16327-22-3Relevant academic research and scientific papers
A General Strategy for Open-Flask Alkene Isomerization by Ruthenium Hydride Complexes with Non-Redox Metal Salts
Lv, Zhanao,Chen, Zhuqi,Hu, Yue,Zheng, Wenrui,Wang, Haibin,Mo, Wanling,Yin, Guochuan
, p. 3849 - 3859 (2017/09/18)
A homogenous metal hydride (M?H) catalyst for isomerization normally requires rigorous air-free techniques. Here, we demonstrate a highly efficient protocol in which simple non-redox metal ions as Lewis acids can promote olefin isomerization dramatically with a commercially available RuH2(CO)(PPh3)3 complex in an open-flask system. Isomerization can be accomplished within a short time, and a satisfactory selectivity for different types of unsaturated compounds can be obtained. Meanwhile, an excellent turnover number up to 17208 was achieved under air, and open-flask gram-scale experiments further demonstrated the efficiency of the RuH2(CO)(PPh3)3/non-redox-metals system. We used FTIR spectroscopy, GC–MS, NMR spectroscopy and kinetics studies to evidence that in the sluggish RuH2(CO)(PPh3)3 catalyst, bloated PPh3 ligands cause steric hindrance for the coordination of the free alkene. Alternatively, the addition of non-redox metal ions could induce the dissociation of the PPh3 ligand to offer unoccupied coordination sites for the alkene and to form the Mg-bridged adduct OC?Ru?H2?Mg2+ as the highly active species, which benefited the isomerization significantly through the metal hydride addition–elimination pathway. Finally, this strategy was demonstrated as an impactful approach for hydride catalysts of other transition metals such as Os.
Unconventional Pd@Sulfonated Silica Monoliths Catalysts for Selective Partial Hydrogenation Reactions under Continuous Flow
Liguori, Francesca,Barbaro, Pierluigi,Said, Bilel,Galarneau, Anne,Santo, Vladimiro Dal,Passaglia, Elisa,Feis, Alessandro
, p. 3245 - 3258 (2017/08/29)
Doubly functionalized, hierarchical-porosity silica monoliths were synthesized by postgrafting of sulfonic groups and in situ growth of Pd nanoparticles in that order. PdNP of 3.1 nm size located in the mesopores of the material showed to be evenly distributed within 4.6 % wt Pd monoliths. The system was explored in the continuous-flow, catalytic partial hydrogenation reaction of 3-halogeno-nitrobenzenes and 3-hexyn-1-ol in the liquid phase, showing remarkable conversion, selectivity, and resistance under very mild conditions.
Redox and Acid–Base Properties of Binuclear 4-Terphenyldithiophenolate Complexes of Nickel
Koch, Felix,Berkefeld, Andreas,Schubert, Hartmut,Grauer, Claudius
supporting information, p. 14640 - 14647 (2016/10/03)
This work reports on the redox and acid–base properties of binuclear complexes of nickel from 1,4-terphenyldithiophenol ligands. The results provide insight into the cooperative electronic interaction between a dinickel core and its ligand. Donor/acceptor contributions flexibly adjust to stabilize different redox states at the metals, which is relevant for redox reactions like proton reduction. Proton transfer to the [S2Ni2] core and Ni?H bond formation are kinetically favored over the thermodynamically favored yet unproductive proton transfer to ligand.
New biobased tetrabutylphosphonium ionic liquids: Synthesis, characterization and use as a solvent or co-solvent for mild and greener Pd-catalyzed hydrogenation processes
Hayouni, Safa,Robert, Anthony,Ferlin, Nadège,Amri, Hassen,Bouquillon, Sandrine
, p. 113583 - 113595 (2016/12/16)
Phosphonium-based Ionic Liquids (PhosILs) with natural organic derived anions (l-lactate, l-tartrate, malonate, succinate, l-malate, pyruvate, d-glucuronate, d-galacturonate, ferulate, p-coumarate) were easily prepared by acid-base method from tetrabutylphosphonium hydroxide and an excess of the corresponding acid with good yields. Their characterization was realized through classical NMR, IR and elemental analysis techniques; their viscosity and ATG parameters were also determined. These ionic liquids showed good performance and recyclability in the selective Pd-catalyzed hydrogenation of alkenes, polyenes like linoleic acid and enantioselective hydrogenation of unsaturated ketones such as isophorone at room temperature under atmospheric H2 pressure. Furthermore, NMR studies leading to computational calculations were performed to establish easily the composition of the resulting mixture obtained through the hydrogenation of linoleic acid.
