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Platinum Metals Rev., 1988, 32, (3), 148

ABSTRACTS: July 1988

of current literature on the platinum metals and their alloys

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PROPERTIES

Metal Substrates Wetting by Indium. II. In-Pt System

j. jandovÁ and j. duŠan, KovovÉ Mater., 1988, 26, (1), 71–75

Studies of Pt wettability by liquid In at 400°C showed that after 30 min In fully dissolved in Pt forming In2Pt intermetallic compound. The wetting angle during the starting period (the first 30 min) was determined as 86±3 rad.

Thermally and Ion-Induced Reaction between Si and Binary Metallic Alloys

l. s. hung, q. z. hong and j. w. mayer, J. Appl. Phys., 1988, 63, (5), 1749–1753

Thermally and ion-induced reactions between Si and binary alloys PtV (solid solution), PtTi (intermetallic compound) and NiTa (amorphous phase), of approximately equiatomic compositions, were investigated. Thermal annealing was performed at 500−700°C. Separated binary silicides were formed in the Pt-V and Ni-Ta systems, while ternary compound PtTiSi was observed in the Pt-Ti system. Ion irradiation was performed at 200−400°C. Uniform mixed amorphous layers were produced in all three systems upon irradiation at relatively low temperatures. Mixtures PtVSi2 and NiTaSi2 were transformed to separated binary silicides by post-annealing, but the PtTiSi2 underwent an amorphous-metastable phase transformation. Thus the dominance of Si motion with the non-equilibrium nature of ion mixing can be used to produce metastable phases in the ternary system.

The Influence of Oxygen on the Selectivity of Alcohol Conversion on the Pd(111 Surface

j. l. davis and m. a. barteau, Surf. Sci., 1988, 197, (1/2), 123–152

The reactions of methanol, ethanol, 1-propanol and 2-propanol were studied on a Pd(111 surface containing one-quarter monolayer of adsorbed O atoms. Methanol was oxidised on the O-dosed Pd(111 surface to formaldehyde and surface formate species. The adsorption of ethanol on the O-dosed Pd(111 surface resulted in the desorption of acetaldehyde at 220K and the formation of surface acetate species. Adsorbed acetate species reacted, via either decomposition at 410K or hydrogenation, to acetic acid at 280K. The relative importance of the two acetate reaction channels was found to depend on the availability of surface H. Similarly, the adsorption of 1-propanol on O/Pd(111 produced both propanal and adsorbed propanoate species. The roles of O adatoms in these reactions were discussed.

The Effect of Nitrogen Implantation on the Tribological Properties of Gold-Based Alloys and Electroplated Palladium

p. w. leech, IEEE Trans. Components, Hybrids, Manuf. Technol., 1988, 11, (1), 16–21

The effect of N2+ ion implantation on the friction and wear behaviour of 30%Pd-29.5%Ag-1.5%Sn-Au,26%Ag-3%Ni-Au and 8%Ag-Au alloys and electroplated Pd was studied. Rider-on-flat experiments showed that N2+ implantation in either the rider in 8%Ag-Au or the flat in the remaining alloys produced a significant reduction in the coefficient of friction and in the extent of surface wear sustained during sliding. Layers of electroplated Pd showed only minor changes in friction and in sliding damage to the flat following N2+ implantation of both surfaces.

Change of Structure and Properties during Annealing of Cold Worked Pd-Fe Alloy

e. i. teitel’ and g. m. gushchin, Fiz.Met.Metalloved., 1988, 65, (2), 332–340

Structural changes and their effect on electroresistance, magnetic and mechanical properties were studied during annealing of cold worked Pd-Fe alloys at 500°C. The results showed formation of dispersed ordered domains, recovery and recrystallisation, forming super-fine dispersed grains with a high level of tensile order. Recrystallised grains showed an increased density, dislocation and twin deformation due to interaction with the ordered matrix which appeared in the elastic-tension state. The mechanism of the kinetics of changes in electroresistance, coercive force and mechanical properties connected with the structural state of the alloys were discussed.

Hydrogen Solubility and the Equilibrium Pressure-Composition Isotherm for Pd-Eu Alloys

s. t. al-ashab and i. r. harris, Int. J. Hydrogen Energy, 1988, 13, (3), 191–194

The H2 solubility and the equilibrium pressure of Pd-Eu alloys were studied. The microbalance-H system was used to determine the pressure-composition isotherm curves of the Pd-Eu-H alloy system containing 1.3 and 5%Eu in a range 0 to 7 atmospheric pressure and at room temperature up to 400°C. The hysteresis phenomena became smaller as the Eu content increased. The effect of Eu content on the partial molar enthalpy and entropy of absorption of mole of H(ΔHH,ΔSH) and the miscibility gap were discussed. The strain energy of Pd-Eu-H was less than that of Pd-Ce-H and more than of Pd-Pb-H.

Growth Kinetics of Palladium Silicides Formed by Rapid Thermal Annealing

c. s. wei, j. van der spiegel and j. j. santiago, J. Electrochem. Soc., 1988, 135, (2), 446–451

Pd2Si is formed through direct reaction of an electron-evaporated Pd thin film and single-crystal <100> Si substrate by rapid thermal annealing. The sample temperatures were measured by a variety of means, and the maximum sample temperatures, were 310−460°C. Pd2Si is the first and only phase in this range and forms at 320°C. The activation energy for the diffusion-controlled silicide growth is 1.4±0.2eV. Thus the growth mechanism of Pd2Si is the same in both rapid thermal annealing and conventional furnace annealing.

Reordering of Polycrystalline Pd2Si on Epitaxial Pd2Si

c. m. comrie, j. c. liu, l. s. hung and j. w. mayer, J.Appl.Phys., 1988, 63, (7), 2402–2405

Polycrystalline Pd2Si was found to reorder on top of epitaxial Pd2Si during silicide growth. The interface between polycrystalline Pd2Si and epitaxial Pd2Si was thus not immobile with respect to the silicide lattice during silicide formation. It was not, therefore, possible to use this interface as a structural marker in order to monitor diffusion in epitaxial Pd2Si. The use of Ti as an inert marker showed that Si was the dominant diffusing species in epitaxial Pd2Si during silicide formation.

Ultrasonic Study of Mechanically Alloyed Amorphous PdSiCu

a. hikata, m. j. mckenna and c. elbaum, J. Appl.Phys., 1988, 63, (6), 1910–1913

An amorphous alloy Pd0.775Si0.165Cu0.60 has been produced by a mechanical alloying process which involves repeatedly deforming, fragmenting and cold welding appropriate amounts of the constituent powders by milling with steel balls in an argon atmosphere, at around room temperature. X-ray diffraction indicates that amorphisation proceeds rapidly with time; no further changes are apparent after milling for 8 hours. This alloy has ultrasonic characteristics typical of an amorphous alloy of similar composition produced by rapid solidification, indicating that a very fast diffusion mechanism has taken place.

Heavy-Fermion Mixed-Valent Behaviour in YbPdSb and YbPdBi

s. k. dhar, n. nambudripad and r. vijayaraghavan, J.Phys.F, 1988, 3, (18, L41–L44

Measurements were made at low temperatures of the heat capacity at 2–20K and magnetic susceptibility at 4.2−300K in the cubic compounds YbPdSb and YbPdBi. From the linear portion of plots of C/T against T2, a γ value of 470 and 240mJ/molK2 was obtained for YbPdBi and YbPdSb, respectively. The magnetic susceptibility results reflected the fluctuating nature of the valence of Yb ions in both compounds.

A Comparison of the Desorption of CO from Pt and Rh Particles on α -Al2O3{0001}

e. i. altman and r. j. gorte, Surf. Sci., 1988, 195, (3), 392–402

The adsorption of CO on Rh particles supported on α -Al2O3{0001} was studied using temperature programmed desorption. The Rh was evaporated onto the non-porous α -Al2O3 substrate in ultra-high vacuum and metal coverage was measured using a quartz-crystal, film thickness monitor. Spectroscopic studies showed that Rh grew as three-dimensional particles on the alumina substrate at 300K. For all Rh particle sizes studied, CO desorbed in peaks at 500 and 425K, which were the same temperatures observed on Rh foils and single crystals.

