ABSTRACTS: April 1993108-118

(1)

ABSTRACTS

of

current literature on the platinum metals and their alloys

PROPERTIES

The Transitions (5d”+5d76s)-5d’6p of Pt

III

A. N. RYABTSEV, J.-I;. WYART, Y. N . JOSHI, A. J. J. RAASSEN and P. H. M. UYLINGS, PhyS. scr., 1993, 47, 45-58 The sliding spark and triggered spark spectra of Pt have been observed in the range 559-2020

A.

More than 800 lines have been classified as transitions between 40 levels of 5da+ 5d76s and 93 levels of 5d76p

in doubly ionised Pt, with the support of accurate predictions using energy parameter regularities in the isoelecwnic sequence Ir III-Bi VIII, and by transition probability calculations which include explicitly the configuration mixing in the (5d

+

6s)’ and 5d76p

+

5d ‘ 6 ~ 6 ~ .

The Magneto-Optical Kerr Effect of

Multilayers FeRt and

Copt

s. ZHOU, H. ZHAI, J. SONG and H. ZHANG,

p

Appl. Phys.,

The magneto-optical polar Kerr rotation spectra of multilayers F e P t and C o P t were calculated based on two assumptions; the spin polarisation of the Pt layer was assumed to be negligible, and the Pt layer was assumed to be polarised and to contribute directly to Kerr rotation in the multilayers. The calculated results for Fe/Pt and C o p t multilayers dco(pc)/dR = 1

showed the magnetooptical Kerr rotation at 300-800

nm increased with increasing modulation wavelength.

1993,73, (2), 986-988

Atomic In-Plane Disorder in CoRt

Superlattices

x.

YAN, T. EGAMI, E. E. MARINERO, R F. c. FARROW and c.

Studies of 4 1 1 > and Cool> oriented Co(3A))Ipt(l8A)

superlattices grown by molecular beam epitaxy via X-ray diffraction were made using synchrotron radi- ation. For the < 1 1 1 > oriented sample, the broaden- ing was characterised by a Lorenuian peak shape with a positional correlation length of the order of 50

A.

H . LEE, A@I. Phys. A, 1992, A55, ( 6 ) , 545-548

Thermodynamic Investigation of the Pt-Pb

Binary Alloys

A. AMZIL and R. CASTANET, Ber. Bunsenges. Phys.

The enthalpy of formation of the Pt-Pb alloys was measured at 923-1316 K with respect to composition by direct reaction calorimetry with the help of high temperature Calvet-type calorimeters. The thermodynamic behaviour of the melts was characterised by moderate negative deviations to ideality, suggest- ing some chemical short-range order at 923 K. The associates are very sensitive to temperature since the excess heat capacity is positive with a maximum of- 10.2 J/K.mol near mole fkaction x,

=

0.71.

C h . ,

1992,96, (12), 1872-1876

Effect of Temperature Gradient

on

Concentration Profile of Hydrogen in

a

Palladium Lattice

w. M. LEE and H. s. UHM,J Appl. phys., 1993,73, (3),

The imposition of a linear temperature increase upon a one-dimensional Pd hydride rod caused a significant redistribution in H concentration. The induced concentration gradient was opposite to that of the imposed temperature gradient due to the positive heat of transport. A Pd hydride rod, in which the Q and l3 phase co-existed prior to imposition of the thermal gradient will have a discontinuous H distribution.

Changes in Film Structure and Increase in

Coercivity for CoRd Multilayered Films with

Atmospheric Annealing

H. YAMANE, Y. MAENO and M. KOBAYASHI, J. Appl.

Phys., 1993, 73, ( l ) , 3 3 4 3 3 8

Studies of changes in the film structure of Co/Pd multilayered sputtered films before and after atmospheric annealing showed that coercivity greatly increased to 2 kOe with atmospheric annealing at

300°C. However, this increase was only observed in atmospheric annealing but not in vacuum-annealing.

The Pd Polarization

at

the Pd/Fe Interface

and H. D R E Y S S E , ~ Map. &Map. Marer., 1993,118,

Studies of the electronic and magnetic properties for a film of n adlayers of Pd grown on semi-infinite

Fe(OOl), for Fe,/Pd./Fe, sandwiches and (Fe,/Pd.), superlattices were performed by a mean-field para- meterised tight-binding method. Antiparallel coup1 ing of the Pd layers was observed in PdJFe(001). Ferromagnetic polarisation of the Pd. layers were obtained up to n = 3. For n

=

4, ferromagnetic polarisation of the nearest neighbour Pd overlayer was obtained, but negative polarisation was observed for the three other planes.

