692-70-6Relevant academic research and scientific papers
Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in Silica Pores, as Catalysts for Selective Hydrogenation of Unsaturated Compounds
Karakanov, Edward A.,Zolotukhina, Anna V.,Ivanov, Andrey O.,Maximov, Anton L.
, p. 358 - 381 (2019/04/04)
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.
Evaluation of Several Molybdenum and Ruthenium Catalysts for the Metathesis Homocoupling of 3-Methyl-1-Butene
Sues, Peter E.,Bukhryakov, Konstantin V.,Schrock, Richard R.
, (2017/10/17)
We synthesized Mo(NC6F5)(CHCMe2Ph)(TPPO)(PPhMe2)Cl (TPPO = 2,3,5,6-tetraphenylphenoxide), Mo(NC6F5)(CHCMe2Ph)(TTBTO)(PPhMe2)Cl (TTBTO = 2,6-di(3′,5′-di-tert-butylphenyl)phenoxide), and Mo(NC6F5)(CHCMe2Ph)(TPPO)(PPhMe2)(CF3Pyr) (CF3Pyr = 3,4-bistrifluoromethylpyrrolide), in order to evaluate them as catalysts for the homocoupling of 3-methyl-1-butene. They were compared with Mo(NC6F5)(CHCMe2Ph)(HMTO)(PPhMe2)Cl (HMTO = 2,6-dimesitylphenoxide), Mo(NC6F5)(CHCMe2Ph)(HIPTO)(PPhMe2)Cl (HIPTO = 2,6-di(2′,4′,6′-triisopropylphenyl)phenoxide), and several other Mo and Ru catalysts. In the best cases turnover numbers (TONs) of 400 – 700 were observed for the homocoupling of 3-methyl-1-butene in a closed vessel (ethylene not removed).
Palladium nanoparticles encapsulated in a dendrimer networks as catalysts for the hydrogenation of unsaturated hydrocarbons
Karakhanov, Edward A.,Maksimov, Anton L.,Zakharian, Elena M.,Kardasheva, Yulia S.,Savilov, Sergey V.,Truhmanova, Nadezhda I.,Ivanov, Andrey O.,Vinokurov, Vladimir A.
, p. 1 - 18 (2015/02/19)
A novel method has been proposed for encapsulating palladium nanoparticles up to 5 nm in the matrix of polymeric support networks based on polyamidoamine dendrimers. The shape of the particle size distribution and the catalytic activity of the materials obtained during the hydrogenation of unsaturated compounds depend strongly on the support structure. High activity (TOF up to 86,000 h-1) has been observed during the hydrogenation of styrene.
Mesoporous organic Pd-containing catalysts for the selective hydrogenation of conjugated hydrocarbons
Karakhanov,Maksimov,Aksenov,Kuznetsov,Filippova,Kardashev,Volkov
, p. 1710 - 1716 (2015/05/20)
Palladium catalysts supported on ordered organic mesoporous polymers were synthesized. The catalysts are characterized by the narrow size distribution of palladium nanoparticles with an average particle size of 2.2-5.2 nm. They demonstrate high catalytic activity and selectivity in phenylacetylene hydrogenation (896-2590 min-1, selectivity 89-98%). High activity and selectivity for alkenes are observed in the hydrogenation of conjugated dienes (for isoprene, TOF = 1850-5000 min-1, selectivity 99%; for 2,5-dimethyl-2,4-hexadiene, TOF = = 1294-2400 min-1, selectivity 100%; for 1,4-diphenyl-1,3-butadiene, TOF = 14-22 min-1, selectivity 7-16%). A dependence of the selectivity on the nature of the support and substrate was found for the hydrogenation of 1,4-diphenyl-1,3-butadiene.
"Click" dendrimers: Synthesis, redox sensing of Pd(OAc) 2, and remarkable catalytic hydrogenation activity of precise Pd nanoparticles stabilized by 1,2,3-triazole-containing dendrimers
Ornelas, Catia,Aranzaes, Jaime Ruiz,Salmon, Lionel,Astruc, Didier
, p. 50 - 64 (2008/09/18)
"Click" dendrimers containing 1,2,3-triazolyl ligands that coordinate to PdII(OAc)2 have been synthesized in view of catalytic applications, Five of these dendrimers contain ferro-cenyl termini directly attached to the triazole ligand in order to monitor the number of PdII that are introduced into the dendrimers by cyclic voltammetry. Reduction of the PdII-triazole dendrimers by using NaBH4 or methanol yields Pd nanoparticles (PdNPs) that are stabilized either by several dendrimers (G0, DSN) or by encapsulation inside a dendrimer (G1 and G2: DEN), as confirmed by TEM. Relative to PAMAM-DENs (PAMAM = poly(amidoamine)), the "click" DSNs and DENs show a remarkable efficiency and stability for olefin hydrogenation under ambient conditions of various substrates. The influence of the reductant of Pd II bound to the dendrimers is dramatic, reduction with methanol leading to much higher catalytic activity than reduction with NaBH4. The most active NPs are shown to be those derived from dendrimer G1, and variation of its termini groups (ferrocenyl, alkyl, phenyl) allowed us to clearly delineate, optimize, and rationalize the role of the dendrimer frameworks on the catalytic efficiencies. Finally, hydrogenation of various substrates catalyzed by these PdNPs shows remarkable selectivity features.
