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Platinum Metals Rev., 1981, 25, (3), 129

ABSTRACTS: July 1981

of current literature on the platinum metals and their alloys

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PROPERTIES


Effect of Oxygen on the Diffusion of Ni in Pt in Pt-Ni-Pt Films


c.-a. chang and w. k. chu, J. Appl. Phys., 1981, 52, (1), 512–514

Studies of the effect of O2 on the diffusion of Ni into Pt in Pt-Ni-Pt films showed that below 400°C the diffusion rates of Ni into both Pt layers were greatly reduced by O2. Above 500°C Ni rapidly mixed with the Pt layers, which led to the formation of Ni oxide on the Pt surface in the presence of O2.

High Pressure Hydrogen Absorption Study on YNi5, LaPt5 and ThNi5


t. takeshita, k. a. gschneidner and j. f. lakner, J. Less-Common Met., 1981, 78, (2), P43–P47

High pressure H2 gas (up to 1550 atm) was used to study H2 absorption in the title compounds, which do not absorb H2 at moderate pressures and room temperature. They were found to absorb a large amount of H2 at high pressures. LaPt5 and YNi5 form hydride phases, while ThNi5 dissolves H2 as a continuous series of solid solutions to high H2 concentrations. The LaPt5 and YNi5 nydride formation is thought to be controlled mainly by their lattice compressibility and not by the unit cell size.

Electronic Structure and Ordering of Hydrogen in F.C.C. Transition Metals


m. a. khan, j. c. parlebas and c. demangeat, J. Less-Common Met., 1981, 77, (1), P1–P8

The heats of formation of H atoms at octahedral and tetrahedral interstitial sites in f.c.c. Pd and Ni were estimated, and the octahedral sites were found to be more stable than tetrahedral sites. The chemical binding energies of nearest-neighbouring and next-nearest-neighbouring pairs of H atoms in α -Pd were repulsive. The binding energies between d element substitutional impurities in Pd and H atoms as the first and second neighbours were also calculated.

On the Possibility of an Increase in Titanium Corrosion Stability by Palladium Ion Implantation


n. d. tomashov, m. i. guseva, g. a. fedoseeva, a. e. gorodetski, a. p. zakharov, d. b. bogomolov, g. p. chernova, b. g. vladimirov and s. m. ivanov, Dokl. Akad. Nauk SSSR, 1981, 256, (5), 1129–1133

Studies of the effect of Pd ion implantation on corrosion stability of Ti showed an increase in corrosion stability in the Pd implanted Ti. The highest corrosion stability was observed on samples containing 5.1016−1017 Pd ions/cm2, implanted by ion energies of 20−100 keV. This increased the Ti corrosion stability 103 times.

Diffusion, Permeability and Solubility of Hydrogen in Pd-1at.%Er, Pd-1at.%Dy Alloys


a. d. spector, iu. d. kozmanov, g. e. kagan and v. v. lobanov. Fiz. Met. Metalloved, 1981, 51, (2), 354–356

Studies of the temperature dependence of the coefficients of diffusion, permeability and solubility of H2 in 1at.%Er-Pd and 1at.%Dy-Pd alloys were performed at 590−1073K. The effect of internal oxidation on H2 permeability was also studied.

Electrical Resistivity of Fe-Rich Fe-Pd Alloys between 77 and 1250 K


y. d. yao and s. arajs, Phys. Status Solidi A, 1981, 64, (1), 95–104

Electrical resistivity (ρ ) of Fe-Pd alloys containing 0.5, 1.0, 3.0, 7.9, 10.0 and 11.4 at.%Pd was studied at increasing and decreasing temperatures between 77 and 1250K. The α-γ transition exhibited hysteresis in the electrical resistivity. The temperature region for the α-γ transition can be slightly affected by the heating and cooling rates. The metastable phase in higher concentration Pd alloys is observed from an irreversible shift in the ρ data for Fe-Pd containing 7.9, 10.0 and 11.9 at.%Pd.

In Vitro Corrosion and Tarnish Analysis of the Ag-Pd Binary System


t. k. vaidy anathan and a. prasad, J. Dent. Res., 1981, 60, (3), 707–715

Ag-Pd alloys were characterised by anodic polarisation in Ringer’s solution and alternate immersion in 0.5% Na2S solution. Alloying with Pd reduces the chloride corrosion and sulphide tarnish of Ag, and the Pd rich compositions of the alloy show stable protection over a wide range of potentials. Intermediate compositions show a potential region for breakdown of protection and subsequent passivation at higher anodic overpotentials. The Ag rich compositions have little protection or passivation tendencies.

