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Catalytic Studies (catalytic + studies)
Selected Abstracts(,6 -Arene)ruthenium(N-heterocyclic carbene) Complexes for the Chelation-Assisted Arylation and Deuteration of Arylpyridines: Catalytic Studies and Mechanistic InsightsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010Amparo Prades Abstract A series of (,6 -arene)ruthenium complexes have been tested in the arylation of arylpyridines. One (,6 - p -cymene)ruthenium(N-heterocyclic carbene) complex (labelled as 1 in the text) was found to be the most effective, being capable of arylating a wide set of substantially different arylpyridines. Complex 1 is also able to promote the regioselective deuteration of a series of arylated N-heterocycles, via a nitrogen-directed mechanism. Two of the deuterated amines were used to measure the kinetic isotope effect (KIE) in the arylation process. The detection of an inverse KIE, together with the observation that the CH activation process does not require the addition of a base, suggest that the rate-limiting step in the arylation process may be different to that of previously reported studies. [source] Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic StudiesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Xavier Sauvage Abstract Four homobimetallic ruthenium-(p -cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p -cymene)Ru(,-Cl)3RuCl(PCy3)(,2 -C2H4)] (7a). All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl diallylmalonate, the homobimetallic ruthenium-indenylidene complex 11 outperformed all the ruthenium-benzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and allenylidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda,Grubbs catalyst [Cl2Ru(PCy3)(CH- o -O- i- PrC6H4)] via stoichiometric cross-metathesis with 2-isopropoxystyrene. The procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process. [source] Catalytic Combustion of Ethyl Acetate over Nanostructure Cobalt Supported ZSM-5 Zeolite CatalystsCHINESE JOURNAL OF CHEMISTRY, Issue 3 2009Aligholi NIAEI Abstract Gas phase catalytic combustion of ethyl acetate, as one of volatile organic compounds (VOC), was studied on nanostructure ZSM-5, HZSM-5 and Co-ZSM-5 with different cobalt loadings. Nanostructure of ZSM-5 was determined by XRD, SEM and TEM. Catalytic studies were carried out under atmospheric pressure in a fixed bed reactor. Results showed that the Co-ZSM-5 catalysts had better activity than others and at temperatures below 350 °C, amount of Co loading was more effective on catalytic activity. The order of conversion of ethyl acetate over different Co loading is as follows: Co-ZSM-5 (0.75 wt%) Synthesis, characterization and catalytic studies of ruthenium(II) chalconate complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2009M. Muthukumar Abstract Stable ruthenium(II) carbonyl complexes of the type [RuCl(CO)(EPh3)(B)(L)] (E = P or As; B = PPh3, AsPh3 or Py; L = 2,-hydroxychalcones) were synthesized from the reaction of [RuHCl(CO)(EPh3)2(B)] (E = P or As; B = PPh3, AsPh3 or Py) with 2,-hydroxychalcones in benzene under reflux. The new complexes were characterized by analytical and spectroscopic (IR, electronic 1H, 31P and 13C NMR) data. They were assigned an octahedral structure. The complexes exhibited catalytic activity for the oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N -methylmorpholine- N -oxide (NMO) as co-oxidant and were also found to be efficient transfer hydrogenation catalysts. Copyright © 2008 John Wiley & Sons, Ltd. [source] Two novel molybdenum complexes containing [Mo2O2S2]2+ fragment: synthesis, crystal structures and catalytic studiesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2007Jun-Feng Wu Abstract Mo2O2S2(HGly)(Gly)21 and K6[Mo2O2S2(nta)2][Mo2O2S2(ntaH)2]·4H2O 2 were synthesized by the reactions of (NH4)2MoS4 and amino acids L (L = glycine, nitrilotriacetic acid) in ethanol,water medium at ambient temperature. The two complexes were characterized by elemental analysis, infrared spectra, UV,visible spectra, TG,DTA and XPS. X-ray crystallographic structural analyses revealed that compound 1 is a binuclear MoSglycinate complex, a glycinate ligand is coordinated to each molybdenum atom through its amine nitrogen and carboxylato oxygen, respectively, and the third glycinate acts as a bridge through its two carboxylato oxygens linking the two molybdenum atoms. Compound 2 is also a binuclear MoS complex with two nitrilotriacetate ligands, each of which is coordinated to a molybdenum atom via its two ,-carboxylato oxygens and a nitrogen atom. Simultaneously, each molybdenum atom in 1 and 2 is chelated to a terminal oxygen and two bridging sulfurs to complete the octahedral configuration. Their catalytic activities in the reduction from C2H2 to C2H4 as well as other binuclear MoSpolycarboxylate complexes, a [Fe4S4] single cubane and a chainlike MoFeS compound were investigated and it was found that 1 exhibited relatively good catalytic activity. Copyright © 2007 John Wiley & Sons, Ltd. [source] Nanostructure Copper-exchanged ZSM-5 Catalytic Activity for Conversion of Volatile Organic Compounds (Toluene and Ethyl Acetate)CHINESE JOURNAL OF CHEMISTRY, Issue 2 2010S. Ali Hosseini Abstract Gas phase catalytic oxidation of ethyl acetate and toluene was examined over copper modified ZSM-5 catalysts under atmospheric pressure. Nanostructure of ZSM-5 was characterized by XRD, SEM and TEM techniques. Elemental composition of ZSM-5 was determined using EDX, ICP-AES and XPS techniques. Results of catalytic studies showed better catalytic activity of Cu-ZSM-5 catalysts than those of parent ZSM-5 and HZSM-5, which revealed catalytic role of copper ions in the Cu-ZSM-5 catalysts. Effects of some parameters over catalytic conversion of these compounds were also studied. Ethyl acetate showed more reactivity than toluene over the Cu-ZSM-5 catalysts. Furthermore, the catalytic activity of Cu-ZSM-5 catalysts increased with increasing the copper loadings. The conversion behavior of a binary mixture of ethyl acetate and toluene was different from that of a single form. A promotive and inhibitive behavior was observed for conversion of ethyl acetate and toluene in the binary mixture, respectively. Water vapor as co-feed had an inhibitive effect on conversion of organic compounds over the Cu-ZSM-5 catalysts. [source]
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