- Solid-State Chemistry of Molecular Metal Oxide Clusters. Ortho Metalation and Hydrogen Transport in 3PW12O40 Probed by 31P NMR Long-Range Deuterium Isotope Effects
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Deuterium isotope effects on 31P shielding that are large relative to the accuracy with which they can be measured are reported.In (Ph3P)2IrH2(dmf)2+, substitution of one 2H for 1H at the IR-H or at the ortho position in the Ph3P ligand leads to two- and three-bond isotope shifts of +0.094 and -0.110 ppm, respectively, with the effect being defined as 2H form)-δ(1H form)>.The ortho-deuterium effects on 31P for Ph3P, Ph3PO, Ph3PMe+I-, and (Ph3P)2Ir(C8H12)+ are -0.110, -0.096, -0.035, and -0.077 ppm, respectively.These long-range isotope effects are used to demonstrate a thermally activated, solid-state exchange of deuterium between iridium and only in the ortho positions of the Ph3P ligands in 3PW12O40.There occurs, additionally, an intermolecular hydrogen-deuterium exchange process.Slow exchange with c-C6D12 leads to incorporation of the deuterium label in the Ph3P rings.
- Siedle, A. R.,Newmark, R. A.
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- Transformation of a Norbornadiene Unit to Ethylenylcyclopentene Requiring Cooperation between Boron and Rhodium Centers
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The synthesis of the lithium salt of a bis-substituted borohydride anion containing a phenyl substituent and a 2-mercaptopyridyl unit (mp) is reported herein. This salt has been used as a pro-ligand for the synthesis of rhodium(I) complex, [Rh{κ3-H,H,S-H2B(Ph)(mp)}(NBD)] (1) (where NBD = 2,5-norbornadiene). The new boron-based ligand coordinates to the rhodium center via the thione donor and the two B-H bonds of the BPhH2 unit, with a dihydroborate motif. Reaction of complex 1 with two equivalents of triphenylphosphine leads to an unprecedented rearrangement and transfer of the former norbornadiene ligand to the boron center. The transformation occurs via an initial hydride migration from boron to rhodium center followed by a hydroboration of one of the double bonds. Finally, a ring-opening process occurs involving both boron and rhodium centers leading to an unusual boron-bound ethylenylcyclopentene unit. The product of this reaction was confirmed as [Rh{η1-S,η2-B,C-B(Ph)(CHCH2(C5H7)(mp)}(PPh3)2] (2). The net result of these transformations is the incorporation of the two hydrogen atoms from the secondary borohydride ligand [BPhH2(mp)]- into the former norbornadiene unit. The end point positions of these hydrogen atoms were confirmed by deuterium labeling experiments. Complex 2 was further reacted with carbon monoxide to generate [Rh{η1-S,η2-B,C-B(Ph)(CHCH2(C5H7)(mp)}(CO)(PPh3)] (3) via ligand substitution. The new ligand and the three complexes, 1, 2, and 3, have been characterized by spectroscopic techniques as well as by X-ray crystallography. Detailed characterization of 2 and 3 revealed an unusual η2-B,C coordination mode within these complexes. Further studies have demonstrated that complexes 2 and 3 react with hydrogen gas (or dimethylamine borane as a source of H2) to generate the hydrogen addition products involving the unprecedented activation of the Rh-η2-B,C motif. Complexes 2 and 3 were further found to be active catalysts for the hydrogenation of olefins and the dehydrogenation of dimethylamine borane.
- Coles, Simon J.,Da Costa, Rosenildo C.,Guwy, Alan J.,Iannetelli, Angelo,Owen, Gareth R.,Tizzard, Graham J.
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- In situ formed "weakly ligated/labile ligand" iridium(0) nanoparticles and aggregates as catalysts for the complete hydrogenation of neat benzene at room temperature and mild pressures
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"Weakly ligated/labile ligand" nanoparticles, that is nanoparticles where only weakly coordinated ligands plus the desired catalytic reactants are present, are of fundamental interest. Described herein is a catalyst system for benzene hydrogenation to cyclohexane consisting of "weakly ligated/labile ligand" Ir(0) nanoparticles and aggregates plus dry-HCl formed in situ from commercially available [(1,5-COD)IrCl]2 plus 40 ± 1 psig (~2.7 atm) H2 at 22 ± 0.1 °C. Multiple control and other experiments reveal the following points: (i) that this catalyst system is quite active with a TOF (turnover frequency) of 25 h-1 and TTO (total turnovers) of 5250; (ii) that the BF 4- and PF6- iridium salt precursors, [(1,5-COD)Ir(CH3CN)2]BF4 and [(1,5-COD)Ir(CH3CN)2]PF6, yield inferior catalysts; (iii) that iridium black with or without added, preformed HCl cannot achieve the TOF of 25 h-1 of the in situ formed Ir(0)/dry-HCl catalyst. However and importantly, CS2 poisoning experiments yield the same activity per active iridium atom for both the Ir(0)/dry-HCl and Ir black/no-HCl catalysts (12.5 h-1 Ir1-), but reveal that the Ir(0)/dry-HCl system is 10-fold more dispersed compared to the Ir(0) black catalyst. The simple but important and key result is that "weakly ligated/labile ligand" Ir(0) nanoparticles and aggregates have been made in situ as demonstrated by the fact that they have identical, per exposed Ir(0) activity within experimental error to Ir(0) black and that they have no possible ligands other than those desired for the catalysis (benzene and H2) plus the at best poor ligand HCl. As expected, the in situ catalyst is poorly stabilized, exhibiting only 60% of its initial activity in a second run of benzene hydrogenation and resulting in bulk metal precipitation. However, stabilization of the Ir(0) nanoparticles with a ca. 2-fold higher catalytic activity and somewhat longer lifetime for the complete hydrogenation of benzene was accomplished by supporting the Ir(0) nanoparticles onto zeolite-Y (TOF of 47h-1 and 8600 TTOunder otherwise identical conditions). Also reported is the interesting result that Cl- (present as Proton Sponge ·H+Cl-) completely poisons benzene hydrogenation catalysis, but not the easier cyclohexene hydrogenation catalysis under otherwise the same conditions, results that suggest different active sites for these ostensibly related hydrogenation reaction. The results suggest that synthetic routes to "weakly ligated/labile ligand" nanoparticles exhibiting improved catalytic performance is an important goal worthy of additional effort. 2010 American Chemical Society.
- Bayram, Ercan,Zahmakiran, Mehmet,Oezkar, Saim,Finke, Richard G.
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- The two-step chemical vapor deposition of Pd(allyl)Cp as an atom-efficient route to synthesize highly dispersed palladium nanoparticles on carbon nanofibers
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Highly dispersed palladium nanoparticles supported on carbon nanoflbers, which show high catalytic activity and stability in the hydrogenation of cyclooctene, were synthesized by the two-step metal organic chemical vapor deposition (MOCVD) of allylcyclopentadienylpalladium (Pd(allyl)Cp) as precursor at atmospheric pressure.
- Liang, Changhai,Xia, Wei,Soltani-Ahmadi, Hamideh,Schlueter, Oliver,Fischer, Roland A.,Muhler, Martin
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- Pd Nanoparticles supported on MIL-101: An efficient recyclable catalyst in oxidation and hydrogenation reactions
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Pd nanoparticles supported on the chromium terephthalate metal organic framework MIL-101 (Pd/MIL-101) in different loadings (0.9 and 4.5 wt%) have been successfully prepared through a simple Pd-acetate adsorption and reduction in acetone, and tested as catalyst for selected liquid phase oxidation and hydrogenation reactions. The materials were characterized by XRD, N2 adsorption-desorption isotherm, TEM, SEM-EDX and ICP analysis. The parent MIL-101 structure was found well preserved after formation of Pd nanoparticles and after catalytic reaction runs. The present catalyst afforded good activity and selectivity for the oxidation of benzyl alcohol to benzaldehyde with 85% conversion and 97% selectivity using air (1 atm) at 85 °C after 14 h. The catalyst also showed good activity in the hydrogenation of the C C bond in alkenes to corresponding alkanes and also benzaldehyde to benzyl alcohol at room temperature using H2 (1 atm). Rigorous test results confirmed that Pd-nanoparticles supported on MIL-101 are responsible for the catalytic reactions occurred. Pd/MIL-101 was reusable several times without losing the structural integrity and initial activity, and demonstrated significantly higher catalytic activities than those by a commercial Pd catalyst supported on activated carbon. Copyright
- Bhattacharjee, Samiran,Kim, Jun,Ahn, Wha-Seung
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- Synthesis, characterisation, and catalytic properties of halloysite-supported metal nanoparticles
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A facile synthetic method is reported for the immobilisation of metal nanoparticles on halloysite, an aluminosilicate material with a unique nanotubular structure. A one-step colloidal synthesis was developed, from which nine different catalysts were prepared. The materials were tested in three different catalytic hydrogenations, and the halloysite-supported catalysts were found to outperform alumina- or silica-supported catalysts prepared in the same fashion. Electron microscopy showed that the activity was closely linked to the spatial distribution of the supported metal particles, which in turn affected the shapes of certain surface-associated peaks in the infrared and nuclear magnetic resonance spectra. From this data insight is gained into the nature of the interaction between metal nanoparticles and the surfaces of these support materials.
