ABSTRACTS of current literature on the platinum metals

PROPERTIES Metal Substrates Wetting by Indium. 11. In-Pt System J . JANDOVA and J . D U ~ N , Kovovi Mater., 1988, 26, (I), 71-75 Studies of Pt wettability by liquid In at 4w°C showed that after 30 min In fully dissolved in Pt forming In,Pt intermetallic compound. The wetting angle during the starting period (the first 30 mh) was determined as 86k3 rad.

Thermally and Ion-Induced Reaction bet- ween Si and Binary Metallic Alloys L. S. HUNG, Q. 2. HONC and J. W . MAYER, J . Appl. phyx., 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 approx- imately equiatomic compositions, were investigated. Thermal annealing was performed at ~w-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 2w-4w°C. Uniform mixed amorphous layers were produced in all three systems upon ir- radiation at relatively low temperatures. Mixtures PtVSi, and NiTaSi, were transformed to separated binary silicides by post-annealing, but the PtTiSi, underwent an amorphous-metastable phase transfor- mation. 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 Selectivi- ty of Alcohol Conversion on the Pd( 11 1) Surface J. L. DAVIS and M. A. BARTEAU, surf. SCl., 1988, 197, (1/2), 123-152 The reactions of methanol, ethanol, I-propanol and 2-propanol were studied on a Pd(11x) surface con- taining one-quarter monolayer of adsorbed 0 atoms. Methanol was oxidised on the 0-dosed Pd( I I I) sur- face to formaldehyde and surface formate species. The adsorption of ethanol on the 0-dosed Pd( I I I) surface resulted in the desorption of acetaldehyde at 220K and the formation of surface acetate species. Adsorbed acetate species reacted, via either decom- position at 41oK 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(x 11) produced both propanal and adsorbed propanoate species. The roles of 0 adatoms in these reactions were discussed.

The the

and their alloys

Effect of Nitrogen Implantation on Tribolodcal Properties of Gold-

Based AlGys and Electroplated Palladium P. w. LEECH, IEEE Trans. Components, Hybrids, Manuf. Technol., 1988, 11, (I), 16-21 The effect of N , + ion implantation on the friction and wear behaviour of 30%Pd-29.~~/oAg-1 .s%Sn-Au, 26%Ag-3%Ni-Au and B%Ag-Au alloys and elec- troplated Pd was studied. Rider-on-flat experiments showed that N , + implantation in either the rider in B%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 N , + implantation of both surfaces.

Change of Structure and Properties dur- ing Annealing of Cold Worked Pd-Fe Alloy E. I. TEITEL’ and G. M. GUSHCHIN, Fiz.Met.Metallov- ed., 1988, 65, (21, 332-340 Structural changes and their effect on elec- troresistance, magnetic and mechanical properties were studied during annealing of cold worked Pd-Fe alloys at 5 0 0 O 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 elec- troresistance, coercive force and mechanical proper- ties 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 E n e w , 1988, 13, (3), 191-194 The H, 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 o to 7 at- mospheric pressure and at room temperature up to 400OC. 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(AH,,AS,) 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.

Platinum Metals Rev. , 1988, 32, (3), 148-159 148

Growth Kinetics of Palladium Silicides Formed by Rapid Thermal Annealing

Electmchem. SOC., 1988, 135, (2), 446-451 Pd,Si is formed through direct reaction of an electron-evaporated Pd thin fdm and single-crystal <roo> Si substrate by rapid thermal annealing. The sample temperatures were measured by a variety of means, and the maximum sample temperatures, were 310-460OC. Pd,Si is the first and only phase in this range and forms at 320OC. The activation energy for the diffusion-controlled silicide growth is I .420.2eV. Thus the growth mechanism of Pd ! Si is the same in both rapid thermal annealing and conventional fur- nace annealing.

Reordering of Polycrystalline Pd2 Si on Epitaxial Pd Si

J.Appl.Phys., 1988, 63, (7), 2402-2405 Polycrystalline Pd , Si was found to reorder on top of epitaxial Pd, Si during silicide growth. The interface between polycrystalline Pd , Si and epitaxial Pd , Si was thus not immobile with respect to the silicide lat- tice during silicide formation. It was not, therefore, possible to use this interface as a structural marker in order to monitor diffusion in epitaxial Pd, Si. The use of Ti as an inert marker showed that Si was the domi- nant diffusing species in epitaxial Pd,Si during silicide formation.

Ultrasonic Study of Mechanically Alloyed Amorphous PdSiCu A. HIKATA, M. 1. MCKENNA and c . ELBAUM, 3. Appl.Phys., 1988, 63, (6), 1910-1913 An amorphous alloy Pd,,,, Sio,,6sCuo.a has been pro- duced by a mechanical alloying process which in- volves repeatedly deforming, fragmenting and cold welding appropriate amounts of the constituent powders by milling with steel balls in an argon at- mosphere, at around room temperature. X-ray dif- fraction 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, (IS), h 1 - U 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 T,, a y value of 470 and z40mJ/molKz was obtained for YbPdBi and YbPdSb, respectively. The magnetic susceptibility results reflected the fluc- tuating nature of the valence of Yb ions in both com- pounds.

C. S. WEI, J. VAN DER SPIEGEL and J. J . SANTIAGO, J .

C. M. COMRIE, 1. C. LIU, L. S. HUNG and J. W. MAYER,

A Comparison of the Desorption of CO from Pt and Rh Particles on a- A1,0,{0001} E. I. ALTMAN and R. J. GORTE, surf. sci . , 1988, 195, (3), 392-402 The adsorption of CO on Rh particles supported on (Y-AI, O,{ooor} was studied using temperature pro- grammed desorption. The Rh was evaporated onto the non-porous a-AI,O, substrate in ultra-high vacuum and metal coverage was measured using a quartz-crystal, fdm thickness monitor. Spectroscopic studies showed that Rh grew as three-dimensional particles on the alumina substrate at 3ooK. For all Rh particle sizes studied, CO desorbed in peaks at 500 and 425K, which were the same temperatures observ- ed on Rh foils and single crystals.

