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Mojtaba Bagherzadeh - One of the best experts on this subject based on the ideXlab platform.
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synthesis structure characterization and study of a new Molybdenum schiff base Complex as an epoxidation catalyst with very high turnover numbers
Inorganic Chemistry Communications, 2017Co-Authors: Mojtaba Bagherzadeh, Saeed Ataie, Hamed Mahmoudi, Jan JanczakAbstract:Abstract The reaction between [MoO2(acac)2] and an ONO type Schiff-base ligand (L = 4-bromo-2-((2-hydroxy-5-methylphenylimino)methyl)phenol) resulted a new oligomer Molybdenum Complex ([MoO2(L)]n). The oligomer Complex was characterized by elemental analysis, FT-IR, 1H and 13C NMR spectroscopies. A suitable single crystal of the Complex was grown in DMSO and characterized by X-ray single crystal diffraction as monomer stabilized by one DMSO molecule, [MoO2L(DMSO)]. The [MoO2(L)]n Complex was used as a catalyst in epoxidation of olefins. Besides the high activity and selectivity, very high turnover numbers were a remarkable advantage of the catalytic system.
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immobilization of a Molybdenum Complex on the surface of magnetic nanoparticles for the catalytic epoxidation of olefins
New Journal of Chemistry, 2016Co-Authors: Maryam Zare, Mojtaba Bagherzadeh, Zeinab Moradishoeili, Serdar Akbayrak, Saim OzkarAbstract:Novel organic–inorganic hybrid heterogeneous nanocatalysts were obtained by covalent anchoring of a Molybdenum(VI) Complex of salicylidene 2-picoloyl hydrazine, MoO2(sal-phz)(CH3OH), (1) on the surface of magnetic nanoparticles functionalized by one of two routes: in the first method, the surface of magnetic nanoparticles is directly modified with 3-chloropropyltrimethoxysilane yielding 1A. In the second method, magnetic nanoparticles were silica-coated with tetraethoxysilane and then with 3-chloropropyltrimethoxysilane yielding the intermediate 2B. Then Complex 1 was grafted on the surface of 1A or 2B through covalent interaction yielding 2A or 3B, respectively. The nanocatalysts 2A and 3B were characterized by FT-IR, XRD, SEM, TGA, EDX and vibrating sample magnetometry techniques. Nanocomposite 2A shows a much higher catalytic activity and stability in liquid phase epoxidation reactions, with t-BuOOH as the oxidant, compared to that of 3B. Additionally, the results of comparative study show that 2A is more active and reusable than the Mo Complex immobilized SBA-15.
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epoxidation of olefins catalyzed by a Molybdenum schiff base Complex anchored in the pores of sba 15
Journal of Molecular Catalysis A-chemical, 2014Co-Authors: Mojtaba Bagherzadeh, Mojtaba Amini, Maryam Zare, Serdar Akbayrak, Taghi Salemnoush, Saim OzkarAbstract:Abstract Novel mesostructured hybrid materials containing a Molybdenum Schiff base Complex grafted on the internal surface of SBA-15 pores were prepared by introducing MoO 2 (acac) 2 into a mesoporous silica functionalized with Schiff base ligands. The SBA-15 supports modified by an amine or salicylaldehyde were obtained by co-condensation of tetraethylorthosilicate and the corresponding organosilane in the presence of Pluronic P123 surfactant as a structure directing agent using bis[3-(trimethoxysilyl)propyl]amine or 5-chloromethylsalicylaldehyde coupled with bis[3-(trimethoxysilyl)propyl]amine as precursor. The Molybdenum (VI) Complexes immobilized on the internal surface of SBA-15 pores were employed as catalyst in the epoxidation of various alkenes using tert-butylhydroperoxide as oxidant. These immobilized Molybdenum Complexes are highly active and selective catalysts in liquid phase olefin epoxidation in dichloroethane at 84 °C. Leaching tests and metal analysis of reaction solutions showed that the kinetically competent catalyst is the Molybdenum Complex immobilized on the internal surface of SBA-15 pores and there is no Molybdenum species in the solution.
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Molybdenum oxo peroxo Complex a very fast catalyst for oxidation and reduction of sulfur based compounds
Catalysis Communications, 2012Co-Authors: Mojtaba Bagherzadeh, Mohammad Mehdi Haghdoost, Mojtaba Amini, Parviz Gohari DerakhshandehAbstract:Abstract We have evaluated the catalytic activity of a Molybdenum(VI) oxo–peroxo Complex through the oxidation and reduction of sulfur-based compounds. Arylalkyl, diaryl and dialkyl sulfides are selectively oxidized to corresponding sulfoxides, with tert -butyl hydroperoxide (TBHP), in the presence of MoO(O 2 )(phox) 2 Complex as catalyst. This Molybdenum Complex was also found to be an efficient catalyst for the deoxygenation of sulfoxides to sulfides with PPh 3 in excellent yields and chemoselectivity.