- Jaine, Jacob. E.,Mucalo, Michael. R.
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- Encapsulation of supported metal nanoparticles with an ultra-thin porous shell for size-selective reactions
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A novel nanostructured catalyst with an ultra-thin porous shell obtained from the thermal decomposition of an aluminium alkoxide film deposited by molecular layer deposition for size-selective reactions was developed. The molecular sieving capability of the porous metal oxide films was verified by examining the liquid-phase hydrogenation of n-hexene versus cis-cyclooctene. The Royal Society of Chemistry 2013.
- Shang, Zeyu,Patel, Rajankumar L.,Evanko, Brian W.,Liang, Xinhua
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- Catalytic properties of MIL-101
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A very high catalytic activity in the cyanosilylation reaction was observed for MIL-101, a chromium based metal-organic framework; moreover, MIL-101 is also a remarkably stable support for palladium in hydrogenation reactions, with significantly higher activity than e.g. palladium on activated carbon. The Royal Society of Chemistry.
- Henschel, Antje,Gedrich, Kristina,Kraehnert, Ralph,Kaskel, Stefan
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- A Facile and In-situ Methanol-mediated Fabrication of Low Pd Loading, High-efficiency and Size-selectivity Pd@ZIF-8 Hydrogenation Catalyst
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In-situ encapsulation of tiny and well-dispersed Pd nanoparticles (Pd NPs) in zeolitic imidazolate frameworks (ZIFs) was firstly achieved using a one-pot and facile methanol-mediated growth approach, in which methanol served as both solvent and a mild reductant. The microstructure, morphology, crystallinity, porosity as well as evolution process of the catalysts were determined by TEM, XRD, N2 adsorption and UV-vis spectra. Due to the complete encapsulation of such Pd NPs combined with ultrahigh surface area and uniform microporous structure of ZIF-8, the resulting Pd@ZIF-8-60 min nanocomposite exhibited more superior catalytic activity for olefins hydrogenation with TOF of 7436 h?1 and excellent size selectivity than previously reported catalysts. Furthermore, the catalyst displays excellent recyclability for 1-octene hydrogenation and without any loss of the Pd active species.
- Zhang, Fengwei,Liu, Mengmeng,Liu, Qiang,Li, Jingjing,Li, Boyang,Dong, Zhengping
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- Generation and Stabilization of Small Platinum Clusters Pt12± x Inside a Metal-Organic Framework
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The generation and matrix stabilization of ligand-free, small platinum nanoclusters (NCs) Pt12±x is presented. The metal-organic framework-template approach is based on encapsulating CO-ligated, atom-precise Pt9 Chini clusters [{Pt3(CO)6}3]2- into the zeolitic imidazolate framework ZIF-8. The selective formation of the air-stable inclusion compound [NBu4]2[{Pt3(CO)6}4]?ZIF-8 of defined atomicity Pt12 and with Pt loadings of 1-20 wt % was monitored by UV/vis and IR spectroscopy and was confirmed by high-resolution transmission electron microscopy (HR-TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (PXRD). Thermally induced decarbonylation at 200 °C yields the composite material Ptn?ZIF-8 with a cluster atomicity n close to 12, irrespective of the Pt loading. The PtNCs retain their size even during annealing at 300 °C for 24 h and during catalytic hydrogenation of 1-hexene at 25 °C in the liquid phase. The Ptn?ZIF-8 material can conveniently be used for storing small PtNCs and their further processing. Removal of the protective ZIF-8 matrix under acidic conditions and transfer of the PtNCs to carbon substrates yields defined aggregation to small Pt nanoparticles (1.14 ± 0.35 nm, HR-TEM), which have previously shown exceptional performance in the electrocatalytic oxygen reduction reaction (ORR).
- Kratzl, Kathrin,Kratky, Tim,Günther, Sebastian,Tomanec, Ond?ej,Zbo?il, Radek,Michali?ka, Jan,Macak, Jan M.,Cokoja, Mirza,Fischer, Roland A.
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- CNC-pincer iron complexes containing a bis(N-heterocyclic carbene)Amido ligand: Synthesis and application to catalytic hydrogenation of alkenes
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This work studied preparation and catalytic application of CNC-pincer Fe complexes containing a bis(NHC)amido ligand (NHC: N-heterocyclic carbene). Deprotonation of bis(3-isopropylimidazoliumyl)amine salt [(CNCiPr)H3]2+[I?]2 (1a) with lithium hexamethyldisilazide (LiHMDS) afforded the corresponding bis(NHC)amido-Li complex 2a. Treatment of in-situ generated 2a with FeI2(thf)2 gave a CNC-pincer Fe(II) iodide complex Fe(CNCiPr)I (3a) and a cationic homoleptic Fe(III) complex [Fe(CNCiPr)2]+I? (4a). Reaction of in-situ generated 2a with Fe[N(SiMe3)2]2 produced the corresponding amido complex Fe(CNCiPr)[N(SiMe3)2] (5a). Similarly, deprotonation of a less hindered methyl analogue [(CNCMe)H3]2+[I?]2 (1b) with LiHMDS followed by treatment of Fe[N(SiMe3)2]2 gave an amido complex Fe(CNCMe)[N(SiMe3)2] (5b). Molecular structures of 3a, 5a and 5b, which were confirmed by X-ray diffraction study, showed a distorted tetrahedral geometry. Complexes 3a and 5b were found to be active in hydrogenation of alkenes. Reaction mechanism was investigated by density functional theory (DFT) calculations.
- Ito, Jun-ichi,Taniguchi, Wakano,Yamashita, Makoto
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- Forays into rhodium macrocyclic chemistry stabilized by a P2N2donor set. Activation of dihydrogen and benzene
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The reaction of the dilithium diamido-diphosphine macrocycle, Li2[N(SiMe2CH2P(Ph)CH2SiMe2)2N] (Li2[P2N2]) with [Rh(COD)Cl]2 generates the dirhodium macrocyclic compound, [P2N2][Rh(COD)]2 (where COD = η4-1,5-cyclooctadiene), wherein both rhodium-COD units are syn to each other and have square planar geometries. While this dirhodium derivative does react with H2, no clean products could be isolated. Upon reaction of Li2[P2N2] with [Rh(COE)2Cl]2 (where COE is η2-cyclooctene), the dilithium-dihodium derivative ([Rh(COE)][P2N2]Li)2(dioxane) forms, which was characterized by single-crystal X-ray analysis and NMR spectroscopy. The cyclooctene derivative reacts with dihydrogen in benzene to generate the dilithium-dirhodium-dihydride complex ([Rh(H)2][P2N2]Li)2(dioxane); also formed is the dilithium-dirhodium-phenylhydride complex ([Rh(C6H5)H][P2N2]Li)2(dioxane) via oxidative addition of a C-H bond of the solvent. The phenyl-hydride is eventually converted to the dihydride derivative via further reaction with H2. This process is complicated by adventitious H2O, which leads to the isolation of the amine-dihydride, Rh[P2N2H](H)2; drying of the H2 eliminates this side product. Nevertheless, careful addition of H2O to ([Rh(COE)][P2N2]Li)2(dioxane) results in protonation of one of the amido units and the formation of the rhodium-amine cyclooctene derivative, Rh[P2N2H](COE), which upon reaction with H2 generates the aforementioned amine-dihydride, Rh[P2N2H](H)2. The mechanism by which dihydrogen and C-H bonds of benzene are activated likely involves initial dissociation of cyclooctene from the 18-electron centers in ([Rh(COE)][P2N2]Li)2(dioxane), followed by H-H and C-H bond activation. The ability of one of the amido units of the P2N2 macrocycle to be protonated is a potentially useful proton storage mechanism and is of interest in other bond activation processes.
- Yeo, Alyssa,Sanz, Corey A.,Fryzuk, Michael D.
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- A neutral heteroatomic zintl cluster for the catalytic hydrogenation of cyclic alkenes
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We report on the synthesis of an alkane-soluble Zintl cluster, [η4-Ge9(Hyp)3]Rh(COD), that can catalytically hydrogenate cyclic alkenes such as 1,5-cyclooctadiene and cis-cyclooctene. This is the first example of a well-defined Zintl-clusterbased homogeneous catalyst.
