1,721,130 research outputs found
Transition Metal Catalysis in Micellar Media: Much More Than a Simple Green Chemistry Promise
Full text linkThe micellar approach, whose major feature is the possibility to operate in water as the reaction medium, is already a major tool in the hands of synthetic organic chemists and is on the way to become an important green technology with ubiquitous fields of application. Surfactants are self-assembling auxiliaries, widely available on the market, that need no special technique to be used but are simply added to water. They allow the use of transition metal complexes developed for work in organic solvents, already optimized by ordinary synthetic elaboration without any special modification to make them compatible with water. Their use does not require any significant plant design or operational changes in the industrial practice while simplifying the separation processes
Highly dispersed rhodium/polyphosphine metal catalysts: Preparation and characterization
No full textThe preparation of novel rhodium metal catalysts, dispersed on styrene-2% divinylbenzene copolymer, functionalized with phosphine groups, is reported. The reduction temperature was chosen on the basis of temperature programmed reduction (TPR) experiments. Thermogravimetric analysis (TGA) indicates that the polymeric network in these materials is stable up to 473 K. The physical properties of the metallic phase were determined with X-ray scattering techniques (SAXS and WAXS). These techniques showed that the metal particle size and dispersion were determined mostly by the number of phosphine groups present on the support. This suggested the existence of a strong metal-ligand interaction. This fact was confirmed by an infrared study of CO absorption onto the catalysts. All polyphosphine supported samples showed CO bands which were assigned to polymer-anchored PRh(CO)2 moieties
Epoxidation of Terminal Olefins with Hydrogen Peroxide Catalyzed by Cationic pentafluorophenyl Platinum(II) Complexes
No full textMild Catalytic Oxidation of Tertiary Amines to N-Oxides with H2O2 Mediated by Pt(II) Catalyst
No full textHighly dispersed rhodium/polyphosphine metal catalysts: Catalytic activity for ethylene hydrogenation
No full textRhodium metal catalysts dispersed on polyphosphine supports were employed in the hydrogenation of ethylene. The reaction was studied in a flow reactor at 395 K and 1 atm. Turnover numbers ranged between 5.8 × 10-3 and 145 × 10-3 (molecules/sec surface atom) depending on phosphorus content. Reaction orders for olefin and hydrogen were about 0.0 and 1.0, respectively. Correlations between specific activity N and phosphorus content for various samples are reported and suggest the existence of a strong phosphorus rhodium interaction which controls the catalytic activity. This was confirmed by chemisorption measurements and activation energy data. Typical activation energy values were 5 kcal/mol for phosphinated samples and 12 kcal/mol for nonphosphinated ones
Pt(II) Pentafluorophenyl Complexes as Highly Active and Selective Catalysts in the Isomerization of Alkenes
No full textSecond-generation electron-poor platinum(II) complexes as efficient epoxidation catalysts for terminal alkenes with hydrogen peroxide
No full textThe preparation and characterization of second-generation electron-poor Pt(II) complexes of general formula [(P-P)Pt(C6F5)(H2O)][X], 1a-h (P-P = diphosphine, X = BF4, OTf), bearing a pentafluorophenyl ligand is reported. The complexes are investigated as catalysts in the epoxidation of alkenes with hydrogen peroxide in a chlorinated solvent/H2O two-phase system. The effects of the P-P ligands and of the Lewis acidity of the metal species are discussed with respect to the catalytic activity in the epoxidation reaction
Diphosphine Pentafluorophenyl Platinum(II) Complexes: An Eclectic Series of Selective Catalysts in Terminal Olefins Reactions
No full textPLATINUM(II) PENTAFLUOROPHENYL COMPLEXES: A NEW CLASS OF SELECTIVE CATALYSTS FOR TERMINAL ALKENES EPOXIDATION
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