1,721,286 research outputs found
Eterogeneità culturale e spazi pubblici in un distretto industriale: il Macrolotto 0 di Prato come zona di transizione
No full textSELECTIVE OXIDATION OF ALKANES AND ETHERS MEDIATED BY RUTHENIUM(II) COMPLEXES
No full textSelective hydroxylation (or ketonization) of cyclic alkanes and conversion of ether to esthers and of secondary alcohols to ketones, with significant rates (up to ca. 1 turnover per minute at room temperature), were achieved by using hypochlorite as oxidant and a choice of ruthenium (II) complexes as catalysts, in a biphasic water-dichloromethane system
Alkene epoxidation by ruthenium(II) phosphino–complexes. A kinetic investigation.
No full textCoordinatively unsaturated complexes of ruthenium(I1) of the type [RUCI(LL)~]+w,h ere LL is 1,3-bis(diphenylphosphino)propane
or l-(diphenylphosphino)-2-(2-pyridyl)ethane, effectively promote the epoxidation of olefins in the presence of iodosylbenzene
and in low-coordinating media. Competition from oxidative cleavage and/or allylic oxidation is observed with some olefin. The
kinetics of the epoxidation of 1-octene, trans-2-octene, cyclooctene, norbornene, styrene, trans-@-methylstyrenea, nd cis- and
trans-stilbene have been investigated gas chromatographically, and the following conclusions are drawn. (i) The reaction order
in the catalyst is 1; (ii) the reaction order in the olefins varies between 0 and 1; (iii) rates are different from each olefin examined.
It is suggested that the rate-determining step consists in the breakdown of an oxo-metal intermediate containing the olefin. KM
and V ,val ues are calculated from the Michaelis-Menten equation, indicating that the relative reactivity of olefins toward catalytic
epoxidation falls into a relatively narrow range. Competition experiments have been performed that confirm the KM data obtained
by the Lineweaver-Burk analyses. Stereospecific epoxidation is achieved with trans-olefins (stilbene, 2-hexene, and 2-octene),
whereas the corresponding cis-olefins produce high yields of trans-epoxides, pointing to a substantially radicaloid character of
the reaction intermediate
Pentaphosphine-complexes of cobalt (II) and hydropentaphosphine- complexes of cobalt (III) with secondary phosphines
No full textHYPOCHLORITE-OXYFUNCTIONALIZATION OF SATURATED-HYDROCARBONS CATALYZED BY RUTHENIUM(II) COMPLEXES
No full textHydroxylation or ketonization of alkanes is achieved using lithium or sodium hypochlorite in the presence of catalytic amounts of ruthenium(II) complexes in a biphasic dichloromethane-water system, at room temperature. The oxidation of cyclooctane is first order both in substrate and in catalyst: a kinetic isotope effect (k(H)/k(D)) = 5.6 was measured using cyclohexane-d12. A discussion is included concerning the origin of the different regioselectivities
Cyanide complexes of cobalt (II) and cobalt (I) with 1,2 -bis (diphenylphosphino) ethane
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