- Townrow, Oliver P. E.,Chung, Cheuk,Macgregor, Stuart A.,Weller, Andrew S.,Goicoechea, Jose M.
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- Pt nanoclusters confined within metal-organic framework cavities for chemoselective cinnamaldehyde hydrogenation
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A highly selective and robust catalyst based on Pt nanoclusters (NCs) confined inside the cavities of an amino-functionalized Zr-terephthalate metal-organic framework (MOF), UiO-66-NH2 was developed. The Pt NCs are monodisperse and confined in the cavities of UiO-66-NH2 even at 10.7 wt % Pt loading. This confinement was further confirmed by comparing the catalytic performance of Pt NCs confined inside and supported on the external surface of the MOF in the hydrogenation of ethylene, 1-hexene, and 1,3-cyclooctadiene. The benefit of confining Pt NCs inside UiO-66-NH2 was also demonstrated by evaluating their performance in the chemoselective hydrogenation of cinnamaldehyde. We found that both high selectivity to cinnamyl alcohol and high conversion of cinnamaldehyde can be achieved using the MOF-confined Pt nanocluster catalyst, while we could not achieve high cinnamyl alcohol selectivity on Pt NCs supported on the external surface of the MOF. The catalyst can be recycled ten times without any loss in its activity and selectivity. To confirm the stability of the recycled catalysts, we conducted kinetic studies for the first 20 h of reaction during four recycle runs on the catalyst. Both the conversion and selectivity are almost overlapping for the four runs, which indicates the catalyst is very stable under the employed reaction conditions.
- Guo, Zhiyong,Xiao, Chaoxian,Maligal-Ganesh, Raghu V.,Zhou, Lin,Goh, Tian Wei,Li, Xinle,Tesfagaber, Daniel,Thiel, Andrew,Huang, Wenyu
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- Palladium complexes comprising C(4)-bound diimidazolylidene carbenes
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Imidazolium-derived palladium dicarbene complexes have been synthesized which feature either normal C(2) carbene bonding or abnormal C(4) bonding. Comparison of the reactivity of these complexes, in particular towards Lewis acids (H+, Ag+), indicate consistently that C(4)-bound carbenes are stronger donors than their C(2)-bound analogs. As a consequence of this electronic impact, palladium complexes comprising C(4)-bound dicarbene ligands were found to be efficient catalysts for olefin hydrogenation under mild conditions. Schweizerische Chemische Gesellschaft.
- Heckenroth, Marion,Albrecht, Martin
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- Double addition of H2 to transition metal-borane complexes: A 'hydride shuttle' process between boron and transition metal centres
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The addition of H2 across a transition metal-borane bond is reported for the first time providing a mechanism for recharging borane functional groups to borohydride.
- Tsoureas, Nikolaos,Kuo, Yu-Ying,Haddow, Mairi F.,Owen, Gareth R.
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- Yolk-shell nanocrystal@ZIF-8 nanostructures for gas-phase heterogeneous catalysis with selectivity control
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A general synthetic strategy for yolk-shell nanocrystal@ZIF-8 nanostructures has been developed. The yolk-shell nanostructures possess the functions of nanoparticle cores, microporous shells, and a cavity in between, which offer great potential in heterogeneous catalysis. The synthetic strategy involved first coating the nanocrystal cores with a layer of Cu2O as the sacrificial template and then a layer of polycrystalline ZIF-8. The clean Cu2O surface assists in the formation of the ZIF-8 coating layer and is etched off spontaneously and simultaneously during this process. The yolk-shell nanostructures were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and nitrogen adsorption. To study the catalytic behavior, hydrogenations of ethylene, cyclohexene, and cyclooctene as model reactions were carried out over the Pd@ZIF-8 catalysts. The microporous ZIF-8 shell provides excellent molecular-size selectivity. The results show high activity for the ethylene and cyclohexene hydrogenations but not in the cyclooctene hydrogenation. Different activation energies for cyclohexene hydrogenation were obtained for nanostructures with and without the cavity in between the core and the shell. This demonstrates the importance of controlling the cavity because of its influence on the catalysis.
- Kuo, Chun-Hong,Tang, Yang,Chou, Lien-Yang,Sneed, Brian T.,Brodsky, Casey N.,Zhao, Zipeng,Tsung, Chia-Kuang
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- Ir-Catalyzed Ligand-Free Directed C-H Borylation of Arenes and Pharmaceuticals: Detailed Mechanistic Understanding
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An efficient method for Ir-catalyzed ligand free ortho borylation of arenes (such as, 2-phenoxypyridines, 2-anilinopyridines, benzylamines, benzylpiperazines, benzylmorpholines, benzylpyrrolidine, benzylpiperidines, benzylazepanes, α-amino acid derivatives, aminophenylethane derivatives, and other important scaffolds) and pharmaceuticals has been developed. The reaction underwent via an interesting mechanistic pathway, as revealed by the detailed mechanistic investigations by using kinetic isotope studies and DFT calculations. The catalytic cycle is found to involve the intermediacy of an Ir-boryl complex where the substrate C-H activation is the turnover determining step, intriguingly without any appreciable primary KIE. The method displays a broad range of substrate scope and functional group tolerance. Numerous late-stage borylation of various important molecules and drugs were achieved using this developed strategy. The borylated compounds were further converted into more valuable functionalities. Moreover, utilizing the benefit of the B-N intramolecular interaction of the mono borylated compounds, an operationally simple method has been developed for the selective diborylation of 2-phenoxypyridines and numerous functionalized arenes. Furthermore, the synthetic utility has been showcased with the removal of the pyridyl directing group from the borylated product to achieve ortho borylated phenol along with the ipso-borylation for the preparation of 1,2-diborylated benzene.
- Mahamudul Hassan, Mirja Md,Mondal, Biplab,Singh, Sukriti,Haldar, Chabush,Chaturvedi, Jagriti,Bisht, Ranjana,Sunoj, Raghavan B.,Chattopadhyay, Buddhadeb
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p. 4360 - 4375
(2022/03/16)
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- Inverse Isotope Effects in Single-Crystal to Single-Crystal Reactivity and the Isolation of a Rhodium Cyclooctane σ-Alkane Complex
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The sequential solid/gas single-crystal to single-crystal reaction of [Rh(Cy2P(CH2)3PCy2)(COD)][BArF4] (COD = cyclooctadiene) with H2 or D2 was followed in situ by solid-state 31P{1H} NMR spectroscopy (SSNMR) and ex situ by solution quenching and GC-MS. This was quantified using a two-step Johnson-Mehl-Avrami-Kologoromov (JMAK) model that revealed an inverse isotope effect for the second addition of H2, that forms a σ-alkane complex [Rh(Cy2P(CH2)3PCy2)(COA)][BArF4]. Using D2, a temporal window is determined in which a structural solution for this σ-alkane complex is possible, which reveals an η2,η2-binding mode to the Rh(I) center, as supported by periodic density functional theory (DFT) calculations. Extensive H/D exchange occurs during the addition of D2, as promoted by the solid-state microenvironment.
- Doyle, Laurence R.,Furfari, Samantha K.,Galpin, Martin R.,Hicks, Scott A.,Lloyd-Jones, Guy C.,MacGregor, Stuart A.,Martínez-Martínez, Antonio J.,Tegner, Bengt E.,Weller, Andrew S.,Whitwood, Adrian C.
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supporting information
p. 284 - 292
(2022/02/10)
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- Cobalt Complexes of Bulky PNP Ligand: H2Activation and Catalytic Two-Electron Reactivity in Hydrogenation of Alkenes and Alkynes
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The reactivity of cobalt pincer complexes supported by the bulky tetramethylated PNP ligands Me4PNPR(R = iPr, tBu) has been investigated. In these ligands, the undesired H atom loss reactivity observed earlier in some classical CH2-arm PNP cobalt complexes is blocked, allowing them to be utilized for promoting two-electron catalytic transformations at the cobalt center. Accordingly, reaction of the formally CoIMe complex 3 with H2 under ambient pressure and temperature afforded the CoIII trihydride 4-H, in a reaction cascade reasoned to proceed by two-electron oxidative addition and reductive eliminations. This mechanistic proposal, alongside the observance of alkene insertion and ethane production upon sequential exposure of 3 to ethylene and H2, prompted an exploration into 3 as a catalyst for hydrogenation. Complex 4-H, formed in situ from 3 under H2, was found to be active in the catalytic hydrogenation of alkenes and alkynes. The proposed two-electron mechanism is reminiscent of the platinum group metals and demonstrates the utility of the bulky redox-innocent Me4PNPR ligand in the avoidance of one-electron reactivity, a concept that may show broad applicability in expanding the scope of earth-abundant first-row transition-metal catalysis.