Kinetics of CO Oxidation by O2 or NO on Rh(111 and Rh(100 Single Crystals

c. h. f. peden, d. w. goodman, d. s. blair, p. j. berlowitz, g. b. fisher and s. h. oh, J. Phys. Chem., 1988, 92, (6), 1563–1567

The oxidation of CO by O2 or NO over Rh(111 and Rh(100 single crystals was studied in a high-pressure reaction high-vacuum surface analysis apparatus. Steady-state catalytic activity as a function of temperature and partial pressures of CO, O2 and NO was measured. The CO-O2 reaction was insensitive to the structure of the surface as shown by the identical rates, activation energies, and partial pressure dependencies measured on the two single-crystal surfaces. Deactivation occurred at a slightly lower O2 partial pressure on Rh(100, which was possibly due to the relative ease of formation of the bulk oxide via diffusion of oxygen through this surface. In contrast to the CO-O2 reaction, the rate of CO oxidation by NO is dramatically different on the two single-crystal surfaces studied.

Paramagnetic Rhodium Species in Zeolites. Part I. RhNa-X and RhNa-Y

a. sayari, j. r. morton and k. f. preston, J. Chem. Soc., Faraday Trans. I, 1988, 84, (2), 413–431

Five different paramagnetic RhIIspecies were stabilised following activation by flowing O2 at 200−475°C in ion-exchanged RhNa-Y samples prepared either from [Rh(NH3)5Cl]Cl2 (sample I) or from RhCl3.3H2O (sample II). The condition of formation of these species, their stability and their possible locations were studied.

X-Ray Investigations in the Systems Ruthenium-Silicon and Ruthenium-Silicon-Nitrogen

f. weitzer, p. rogl and j. c. schuster, Z. Metallkd., 1988, 79, (3), 154–156

X-ray studies of the ternary system Ru-Si-N and its binary system Ru-Si showed that no ternary phase was found to exist at temperatures of 1000−1250°C in the absence of external nitrogen pressure. Isothermal sections for the ternary system were given. A new phase diagram for the binary Ru-Si is proposed.

Thermochemistry of the Intermetallic Compounds RuTi, RuZr, and RuHf

l. topor and o. j. kleppa, Metall. Trans. A, 1988, 19A, (4), 1061–1066

The standard enthalpies of formation of RuTi, RuZr and RuHf have been determined by high temperature mixing calorimetry at 1400K, as −153.9±7.4,−137.3±6.8 and −183.5±10.4 kJ/mol, respectively. These are the first experimentally measured enthalpies of formation for these intermetallics that have been reported; and they are compared with calculated values and values of equiatomic alloys of Pd and Rh with Ti, Zr and Hf.

CHEMICAL COMPOUNDS

Mixed Platinum-Gold Clusters. Synthesis, Structure and Properties of PtAu8(PPh3)8(NO3)2

j. j. bour, r. p. f. kanters, p. p. j. schlebos and j. j. steggerda, Recl. Trav. Chim. Pays-Bas, 1988, 107, (3), 211–215

The mixed Pt-Au cluster PtAu8(PPh3)8(NO3)2 was formed by the reaction of H2 with Au(PPh3)NO3 and either Pt(PPh3)3 or Pt(COD)(NO3)2. The metal frame is a centred crown with a phosphine bonded to each peripheral metal atom. Spectroscopic studies showed that Pt is in the centre and that the 8 Au atoms are on the crown. An electrochemical study showed that the cluster could be reduced in two reversible one-electron steps at −1.14 and −1.29V.

The Reaction of a Zwitterionic Diphosphorus Compound with the Platinum(O) Complex, (C2H4)Pt(PPh3)2

p. look, r. schmutzler, r. goodfellow, m. murray and d. schomburg, Polyhedron, 1988, 7, (7), 505–512

The oxidation-reduction reaction between a zwitterionic diphosphorus compound, involving the grouping Cl-P(−)-P(+)-NEt2 with the Pt(o) complex, (C2H4)Pt(PPh3)2, produced a novel Pt(II) complex with a Pt-P four-membered ring. The identity and structure of this Pt complex was determined by NMR and by single-crystal X-ray study.

Na2PdH2, A Hydride with a Novel Linear [PdH2] Complex

d. norÉus, k. w. tÖrnroos, a. bÖrje, t. szabÓ, w. bronger, h. spittank, g. auffermann and p. mÜller, J. Less-Common Met., 1988, 139, (2), 233–239

The ternary hydride Na2PdH2 was prepared by the reaction of Na hydride with Pd in a hydrogen atmospere at 370°C. The structure was derived from X-ray studies on powdered samples and on a single crystal as well as from neutron diffraction experiments on the deuterated compound. Na2PdH2 crystallised in the tetragonal space group I4/mmm and was isotypic with Na2HgO2. The atomic arrangement was a novel linear [PdH2] complex.

Novel Reaction of an Iridium Carbonyl Complex with Xenon Difluoride: the First Metal Fluoroacyl Complex

a. j. blake, r. w. cockman, e. a. v. ebsworth and j. h. holloway, J. Chem. Soc., Chem. Commun., 1988, (8), 529–530

The cation [Ir(CO)3(PEt3)2]+ reacted smoothly with XeF2 at 273K in CH2Cl2 to give the novel species [Ir(CO)2F(COF)(PEt3)2]+ (1) in high yields. The product (1) is the first fluoroacyl complex described and is stable at room temperature in the absence of air and moisture. It was isolated as BF4 and PF6 salts and was characterised spectroscopically, crystallographically and by partial elemental analysis. The product (1) has considerable potential as a synthetic intermediate.

Surface-Mediated Organometallic Synthesis: Formation of [Os5C(CO)14]2− from [Os3(CO)12] on MgO

a. s. fung, p. a. tooley, m. j. kelley and b. c. gates, J. Chem. Soc., Chem. Commun., 1988, (5), 371–372

A simple one-step high yield synthesis of [Os5C(CO)14]2− from [Os3(CO)12] conversion on the surface of partially dehydroxylated MgO under 1 bar of flowing CO at 550 K is reported. This synthesis is far simpler and gives much higher yields of about 65% than the conventional synthesis. Previously the production was multistep and required tedious separations. Surface mediated synthesis may find wide application in organometallic chemistry.

Energy Transfer and Highly Resolved Emission of [Ru1−xOsx(bpy)3](PF6)2

h. yersin, g. hensler and e. gallhuber, J. Lumin., 1988, (40 & 41), 676–677

The emission properties of the title compound were studied at T = 2K and high magnetic fields. The radiationless energy transfer from the [Ru]-host to the [Os]-guest was governed by a fast process and a slow one, which showed a relatively ineffective transfer in the host material.

ELECTROCHEMISTRY

Effect of Tin Adatoms on the Electro-oxidation of Ethylene Glycol on a Platinum Electrode

o. a. petrii and n. v. smirnova, Electrokhimiya, 1988, 24, (4), 522–526

Electro-oxidation of ethylene glycol was studied on a platinised Pt electrode modified by Sn adatoms, in acid and alkaline media under stationary conditions. The results showed that electro-oxidation of ethylene glycol greatly increased in the presence of Sn adatoms which was due to the oxide-absorbing character of Sn adatoms. It is shown, that adatoms affect changes in the character of oxidation of chemisorbed ethylene glycol products and cause the disappearance of high charge effect.

