- 14-Electron Rh and Ir silylphosphine complexes and their catalytic activity in alkene functionalization with hydrosilanes
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Herein we report an experimental and computational study of a family of four coordinated 14-electron complexes of Rh(iii) devoid of agostic interactions. The complexes [X-Rh(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)2], where X = Cl (Rh-1), Br (Rh-2), I (Rh-3), OTf (Rh-4), Cl·GaCl3(Rh-5); derive from a bis(silyl)-o-tolylphosphine with isopropyl substituents on the Si atoms. All five complexes display a sawhorse geometry around Rh and exhibit similar spectroscopic and structural properties. The catalytic activity of these complexes and [Cl-Ir(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)2],Ir-1, in styrene and aliphatic alkene functionalizations with hydrosilanes is disclosed. We show thatRh-1catalyzes effectively the dehydrogenative silylation of styrene with Et3SiH in toluene while it leads to hydrosilylation products in acetonitrile.Rh-1is an excellent catalyst in the sequential isomerization/hydrosilylation of terminal and remote aliphatic alkenes with Et3SiH including hexene isomers, leading efficiently and selectively to the terminal anti-Markonikov hydrosilylation product in all cases. With aliphatic alkenes, no hydrogenation products are observed. Conversely, catalysis of the same hexene isomers byIr-1renders allyl silanes, the tandem isomerization/dehydrogenative silylation products. A mechanistic proposal is made to explain the catalysis with these M(iii) complexes.
- Abeynayake, Niroshani S.,Donnadieu, Bruno,Gorla, Saidulu,Montiel-Palma, Virginia,Mu?oz-Hernández, Miguel A.,Zamora-Moreno, Julio
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supporting information
p. 11783 - 11792
(2021/09/06)
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- A family of rhodium(i) NHC chelates featuring O-containing tethers for catalytic tandem alkene isomerization-hydrosilylation
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The rhodium complex Rh(HL)(COD)Cl, 1, L being a functionalized N-heterocyclic carbene (NHC) ligand with an oxygen-containing pendant arm, has been used as the entry point to synthesize a series of neutral and cationic Rh(i) O,C chelates. While the Rh-carbene interaction is similar in all these 16-electron complexes, structural analysis reveals that the strength of the Rh-O bond is greatly affected by the nature of the O-donor: R-O- > R-OH > R-OBF3. These subtle changes in the nature of the O-containing tether are found to be responsible for large differences in the alkene hydrosilylation catalytic activity of these compounds: the stronger the Rh-O interaction, the better the catalytic performances. The most active catalyst, [Rh(L)(COD)], 2, demonstrated good catalytic activity under mild reaction conditions for the hydrosilylation of a range of alkene substrates with the industrially relevant non-activated tertiary silane, 1,1,1,3,5,5,5-heptamethyltrisiloxane (MDHM). Furthermore, this complex is an effective catalyst for the selective remote functionalization of internal olefins at room temperature via tandem alkene isomerization-hydrosilylation.
- Srivastava, Ravi,Jakoobi, Martin,Thieuleux, Chloé,Quadrelli, Elsje Alessandra,Camp, Clément
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p. 869 - 879
(2021/02/03)
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- Silicon(II) Cation Cp*Si:+ X-: A New Class of Efficient Catalysts in Organosilicon Chemistry
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The catalytic activity of the pentamethylcyclopentadienylsilicon(II) cation Cp*Si:+ was investigated. It was shown that Cp*Si:+ efficiently catalyzes reactions of technical relevance in organosilicon chemistry: Cp*Si:+ proved to be a very efficient nonmetallic catalyst for the hydrosilylation of olefins at low catalyst amounts of 0.01 mol % and for the Piers-Rubinsztajn reaction in order to make controlled silicone topologies. The thermal induction of hydrosilylation which is important for the manufacturing of silicone rubber can be achieved by small amounts of alkoxysilanes.
- Fritz-Langhals, Elke
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p. 2369 - 2377
(2019/10/28)
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- Thermal, Catalytic Conversion of Alkanes to Linear Aldehydes and Linear Amines
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Alkanes, the main constituents of petroleum, are attractive feedstocks for producing value-added chemicals. Linear aldehydes and amines are two of the most important building blocks in the chemical industry. To date, there have been no effective methods for directly converting n-alkanes to linear aldehydes and linear amines. Here, we report a molecular dual-catalyst system for production of linear aldehydes via regioselective carbonylation of n-alkanes. The system is comprised of a pincer iridium catalyst for transfer-dehydrogenation of the alkane using t-butylethylene or ethylene as a hydrogen acceptor working sequentially with a rhodium catalyst for olefin isomerization-hydroformylation with syngas. The system exhibits high regioselectivity for linear aldehydes and gives high catalytic turnover numbers when using ethylene as the acceptor. In addition, the direct conversion of light alkanes, n-pentane and n-hexane, to siloxy-terminated alkyl aldehydes through a sequence of Ir/Fe-catalyzed alkane silylation and Ir/Rh-catalyzed alkane carbonylation, is described. Finally, the Ir/Rh dual-catalyst strategy has been successfully applied to regioselective alkane aminomethylation to form linear alkyl amines.
