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Showing papers on "Palladium published in 1986"


Journal ArticleDOI
TL;DR: The cross-coupling of organotin reagents with a variety of organic electrophiles, catalyzed by palladium, provides a novel method for generating a carbon-carbon bond.
Abstract: The cross-coupling of organotin reagents with a variety of organic electrophiles, catalyzed by palladium, provides a novel method for generating a carbon-carbon bond. Because this mild, versatile reaction is tolerant of a wide variety of functional groups on either coupling partner, is stereospecific and regioselective, and gives high yields of product, it is ideal for use in the synthesis of elaborate organic molecules. When the coupling reaction is carried out in the presence of carbon monoxide, instead of a direct coupling, carbon monoxide insertion takes place, stitching the two coupling partners together and generating a ketone.

2,991 citations


Journal ArticleDOI
TL;DR: A mixture of palladium and magnesium nitrates was found to be a very powerful modifier for the determination of As, Bi, In, Pb, Sb, Se, Sn, Te and Tl in graphite furnace atomic absorption spectrometry as mentioned in this paper.

313 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the kinetics of hydrodechlorination of chlorobenzene over Pd Al 2 O 3 and Rh Al 2O 3 catalysts of varying dispersion and proposed a reaction scheme which is formally analogous to the Mars-van Krevelen mechanism for the oxidation of hydrocarbons.

287 citations


Journal ArticleDOI
TL;DR: In this paper, des calculs ab initio sur les complexes MR 2 (M=Pd ou Pt R=H ou CH 3 ) pour modeliser des copulatures reductives concertees a partir de complexes MR2 L 2 (ou L est une phosphine)

210 citations



Journal ArticleDOI
TL;DR: In this paper, the authors investigated the hydrogenation of CO2 over Pd supported by A12O3, TiO2, SiO2 and MgO in a flow technique at 1 and at 9.5 atm.

182 citations



Journal ArticleDOI
TL;DR: Phenols can be selectively deoxygenated by reduction of the corresponding aryl triflates with triethylammonium formate in the presence of a homogeneous palladium catalyst as discussed by the authors.

162 citations



Journal ArticleDOI
TL;DR: In this article, the reactions des cis-and trans-acetates des phenyl-4 butene-3ol-2 and phenyl -1 butene 2ol-1 avec le sodiomalonate de dimethyle, l'acetylacetonate de sodium and le sodioacetylacetate de methyle en presence d'un catalyseur au palladium.
Abstract: Etude des reactions des cis- et trans-acetates des phenyl-4 butene-3ol-2 et phenyl-1 butene-2ol-1 avec le sodiomalonate de dimethyle, l'acetylacetonate de sodium et le sodioacetylacetate de methyle en presence d'un catalyseur au palladium

151 citations


Journal ArticleDOI
TL;DR: Automobile catalytic converters apparently release significant quantities of platinum and palladium to the roadside environment, which may wash this concentrate into local water systems or the ocean.
Abstract: Automobile catalytic converters apparently release significant quantities of platinum and palladium to the roadside environment. Dust samples collected from broad-leaved plants contained as high as 0.7 ppm of platinum and 2.5 times less palladium. Rains may wash this concentrate into local water systems or the ocean. 8 references, 1 table.

Journal ArticleDOI
TL;DR: In this paper, a three-component system comprised of a soluble palladium catalyst, hydridosilane, and zinc chloride is capable of efficient conjugate reduction of a,&unsaturated ketones and aldehydes.
Abstract: A three-component system comprised of a soluble palladium catalyst, hydridosilane, and zinc chloride is capable of efficient conjugate reduction of a,&unsaturated ketones and aldehydes. The optimal set of conditions includes diphenylsilane as the most effective hydride donor, any soluble palladium complex in either the 0 or I1 oxidation state, when it is stabilized by phosphine ligands, and ZnCll as the best Lewis acid cocatalyst. The reaction is very general with respect to a broad range of unsaturated ketones and aldehydes, and it is highly selective for these Michael acceptors, as reduction of a,@-unsaturated carboxylic acid derivatives is very sluggish under these conditions. When dideuteriodiphenylsilane is used to reduce unsaturated ketones, deuterium is stereoselectively introduced at the less-hindered face of the substrate and regioselectively at the 8-position. Conversely, when reductions are carried out in the presence of traces of D20, deuterium incorporation occurs at the a-position. On the basis of deuterium-incorporation experiments and 'H NMR studies, a catalytic cycle is postulated in which the first step involves reversible coordination of the palladium complex to the electron-deficient olefin and oxidative addition of silicon hydride to form a hydridopalladium olefin complex. Migratory insertion of hydride into the coordinated olefin produces an intermediate palladium enolate which, via reductive elimination, collapses back to the Pd(0) complex and a silyl enol ether, which is then hydrolyzed to the saturated ketone. In addition to catalyzing that hydrolysis, ZnC12 facilitates the hydrosilation process. Despite the bewildering variety of reducing agents available for synthetic chemistry, new and ever more selective reductants are in constant demand. Most popular of selective reducing agents are the various metal hydrides, mainly those of boron and alu- minum,' an abundance of which have been designed over the past 4 decades and new derivatives of which are continuously being developed.* However, the hydridic nature of most of these group 13 and other metal hydrides can limit their usefulness, particularly when high chemoselectivity is required.