Metal Electrodes Bonded on Solid Polymer Electrolyte Membranes (SPE). V. Methanol Oxidation on Pt-SPE Electrode

h. nakajima and h. kita, Electrochim. Acta, 1988, 33, (4), 521–526

Direct methanol oxidation from the gas phase was studied on a Pt-SPE electrode. The voltammogram and Tafel plots showed that a Pt metal electrode in electrolyte solution and the present Pt-SPE electrode both behave in the same way for methanol oxidation. However, the Pt-SPE electrode produces a 103 times larger oxidation current, and does not deactivate after a few hours polarisation. The burning efficiency of methanol was studied as functions of the potential and the partial pressures of methanol and water. An excess supply of methanol resulted in the production of HCOOCH3 in an amount almost equal to CO2. At a low methanol pressure, complete combustion took place independent of the potential.

Interfacial Electron-Transfer Reactions between Platinum Colloids and Reducing Radicals in Aqueous Solution

a. harriman, g. r. millward, p. neta, m. c. richoux and j. m. thomas, J. Phys. Chem., 1988, 92, (5), 1286–1290

Cyclic voltammetry was used to evaluate redox potentials, diffusion coefficients and heterogeneous electrochemical rate constants for reducing radicals derived from various N-methylbipyridinium ions, N-methylpyridinium ions, aryl ketones and p-nitrobenzoate ion in aqueous solution. The absorption spectra, rates of formation and stabilities of the radicals were found by pulse radiolytic techniques. All these radicals transfer an electron to colloidal Pt particles and the bimolecular rate constants were measured. The size of these rate constants depends upon a number of factors related to mass-transfer and surface processes. The orientation of the support on the metal surface could play a crucial role in the rate of interfacial electron transfer.

Methanol Oxidation on Unsupported and Carbon Supported Pt+Ru Anodes

j. b. goodenough, a. hamnett, b. j. kennedy, r. manoharan and s. a. weeks, J. Electroanal. Chem. Interfacial Electrochem., 1988, 240, (1/2), 133–145

A novel Pt+Ru electrode material was shown to be highly active for the direct electro-oxidation of methanol in H2SO4 solutions, and had little tendency to poison. Spectroscopic study of this material before use as an anode showed that the Ru was oxidised and that there was an important surface concentration of oxidised Pt. After prolonged use as a methanol-oxidation anode, the concentration of oxidised Pt was somewhat increased and there was no evidence for any Pt-CO or Pt2 = CO species; rather adsorbed formate was present. Dispersion of the Pt-Ru on a pure C support showed a much greater performance per gram of precious metal. The initial increase in over-potential was, however, greater by over 100mV.

Permeation of Gases through Poly(Ethylene Terephthalate) Membranes Metallized with Palladium

p. mercea, l. muresan, v. mecea, d. silipas and i. ursu, J. Membrane Sci., 1988, 35, (3), 291–300

Studies were made of the permeations of He, H2, CO2, Ar and N2 at 50°C through poly(ethylene terephthalate) (PET) membranes metallised with Pd layers of 125−1000Å in thickness. It was shown that the Pd layers act as gas barriers which reduce the rate of gas transfer through the polymer by over one order of magnitude. The fact that the Pd layers failed to be perfect gas barriers was attributed to the presence of defects in the structure.

Auger Electron Spectroscopy and Electrochemical Characterization of Au-Pd System in 1M H2SO4

j. genescÁ, m. e. gamboa and l. cota-araiza, Surf.Coat. Technol., 1988, 34, (2), 141–144

An electrochemical study of the Au-Pd system was performed by measuring the O electrosorption properties of Pd surfaces coated with Au by vacuum deposition, in 1 M H2SO4 at 25°C. The properties differed from those of Pd-Au alloy. The crater edge profiles showed an interface a few ångströms thick of a Pd enriched layer, very close to the surface. Between this interface and the bulk of the electrode, Au was predominant, but with a great amount of Pd forming a mixture with the Au.

Electrochemical Studies of Hydrogen in Ordered and Disordered Pd3 Mn Alloy

k. baba, y. sakamoto and t. b. flanagan, J. Chem. Soc., Faraday Trans. I, 1988, 84, (2), 459–466

The solubility of H in ordered and disordered forms of Pd3Mn was studied by electrode potential and electrical resistance measurements following electrochemical introduction of H. The solubility of H in the ordered state was higher than in the disordered state. Diffusion constants were measured, and it was found that the diffusion constant in the disordered form was about a factor of four greater than that for the ordered form at 312K.

Change in the Catalytic Activity and Hydrogen Permeability of the Membrane Catalyst from Palladium-Ruthenium Alloy Induced by Reagents

m. m. ermilova, n. v. orekhova, e. v. skakunova and v. m. gryaznov, Izv. Akad. Nauk SSSR, Ser. Khim., 1988, (4), 750–755

Studies of catalytic activity and H2 permeability in 9.8%Ru-Pd membrane catalysts made during the hydrogenations of cyclopentadiene, cyclooctadiene, isoprene and the hydrogenolysis of propane at 373−573K showed catalytic corrosion of Pd-Ru membrane catalyst determined by nature of reagants. Oxidative-reductive treatment changed in much smaller degree the surface structure, catalytic activity and H2 permeability than alternative treatment.

The Kinetics of Charging and Discharging of Iridium Oxide Films in Aqueous and Non-Aqueous Media

p. g. pickup and v. i. birss, J. Electroanal. Chem. Interfacial. Electrochem., 1988, 240, (1/2), 185–199

The kinetics of oxidation and reduction of electrochemically generated Ir oxide films in H2SO4, basic aqueous LiClO4 solutions and LiClO4+acetonitrile solutions were studied by cyclic voltammetry and chronocoulometry. In acidic and basic aqueous solutions, chronocoulometric measurements showed that electron transport through the oxide was rate limiting for the main redox wave, whereas ion transport probably limits the charging/discharging kinetics in LiClO4+CH3CN solution.

Characterisation of Oxygen Evolving DSA Type Electrode. 1. Ti/IrO2-Ta2O5 Electrode

r. rolewicz, ch. comninellis, e. platiner and j. hinden, Electrochim. Acta, 1988, 33, (4), 573–580

Morphological and crystal structure studies of O2 evolving DSA electrodes Ti/IrO2-Ta2O5 showed agglomerates of epitaxial crystals of IrO2 in the deposits. The catalytic activity and efficiency of the electrodes were a maximum for a composition containing 70%IrO2 and 30%Ta2O5. An increase in catalytic activity and efficiency was due to Ta2O5 addition to the deposit, which resulted in an increase in the number of electrochemically active sites formed.

Electrochemical Reduction of Carbon Dioxide. Characterization of the Formation of Methane at Ru Electrodes in Carbon Dioxide Saturated Aqueous Solution

d. p. summers and k. w. frese, Langmuir, 1988, 4, (1), 51–57

The electrochemical reduction of CO2 to CH4 on electroplated Ru electrodes was studied. Scanning electron micrographs showed that the surface of such an electrode was made up of fused spheroids of Ru divided by a network of cracks. The variations of the CH4 formation rate with pH showed that the rate increase with decreasing pH was due to an increasing H coverage on the electrode, until the coverage became so high that sites for CH4 formation were blocked.

Formation of Bromates at a RuO2/TiO2 Titanium Anode

o. Ű. pavloviĆ, n. v. krstajiĆ and m. d. spasojeviĆ, Surf. Coat. Technol., 1988, 34, (2), 177–179

The production of Na bromate by electrolysis of concentrated Na bromide solution in a cell without a diaphragm using a RuO2/TiO2 Ti anode was studied. The RuO2/TiO2 active coating for the Ti anode was obtained by thermal decomposition of a salt mixture of RuCl3.3H2O and TiCl4 in isopropanol. The current efficiency was high at 98−99% when the pH of the solution was maintained at 8.5−9.5 in the presence of Na2Cr2O7.