Non-redox metal ions can promote Wacker-type oxidations even better than copper(II): A new opportunity in catalyst design
Qin, Shuhao,Dong, Lei,Chen, Zhuqi,Zhang, Sicheng,Yin, Guochuan
, p. 17508 - 17515 (2015/10/19)
In Wacker oxidation and inspired Pd(ii)/Cu(ii)-catalyzed C-H activations, copper(ii) is believed to serve in re-oxidizing of Pd(0) in the catalytic cycle. Herein we report that non-redox metal ions like Sc(iii) can promote Wacker-type oxidations even better than Cu(ii); both Sc(iii) and Cu(ii) can greatly promote Pd(ii)-catalyzed olefin isomerization in which the redox properties of Cu(ii) are not essential, indicating that the Lewis acid properties of Cu(ii) can play a significant role in Pd(ii)-catalyzed C-H activations in addition to its redox properties. Characterization of catalysts using UV-Vis and NMR indicated that adding Sc(OTf)3 to the acetonitrile solution of Pd(OAc)2 generates a new Pd(ii)/Sc(iii) bimetallic complex having a diacetate bridge which serves as the key active species for Wacker-type oxidation and olefin isomerization. Linkage of trivalent Sc(iii) to the Pd(ii) species makes it more electron-deficient, thus facilitating the coordination of olefin to the Pd(ii) cation. Due to the improved electron transfer from olefin to the Pd(ii) cation, it benefits the nucleophilic attack of water on the olefinic double bond, leading to efficient olefin oxidation. The presence of excess Sc(iii) prevents the palladium(0) black formation, which has been rationalized by the formation of the Sc(iii)...H-Pd(ii) intermediate. This intermediate inhibits the reductive elimination of the H-Pd(ii) bond, and facilitates the oxygen insertion to form the HOO-Pd(ii) intermediate, and thus avoids the formation of the inactive palladium(0) black. The Lewis acid promoted Wacker-type oxidation and olefin isomerization demonstrated here may open up a new opportunity in catalyst design for versatile C-H activations.
Alkene isomerisation catalysed by a ruthenium PNN pincer complex
Perdriau, Sébastien,Chang, Mu-Chieh,Otten, Edwin,Heeres, Hero J.,De Vries, Johannes G.
supporting information, p. 15434 - 15442 (2016/02/18)
The [Ru(CO)H(PNN)] pincer complex based on a dearomatised PNN ligand (PNN: 2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) was examined for its ability to isomerise alkenes. The isomerisation reaction proceeded under mild conditions after activation of the complex with alcohols. Variable-temperature (VT) NMR experiments to investigate the role of the alcohol in the mechanism lend credence to the hypothesis that the first step involves the formation of a rearomatised alkoxide complex. In this complex, the hemilabile diethylamino side-arm can dissociate, allowing alkene binding cis to the hydride, enabling insertion of the alkene into the metal-hydride bond, whereas in the parent complex only trans binding is possible. During this study, a new uncommon Ru0 coordination complex was also characterised. The scope of the alkene isomerisation reaction was examined. The catalyst tested positive! A dearomatised ruthenium PNN (2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) pincer complex, [Ru(CO)H(PNN)], was evaluated as an alkene isomerisation catalyst. The isomerisation reaction was greatly accelerated by the addition of alcohols, in particular isopropanol. Isomerisation of terminal to internal alkenes took place at room temperature. A mechanism was proposed based on variable-temperature NMR spectroscopy.
Biomass derived ionic liquids: Synthesis from natural organic acids, characterization, toxicity, biodegradation and use as solvents for catalytic hydrogenation processes
Ferlin, Nadège,Courty, Matthieu,Gatard, Sylvain,Spulak, Marcel,Quilty, Brid,Beadham, Ian,Ghavre, Mukund,Hai?, Annette,Kümmerer, Klaus,Gathergood, Nicholas,Bouquillon, Sandrine
, p. 6150 - 6161 (2013/07/25)
Ionic liquids with natural organic derived anions (l-lactate, l-tartrate, malonate, succinate, l-malate, pyruvate, d-glucuronate, d-galacturonate) were easily prepared from tetrabutylammonium hydroxide and an excess of the corresponding acid with good yields. Their characterization was realized through classical NMR, IR, and elemental analysis techniques; their viscosity and TGA (thermogravimetric analysis) parameters were also determined. These ionic liquids showed good performance and recyclability in the selective catalytic hydrogenation of 1,5-cyclooctadiene (1,5-COD) into cyclooctene (COD) at room temperature under atmospheric H2 pressure. Antimicrobial toxicity assays toward a large panel of bacteria and fungi strains were also completed and biodegradation studies (Closed Bottle test, 28 days) were also performed.