Alois Furstner - One of the best experts on this subject based on the ideXlab platform.
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Cross-metathesis of terminal alkynes.
Chemistry: A European Journal, 2014Co-Authors: Rudy Lhermet, Alois FurstnerAbstract:: Terminal acetylenes are amongst the most problematic substrates for alkyne metathesis because they tend to undergo rapid polymerization on contact with a metal alkylidyne. The Molybdenum Complex 3 endowed with triphenylsilanolate ligands, however, is capable of inducing surprisingly effective cross-metathesis reactions of terminal alkyl acetylenes with propynyl(trimethyl)silane to give products of type R(1)-C≡CSiMe. This unconventional way of introducing a silyl substituent onto an alkyne terminus complements the conventional tactics of deprotonation/silylation and excels as an orthogonal way of alkyne protecting group chemistry for substrates bearing base-sensitive functionalities. Moreover, it is shown that even terminal aryl acetylenes can be cross-metathesized with internal alkyne partners. These unprecedented transformations are compatible with various functional groups. The need to suppress acetylene formation, which seems to be a particularly effective catalyst poison, is also discussed.
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concise total syntheses of epothilone a and c based on alkyne metathesis
Chemical Communications, 2001Co-Authors: Alois Furstner, Christian Mathes, Karol GrelaAbstract:A ring closing alkyne metathesis reaction catalyzed by the Molybdenum Complex 26 followed by a Lindlar reduction of the resulting cycloalkyne product opens an efficient and stereoselective entry into epothilone A and C.
Paul J Chirik - One of the best experts on this subject based on the ideXlab platform.
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determination of the n h bond dissociation free energy in a pyridine diimine Molybdenum Complex prepared by proton coupled electron transfer
Inorganic Chemistry, 2020Co-Authors: Grant W Margulieux, Sangmin Kim, Paul J ChirikAbstract:The pyridine(diimine)Molybdenum bis(imido) Complex (iPrPDI)Mo(═NTol)2 (Tol = 4-methylphenyl) was synthesized by the addition of 2 equiv of 4-methylphenylazide to the corresponding Molybdenum benzen...
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dinitrogen coupling to a terpyridine Molybdenum chromophore is switched on by fermi resonance
Chem, 2019Co-Authors: Shahnawaz Rafiq, Mate J Bezdek, Paul J Chirik, Gregory D ScholesAbstract:Summary The traditional view of a chemical change is inherently local and classical, and such a change relies on a mix of thermodynamic and kinetic parameters to control reactivity. Often, the thermodynamic stability of chemical bonds necessitates significant energy input for activation. One fundamental question is potentially transformative: can quantum mechanics enable selective bond activation? A possible approach involves strategic input of energy to reaction-specific vibrational levels. Toward this goal, our work describes the coupling of vibrational motions in a terpyridine-Molybdenum Complex hosting a nonreactive substrate—dinitrogen. Ultrafast coherence spectroscopies revealed a Fermi-resonance coupling mechanism connecting in-plane breathing motion of the light-harvesting terpyridines with the stretching motion of the spatially disparate dinitrogen bridge. Notably, the coupling is significantly enhanced in the photoexcited state. This Fermi resonance indicates an energy conduit that drives the two motions in sync and thereby amplifies vibrational energy exchange. Achieving selective bond activation by bridging vibrations could present a quantum-inspired design principle in synthetic chemistry.
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ultrafast photophysics of a dinitrogen bridged Molybdenum Complex
Journal of the American Chemical Society, 2018Co-Authors: Shahnawaz Rafiq, Mate J Bezdek, Paul J Chirik, Marius Koch, Gregory D ScholesAbstract:Among the many metal–dinitrogen Complexes synthesized, the end-on bridging (μ2, η1, η1—N2) coordination mode is notoriously unreactive for nitrogen fixation. This is principally due to the large activation energy for ground-state nitrogen–element bond formation and motivates exploration of the photoexcited reactivity of this coordination mode. To provide the foundation for this concept, the photophysics of a dinitrogen-bridged Molybdenum Complex was explored by ultrafast electronic spectroscopies. The Complex absorbs light from the UV to near-IR, and the transitions are predominantly of metal-to-ligand charge transfer (MLCT) character. Five excitation wavelengths (440, 520, 610, 730, and 1150 nm) were employed to access MLCT bands, and the dynamics were probed between 430 and 1600 nm. Despite the large energy space occupied by electronic states (ca. 1.2 eV), the dynamics were independent of the excitation wavelength. In the proposed kinetic model, photoexcitation from a Mo–N═N–Mo centered ground state pop...