High-Temperature Effects of Shape Memory in TiNi-TiPd Alloys


v. n. khachin, n. m. matveeva, v. p. sivokha, d. b. chernov and iu. k. kovneristii. Dokl. Akad. Nauk SSSR, 1981, 257, (1), 167–169

Studies were performed on high-temperature (to 500°C) effects of shape memory in TiNi-TiPd. The results showed a practically full shape memory at high temperatures, after significant (to 4−5%) preliminary deformation of the alloy. The discovered effect increased a number of possible applications of the appearance of shape memory and explains reversible deformation during martensitic conversions.

CHEMICAL COMPOUNDS


η 3-Allyl(hydrido)phosphaneplatinum(II) Complexes


g. carturan, a. scrivanti and f. morandini, Angew. Chem., Int. Ed. Engl., 1981, 20, (2), 112–113

Novel allyl(hydrido)Pt(II) complexes were synthesised and characterised. They alter the position of equilibrium between allyl (hydrido) and olefin complexes which could be a key step in selective hydrogenations.

High Yield Preparation of Pt5(CO)6[P(C6H5)3]4; Its Use in Mixed-Metal Cluster Synthesis. Preparation and Molecular Structure of PtCo2(CO)8[P(C6H5)3]


r. bender, p. braunstein, j. fischer, l. ricard and a. mitschler, Nouv. J. Chim., 1981, 5, (2), 81–83

A new and unexpected high yield synthesis for Pt5(CO)6(PPh3)4(A) is reported which can be utilised in preparing mixed-metal clusters. Some clusters, such as Pt2Mo2Cp2(CO)6(PPh3)2 and Pt2Co2(CO)8(PPh3)2 have been synthesised previously, but the new Pt cluster PtCo2(CO)8PPh3 has only been obtained by reacting (A) with Co2(CO)8. It is the first Pt-Co triangulo cluster and has a semitriply bridging CO ligand on a heterotrimetallic face.

Carbon Dioxide Activation; Formation of trans -(Ph3P)2Rh(CO)(OCO2H) in the Reaction of CO2 with HRh(CO)(PPh3)3−CO and the Determination of Its Structure by X-Ray Crystallography


s. fazley-hossain, k. m. nicholas, c. l. teas and r. e. davis, J. Chem. Soc., Chem. Commun., 1981, (6), 268–269

The intermediate produced from the interaction of HRh(CO)(PPh3)3 with CO reacts with CO2 to yield a novel hydrogen carbonate complex, trans -(Ph3P)2Rh(CO)(OCO2H) which then undergoes a reversible loss of CO2.

ELECTROCHEMISTRY


The Effect of Anions on the Electrochemical Reduction of Thick Oxide Films on Platinum Electrode in Acidic Aqueous Solutions


s. shibata and m. p. sumino, Electrochim. Acta., 1981, 26, (4), 517–523

The cathodic galvanostatic reduction of thick oxide films on Pt was studied in HF, HClO4 and H2SO4 solutions at 25°C as a function of the current density and acid concentrations. The thick oxide film was completely reduced at a single potential step of 0.6V in HF solution and also in very dilute HClO4 and H2SO4 solutions. The effect of on the reduction of the inner-layer oxide was stronger than that of ClO4 and the effect of F was very weak.

An Investigation of Electrode Materials for the Anodic Oxidation of Sulfur Dioxide in Concentrated Sulphuric Acid


p. w. t. lu and r. l. ammon, J. Electrochem. Soc., 1980, 127, (12), 2610–2616

Catalysts for the SO2 oxidation reaction with H2O to produce H2SO4 and H2 were evaluated. Pd and Pd oxide were better catalysts than Pt. Increasing temperature remarkably improves the anodic over-potential for SO2 oxidation on a preanodised Pd electrode; however, the reaction mechanism is independent of temperature. In the anodic sweep SO2 oxidation begins at potentials where the formation of adsorbed O2-containing species is initiated. The Pd oxide covered electrode exhibits high electrocatalytic activity for SO2 oxidation.