Kinetics of CO Oxidation by O 2 or NO on Rh( 11 1) and Rh( 100) Single Crystals

BERLOWITZ, G. B. FISHER and s. H. OH, J. Phys. Chem., 1988, 92, (6), 1563-1567 The oxidation of CO by 0, or NO over Rh( I I I ) and R h ( 1 o o ) 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, 0, and NO was measured. The CO-0, 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 sur- faces. Deactivation occurred at a slightly lower 0, partial pressure on Rh(~oo), 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-0, 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, 3. Chem. SOC., Faraday Trans. I , 1988, 84, (2), 4 1 3 - 4 3 1

Five different paramagnetic Rh"species were stabilis- ed following activation by flowing 0, at 2oo-475OC in ion-exchanged RhNa-Y samples prepared either from [Rh(NH,),ClICI, (sample I) or from Rhcl, .3H, 0 (sample 11). The condition of formation of these species, their stability and their possible loca- tions 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 1 o o o - 1 2 5 o o 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.

C. H. F. PEDEN, D. W. GOODMAN, D. S. BLAIR, P. J.

Platinum Metals Rev. , 1988, 32, (3) 149

Thermochemistry of the Intermetallic Compounds RuTi, RuZr, and RuHf L. TOPOR and 0. J . KLEPPA, Meiall. Trans. A, 1988, 19A, (4), 1061-1066 The standard enthalpies of formation of RuTi, RuZr and RuHf have been determined by high tempera- ture mixing calorimetry at 1400K, as - 153.9k7.4,-137.326.8 and -183.5210.4 kJ/mol, respectively. These are the first experimentally measured enthalpies of formation for these in- termetallics 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

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 P ~ A u , ( P P ~ , ) ~ ( N O , ) , was formed by the reaction of H, with Au(PPh,)NO, and either Pt(PPh j ) , or Pt(COD)(NO ,) ,. 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(0) Complex, (C H,)Pt(PPh3)2

RAY and D. SCHOMBURG, Polyhedron, 1988, 7, (7), 505-512 The oxidation-reduction reaction between a zwit- terionic diphos horus compound, involving the grouping Cl-@-eP( +)-NEt with the Pt(o) complex, (C,H,)Pt(PPh,), , produced a novel Pt(I1) 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.

Na2PdH,, A Hydride with a Novel Linear [PdH 1 Complex

PtAu 8 (PPh3) 8 (NO 3 ) 2

P. LOOK, R. SCHMUTZLER, R. GOODFELLOW, M. MUR-

D. NOREUS, K. W. TbRNROOS, A. BbRJE, T. SZABO, W. BRONGER, H. SPITTANK, G. AUFFERMANN and P. MOLLER, J. Less-Common Met., 1988, 139, (2), 233-239 The ternary hydride Na,PdH, was prepared by the reaction of Na hydride with Pd in a hydrogen at- mospere at 37oOC. The structure was derived from X-ray studies on powdered samples and on a single crystal as well as from neutron diffraction ex- periments on the deuterated compound. Na,PdH, crystallised in the tetragonal space group I4/mmm and was isotypic with Na,HgO,. The atomic ar- rangement was a novel linear [PdH,l 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.,

The cation [Ir(CO) ,(PEt ,)] 1 + reacted smoothly with XeF, at 273K in CH,CI, to give the novel species [Ir(CO),F(COF)(PEt,),l+ (I) in high yields. The product (I) is the first fluoroacyl complex described and is stable at room temperature in the absence of air and moisture. It was isolated as BF,- and PF,- salts and was characterised spectroscopically, crystallographically and by partial elemental analysis. The product (I) has considerable potential as a syn- thetic intermediate.

Surface-Mediated Organometallic Syn- thesis: Formation of [Os, C(C0) I - from [OS~(CO),~] on MgO

GATES, 3. Chem. soc., Chem. Commun., 1988, ( 5 ) , 371-372 A simple one-step high yield synthesis of [Os,C(CO),,lz- from [Os,(CO),,l conversion on the surface of partially dehydroxylated MgO under I bar of flowing CO at 550 K is reported. This syn- thesis is far simpler and gives much higher yields of about 65% than the conventional synthesis. Previous- ly 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 [Ru, -xOs,(bpy)31(PF,)2 H. YERSIN, G . HENSLER and E. GALLHUBER, 9. Lumin., 1988, (40 i? 411, 676-677 The emission properties of the title compound were studied at T=2K and high magnetic fields. The radiationless energy transfer from the [Rul-host to the IOsl-guest was governed by a fast process and a slow one, which showed a relatively ineffective transfer in the host material.

19889 (8), 529-530

A. S. FUNG, P. A. TOOLEY, M. J . KELLEY and B. C.

ELECTROCHEMISTRY Effect of Tin Adatoms on the Electro- oxidation of Ethylene Glycol on a Platinum Electrode 0. 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.

Platinum Metals Rev. , 1988, 32, ( 3 ) 150

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, S~I -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 10’ 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 HCOOCH, in an amount almost equal to CO, . 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

RICHOUX and J. M. THOMAS, 3. Phys. Chem., 1 9 8 8 , 9 2 , ( 5 ) , 1286-1290

Cyclic voltammetry was used to evaluate redox poten- tials, diffusion coefficients and heterogeneous elec- trochemical rate constants for reducing radicals derived from various N-methylbipyridinium ions, N- methylpyridinium ions, aryl ketones and p- nitrobenzoate ion in aqueous solution. The absorp- tion 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.

