Search results for "Catalyst"
showing 10 items of 516 documents
Electrochemical characterization of praseodymia doped zircon. Catalytic effect on the electrochemical reduction of molecular oxygen in polar organic …
2011
The voltammetry of microparticles and scanning electrochemical microscopy methodologies are applied to characterize praseodymium centers in praseodymia-doped zircon (PrxZr(1−y)Si(1−z)O4; y + z = x; 0.02 < x < 0.10) specimens prepared via sol–gel synthetic routes. In contact with aqueous electrolytes, two overlapping Pr-centered cathodic processes, attributable to the Pr (IV) to Pr (III) reduction of Pr centers in different sites are obtained. In water-containing, air-saturated acetone and DMSO solutions as solvent, PrxZr(1−y)Si(1−z)O4 materials produce a significant catalytic effect on the electrochemical reduction of peroxide radical anion electrochemically generated. These electrochemical…
Application of palladium complexes bearing acyclic amino(hydrazido)carbene ligands as catalysts for copper-free Sonogashira cross-coupling
2015
Abstract Metal-mediated coupling of one isocyanide in cis-[PdCl2(CNR1)2] (R1 = C6H11 (Cy) 1, tBu 2, 2,6-Me2C6H3 (Xyl) 3, 2-Cl-6-MeC6H3 4) and various carbohydrazides R2CONHNH2 [R2 = Ph 5, 4-ClC6H4 6, 3-NO2C6H4 7, 4-NO2C6H4 8, 4-CH3C6H4 9, 3,4-(MeO)2C6H3 10, naphth-1-yl 11, fur-2-yl 12, 4-NO2C6H4CH2 13, Cy 14, 1-(4-fluorophenyl)-5-oxopyrrolidine-3-yl 15, (pyrrolidin-1-yl)C(O) 16, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propane-1-yl 17, EtNHC(O) 18] or sulfohydrazides R3SO2NHNH2 [R3 = Ph 19, 4-MeC6H4 20] led to a series of (hydrazido)(amino)carbene complexes cis-[PdCl2{ C (NHNHX) N(H)R1}(CNR1)]; X = COR2, SO2R3 (21–48, isolated yields 60–96%). All prepared species were characterized by elemental…
Ethylene oligomerization with 2-hydroxymethyl-5,6,7-trihydroquinolinyl-8-ylideneamine-Ni(II) chlorides
2021
Abstract A series of Ni complexes of the general formula [2-(MeOH)-8-{N(Ar)}C9H8N]NiCl2, where Ar = 2,6-Me2C6H3 in Ni1; 2,6-Et2C6H3 in Ni2; 2,6-i-Pr2C6H3 in Ni3; 2,4,6-Me3C6H2 in Ni4; 2,6-Et2-4-MeC6H2 in Ni5 and 2,4,6-t-Bu3C6H2 in Ni6 has been synthesized and characterized by elemental analysis and IR spectroscopy. On activation with MMAO or Et2AlCl, these complexes showed high activity in ethylene oligomerization, reaching 2.23 × 106 g·mol–1 (Ni) h–1 at 30 °C with the Al/Ni ratio of 5500 and 9.11 × 105 g·mol–1 (Ni) h–1 with the Al/Ni of 800, respectively. Moreover, the content of α-C4 indicated high selectivity exceeding 99% in the Ni/Et2AlCl system. Comparing with the previous report by o…
Weak Interactions Modulating the Dimensionality in Supramolecular Architectures in Three New Nickel(II)-Hydrazone Complexes, Magnetostructural Correl…
2011
Three different ONO donor acetyl hydrazone Schiff bases have been synthesized from the condensation of acetic hydrazide with three different carbonyl compounds: salicylaldehyde (HL(1)), 2-hydroxyacetophenone (HL(2)), and 2, 3-dihydroxybenzaldehyde (HL(3)). These tridentate ligands are reacted with Ni(OOCCF(3))(2)·xH(2)O to yield three new Ni(II) complexes having distorted octahedral geometry at each Ni center: [Ni(L(1))(OOCCF(3))(CH(3)OH)](2) (1), [Ni(L(2))(OOCCF(3))(H(2)O)](2) (2), and [Ni(L(3))(L(3)H)](OOCCF(3))(H(2)O)(1.65)(CH(3)OH)(0.35) (3). The ligands and the complexes have been characterized by elemental analysis and IR and UV-vis spectroscopy, and the structures of the complexes ha…
Aromatic Nucleophilic Substitution (SNAr) of meso-Nitroporphyrin with Azide and Amines as an Alternative Metal Catalyst Free Synthetic Approach To Ob…
2014
International audience; Aromatic nucleophilic substitution reaction of the nitro group of meso-nitroporphyrins with azide and various amines was achieved and represents an alternative procedure to C-N coupling reactions usually needed to obtain such meso-N-substituted porphyrins in good yields.