Observation of Electrochromism in Solid-State Anodic Iridium Oxide Film Cells Using Fluoride Electrolytes


c. e. rie and p. m. bridenbaugh, Appl. Phys. Lett., 1981, 38, (1), 59–61

Thin film cells SnO2/AIROF/fluoride/Au were constructed; AIROF is anodic Ir oxide film and fluoride is PbF2 on PbSnF4. The devices exhibit reversible electrocoloration and bleaching with response times as low as 0.1 s. These cells are simple to construct and show switching speeds superior to solid state electrochromic cells previously reported.

Advances in Oxygen Evolution Catalysis in Solid Polymer Electrolyte Water Electrolysis


j. m. sedlak, r. j. lawrence and j. f. enos, Int. J. Hydrogen Energy, 1981, 6, (2), 159–165

Continuous polarisation of a stabilised RuO2 O2 anode in a solid polymer electrolyte water electrolysis cell at 1072 mA/cm2 resulted in severe anode deterioration within 24–48 hours. In contrast, a new Ru-based mixed oxide catalyst, exhibited stability in O2 evolution over a 6700 hr period. The activation energy for O2 evolution in the new catalyst is comparable to that observed on new RuO2 anodes.

An Electrode-Supported Oxidation Catalyst Based on Ruthenium (IV) pH “Encapsulation” in a Polymer Film


g. j. samuels and t. j. meyer, J. Am. Chem. Soc., 1981, 103, (2), 307–312

The oxidative catalytic behaviour of (bpy)2(py)RuO2+ and (trpy)(bpy)RuO2+ (trpy is 2,2′,2″-terpyridine) has been transferred to electrode surfaces by depositing thin polymeric films containing the (bpy)2(H2O)RuII group bound to poly-4-vinylpyridine. Upon oxidation to RuIV catalytic currents are observed. Below pH 4, potentials for the redox couples change with pH as expected, but not from pH 4–9.2 where the unbound pyridyl group becomes deprotonated. This allows the deposition to be observed, and the cyano ions were seen to be permanently bound in the films by a Fe-Ru dimer.

PHOTOCONVERSION


Hydrogen Production from Photolysis of Steam Adsorbed onto Platinized SrTiO3


r. g. carr and g. a. somorjai, Nature, 1981, 290, (5807), 576–577

Photodissociation of ultrapure, high pressure (1–8 atm) H2O at high temperatures (100−160°C) occurred under vacuum conditions, with Ar gas as carrier, on a single crystal wafer of SrTiO3 with a thin Pt coating, when illuminated by a Hg discharge lamp. The photoreaction was highest when the coating was transparent, and the photon energy was higher than the bandgap energy (3.1 eV). After ∼ 10 hours the H2 production rate drops because of equilibration of production and recombination rates and surface poisoning. This work did not involve an electrolyte and the surface is accessible to UHV analytical surface techniques for examining the reaction mechanisms.

Visible Light Induced Water Cleavage in CdS Dispersions Loaded with Pt and RuO2, Hole Scavenging by RuO2


k. kalyanasundaram, e. borgarello and m. grätzel, Helv. Chim. Acta, 1981, 64, (1), 362–366

Visible light illumination of aqueous CdS dispersions loaded with Pt and RuO2 produces stoichiometric amounts of H2 and O2. No photo catalyst degradation was noted after 60 hr irradiation. The RuO2 deposit on the particle surface greatly accelerates the transfer of holes from the semiconductor valence band to the aqueous solution, thus inhibiting photo-corrosion.

Photocatalytic Reaction of Water with Carbon over Platinized Titania


s. sato and j. m. white, J. Phys. Chem., 1981, 85, (4), 336–341

The reaction of gaseous water with active C over illuminated platinised TiO2 was studied at room temperature and 60°C. The products were H2, CO2 and a little O2. Accumulation of H2 decreases contact between catalyst and C and reaction rate declines. At room temperature the quantum efficiency is ∼2% at the beginning of the reaction. With liquid H2O, the oxidation of C is inhibited and O2 as well as H2 evolves.