A. HARRIMAN, G. R. MILLWARD, P. NETA, M. C.

Permeation of Gases through Po- ly(Ethy1ene Terephthalate) Membranes Metallized with Palladium

URSU, 3. Membrane Sci., 1988, 35, (3), 2 9 1 - 3 0 0

Studies were made of the permeations of He, H,, CO,, Ar and N, at 5o°C through poly(ethy1ene terephthalate) (PET) membranes metallised with Pd layers of I z S - I o o o h 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 Elec- trochemical Characterization of Au-Pd System in 1 M H 2 S 0 ,

SurJCoat. Technol., 1988 , 34, (z), 1 4 1 - 1 4 4

An electrochemical study of the Au-Pd system was performed by measuring the 0 electrosorption pro- perties of Pd surfaces coated with Au by vacuum deposition, in I M H,SO, at 25OC. The properties differed from those of Pd-Au alloy. The crater edge profiles showed an interface a few hgstroms thick of a Pd enriched layer, very close to the surface. Bet- ween this interface and the bulk of the electrode, Au was predominant, but with a great amount of Pd for- ming a mixture with the Au.

Electrochemical Studies of Hydrogen in Ordered and Disordered Pd,Mn Alloy K. BABA, Y. SAKAMOTO and T. B. FLANAGAN, 3. Chem. SOC., Faraday Trans. I , 1988, 84, (z), 459-466 The solubility of H in ordered and disordered forms of Pd,Mn was studied by electrode potential and electrical resistance measurements following elec- trochemical 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

P. MERCEA, L. MURESAN, V. MECEA, D. SILIPAS and I.

1. GENESCd, M. E. GAMBOA and L. COTA-ARAIZA,

Methanol Oxidation on Unsupported and Carbon Supported Pt + Ru Anodes

form was about a factor of four greater than that for the ordered form at 312K.

J. B. COODENOUGH, A. HAMNETT, B. 1. KENNEDY, R. MANOHARAN and s. A. WEEKS, 3. Electroanal. Chem. Interfacial Electrochem., 1988, 240, (I/z), 133-145 A novel Pt+Ru electrode material was shown to be highly active for the direct electro-oxidation of methanol in H, SO, 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-oxida- tion anode, the concentration of oxidised Pt was somewhat increased and there was no evidence for any Pt-CO or Pt, =CO species; rather adsorbed for- mate 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 IoomV.

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

and v. M. GRYAZNOV, Im, Akad. Nauk SSSR, Ser. Khim., 1988, (4), 750-755 Studies of catalytic activity and H, permeability in 9.8OhRu-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 mem- brane catalyst determined by nature of reagants. Oxidative-reductive treatment changed in much smaller degree the surface structure, catalytic activity and H , permeability than alternative treatment.

M. M. ERMILOVA, N. V. OREKHOVA, E. V. SKAKUNOVA

Platinum Metals Rev., 1988, 32, (3) 151

The Kinetics of Charging and Discharg- ing of Iridium Oxide Films in Aqueous and Non-Aqueous Media P. G . PICKUP and v. I . B I R S S , ~ . Elecrroanal. Chem. In- terfacial. Electrochem., 1988, 240, ( ~ h ) , 185-199 The kinetics of oxidation and reduction of elec- trochemically generated Ir oxide fdms in H,SO,, basic aqueous LiCIO, solutions and LiCIO, + 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 LiClO, + CH, CN solution.

Characterisation of Oxygen Evolving DSA Type Electrode. 1. TilIrO -Ta 0 Electrode

HINDEN, Electrochim. Acta, 1988, 33, (4), 573-580 Morphological and crystal structure studies of 0, evolving DSA electrodes Ti/IrO,-Ta,O, showed ag- glomerates of epitaxial crystals of IrO, in the deposits. The catalytic activity and efficiency of the electrodes were a maximum for a composition con- taining 7o%IrO, and 3o%Ta,O,. An increase in catalytic activity and efficiency was due to Ta,O, ad- dition to the deposit, which resulted in an increase in the number of electrochemically active sites formed.

Electrochemical Reduction of Carbon Dioxide. Characterization of the Forma- tion of Methane at Ru Electrodes in Car- bon Dioxide Saturated Aqueous Solution

R. ROLEWICZ, CH. COMNINELLIS, E. PLATINER and J .

D. P . SUMMERS and K. W. FRESE, Langmuir, 1988, 4, (I), 51-57 The electrochemical reduction of CO, to CH, 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 CH, formation rate with pH showed that the rate in- crease with decreasing pH was due to an increasing H coverage on the electrode, until the coverage became so high that sites for CH, formation were blocked.

Formation of Bromates at a RuO /Ti0 Titanium Anode 0. f. PAVLOVIC, N. v. KRSTAJIC and M. D. SPASOJEVIC, Surf. Coat. Technol., 1988, 34, (2), 177-179 The production of Na bromate by electrolysis of con- centrated Na bromide solution in a cell without a diaphragm using a RuO,/TiO, Ti anode was studied. The RuO,/TiO, active coating for the Ti anode was obtained by thermal decomposition of a salt mixture of RuCl, .3H,O and TiCI, in isopropanol. The cur- rent efficiency was high at 98-99Oh when the pH of the solution was maintained at 8.5-9.5 in the presence of Na , Cr , 0 , .

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

Int. J . Hydrogen Energy, 1988, 13, (4), 225-230 An equation for the cell current in a self-driven photon-induced electrochemical cell, with semicon- ducting photoelectrodes as the electrodes, has been derived and applied to H 0 splitting to H, . The cell current and cell potential depend on semiconductor properties and the properties of ions in solution. Computed results show the same trends as ex- periments. Calculations suggest that an efficiency in the conversion of light up to 18% for H , 0 splitting to H, may be possible for p-InP(Pt-electrocatalyst)/n- Si(electrocata1yst).

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

J.Phys.Chem., 1988, 92, (8), 2316-2324 The open circuit photovoltage of a photoelec- trochemical 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 5-2onm,wide.

