Alida H. Éll

Bio: Alida H. Éll is an academic researcher from Stockholm University. The author has contributed to research in topics: Ruthenium & Catalysis. The author has an hindex of 10, co-authored 15 publications receiving 990 citations. Previous affiliations of Alida H. Éll include Royal Institute of Technology.

Efficient ruthenium-catalyzed aerobic oxidation of alcohols using a biomimetic coupled catalytic system.

Abstract: Efficient Ruthenium-Catalyzed Aerobic Oxidation of Alcohols Using a Biomimetic Coupled Catalytic System

Efficient Ruthenium‐Catalyzed Aerobic Oxidation of Amines by Using a Biomimetic Coupled Catalytic System

Abstract: Efficient aerobic oxidation of amines was developed by the use of a biomimetic coupled catalytic system involving a ruthenium-induced dehydrogenation. The principle for this aerobic oxidation is that the electron transfer from the amine to molecular oxygen occurs stepwise via coupled redox systems and this leads to a low-energy electron transfer. A substrate-selective ruthenium catalyst dehydrogenates the amine and the hydrogen atoms abstracted are transported to an electron-rich quinone (2a). The hydroquinone thus formed is subsequently reoxidized by air with the aid of an oxygen-activating [Co(salen)]-type complex (27). The reaction can be used for the preparation of ketimines and aldimines in good to high yields from the appropriate corresponding amines. The reaction proceeds with high selectivity, and the catalytic system tolerates air without being deactivated. The rate of the dehydrogenation was studied by using quinone 2a as the terminal oxidant. A catalytic cycle in which the amine promotes the dissociation of the dimeric catalyst 1 is presented.

Mechanistic study of hydrogen transfer to imines from a hydroxycyclopentadienyl ruthenium hydride. Experimental support for a mechanism involving coordination of imine to ruthenium prior to hydrogen transfer.

Abstract: Reaction of [2,3,4,5-Ph4(η5-C4COH)Ru(CO)2H] (2) with different imines afforded ruthenium amine complexes at low temperatures At higher temperatures in the presence of 2, the complexes decomposed to give [Ru2(CO)4(μ-H)(C4Ph4COHOCC4Ph4)] (1) and free amine Electron-rich imines gave ruthenium amine complexes with 2 at a lower temperature than did electron-deficient imines The negligible deuterium isotope effect (kRuHOH/kRuDOD = 105) observed in the reaction of 2 with N-phenyl[1-(4-methoxyphenyl)ethylidene]amine (12) shows that neither hydride (RuH) nor proton (OH) is transferred to the imine in the rate-determining step In the dehydrogenation of N-phenyl-1-phenylethylamine (4) to the corresponding imine 8 by [2,3,4,5-Ph4(η4-C4CO)Ru(CO)2] (A), the kinetic isotope effects observed support a stepwise hydrogen transfer where the isotope effect for C−H cleavage (kCHNH/kCDNH = 324) is equal to the combined (C−H, N−H) isotope effect (kCHNH/kCDND = 326) Hydrogenation of N-methyl(1-phenylethylidene)amine (14)

Mechanistic aspects of transition metal-catalyzed hydrogen transfer reactions.

Abstract: In this tutorial review recent mechanistic studies on transition metal-catalyzed hydrogen transfer reactions are discussed. A common feature of these reactions is that they involve metal hydrides, which may be monohydrides or dihydrides. An important question is whether the substrate coordinates to the metal (inner-sphere hydrogen transfer) or if there is a direct concerted transfer of hydrogen from the metal to substrate (outer-sphere hydrogen transfer). Both experimental and theoretical studies are reviewed.

Hydroxyapatite-Supported Palladium Nanoclusters: A Highly Active Heterogeneous Catalyst for Selective Oxidation of Alcohols by Use of Molecular Oxygen

Abstract: Treatment of a stoichiometric hydroxyapatite (HAP), Ca10(PO4)6(OH)2, with PdCl2(PhCN)2 gives a new type of palladium-grafted hydroxyapatite. Analysis by means of powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX), IR, and Pd K-edge X-ray absorption fine structure (XAFS) proves that a monomeric PdCl2 species is chemisorbed on the HAP surface, which is readily transformed into Pd nanoclusters with a narrow size distribution in the presence of alcohol. Nanoclustered Pd0 species can effectively promote the alcohol oxidation under an atmospheric O2 pressure, giving a remarkably high turnover number (TON) of up to 236,000 with an excellent turnover frequency (TOF) of approximately 9800 h(-1) for a 250-mmol-scale oxidation of 1-phenylethanol under solvent-free conditions. In addition to advantages such as a simple workup procedure and the ability to recycle the catalyst, the present Pd catalyst does not require additives to complete the catalytic cycle. The diameters of the generated Pd nanoclusters can be controlled upon acting on the alcohol substrates used. Oxidation of alcohols is proposed to occur primarily on low-coordination sites within a regular arrangement of the Pd nanocluster by performing calculations on the palladium crystallites.