Palladium Pallas

Tantalum (Tantalus), Niobium (Niobe), Promethium (Promethius), Uranium (Uranus), Neptunium (Neptune), Plutonium (Pluto), Palladium (Pallas), and Cerium (Ceres) are all named after mythological creatures. 

Palladium Pallas Greek Asteroid discovered in 1802. The new element was discovered in 1803... 

Palladium was named after the asteroid Pallas, which was discovered at about the same time. Pallas was the Greek goddess of wisdom. 

In 1803, in the course of his study of platinum, Wollaston isolated and identified palladium from the mother liquor remaining after platinum had been precipitated as (NH4)2PtCl6 from its solution in aqua regia. He named it after the newly discovered asteroid, Pallas, itself named after the Greek goddess of wisdom (ytaXXd iov, palladion, of Pallas). 

Palladium and platinum are the longest known and most studied of the six platinum metals [1-11], a reflection of their abundance and consequent availability. Platinum occurs naturally as the element, generally with small amounts of the other platinum metals. It was used as a silver substitute by Colombian Indians and first observed there by Ulloa (1736), who called it platina del Pinto ( little silver of the Pinto river ) but the first sample was actually brought to Europe in 1741 by Charles Wood, Assay Master of Jamaica. Palladium was isolated in 1803 by W.H. Wollaston, who was studying the aqua regia-soluble portion of platinum ores (he announced his discovery by an anonymous leaflet advertising its sale through a shop in Soho) and named it after the newly discovered asteroid Pallas [12],... 

Allegedly, the product of the reduction is a bipyridyl palla-dium(0) complex. This is not likely and our personal opinion is that the obtained material is a supported metal palladium catalyst. This is the reason why the paper was included in this review. 

The use of palladium(II) sulfoxide complexes as catalyst precursors for polymerization has met with mixed results thus a report of a palla-dium(II) chloride-dimethyl sulfoxide system as a catalyst precursor for phenylacetylene polymerization suggests similar results to those obtained using tin chloride as catalyst precursor (421). However, addition of dimethyl sulfoxide to solutions of [NH fPdCh] decreases the activity as a catalyst precursor for the polymerization of butadiene (100). Dimethyl sulfoxide complexes of iron have also been mentioned as catalyst precursors for styrene polymerization (141). 

Palladium (Pd, [Kr]4d10), name and symbol from the asteroid Pallas. Discovered (1803) by the English chemist William Hyde Wollaston. 

Anodic oxidation is used to promote the recycling of palladium(il) in the Wacker process for the conversion terminal alkenes to methyl ketones. Completion of the catalytic cycle requires the oxidation of palladium(O) back to the palla-dium(li) state and this step can be achieved using an organic mediator such as tri(4-bromophenyljamine. The mediator is oxidised at the anode to a radical-cation and... 

Furukawa et al. reported the total synthesis of murrayaquinone A (107) by a palladium(II)-mediated oxidative cyclization of the corresponding 2-arylamino-5-methyl-l,4-benzoquinones. 2-Anilino-5-methyl-l,4-benzoquinone (842) was prepared starting from 2-methyl-l,4-benzoquinone 841 and aniline 839, along with the regio-isomeric 2-anilino-6-methyl-l,4-benzoquinone (844). The oxidative cyclization of 2-anilino-5-methyl-l,4-benzoquinone (842) with stoichiometric amounts of palla-dium(ll) acetate provided murrayaquinone A (107) in 64% yield. This method was also applied to the synthesis of 7-methoxy-3-methylcarbazole-l,4-quinone (113) starting from 3-methoxyaniline (840) (623). Seven years later, Chowdhury et al. reported the isolation of 7-methoxy-3-methylcarbazole-l,4-quinone (113) from the stem bark of Murraya koenigii and named it koeniginequinone A (113) (49) (Scheme 5.101). 

In 1803 William Hyde Wollaston, a British physician who became famous for his research in metallurgy, mineralogy, and optics, succeeded in extracting a white metal from platinum. He named the new element palladium, after the asteroid Pallas, which had just been discovered the previous year. In the same year the English chemist Smithson Tennant obtained two new metals, which he named iridium and osmium, from platinum. And in 1828 the Russian chemist Karl Karlovich Klaus reported that he had obtained three new metals from platinum mined in the Urals. However, the existence of only one of them, which Klaus called ruthenium, was confirmed. 

Palladium was discovered in 1803 by W.H. Wollaston during refining and purification oP platinum metal. This new metal was found in the aqua regia extract of native platinum and was detected in solution after platinum was precipitated. It was removed as ammonium chloroplatinate. Treating this solution with mercurous cyanide precipitated a yellow palladium complex salt. The precipitate was washed and ignited to form palladium metal. Wollaston named the element palladium after the newly discovered asteroid Pallas. 