Exciplexee of Ruthenium(I1) a-Diimine Complexes with Silver(1) N. P. AYALA, J . N. DEW and v . A. DEGRAFF, J.Am.Chem.Soc., 1988, 110, ( 5 ) , 1523-1529 Luminescence “quenching” of RuL,?+, where L=s,i’-bipyridine and 4,7-dimethyI-1,1o-phena- nthroline, photosensitisers by Ag + in aqueous solu- tions proceeds not by oxidative transfer quenching, but predominantly by formation of luminescent ex- ciplexes. The photochemih formation of Ago(aq) is (0.02 in H,O and (0.05 in acetonitrile. Both form a normal bimolecular exciplex, *(RuL, /Ag) )+, and a rare termolecular *(RuL, /Ag,)‘+ exciplex is seen.

Photochemical C 0 2 Reduction by an NADH Model Compound in the Presence of [Ru(bpy) I 2+ and [Ru(bpy) (CO) I 2+

(bpy= 2,2 ’-bipyridine) in H20/DMF H. ISHIDA, K. TANAKA and T. TANAKA, Chem. Lerr.Jpn., 1988, (2), 339-342 Photochemical conversion of CO, to CO and HCOO- was carried out by using nicotinamide adenine dinucleotide model compound, I -benzyl- 1,4-dihydronicotinamide, as an electron donor in the presence of [Ru(bpy)31’+ and [Ru(bpy),(CO),I’+ in H,O/DMF. The quantum yields for the CO and HCOO- formation attained 14.8 and 2.7%, respec- tively, in H,O/DMF (1:9 v/v).

S. U . M. KHAN, R. C. KAINTHLA and J. O’M. BOCKRIS,

Y. NAKATO, K. UEDA, H. YANO and H. TSUBOMURA,

Platinum Metals Rev., 1988, 32, (3) 152

Energy Redistribution and Localization in the Excited States of Ruthenium(I1) Polypyridyl Complexes

and 1. VAN HOUTEN, Inorg. Chem., 1988, 17, (4),

Excited state absorption and resonance Raman spec- tra of the mixed ligand complexes Ru(bpy),phen, +

and Ru(bpy),DIP’ +, 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 ex- cited 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+/TiOz R. M. QUINT and N. GETOFF, Int. 3. Hydrogen Energv, 1988, 13, (5), 269-276 The Ru(bipy) , +/H, SO, /n-TiO, system was in- vestigated to discover its water splitting ability. The effects of initial Ru(bipy) , + concentration, prepara- tion grain size and amount of TiO, powder used in suspension were examined. Conditions during system illumination and the pH of the solution were also ex- amined. At prolonged illumination and/or at higher illumination temperatures, <4ooC, a relatively strong decomposition of the sensitiser is seen. Yields of 0, and H, were determined and possible reaction mechanisms are presented.

C. V. KUMAR, 1. K. BARTON, I. R. GOULD, N. J. TURRO

648-651

ELECTRODEPOSITION AND SURFACE COATINGS Structural and Protective Properties of Rhodium Coatings Obtained by Pro- grammed Pulse Current

KOSTIN, Zushch. 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 gA electrolyte): Rh sulphate ratio of 8-10 (calculated on metal) in go-~oo% H,SO,, pH-I , at 20-25OC using Pt anodes and achieving coatings of thickness of 1-20 pm. The results showed that during cyclic Rh elec- trodeposition by bipolar-impulse current the microhardness of the Rh coatings increased to goooMPa and at the same time internal tension decreased to 2ooMPa. This method also prevented cracking, decreased porosity and increased the rate of Rh coatings deposition. The reliability and durability of electroapparatus contacts were increased.

V. A. ZABLUDOVSKII, V. I. KAPTANOVSKII and N. A.

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

and C. BATTAGLIN, Extended Abstracts, Vol. 88-1, Electrochem. Soc., Spring Meeting, Atlanta, Georgia, May 15-20, 1988, 777-778 Depth profiling of RuO,/TiO, 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 RuCl,.xH,O/TiCI, mixtures or of Ru(NO)(NO,) ,/TiCI,. Various techniques of assess- ment were used.

A. DE BATTISTI, M. CAPPADONIA, G. LODI, R. AMEDELLI

APPARATUS AND TECHNIQUE Nernstian Behaviour of Zirconia Oxygen Sensors Incorporating Composite Elec- trodes s. P. s. BADWAL, F. T. CIACCHI and J. w. HAYLOCK, J.Appl.Electrochem., 1988, 18, (2), 232-239 The Nernstian behaviour of ZrO, 0, sensors incor- porating composite electrodes has been examined in the range < h 0 C . These electrodes consist of a semiconducting metal oxide and Pt and lower the operating temperature of 0, sensors to - 3oo-350°C, which is well below that conventional- ly used. Impedance measurements show that the elec- trode 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 ‘-Te tramethylbenzidine A. WATANABE, K. MORI, M. MIKUNI, Y. NAKAMURA and 0. ITO, J. Chem.Soc., Chem.Commun., 1988, (7), 452-453 A fme Pt wire electrode was used in the electrolysis of 3,3’,5,5’-tetramethylbenzidine (TMB), at 60OC; 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 > I cm in length.

A New Staining Technique of RuO, Solu- tion in Organic Solvents for Resolving the Lamella Structure in Polymers T. CAO, s. CHEN and Y. ]IN, Polymer Commun., 1988,

A solution of RuO, in CCI, was used as a staining medium for resolving the lamella structure in both polyethylene and polypropylene with the transmis- sion electron microscope. Staining in the organic medium was more efficient than in the vapour phase of an aqueous solution of RuO, and was more conve- nient than in the vapour of solid crystalline RuO, for both polymers. The organic solution of RuO, ap- pears to be a universal staining medium for revealing the fine morphology in hydrophobic polymers.

