Palladium selenides

Madhu, Singh RN (2011) Palladium selenides as active methanol tolerant cathode materials for dnect methanol fuel cell. Int J Hydrogen Energy 36(16) 10006-10012... 

These results strongly suggest that pyridine acts as a suitable ligand for an active palladium intermediate. In the absence of pyridine, palladium selenide [Pd(SePh)2] molecules, a key species for this hydroselenation of alkynes, easily react with each other by the coordination of the selenide ligand to the other palladium center to form polymerized complex, which is insoluble in usual organic solvent and loses the catalytic activity. Therefore, pyridine is considered to inhibit the polymerization and protect the catalyst from the poisoning [23]. 

Selenium occurs in the slimes as intermetallic compounds such as copper silver selenide [12040-91 -4], CuAgSe disilver selenide [1302-09-6], Ag2Se and Cu2 Se [20405-64-5], where x < 1. The primary purpose of slimes treatment is the recovery of the precious metals gold, silver, platinum, palladium, and rhodium. The recovery of selenium is a secondary concern. Because of the complexity and variabiUty of slimes composition throughout the world, a number of processes have been developed to recover both the precious metals and selenium. More recently, the emphasis has switched to the development of processes which result in early recovery of the higher value precious metals. Selenium and tellurium are released in the later stages. Processes in use at the primary copper refineries are described in detail elsewhere (25—44). 

Cinnamyl phenyl selenide, 79 Tetrakis(triphenylphosphine)-palladium(O), 289 Vinyltrimethylsilane, 343 Allylic ethers... 

Complex Compounds of Platinum and Palladium Halides with Dialkyl Selenides.6... 

Diphenyl selenide is a colourless, strongly refractive oil, B.pt. 167° C. at 16-5 mm. insoluble in water but miscible with alcohol or ether in all proportions. It has a faint odour, and a density of 1 3712 at 0° C., 1 3561 at 15 2° C., and 1 350 at 20° C. With cold bromine in ether solution it yields the dibromide. Diphenyl selenide, unlike dimethyl selenide, does not combine with alkyl iodides, and in this respect it resembles diphenyl sulphide.2 When heated nearly to its boiling-point with sulphur it gives diphenyl sulphide, the reaction being practically quantitative at 300° C.3 With palladium chloride it forms the complex PdCl2.2(C6H5)2Se, orange-red needles, M.pt. 181° to 182° C.4... 

The cyclofunctionalization of cyclohexa-2,4-dieneacetic acids results in 1,4-addition to form c/s-fused 7-lactones, as shown in equation (13) and Table 4. Most reaction conditions gave products with the electrophile trans to the lactone ring (entries 1-4), but the stereochemistry of the palladium-catalyzed reaction was reversed if an excess of a complexing ligand was added to the reaction (entries 5 and 6).49>s0 Results of lactonization in cyclohepta-2,4-dieneacetic acid systems were similar, but selenolactonization produced 1,2-addition products under some conditions.31 It is possible that these products result from a 1,3-rearrangement of the initial allyl selenide.52... 

Allylic metals, in propargylic alcohol alkylation, 11, 129 ir-Allylic palladium complexes, and carbocyclization, 11, 426 Allylic position, alkenes, dienes, polyenes, metallation, 9, 6 Allylic selenides, [2,3]sigmatropic rearrangement, 9, 481 Allylic substitution reactions for C-N bonds via amination... 

There is a substantial body of literature on the palladium- and nickel-catalyzed formation of aryl sulfides, selenides, and phosphines from aromatic and heteroaromatic halides. Progress on these reactions has continued with several recent contributions [47-50]. A review in 1997 covered the types of transformations that can be conducted and the types of catalysts used [51]. Particularly useful examples are the conversions ofbinaphthol to binaphthylphosphines... 

Trialkylboranes were converted into alkyl phenyl selenides and alkyl phenyl tellurides by reactions with PhSeSePh and PhTeTePh in the presence of stoichiometric amounts of air.550 Vinyl selenides and tellurides were synthesized by treating vinylboronic acids or esters with phenylselenyl chloride in ionic liquids (Equation (114))551 or by palladium-catalyzed coupling reaction of diorgano ditellurides (Equation (115)).552... 

Selenium analogs of the mercury and palladium complexes are known, but no simple selenide complexes seem to have been reported. 

The above proportions of palladium and gold correspond to the formula PdAus. A natural selenide of palladium, Eugenesite or selen-palladium, has been described 3 as a silver-white, hard, crystalline alloy, which can be readily melted. 

Palladous Selenide, PdSe.—Berzelius found that palladium and selenium unite to form a refractory, grey selenide when heated together, their union being accompanied with evolution of heat. 

The first synthesis of (R)-4,5-dihydro-37/-dinaphtho[2,l-f l, 2 -i ]selenepin oxide 110 has been achieved from (R)-(+)-l,l -bi-2-naphthol, which in turn was obtained by resolution of raol,l -bi-2-naphthol. Palladium-catalyzed alkoxy carbonylation of the alcohol 108 gave a dimethyl ester which was then reduced by LiAlfLi, and the resultant diol converted to key intermediate chloride 109. Cyclization with sodium selenide gave a novel enantiomerically pure selenide, which upon oxidation yielded the desired selenoxide 110 <2000SC2975>. 

It has been reported that, in the presence of a palladium catalyst, diphenyl diselenide and samarium diiodide react with allylic acetates to give allylic phenyl selenides under mild conditions (Scheme 12) [18]. In this case, however, the nucleophilic benzeneselenolate was not proposed as an intermediate of the reaction. 

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