PHOTOCONVERSION

A Model of Photon-Induced Self-Driven Electrochemical Cell for Water Splitting to Hydrogen

s. u. m. khan, r. c. kainthla and j. o’m. bockris, Int. J. Hydrogen Energy, 1988, 13, (4), 225–230

An equation for the cell current in a self-driven photon-induced electrochemical cell, with semiconducting photoelectrodes as the electrodes, has been derived and applied to H2O splitting to H2. The cell current and cell potential depend on semiconductor properties and the properties of ions in solution. Computed results show the same trends as experiments. Calculations suggest that an efficiency in the conversion of light up to 18% for H2O splitting to H2 may be possible for p-InP(Pt-electrocatalyst)/n-Si(electrocatalyst).

Effect of Microscopic Discontinuity of Metal Overlayers on the Photovoltages in Metal-Coated Semiconductor-Liquid Junction Photoelectrochemical Cells for Efficient Solar Energy Conversion

y. nakato, k. ueda, h. yano and h. tsubomura, J.Phys.Chem., 1988, 92, (8), 2316–2324

The open circuit photovoltage of a photoelectrochemical cell with a Pt-coated n-Si semiconductor electrode remarkably increased when the Pt layer was made microscopically discontinuous. An open circuit voltage of 0.685 V was obtained for an alkali-etched n-Si electrode with Pt islands 5−20nm wide.

Exciplexes of Ruthenium(II) α -Diimine Complexes with Silver(I)

n. p. ayala, j. n. demas and v. a. degraff, J. Am. Chem. Soc., 1988, 110, (5), 1523–1529

Luminescence “quenching” of RuL32+, where L=2,2′-bipyridine and 4,7-dimethyl-1,10-phena-nthroline, photosensitisers by Ag+ in aqueous solutions proceeds not by oxidative transfer quenching, but predominantly by formation of luminescent exciplexes. The photochemical formation of Ag0(aq) is <0.02 in H2O and <0.05 in acetonitrile. Both form a normal bimolecular exciplex, (RuL2/Ag)3+, and a rare termolecular (RuL3/Ag2)4+ exciplex is seen.

Photochemical CO2 Reduction by an NADH Model Compound in the Presence of [Ru(bpy)3]2+ and [Ru(bpy)2(CO)2]2+ (bpy = 2,2′-bipyridine) in H2O/DMF

h. ishida, k. tanaka and t. tanaka, Chem.Lett.Jpn., 1988, (2), 339–342

Photochemical conversion of CO2 to CO and HCOO was carried out by using nicotinamide adenine dinucleotide model compound, 1-benzyl-1,4-dihydronicotinamide, as an electron donor in the presence of [Ru(bpy)3]2+ and [Ru(bpy)2(CO)2]2+ in H2O/DMF. The quantum yields for the CO and HCOO formation attained 14.8 and 2.7%, respectively, in H2O/DMF (1:9 v/v).

Energy Redistribution and Localization in the Excited States of Ruthenium(II) Polypyridyl Complexes

c. v. kumar, j. k. barton, i. r. gould, n. j. turro and j. van houten, Inorg. Chem., 1988, 27, (4), 648–651

Excited state absorption and resonance Raman spectra of the mixed ligand complexes Ru(bpy)2phen2+ and Ru(bpy)2DIP2+, where DIP = 4,7-diphenyl-phenanthroline, are reported. The spectra show that the excited state electron is localised on individual ligands, but show non-statistical contributions from states corresponding to each of the ligands present in the co-ordination sphere. For these complexes the excited state energy is localised on the ligands in the lowest metal-to-ligand charge transfer state, and is funnelled into the energetically favoured ligand after initial excitation. Thus it becomes possible to design systematically complexes with specific ligands which would absorb at the wavelength of choice, but that would funnel the energy onto a different ligand.

Photosensitized Dissociation of Water Using the System Ru(bipy)32+/TiO2

r. m. quint and n. getoff, Int. J. Hydrogen Energy, 1988, 13, (5), 269–276

The Ru(bipy)32+/H2SO4/n-TiO2 system was investigated to discover its water splitting ability. The effects of initial Ru(bipy)32+ concentration, preparation grain size and amount of TiO2 powder used in suspension were examined. Conditions during system illumination and the pH of the solution were also examined. At prolonged illumination and/or at higher illumination temperatures, ⩽40°C, a relatively strong decomposition of the sensitiser is seen. Yields of O2 and H2 were determined and possible reaction mechanisms are presented.

ELECTRODEPOSITION AND SURFACE COATINGS

Structural and Protective Properties of Rhodium Coatings Obtained by Programmed Pulse Current

v. a. zabludovskii, v. i. kaptanovskii and n. a. kostin, Zashch. Metal., 1988, 24, (2), 255–257

Structural and physicochemical properties were studied of Rh coatings deposited by alternating cathodic and anodic impulse currents from an acidic sulphate electrolyte (containing, in g/l electrolyte): Rh sulphate ratio of 8–10 (calculated on metal) in 90−100% H2SO4, pH∼1, at 20−25°C using Pt anodes and achieving coatings of thickness of 1−20 μ m. The results showed that during cyclic Rh electrodeposition by bipolar-impulse current the microhardness of the Rh coatings increased to 9000MPa and at the same time internal tension decreased to 200MPa. This method also prevented cracking, decreased porosity and increased the rate of Rh coatings deposition. The reliability and durability of electroapparatus contacts were increased.

Surface Study of Ruthenium Dioxide Coatings Stabilized with Valve-Metal Oxides

a. de battisti, m. cappadonia, g. lodi, r. amedelli and c. battaglin, Extended Abstracts, Vol. 88–1, Electrochem. Soc., Spring Meeting, Atlanta, Georgia, May 15–20, 1988, 777–778

Depth profiling of RuO2/TiO2 coatings containing 30, 40, 50, 60, 70 and 80 at.% Ru was performed to find the extent to which surface segregation is a real physical feature. Coatings were obtained either by pyrolysis of RuCl3.xH2O/TiCl4 mixtures or of Ru(NO)(NO3)3/TiCl4. Various techniques of assessment were used.

APPARATUS AND TECHNIQUE

Nernstian Behaviour of Zirconia Oxygen Sensors Incorporating Composite Electrodes

s. p. s. badwal, f. t. ciacchi and j. w. haylock, J. Appl. Electrochem., 1988, 18, (2), 232–239

The Nernstian behaviour of ZrO2 O2 sensors incorporating composite electrodes has been examined in the range <600°C. These electrodes consist of a semiconducting metal oxide and Pt and lower the operating temperature of O2 sensors to ∼300–350°C, which is well below that conventionally used. Impedance measurements show that the electrode resistance and the time constant go through a minimum when plotted against Pt content in the composite.

Formation of Whiskers on the Electrode Surface by the Electrolysis of 3,3′,5,5′-Tetramethylbenzidine

a. watanabe, k. mori, m. mikuni, y. nakamura and o. ito, J. Chem. Soc., Chem. Commun., 1988, (7), 452–453

A fine Pt wire electrode was used in the electrolysis of 3,3′,5,5′-tetramethylbenzidine (TMB), at 60°C; cyclic voltammograms showed two anodic peaks, but no corresponding cathodic peak. By increasing the number of sweeps, needle-like whiskers appeared on the Pt electrode surface, of >1 cm in length.

A New Staining Technique of RuO4 Solution in Organic Solvents for Resolving the Lamella Structure in Polymers

t. cao, s. chen and y. jin, Polymer Commun., 1988, 29, (3), 66–67

A solution of RuO4 in CCl4 was used as a staining medium for resolving the lamella structure in both polyethylene and polypropylene with the transmission electron microscope. Staining in the organic medium was more efficient than in the vapour phase of an aqueous solution of RuO4 and was more convenient than in the vapour of solid crystalline RuO4 for both polymers. The organic solution of RuO4 appears to be a universal staining medium for revealing the fine morphology in hydrophobic polymers.

