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p. 4995 - 4998
(2018/05/23)
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- Iron Catalyzed CO2 Activation with Organosilanes
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Abstract: Iron nanoparticles generated in situ from [Fe3(CO)12] catalyzed CO2 reduction in the presence of Et3SiH as a reductant and tetrabutylammonium fluoride as a promoter to yield silyl formate (1s) under relatively mild reaction conditions. Additionally, when CO2 hydrosilylation was carried out in water, the product of CO2 reduction was formic acid. Additionally, a similar reaction using [Fe3(CO)12] as a catalytic precursor, PhSiH3 as a reductant, and CO2 in the presence of amines allowed the immediate formation of ureas at room temperature. Here, CO2 acted as a C1 building block for value-added products.
- Jurado-Vázquez, Tamara,García, Juventino J.
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p. 1162 - 1168
(2018/02/22)
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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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- Aromaticity as stabilizing element in the bidentate activation for the catalytic reduction of carbon dioxide
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A new transition-metal-free mode for the catalytic reduction of carbon dioxide via bidentate interaction has been developed. In the presence of Li2[1,2-C6H4(BH3)2], CO2 can be selectively transformed to either methane or methanol, depending on the reducing agent. The bidentate nature of binding is supported by X-ray analysis of an intermediate analogue, which experiences special stabilization due to aromatic character in the bidentate interaction. Kinetic studies revealed a first-order reaction rate. The transformation can be conducted without any solvent.
- Lu, Zhenpin,Hausmann, Heike,Becker, Sabine,Wegner, Hermann A.
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supporting information
p. 5332 - 5335
(2015/05/13)
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- Deoxygenative reduction of carbon dioxide to methane, toluene, and diphenylmethane with [Et2Al]+ as catalyst
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The strong Lewis acid [Et2Al]+ catalyzes the reduction of carbon dioxide with hydrosilanes under mild conditions to methane. In benzene solution, the side products toluene and diphenylmethane are also obtained through Lewis acid catalyzed benzene alkylation by reaction intermediates. Copyright
- Khandelwal, Manish,Wehmschulte, Rudolf J.
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supporting information; experimental part
p. 7323 - 7326
(2012/09/08)
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