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ammonia activation h2 evolution and nitride formation from a Molybdenum Complex with a chemically and redox noninnocent ligand
Journal of the American Chemical Society, 2017Co-Authors: Grant W Margulieux, Mate J Bezdek, Zoe R Turner, Paul J ChirikAbstract:Treatment of the bis(imino)pyridine Molybdenum η6-benzene Complex (iPrPDI)Mo(η6-C6H6) (iPrPDI, 2,6-(2,6-iPr2C6H3N═CMe)2C5H3N) with NH3 resulted in coordination induced haptotropic rearrangement of the arene to form (iPrPDI)Mo(NH3)2(η2-C6H6). Analogous η2-ethylene and η2-cyclohexene Complexes were also synthesized, and the latter was crystallographically characterized. All three compounds undergo loss of the η2-coordinated ligand followed by N–H bond activation, bis(imino)pyridine modification, and H2 loss. A dual ammonia activation approach has been discovered whereby reversible M–L cooperativity and coordination induced bond weakening likely contribute to dihydrogen formation. Significantly, the weakened N–H bonds in (iPrPDI)Mo(NH3)2(η2-C2H4) enabled hydrogen atom abstraction and synthesis of a terminal nitride from coordinated ammonia, a key step in NH3 oxidation.
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coordination induced weakening of ammonia water and hydrazine x h bonds in a Molybdenum Complex
Science, 2016Co-Authors: Mate J Bezdek, Sheng Guo, Paul J ChirikAbstract:Although scores of transition metal Complexes incorporating ammonia or water ligands have been characterized over the past century, little is known about how coordination influences the strength of the nitrogen-hydrogen and oxygen-hydrogen bonds. Here we report the synthesis of a Molybdenum ammonia Complex supported by terpyridine and phosphine ligands that lowers the nitrogen-hydrogen bond dissociation free energy from 99.5 (gas phase) to an experimentally measured value of 45.8 kilocalories per mole (agreeing closely with a value of 45.1 kilocalories per mole calculated by density functional theory). This bond weakening enables spontaneous dihydrogen evolution upon gentle heating, as well as the hydrogenation of styrene. Analogous Molybdenum Complexes promote dihydrogen evolution from coordinated water and hydrazine. Electrochemical and theoretical studies elucidate the contributions of metal redox potential and ammonia acidity to this effect.
Sara Abednatanzi - One of the best experts on this subject based on the ideXlab platform.
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enhanced catalytic activity of nanoporous cu3 btc 2 metal organic framework via immobilization of oxodiperoxo Molybdenum Complex
New Journal of Chemistry, 2015Co-Authors: Sara Abednatanzi, Alireza Abbasi, Majid MasterifarahaniAbstract:Molybdenum(VI) oxodiperoxo Complex was immobilized into a post synthetically modified Cu3(BTC)2 metal–organic framework (abbreviated as CuBTC MOF, BTC = benzene-1,3,5-tricarboxylate). Characterization of the modified CuBTC MOF by Fourier transform infrared and atomic absorption spectroscopies as well as thermogravimetric and CHN elemental analyses confirmed successful modification of the framework. Powder X-ray diffraction revealed a shift for all peaks to smaller 2θ angles during the Molybdenum Complex attachment as the result of MOF expansion. Nitrogen adsorption/desorption techniques demonstrated a significant decrease in BET surface area and total pore volume during the modification process. The resulting Molybdenum-containing MOF showed higher catalytic activity and selectivity than the CuBTC MOF due to the presence of the Molybdenum(VI) oxodiperoxo Complex.
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post synthetic modification of nanoporous cu3 btc 2 metal organic framework via immobilization of a Molybdenum Complex for selective epoxidation
Journal of Molecular Catalysis A-chemical, 2015Co-Authors: Sara Abednatanzi, Alireza Abbasi, Majid MasterifarahaniAbstract:Abstract In the present work, nanoporous Cu3(BTC)2 (abbreviated as CuBTC and BTC = benzene-1,3,5-tricarboxylate) metal-organic framework (MOF) was modified in a two-step post-synthetic reaction by covalent attachment of aminopyridine groups followed by the reaction with bis(acetylacetonato) dioxoMolybdenum(VI). The prepared Molybdenum containing MOF was utilized as a heterogeneous catalyst in the epoxidation of olefins and allylic alcohols. Characterization of the prepared catalyst was performed using Fourier transform infrared, atomic absorption spectroscopies, CHN elemental analysis, powder X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and nitrogen adsorption/desorption techniques. The resulting catalyst showed high selectivity and catalytic activity toward the epoxidation reaction. Moreover, the catalyst demonstrated size-selective properties suggested the reaction occurred inside the pores.
