Showing papers on "Palladium published in 1977"

Selective carbon-carbon bond formation via transition metal catalysis. 3. A highly selective synthesis of unsymmetrical biaryls and diarylmethanes by the nickel- or palladium-catalyzed reaction of aryl- and benzylzinc derivatives with aryl halides

Abstract: Organozinkchloride (I) und Arylhalogenide (II) reagieren in Gegenwart von Ni- oder Pd-Katalysatoren wie (VI) oder (VII) zu den Kupplungsprodukten (III).

Reactions of allyltin compounds iii. allylation of aromatic halides with allyltributyltin in the presence of tetrakis(triphenylphosphine)palladium(o)

Abstract: Catalytic allylation of aryl halides with allyltributyltin in the presence of tetrakis(triphenylphosphine)palladium(O) was investigated. The reaction with aryl bromides proceeded efficiently to yield allylbenzenes.

Palladium Alloys for Hydrogen Diffusion Membranes

Abstract: Palladium holds a unique position among the metallic elements in being able to take into solution large quantities of hydrogen while simultaneously retaining a high degree of ductility. These attributes coupled with the high mobility or rate of diffusion of hydrogen in the lattice have been exploited in the use of palladium and subsequently of palladiumbased alloys as hydrogen diffusion membranes. Earlier articles in this Journal (I, 2) have described the application of this principle to commercial diffusion units for the production of high purity hydrogen, and more recently to a hydrogen generator for military requirements (3). In these applications the permeability of the palladium alloy to all other gases at the operating temperatures is so low as to be negligible in practice, and the alloy therefore functions as a highly specific filter for the production of ultra-pure hydrogen, or for removing hydrogen from mixed process gases. A limitation to the use of pure palladium for hydrogen diffusion has its basis in the pressure-concentration isotherms for the palladium-hydrogen system shown in Figure I (4). At temperatures below 300°C and pressures below 20 atm, increasing the hydrogen concentration leads to the formation of the p phase which can coexist with the 01 phase. The (3 phase has a considerably expanded lattice compared with u, for example a hydrogen/palladium ratio of 0.5 results in an expansion of about 10 per cent by volume. Nucleation and growth of the in the a matrix therefore sets up severe strains in the material resulting in distortion, dislocation multiplication and hardening. After a few hydrogenation/dehydrogenation cycles splitting of the diffusion membrane may occur. One method whereby the phase change can be avoided is to ensure that the palladium diffusion membrane is always operated in the single phase region of the Pressure-Composition-Temperature diagram (5). This may be achieved by maintaining the temperature above the critical value of 300°C as long as the membrane is in a hydrogen atmosphere, or by ensuring that cooling is allowed only when it is in a dehydrogenated condition with the hydrogen pumped from the system. Such expedients do not, of course, avoid the volume changes that inevitably occur, but in a single phase region the composition varies smoothly and the distortion phenomena associated with nucleation and growth are circumvented. With these limitations in mind it is nevertheless possible to operate pure palladium membranes successfully for the large scale separation of hydrogen from mixed gases. Diffusion installations in the Union Carbide Corporation with individual outputs of 9 million cu ft/day have been described (6).

Reaction of diazonium salts with transition metals. i. arylation of olefins with arenediazonium salts catalyzed by zero valent palladium

Abstract: Various olefins, especially those bearing electron donating groups, were successfully arylated by arenediazonium salts in the presence of a catalytic amount of palladium(O) complexes. An arylpalladium species was supposed to be an intermediate in this reaction.

Alkylation, arylation, and vinylation of acyl chlorides by means of organotin compounds in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium(o)

Abstract: Alkylation, arylation, and vinylation of acyl chlorides by means of organotin compounds in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium(O) were demonstrated. The corresponding ketons were obtained in fairly good yields.

Synthesis of ethylene, cyclo-octa-1,5-diene, bicyclo[2.2.1]heptene, and trans-cyclo-octene complexes of palladium(0) and platinum(0); crystal and molecular structure of tris(bicyclo[2.2.1]heptene)platinum

Abstract: Reaction of [Pt(1,5-C8H12)Cl2] with Li2(C8H8) in diethyl ether in the presence of excess of 1,5-C8H12 gives the white crystalline complex [Pt(1,5-C8H12)2] in good yield. A similar reaction of [Pd(1,5-C8H12)Cl2] in the presence of propene affords [Pd(1.5-C8H12)2]. stable below ambient temperatures. The reaction of [M(1,5-C8H12)Cl2](M = Pd or Pt) with Li2(C8H8) and excess of bicyclo[2.2.1]heptene gives, respectively, tris(bicyclo[2.2.1]heptene)- palladium and -platinum. These complexes are also obtained by displacement of cyclo-octa-1,5-diene from [M(1,5-C8H12)2](M = Pd or Pt) by bicyclo[2.2.1]heptene. Related displacement reactions with trans-cyclo-octene and ethylene afford, respectively, tris(trans-cyclo-octene)palladium, tris(trans-cyclo-octene)platinum. tris(ethylene)palladium, and tris(ethylene)platinum. The ethylene complexes are highly volatile, and can be isolated as crystalline species, although they readily deposit the metals. The structural identity of tris(bicyclo-[2.2.1]heptene)platinum has been established by analysis of single-crystal X-ray data recorded on a four-circle diffractometer both at room temperature and at 190 K. The complex is orthorhombic, space group P212121. Z= 4, a= 5.717(1), b= 10.735(4), c= 28.749(12)A, at 300 K: at 190 K a= 5.598(6), b= 10.775(16), c= 28.562(40)A. Full-matrix least-squares refinement, using 1 781 reflections, has converged to R 0.056 (R′ 0.066)(190 K data). The molecule has a trigonal-planar structure in which the maximum deviation from planarity is 0.03 A.

