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Dialkyl sulfides palladium

Even for palladium, contact times of at least 1 h are needed for these reactions to proceed substantially to completion, and the dialkyl sulfide extraction process is operated in a batch, rather than continuous, mode to accommodate this requirement. Gold(III), unless removed previously, is also extracted by dialkyl sulfides in the form of the complex AuC13(R2S), and silver(I) can be extracted from nitrate solutions as the complex AgN03(R2S)2.228... [Pg.807]

The back-extraction (stripping) of palladium is achieved in the hydroxyoxime process by contacting the loaded organic phase with a concentrated solution of hydrochloric acid (about 6 M), thus causing the reversal of reaction (76). Palladium can be recovered from the strip liquor by the addition of ammonia, and the precipitated Pd(NH3)2Cl2 can be calcined to yield pure palladium metal. In the dialkyl sulfide process, however, the extraction reaction (75) is independent of acidity, and is therefore reversed by the use of aqueous ammonia, which forms a stable cationic complex with palladium(II) ... [Pg.807]

The mechanism of this process has been investigated [9]. The reaction exhibits the features of electrophilic substitution electron-releasing substituents in the aromatic nucleus accelerate the metalation. Usually a-aryl complexes of palladium(ll) are not stable and cannot be isolated. However, dialkyl sulfides stabilize the complexes which can be isolated as yellow crystals [10] ... [Pg.323]

Diagnostic imaging techniques non-invasive gamma rays, 965 Dialkyl sulfides solvent extraction gold and silver, 807 palladium, 807 Diamines cobalt catalysts hydrogenation, 237 ligands... [Pg.7189]

Although adsorbed molecules of extractants are well oriented at the interface, the interfacial reactions occur more slowly, as recalculated for the same volume, than reactions in the aqueous phase. The extraction of palladium(II) from HCl solutions with dialkyl sulfides is a classic example of a very slow process. Modifying the extractant structure by adding a hydrophilic hydroxyl group and/or a phase transfer catalyst, e.g., trialkylamine or quaternary ammonium salt, increases the rate of extraction. The addition of sulfonic and phosphoric acids to hydroxyoximes may enhance the rate of copper extraction due to the formation of reverse micelles and the development of the microscopic interface. The a-acyloin oximes that form an intermediate complex that has a five-member ring with copper(II) increase the rate of extraction of aromatic hydroxyoximes. The addition of surfactants may cause both retardation and acceleration of extraction. If the interfacial tension is decreased, surfactants cause an increase in the interfacial surface area in dispersed systems. When they adsorb at the interface, they cause an additional... [Pg.1175]

Evidence for the intermediacy of a-arylpalladium acetate complexes c was provided by the isolation of their trinuclear dialkyl sulfide adducts [11]. The two following steps, insertion of the alkene 4 and )8-hydride elimination, correspond to the classical Mizoroki-Heck reaction pathway. The resulting palladium(0) species, which is likely to be stabilized in the form of a hydridopalladium carboxylate e, is then reoxidized by molecular oxygen to the initial palladium(II) acetate (a) under liberation of water. The precise mechanism of this reoxidation is not yet fully understood, but it seems that, at elevated oxygen pressures, it is not rate-determining even in the absence of promoters. Mechanistic studies by Jacobs and coworkers [10] indicate that the beneficial effect of adding transition metal salts, originally intended to facilitate this oxidation step, in fact arises from an acceleration... [Pg.165]

Fuchita, Y, Hiraki, K., Kamogawa, Y. et al. (1989) Activation of aromatic carbon-hydrogen bonds by palladium(II) acetate-dialkyl sulfide systems. Formation and characterization of novel diphenyltripalladium(Il) complexes. Bull. Chem. Soc. Jpn., 62, 1081-5. [Pg.177]

Palladium and platinum - Dialkyl sulfides, tributyl phosphate and alkyl amines have been used for extracting these metals. [Pg.71]

Dialkyl and diaryl sulfoxides were reduced (deoxygenated) to sulfides by several methods. As a little surprise sulfides were obtained from sulfoxides by catalytic hydrogenation over 5% palladium on charcoal in ethanol at 80-90° and 65-90 atm in yields of 59-99% [684. In the case of p-tolyl -styryl sulfoxide deoxygenation was achieved even without reduction of the double bond giving 66% of p-tolyl -styryl sulfide and only 16% of p-tolyl -phenyl-ethyl sulfide [684],... [Pg.88]

Palladium-catalyzed cross-coupling reactions of diaryliodonium tetrafluo-roborates have recently been employed for conversions of mercaptans to aryl-and diaryl sulfides, sodium arenesulfinates to diaryl sulfones, and dialkyl phosphites to aryl phosphonates (Scheme 43) [120-122]. [Pg.154]


See other pages where Dialkyl sulfides palladium is mentioned: [Pg.175]    [Pg.175]    [Pg.120]    [Pg.807]    [Pg.807]    [Pg.6952]    [Pg.445]    [Pg.183]    [Pg.93]    [Pg.205]    [Pg.874]    [Pg.105]    [Pg.459]   
See also in sourсe #XX -- [ Pg.807 ]

See also in sourсe #XX -- [ Pg.807 ]

See also in sourсe #XX -- [ Pg.6 , Pg.807 ]




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