1,721,010 research outputs found
Iron complexes with polydentate phosphines as unusual catalysts for alcohol oxidation
Full text linkThe iron(II) compounds [Fe(triphos)(CH3CN)3](OTf)2 (triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane; OTf = CF3SO3) (1), [Fe(dppm)2(CH3CN)2](OTf)2 (dppm = bis(diphenylphosphino)methane) (2), [Fe(dppe)2(CH3CN)2](OTf)2 (dppe = 1,2-bis(diphenylphosphino)ethane) (3), [Fe(dppp)(CH3CN)4](OTf)2 (dppp = 1,3-bis(diphenylphosphino)propane) (4) and [Fe(PSP)(CH3CN)3](OTf)2 (PSP = bis(2-(diphenylphosphino)ethyl)sulfide) (5) were synthesized and characterized by NMR and (2, 3 and 4) also by X-ray crystallography. Such complexes catalyzed the selective oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones. The catalytic reactions were performed in acetonitrile in mild experimental conditions (r.t. or 50 °C) using tert-butylhydroperoxide (TBHP) as oxidizing agent. By following the reaction of complex 4 with the oxidant by UV–visible spectroscopy, it was possible to evidence formation of the corresponding iron-peroxide intermediate. Comparison of ESI-MS spectra acquired on a solution of 1 or 4 before and after TBHP addition suggests ligand oxidation to iron-phosphine oxide complexes
Vittoria Colonna
No full textIl capitolo dedicato a Vittoria Colonna ricostruisce, sulla scorta degli studi più recenti, il percorso intellettuale della poetessa di Marino, con particolare attenzione alle diverse stagioni del suo percorso poetico e all'evoluzione della sua poesia da un esordio marcato in direzione soprattutto amorosa, ad una progressiva introspezione e riflessione religiosa non esente da suggestioni di carattere eterodosso. Una discreta antologia di componimenti introdotti e commentati completa il capitolo
Dihydrogen and Hydrido Complexes via Hydrogen Addition to d6 Five-co-ordinate Complexes of Ruthenium and Osmium with 1,2-Bis(dicyclohexylphosphino)ethane
No full textThe dihydrogen complexes [MX(eta-2-H-2)(dcpe)2]BPh4 [dcpe = 1,2-bis(dicyclohexylphosphino)ethane; M = Ru, X = H or Cl; M = Os, X = Cl] were prepared by reaction of molecular hydrogen with the five-co-ordinate complexes [MX(dcpe)2]BPh4, or by protonation of the hydrides [MH(X)(dcpe)2]. The same synthetic procedures yielded [OsH3(dcpe)2]BPh4, for which a classical trihydride seven-co-ordinate structure is proposed. The compounds have been characterized by variable-temperature H-1 and P-31-{H-1} NMR spectra and T1 measurements. The reaction of molecular hydrogen with the complexes cis-[MCl2(dcpe)2] to yield trans-[MH(Cl)(dcpe)2] and cis-[MH2(dcpe)2] is also discussed
Selective hydrogenation of PhCH=CHCOMe to the unsaturated alcohol catalysed by [IrH3(PR3)3] (R = alkyl or aryl)
No full textSelective hydrogenation of benzylideneacetone (PhCH=CHCOMe) catalysed by iridiumphosphine systems prepared in situ is reported. Depending on the steric properties of the phosphine employed and the P:lr ratio, different species are formed in solution, as evidenced by n.m.r. spectroscopy. [IrH5(PR3)2] (R = alkyl or aryl) is a catalyst for the hydrogenation of the carbon-carbon double bond, whereas [IrH3(PR3)3] catalyses the reduction of the carbonyl group with a selectivity up to 100%
Iron-Catalyzed Oxidation of 1-Phenylethanol and Glycerol With Hydrogen Peroxide in Water Medium: Effect of the Nitrogen Ligand on Catalytic Activity and Selectivity
Full text linkThe iron(II) complexes [Fe(bpy)3](OTf)2 (bpy = 2,2'-bipyridine; OTf = CF3SO3) (1) and [Fe(bpydeg)3](OTf)2 (bpydeg = N4,N4-bis(2-(2-methoxyethoxy)ethyl) [2,2'-bipyridine]-4,4'-dicarboxamide) (2), the latter being a newly synthesized ligand, were employed as catalyst precursors for the oxidation of 1-phenylethanol with hydrogen peroxide in water, using either microwave or conventional heating. With the same oxidant and medium the oxidation of glycerol was also explored in the presence of 1 and 2, as well as of two similar iron(II) complexes bearing tridentate ligands, i.e., [Fe(terpy)2](OTf)2 (terpy = 2, 6-di(2-pyridyl)pyridine) (3) and [Fe(bpa)2](OTf)2 (bpa = bis(2-pyridinylmethyl)amine) (4): in most reactions the major product formed was formic acid, although with careful tuning of the experimental conditions significant amounts of dihydroxyacetone were obtained. Addition of heterocyclic amino acids (e.g., picolinic acid) increased the reaction yields of most catalytic reactions. The effect of such additives on the evolution of the catalyst precursors was studied by spectroscopic (NMR, UV-visible) and ESI-MS techniques
A HincII polymorphism at the porcine gamma-glutamyl transpeptidase (GGT) locus
No full textA HincII polymorphism at the porcine gamma-glutamyl transpeptidase (GGT) locu
A BglII polymorphism at the porcine γ‐glutamyl transpeptidase (GGT) locus
No full textA BglII polymorphism at the porcine γ‐glutamyl transpeptidase (GGT) locu
Effect of Bulky Ligands on the Hydrogenation of Olefins Catalyzed by cis-[MH2(dcpe)2] (M = Ru, Os; dcpe = 1,2-Bis(dicyclohexylphosphino)ethane)
No full textcis-[RuH2(dcpe)2] and cis-[OsH2(dcpe)2] (dcpe = Cy2PCH2CH2PCy2) behave as catalyst precursors for the hydrogenation of C = C bonds in a number of organic substrates. The ruthenium species is the more active one for the reduction of enones to saturated ketones. In contrast, the hydrogenation of unactivated olefins is faster in the presence of the osmium catalyst. Experimental evidence of the formation of the catalytically active species via dissociation of one diphosphine is obtained
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