29, (31, 66-67

Platinum Metals Rev. , 1988, 32, (3) 153

HETEROGENEOUS CATALYSIS Another Strong Metal-Support Interac- tion: High Intrinsic Methanation Activity of an Alumina-Supported Platinum Catalyst after High Temperature Reduc- tion without Loss of Chemisorption Ability s. TANIGUCHI, T. MOM, Y. MORI, T. HATTORI and Y. MURAKAMI, 3. Chem. SOC., Chem. Commun., 1988,

Pulse surface reaction rate analysis measurements showed that the intrinsic methanation activity of 0.5%Pt/A120, catalyst was increased by high temperature reduction (HTR) without a marked reduction in its chemisorption ability. The rate cons- tant 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 0, follow- ed 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 methana- tion 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 PlatinumlAlumina Catalysts Modified by Lanthanum and Cerium

( 10) , 630-63 I

V. A. DROZWV, P. G. TSYRUL’NIKOV, A. N. PESTRYAKOV, A. A. DAWDOV and V. V. POPOVSKII, Kinet. Katal., 1988, 29, (2), 484-488 A study of the effect of the addition of La and CX ox- ides to 2.53Wt.0/oPt/~~01 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/y-Al2 0, Catalyst A. A. IVKO and s. v. WKEVICH, Vesm. Akad. Navuk BSSR, Ser. Khim. Navuk, 1988, (I) , 18-21 Mass-spectroscopy studies were performed of the gassing and thermodesorbed products formed during benzene hydrogenation to cyclohexane over o.3%Pt17-Al,01 catalyst, which is the primary reac- tion stage of the industrial production of caprolac- tams. 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 Activi- ty 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 at- mospheric pressure was investigated for Pt/Al ,O ] , Pt-Re/Al,O, and Pt-Re-Cr/Al,O, as a function of their pretreatments. Presulphidation caused very high conversions, high yields of cyclenes, aromatics and H , , and hence enhanced coke formation. With self-poisoning, S stabilises the hydrogenation/ dehydrogenation reactions of the catalysts. Reactiva- tion with CCI, in air increases the total conversions; and the cracking activity increases. For best results, the reaction should be performed after presulphida- tion when the catalysts contain high C1 contents.

Skeletal Catalysts on Supports. 11. For- mation and Structure of Pt-Cu/A12 0 Raney Catalysts

FASMAN, Kinet.Katal., 1988, 29, (I), 180-184 The porous structure of Pt-Cu/Al,O, Raney catalysts was studied by a low-temperature adsorption method and by capillary condensation of Ar. The treatment of the catalyst with 5% HNO, increased specific surface and porosity at the expense of dissolving part of the 7-Al ,O and Cu. The rest of the Cu was redispersed in the pores of the catalyst, stabilising and forming 0- CuAlO, . During the catalyst preparation highly dispersed surfaces were formed. It is suggested that Cu ions fixed in the lattice of 7-Al 0 become centres of stability for migrating Pt atoms.

The Adsorption of Oxygen and the Oxida- tion of Methanol on Silver-Platinum Alloys S. DONG, F. XIAO and J . DENG, J.Catal., 1988, 109, ( I ) , 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 0 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 C , and C, Alcohols by Si0,-Supported RhFe, PtFe, and PdFe Bimetallic Cluster- Derived Catalysts

3. Chem.Soc., Chem.Commun., 1988, (6), 428-430 Evidence for the potential benefits of SO,-supported Rh,Fe, Rh,Fe,, F’tlFel, PtFe,, Pd,Fe, and PdFe, carbonyl clusters as precursors for the preparation of tailored bimetallic catalysts is presented. The derived catalysts exhibit high catalytic activities and selec- tivities for the formation of oxygenates, consisting mainly of methanol and ethanol from CO + H, .

G. M. KHUTORETSKAYA, V. N. ERMOLAEV and A. B.

A. FUKUOKA, T. KIMURA and M. ICHIKAWA,

154 Plarinum Metals Rev., 1988, 32, (3)

The Effect of the Carrier Modification by y-Alumina on Palladium Catalyst Pro- perties 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 o.q%Pd/a-Al, 0 catalyst by y- Al 0, on its proper- ties. The results showed the existence of an optimal concentration of y-Al,OJ at which the maximum dispersity of Pd particles and the highest value of its specific catalytic activity were observed.

Syntheses and Characterization of Mercapto-Hydroxyl-Palladium Macro- molecular Chelates and Their Catalytic Properties Y. WANG and H. LIU, 3. Mol. Catal., 1988, 45, (I),

A Pd complex with an unusual macromolecular mercapto-hydroxyl bidentate ligand was prepared by the reaction of epoxy-phenolic oligomer with H,S and was then characterised spectroscopically. The catalytic behaviour of macromolecular Pd chelate complexes absorbed on a S O , support was studied

127-142

by the Heck reaction. The activity of the chelates The Conversion of Pobaccharides to depended on the molar ratio of S:Pd, and an active Hydrogen Gas. Part 1: The Palladium catalyst was obtained at a S:Pd ratio of 2. The catalyst Catalysed Decomposition of Formic was inactive at ratios of 6 or greater. The catalyst had AcidISodium Formate Solutions better stability than other polymeric Pd catalysts. s. P. HILL and 1. M. WINTERBOTTOM, J . Chem. Tech. Biotechnol., 1988, 41, (2), 121-133 Studies of catalytic decomposition of solutions con- taining formic acid and Na formate to H , + CO , over 5% w/w Pd/charcoal catalyst was studied in a stirred reactor at 60-go°C. The production of H, gas was optimum in the pH range 3.8-6.5 and the order of reaction varied with the solution composition from 0.33(1oomol% formic acid) to 1.07(1oomol% formate ion). Energies of activation were in the range 20.9&5 to 41.8qkJ/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, (I), 106-112 The meta-cresol steam dealkylation on Al , 0 - supported Rh (0.6wt.%), Pd(0.6wt.%) and Ni(r1.4wt.%) catalysts was performed in a dynamic reactor at 4o0C, at atmospheric pressure and weight hourly space velocity of 2 to 20h. 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 propor- tions, 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: Rhroo>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 ap- peared to take place in an acetic acid fdm 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.

