ABSTRACTS: July 1988148-159

(1)

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 irradiation 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 containing one-quarter monolayer of adsorbed 0 atoms. Methanol was oxidised on the 0-dosed Pd( I I I) surface 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 decomposition 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 1 1 ) 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 electroplated 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, 6 5 , (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 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 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 atmospheric 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.

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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 lattice 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 produced 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 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, (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 compounds.

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 observed on Rh foils and single crystals.

Kinetics

of

CO Oxidation by O 2

or

NO on

Rh( 1 1 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 surfaces. 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.

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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 temperature 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), 5 0 5 - 5 1 2

The oxidation-reduction reaction between a zwitterionic 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 experiments 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

[ O s ,

C(C0)

I

-

from [ O S ~ ( C O ) , ~ ]

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 synthesis 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 = 2 K 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.

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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 - 5 2 6

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 ) , 1 2 8 6 - 1 2 9 0

Cyclic voltammetry was used to evaluate redox poten- tials, 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.

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,, A r 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., 1 9 8 8 , 34, (z), 1 4 1 - 1 4 4 An electrochemical study of the Au-Pd system was performed by measuring the 0 electrosorption properties 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 forming 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 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 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-oxidation anode, the concentration of oxidised Pt was somewhat increased and there was no evidence for any Pt-CO or Pt, =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 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 membrane 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

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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 electrochemically 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 containing 7o%IrO, and 3o%Ta,O,. An increase in catalytic activity and efficiency was due to Ta,O, 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 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 increase 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 current 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 semiconducting 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 experiments. 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 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 5-2onm,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%, respectively, 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,

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Energy Redistribution and Localization in

the Excited States of Ruthenium(I1)

Polypyridyl Complexes

and 1. VAN HOUTEN, Inorg. Chem., 1988, 1 7 , (4),

Excited state absorption and resonance Raman spectra 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 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+/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 investigated 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 examined. 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,, p H - I , at 20-25OC using

Pt

anodes and achieving coatings of thickness of 1-20 pm. The results showed that during cyclic Rh electrodeposition 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 incorporating 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 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

‘-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

(7)

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 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 0, 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 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

oxides 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 reaction 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 atmospheric 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 presulphidation 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

X P S

and TD S 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

(8)

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 U S S R , 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 properties. 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 containing 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 appeared 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 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 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 technique. 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, transient studies also suggest the formation of mixed H- CO adlayers.

Selective Formation

o f

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

(9)

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 increased 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 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(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 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 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.,

(10)

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 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(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 propylene, 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 performed under N, atmosphere in a closed system. The results showed the,formation of cyclohexene (138 turnovers) 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 formation 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 formation of alkynyltriethylsilanes from alkynes, and alkenyltriethylsilanes from alkenes is a characteristic of the [Ir(OMe)(diolefin)l,

+

n L systems. Mechanistic pathways for the observed hydrosilylation 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. [I r H , ( 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)

(11)

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 selectivity in the presence of NEt,+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 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 carbonylation 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 conditions, 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 performed using Basal Plane Pyrolytic Graphite

( B E )

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 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 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.