- Tang, Xinxin,Jia, Xiangqing,Huang, Zheng
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supporting information
p. 4157 - 4163
(2018/03/29)
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- Tuning the redox non-innocence of a phenalenyl ligand toward efficient nickel-assisted catalytic hydrosilylation
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In this report, a ligand-redox assisted catalytic hydrosilylation has been investigated. A phenalenyl ligand coordinated nickel complex has been utilized as an electron reservoir to develop a base metal-assisted catalyst, which very efficiently hydrosilylates a wide variety of olefin substrates under ambient conditions. A mechanistic investigation revealed that a two-electron reduced phenalenyl based biradical nickel complex plays the key role in such catalysis. The electronic structure of the catalytically active biradical species has been interrogated using EPR spectroscopy, magnetic susceptibility measurements, and electronic structure calculations using a DFT method. Inhibition of the reaction by a radical quencher, as well as the mass spectrometric detection of two intermediates along the catalytic loop, suggest that a single electron transfer from the ligand backbone initiates the catalysis. The strategy of utilising the redox reservoir property of the ligand ensures that the nickel is not promoted to an unfavorable oxidation state, and the fine tuning between the ligand and metal redox orbitals elicits smooth catalysis.
- Vijaykumar, Gonela,Pariyar, Anand,Ahmed, Jasimuddin,Shaw, Bikash Kumar,Adhikari, Debashis,Mandal, Swadhin K.
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p. 2817 - 2825
(2018/03/21)
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- A Pt(0) complex with cyclic (alkyl)(amino)silylene and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane ligands: Synthesis, molecular structure, and catalytic hydrosilylation activity
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A platinum(0) complex bearing a cyclic (alkyl)(amino)silylene and a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS) was synthesized and isolated in the form of colorless crystals. The single-crystal X-ray diffraction analysis of this complex in combination with theoretical calculations indicated that the Pt→Si π-back-donation in this complex is weaker than that in the corresponding cyclic-dialkylsilylene-ligated Pt complex. The performance of this complex in the catalytic hydrosilylation of (Me3SiO)2MeSi-H with various terminal alkenes that contain functional groups was comparable to that of the corresponding cyclic dialkylsilylene/DVTMS Pt(0) complex.
- Iimura, Tomohiro,Akasaka, Naohiko,Kosai, Tomoyuki,Iwamoto, Takeaki
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p. 8868 - 8874
(2017/07/22)
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- Conversion of alkanes to linear alkylsilanes using an iridium-iron-catalysed tandem dehydrogenation-isomerization-hydrosilylation
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The conversion of inexpensive, saturated hydrocarbon feedstocks into value-added speciality chemicals using regiospecific, catalytic functionalization of alkanes is a major goal of organometallic chemistry. Linear alkylsilanes represent one such speciality chemical - they have a wide range of applications, including release coatings, silicone rubbers and moulding products. Direct, selective, functionalization of alkanes at primary C-H bonds is difficult and, to date, methods for catalytically converting alkanes into linear alkylsilanes are unknown. Here, we report a well-defined, dual-catalyst system for one-pot, two-step alkane silylations. The system comprises a pincer-ligated Ir catalyst for alkane dehydrogenation and an Fe catalyst that effects a subsequent tandem olefin isomerization-hydrosilylation. This method exhibits exclusive regioselectivity for the production of terminally functionalized alkylsilanes. This dual-catalyst strategy has also been applied to regioselective alkane borylations to form linear alkylboronate esters.
- Jia, Xiangqing,Huang, Zheng
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p. 157 - 161
(2016/02/03)
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- Iron-catalysed chemo-, regio-, and stereoselective hydrosilylation of alkenes and alkynes using a bench-stable iron(II) pre-catalyst
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The chemo-, regio-, and stereoselective iron-catalysed hydrosilylation of alkenes and alkynes with excellent functional group tolerance is reported (34 examples, 41-96% yield). The catalyst and reagents are commercially available and easy to handle, with the active iron catalyst being generated in situ, thus providing a simple and practical methodology for iron-catalysed hydrosilylation. The silane products can be oxidised to the anti-Markovnikov product of olefin hydration, and the one-pot iron-catalysed hydrosilylation-oxidation of olefins to give silane(di)ols directly is also reported. The iron pre-catalyst was used at loadings as low as 0.07 mol%, and displayed catalyst turnover frequencies (TOF) approaching 60,000 molh-1. Initial mechanistic studies indicate an iron(I) active catalyst.
- Greenhalgh, Mark D.,Frank, Dominik J.,Thomas, Stephen P.
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supporting information
p. 584 - 590
(2014/05/20)
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- HYDROSILYLATION REACTION CURABLE COMPOSITIONS AND METHODS FOR THEIR PREPARATION AND USE
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A composition contains (A) a hydrosilylation reaction catalyst and (B) an aliphatically unsaturated compound having an average, per molecule, of one or more aliphatically unsaturated organic groups capable of undergoing hydrosilylation reaction. The composition is capable of reacting via hydrosilylation reaction to form a reaction product, such as a silane, a gum, a gel, a rubber, or a resin. Ingredient (A) contains a platinum-ligand complex that can be prepared by reacting a platinum precursor and a ligand.
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Page/Page column 43; 44
(2013/03/26)
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- SILVER CONTAINING HYDROSILYLATION CATALYSTS AND COMPOSITIONS CONTAINING THE CATALYSTS
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A composition contains (A) a hydrosilylation reaction catalyst and (B) an aliphatically unsaturated compound having an average, per molecule, of one or more aliphatically unsaturated organic groups capable of undergoing hydrosilylation reaction. The composition ' capable of reacting via hydrosilylation reaction to form a reaction product, such as a silane, a gum, a gel, a rubber, or a resin. Ingredient (A) contains a metal-ligand complex that can be prepared by a method including reacting a metal precursor and a ligand.
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Paragraph 0232
(2013/04/10)
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