Oxidative Substitution Reaction of the Osmochrome Os(OEP)[P(OMe)3]2 in Chlorinated Solvents


n. serpone, m. j. jamieson and t. l. netzel, J. Photochem., 1981, 15, (4), 295–301

Photolysis of Os(OEP)[P(OMe)3]2, where OEP is octaethylporphine, in the chlorinated solvents CH2Cl2, CHCl3 and CCl4 at 365 and 405 nm and at 22°C, produced an Os(IV) porphyrin identified as Os(OEP)Cl2. The rate of the product formation increased in the order of solvents CH2Cl2< CHCl3<CCl4 in the ratio 1 : 8 : 120. A possible mechanism involving radicals is suggested.

Electrogenerated Chemiluminescence. 37. Aqueous Eel Systems Based on Ru and Oxalate or Organic Acids


i. rubinstein and a. j. bard, J. Am. Chem. Soc., 1981, 103, (3), 512–516

A new aqueous chemiluminescent and ecl system based on and a suitable organic acid or salt is described. The bright orange chemiluminescence, which could also be generated by reaction of chemically produced Ru(III) species with oxalate, corresponded to emission by ; ecl efficiency (photons emitted/ generated) was ∼2% in deaerated solution. Ecl by reaction of the 1+ and 3+ Ru species was also obtained in partially aqueous solutions containing at least 20% acetonitrile. Chemiluminescence was observed with other organic acids.

Photoredox Reactions in Functional Micellar Assemblies. Use of Amphiphilic Redox Relays to Achieve Light Energy Conversion and Charge Separation


p.-a. brugger, p. p. infelta, a. m. braun and m. grätzel, J. Am. Chem. Soc., 1981, 103, (2), 320–326

The photoreduction of a homologous series of amphiphilic viologens (CnMV2+) using and Zn tetrakis(N-methylpyridyl)porphyrin(ZnTMPyP4+) as sensitiser was studied in H2O and aqueous solution containing cationic micelles, to establish pathways preventing back reactions. On reduction the relay acquires hydrophobic properties leading to rapid solubilisation in the micelles, and the thermal back reaction is impaired at least 500 times. The intermediates had high stability and the lifetimes were long enough to allow the intervention of ultrafine Pt particles as the efficient catalyst to couple three relays C12MV2+−C16MV2+ with light induced H2 production from water.

ELECTRODEPOSITION AND SURFACE COATING


Studies of Processes of Electrodeposition of Palladium-Iridium Alloy from Ammonium-Trilog and Sulphamide Electrolytes


a. a. tikhonov, p. m. viacheslavov and g. k. burkat, Zh. Prikl. Khim. (Leningrad), 1981, 54, (2), 364–369

The effect of electrolyte composition and electrolysis parameters on the composition and quality of deposited Pd-Ir layers was studied. The Pd-Ir alloy layer from the ammonium-trilog electrolyte exhibited high wear resistance and low internal stress. Technological processes for depositing Pd-Ir alloys from ammonium-trilog electrolytes can be used in the production of coatings for the collector of d.c. electric motors and in contacts. The use of Pd-Ir alloys instead of Pd layers increases the reliability of electric contacts.

LABORATORY APPARATUS AND TECHNIQUE


A Titanium Dioxide Hydrogen Detector


l. a. harris, J. Electrochem. Soc., 1980, 127, (12), 2657–2662

Sputtered films of TiO2 several thousand angstroms thick and sandwiched between a layer of Ti and a layer of Pt are highly selective H2 detectors. The Pt film is made negative with respect to Ti, providing a greater dynamic range and faster recovery when H2 is removed. Above 0.5% H2 in air the response of the detector is rapid and limited by lead resistance. At lower concentrations (a few hundred ppm in air) the response is proportional to concentration, but relatively slow at room temperature. Increasing temperature quickens the response. The detectors can be used as alarm devices at room temperature, with a.c. or d.c. circuitry that requires negligible power in the absence of H2.

Brazing of Sensors for High-Temperature Steam Instrumentation Systems


a. j. moorhead, c. s. morgan, j. j. woodhouse and r. w. reed, Weld. J. (Miami), 1981, 60, (4), 17–28

The structure of a probe for high temperature detection in water-cooled nuclear reactors is discussed. The probe measures impedance between two electrodes in the space between three fuel rod simulators giving the steam : water ratio. Base materials for brazing including platinised Al2O3-Pt and platinised Al2O3-Ir which with 72Ti-28Ni and 49 Ti-49Cu-2Be filler metal composition had excellent wetting with no visible cracks. Steam corrosion testing, including high temperature steam exposure of 304L stainless steam joined to Pt on Kovar sheet was examined. A ceramic-to-metal seal of platinised Al2O3 cermet insulator brazed to a Pt transition material, with a filler of 49Ti-49Cu-2Be was used in the probe.