Iron or Lanthanum Promoters on the Selectivity of Palladium Zeolites in Methanol Synthesis B. M. CHOUDARY, K. LAZAR, K. MATUSEK, and L. GuczI, J. Chem. Soc., Chem. Commun., 1988, (9), 592-594 The first example showing a distinct shift in selectivi- ty 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 RhlSiO? : A Rapid-Response Fourier Transform In- frared Transient Study Y. -E. LI and R. D. GONZALEZ, 3. Phys. chem., 1988,

The catalytic oxidation of CO was studied over Rh/SiO, by using a FTIR-mass spectrometric techni- que. The reactivity of linearly adsorbed CO was con- siderably greater than that of the dicarbonyl species at both 85 and 2ooOC. The oxidation of CO over Rh/SiO, proceeded through a mixed 0-CO adlayer. Induction times required for the formation of gas- phase CO, were nearly 2 orders of magnitude lower than those observed for Pt/SiO, and Pd/SiO,. Self- sustained CO-0, oscillations reinforced the greater reactivity of linearly adsorbed CO. H,-CO-0, tran- sient 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 Rh, and RhFe Bimetallic Cluster-Derived Catalysts L. -F. RAO, A. NKUOKA and M. ICHIKAWA, 3. Chem. SOC., Chem. Commun., 1988, (7), 458-460 Rh,, Fe, and bimetallic RhFe clusters encapsulated in NaY zeolite were characterised and examined in the CO + H, reaction under atmospheric pressure. The Rh, clusters led to the formation of C,-C, alkenes, whereas the entrapped RhFe clusters had a higher selectivity for C, -C, alcohol formation.

92, (61, 1589-1595

Platinum Metals Rev., 1988, 32, (3) 155

Design of Fischer-Tropsch Catalysts by Pulse Surface Reaction Rate Analysis. 11. Selective Production of Liquid Fuel Frac- tion on RutheniumIAlumina Catalyst Pro- moted by Rare Earth Oxides N. TAKAHASHI, T. MORI, A. MIYAMOTO, T. HATTORI and Y. MURAKAMI, Appl. coral., 1988, 38, ( I ) , 61-69 Different rare earth oxides were tried as promoters of Ru/AI,O 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-Na2 O/Al, 0 Catalysts: Synergistic Effect of Ru and Mo

Y. TAKEGAMI and T. INUI, 3. Mol. catal., 1988, 45, ( I ) , 1 1 1 - 1 2 6

Direct synthesis of alcohols from syngas on Ru-Mo- Na,O/AI,O, catalysts was studied at 25s°C under 86kg/cm1 pressure. The results showed that close contact between Ru and Mo particles was essential for the formation of alcohols. Combining Na,O with the Ru-Mo catalyst decreased the catalytic activity but in- creased the selectivity for alcohols, together with a slight increase in propagation probability for alcohol products.

Wet Oxidation Catalyzed by Ruthenium Supported on Cerium(1V) Oxides

Chem. Res., 1988, 27, (4), 7 1 8 - 7 2 1

The activity of various noble metal catalysts was in- vestigated for the wet oxidation of organic com- pounds, 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(1V) oxide the most effective support. The Ru/Ce catalyst rivall- ed 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 0-containing compounds, such as poly(ethy1ene glycol), ethylene glycol, etc.

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

AIZUMI, Nippon Kagaku Kuishi, 1988, ( I ) , 126-128 The hydrogenation of cyclohexanone was performed under atmospheric or high H, pressure (Iookg/cm,) at 7ooC 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.

M. INOUE, T. MIYAKE, S. YONEZAWA, D. MEDHANAWN,

S. IMAMURA, I . FUKUDA and S. ISHIDA, Ind. Eng.

J.-I. ISHIYAMA, K. ESASHIKA, Y. SENDA and S. IM-

HOMOGENEOUS CATALYSIS Homogeneous Catalysis of the Water-Gas Shift Reaction R. M. LAINE and E. 1. CRAWFORD, J . Mol. Catal., 1 9 8 8 , 44, (3L 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 dur- ing the last 10 years. Topics discussed include transi- tion metal catalysis of the WGSR under both acidic and basic conditions, as well as areas of special in- terest such as mixed-metal catalysis and catalyst tolerance toward S contaminants. ( 9 6 Refs.)

Reversible Homogeneous Catalysis of Carbon Dioxide Hydrogenation/Reduc- tion at Room Temperature and Low Pressures

Chem. Commun., 1988, (9) , 602-603 The Pt complex, IPt,(p-dppm),l, where dppm = Ph,PCH,PPh,, is an effective catalyst under un- precedented mild conditions in toluene solution for the reaction between CO,, H , and Me,NH to yield dimethyl formamide and H, 0. The catalysis is readi- ly reversible, which is unusual.

Allylation of Active Methylene Com- pounds with Ally1 Oxime Carbonates Catalyzed by Pd(0) 0. SUZUKI, Y. HASHIGUCHI, s. INOUE and K . SATO, Chem. Lett. Jpn., 1988, (2), 291-294 Allylation of active methylene compounds catalysed by a Pd(o)-phosphine system using Pd(dba) (dba = dibenzylideneacetone) catalyst and diphenylphosphinoethane was performed with high stereoselectivity by employing ally1 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-SilyI-4-Stannylfuran S. KATSUMURA, S. FUJIWARA and S. ISOE, Tetrahedron Lett., 1988, 29, (IO), 1 1 7 3 - 1 1 7 6

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(o) catalysed coupling with CO and 2-trimethylsilyl-4-tributylstannylfuran followed by chemoselective oxidation of 2-trimethylsilylfuran with singlet 0. This synthesis of these unique sesterterpenoids promises not only to supply enough quantities of these biologically important pen- taprenoids but also to make possible the synthesis of various analogs of manoalide. The seco-manoalide in- hibits both phospholipase A2 and aldose reductase more strongly than manoalide in vitro.