Strain Gradient-Induced Diffusion of

Hydrogen

in

Palladium and Nickel

Membranes

Y. SAKAMOTO, H. TANAKA, F. A. LEWIS and

x.

Q. TONG, In?. J. Hydrogen Energy, 1993, 17, (12), 965-970

Studies of the “uphill” diffusion of H during permeation through flat sheets of Pd and Ni were made by an electrochemical permeation method at 303 K. For both annealed and “as cold rolled” Pd samples, uphill diffusion effects on H absorption and desorption were observed over a range of initial H contents from

-

H:Pd = 0.01, which is near or slightly less than the a- composition, up to H:Pd = 0 . 2 5 4 . 3 .

1011-1017

H. NAlT-IAZIZ, S. BOUARAB, C. DEMANGEAT,A. MOKRANI

(3), 365-372

(2)

Magnetic Phase Diagram of N u u , S i , i n

High

Magnetic

Field

V. IVANOV, L VINOKLJROVA, A. S Z Y T U I A and A. 7XGMUNT,

3:

A&YS Cmpd., 1993,191, (l), 159-163

The high field magnetisation and AC susceptibility of NdRh,Jh,Si, compounds were studied up to 140

kOe and the magnetic phase diagram was obtained as a function of concentration, x, and magnetic field. Increases in Y and in magnetic field caused changes in

the magnetic properties of the NdRh,&u~i, compounds. A difference between values determined by neutron dfiaction and magnetic measurements w a s

observed.

Magnetism and Growth of Ultrathin GI Films

Grown

Epitaxially

on

Ru(OOO1)

c. LIU and s. D. BADER,

J.

Magn. 6 Magn. Muter.,

Ultrathin Co films were found to grow pseudomor- phicaUy on Ru(OOO1) at mom temperature in an island suucture, by evaporation h m a resistively heated Co wire in UHV. The expanded Co lattice relaxed to its bulk spacing after a 500°C anneal. No ferromagnetic hysteresis loops were detected in the first four Co monolayer equivalents (MLE), possibly due to super- paramagnetic effects, but ferromagnetic hysteresis loops with in-plane easy axes of magnetisation occurred for film thicknesses > 4 MLE.

1993, 119, (1&2), 81-86

Symmetry of the Gap

in

Superconducting

URu,Si,

K. HASSEIBACH, J. R. KIRTLEY and J. FLOUQVET, Phys. Rev. B, 1993,47, (l), 509-513

Synthesis and Structural Characterization of

a

Layer-Segregated Platinum-Ruthenium

Cluster Complex that Exhibits Selective

Coordination and a High Activity

for

the

Catalytic Hydrogenation of Diphenylacetylene

R. D. ADAMS, Z. LI, P. SWEPSTON, W. WU and J. YAMAMOTO, 3 Am. Chem. Soc., 1992, 114, (26), 10657-10658

The complex Pt,RuJCO),,(CI-H),(p3-H) w a s obtained in 83% yield &om the reaction of Ru,Pb(CO),, with H (1 a m ) in a refluxing heptane solution. The alkyne PhC,Ph was found to exhibit a co-ordination prefer- ence for a tri-Ru site in the monoalkyne derivative and also was highly active in the catalytic hydrogenation of PhC,Ph to (a-stilbene, Ph(H)C=C- O P h . The structure of this Pt-Ru complex consists of

three

mangular layers of nine metal atoms arranged in the form of a face-shared bioctahedron. The cen- tral layer consists of three Pt atoms while the outer layers are pure Ru.

New

Molecular

Superconductor,

H. KOBAYASHI, K. BUN, T. NAITO, R. KATO and A.

A new superconductor [MqEbN [pd(dmit)J, (where dmit is 4,5-dimercapto-l,3-dithiole-2-thione) was isolated with

T,

= 4 K at 2.4 kbar. X-ray studies showed that this superconductor is not isomorphous to neither a-[Me,Et,N][Ni(dmit),], nor to 5-

[(CH,),NI [Pd(dmit),],. Its insulating phase emerged when the superconducting state was suppressed at high pressure.

[Me,E@I

[Pd(dmit),ll

KOBAYASHI, chem. ,?A#. &n., 1992, (lo), 1909-1912

A Novel Chain Compound Composed

of

Benzoflnone

The specific heat in the superconducting state of the

heavy-fermion compound URu,Si, was modelled by

overall agreement between the modelling and exper-

considering all symmeny-allowed gap functions. The

Rhodium(11)

PiValate

Dimer

and

194-

h e m suggests a gap symmetry of either E. (1,l) or B,,

with one or two lines of zeros, respectively.

