4730-22-7Relevant academic research and scientific papers
Tuning Nano-Nickel Catalyst Hydrogenation Aptitude by On-the-Fly Zirconium Doping
Zienkiewicz-Machnik, Ma?gorzata,Goszewska, Ilona,Giziński, Damian,?r?bowata, Anna,Kuzmowicz, Katarzyna,Kubas, Adam,Matus, Krzysztof,Lisovytskiy, Dmytro,Pisarek, Marcin,Jacinto
, p. 3132 - 3138 (2020)
The effect of nano-Ni catalyst post-synthetic Zr-modification on hydrogenation reaction of 6-methyl-5-hepten-2-one was investigated in a fixed bed continuous-flow micro-reactor to produce fine chemicals. The catalytic performance revealed that Zr-doping achieved by surface organometallic chemistry approach modifies the natural aptitude of nickel to hydrogenate C=C bond, since the addition of small quantities of zirconium significantly increased the amount of unsaturated and saturated alcohols formed in 6-methyl-5-hepten-2-one hydrogenation. Quantum chemical calculations revealed a stronger interaction between Zr←O=C that promotes the formation of C=C semihydrogenation product and enhances the probability of complete hydrogenation. The on-the-fly strategy presented herein enables for rapid optimization and understanding of catalytic processes.
Base-free transfer hydrogenation of aryl-ketones, alkyl-ketones and alkenones catalyzed by an IrIIICp* complex bearing a triazenide ligand functionalized with pyrazole
Medrano-Castillo, Layla J.,Collazo-Flores, Miguel á.,Camarena-Díaz, Juan P.,Correa-Ayala, Erick,Chávez, Daniel,Grotjahn, Douglas B.,Rheingold, Arnold L.,Miranda-Soto, Valentín,Parra-Hake, Miguel
, (2020/03/13)
An IrIIICp* complex (2) bearing a triazenide ligand functionalized with pyrazole was synthesized and fully characterized by spectroscopic methods and the structure confirmed by X-ray diffraction studies. The catalytic activity of 2 and the control complex 3, which lacks of pyrazole in its structure, was evaluated in the reduction of aryl-ketones, alkyl-ketones, α,β-unsaturated and γ,δ-unsaturated ketones. The catalytic system, using either 2 or 3, exhibited good to excellent selectivity when tested with ketones and alkenones at 90 °C in 2-propanol as hydrogen source under base-free conditions. Reactivity of 2 in 2-propanol and NaH gave a neutral metal hydride (4) while in the absence of base gave two major cationic hydrides species (5 and 6).
Rh(III)Cp? and Ir(III)Cp? Complexes of 1-[(4-Methyl)phenyl]-3-[(2-methyl-4′-R)imidazol-1-yl]triazenide (R = t-Bu or H): Synthesis, Structure, and Catalytic Activity
Camarena-Diáz, Juan P.,Iglesias, Ana L.,Chávez, Daniel,Aguirre, Gerardo,Grotjahn, Douglas B.,Rheingold, Arnold L.,Parra-Hake, Miguel,Miranda-Soto, Valentín
, p. 844 - 851 (2019/02/19)
A series of iridium and rhodium complexes have been synthesized using as ligand a triazenide monofunctionalized with an imidazole substituent. Steric hindrance at the imidazole moiety induced differences in the coordination modes as well in the catalytic behavior of complexes 4-7. Complexes 4-7 were tested in the transfer hydrogenation of acetophenone and 5-alken-2-ones. The hydrogenation of either the double bond or the carbonyl group in 5-alken-2-ones, showed to be selective in the presence of 6, 7, and 10 and has a dependence on the presence or absence of base. Control experiments point out that the imidazole moiety in the structure of complexes 4-7 speeds-up the catalysis.