S. SCHREINER, J. Y. YU and L. VASKA, 3. Chem. SOC.,

Platinum Metals Rev. , 1988, 32, (3) 156

Substitute Carbonylation of Organic Compounds Catalysed by Palladium Complexes YU. v. GULEVICH, N. A. BUMACHIN and I. P. BELET- SKAYA, 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 con- verted to CO during reaction catalysed by Pd com- plexes. 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(I1) 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, ( I ) , 103-109 A kinetic study of oxidative acetoxylation of pro- pylene, by O 2 in acetic acid in the presence of PdCI, catalyst and nitrate ions at 50-85OC and various NO,-:Pd(II) and propylene:O, ratios, showed the formation of monoacetate propylene glycols. The reaction of propylene and Pd(I1) 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 o,P-Epoxy Ketones to @-Diketones M. SUZUKI, A. WATANABE and R. NOYORI, Red. Trav. Chim. Pays-Bas, 1988, 107, (3), 230-236 Studies of the isomerisation of cY,&epoxy ketones in the presence of catalytic amounts of tetrakis(triphenylphosphine)Pd(o) and 1,2,- bis(dipheny1phosphino)ethane showed the formation of the corresponding &diketones in high yields. Both open-chain and cyclic substrates could be used. Possi- ble reaction mechanisms were discussed.

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

TANAKA, Chem. Lett. ypn., 1988, (2), 263-264 Olefins and H , were catalytically formed from alkanes in the presence of RhCI(CO)(PMe,), under irradiation by a IOOW high pressure Hg lamp at am- bient temperature for 16.5h. The irradiation was per- formed under N, atmosphere in a closed system. The results showed the,formation of cyclohexene (138 tur- novers) and benzene (3 turnovers). A nearly theoretical amount of H, (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 ac- ceptor and shows high catalytic activity.

T. SAKAKURA, T. SODEYAMA, Y. TOKUNACA and M.

Remarkable Effect of the Wavelength in the Photoassisted Carbonylation of the C- H Bond of Decane in the Presence of RhCI(CO)(PR,), as the Catalyst

M. TANAKA, Chem. Lett. Jpn.,1988, (I), 155-158 Studies of the carbonylation of the C-H bond of decane performed in the presence of RhCI(CO)(PR,), catalyst under irradiation by a 500w high pressure Hg lamp showed the formation of C,, aldehydes andlor I-nonene, depending on the wavelength. Irradiation with X>29gnm was essential to the formation of I-nonene and undecanal. By cut- ting off X<325nm, I-nonene formation was complete- ly suppressed and a series of isomeric C,, aldehydes was obtained.

High Deoxygenation Ability of Rh Car- bony1 Clusters toward Oximes Leading to Nitrile Formation

Jpn., 1988, (2), 285-286 Nitriles were selectively prepared by the reaction of aldoximes with CO and H ? O in the presence of Rh,(CO) ,b cluster catalysts. The i.r. spectra studies of the condensed reaction mixture showed the forma- tion of Rh,, and Rh,, carbonyl cluster anions.

Iridium-Catalysed Hydrosilylation of Hex-1-yne: The Unusual Formation of 1 -Triethylsilylhex- 1 -yne M. J . FERNANDEZ, L. A. ORO and B. R. MANZANO, 3. Mol. Catal, 1988, 45, (I), 7-15 Hex-I-yne reacted with triethylsilane in the presence of IrH, (SiEt,)(COD)(AsPh ,) or Ir catalysts formed by adding triarylarsines (L) or triarylphosphines (L) to [Ir(OMe)(diolefin)ll. The catalytic products were the expected trans- and cis-1-triethylsilylhex-1 -enes, as well as significant amounts of I-triethylsilylhex-I-yne and hex-I-ene. The forma- tion of alkynyltriethylsilanes from alkynes, and alkenyltriethylsilanes from alkenes is a characteristic of the [Ir(OMe)(diolefin)l, + nL systems. Mechanistic pathways for the observed hydrosilyla- tion reaction were discussed.

Selective Hydrogenation of PhCH = CHCOMe to the Unsaturated Alcohol Catalysed by [IrH,(PR,),] (R = Alkyl or

E. FARNETTI, J . KASPAR, R. SPOGLIARICH and M. GRA- ZIANI, 3. 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 I r ratio and on the steric properties of the phosphine. [IrH,(PR,)?l (R = alkyl or aryl) is a catalyst for the hydrogenation of the C = C bond, whereas [IrH,(PR,),l catalyses the reduction of the carbonyl group with a selectivity up to IOO%.

T. SAKAKURA, K. SASAKI, Y. TOKUNAGA, K. WADA and

K. KANEDA, K. DOKEN and T. IMANAKA, Chem. Letf.

Aryl)

Platinum Metals Rev., 1988, 32, (3) 157

Asymmetric Dihydroxylation via Ligand- Accelerated Catalysis

SCHRISDER and K. B. SHARPLESS, 3. Am. Chem. soc., 1988, 1x0, (6), 1968-1970 A new catalytic asymmetric dihydroxylation between olefins and OsO, 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 OsO,-alkaloid complex is formed, which is far more reactive than OsO, alone. The alkaloid acts as an ac- celerator of the dihydroxylation catalysis by binding strongly enough to accelerate addition to olefins.

Ruthenium Carbonyl Catalysed Reduc- tive Carbonylation of Aromatic Nitro Compounds. A Selective Route to Car- bamates

Org. Chem., 1988, 53, (6) , 1243--1250 Ru,(CO),, and Ru(CO),(PPh,), catalysed the reductive carbonylation of nitrobenzene and substituted aromatic mononitro compounds to give the corresponding methylcarbamates, in toluene- methanol, at 160-17ooC and batm, with high selec- tivity in the presence of NEt,+Cl- as co-catalyst. This catalytic system works in relatively mild condi- tions, 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 co- catalyst were studied.