Ionic liquid layer on Pd/C catalyst: Membrane-like effect on the selectivity for multistep hydrogenation reactions
Nassor, Evelisy C. O.,Dos Santos, Eduardo N.,Moura, Flavia C. C.,Lago, Rochel M.,Araujo, Maria Helena,Tristao, Juliana C.
, p. 74 - 80,7 (2020/08/20)
In this work, it has been investigated a membrane-like effect of ionic liquid (IL) in the multistep catalytic hydrogenation of trans-cinnamaldehyde (CALD) and 1,5-ciclooctadiene (1,5-COD). A commercial Pd/C catalyst was impregnated with 1-hexyl-3-methyl-imidazolium at 0.5-10 wt%. SEM, EDS, XRD, TG and BET data suggested that the IL penetrates the carbon pore structure coating the catalyst, especially at 5 and 10% concentration. The presence of the IL layer strongly affected the selectivities of the hydrogenations of CALD and 1,5-COD. In the case of CALD, the IL favored the formation of the fully hydrogenated product (hydrocinnamyl alcohol). This result is discussed in terms of a membrane-like effect, in which the small H2 molecule diffuses more easily from toluene through the IL layer as compared to the larger cinnamaldehyde. This effect results in the production of comparatively higher concentrations of the Pd-H species, which favors the double hydrogenation. On the other hand, the IL layer during the 1,5-COD hydrogenation favored the intermediate product COE (cyclooctene). In this case, a membrane-like effect was also used to discuss the result, where the IL layer has the effect to expel the intermediate COE hindering its contact with the Pd surface.
Hydrosilylation with biscarbene Rh(I) complexes: Experimental evidence for a silylene-based mechanism
Gigler, Peter,Bechlars, Bettina,Herrmann, Wolfgang A.,Kuehn, Fritz E.
experimental part, p. 1589 - 1596 (2011/04/16)
A detailed study investigating the mechanism of the hydrosilylation of 4-F-acetophenone by N-heterocyclic biscarbene rhodium(I) complexes was performed, delivering substantial experimental evidence for a recently proposed catalytic cycle and explaining the observed side-product formation. Labeling experiments, silylene trapping reactions, and specific catalytic reactions were employed to substantiate each step of the catalytic cycle and explain the differences observed for different types of chiral catalysts. It is further shown that hydrosilylation and dehydrocoupling reactions with dihydrosilanes are mechanistically related.
Direct in situ synthesis of cationic N-heterocyclic carbene iridium and rhodium complexes from neat ionic liquid: Application in catalytic dehydrogenation of cyclooctadiene
Hintermair, Ulrich,Gutel, Thibaut,Slawin, Alexandra M.Z.,Cole-Hamilton, David J.,Santini, Catherine C.,Chauvin, Yves
, p. 2407 - 2414 (2008/09/20)
A direct synthetic route to cationic N-heterocyclic carbene (NHC) complexes of rhodium and iridium from neat dialkyl-imidazolium ionic liquids (ILs) has been found. The method uses complexes bearing basic anionic ligands, [M(COD)(PPh3)X], X = OEt, MeCO2, which react with the inactivated imidazolium cation in the absence of external bases yielding one M-NHC moiety and the free protonated base. This new one-pot synthesis leaving pure, catalytically active IL solutions is faster, cleaner and more efficient than traditional syntheses of such NHC complexes. The observed reactivity also gives insight into NHC incorporation of rhodium and iridium catalyzed reactions performed in common dialkyl-imidazolium ILs. The complexes synthesised in this manner are compared with their bis-phosphine analogues in terms of activity for catalytic dehydrogenation of 1,5-cyclooctadiene and 1,3-cyclooctadiene in neat [BMIM][NTf2] as solvent. Even at high temperature, no ligand exchange reaction is observed with [(COD)M(PPh3)2] [NTf2] catalysts. As expected, the yields of all the reactions were low, iridium was much more active in C-H activation than rhodium and the NHC ligands were more stable than triphenylphosphine. For all catalysts, the isomerisation of 1,5-cyclooctadiene is the major reaction. However, the phosphine-NHC complex of iridium seems to be more selective for dehydrogenation than its bis-phosphine counterpart, which is more active in transfer-hydrogenation and less stable under the applied conditions. Different reaction conditions were tried in order to optimise selectivity for dehydrogenation over isomerisation and transfer-hydrogenation. Surprisingly, with 1,3-cyclooctadiene as substrate selectivity for dehydrogenation is much higher than with 1,5-cyclooctadiene for all catalysts.