Phosphonate-Mediated Immobilization of Rhodium/Bipyridine Hydrogenation Catalysts
Forato, Florian,Belhboub, Anouar,Monot, Julien,Petit, Marc,Benoit, Roland,Sarou-Kanian, Vincent,Fayon, Franck,Jacquemin, Denis,Queffelec, Clémence,Bujoli, Bruno
, p. 2457 - 2465 (2018/02/06)
RhL2 complexes of phosphonate-derivatized 2,2′-bipyridine (bpy) ligands L were immobilized on titanium oxide particles generated in situ. Depending on the structure of the bipy ligand—number of tethers (1 or 2) to which the phosphonate end groups are attached and their location on the 2,2′-bipyridine backbone (4,4′-, 5,5′-, or 6,6′-positions)—the resulting supported catalysts showed comparable chemoselectivity but different kinetics for the hydrogenation of 6-methyl-5-hepten-2-one under hydrogen pressure. Characterization of the six supported catalysts suggested that the intrinsic geometry of each of the phosphonate-derivatized 2,2′-bipyridines leads to supported catalysts with different microstructures and different arrangements of the RhL2 species at the surface of the solid, which thereby affect their reactivity.
STABILIZATION OF ACTIVE METAL CATALYSTS AT METAL-ORGANIC FRAMEWORK NODES FOR HIGHLY EFFICIENT ORGANIC TRANSFORMATIONS
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Paragraph 0338, (2019/01/07)
Metal-organic framework (MOFs) compositions based on post?synthetic metalation of secondary building unit (SBU) terminal or bridging OH or OH2 groups with metal precursors or other post-synthetic manipulations are described. The MOFs provide a versatile family of recyclable and reusable single-site solid catalysts for catalyzing a variety of asymmetric organic transformations, including the regioselective boryiation and siiylation of benzyiic C—H bonds, the hydrogenation of aikenes, imines, carbonyls, nitroarenes, and heterocycles, hydroboration, hydrophosphination, and cyclization reactions. The solid catalysts can also be integrated into a flow reactor or a supercritical fluid reactor.
Stable and Inert Cobalt Catalysts for Highly Selective and Practical Hydrogenation of C≡N and C=O Bonds
Chen, Feng,Topf, Christoph,Radnik, J?rg,Kreyenschulte, Carsten,Lund, Henrik,Schneider, Matthias,Surkus, Annette-Enrica,He, Lin,Junge, Kathrin,Beller, Matthias
supporting information, p. 8781 - 8788 (2016/08/02)
Novel heterogeneous cobalt-based catalysts have been prepared by pyrolysis of cobalt complexes with nitrogen ligands on different inorganic supports. The activity and selectivity of the resulting materials in the hydrogenation of nitriles and carbonyl compounds is strongly influenced by the modification of the support and the nitrogen-containing ligand. The optimal catalyst system ([Co(OAc)2/Phenα-Al2O3]-800 = Cat. E) allows for efficient reduction of both aromatic and aliphatic nitriles including industrially relevant dinitriles to primary amines under mild conditions. The generality and practicability of this system is further demonstrated in the hydrogenation of diverse aliphatic, aromatic, and heterocyclic ketones as well as aldehydes, which are readily reduced to the corresponding alcohols.
Ruthenium complexes bearing an unsymmetrical pincer ligand with a 2-hydroxypyridylmethylene fragment: Active catalysts for transfer hydrogenation of ketones
Shi, Jing,Hu, Bowen,Gong, Dawei,Shang, Shu,Hou, Guangfeng,Chen, Dafa
, p. 4828 - 4834 (2016/03/19)
Five ruthenium(ii) complexes were synthesized, including (HO-C5H3N-CH2-C5H3N-C5H4N)Ru(PPh3)Cl2 (3), [(HO-C5H3N-CH2-C5H3N-C5H4N)Ru(PPh3)2Cl][PF6] (4) and [(HO-C5H3N-CH2-C5H3N-C5H4N)Ru(PPh3)2OH][PF6] (5) bearing an unsymmetrical pincer NNN ligand with a 2-hydroxypyridylmethylene fragment, and [(CH3O-C5H3N-CH2-C5H3N-C5H4N)2Ru][Cl]2 (6) and [(CH3O-C5H3N-CH2-C5H3N-C5H4N)2Ru][PF6]2 (7) containing 2-methoxypyridylmethylene moieties. 4 reacts with H2O at room temperature to give 5 whose crystal structure reveals the existence of intramolecular hydrogen-bonding between its two -OH groups. 3 exhibits high catalytic activity for transfer hydrogenation of ketones.