- Fayzullin, Robert R.,Gallagher, James M.,Khaskin, Eugene,Khusnutdinova, Julia R.,Lapointe, Sébastien,Osborne, James,Pandey, Dilip K.
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supporting information
p. 3617 - 3626
(2021/11/16)
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- η2-Alkene Complexes of [Rh(PONOP-iPr)(L)]+Cations (L = COD, NBD, Ethene). Intramolecular Alkene-Assisted Hydrogenation and Dihydrogen Complex [Rh(PONOP-iPr)(η-H2)]+
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Rhodium-alkene complexes of the pincer ligand κ3-C5H3N-2,6-(OPiPr2)2 (PONOP-iPr) have been prepared and structurally characterized: [Rh(PONOP-iPr)(η2-alkene)][BArF4] [alkene = cyclooctadiene (COD), norbornadiene (NBD), ethene; ArF = 3,5-(CF3)2C6H3]. Only one of these, alkene = COD, undergoes a reaction with H2 (1 bar), to form [Rh(PONOP-iPr)(η2-COE)][BArF4] (COE = cyclooctene), while the others show no significant reactivity. This COE complex does not undergo further hydrogenation. This difference in reactivity between COD and the other alkenes is proposed to be due to intramolecular alkene-assisted reductive elimination in the COD complex, in which the η2-bound diene can engage in bonding with its additional alkene unit. H/D exchange experiments on the ethene complex show that reductive elimination from a reversibly formed alkyl hydride intermediate is likely rate-limiting and with a high barrier. The proposed final product of alkene hydrogenation would be the dihydrogen complex [Rh(PONOP-iPr)(η2-H2)][BArF4], which has been independently synthesized and undergoes exchange with free H2 on the NMR time scale, as well as with D2 to form free HD. When the H2 addition to [Rh(PONOP-iPr)(η2-ethene)][BArF4] is interrogated using pH2 at higher pressure (3 bar), this produces the dihydrogen complex as a transient product, for which enhancements in the 1H NMR signal for the bound H2 ligand, as well as that for free H2, are observed. This is a unique example of the partially negative line-shape effect, with the enhanced signals that are observed for the dihydrogen complex being explained by the exchange processes already noted.
- Johnson, Alice,Royle, Cameron G.,Brodie, Claire N.,Martínez-Martínez, Antonio J.,Duckett, Simon B.,Weller, Andrew S.
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supporting information
p. 13903 - 13912
(2021/03/01)
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- Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
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A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
- Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
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supporting information
p. 18591 - 18598
(2021/06/28)
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- Chemoselective Hydrogenation of Olefins Using a Nanostructured Nickel Catalyst
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The selective hydrogenation of functionalized olefins is of great importance in the chemical and pharmaceutical industry. Here, we report on a nanostructured nickel catalyst that enables the selective hydrogenation of purely aliphatic and functionalized olefins under mild conditions. The earth-abundant metal catalyst allows the selective hydrogenation of sterically protected olefins and further tolerates functional groups such as carbonyls, esters, ethers and nitriles. The characterization of our catalyst revealed the formation of surface oxidized metallic nickel nanoparticles stabilized by a N-doped carbon layer on the active carbon support.
- Klarner, Mara,Bieger, Sandra,Drechsler, Markus,Kempe, Rhett
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supporting information
p. 2157 - 2161
(2021/05/21)
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- Designing of Highly Active and Sustainable Encapsulated Stabilized Palladium Nanoclusters as well as Real Exploitation for Catalytic Hydrogenation in Water
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Abstract: Encapsulated nanoclusters based on palladium, 12-tunstophosphoric acid and silica was designed by simple wet impregnation methodology. The catalyst was found to be very efficient towards cyclohexene hydrogenation up to five catalytic runs with substrate/catalyst ratio of 4377/1 at 50?°C as well as for alkene, aldehyde, nitro and halogen compounds. Graphic Abstract: Silica encapsulated Pd nanoclusters stabilized by 12-tungstophosphoric acid is proved to be sustainable and excellent for water mediated hydrogenation reaction with very high catalyst to substrate ratio as well as TON.[Figure not available: see fulltext.]
- Patel, Anish,Patel, Anjali
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p. 803 - 820
(2020/08/12)
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- Synthesis and characterization of supported stabilized palladium nanoparticles for selective hydrogenation in water at low temperature
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Zirconia supported vacant phosphotungstate stabilized Pd nanoparticles (Pd-PW11/ZrO2) were prepared using a simple impregnation and post reduction method, characterized and their efficiency for selective C=C hydrogenation of unsaturated compounds explored. The establishment of a hydrogenation strategy at low temperature using water as solvent under mild conditions makes the present system environmentally benign and green. The catalyst shows outstanding activity (96% conversion) with just a small amount of Pd(0) (0.0034 mol%) with high substrate/catalyst ratio (29 177/1), TON (28 010) and TOF (14?005 h?1) for cyclohexene (as a model substrate) hydrogenation. The catalyst was recovered by simple centrifugation and reused for up to five catalytic cycles without alteration in its activity. The present catalyst was found to be viable towards different substrates with excellent activity and TON (18 000 to 28 800). A study on the effect of addenda atom shows that the efficiency of the catalyst can be enhanced greatly by increasing the number of counter protons. This challenging strategy would greatly benefit sustainable development in chemistry as it diminishes the use of organic solvents and offers economic and environmental benefits as water is cheap and non-toxic.
- Patel, Anish,Patel, Anjali
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p. 8218 - 8227
(2021/03/03)
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- Copper(II)-Doped ZIF-8 as a Reusable and Size Selective Heterogeneous Catalyst for the Hydrogenation of Alkenes using Hydrazine Hydrate
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In recent years, synthesis of mixed-metal organic frameworks has received considerable attention due to their superior performance than with mono-metallic metal organic frameworks (MOFs). In the present manuscript, Cu2+ ions are doped within the framework of ZIF-8 (ZIF: Zeolitic Imidazolate Frameworks) to obtain Cu@ZIF-8 and is characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV-Visible diffuse reflectance spectra (DRS), scanning electron microscope (SEM) and transmission electron microcope (TEM) studies. The reaction conditions are optimized with styrene as a model substrate using Cu@ZIF-8 as a solid catalyst. Heterogeneity of the reaction is confirmed by leaching test and the solid is reusable for three recycles with no diminishing activity. Further, the structural integrity of Cu@ZIF-8 is also retained after hydrogenation of styrene as evidenced by powder X-ray diffraction. The size selective catalysis of Cu@ZIF-8 is demonstrated by comparing the activity of Cu2+ ions adsorbed over ZIF-8 solid (Cu/ZIF-8) in the hydrogenation of 1-hexene, 1-octene, cyclohexene, cyclooctene and t-stilbene. The catalytic results indicate that Cu/ZIF-8 shows superior activity than Cu@ZIF-8 for all these olefins due to the lack of diffusion to access the active sites (Cu2+). In contrast, Cu@ZIF-8 exhibits higher activity for those olefins with lower molecular dimensions (1-hexene, 1-octene) than the pores of ZIF-8 indicating the facile diffusion of these substrates inside the pores ZIF-8 while poor activity is observed with t-stilbene due to its larger molecular dimension than the pore apertures of ZIF-8. These catalytic data clearly establish the size selective hydrogenation of Cu@ZIF-8 due to the effective confinement provided by ZIF-8 framework and the presence of the active sites within the framework. Furthermore, this is the first report showing the size selective hydrogenation of olefins promoted by Cu@ZIF-8 (mixed-metal MOFs) compared to other noble metal nanoparticles (NPs) embedded over MOFs as catalysts.
- Nagarjun, Nagarathinam,Arthy, Kannan,Dhakshinamoorthy, Amarajothi
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p. 2108 - 2119
(2021/06/01)
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- Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation
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Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M?H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co?H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT.
- Sang, Sier,Unruh, Tobias,Demeshko, Serhiy,Domenianni, Luis I.,van Leest, Nicolaas P.,Marquetand, Philipp,Schneck, Felix,Würtele, Christian,de Zwart, Felix J.,de Bruin, Bas,González, Leticia,V?hringer, Peter,Schneider, Sven
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p. 16978 - 16989
(2021/08/09)
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- Fe Exchanged Supported Phosphomolybdic Acid: Synthesis, Characterization and Low Temperature Water Mediated Hydrogenation of Cyclohexene
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In this article, first time we are reporting two steps synthesis of Fe exchanged phosphomolybdic acid supported on zirconia (Fe-PMA/ZrO2) by incipient wet impregnation and ion exchange method. The obtained material was well characterized by EDX mapping, ICP, FT-IR, Raman, 31P MAS NMR, ESR, XPS and powder XRD. The catalytic evaluation was explored for cyclohexene hydrogenation at low temperature using water as a solvent. The obtained results demonstrate remarkable efficiency of the synthesized material as a sustainable heterogeneous catalyst with very low amount of active species (Fe: 0.024?mol%), 90% conversion, high substrate/catalyst ratio (4157/1) as well as TON (3742) for 3 catalytic cycles. The present synthetic approach is highly green as it does not involve use of any noble metal, with no waste generation (E-factor = 0) as well as high reaction mass efficiency (92.20%). Graphical Abstract: [Figure not available: see fulltext.]