HETEROGENEOUS CATALYSIS


The Effects of SO2 on the Oxidation of Hydrocarbons and Carbon Monoxide over Pt/γ -Al2O3 Catalysts


h. c. yao, h. k. stepien and h. s. gandhi, J. Catal., 1981, 67, (1), 231–236

Propane and propylene were used to test the effects of SO2 on the oxidation of saturated and unsaturated hydrocarbons over Pt/γ -Al2O3 catalysts in a flow reactor. SO2 in the feed gas enhanced propane oxidation but suppressed propylene and CO oxidations. This is due to the formation of surface sulphates on γ -Al2O3 after the SO2 adsorption and oxidation and their effects on the chemisorptive properties of the Pt/γ -Al2O3. These sulphates may enhance propane oxidation by increasing its dissociative adsorption on Pt and suppressing CO and propylene oxidations by decreasing the associative CO and propylene adsorptions on Pt.

Study of the Factors Affecting the Stability of Supported Metals against Sulphur. 1. Effect of the Nature of the Support on the Stability against Sulphur of Nickel-, Platinum- and Palladium-Containing Catalysts


g. v. echevskii, k. g. ione, l. a. vostrikova and l. s. egorova, Kinet. Katal., 1981, 22, (1), 208–212

Studies of the stability of Pt, Pd and Ni supported catalysts against S were performed during 1-hexene hydrogenation. Stability of the catalysts did not depend on the Na content, the degree of dealuminisation of the Y type zeolites, mordenites, or on the nature of the support. The increase in activity of S containing metal catalysts with the increase of decationisation of the supports is connected with the stabilisation of more dispersed compounds.

Design Factors of Dual Bed Catalysts


j. c. summers and d. r. monroe, Ind. Eng. Chem., Prod. Res. Dev., 1981, 20, (1), 23–31

The effect of various design parameters on the performance of dual bed systems was studied. For front bed catalysts, in which Rh is very active, neither Pt nor Pd adds to the warmed up CO or HC conversions. Pt and Pd affect the NO conversion activity of Rh, deteriorating rich and enhancing lean conversions. Pt and Pd assist Rh for lightoff. The three-way durability performance of Pt and Pd is poorer than that of Rh. Increasing the noble metal loading of the rear bed increases the warmed up durability of the dual bed catalyst. Poisons are unequally distributed with P and Pb collecting heaviest on the front bed and S heaviest on the rear.

Hydrocarbon Conversion Reactions over Platinum-Ruthenium Alloys Supported Catalysts


g. blanchard, h. charcosset, m. guenin and l. tournayan, Nouv. J. Chim., 1981, 51, (2), 85–89

Poorly dispersed Pt-Ru/SiO2 and well dispersed Pt-Ru/Al2O3 were studied during hydrogenation of benzene, dehydrogenation of cyclohexane and conversion of n-heptane. For benzene hydrogenation the turnover number was a maximum for about 75at.% Ru/(Pt + Ru). In the two other reactions turnover number decreased as % Ru/(Pt + Ru) increased. The results are discussed in terms of the nearly identical mean and surface compositions of the Pt-Ru alloy particles, the dilute effects on Pt by Ru and the role of carbonaceous deposits.

A Contribution of Catalysts for the Aromatising of Ethylene


o. v. bragin, t. v. vasina, a. v. preobrazenskij, p. birke, s. engels and m. wilde, Z. Anorg. Allg. Chem., 1981, 472, (1), 173–178

A series of monometallic, bimetallic and trimetallic platinum group metal catalysts supported on Al2O3 were tested for the aromatisation of ethylene. The results were correlated with the composition and the metal dispersion of the catalysts.

Palladium-Catalyzed Oxidation of Terminal Olefins to Methyl Ketones by Hydrogen Peroxide


m. roussel and h. mimoun, J. Org. Chem., 1980, 45, (26), 5387–5390

A very efficient catalytic procedure for the oxidation of terminal olefins to methyl ketones by H2O2 using a Pd catalyst and operating in the absence of halogens and co-metals is discussed. A high selectivity for 2-octanone formation was observed, and a 90−95% conversion of 1-octene was obtained after 3 hours of reaction time. 3- and 4-octanone were the major by-products.