Single-Site Cobalt Catalysts at New Zr8(μ2-O)8(μ2-OH)4 Metal-Organic Framework Nodes for Highly Active Hydrogenation of Alkenes, Imines, Carbonyls, and Heterocycles
Ji, Pengfei,Manna, Kuntal,Lin, Zekai,Urban, Ania,Greene, Francis X.,Lan, Guangxu,Lin, Wenbin
supporting information, p. 12234 - 12242 (2016/09/28)
We report here the synthesis of robust and porous metal-organic frameworks (MOFs), M-MTBC (M = Zr or Hf), constructed from the tetrahedral linker methane-tetrakis(p-biphenylcarboxylate) (MTBC) and two types of secondary building units (SBUs): cubic M8(μ2-O)8(μ2-OH)4 and octahedral M6(μ3-O)4(μ3-OH)4. While the M6-SBU is isostructural with the 12-connected octahedral SBUs of UiO-type MOFs, the M8-SBU is composed of eight MIV ions in a cubic fashion linked by eight μ2-oxo and four μ2-OH groups. The metalation of Zr-MTBC SBUs with CoCl2, followed by treatment with NaBEt3H, afforded highly active and reusable solid Zr-MTBC-CoH catalysts for the hydrogenation of alkenes, imines, carbonyls, and heterocycles. Zr-MTBC-CoH was impressively tolerant of a range of functional groups and displayed high activity in the hydrogenation of tri- and tetra-substituted alkenes with TON > 8000 for the hydrogenation of 2,3-dimethyl-2-butene. Our structural and spectroscopic studies show that site isolation of and open environments around the cobalt-hydride catalytic species at Zr8-SBUs are responsible for high catalytic activity in the hydrogenation of a wide range of challenging substrates. MOFs thus provide a novel platform for discovering and studying new single-site base-metal solid catalysts with enormous potential for sustainable chemical synthesis.
Chiral fluorinated α-sulfonyl carbanions: Enantioselective synthesis and electrophilic capture, racemization dynamics, and structure
Hellmann, Gunther,Hack, Achim,Thiemermann, Eric,Luche, Olaf,Raabe, Gerhard,Gais, Hans-Joachim
supporting information, p. 3869 - 3897 (2013/04/10)
Enantiomerically pure triflones R1CH(R2)SO 2CF3 have been synthesized starting from the corresponding chiral alcohols via thiols and trifluoromethylsulfanes. Key steps of the syntheses of the sulfanes are the photochemical trifluoromethylation of the thiols with CF3Hal (Hal=halide) or substitution of alkoxyphosphinediamines with CF3SSCF3. The deprotonation of RCH(Me)SO2CF3 (R=CH2Ph, iHex) with nBuLi with the formation of salts [RC(Me)-SO2CF3]Li and their electrophilic capture both occurred with high enantioselectivities. Displacement of the SO2CF3 group of (S)-MeOCH2C(Me)(CH 2Ph)SO2CF3 (95 % ee) by an ethyl group through the reaction with AlEt3 gave alkane MeOCH2C(Me)(CH 2Ph)Et of 96 % ee. Racemization of salts [R1C(R 2)SO2CF3]Li follows first-order kinetics and is mainly an enthalpic process with small negative activation entropy as revealed by polarimetry and dynamic NMR (DNMR) spectroscopy. This is in accordance with a Cα-S bond rotation as the rate-determining step. Lithium α-(S)-trifluoromethyl- and α-(S)-nonafluorobutylsulfonyl carbanion salts have a much higher racemization barrier than the corresponding α-(S)-tert-butylsulfonyl carbanion salts. Whereas [PhCH 2C(Me)SO2tBu]Li/DMPU (DMPU = dimethylpropylurea) has a half-life of racemization at -105 °C of 2.4 h, that of [PhCH 2C(Me)SO2CF3]Li at -78 °C is 30 d. DNMR spectroscopy of amides (PhCH2)2NSO2CF 3 and (PhCH2)N(Ph)SO2CF3 gave N-S rotational barriers that seem to be distinctly higher than those