HETEROGENEOUS CATALYSIS

Another Strong Metal-Support Interaction: High Intrinsic Methanation Activity of an Alumina-Supported Platinum Catalyst after High Temperature Reduction without Loss of Chemisorption Ability

s. taniguchi, t. mori, y. mori, t. hattori and y. murakami, J. Chem. Soc., Chem. Commun., 1988, (10, 630–631

Pulse surface reaction rate analysis measurements showed that the intrinsic methanation activity of 0.5%Pt/Al2O3 catalyst was increased by high temperature reduction (HTR) without a marked reduction in its chemisorption ability. The rate constant for methanation after HTR was about five times as large as that after reduction at 523K (low temperature reduction, LTR). Heating the catalyst with high methanation activity in flowing O2 followed by LTR caused the rate constant to decrease to near the original value. The rate constant determined by these analyses was not affected by the number of active sites on the catalyst. The changes in methanation activity caused by HTR were reversible but not permanent.

Study of Catalytic Activity in the Reaction of Complete Oxidation of Butane and State of Platinum in Platinum/Alumina Catalysts Modified by Lanthanum and Cerium

v. a. drozdov, p. g. tsyrul’nikov, a. n. pestryakov, a. a. davydov and v. v. popovskii, Kinet. Katal., 1988, 29, (2), 484–488

A study of the effect of the addition of La and Ce oxides to 2.53wt.%Pt/Al2O3 catalysts at 523−623K on the catalytic activity during complete oxidation of butane showed that this addition greatly increased the dispersion and stability of the deposited Pt during superheating. The electronic state of Pt surface atoms and of studied samples after various treatments was established spectroscopically. The results showed that adding Ce oxide to Pt depresses reduction in favour of oxidation, compared to unmodified Pt.

Mass-Spectroscopy Study of Products of Thermodesorption with 0.3%Pt/γ -Al2O3 Catalyst

a. a. ivko and s. v. markevich, Vestn. Akad. Navuk BSSR, Ser. Khim. Navuk, 1988, (1), 18–21

Mass-spectroscopy studies were performed of the gassing and thermodesorbed products formed during benzene hydrogenation to cyclohexane over 0.3%Pt/γ -Al2O3 catalyst, which is the primary reaction stage of the industrial production of caprolactams. A temperature dependence of the yields was also studied. Cyclohexane dehydrogenation to benzene occurred at low temperatures. The results showed that coal formation goes on in spent catalysts if they are heat treated in vacuum.

On the Influence of Sulphur on the Activity and Selectivity of Reforming Catalysts in the Conversion of Methylcyclopentane

m. wilde, t. stolz, r. feldhaus and k. anders, Chem. Tech. (Leipzig), 1988, 40, (4), 166–169

The conversion of methylcyclopentane at atmospheric pressure was investigated for Pt/Al2O3, Pt-Re/Al2O3 and Pt-Re-Cr/Al2O3 as a function of their pretreatments. Presulphidation caused very high conversions, high yields of cyclenes, aromatics and H2, and hence enhanced coke formation. With self-poisoning, S stabilises the hydrogenation/dehydrogenation reactions of the catalysts. Reactivation with CCl4 in air increases the total conversions; and the cracking activity increases. For best results, the reaction should be performed after presulphidation when the catalysts contain high Cl contents.

Skeletal Catalysts on Supports. II. Formation and Structure of Pt-Cu/Al2O3 Raney Catalysts

g. m. khutoretskaya, v. n. ermolaev and a. b. fasman, Kinet. Katal., 1988, 29, (1), 180–184

The porous structure of Pt-Cu/Al2O3 Raney catalysts was studied by a low-temperature adsorption method and by capillary condensation of Ar. The treatment of the catalyst with 5% HNO3 increased specific surface and porosity at the expense of dissolving part of the γ -Al2O3 and Cu. The rest of the Cu was redispersed in the pores of the catalyst, stabilising and forming β -CuAlO2. During the catalyst preparation highly dispersed surfaces were formed. It is suggested that Cu ions fixed in the lattice of γ -Al2O3 become centres of stability for migrating Pt atoms.

The Adsorption of Oxygen and the Oxidation of Methanol on Silver-Platinum Alloys

s. dong, f. xiao and j. deng, J. Catal., 1988, 109, (1), 170–179

The effects on the adsorption and oxidation of methanol on Ag of alloying Pt with Ag were examined spectroscopically. Ag-Pt alloys containing <9.7 at.% Pt were prepared. Two kinds of adsorption states of O were found on the surface of the alloys by XPS and TDS techniques. The catalytic activity and selectivity for oxidising methanol were measured.

Selective Hydrogenation of CO into C1 and C2 Alcohols by SiO2-Supported RhFe, PtFe, and PdFe Bimetallic Cluster-Derived Catalysts

a. fukuoka, t. kimura and m. ichikawa, J. Chem. Soc., Chem. Commun., 1988, (6), 428–430

Evidence for the potential benefits of SiO2-supported Rh4Fe, Rh4Fe2, Pt3Fe3, PtFe4, Pd6Fe6 and PdFe4 carbonyl clusters as precursors for the preparation of tailored bimetallic catalysts is presented. The derived catalysts exhibit high catalytic activities and selectivities for the formation of oxygenates, consisting mainly of methanol and ethanol from CO + H2.

The Effect of the Carrier Modification by γ -Alumina on Palladium Catalyst Properties

v. m. vlasenko, v. a. kuznetsov, i. a. mal’chevskii, l. v. palamarchuk and g. v. filonenko, Dokl. Akad. Nauk USSR, Ser. B, 1988, (3), 40–43

Studies were made of the effect of modification of 0.4%Pd/α -Al2O3 catalyst by γ -Al2O3 on its properties. The results showed the existence of an optimal concentration of γ -Al2O3 at which the maximum dispersity of Pd particles and the highest value of its specific catalytic activity were observed.

The Conversion of Polysaccharides to Hydrogen Gas. Part 1: The Palladium Catalysed Decomposition of Formic Acid/Sodium Formate Solutions

s. p. hill and j. m. winterbottom, J. Chem. Tech. Biotechnol., 1988, 41, (2), 121–133

Studies of catalytic decomposition of solutions containing formic acid and Na formate to H2 + CO2 over 5% w/w Pd/charcoal catalyst was studied in a stirred reactor at 60−90°C. The production of H2 gas was optimum in the pH range 3.8−6.5 and the order of reaction varied with the solution composition from 0.33(100mol% formic acid) to 1.07(100mol% formate ion). Energies of activation were in the range 20.9±5 to 41.8±7kJ/mol, the larger values occurring at the ends of the composition range.

Study of Dealkylation of meta-Cresol on Alumina-Supported Rhodium, Nickel and Palladium Catalysts

m. assafi and d. duprez, Bull. Soc. Chim. Fr., 1988, (1), 106–112

The meta-cresol steam dealkylation on Al2O3-supported Rh (0.6wt.%), Pd(0.6wt.%) and Ni(11.4wt.%) catalysts was performed in a dynamic reactor at 440°C, at atmospheric pressure and weight hourly space velocity of 2 to 20/h. The results were compared to the performance of the same catalysts in toluene steam reforming. The formation of acid-like reaction products was observed in significant proportions, even on the bare support. This was explained as being due to the ability of the cresol molecule to be protonated on the aromatic ring. The relative activity order was: Rh100>Pd25>Ni13.

Catalytic Activity of Supported Liquid-Phase Lithium-Palladium Acetate Catalysts in the Oxidation of Ethylene to Vinyl Acetate

s. a. h. zaidi, Appl. Catal., 1988, 38, (2), 353–358

The effect of different liquid loadings in catalysts containing solutions of Li-Pd acetates on C was studied in the selective oxidation of ethylene to vinyl acetate at 428−463K. The oxidation reaction appeared to take place in an acetic acid film on the periphery of the C particles and the site of activity of these supported solutions seems to lie in between the micro- and macropores of the C support.