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Molybdenum Complex tethered to the surface of activated carbon as a new recoverable catalyst for the epoxidation of olefins
Applied Catalysis A-general, 2014Co-Authors: Majid Masterifarahani, Sara AbednatanziAbstract:Abstract A new recoverable catalyst for the epoxidation of olefins was developed by covalent attachment of aminopropyl groups on the surface of oxidized activated carbon (AC) and next reaction with bis(acetylacetonato)dioxoMolybdenum(VI). Characterization of the prepared catalyst was performed with different physicochemical methods such as Fourier transform infrared and atomic absorption spectroscopies, scanning electron microscopy, energy-dispersive X-ray and nitrogen sorption analyses. Nitrogen adsorption–desorption analysis revealed that the textural characteristics of the support were changed during the grafting experiments but the channels remained relatively accessible despite sequential reduction in surface area, pore volume and pore size. Elemental analysis showed the presence of 0.06 mmol g −1 Molybdenum in the catalyst. The prepared catalyst catalyzed the epoxidation of olefins and allyl alcohols with tert -butyl hydroperoxide (TBHP) and cumene hydroperoxide (CHP) quantitatively with excellent selectivity toward the corresponding epoxides under mild reaction conditions. The results indicated that the hydrophobicity of the AC support promoted the catalytic efficiency of the catalyst in the epoxidation of olefins.
Saim Ozkar - One of the best experts on this subject based on the ideXlab platform.
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immobilization of a Molybdenum Complex on the surface of magnetic nanoparticles for the catalytic epoxidation of olefins
New Journal of Chemistry, 2016Co-Authors: Maryam Zare, Mojtaba Bagherzadeh, Zeinab Moradishoeili, Serdar Akbayrak, Saim OzkarAbstract:Novel organic–inorganic hybrid heterogeneous nanocatalysts were obtained by covalent anchoring of a Molybdenum(VI) Complex of salicylidene 2-picoloyl hydrazine, MoO2(sal-phz)(CH3OH), (1) on the surface of magnetic nanoparticles functionalized by one of two routes: in the first method, the surface of magnetic nanoparticles is directly modified with 3-chloropropyltrimethoxysilane yielding 1A. In the second method, magnetic nanoparticles were silica-coated with tetraethoxysilane and then with 3-chloropropyltrimethoxysilane yielding the intermediate 2B. Then Complex 1 was grafted on the surface of 1A or 2B through covalent interaction yielding 2A or 3B, respectively. The nanocatalysts 2A and 3B were characterized by FT-IR, XRD, SEM, TGA, EDX and vibrating sample magnetometry techniques. Nanocomposite 2A shows a much higher catalytic activity and stability in liquid phase epoxidation reactions, with t-BuOOH as the oxidant, compared to that of 3B. Additionally, the results of comparative study show that 2A is more active and reusable than the Mo Complex immobilized SBA-15.
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epoxidation of olefins catalyzed by a Molybdenum schiff base Complex anchored in the pores of sba 15
Journal of Molecular Catalysis A-chemical, 2014Co-Authors: Mojtaba Bagherzadeh, Mojtaba Amini, Maryam Zare, Serdar Akbayrak, Taghi Salemnoush, Saim OzkarAbstract:Abstract Novel mesostructured hybrid materials containing a Molybdenum Schiff base Complex grafted on the internal surface of SBA-15 pores were prepared by introducing MoO 2 (acac) 2 into a mesoporous silica functionalized with Schiff base ligands. The SBA-15 supports modified by an amine or salicylaldehyde were obtained by co-condensation of tetraethylorthosilicate and the corresponding organosilane in the presence of Pluronic P123 surfactant as a structure directing agent using bis[3-(trimethoxysilyl)propyl]amine or 5-chloromethylsalicylaldehyde coupled with bis[3-(trimethoxysilyl)propyl]amine as precursor. The Molybdenum (VI) Complexes immobilized on the internal surface of SBA-15 pores were employed as catalyst in the epoxidation of various alkenes using tert-butylhydroperoxide as oxidant. These immobilized Molybdenum Complexes are highly active and selective catalysts in liquid phase olefin epoxidation in dichloroethane at 84 °C. Leaching tests and metal analysis of reaction solutions showed that the kinetically competent catalyst is the Molybdenum Complex immobilized on the internal surface of SBA-15 pores and there is no Molybdenum species in the solution.