Giorgio Strukul

Catalytic oxidations with hydrogen peroxide as oxidant

1: Introduction and Activation Principles.- 2: Hydrogen Peroxide: Manufacture and Industrial Use for Production of Organic Chemicals.- 3: Activation of Hydrogen Peroxide by Organic Compounds.- 4: Fenton Type Activation and Chemistry of Hydroxyl Radical.- 5: Activation of Hydrogen Peroxide with Biomimetic Systems.- 6: Nucleophilic and Electrophilic Catalysis with Transition Metal Complexes.- 7: Peroxometal Complexes Derived from Hydrogen Peroxide. Some Applications in Organic Synthesis.- 8: The Use of Polyoxometalates in Reactions with Hydrogen Peroxide.

Transition metal catalysis in the Baeyer-Villiger oxidation of ketones

Environmentally friendly oxidizing agents such as hydrogen peroxide or dioxygen can be used today in catalytic versions of the almost one century old Baeyer-Villiger oxidation with transition metal complexes as catalysts. On the right is a sketch of a possible mechanism for this reaction with a platinum catalyst in homogeneous solution.

Recent advances in catalysis in micellar media

The present review paper deals with the development of catalytic systems in water in the presence of micelles obtained by addition of surfactants, focusing on the effects of these simple, economic, and green reaction media on important aspects like recyclability, activity, product and substrate selectivity. Contributions from 2005 to 2014 are surveyed with particular emphasis on emerging findings and directions in the field of catalysis. Surfactants enable formation of nanosized apolar aggregates in bulk water where the catalysts and reagents can be dissolved thanks to weak intermolecular interactions like the hydrophobic effect and ion pairing operating in a more concentrated system compared to the bulk solvent. While in the past the use of surfactants was a straightforward approach to enable solubilization of reaction mixtures in water, nowadays specific interactions between substrates, catalysts and micelles are investigated by means of NMR and other techniques to better understand the molecular basis of this kind of supramolecular catalysis. Specifically designed surfactants to engineer micelles in order to compete efficiently with traditional catalysis in organic solvents are nowadays available.

Use of palladium based catalysts in the hydrogenation of nitrates in drinking water : from powders to membranes

Abstract The behavior of Cu or Sn promoted palladium catalysts supported on zirconia and titania for the hydrogenation of nitrate in drinking water is discussed. Catalysts are prepared either as powders (microspheres) or in the form of membranes deposited on commercial alumina tubes. The performance of the former in terms of activity and selectivity towards the formation of nitrogen in a batch reactor is presented as a function of the preparation procedure, the type of precursor, the Pd/Cu ratio and the type of promoter. The use of catalysts under diffusion controlled conditions allows to reduce significantly the amount of ammonia formed while retaining a high catalytic activity. Membrane catalysts are prepared by sol–gel and characterized by SEM, EDS and hydrogen permeability tests. Their reactivity is studied either in a recirculation reactor or in a continuous flow reactor and the effect of the initial pH, the residence time and the internal hydrogen pressure are reported.

Supramolecular control on chemo- and regioselectivity via encapsulation of (NHC)-Au catalyst within a hexameric self-assembled host

The encapsulation of a Au(I) catalyst within a self-assembled, hydrogen bonded, hexameric capsule dramatically changes its catalytic activity, leading to unusual products due to the steric requirements of the hosts cavity.

Sol-gel palladium catalysts for nitrate and nitrite removal from drinking water

Abstract Alumina-copper oxide supports can be obtained by cogelation yielding uniformly sized spheres with high surface areas and unimodal mesoporosity, that can be employed as supports for Pd catalysts obtained by impregnation. These are characterized by SEM, XRD, BET, H2 chemisorption and TPR, and can be successfully used in the hydrogenation of nitrate (nitrite) in water with minor ammonia formation.

Isomerization ofn-butane on sulfated zirconia: Evidence for the dominant role of Lewis acidity on the catalytic activity

The catalytic activity of a ZrO2/SO4 catalyst in the isomerization ofn-butane at 423 K is reversibly suppressed by addition of CO. IR analysis of the adsorption of CO indicates that the only σ-coordination of CO onto coordinatively unsaturated surface Zr4+ cations occurs in the 300–473 K interval.

New (old) hydroxo complexes of platinum(II) as catalysts for the Baeyer-Villiger oxidation of ketones with hydrogen peroxide

Enantioselective Baeyer-Villiger oxidation of cyclic ketones with hydrogen peroxide can be obtained using (P-P * )Pt(2-van) complexes (P-P * , chiral diphosphine; 2-van, bis-anion of 2-vanillin) as catalyst precursors. An analysis of the activation procedure aimed to the identification of the reactive species leads to the isolation of complexes of the type ((P-P)Pt(μ-OH)]) 2 2+ (P-P, various diphosphines). The synthesis of some new species is reported together with their characterization with IR and NMR spectroscopy and conductivity data. It is found that these complexes are catalytically active in the (enantioselective) Baeyer-Villiger oxidation of cyclic ketones with hydrogen peroxide. The basic nature of the OH ligands is exploited in the reaction with a variety of acids including hydrogen peroxide.

Übergangsmetallkatalyse bei der Baeyer-Villiger-Oxidation von Ketonen

Umweltvertragliche Oxidationsmittel wie Wasserstoffperoxid oder Disauerstoff konnen heute in der seit fast 100 Jahren bekannten Titelreaktion eingesetzt werden, wenn Ubergangsmetallverbindungen als Katalysatoren zugegen sind. Rechts ist ein moglicher Mechanismus mit einem Platinkatalysator in homogener Losung gezeigt.

Hydrogenation of carbon monoxide: evidence of a strong metal-support interaction in Rh/ZrO2 catalysts

Abstract Temperature-programmed desorption (TPD) studies are reported on a series of Rh catalysts dispersed on ZrO2 and γ-Al2O3 and activated under H2 flow at 250, 400, and 600°C. While the high temperature of activation did not show any significant difference in the Rh γ-Al 2 O 3 samples, in the case or Rh ZrO 2 a pronounced effect is quite evident. The experimental observations have been associated to a modification of the metal-support interface, for which a possible model is suggested. Parallel experiments in the hydrogenation of carbon monoxide at 220°C and P = 1 atm have shown a sharp decrease in the overall activity while the selectivity was virtually unaffected by the temperature of reduction.