Homogeneous Catalytic Hydrogenation of the Esters of Bicarboxylic Acids. Part 111. Ethylene Glycol from Dimethyl Oxalate

TI, 3. Mol. Catal., 1988, 44, (3h 347-355

E. N. JACOBSEN, I . MARK^, W. S. MUNGALL, C.

S. CENINI, C. CROTTI, M. PIZZOTTI and F. PORTA, 7.

U. MATTEOLI, G. MENCHI, M. BIANCHI and F. PIACEN-

Dimethyl oxalate was hydrogenated in the presence of Ru(C0) , (CHI COO) , (PBu,) to methyl glycolate, which was subsequently reduced at a much slower rate to ethylene glycol. This reduction was affected by high H, 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, 3. MOl. catal . , 1988, 45, (I) , 57-71 The activation and functionalisation of an arene C-H bond was achieved in the photochemical carbonyla- tion of benzene catalysed by the Ru(o) complexes RuU(CO)(NO)(PP~,),(I), Ru(C0) ,(PPh,) , (2 ) and Ru(CO),(PPh,)(3). Under the carbonylation condi- tions, both (I) and (2) converted to Ru(CO),(PPh,).

Oxygen Evolution by Means of Water Ox- idation Catalyzed by Mononuclear Ruthenium-Ammine Complexes M. KANEKO, R . RAMARAJ and A. KIRA, Bull. Chem. SOC. 3Pn., 1988, 61, (4, 417-421 Oxidation of H,O was achieved catalytically by the use of mononuclear Ru-ammine complexes [Ru(NH,),C1I2+ and [Ru(NH,),(H,O)l’+, with Ce(IV) as an oxidant. Cyclic voltammetric studies of the mononuclear Ru-ammine complexes were per- formed using Basal Plane Pyrolytic Graphite (BE) 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 H,O oxidation. The H,O oxidation depended on the ionic strength of the media; higher acidic conditions gave higher 0, 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

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 agglomera- tion. C black was incorporated into the catalyst layer to achieve electrical conduction. Electrodes were fabricated, 0, 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

SRINIVASAN, Extended Abstracts, Vol. 88-1, Elec- trochem. 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, 0, or air should be humidified at IO-ISOC, and H, at IO-IS~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/cmz. Sputtering Pt onto a standard electrode enhanced the power density by IOO-I~OYO; and cells with 20-40 wt.% R/C electrodes had a better perfor- mance than those with 10 wt.% Pt/C. However, sput- tering a Pt film onto 20 wt.% Pt/C gave the highest power densities. A stable performance of x m h oc- curred at 300 and 500 mA/cm’.

A. HONJI, T. MORI, Y. HISHINUMA and K. KURITA, 7.

E. A. TICIANELLI, C. R. DEROUIN, W.-K. PAIK and S.

Platinum Metals Rev. , 1988, 32, (3) 158

Change of Pt Distribution in the Active Components of Phosphoric Acid Fuel Cell 1. ARAGANE, T. MURAHASHI and T. ODAKA, J. Elec- trochem. SOC., 1988, 135, (4), 844-850 The changes in Pt distributions in the active com- ponents, in phosphoric acid fuel cells were in- vestigated after long term use. Electron probe microanalysis shows Pt loss in the cathode and also Pt migration to the anode during operation and iden- tifies Pt in the matrix.

CORROSION PROTECTION Passivating Ability and Corrosion Stabili- ty of Stainless Steel Surface-Alloyed by Palladium by Vacuum Condensation Method

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 sam- ple, were performed in 10 and 20%H2S0, at 25-100°C. The results showed an increase in corro- sion stability by several orders of magnitude in the stainless steel after surface modification by Pd.

G. P. CHERNOVA, T. A. FEDOSEEVA and N. D.

CHEMICAL TECHNOLOGY The Preparation of Chloroplatinic Acid Labelled with Platinum Radioisotopes A. B. MALININ, N. v. KURENKOV, M. D. KOZLOVA and A, s. SEVASTYANOVA, 3, Radwanal. Nucl. Chem.,

After the extraction of ‘“Au 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 Precur- sors for the Chemical Vapor Deposition of High-Purity Palladium and Platinum Thin Films

GIROLAMI, J. Am. Chem. SOC., 1988, 1x0, (8), 2688-2689 The synthesis of high-quality Pd and Pt thin films by metal-organic chemical vapour deposition (MOCVD), from ‘‘tailored’’ organometallic precur- sors 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 250OC and Io-‘torr, and bright silvery metallic films up to 21m thick were grown on a variety of substrates. Electrical conduc- tivity measurements were performed.

Lett . , 1988, 126, (I), 17-25

J. E. GOZUM, D. M. F’OLLINA, 1. A. JENSEN and G. S.

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, XI, (I), 116-123 New wrought self-lubricating Ag-Pd alloy base com- posite 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 10ohi existed on the contact boundary surface for the Io%Pd-5%C-Ag brush and the Cu-Io0hAg 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

IEEE Trans. Components, Hybnds., Manuf. Technol., 1988, XI, (I), 163-170 New glass-ceramic materials, with low dielectric con- stant, which could be sintered at about w 0 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. SIROT- TI, 3. Appl. Phys., 1988, 63, (7), 2267-2271 Thick-film resistive inks were prepared starting from powders obtained by precipitation of RucI, on two different lead-containing glasses. The structural and electrical properties of the films were studied after heat treatment at various temperatures. The evolu- tion of the microstructure involved phase transforma- tions from Pb-rich (Ru-deficient) pyrochlores to RU pyrochlores and f d l y to RuO, .

Y. SHIMADA, Y. YAMASHITA and H. TAKAMIZAWA,

TEMPERATURE MEASUREMENT Forehearth Temperature Gradient Measurements with Thermocouples D. A. TOENSHOFF and C. J. STEER, Glass, 1988,65, (4), 135-1369 I39 The effective use of thermocouples in the glass con- tainer industry is briefly reviewed. The problem of the short life of thermocouples immersed in amber glass has been investigated, and a solution found. In- tergranular fracture of Pt-~oYoRh 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 R-Au alloy or Pt strengthened by the dispersion of an oxide avoids premature failures from Rh.

Platinum Metals Rev., 1988, 32, (3) 159