Syntheses and Characterization of Mercapto-Hydroxyl-Palladium Macromolecular Chelates and Their Catalytic Properties

y. wang and h. liu, J. Mol. Catal., 1988, 45, (1), 127–142

A Pd complex with an unusual macromolecular mercapto-hydroxyl bidentate ligand was prepared by the reaction of epoxy-phenolic oligomer with H2S and was then characterised spectroscopically. The catalytic behaviour of macromolecular Pd chelate complexes absorbed on a SiO2 support was studied by the Heck reaction. The activity of the chelates depended on the molar ratio of S:Pd, and an active catalyst was obtained at a S:Pd ratio of 2. The catalyst was inactive at ratios of 6 or greater. The catalyst had better stability than other polymeric Pd catalysts.

Iron or Lanthanum Promoters on the Selectivity of Palladium Zeolites in Methanol Synthesis

b. m. choudary, k. lÁzÁr, k. matusek, and l. guczi, J. Chem. Soc., Chem. Commun., 1988, (9), 592–594

The first example showing a distinct shift in selectivity towards methanol formation during CO hydrogenation on addition of Fe or La to Pd zeolite catalysts, and giving enhanced activity is reported.

Catalytic Oxidation of CO on Rh/SiO2: A Rapid-Response Fourier Transform Infrared Transient Study

y. -e. li and r. d. gonzalez, J. Phys. Chem., 1988, 92, (6), 1589–1595

The catalytic oxidation of CO was studied over Rh/SiO2 by using a FTIR-mass spectrometric technique. The reactivity of linearly adsorbed CO was considerably greater than that of the dicarbonyl species at both 85 and 200°C. The oxidation of CO over Rh/SiO2 proceeded through a mixed O-CO adlayer. Induction times required for the formation of gas-phase CO2 were nearly 2 orders of magnitude lower than those observed for Pt/SiO2 and Pd/SiO2. Self-sustained CO-O2 oscillations reinforced the greater reactivity of linearly adsorbed CO. H2-CO-O2 transient studies also suggest the formation of mixed H-CO adlayers.

Selective Formation of Lower Alkenes and Alcohols in CO + H2 Reaction Catalysed on NaY Zeolite-Encapsulated Rh6 and RhFe Bimetallic Cluster-Derived Catalysts

l. -f. rao, a. fukuoka and m. ichikawa, J. Chem. Soc., Chem. Commun., 1988, (7), 458–460

Rh6, Fe3 and bimetallic RhFe clusters encapsulated in NaY zeolite were characterised and examined in the CO + H2 reaction under atmospheric pressure. The Rh6 clusters led to the formation of C2-C4 alkenes, whereas the entrapped RhFe clusters had a higher selectivity for C1-C2 alcohol formation.

Design of Fischer-Tropsch Catalysts by Pulse Surface Reaction Rate Analysis. II. Selective Production of Liquid Fuel Fraction on Ruthenium/Alumina Catalyst Promoted by Rare Earth Oxides

n. takahashi, t. mori, a. miyamoto, t. hattori and y. murakami, Appl. Catal., 1988, 38, (1), 61–69

Different rare earth oxides were tried as promoters of Ru/Al2O3 Fischer-Tropsch catalysts for the selective production of liquid fuels via the hydrogenation of CO. Rare earth oxide additions resulted in an increase in the turnover frequency, and an increase in the selectivity for the production of higher hydrocarbons.

Direct Synthesis of Alcohols from Syngas on Ru-Mo-Na2O/Al2O3 Catalysts: Synergistic Effect of Ru and Mo

m. inoue, t. miyake, s. yonezawa, d. medhanavyn, y. takegami and t. inui, J. Mol. Catal., 1988, 45, (1), 111–126

Direct synthesis of alcohols from syngas on Ru-Mo-Na2O/Al2O3 catalysts was studied at 255°C under 86kg/cm2 pressure. The results showed that close contact between Ru and Mo particles was essential for the formation of alcohols. Combining Na2O with the Ru-Mo catalyst decreased the catalytic activity but increased the selectivity for alcohols, together with a slight increase in propagation probability for alcohol products.

Wet Oxidation Catalyzed by Ruthenium Supported on Cerium(IV) Oxides

s. imamura, i. fukuda and s. ishida, Ind. Eng. Chem. Res., 1988, 27, (4), 718–721

The activity of various noble metal catalysts was investigated for the wet oxidation of organic compounds, in order that a more effective way of treating highly contaminated waste waters could be found. Ru was the most effective catalyst tried, and Ce(IV) oxide the most effective support. The Ru/Ce catalyst rivalled homogeneous Cu catalyst which is used for waste water treatment, for the oxidation of n-propyl alcohol, n-butyl alcohol, phenol, acetamide, etc. It was especially effective for the oxidation of some high O-containing compounds, such as poly(ethylene glycol), ethylene glycol, etc.

Hydrogenation and Acetalization of Cyclohexanone over Platinum Group Metal Catalysts in the Presence of Ethylene Glycol

j.-i. ishiyama, k. esashika, y. senda and s. imaizumi, Nippon Kagaku Kaishi, 1988, (1), 126–128

The hydrogenation of cyclohexanone was performed under atmospheric or high H2 pressure (100kg/cm2) at 70°C over platinum group metal catalysts in the presence of ethylene glycol. Although only hydrogenated product (cyclohexanol) was detected over Os, Ir, and Pt catalysts, the rapid formation of acetal was observed over Ru, Rh and especially Pd catalysts under H conditions.

HOMOGENEOUS CATALYSIS

Homogeneous Catalysis of the Water-Gas Shift Reaction

r. m. laine and e. j. crawford, J. Mol. Catal., 1988, 44, (3), 357–387

A review is given of the advances in homogeneous catalysis of the water-gas shift reaction (WGSR) in the presence of platinum group metals published during the last 10 years. Topics discussed include transition metal catalysis of the WGSR under both acidic and basic conditions, as well as areas of special interest such as mixed-metal catalysis and catalyst tolerance toward S contaminants. (96 Refs.)

Reversible Homogeneous Catalysis of Carbon Dioxide Hydrogenation/Reduction at Room Temperature and Low Pressures

s. schreiner, j. y. yu and l. vaska, J. Chem. Soc., Chem. Commun., 1988, (9), 602–603

The Pt complex, [Pt2(μ -dppm)3], where dppm = Ph2PCH2PPh2, is an effective catalyst under unprecedented mild conditions in toluene solution for the reaction between CO2, H2 and Me2NH to yield dimethyl formamide and H2O. The catalysis is readily reversible, which is unusual.

Allylation of Active Methylene Compounds with Allyl Oxime Carbonates Catalyzed by Pd(O)

o. suzuki, y. hashiguchi, s. inoue and k. sato, Chem. Lett. Jpn., 1988, (2), 291–294

Allylation of active methylene compounds catalysed by a Pd(0)-phosphine system using Pd(dba)2 (dba = dibenzylideneacetone) catalyst and diphenylphosphinoethane was performed with high stereoselectivity by employing allyl oxime carbonates as the allylating reagent. Higher stereoselectivity was obtained by using triphenylphosphine as an additive ligand, but regioselectivity was lowered.

Highly Efficient Total Synthesis of Manoalide and Seco-Manoalide via Pd(0) Catalyzed Coupling of Allylhalide with CO and 2-Silyl-4-Stannylfuran

s. katsumura, s. fujiwara and s. isoe, Tetrahedron Lett., 1988, 29, (10, 1173–1176

Improved and highly efficient total synthesis of manoalide and seco-manoalide from an allylchloride derivative was achieved by 6 steps in 56.4% overall yield by Pd(0) catalysed coupling with CO and 2-trimethylsilyl-4-tributylstannylfuran followed by chemoselective oxidation of 2-trimethylsilylfuran with singlet O. This synthesis of these unique sesterterpenoids promises not only to supply enough quantities of these biologically important pentaprenoids but also to make possible the synthesis of various analogs of manoalide. The seco-manoalide inhibits both phospholipase A2 and aldose reductase more strongly than manoalide in vitro.