- Patel, Anjali,Patel, Jay
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- Amido PNP complexes of iridium: Synthesis and catalytic olefin and alkyne hydrogenation
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In situ lithiation of HN(o-C6H4PPh2)2 (H[1a]) or HN(o-C6H4PiPr2)2 (H[1b]) with nBuLi in THF at ?35°C followed by addition of [Ir(μ-Cl)(COD)]2 (COD = 1,5-cyclooctadiene) in toluene at ?35°C generates 5-coordinate [1a]Ir(η4-COD) (2a) or 4-coordinate [1b]Ir(η2-COD) (2b), respectively. Oxidative addition of N-H in H[1b] to [Ir(μ-Cl)(COD)]2 affords square pyramidal [1b]Ir(H)(Cl) (3b). Metathetical reaction of 3b with LiBHEt3 in the presence of 1 atm of H2 in toluene produces [1b]Ir(H)2 (4b). Both 2a and 4b are active for catalytic hydrogenation of olefins and alkynes under extremely mild conditions.
- Huang, Mei-Hui,Zou, Xue-Ru,Liang, Lan-Chang
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p. 353 - 360
(2019/12/24)
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- Understanding the roles of variable Pd(II)/Pd(0) ratio supported on conjugated poly-azobenzene network: From characteristic alteration in properties to their cooperation towards visible-light-induced selective hydrogenation
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Selective hydrogenation of organic functionalities at environmentally benign conditions using visible light is of great industrial and economic significance. Herein we report visible-light-induced rapid, almost quantitative and selective hydrogenation of olefins to respective mono-reduced products using cooperative performance of Pd(0) nanoparticles (NPs) and Pd(II) ions evenly distributed on a newly synthesized conjugated mesoporous poly-azobenzene network. Role of variable Pd(0)/Pd(II) ratio on the properties of polymeric networks and their overall catalytic abilities is critically investigated. This is the first proposed example of cooperative hydrogenation by simultaneous activation of H2 and unsaturated substrates using Mott-Schottky heterojunction between Pd NPs and the semiconducting polymer, with the help of Pd(II)-site-mediated η-coordination. A control over selective mono-reduction of diene with identical double bonds was also obtained. The catalytic activity retained for other non-olefinic functionalities as well.
- Nath, Ipsita,Chakraborty, Jeet,Zhang, Gaoke,Chen, Cheng,Chaemchuen, Somboon,Park, Jihae,Zhuiykov, Serge,Han, Taejun,Verpoort, Francis
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p. 120 - 128
(2020/04/15)
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- Mononuclear calcium complex as effective catalyst for alkenes hydrogenation
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Hydrogenolysis of the scorpionate-supported calcium benzyl complex [(TpAd,iPr)Ca(p-CH2C6H4-Me)(THP)] (TpAd,iPr= hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate, THP = tetrahydropyran) (2-THP) afforded the mononuclear calcium hydrido complex [(TpAd,iPr)Ca(H)(THP)] (3). Under mild conditions (40 °C, 10 atm H2, 5 mol% cat.), complex3effectively catalyzed the hydrogenation of a variety of alkenes, including activated alkenes, semi-activated alkenes, non-activated terminal and internal alkenes. Mononuclear calcium unsubstituted alkyl complex [(TpAd,iPr)Ca{(CH2)4Ph}(THP)] (6), proposed as the catalytic hydrogenation intermediate, was isolated and structurally characterized.
- Shi, Xianghui,Hou, Cuiping,Zhao, Lanxiao,Deng, Peng,Cheng, Jianhua
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supporting information
p. 5162 - 5165
(2020/05/26)
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- Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings
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Two series of bulky alkaline earth (Ae) metal amide complexes have been prepared: Ae[N(TRIP)2]2 (1-Ae) and Ae[N(TRIP)(DIPP)]2 (2-Ae) (Ae=Mg, Ca, Sr, Ba; TRIP=SiiPr3, DIPP=2,6-diisopropylphenyl). While monomeric 1-Ca was already known, the new complexes have been structurally characterized. Monomers 1-Ae are highly linear while the monomers 2-Ae are slightly bent. The bulkier amide complexes 1-Ae are by far the most active catalysts in alkene hydrogenation with activities increasing from Mg to Ba. Catalyst 1-Ba can reduce internal alkenes like cyclohexene or 3-hexene and highly challenging substrates like 1-Me-cyclohexene or tetraphenylethylene. It is also active in arene hydrogenation reducing anthracene and naphthalene (even when substituted with an alkyl) as well as biphenyl. Benzene could be reduced to cyclohexane but full conversion was not reached. The first step in catalytic hydrogenation is formation of an (amide)AeH species, which can form larger aggregates. Increasing the bulk of the amide ligand decreases aggregate size but it is unclear what the true catalyst(s) is (are). DFT calculations suggest that amide bulk also has a noticeable influence on the thermodynamics for formation of the (amide)AeH species. Complex 1-Ba is currently the most powerful Ae metal hydrogenation catalyst. Due to tremendously increased activities in comparison to those of previously reported catalysts, the substrate scope in hydrogenation catalysis could be extended to challenging multi-substituted unactivated alkenes and even to arenes among which benzene.
- Eyselein, Jonathan,F?rber, Christian,Grams, Samuel,Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Martin, Johannes,Thum, Katharina,Wiesinger, Michael
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supporting information
p. 9102 - 9112
(2020/03/30)
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- Synthesis of a hybrid Pd0/Pd-carbide/carbon catalyst material with high selectivity for hydrogenation reactions
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We present a highly selective and active Pd carbon catalyst prepared by an easy hydrothermal synthesis method. This synthetic procedure allows the stabilization under mild conditions of interstitial carbon atoms on the surface of a Pd0 carbon catalyst. The so formed Pd carbide phase appears on the upper surface layers of the Pd carbon catalyst, as demonstrated by X-ray photoelectron depth profile analysis using variable synchrotron X-ray energies. The presence of carbon in the palladium carbide species modifies the electronic state of surface Pd atoms, resulting in more electron positive Pd species (Pdδ+). This influences the adsorption of reactants and reaction intermediates during the hydrogenation of alkynes, dienes and imines, resulting in high selectivities at practically 100percent conversion.
- Climent, Maria José,Concepción, Patricia,Cored, Jorge,Corma, Avelino,Garcia-Ortiz, Andrea,Iborra, Sara,Pérez-Dieste, Virginia,Ruano, Daniel,Vidal, Juan Diego
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p. 706 - 713
(2020/08/05)
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- Catalytic Activity of a Zr MOF Containing POCOP-Pd Pincer Complexes
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A metal-organic framework assembled from POCOP-Pd pincer complex metallolinkers (1-PdBF4, Zr6O4(OH)4(L-PdMeCN)3(BF4)3, L = (2,6-(OPAr2)2C6H3, Ar = p-C6H4CO2-) has been generated via postsynthetic oxidative I-/BF4- ligand exchange with NOBF4. 1-PdBF4 catalyzes a range of organic transformations, including transfer hydrogenation of unsaturated organic substrates, terminal alkyne hydration, and intramolecular hydroarylation of alkynes. The homogeneous analogue, tBu4POCOP-PdBF4, shows poor catalytic activity for transfer hydrogenation and alkyne hydration and decomposes under the catalytic reaction conditions. Solubility limitations and catalyst deactivation pathways observed for the homogeneous pincer complex propound the advantages of using porous solid supports to immobilize organometallic species.
- Kassie, Abebu A.,Wade, Casey R.
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p. 2214 - 2221
(2020/07/06)
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- Bidentate NHC-Cobalt Catalysts for the Hydrogenation of Hindered Alkenes
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Herein, we report a series of easily accessible bidentate N-heterocyclic carbene (NHC) cobalt catalysts, which enable the hydrogenation of hindered alkenes under mild conditions. The four-coordinated bidentate NHC-Co(II) complexes were characterized by X-ray diffraction, elemental analysis, ESI-HRMS, and magnetic moment measurements, revealing a distorted-tetrahedral geometry and a high-spin configuration of the metal center. The activity of the in situ formed catalytic system, which was obtained from easily available NHC precursors, CoCl2, and NaHBEt3, was identical with those of well-defined NHC-cobalt catalysts. This highlights the potential utility of this reaction system.