Journal ArticleDOI
TL;DR: Palladium-catalyzed reaction of phenyl fluoroalkanesulfonates with alkynes and alkens under mild conditions gives the corresponding alkynyl and alkenyl substituted benzenes in good yields as mentioned in this paper.

Journal ArticleDOI
TL;DR: Cyanuration d'iodo- (iodo halogeno)- et diiodobenzenes et de l'iodon-4 benzoate de methyle dans la triethylamine as mentioned in this paper.
Abstract: Cyanuration d'iodo- (iodo halogeno)- et diiodo-benzenes et de l'iodo-4 benzoate de methyle dans la triethylamine

Journal ArticleDOI
TL;DR: In this article, the reaction products are benzene from cyclotrimerization, ethylene from hydrogenation, and hydrogen from decomposition on palladium single crystals in ultrahigh vacuum (UHV) and at atmospheric pressures (10/sup -1/-1 atm).
Abstract: Acetylene cyclotrimerizes to form benzene on palladium single crystals in ultrahigh vacuum (UHV) (10/sup -12/-10/sup -8/ atm) and at atmospheric pressures (10/sup -1/-1 atm). The reaction is structure sensitive in both pressure regimes. In UHV the (111) face is the most active followed by the (110) and then the (100) surfaces. At high pressure the (111) and (100) surfaces have equal catalytic activity whereas the (110) face is one-fourth as active. In UHV the reaction products are benzene from cyclotrimerization, ethylene from hydrogenation, and hydrogen from decomposition. At high pressures only benzene was detected. The high-pressure catalytic reaction proceeds on the bare metal surface. The reaction also proceeds readily on Pd films and Pd supported on alumina.

Journal ArticleDOI
TL;DR: In this article, a general synthesis of heterobioaryls in good to excellent yields via Pd-catalyzed cross-coupling of trialkylheteroarylstannanes 1-5 with aryl halides is described.

Journal ArticleDOI
TL;DR: Tetrakis(triphenylphosphine)palladium(0) catalyses the cis-addition of hexaalkylditins R6Sn2 (R = Me, Et, Bu) to acetylene and 1-alkynes; however, the reaction is not quantitative.



Book ChapterDOI
TL;DR: In this paper, the authors describe the hydrogenation of nitriles, which is a complicated process, owing to the existence of reactive intermediates comprising several consecutive and competitive reactions of different characters.
Abstract: Publisher Summary This chapter describes the hydrogenation of nitriles, which is a complicated process, owing to the existence of reactive intermediates comprising several consecutive and competitive reactions of different characters. Some of them are typical hydrogenation reaction promoted by metallic hydrogenation catalysts; others are condensation reactions of acid-base character. The active centers for the hydrogenation and condensation reactions are localized on the surface of the metallic component of the catalyst, and the type of metal used is decisive for the catalyst properties. By changing the reaction conditions the relationships between the rates of hydrogenation and condensation can be influenced and thus the composition of the reaction product can be varied. The net result under the actual reaction conditions employed depends on the type of catalyst and/or on the experimental arrangement. The individual catalysts differ in their responses to a change in reaction conditions, and very often contradictory results are encountered. Addition of ammonia enhances the content of primary amines in hydrogenations catalyzed by nickel or cobalt, promotes the formation of secondary amines on copper catalysts under certain conditions and leads to an increased yield of tertiary amines in hydrogenations catalyzed by platinum or palladium.