Substitute Carbonylation of Organic Compounds Catalysed by Palladium Complexes

yu. v. gulevich, n. a. bumachin and i. p. beletskaya, Usp. Khim., 1988, 57, (4), 529–561

A review is given of substitute carbonylation of element-organic compounds, organic halides and other substrates of the type RX, in which X converted to CO during reaction catalysed by Pd complexes. The mechanism of the reaction behaviour of Pd complexes during carbonylation was discussed. The use of the substitute carbonylation reaction in organic synthesis was emphasised. (141 Refs.)

Study of Kinetics and Mechanism of Oxidative Acetoxylation of Propylene Catalysed by Pd(II)

v. i. emel’yanov, s. d. asriev, a. s. sobolov, b. v. fal’kovskii, b. ya. stul’, a. v. borisov and b. b. cheshokov, Kinet. Katal., 1988, 29, (1), 103–109

A kinetic study of oxidative acetoxylation of propylene, by O2 in acetic acid in the presence of PdCl2 catalyst and nitrate ions at 50−85°C and various NO3:Pd(II) and propylene:O2 ratios, showed the formation of monoacetate propylene glycols. The reaction of propylene and Pd(II) was found to be first order. The obtained kinetic data agree with a mechanical reaction forming intermediate Pd nitrite complexes with propylene.

Palladium(0)-Catalyzed Isomerization α,β -Epoxy Ketones to β -Diketones

m. suzuki, a. watanabe and r. noyori, Red. Trav. Chim. Pays-Bas, 1988, 107, (3), 230–236

Studies of the isomerisation of α,β -epoxy ketones in the presence of catalytic amounts of tetrakis(triphenylphosphine)Pd(0) and 1,2,-bis(diphenylphosphino)ethane showed the formation of the corresponding β -diketones in high yields. Both open-chain and cyclic substrates could be used. Possible reaction mechanisms were discussed.

Highly Catalytic Dehydrogenation of Alkanes to Olefins via C-H Activation in the Presence of RhCl(CO)(PMe3)2 under Irradiation

t. sakakura, t. sodeyama, y. tokunaga and m. tanaka, Chem. Lett. Jpn., 1988, (2), 263–264

Olefins and H2 were catalytically formed from alkanes in the presence of RhCl(CO)(PMe3)2 under irradiation by a 100W high pressure Hg lamp at ambient temperature for 16.5h. The irradiation was performed under N2 atmosphere in a closed system. The results showed the formation of cyclohexene (138 turnovers) and benzene (3 turnovers). A nearly theoretical amount of H2 (132 turnovers) was detected in the gas phase. The article gives the first example of a practical productive dehydrogenation of alkanes via the transition metal complex catalysed C-H activation. The system does not require a H acceptor and shows high catalytic activity.

Remarkable Effect of the Wavelength in the Photoassisted Carbonylation of the C-H Bond of Decane in the Presence of RhCl(CO)(PR3)2 as the Catalyst

t. sakakura, k. sasaki, y. tokunaga, k. wada and m. tanaka, Chem. Lett. Jpn., 1988, (1), 155–158

Studies of the carbonylation of the C-H bond of decane performed in the presence of RhCl(CO)(PR3)2 catalyst under irradiation by a 500W high pressure Hg lamp showed the formation of C11 aldehydes and/or 1-nonene, depending on the wavelength. Irradiation with λ >295nm was essential to the formation of 1-nonene and undecanal. By cutting off λ <325nm, 1-nonene formation was completely suppressed and a series of isomeric C11 aldehydes was obtained.

High Deoxygenation Ability of Rh Carbonyl Clusters toward Oximes Leading to Nitrile Formation

k. kaneda, k. doken and t. imanaka, Chem. Lett. Jpn., 1988, (2), 285–286

Nitriles were selectively prepared by the reaction of aldoximes with CO and H2O in the presence of Rh6(CO)16 cluster catalysts. The i.r. spectra studies of the condensed reaction mixture showed the formation of Rh12 and Rh13 carbonyl cluster anions.

Iridium-Catalysed Hydrosilylation of Hex-l-yne: The Unusual Formation of l-Triethylsilylhex-l-yne

m. j. fernandez, l. a. oro and b. r. manzano, J. Mol. Catal, 1988, 45, (1), 7–15

Hex-1-yne reacted with triethylsilane in the presence of IrH2(SiEt3)(COD)(AsPh3) or Ir catalysts formed by adding triarylarsines (L) or triarylphosphines (L) to [Ir(OMe)(diolefin)]2. The catalytic products were the expected trans- and cis-1-triethylsilylhex-1-enes, as well as significant amounts of 1-triethylsilylhex-1-yne and hex-1-ene. The formation of alkynyltriethylsilanes from alkynes, and alkenyltriethylsilanes from alkenes is a characteristic of the [Ir(OMe)(diolefin)]2 + nL systems. Mechanistic pathways for the observed hydrosilylation reaction were discussed.

Selective Hydrogenation of PhCH = CHCOMe to the Unsaturated Alcohol Catalysed by [IrH3(PR3)3] (R = Alkyl or Aryl)

e. farnetti, j. kašpar, r. spogliarich and m. graziani, J. Chem. Soc., Dalton Trans., 1988, (4), 947–952

The selective hydrogenation of (PhCH = CHCOMe) catalysed by Ir-phosphine systems prepared in situ is reported. Different species are formed depending on the P:Ir ratio and on the steric properties of the phosphine. [IrH5(PR3)2] (R = alkyl or aryl) is a catalyst for the hydrogenation of the C = C bond, whereas [IrH3(PR3)3] catalyses the reduction of the carbonyl group with a selectivity up to 100%.

Asymmetric Dihydroxylation via Ligand-Accelerated Catalysis

e. n. jacobsen, i. markÓ, w. s. mungall, g. schrÖder and k. b. sharpless, J. Am. Chem. Soc., 1988, 110, (6), 1968–1970

A new catalytic asymmetric dihydroxylation between olefins and OsO4 which gives substantially improved rates of reaction and turnover numbers and useful levels of asymmetric induction, is reported. When the process is performed in the presence of alkaloid an OsO4-alkaloid complex is formed, which is far more reactive than OsO4 alone. The alkaloid acts as an accelerator of the dihydroxylation catalysis by binding strongly enough to accelerate addition to olefins.

Ruthenium Carbonyl Catalysed Reductive Carbonylation of Aromatic Nitro Compounds. A Selective Route to Carbamates

s. cenini, c. crotti, m. pizzotti and f. porta, J. Org. Chem., 1988, 53, (6), 1243–1250

Ru3(CO)12 and Ru(CO)3(PPh3)2 catalysed the reductive carbonylation of nitrobenzene and substituted aromatic mononitro compounds to give the corresponding methylcarbamates, in toluenemethanol, at 160−170°C and 60atm, with high selectivity in the presence of NEt4 +Cl as co-catalyst. This catalytic system works in relatively mild conditions, and it is one of the most selective reported. The effects of CO pressure, reaction temperature, and amount and nature of the added alcohol and cocatalyst were studied.

Homogeneous Catalytic Hydrogenation of the Esters of Bicarboxylic Acids. Part III. Ethylene Glycol from Dimethyl Oxalate

u. matteoli, g. menchi, m. bianchi and f. piacenti, J. Mol. Catal., 1988, 44, (3), 347–355

Dimethyl oxalate was hydrogenated in the presence of Ru(CO)2(CH3COO)2 (PBu3)2 to methyl glycolate, which was subsequently reduced at a much slower rate to ethylene glycol. This reduction was affected by high H2 pressure and pretreatment of the catalytic system with a hydroxylated reactant, such as methyl glycolate or ethylene glycol itself. Under optimum conditions a 95% conversion of dimethyl oxalate to the corresponding glycol was achieved.