- Wei, Zeyuan,Wang, Yujie,Li, Yibiao,Ferraccioli, Raffaella,Liu, Qiang
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p. 3082 - 3087
(2020/10/02)
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- Hydrogenation reaction method
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The invention relates to a hydrogenation reaction method, and belongs to the technical field of organic synthesis. The hydrogenation reaction method provided by the invention comprises the following steps: carrying out a hydrogen transfer reaction on a hydrogen acceptor compound, pinacol borane and a catalyst in a solvent in the presence of proton hydrogen, so that the hydrogen acceptor compound is subjected to a hydrogenation reaction; the catalyst is one or more than two of a palladium catalyst, an iridium catalyst and a rhodium catalyst; the hydrogen acceptor compound comprises one or morethan two functional groups of carbon-carbon double bonds, carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogentriple bonds and epoxy. The method is mild in reaction condition, easy to operate, high in yield, short in reaction time, wide in substrate application range, suitable for carbon-carbon double bonds,carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogen triple bonds and epoxy functional groups, good in selectivity and high in reaction specificity.
- -
-
Paragraph 0034; 0197-0200
(2020/05/14)
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- Bioinspired Hollow Nanoreactor: Catalysts that Carry Gaseous Hydrogen for Enhanced Gas-Liquid-Solid Three-Phase Hydrogenation Reactions
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For conventional gas-liquid-solid three-phase heterogeneous hydrogenation reactions, hydrogen must be dissolved into the solvent to be a participating reactant, restricting the reaction rates. In this study, we demonstrate that gaseous hydrogen could be directly involved in gas-liquid-solid hydrogenation reactions through a bioinspired hollow nanoreactor with superaerophilic surface to enhance the reaction rates. We produce Pd@meso-SiO2 hollow nanoreactor, whose external surface is modified with perfluorodecyltriethoxysilane (PFDTS). In aqueous solutions, H2 gas could be spread quickly on the surface and stored in the cavity of hollow spheres, and participated in hydrogenation reactions, thereby enhancing H2 concentration around Pd nanoparticles. In hydrogenation of olefin reactions, such three-phase interface allows rapid and direct transportation of H2 bubbles to the surface of Pd nanoparticles rather than through diffusion of dissolved H2 in liquid phase, leading to an enhanced catalytic rate. This strategy is expected to be useful for designing and developing new catalytic systems of gas-liquid-solid three-phase reaction.
- Li, Zhaohua,Zhu, Zhongpeng,Cao, Changyan,Jiang, Lei,Song, Weiguo
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p. 459 - 462
(2019/12/24)
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- Rhodium porphyrin molecule-based catalysts for the hydrogenation of biomass derived levulinic acid to biofuel additive γ-valerolactone
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Rhodium-meso-tetraphenylporphyrin (RhTPP) and rhodium-meso-tetrakis(4-carboxyphenyl)porphyrin (RhTCPP) complexes were synthesized and surface grafted on amine-functional mesoporous molecular sieves. The formation of ligands (TPP and TCPP) and their rhodium complexes (RhTPP and RhTCPP) was evident with the help of 1H NMR, 13C NMR, mass spectral and elemental (CHN) analysis. The absence of the pyrrole proton of the porphyrin units on RhTPP and RhTCPP confirmed the successful formation of metallo-macro-molecules. Further, RhTPP and RhTCPP were fixed on the surface of SBA-15 through amino-silane as the linker. The rhodium containing homogeneous (RhTPP and RhTCPP) and heterogeneous catalysts (RhTPP-SBA-AM and RhTCPP-SBA-AM) were used for biomass-derived levulinic acid hydrogenation. Further, the synthesized catalysts were utilized for the hydrogenation of various organic molecules having arene, carbonyl, and alkene functionality under moderate reaction conditions. Both homogeneous and heterogeneous catalysts showed more than 95% levulinic acid conversion even after four cycles. The homogeneous RhTPP and RhTCPP yielded γ-valerolactone (GVL) as a major product, whereas heterogeneous catalysts showed only comparable γ-valerolactone (GVL) selectivity, with improved reusability and recylability in the presence of relatively lower amounts of rhodium complexes. Among RhTPP and RhTCPP, RhTPP showed better selectivity for γ-valerolactone (GVL) compared to RhTCPP. Further, as the number of catalytic runs increased, there was a gradual increase in diol selectivity, which was predominant in the case of RhTCPP, possibly due to the presence of the hydrophilic carboxylate ion which facilitates the interaction of water by-products with γ-valerolactone and favours diol formation. The hydrophobic environment of the RhTPP catalyst facilitated the formation of γ-valerolactone as the major product even in the fifth run. This journal is
- Anjali, Kaiprathu,Christopher, Jayaraj,Sakthivel, Ayyamperumal,Venkatesha, Naragalu J.
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supporting information
p. 11064 - 11075
(2020/07/15)
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- Transition metal complexes of a bis(carbene) ligand featuring 1,2,4-triazolin-5-ylidene donors: structural diversity and catalytic applications
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Dialkylation of the 1,3-bis(1,2,4-triazol-1-yl)benzene with ethyl bromide results in the formation of [L-H2]Br2which, upon salt metathesis with NH4PF6, readily yields the bis(triazolium) salt [L-H2](PF6)2with non-coordinating counterions. [L-H2](PF6)2and Ag2O react in a 1?:?1 ratio to yield a binuclear AgI-tetracarbene complex of the composition [(L)2Ag2](PF6)2which undergoes a facile transmetalation reaction with [Cu(SMe2)Br] to deliver the corresponding CuI-NHC complex [(L)2Cu2](PF6)2. In contrast, the [L-H2]Br2reacts with [Ir(Cp*)Cl2]2to generate a doubly C-H activated IrIII-NHC complex5. Similarly, the triazolinylidene donor supported diorthometalated RuII-complex6is also obtained. Complexes5and6represent the first examples of a stable diorthometalated binuclear IrIII/RuII-complex supported by 1,2,4-triazolin-5-ylidene donors. The synthesized IrIII-NHC complex5is found to be more effective than its RuII-analogue (6) for the reduction of a range of alkenes/alkynesviathe transfer hydrogenation strategy. Conversely, RuII-complex6is identified as an efficient catalyst (0.01 mol% loading) for the β-alkylation of a wide range of secondary alcohols using primary alcohols as alkylating partnersviaa borrowing hydrogen strategy.
- Donthireddy, S. N. R.,Illam, Praseetha Mathoor,Rit, Arnab,Singh, Vivek Kumar
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p. 11958 - 11970
(2020/09/21)
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- Zero valent iron complexes as base partners in frustrated Lewis pair chemistry
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The prototypical iron(0) complex [Fe(CO)3(PMe3)2] (1) forms a frustrated Lewis pair (FLP) with B(C6F5)3 (BCF). In this FLP, the iron complex acts as the Lewis base partner, and the borane as the Lewis acid partner. This FLP is able to cleave H-H, H-Cl, H-O and H-S bonds in H2, HCl, H2O and HSPh. The FLP 1/BCF is shown to catalyze the hydrogenation of alkenes under mild conditions, where terminal alkenes are preferentially reduced. Mechanistic studies using D2 gas suggest that a branched intermediate in an alkene insertion cycle or an ionic cycle is favored for this catalytic reaction.
- Fraser, Craig,Tinnermann, Hendrik,Young, Rowan D.
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supporting information
p. 15184 - 15189
(2020/11/18)
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- New photocatalytic fixed-point deuteration method for carbon-carbon unsaturated bonds
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The invention relates to a new photocatalytic fixed-point deuteration method for carbon-carbon unsaturated bonds. The method is characterized in that an olefin or alkyne compound and a deuterium source undergoes a deuteration reaction under the catalysis of a light source and a photocatalyst to obtain a deuterated product, wherein the deuterium source is deuterated water, deuterated alcohol or deuterated acid, and the reaction temperature is between room temperature and 80 DEG C. The fixed-point deuteration reaction of the olefin or alkyne compound is realized under the photocatalysis action of the photocatalyst with environmentally-friendly and cheap deuterated water or a deuteration reagent as a deuterium source to substitute deuterium gas. Compared with traditional deuteration reactions, the method has a higher selectivity, milder reaction conditions and higher economical suitability, and is suitable for large-scale deuterated chemical substance production.