Journal ArticleDOI
TL;DR: In this article, the selective photoreduction and recovery of precious metals from a dilute solution (as might be found in industrial wastes) have been investigated for a mixture of gold(III), platinum(IV), and rhodium(III) chloride salts as a function of various parameters (pH, presence or absence of O/sub 2/, presence or presence of a hole scavenger, and the concentration of the semiconductor).
Abstract: Irradiation of aqueous TiO/sub 2/ dispersions containing palladium(II) or rhodium(III) chloride salts with AM1 simulated sunlight leads to the photoreduction of these metals, which are deposited on the semiconductor particle surface. Oxygen is detrimental to the photoreduction of rhodium(III) but not the photoreduction of palladium(II). However, in both cases the reduction process is most efficient if the solution contains CH/sub 3/OH, which acts to scavenge valence band holes of the illuminated TiO/sub 2/ semiconductor. The selective photoreduction and recovery of precious metals from a dilute solution (as might be found in industrial wastes) have been investigated for a mixture of gold(III), platinum(IV), and rhodium(III) chloride salts as a function of various parameters (pH, presence or absence of O/sub 2/, presence or absence of a hole scavenger, and the concentration of the semiconductor). At pH 0, gold is easily separated from platinum and rhodium. The rate of photoreduction of gold(III) on TiO/sub 2/ is nearly independent of the concentration of the semiconductor, under the experimental conditions employed; the limiting rate is 2.7 x 10/sup -7/ M s/sup -1/. The potential utility of this selective photochemical technique is discussed.

Journal ArticleDOI
TL;DR: In this paper, Silyl enol ethers and ketene silyl acetates derived from ketones are converted into α,β-unsaturated ketones by reaction with allyl carbonate in acetonitrile using the palladium complex and tributyltin methoxide as bimetallic catalysts.

Journal ArticleDOI
TL;DR: By the palladium catalysis 2-carboethoxyethylzinc iodide reacts with aryl iodides and vinyl iodides or triflates to provide the coupling products (ethyl 3-arylpropionates and ethyl 4-pentenoates, respectively) in satisfactory yields.

Journal ArticleDOI
TL;DR: X-ray photoelectron spectra of several Palladium fluorine compounds have been investigated in this article, and the results clearly confirm the unusual +III oxidation State of Palladium in NaPdF4, Na3pdF6, K3Pd F6, and K2NaPdrF6.
Abstract: X-ray photoelectron spectra of several Palladium fluorine compounds have been investigated. In all these phases Palladium atoms have a more or less distorted octahedral coordination. Satellite Structures generally occur in Pd 3d3/2 and Pd 3d5/2 levels and broad F 1s peaks are observed. Shifts in binding energies can be correlated with Palladium oxidation State and covalency. XPS results clearly confirm the unusual +III oxidation State of Palladium in NaPdF4, Na3PdF6, K3PdF6, and K2NaPdF6.

Journal ArticleDOI
TL;DR: In this article, stable sols of ruthenium, rhodium, palladium, platinum, silver, and gold were prepared from aqueous solutions of the corresponding noble metal salts by reduction with sodium borohydride in the presence of three different types of surfactants, stearyltrimethylammonium chloride (SC), sodium dodecylbenzenesulfonate (SD), and polyethylene glycol mono-p-nonylphenyl ether (PN).



Journal ArticleDOI
TL;DR: Preparation d'homopolymeres de faibles masses moleculaires du m-bromophenylacetylene ainsi que de copolymeres et reseaux de benzenes di- et triethynyl avec des di- and tribromobenzenes par une reaction de couplage utilisant un sel de Pd(II), la triphenylphosphine et l'iodure cuivreux comme catalyseur.
Abstract: Preparation d'homopolymeres de faibles masses moleculaires du m-bromophenylacetylene ainsi que de copolymeres et reseaux de benzenes di- et triethynyl avec des di- et tribromobenzenes par une reaction de couplage utilisant un sel de Pd(II), la triphenylphosphine et l'iodure cuivreux comme catalyseur

Journal ArticleDOI
TL;DR: In this paper, the reactivite relative d'acetates allyliques and propargyliques vis-a-vis de substitutions par des nucleophiles divers catalysees par le palladium.
Abstract: Etude de la reactivite relative d'acetates allyliques et propargyliques vis-a-vis de substitutions par des nucleophiles divers catalysees par le palladium