The Photochemical Carbonylation of Benzene, and Hydrogenation and Hydrosilation of Benzaldehyde Catalyzed by Ruthenium(0) Complexes

e. m. gordon and r. eisenberg, J. Mol. Catal., 1988, 45, (1), 57–71

The activation and functionalisation of an arene C-H bond was achieved in the photochemical carbonylation of benzene catalysed by the Ru(0) complexes RuCl(CO)(NO)(PPh3)2(1), Ru(CO)3(PPh3)2(2) and Ru(CO)4(PPh3)(3). Under the carbonylation conditions, both (1) and (2) converted to Ru(CO)4(PPh3).

Oxygen Evolution by Means of Water Oxidation Catalyzed by Mononuclear Ruthenium-Ammine Complexes

m. kaneko, r. ramaraj and a. kira, Bull. Chem. Soc. Jpn., 1988, 61, (2), 417–421

Oxidation of H2O was achieved catalytically by the use of mononuclear Ru-ammine complexes [Ru(NH3)5Cl]2+ and [Ru(NH3)5(H2O)]3+, with Ce(IV) as an oxidant. Cyclic voltammetric studies of the mononuclear Ru-ammine complexes were performed using Basal Plane Pyrolytic Graphite (BPG) coated with poly(p-styrenesulphonate), Nafion or kaolin clay. The electrochemical properties of these Ru-ammine complexes show that they can be used as two-electron oxidants for H2O oxidation. The H2O oxidation depended on the ionic strength of the media; higher acidic conditions gave higher O2 yields. However, heterogeneous catalysis with the Ru complex in kaolin was as effective as homogeneous.

FUEL CELLS

Platinum Supported on Silicon Carbide as Fuel Cell Electrocatalyst

a. honji, t. mori, y. hishinuma and k. kurita, J. Electrochem. Soc., 1988, 135, (4), 917–918

SiC was evaluated as the support in phosphoric acid fuel cells to see if it prevents Pt particle agglomeration. C black was incorporated into the catalyst layer to achieve electrical conduction. Electrodes were fabricated, O2 was reduced, Pt particle dispersion was examined by TEM and Pt particle diameter was measured by X-ray diffraction. Results indicate that Pt/SiC could be a potential support for phosphoric acid fuel cells, but that the method of preparation and electrode fabrication need to be optimised.

Methods to Attain High Power Densities in Solid Polymer Electrolyte Fuel Cells Using Low Platinum Loading Electrodes

e. a. ticianelli, c. r. derouin, w.-k. paik and s. srinivasan, Extended Abstracts, Vol. 88–1, Electrochem. Soc., Spring Meeting, Atlanta, Georgia, May 15–20, 1988, 2–3

Methods of attaining high power densities in SPE fuel cells are discussed. The optimisation of the Nafion film impregnated into the electrode and the optimal hot pressing conditions between Nafion and electrode are considered. For stable long term performance, O2 or air should be humidified at 10−15°C, and H2 at 10−15°C, above the cell temperature. Localisation of Pt near the front surface of the electrode, which is most effective for high power densities, is achieved by two methods, giving total Pt loadings <0.5 mg/cm2. Sputtering Pt onto a standard electrode enhanced the power density by 100−150%; and cells with 20−40 wt.% Pt/C electrodes had a better performance than those with 10 wt.% Pt/C. However, sputtering a Pt film onto 20 wt.% Pt/C gave the highest power densities. A stable performance of 1000h occurred at 300 and 500 mA/cm2.

Change of Pt Distribution in the Active Components of Phosphoric Acid Fuel Cell

j. aragane, t. murahashi and t. odaka, J. Electrochem. Soc., 1988, 135, (4), 844–850

The changes in Pt distributions in the active components, in phosphoric acid fuel cells were investigated after long term use. Electron probe microanalysis shows Pt loss in the cathode and also Pt migration to the anode during operation and identifies Pt in the matrix.

CORROSION PROTECTION

Passivating Ability and Corrosion Stability of Stainless Steel Surface-Alloyed by Palladium by Vacuum Condensation Method

g. p. chernova, t. a. fedoseeva and n. d. tomashov, Zashch. Met., 1988, 24, (2), 199–203

Studies of the electrochemical and corrosion behaviours of stainless steel after surface alloying with Pd applied by a vacuum condensation method and then followed by diffusion annealing of the sample, were performed in 10 and 20%H2SO4 at 25−100°C. The results showed an increase in corrosion stability by several orders of magnitude in the stainless steel after surface modification by Pd.

CHEMICAL TECHNOLOGY

The Preparation of Chloroplatinic Acid Labelled with Platinum Radioisotopes

a. b. malinin, n. v. kurenkov, m. d. kozlova and a. s. sevastyanova, J. Radioanal. Nucl. Chem., Lett., 1988, 126, (1), 17–25

After the extraction of 199Au impurities, natural metallic Pt, which has been irradiated in a nuclear reactor, may be used for the preparation of labelled hexachloroplatinic acid, which is then utilised for the synthesis of various anti-tumour compounds.

“Tailored” Organometallics as Precursors for the Chemical Vapor Deposition of High-Purity Palladium and Platinum Thin Films

j. e. gozum, d. m. pollina, j. a. jensen and g. s. girolami, J. Am. Chem. Soc., 1988, 110, (8), 2688–2689

The synthesis of high-quality Pd and Pt thin films by metal-organic chemical vapour deposition (MOCVD), from “tailored” organometallic precursors under mild conditions, for use in electronic devices, is reported. Three organo-Pd compounds were studied as potential precursors for Pd thin films. CVD was conducted at 250°C and 10−4 torr, and bright silvery metallic films up to 2μ m thick were grown on a variety of substrates. Electrical conductivity measurements were performed.

ELECTRICAL AND ELECTRONIC ENGINEERING

Contact Voltage Drop and Wear of Self-Lubricating Ag-Pd Alloy Base Composite Materials

k. okada and m. yoshida, IEEE Trans. Components, Hybrids, Manuf. Technol., 1988, 11, (1), 116–123

New wrought self-lubricating Ag-Pd alloy base composite materials containing graphite are described and the contact voltage drop, wear and friction of the new self-lubricating brushes and the metal alloy slip rings were studied. The results showed that since a thin graphite film of about 100Å existed on the contact boundary surface for the 10%Pd-5%C-Ag brush and the Cu-10%Ag slip ring, both the friction coefficient and the specific wear rate became small.

Low Dielectric Constant Multilayer Glass-Ceramic Substrate with Ag-Pd Wiring for VLSI Package

y. shimada, y. yamashita and h. takamizawa, IEEE Trans. Components, Hybrids., Manuf. Technol., 1988, 11, (1), 163–170

New glass-ceramic materials, with low dielectric constant, which could be sintered at about 900°C in air, have been developed by means of green sheet technologies using Ag-Pd wiring.

Phase Transitions in Ru Based Thick-Film (Cermet) Resistors

b. morten, m. prudenziati, m. sacchi and f. sirotti, J. Appl. Phys., 1988, 63, (7), 2267–2271

Thick-film resistive inks were prepared starting from powders obtained by precipitation of RuCl3 on two different lead-containing glasses. The structural and electrical properties of the films were studied after heat treatment at various temperatures. The evolution of the microstructure involved phase transformations from Pb-rich (Ru-deficient) pyrochlores to Ru pyrochlores and finally to RuO2.

TEMPERATURE MEASUREMENT

Forehearth Temperature Gradient Measurements with Thermocouples

d. a. toenshoff and c. j. steer, Glass, 1988, 65, (4), 135–136, 139

The effective use of thermocouples in the glass container industry is briefly reviewed. The problem of the short life of thermocouples immersed in amber glass has been investigated, and a solution found. Intergranular fracture of Pt-10%Rh thermocouple sheaths was associated with Rh-S formation at the grain boundaries. This compound dissolves readily in the glass, producing voids which connect together and cause grains to fall off. The use of a Pt-Au alloy or Pt strengthened by the dispersion of an oxide avoids premature failures from Rh.

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