Kinetics of Hydrogenation of Cyclic Butadiene Oligomers on Palladium Catalysts. I. Cyclooctadiene Isomers. II. 1,5,9-Cyclododecatrine Stereoisomers


j. hanika, i. svoboda and v. růzicka, Collect. Czech. Chem. Commun., 1981, 46, (4), 1031–1038, 1039–1047

The kinetics of hydrogenation of 1,3- and 1,5-cyclooctadiene, cyclooctene and of 1,5,9-cyclododecatriene stereoisomers and cyclododecene were studied on Pd/Al2O3, Pd/C and Pd/CaCO3 catalysts in n-heptane solutions at 300K and H2 at atmospheric pressure. The kinetic constants were obtained by relating the experimental data to a kinetic model in which the partial reactions are assumed to be first order.

Selective Hydrogenation of Benzene over Platinum or Palladium Supported on Organic Polymer Catalysts. II. Characterisation of Palladium Deposited on Polyamide-66 by Hydrogen-Oxygen Titration and Electron Microscopy


c. michel, c. hoang-van and s. j. teichner, J. Chim. Phys. Phys.-Chim. Biol., 1981, 78, (3), 241–245

The metal surface area of Pd/nylon-66 catalysts was measured by hydrogen-oxygen titration. The presence of Pd crystallites was observed inside the nylon carrier. Most of them had a mean diameter of ∼30Å, thus confirming the Pd penetration during catalyst preparation into the bulk of the nylon carrier. Catalytic properties of Pd/nylon catalysts support the hypothesis of a modification of metallic sites resulting from an interaction between Pd and nylon.

Chemical Oscillations of Methanol-Oxidation on a Pd-Supported Catalyst


n. i. jaeger, p. j. plath and e. van raaij, Z. Naturforsch., A, 1981, 36, (4), 395–402

A periodic reaction was observed during the complete oxidation of MeOH to CO2 and H2O over a Pd-supported catalyst. The temperature oscillations of the catalyst and the corresponding product distribution were measured and correlated with a chemical reaction scheme. This scheme is based on the monotonic behaviour of the pressure-concentration relationship in the Pd-H system.

Study of the Effect of PdCu Zeolites Acidity on Their Catalytic Properties in Ethylene Oxidation to Acetaldehyde


kh. m. minachev, n. ia. usachev, ia. i. isakov, a. p. rodin and v. p. kalinin, Izv. Akad. Nauk SSSR, Ser. Khim., 1981, (4), 724–730

Catalytic properties of ion exchange PdCu catalyst supported on zeolites type A, X, Y, and mordenite during C2H4 oxidation depended on their acidity. The increase in concentration of the acid OH group in PdCuNaY zeolites decreased the activity, selectivity and stability of the catalyst. Spectroscopic studies showed that NH3, which was added to zeolites in the complex or by adsorption, reacted with acid H+ centres in aluminosilicate and also with cations of transition metals.

The Effects of Different Supports on the Formation and Reactivity of Surface Isocyanates on Pd, Ir, Ru and Rh


f. solymosi, l. vögyesi and j. raskó, Magy. Kem. Foly., 1981, 87, (1), 23–27

The effect of Al2O3, MgO, TiO2 and SiO2 supports for Pd, Rh, Ir and Ru catalysts was studied on the formation and stability of isocyanate species in the NO + CO reaction. Isocyanate formation occurred easily on TiO2 supported metal, but very slowly on SiO2. The location of the isocyanate bond hardly depended on the metal, but was strongly influenced by the support. The isocyanate was relatively unstable on M/TiO2 but was extremely stable on M/SiO2. The results were explained by assuming that isocyanate forms on the metal, but migrates rapidly onto the support, which thus determines its behaviour.

Catalytic Synthesis of 3-Substituted Indoles Using CO as Building Block and Supported Rhodium as Catalyst


e. ucciani and a. bonfand, J. Chem. Soc., Chem. Commun., 1981, (3), 82–83

Under hydroformylation conditions, using Rh/C as catalyst, 2-nitrostyrene is directly converted into skatole in ∼70% yield, by a reaction involving formation of 2-(o-nitrophenyl)propionaldehyde by homogeneous catalysis, reduction of the nitro-group by heterogeneous catalysis, then ring closure and thermal dehydration. Thus under severe hydroformylation conditions supported Rh can act as a reservoir of Rh carbonyl complexes and a mass contact able to activate H2, and a catalytic route to 3-substituted indoles from 2-nitrostyrenes and CO is available.