- -
-
Paragraph 0055; 0057; 0058; 0061
(2019/01/21)
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- Bimetallic nickel-lutetium complexes: tuning the properties and catalytic hydrogenation activity of the Ni site by varying the Lu coordination environment
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We present three heterobimetallic complexes containing an isostructural nickel center and a lutetium ion in varying coordination environments. The bidentate iPr2PCH2NHPh and nonadentate (iPr2PCH2NHAr)3tacn ligands were used to prepare the Lu metalloligands, Lu(iPr2PCH2NPh)3 (1) and Lu{(iPr2PCH2NAr)3tacn} (2), respectively. Reaction of Ni(COD)2 (where COD is 1,5-cyclooctadiene) and 1 afforded NiLu(iPr2PCH2NPh)3 (3), with a Lu coordination number (CN) of 4 and a Ni-Lu distance, d(Ni-Lu), of 2.4644(2) ?. Complex 3 can further bind THF to form 3-THF, increasing both the Lu CN to 5 and d(Ni-Lu) to 2.5989(4) ?. On the other hand, incorporation of Ni(0) into 2 provides NiLu{(iPr2PCH2NAr)3tacn} (4), in which the Lu coordination environment is more saturated (CN = 6), and the d(Ni-Lu) is substantially elongated at 2.9771(5) ?. Cyclic voltammetry of the three Ni-Lu complexes shows an overall ~410 mV shift in the Ni(0/I) redox couple, suggesting tunability of the Ni electronics across the series. Computational studies reveal polarized bonding interactions between the Ni 3dz2 (major) and the Lu 5dz2 (minor) orbitals, where the percentage of Lu character increases in the order: 4 (6.0% Lu 5dz2) 2 at low temperatures (?30 to ?80 °C) and are competent catalysts for styrene hydrogenation. Complex 3 outperforms 4 with a four-fold faster rate. Additionally, adding increasing THF equivalents to 3, which would favor build-up of 3-THF, decreases the rate. We propose that altering the coordination sphere of the Lu support can influence the resulting properties and catalytic activity of the active Ni(0) metal center.
- Ramirez, Bianca L.,Sharma, Prachi,Eisenhart, Reed J.,Gagliardi, Laura,Lu, Connie C.
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p. 3375 - 3384
(2019/03/21)
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- Cu3(BTC)2 metal organic framework as heterogeneous solid catalyst for the reduction of styrenes with silane as reducing agent
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In this work, a well known metal organic framework, Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) is reported as a heterogeneous solid catalyst for the reduction of styrene and its derivatives with silane as a reducing agent. Under these reaction conditions, a quantitative conversion of styrene is achieved with very high selectivity to ethylbenzene. A control experiment with pyridine as a catalyst poison revealed that Cu2+ located within the framework plays a crucial role in promoting this reduction. Further, hot-filtration test indicated the absence of metal leaching and Cu3(BTC)2 is used four times with no significant decay in its activity. In addition, the four times used Cu3(BTC)2 was compared with the fresh solid by powder X-ray diffraction, FT-IR, UV–Visible diffuse reflectance spectra, scanning electron microscope and electron paramagnetic resonance methods and observing no significant changes in its structural integrity, crystallinity and morphology. This process is extended for other styrene derivatives to their respective reduced products.
- Anbu, Nagaraj,Dhakshinamoorthy, Amarajothi
-
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- Sustainable visible light assisted in situ hydrogenation via a magnesium-water system catalyzed by a Pd-g-C3N4 photocatalyst
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A non-hazardous and relatively mild protocol was formulated for an effectual hydrogen generation process via a "magnesium-activated water" system with a Pd-g-C3N4 photocatalyst under visible light at room temperature. Water functions photochemically as a hydrogen donor without any external source with the Pd-g-C3N4 photocatalyst. The synthesized Pd-g-C3N4 photocatalyst is highly efficient under visible light for the selective reduction of a wide range of unsaturated derivatives and nitro compounds to afford excellent yields (>99%). The photocatalyst Pd-g-C3N4 could be easily recovered and reused for several runs without any deactivation during the photochemical hydrogen transfer reaction process.
- Sharma, Priti,Sasson, Yoel
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supporting information
p. 261 - 268
(2019/01/28)
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- A convenient method for the generation of {Rh(PNP)}+ and {Rh(PONOP)}+ fragments: Reversible formation of vinylidene derivatives
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The substitution reactions of [Rh(COD)2][BArF4] with PNP and PONOP pincer ligands 2,6-bis(di-tert-butylphosphinomethyl)pyridine and 2,6-bis(di-tert-butylphosphinito)pyridine in the weakly coordinating solvent 1,2-F2C6H4 are shown to be an operationally simple method for the generation of reactive formally 14 VE rhodium(i) adducts in solution. Application of this methodology enables synthesis of known adducts of CO, N2, H2, previously unknown water complexes, and novel vinylidene derivatives [Rh(pincer)(CCHR)][BArF4] (R = tBu, 3,5-tBu2C6H3), through reversible reactions with terminal alkynes.
- Gyton, Matthew R.,Hood, Thomas M.,Chaplin, Adrian B.
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supporting information
p. 2877 - 2880
(2019/03/06)
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- Cobalt-Catalyzed Hydrogenations via Olefin Cobaltate and Hydride Intermediates
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Redox noninnocent ligands are a promising tool to moderate electron transfer processes within base-metal catalysts. This report introduces bis(imino)acenaphthene (BIAN) cobaltate complexes as hydrogenation catalysts. Sterically hindered trisubstituted alkenes, imines, and quinolines underwent clean hydrogenation under mild conditions (2-10 bar, 20-80 °C) by use of the stable catalyst precursor [(DippBIAN)CoBr2] and the cocatalyst LiEt3BH. Mechanistic studies support a homogeneous catalysis pathway involving alkene and hydrido cobaltates as active catalyst species. Furthermore, considerable reaction acceleration by alkali cations and Lewis acids was observed. The dinuclear hydridocobaltate anion with bridging hydride ligands was isolated and fully characterized.
- Sandl, Sebastian,Maier, Thomas M.,Van Leest, Nicolaas P.,Kr?ncke, Susanne,Chakraborty, Uttam,Demeshko, Serhiy,Koszinowski, Konrad,De Bruin, Bas,Meyer, Franc,Bodensteiner, Michael,Herrmann, Carmen,Wolf, Robert,Von Jacobi Wangelin, Axel
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p. 7596 - 7606
(2019/08/20)
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- Synthesis and Reactivity of an Early-Transition-Metal Alkynyl Cubane Mn4C4 Cluster
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While the coordination chemistry of monometallic complexes and the surface properties of extended metal particles are well understood, the control of metal nanocluster formation has remained challenging. The isolation of discrete metal clusters provides an especially rare snapshot at the nanoscale of cluster growth. The synthesis and full characterization of the first early-transition-metal alkynyl cubane and the first μ3-alkynyl Mn3 motif are reported.
- Chakraborty, Uttam,Demeshko, Serhiy,Meyer, Franc,Jacobi von Wangelin, Axel
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supporting information
p. 3466 - 3470
(2019/02/20)
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- Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in Silica Pores, as Catalysts for Selective Hydrogenation of Unsaturated Compounds
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Heterogeneous Pd-containing nanocatalysts, based on poly (propylene imine) dendrimers immobilized in silica pores and networks, obtained by co-hydrolysis in situ, have been synthesized and examined in the hydrogenation of various unsaturated compounds. The catalyst activity and selectivity were found to strongly depend on the carrier structure as well as on the substrate electron and geometric features. Thus, mesoporous catalyst, synthesized in presence of both polymeric template and tetraethoxysilane, revealed the maximum activity in the hydrogenation of various styrenes, including bulky and rigid stilbene and its isomers, reaching TOF values of about 230000 h?1. Other mesoporous catalyst, synthesized in the presence of polymeric template, but without addition of Si(OEt)4, provided the trans-cyclooctene formation with the selectivity of 90–95 %, appearing as similar to homogeneous dendrimer-based catalysts. Microporous catalyst, obtained only on the presence of Si(OEt)4, while dendrimer molecules acting as both anchored ligands and template, demonstrated the maximum activity in the hydrogenation of terminal linear alkynes and conjugated dienes, reaching TOF values up to 400000 h?1. Herein the total selectivity on alkene in the case of terminal alkynes and conjugated dienes reached 95–99 % even at hydrogen pressure of 30 atm. The catalysts synthesized can be easily isolated from reaction products and recycled without significant loss of activity.
- Karakanov, Edward A.,Zolotukhina, Anna V.,Ivanov, Andrey O.,Maximov, Anton L.
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p. 358 - 381
(2019/04/04)
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- Rethinking Basic Concepts-Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes
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An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is atom economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. The most efficient precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- A nd disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 °C, while 1,2-disubstituted alkenes require a reaction temperature of 60 °C. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar were applied. A mechanism based on DFT calculations is presented, which is supported by preliminary experimental studies.