But not only palladium(O) complexes can activate CO or O2, also palla-dium(II) complexes have been reported to be active in the presence of carbon monoxide or dioxygen as it was shown in the direct synthesis of polycarbonate from CO and phenol or bisphenol A [79,80]. The authors could confirm the positive influence of the NHC ligand comparing the activity and reactivity of the palladium-carbene complex with the corresponding PdBr2 catalyst. The molecular weights and yields of the polycarbonates improved with increasing steric hindrance of the substituents in the l,T-position of the car-bene complex. 

In 1803 Dr. Wollaston succeeded in separating two new metals from platinum. He dissolved the crude metal in aqua regia, evaporated off the excess acid, and added a solution of mercuric cyanide, drop by drop, until a yellow precipitate appeared. When this substance was washed and ignited, a white metal remained. By heating the yellow precipitate with sulfur and borax he also succeeded in obtaining a button of the new metal, which he named palladium in honor of the recently discovered asteroid, Pallas (6). 

The previous extension of solvent mixtures involved solvent interfaces. This organic-water interfacial technique has been successfully extended to the synthesis of phenylacetic and phenylenediacetic acids based on the use of surface-active palla-dium-(4-dimethylaminophenyl)diphenylphosphine complex in conjunction with dode-cyl sodium sulfate to effect the carbonylation of benzyl chloride and dichloro-p-xylene in a toluene-aqueous sodium hydroxide mixture. The product yields at 60°C and 1 atm are essentially quantitative based on the substrate conversions, although carbon monoxide also undergoes a slow hydrolysis reaction along with the carbonylation reactions. The side reaction produces formic acid and is catalyzed by aqueous base but not by palladium. The phosphine ligand is stable to the carbonylation reactions and the palladium can be recovered quantitatively as a compact emulsion between the organic and aqueous phases after the reaction, but the catalytic activity of the recovered palladium is about a third of its initial activity due to product inhibition (Zhong et al., 1996). 

In the course of investigating the production of platinum from its ores, Wollaston and Tennant found four new elements in 1803. Tennant isolated osmium and iridium Wollaston found rhodium and palladium. As was the contemporary habit, Wollaston named the latter after a newly discovered celestial body. Uranium gained its name this way after William Herschel s discovery of the planet Uranus, and palladium honoured the asteroid Pallas, found in 1802. 

Although the fate of the zinc ligands was not unambiguously ascertained, it appeared clearly that palladium to zinc transmetallation occurred prior to cyclization. Indeed, palla-dium-ene reactions are known but generally require higher temperatures and, when run in association with a subsequent Stille cross-coupling, trans- 1,2-disubstituted cyclopentanes were generated (equation 81)115,116. 

Polystyrene-bound secondary aliphatic amines and /V-alkyl amino acids can be ally-lated by treatment with a diene and an aryl iodide or bromide in the presence of palla-dium(II) acetate (Entry 14, Table 10.3). As the diene, 1,3-, 1,4-, and 1,5-dienes can be used, and, besides aryl halides, heteroaryl bromides have also been successfully used [63], This remarkable reaction is likely to proceed via the formation of an aryl palladium complex, with subsequent insertion of an alkene into the C-Pd bond. The resulting organopalladium compound does not undergo ( -elimination (as in the Heck reaction), but isomerizes to an allyl palladium complex, which reacts with the amine to give the observed allyl amines. 

Di-jjL-carbonylhexacarbonyldicobalt, 99 Dichlorobis(triphenylphosphine)palla-dium(II), 103 Iron carbonyl, 152 Palladium(II) chloride-Copper(II) chloride, 235... 

Cross-coupling of two vinyl groups Dichlorobis(triphenylphosphine)pal-ladium(II), 103 Palladium(II) acetate, 232 Tetrakis(triphenylphosphine)palla-dium(0), 289... 

Palladium(II) trifluoroacetate, 236 Sodium borohydride-Tetrakis(tri-phenylphosphine)palladium(O), 168 Tetrakis(triphenylphosphine)palla-dium(0), 34, 103, 126, 142, 169, 202, 211, 220, 271, 289 Tetrakis(triphenylphosphine)palla-dium(0)-l, 2-Bis(diphenylphos-phine)ethane, 290 Tetrakis(triphenylphosphine)palla-dium(0)-Zinc, 346 Tributyltin hydride-Dichlorobis-(triphenylphosphine)palladium(II), 319... 

Researchers at NASA (National Aeronaulics and Space Administration. Cleveland. Ohio) tested a large number of alloys, such as irun-chromium-aluminum. platinum-tungsten, platinum-palladium-molybdcnum, and palla... 

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