Zeolite Support Effects on CO-Ru Interactions


d. g. blackmond and j. g. goodwin, J. Chem. Soc., Chem. Commun., 1981, (3), 125–126

An i.r. study of Co adsorption on a series of zeolite-supported Ru catalysts relates strong metal-support interactions to higher zeolite activity and lower Fischer-Tropsch/methanation activity.

HOMOGENEOUS CATALYSIS


Homogeneous Reduction of Nitrobenzene p-Chloronitrobenzene in Presence of Dichlorobis(phenylcyano)palladium(II) as Catalyst


t. k. banerjee and c. r. saha, Indian J. Chem., 1980, 19A, (10), 964–966

The complex Pd(C6H5CH)2Cl2 was prepared and used as a homogeneous catalyst for the reduction of C6H5NO2 and p-ClC6H4NO2 in a basic ethanolic medium. Reduction of C6H5NO2 produced only aniline (94%) under normal pressure and aniline and azoxybenzene (45% and 20%, respectively) under high pressure. The yield of p-ClC6H4NH2 from p-ClC6H4NO2 is highest (60%) at normal pressure and decreases with increasing pressure.

A Chemist’s Tool Kit


r.e. merrill, Chemtech, 1981, 11, (2), 118–127

A review of biologically active compounds, most being optically active, is presented. Ways of synthesising them, especially by asymmetric syntheses are examined. The first asymmetric catalysis, including hydrogenation with Wilkinson’s catalyst, Rh(PPh3)3Cl, is discussed, and asymmetric syntheses with chiral phosphine complexes are explained. Also discussed are asymmetric hydrosilylations, catalysed by Pt, Pd, Rh or Ni complexes and asymmetric alkylations.

Kinetics and Selectivity of Homogeneous Hydroformylation of 1-Hexene with RhHCO(PØ3)3


w. strohmeier and m. michel, Z. Phys. Chem. (Frankfurt am Main), 1981, 124, (1), 23–31

Studies of the bulk hydroformylation of 1-hexene with RhHCO(PØ3)3 catalyst showed that the selectivity (n/isoaldehyde) increases with PØ3 concentration as well as with decreasing total pressure and goes through a maximum at 90°C. The selectivity was practically independent of catalyst concentration when the rate was not controlled by gas diffusion. At constant pressure and catalyst concentration, the conversion of 1-hexene obeys a pseudo first order rate law.

Catalytic Double Bond Isomerization by Polystyrene-Anchored RuCl2(PPh3)3


a. zoran, y. sasson and j. blum, J. Org. Chem., 1981, 46, (2), 255–260

Dichlorotris(triphenylphosphine)Ru has been anchored to diphenylphosphinated styrene-divinylbenzene copolymer. The resulting catalyst has been successfully used for isomerising allylbenzenes and allyl alcohols in numerous turnovers. The catalyst stability was examined in several media and its performance compared with those of homogeneous RuCl2(PPh3)3 and with those of polymer-bound and free RhCl(PPh3)3 and IrCl(CO)(PPh3)2.

The Kinetics and Mechanism of Homogeneous Hydrogen Transfer upon Alcohols to Benzylideneacetone Catalyzed by Dichloritris(Triphenylphosphine)Ruthenium (II)


g. speier and l. markó, J. Organomet. Chem., 1981, 210, (2), 253–262

Ru(II)Cl2(PPh3)3Ru(II) catalyses the transfer from alcohols to olefins. Kinetic studies were carried out at 170−190°C using the Ru(II) complex as homogeneous catalyst, benzyl alcohol, diphenylcarbinol, methylphenylcarbinol and benzoin as the H donors, benzylideneacetone as H acceptor and dibenzyl ether as a solvent. In the reaction mixture RuCl2(PPh3)3 is converted by the alcohols into RuH2(CO)(PPh3)3 which then hydrogenates benzylideneacetone. The rate determining step is the transfer of H from the alcohol to a Ru species.