- Weber, Stefan,St?ger, Berthold,Veiros, Luis F.,Kirchner, Karl
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p. 9715 - 9720
(2019/10/14)
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- Metal complex and supported metal complex having disiloxane as ligand, method for production therefor, and supported metal catalyst prepared by using the same
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A metal complex represented by the following Formula (1): (wherein M represents palladium or platinum; L represents a ligand selected from carbon monoxide, an olefin compound, an amine compound, a phosphine compound, an N-heterocyclic carbene compound, a nitrile compound and an isocyanide compound; n represents an integer of 0 to 2 showing the number of the ligand; and each of R1 to R4 represents an organic group). The metal complex described above can be fixed on an inorganic oxide while maintaining a skeletal structure thereof to obtain a supported metal complex, and this makes it possible to allow the supported metal complex to maintain the same catalytic activity as that of the original metal complex. Also, calcining the supported metal complex obtained in the manner described above makes it possible to obtain a supported metal catalyst which is improved in catalytic activity to a greater extent than conventional supported metal catalysts.
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Page/Page column 14; 15
(2019/03/17)
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- Selective C=C Hydrogenation of Unsaturated Hydrocarbons in Neat Water Over Stabilized Palladium Nanoparticles Via Supported 12-Tungstophosphoric Acid
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Stabilized Pd(0) nanoparticles by supported 12-tungstophosphoric acid (Pd(0)-TPA/ZrO2) was explored as a sustainable recyclable catalyst for selective C=C hydrogenation of cyclohexene and crotonaldehyde. The catalyst shows an outstanding performance [catalyst to substrate ratio (1:1.31 × 104)] towards high conversion as well as 100% selectivity of the desired product with high turnover number (> 10,000) and turnover frequency (> 2600?h-1) for both the systems. The use of neat water as a solvent and mild reaction conditions makes the present system environmentally benign and green. Moreover, the catalyst could be recovered and reused up to five cycles without any significant loss in their conversion as well as selectivity. The viability of the catalyst was evaluated towards different aromatic as well as aliphatic arenes and found to be excellent in all the cases. The obtained selectivity, especially butyraldehyde, was correlated with the nature of the catalyst as well as solvent and based on the study, a plausible mechanism for both the reactions was also proposed. Graphical Abstract: [Figure not available: see fulltext.].
- Patel, Anish,Patel, Anjali
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p. 1476 - 1485
(2019/04/25)
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- Iridium-Catalyzed Alkene-Selective Transfer Hydrogenation with 1,4-Dioxane as Hydrogen Donor
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The iridium-catalyzed transfer hydrogenation of alkenes using 1,4-dioxane as a hydrogen donor is described. The use of 1,2-bis(dicyclohexylphosphino)ethane (DCyPE), featuring bulky and highly electron-donating properties, led to high catalytic activity. A polystyrene-cross-linking bisphosphine PS-DPPBz produced a reusable heterogeneous catalyst. These homogeneous and heterogeneous protocols achieved chemoselective transfer hydrogenation of alkenes over other potentially reducible functional groups such as carbonyl, nitro, cyano, and imino groups in the same molecule.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5867 - 5872
(2019/08/26)
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- Highly selective and recyclable hydrogenation of α-pinene catalyzed by ruthenium nanoparticles loaded on amphiphilic core–shell magnetic nanomaterials
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A multifunctional nanomaterial (Fe3O4@SiO2@CX@NH2) comprising a magnetic core, a silicon protective interlayer, and an amphiphilic silica shell is successfully prepared. Ru nanoparticles catalyst loaded on Fe3O4@SiO2@CX@NH2 is used in hydrogenation of α-pinene for the first time. The novel nanomaterial with amphipathy can be used as a solid foaming agent to increase gas–liquid–solid three-phase contact and accelerate the reaction. Under the mild conditions (40?°C, 1?MPa H2, 3?h), 99.9% α-pinene conversion and 98.9% cis-pinane selectivity are obtained, which is by far the best results reported. Furthermore, the magnetic nanocomposite catalyst can be easily separated by an external magnet and reused nine times with high selectivity maintaining.
- Wu, Fang-Zhu,Yu, Feng-Li,Yuan, Bing,Xie, Cong-Xia,Yu, Shi-Tao
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- Engineering channels of metal-organic frameworks to enhance catalytic selectivity
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This report describes a facile strategy to enhance the catalytic selectivity by tuning the pore sizes of metal-organic frameworks (MOFs) in nanoparticles (NPs)/MOF composite catalysts. A general post-synthetic modification method was used to adjust the pore sizes of MOFs by using anhydrides with different chain lengths to react with amino groups in the ligands. The modified NPs/MOF catalysts exhibited enhanced size selectivity performance in the hydrogenation of olefins, which revealed the flexibility of MOFs as supporting materials for heterogeneous catalysis.
- Liu, Ye,Shen, Yu,Zhang, Weina,Weng, Jiena,Zhao, Meiting,Zhu, Tingshun,Chi, Yonggui Robin,Yang, Yanhui,Zhang, Hua,Huo, Fengwei
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supporting information
p. 11770 - 11773
(2019/10/02)
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- Nitrogen-enriched porous carbon supported Pd-nanoparticles as an efficient catalyst for the transfer hydrogenation of alkenes
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Ultrafine palladium nanoparticles were immobilized on nitrogen-enriched porous carbon nanosheets (NPC), which were fabricated with g-C3N4 as a nitrogen source and a self-sacrificial template. The prepared Pd@NPC exhibited superior catalytic activity and chemoselectivity for the catalytic transfer hydrogenation of alkenes under mild conditions with formic acid as a hydrogen donor. Moreover, the catalyst displays high structure stability, and can be reused for five runs without any significant decrease of its catalytic activity and obvious leaching of Pd species. This work provides a facile and feasible approach to fabricate nitrogen-enriched carbon nanosheets and to construct advanced Pd supported heterogeneous catalysts for achieving high catalytic activity.
- Li, Jie,Zhou, Xin,Shang, Ning-Zhao,Feng, Cheng,Gao, Shu-Tao,Wang, Chun
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p. 16823 - 16828
(2018/10/23)
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- Selective Catalytic Hydrogenation of Alicyclic Dienes with Hydrogen in a Liquid Phase
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Abstract: The hydrogenation behavior of a number of alicyclic dienes (5-vinyl-2-norbornene (5-vinyl-bicyclo[2.2.1]heptene-2), dicyclopentadiene (tricyclo[5.2.1.02,6]decadiene-3,8), and cis,cis-1,5-cyclooctadiene) to the corresponding cycloalkenes in the presence of a finely divided palladium catalyst suspended in the liquid phase has been studied. The reactivities of the double bonds of these dienes have been compared. The conversion of 5-vinyl-2-norbornene and selectivity of its hydrogenation to 2-vinylnorbornane depending on the reaction conditions have been evaluated. Conditions for the selective production of desired 2-vinylnorbornane are proposed for the further implementation of this process in practice.
- Bermeshev,Antonova,Shangareev,Danilova,Pozharskaya
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p. 869 - 875
(2018/10/15)
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- Colloid and Nanosized Catalysts in Organic Synthesis: XIX.1 Influence of the Support Nature on Hydrogenation Catalysis of Cyclic Olefins by Nickel Nanoparticles
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Gas-phase hydrogenation of cycloalkenes in the presence of nickel nanoparticles supported on Ceokar-2, BAU-A activated carbon, alumina, and NaX zeolite proceeds at 140–240°C and atmospheric pressure of hydrogen. The conversion and selectivity depend on the type of support and on the hydrogen excess.
- Popov, Yu. V.,Mokhov,Nebykov,Shcherbakova,Dontsova
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- Sodium borohydride-nickel chloride hexahydrate in EtOH/PEG-400 as an efficient and recyclable catalytic system for the reduction of alkenes
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An efficient, safe and one-pot convenient catalytic system has been developed for the reduction of alkenes using NaBH4-NiCl2·6H2O in EtOH/PEG-400 under mild conditions. In this catalytic system, a variety of alkenes (including trisubstituted alkene α-pinene) were well reduced and the Ni catalyst could be recycled.
- Li, Kaoxue,Liu, Chuanchao,Wang, Kang,Ren, Yang,Li, Fahui
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p. 7761 - 7764
(2018/03/01)
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- [(NHC)CoR2]: pre-catalysts for homogeneous olefin and alkyne hydrogenation
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A novel synthesis for dialkyl cobalt compounds [(tmeda)CoR2] is presented. In these complexes tmeda is readily replaced by an NHC or a bidentate phosphine ligand to form 3- and 4-coordinate compounds, respectively. [(ItBu)Co(CH2SiMe3)2] (ItBu = 1,3-di-tert-butylimidazolin-2-ylidene) serves as an efficient, homogeneous olefin hydrogenation pre-catalyst and allows the preparation of the novel cobalt bis(alkyne) complex [(ItBu)Co(η2-PhCCPh)2].
- Enachi, Andreea,Baabe, Dirk,Zaretzke, Marc-Kevin,Schweyen, Peter,Freytag, Matthias,Raeder, Jan,Walter, Marc D.
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supporting information
p. 13798 - 13801
(2018/12/14)
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