Oligomerization of α-olefins by the dimeric nickel bisamido complex [Ni{1-N(PMes2)-2-N(μ-PMes2)C6H4-κ3N,N′,P,-κ1P′}]2 activated by methylalumoxane (MAO)
Majoumo-Mbe, Felicite,L?nnecke, Peter,Volkis, Victoria,Sharma, Manab,Eisen, Moris S.,Hey-Hawkins, Evamarie
, p. 2603 - 2609 (2008/09/21)
The reaction of Li2[1,2-{N(PMes2)}2C6H4], formed in situ from n-BuLi and the corresponding amines, with 1 equiv. of [NiBr2(DME)] gives [Ni{1-N(PMes2)-2-N(μ-PMes2)C6H4-κ3N,N′,P-κ1P′}]2 (1). After activation by methylalumoxane (MAO), 1 is a highly active catalyst in the oligomerization and isomerization of α-olefins such as ethene, propene, isobutene, 1-hexene and 1,5-hexadiene. For ethene oligomerization turnover frequencies (TOFs) range from 3000 to 79015 h-1, depending on the reaction conditions. The TOF for propene oligomerization reaches 1 190 730 h-1. To our knowledge, catalyst 1, activated by MAO, is the most active catalyst for the oligomerization of propene and outperforms the best known complexes for this reaction. In the reactions with 1-hexene, 1,5-hexadiene and isobutene dimerization and isomerization products were observed.
Coupled reactions of condensation and charge transfer. 1. Formation of olefin dimer ions in reactions with ionized aromatics. Gas-phase studies
Meot-Ner, Michael,Pithawalla, Yezdi B.,Gao, Junling,El-Shall, M. Samy
, p. 8332 - 8341 (2007/10/03)
The toluene radical ion C6H5CH3(·)+, generated by resonance two-photon ionization, does not react with a single isobutene molecule (i-C4H8) which has a significantly higher ionization potential (ΔIP = 0.42 eV). However, a reaction is observed involving two i-C4H8 molecules, to form the dimer ion C8H16(·)+. A coupled reaction of dimer formation and charge transfer to the dimer is exothermic if the product is an ionized hexene with a low IF. Correspondingly, the observed nominal second-order rate coefficients, (5-25) x 10-12 cm3 s-1, are enhanced by a factor of > 105 over the expected value for direct endothermic charge transfer. Pressure and concentration effects suggest a sequential mechanism that proceeds through a C6H5CH3·+(i-C4H8) reactive π complex. The complex can isomerize to a nonreactive CH3C6H4-t-C4H9(·)+ adduct,or react with a second i-C4H8 molecule to form a C6H5CH3·+-(i-C4H8)2 complex, in which the olefin molecules are activated by the aromatic ion. Similar reactions are observed in the benzene/propene system with a somewhat larger ΔIP of 0.48 eV, suggesting that the charge density on the olefin in the complex is still sufficient to activate it for nucleophilic attack. However, aromatic/olefin systems with ΔIP > 0.87 eV show no olefin dimer formation. At low [i-C4H8] and [Ar] number densities, the rate of formation of C8H16(·)+ is proportional to [i-C4H8]2[Ar]. The corresponding fourth-order rate coefficient shows a strong negative temperature coefficient with k = 11 x 10-42 cm9 s-1 at 300 K and 2 x 10-42 cm9 s-1 at 346 K, suggesting that the mechanism can be efficient in low-temperature industrial and interstellar environments. The direct formation of the dimer bypasses the monomer olefin cation and its consequent side-reactions, and directs the products selectively into radical ion polymerization. The products and energy relationships that apply in the gas phase are observed also in clusters.
DIRECT CONVERSION OF OXIRANES TO ALKENES BY CHLOROTRIMETHYLSILANE AND SODIUM IODIDE
Caputo, Romualdo,Mangoni, Lorenzo,Neri, Orsola,Palumbo, Giovanni
, p. 3551 - 3552 (2007/10/02)
Smooth and quantitative conversion of oxiranes to alkenes is achieved by treatment with in situ generated iodotrimethylsilane.
PHOTOCHEMISTRY OF ALKYL HALIDES - VII. CYCLOPROPANATION OF ALKENES
Kropp, Paul J.,Pienta, Norbert J.,Sawyer, Joy A.,Polniaszek, Richard P.
, p. 3229 - 3236 (2007/10/02)
The previously observed cyclopropanation of alkenes by irradiation of diiodomethane (1) in their presence has been studied in more detail and found to be a synthetically useful procedure which is significantly less subject to steric effects than the traditional Simmons-Smith method.The results from photocyclopropanation of a variety of alkenes are summarized in Tables 1 and 3-4.In a number of cases the photochemical procedure afforded improved results over the Simmons-Smith method, particularly with sterically congested alkenes.Cycloalkenes showed relative rates of photocyclopropanation as a function of ring size similar to those of the Simmons-Smith method (Table 5).However, the photocyclopropanation reaction exhibited steadily increasing relative rates with increasing substitution about the double bond-in contrast with the Simmons-Smith method (Table 6), in which steric effects offset increasing nucleophilicity of the alkene with increasing substitution.The α-iodocation 2 is suggested as the methylene transfer species.In the presence of lithium bromide cation 2 was trapped to afford bromoiodomethane.