A supercritical-fluid method for growing carbon nanotubes
2007
Large‐scale generation of multiwalled carbon nanotubes (MCNTs) is efficiently achieved through a supercritical fluid technique employing carbon dioxide as the carbon source. Nanotubes with diameters ranging from 10 to 20 nm and lengths of several tens of micrometers are synthesized (see figure). The supercritical‐fluid‐grown nanotubes also exhibit field‐emission characteristics similar to MCNTs grown by chemical‐vapor deposition.
Sali di imidazolio multistrato supportati covalentemente: attività catalitica per la produzione di carbonati ciclici in scCO2 e nuovi supporti per ca…
2011
I liquidi ionici supportati (SILP) hanno trovato interessanti applicazioni sia nel campo delle reazioni catalizzate da metalli che in organocatalisi [1]. Inoltre, i SILP sono stati efficacemente impiegati in reazioni di apertura di epossidi in CO2 supercritica per fornire carbonati ciclici [2]. I liquidi ionici vengono generalmente supportati covalentemente attraverso la modificazione dei gruppi funzionali presenti sulla superficie del supporto, conducendo in tal modo alla formazione di un monostrato di liquido ionico supportato. Gli esempi di SILP legati covalentemente, in maniera tale da ottenere dei multistrato, sono rari. In questa comunicazione viene riportato un metodo per preparare d…
Studium zum Vorgang der Wasserstoffübertragung, 50. Elektroreduktion und phasentransferkatalysierte Borhydrid-reduktion prochiraler Ketone
1978
Prochirale Carbonylverbindungen wurden in die entsprechenden sekundaren Alkohole ubergefuhrt a) durch Elektroreduktion und b) mit NaBH4, in beiden Fallen mit den gleichen Ephedriniumsalzen, und zwar fur a) als optisch aktive Leitsalze und fur b) als optisch aktive Phasentransfer-Katalysatoren. Es wurden bei der Elektroreduktion und bei der Phasentransfer-Katalyse die Ausbeuten an Carbinol (und Pinakol)3), die optische Ausbeute und die absolute Konfiguration des bevorzugt gebildeten Enantiomeren bestimmt. In der uberwiegenden Mehrzahl der untersuchten Beispiele besitzen die unter Mitwirkung optisch aktiver Ephedriniumsalze nach beiden Methoden erhaltenen Uberschusenantiomeren die entgegenges…
α-d-Glucopyranose Adsorption on a Pd30 Cluster Supported on Boron Nitride Nanotube
2016
Boron nitride nanotube (BNNT) as an innovative support for carbohydrate transformation processes was evaluated, using density functional theory. The α-d-glucopyranose adsorption on a Pd30 cluster, supported on BNNT, was used to check both the local activity of topologically different metallic sites and the effects of the proximity of the BNNT surface to the same metallic sites. Detailed geometrical and electronic analyses performed on Pd30/BNNT and α-d-glucopyranose/Pd30/BNNT systems were discussed. It was observed that the deposition of the Pd30 cluster onto the BNNT support gives rise to an electronic rearrangement, determining a charge transfer from the support to the adsorbed metal clus…
Enhancing the electrocatalytic activity and stability of Prussian blue analogues by increasing their electroactive sites through the introduction of …
2021
Prussian blue analogues (PBAs) have been proven as excellent Earth-abundant electrocatalysts for the oxygen evolution reaction (OER) in acidic, neutral and alkaline media. Further improvements can be achieved by increasing their electrical conductivity, but scarce attention has been paid to quantify the electroactive sites of the electrocatalyst when this enhancement occurs. In this work, we have studied how the chemical design influences the specific density of electroactive sites in different Au-PBA nanostructures. Thus, we have first obtained and fully characterized a variety of monodisperse core@shell hybrid nanoparticles of Au@PBA (PBA of NiIIFeII and CoIIFeII) with different shell siz…