Search results for "ATAL"
showing 10 items of 10591 documents
Highly Active Co3O4-Based Catalysts for Total Oxidation of Light C1–C3 Alkanes Prepared by a Simple Soft Chemistry Method: Effect of the Heat-T…
2021
9 figures, 2 tables.
Predicting the activity of single isolated Lewis acid sites in solid catalysts.
2006
An experimental study of the activity of Ti-, Zr- and Sn-beta catalysts in different types of oxidation reactions is combined with a quantum-chemical analysis of the electronic properties of the active sites and the adsorbed reactants. The differences observed in the catalytic behaviour of the three materials are explained in terms of the molecular orbital distribution of each system. The intrinsic Lewis acid strength of the isolated active site, the degree of back-donation from the catalyst to the empty orbitals of the organic reactant and the net atomic charges on selected atoms are proposed as predictors of reactivity.
Impact of α,β-dehydroamino acid residues on the binding abilities of di-, tri- and tetra-peptides
2000
Insertion of a dehydroamino acid residue into a sequence of di-, tri- or tetra-peptide changed considerably the binding abilities of peptide ligands towards copper(II) ions. Potentiometric and spectroscopic (EPR, UV-VIS and CD) data have shown that the amide nitrogen of the dehydroamino acid residue is more effective in co-ordination than its parent analogue. In the case of the bulky ΔPhe residue also the (Z–E) isomerisation has a critical impact on the co-ordination equilibria in the system studied.
ChemInform Abstract: Gold(I)-Catalyzed Intermolecular Oxyarylation of Alkynes: Unexpected Regiochemistry in the Alkylation of Arenes.
2010
The reaction between acetylenes and sulfoxides, studied as a test case for gold-catalyzed intermolecular addition, provides the oxyarylation compounds 3 in good yields. Unpredictably, in all cases a single regioisomer arising from the electrophilic aromatic alkylation at the position adjacent to the sulfur atom is obtained instead of the expected Friedel−Crafts regioisomer. A new concerted mechanism based on DFT calculations is proposed to account for the products in this intermolecular gold(I)-catalyzed reaction.
Efficient ethylene polymerisation catalysis by a cationic benzyl hafnium complex containing pyrrolide-imine ligandsElectronic supplementary informati…
2002
A dibenzyl hafnium(IV) complex containing pyrrolide-imine chelate ligands was synthesized and investigated as an ethylene polymerisation catalyst.
Precatalyst or dosing-device? The [Pd2{μ-(C6H4) PPh2}2{μ-O2C(C6H5)}2] complex anchored on a carboxypolystyrene polymer as an effective supplier of pa…
2020
Abstract A new catalyst has been synthesized from the precursor [Pd2{μ-(C6H4) PPh2}2 {μ-O2C(C6H5)}2] immobilized on a carboxypolystyrene polymer that exhibits an excellent dispersion of the Pd (II) centers, reusability, and catalytic activity in front of phenyl bromides. The activity of this new material was studied in detail for the Suzuki-Miyaura reaction and compared to that of Pd nanoparticles (NPs) supported on UVM-7 (a mesoporous silica), and Pd NPs stabilized with polyvinylpirrolydone. The homogeneous/heterogeneous character of the catalytic process was determined from the results of the hot-filtration, centrifugation, poisoning, three phases tests, and from differential sensitivity …
CO2 Fixation by Copper(II) Complexes of a Terpyridinophane Aza Receptor
2004
CO2 is fixed by a Cu2+ complex of a macrocyclic terpyridinophane ligand forming a carbamate group. Several features of the structure mimic the enzyme rubisco.
Promoting the activity and selectivity of high surface area Ni–Ce–O mixed oxides by gold deposition for VOC catalytic combustion
2011
Gold supported on nickel cerium oxide catalysts (Ni–Ce–O) have been studied for the total oxidation of propane, as a model for hydrocarbon volatile organic compound emission control. High surface area Ni–Ce–O catalysts were synthesized using a very simple evaporation method, where cerium and nickel salts were evaporated in the presence of a mixture of methanol and oxalic acid. Gold catalysts were prepared following a deposition–precipitation method. A very efficient catalyst for the oxidation of propane, in terms of both activity and selectivity, was obtained. This high activity has been related to the high surface area of the catalyst (and therefore to the presence of more active sites ava…
Magnetic Core–Shell Nanoparticles as Carriers for Olefin Dimerization Catalysts
2013
We report the covalent support of functionalized nickel complexes on magnetic core–shell hybrid particles γ-Fe2O3/SiO2. Two completely different ways of connecting the particle with these nickel complexes were carried out. The first approach used the hydrosilylation method between the alkene-substituted nickel complex and a silane. In a second approach, the particles were connected with the complexes by means of click chemistry (copper-catalyzed Huisgen 1,3-dipolar cycloaddition). For this purpose, the nickel complexes were substituted with an alkyne moiety. Transmission and scanning electron microscopies, energy-dispersive X-ray diffraction, and FTIR spectroscopy were the methods employed …
Pressure- and temperature-induced valence tautomeric interconversion in a o-dioxolene adduct of a cobalt-tetraazamacrocycle complex
2001
An electronic switch at the molecular level has been realized by using a class of ionic compounds of the formula [Co(L)(diox)]Y (L = tetraazamacrocyclic ligand, Y = mononegative anion). Such compounds undergo temperature- and pressure-induced intramolecular one-electron transfer equilibria. The transition temperature of interconversion varies with the nature of the counterions Y (Y = PF6, BPh4, I). Surprisingly the effect of the anion on the transition temperature is not only governed by its volume but also by its coulombic interaction.