FUEL CELLS


Electrocatalytic Problems Associated with the Development of Direct Methanol-Air Fuel Cells


b. d. mcnicol, J. Electroanal. Chem. Interfacial Electrochem., 1981, 118, 71–87

The potential advantages of the direct methanol-air fuel cell over conventional power sources are reviewed and in particular the area of noble metal catalytic electrodes is discussed in some detail. The role of the second component in bimetallic catalysts and the activity of such noble metal catalysts is also discussed. (41 Refs.)

CHEMICAL TECHNOLOGY


Production of Pd-Cu-Si Amorphous Wires by Melt Spinning Method Using Rotating Water


t. masumoto, l. ohnaka, a. inoue and m. hagiwara, Scr. Metall., 1981, 15, (3), 293–296

Continuous Pd-Cu-Si amorphous alloy wire has been produced by a melt spinning method directly from the liquid state. The wire was supercooled below the glass transition temperature of the alloy without breakup of the stable jet stream. The wires had good shape and uniformity.

ELECTRICAL AND ELECTRONIC ENGINEERING


Reaction at a Platinum-Gallium Arsenide Interface


d. l. begley, r. w. alexander, r. j. bell and c. a. goben, Surf. Sci., 1981, 104, (2/3), 341–353

The reaction at a Pt/n-GaAs interface after annealing at 400°C was investigated by various techniques. An increase in optical reflectivity was observed early in the annealing sequence, and a complex layered structure formed at the interface, but Ga was seen to diffuse rapidly into the Pt film at apparent imperfections in the film. These areas are believed to be primary sites for premature IMPATT device failure.

An AES/XPS Study of the Chemistry of Palladium on Hydrogenated Amorphous Silicon Schottky Barrier Solar Cells


j. h. thomas and d. e. carlson, J. Electrochem. Soc., 1981, 128, (2), 415–420

Thin layers of Pd (∼100 Å thick) on hydrogenated amorphous Si have been used as diodes and photovoltaic devices (solar cells). AES and XPS with ion-milling were used to characterise the interface region, where a thin oxide layer is observed along with possible Pd silicide. Pd and Pd silicides extend well into the Si substrate. Pd silicide is due in part to ion-mixing. The degradation is due to oxide formation at the Pd/a-Si:H interface.

Thin Palladium Silicide Contacts to Silicon


s. kritzinger and k. k. tu, J. Appl. Phys., 1981, 52, (1), 305–310

A new approach to the development of very thin Pd2Si-to-Si contacts for possible future use in ultrasmall devices is described. It is based on the principle of diluting the silicide-forming Pd metal with Si, by codeposition of these two elements onto a single-crystal Si substrate. During annealing of the layered structure, Pd is extracted from the amorphous alloy to form the metal-rich and very stable compound Pd2Si at the surface. The decomposing Pd80Si20 is also converted to Pd2Si. In this way, a silicide is formed for which only ∼50% of the required Si need be supplied by the Si-substrate, resulting in a very shallow silicide contact.

A Comparison of Clad Inlay Gold, Palladium, and Palladium-Silver Contact Alloys


r. j. russell and p. o. capp, Insul./Circuits, 1981, 27, (3), 34–38

A comparison of contact resistance between Pd and 60% Pd-40%Ag and traditional Au alloys was performed. Pd and 60%Pd-40%Ag clad inlays had low, stable contact resistance under dry circuit conditions and with 100g load after artificial ageing. Au clad inlays had considerable contact resistance increases after artificial ageing. Their resistances were greater than those of Pd and 60%Pd-40%Ag at the same thickness. Pd and 60%Pd-40%Ag contact alloys were equal in performance to other precious metal alloys when subjected to a hostile gas environment.

MEDICAL USES


Pd-Co Dental Casting Ferromagnetic Alloys


y. kinouchi, j. ushita, h. tsutsui, y. yoshida, h. sasaki and t. miyazaki, J. Dent. Res., 1981, 60, (1), 50–58

Three dental alloys, 43wt.%Pd-57wt.%Co, 41wt.%Pd-54wt.%Co-5wt.%Cr and 43wt.%Pd-27wt.%Co-30wt.%Ni have been developed, and their magnetic and physical properties and corrosion resistances have been measured. The alloys were found to have magnetic properties suitable for generating an effective magnetic attraction in combination with the Sm-Co magnet. They have typical dental casting alloy properties, Pd-Co-Ni was the most easily melted and had the highest corrosion resistance.

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