Reduction of nitro-compounds

Abstract: Nitro-compounds were reduced to amines in high yields by using palladium, platinum, or rhodium metal catalyst with formic, phosphinic, or phosphorous acid. With formic acid, nitro-compounds containing fluorine were reduced but not those containing chlorine, bromine, or iodine. With the other acids, nitro-compounds containing any of the halogens were reduced with retention of the halogen.

Thermodynamics of hydrogen dissolved in palladium/rhodium and palladium/platinum alloys

Abstract: Partial thermodynamic parameters have been determined for the solution of hydrogen in Pd/Pt and Pd/Rh alloys. The partial excess entropies of absorption of hydrogen at infinite dilution decrease regularly with atom fraction platinum but not with atom fraction rhodium. This suggests that interstices are not excluded for hydrogen occupation by rhodium atoms neighbouring the interstices but are excluded by the platinum nearest neighbours. Other thermodynamic parameters for hydrogen absorption have been determined and are compared for these alloys. These results are discussed in terms of the observation that rhodium will absorb hydrogen at high pressures of hydrogen when situated within the palladium lattice whereas platinum will not.

Radiometric Determination of Platinum and Palladium Attrition from Automotive Catalysts

Abstract: Automotive exhaust gas catalysts contain platinum and palladium as the active material on an alumina substrate. The loss rate of the active material from the catalyst under vehicle operating conditions was determined with a radiometric method in which radioactive platinum and palladium were used as tracers. Experiments with a commercial catalyst made radioactive by irradiation in a nuclear reactor indicated that a maximum of about 6 percent of the active material would be lost from the catalyst in 80,000 km. Experiments with a laboratory prepared catalyst containing 195mPt and 103Pd indicated that about 10 percent of the active material lost was water soluble, possibly in the form of halides.

Low cost method for forming elevated metal bumps on integrated circuit bodies employing an aluminum/palladium metallization base for electroless plating

Abstract: Elevated metal contact bumps are provided on a microelectronic semiconductor circuit, with the use of aluminum-palladium metallization as a base for selective electroless plating. The aluminum and palladium are preferably deposited sequentially in a single operation, i.e., without exposing the aluminum surface to the atmosphere. The aluminum-palladium film is then patterned in a single step, using an etchant which attacks both metals at substantially the same rate. The metal pattern is then covered with an insulation layer wherein apertures are opened to expose palladium at selected sites for immersion in an electroless plating bath of ionic Cu or Ni for bump formation.

The effect of the α-β phase change on the α phase solubility of hydrogen in palladium

Abstract: Following the α-β phase change in palladium, there is an enhanced solubility of hydrogen at a given equilibrium pressure within the low hydrogen content α phase. There are marked similarities between the absorption isotherms for hydrogen following the phase change and those exhibited by heavily cold-worked palladium. Partial thermodynamic parameters for hydrogen absorption are reported for palladium plastically deformed by the phase change.

Vibrational and nuclear magnetic resonance spectroscopic studies on some carbonyl complexes of gold, palladium, platinum, rhodium, and iridium

Abstract: Detailed i.r. and Raman studies are reported for [AuCl(CO)], [PtX3(CO)]–(X = Cl, Br, or I), [PdX3(CO)]–, cis-[PtX2(CO)2], cis-[RhX2(CO)2]–(X = Cl or Br), and cis-[IrCl2(CO)2]– together with assignments. Skeletal stretching wavenumbers are reported for cis-[PtX2(CO)(PMe3)](X = Cl, Br, or I), trans-[PtX(CO)(PMe3)2]+, trans-[RhX(CO)(PMe3)2](X = Cl or Br), and [RhCl3(CO)(PMe3)2]. The results of 13C n.m.r. studies on the carbony complexes are reported together with those from 1H n.m.r. and 1H-{31p} and 1H-{195Pt} INDOR spectroscopy on the phosphine-containing complexes. The 195Pt chemical shifts of [PtX3(CO)]– from direct measurements are reported. The results are discussed with the assistance of stretching force constants for some of the simpler complexes.

Sintered electrodes with electrocatalytic coating

Abstract: Sintered electrodes for electrolytic processes comprising a self-sustaining body or matrix of sintered powders of an oxycompound of at least one metal selected from the group consisting of titanium, tantalum, zirconium, vanadium, niobium, hafnium, aluminum, silicon, tin, chromium, molybdenum, tungsten, lead, manganese, beryllium, iron, cobalt, nickel, platinum, palladium, osmium, iridium, rhenium, technetium, rhodium, ruthenium, gold, silver, cadmium, copper, zinc, germanium, arsenic, antimony, bismuth, boron, scandium and metals of the lanthanide and actinide series and at least one electroconductive agent, the said electrodes being provided over at least a portion of their surface with at least one electrocatalyst for electrolysis reaction and bipolar electrodes, electrolytic cells containing said electrodes and electrolytic processes using the said electrodes as anodes and/or electrodes. Oxycompounds include oxides, multiple oxides, mixed oxides, oxyhalides and oxycarbides and mixtures thereof. PRIOR APPLICATION