of nonfluorinated sulfonamides. NMR spectroscopy of [PhCH2C(Ph)SO 2R]M (M=Li, K, NBu4; R=CF3, tBu) shows for both salts a confinement of the negative charge mainly to the Cα atom and a significant benzylic stabilization that is weaker in the trifluoromethylsulfonyl carbanion. According to crystal structure analyses, the carbanions of salts {[PhCH2C(Ph)SO2CF3] Li×L}2 (L=2 THF, tetramethylethylenediamine (TMEDA)) and [PhCH2C(Ph)SO2CF3]NBu4 have the typical chiral Cα-S conformation of α-sulfonyl carbanions, planar Cα atoms, and short Cα-S bonds. Ab initio calculations of [MeC(Ph)SO2tBu]- and [MeC(Ph)SO2CF3]- showed for the fluorinated carbanion stronger nC→σ* S-CF 3 and n O→σ* S-CF 3 interactions and a weaker benzylic stabilization. According to natural bond orbital (NBO) calculations of [R 1C(R2)SO2R]- (R=tBu, CF3) the nC→σS-R interaction is much stronger for R=CF3. Ab initio calculations gave for [MeC(Ph)SO2tBu] Li×2 Me2O an O,Li,Cα contact ion pair (CIP) and for [MeC(Ph)SO2CF3]Li×2 Me2O an O,Li,O CIP. According to cryoscopy, [PhCH2C(Ph)SO2CF 3]Li, [iHexC(Me)SO2CF3]Li, and [PhCH 2C(Ph)SO2CF3]NBu4 predominantly form monomers in tetrahydrofuran (THF) at -108 °C. The NMR spectroscopic data of salts [R1(R2)SO2R3]Li (R 3=tBu, CF3) indicate that the dominating monomeric CIPs are devoid of Cα-Li bonds. Worth their salt: Chiral Li α-(S)-trifluoromethylsulfonyl carbanion salts with ≥98 % enantiomeric excess (ee) and high configurational stability are accessible through the reaction of chiral triflones (≥98 % ee) with RLi (see figure). Their electrophilic capture occurs with high enantioselectivity. Studies of the structure and dynamics of chiral Li α-(S)-trifluoromethylsulfonyl carbanion salts revealed monomeric contact ion pairs. Copyright
Synthesis of an ionic paramagnetic ruthenium(III) complex and its application as an efficient and recyclable catalyst for the transfer hydrogenation of ketones
Zhou, Chengliang,Zhang, Jing,Dakovic, Marijana,Popovic, Zora,Zhao, Xiaoli,Liu, Ye
experimental part, p. 3435 - 3440 (2012/09/08)
A novel ionic complex, bis[1-butyl-2-(diphenylphosphanyl)-3- methylimidazolium]tetrachloridoruthenium(III) hexafluorophosphate (2), has been synthesized and fully characterized. The single-crystal X-ray diffraction analysis showed that 2 is composed of an Ru complex cation and PF 6- anion. The cation has a highly symmetrical Ru-centered octahedron geometry with four Cl atoms in the equatorial plane and two imidazolium-substituted phosphane ligands in the axial positions. It exhibits paramagnetism due to the presence of one unpaired electron in the phosphane-ligated low-spin RuIII complex. Complex 2 exhibited good catalytic performance in the transfer hydrogenation of a wide range of ketones by using alcohols as hydrogen donors. Owing to its high polarity, good thermal stability, and insensitivity to moisture and oxygen, complex 2 could be used in six catalytic cycles in the transfer hydrogenation of acetophenone without any obvious loss of activity. A novel ionic complex 2 containing an RuIII cation and PF6- anion has been synthesized. The Ru III cation possesses ideal octahedral geometry and exhibits paramagnetism due to the presence of one unpaired electron in the phosphane-ligated low-spin RuIII complex. Complex 2 proves to be an efficient and recyclable catalyst for the transfer hydrogenation of ketones with alcohols as hydrogen donors. Copyright