M. HANDA, A. TAKATA, T. NAKAO, K. KASUGA, M.

MIKURIYA and T. KOTERA, Chem. Lett. Jpn., 1992, (lo), 2085-2088

A chain complex [Rh,(O,CCMe,),.BQI. (I) (BQ =

1,4&nzoquinone) with the

I&@)

pivalate dimen con-

Preparative and Structural Chemistry of

nected by the bifunctional ligation of the pquinone

Chiral

P,N-Bidentate Complexes

of

through its carbony1 0 or C=C double bond, was pre-

Palladium(II) and Platinum(I1)

pared by the reaction of Rh(I1) pivalate dimer &(O,CCMe,), (IIwith BQ in hexane. X-ray ) crystal

CHEMICAL COMPOUNDS

A. ALBINATI, F. JJANZA, H. BERGER, P. S. PREGOSIN,

stIllctcve sNdies of showed that its suucture

H. RiieGGER and R.

w.

K m Z , _Chem.,_{1993,322 is}

formed by an alternated arrangement of (n) and BQ,

(4), 478486

The valine-derived chiral (L) P,N-bidentate ligand @-CH,C6H,),l'CH,CH(Pri)NHCH,C,H,)

(I), PdCI,(I) (2) and PtCI,(l) (3) complexes, and the deprotonated dimeric compound [Pt(l-H)CI],

(4), as well as the iodo analog of 3, were prepared. The results are discussed with the help of molecular mechanics calculations and solid-state "P-NMR methods which are shown to be useful for deter- mining 3-D structures of metal complexes in solution. The complexes exhibited different solution vs solid-state structures. The chiral pocket offered by the chelating ligand is likely to be rather flexible.

Magnetic Ordering in the New Ternary

Stannide UsRh,Snls

GRAVEREAU and J. ETOURNEAU,

3

Magn. & M a p . Muter, 1993,118, (1 & 2), 187-192

Studies of structural and magnetic properties of U,Rh,Sn,,, which melts non-congruently, showed that it crystallises in the cubic Yb,Rh,Sn,,-type structure with a = 9.6416

A

and it undergoes a magnetic tran-

sition near 17.5 K. At low temperature, U,Rh,Sn,, had an enhanced electronic specific heat coefficient. F. MIRAMBET, B. CHEVALIER, L FOURNES, M. J. BESNUS, P.

(3)

Building

Blocks

for

Polymetallic

Ruthenium(lI) and

Osmium(n)

Polypyridine

Luminophores

s.

K. SAHNI, M. G. B. DREW, T. w . BELL and B. s. BRUNSCHWIG,J. Chem. soc., Chem. Commun., 1993, (2), 123-125

X-ray crystallographic studies were performed on the three mixed ligand complexes of Ru and Os, prepared by refluxing aqueous ethanol solutions of cis- [Ru(bpy),Cl,] or cis-[Os(bpy),Cl,] and an excess of the tridentate ligand for 6-28 h under N,, and then precipitated as hexafluorophosphate salts. The complexes, of typical formula [Ru(bpY),bpW [PF61p

PPY

=

2,2’-bipyridine; bpaH = bis@icolyl)amine], have a “dangling” pyridine ligand and a luminescence life- time comparable with that of [Ru(bpy),]”.

Stabilizing

of

the RU:

Core. Use

of

Highly

Charged Ligands such

as

Sulfate and

Phosphate

F. A. COTTON, T. DA-ITA, L. LABELLA and M. SHANG, Inorg. Chim. Acta, 1993, 203, (l), 55-60

The new Ru~(I1,III) phosphate complex,

K.,[Ru,(HPO,),(PO,)(H,O),]

(l), has been prepared by a new synthetic route starting from an Ru,(II,III) carbonate complex to Ru,(II,III) sulphate and phosphate complexes, which were further transformed by electrochemical oxidation to the corresponding Ru2(III,III) complexes. Magnetic susceptibility measurements on &[Ru,(SO,),(H,O)$ at 10-300K confirmed the assignment of the ground state as one arising from an unusual configuration.

ELECTROCHEMISTRY

Oxidation

of

Glucose

at

Electrodeposited

Platinum Electrodes

C. P. WLLDE and M. ZHANG,

3

Elecmanal. Chem., 1992, 340, (1 and 2), 241-255

Studies of the oxidation of glucose at low concentra-

tions at electrodeposited Pt electrodes in 0.1 M HClO, were performed using an electrochemical quartz crystal microbalance (EQCM). Adsorbate, which derived from glucose through the removal of features associ- ated with the presence of adsorbed anions in the back- ground electrolyte, occurred in the region of potential which gave adsorbed H.

Reductions of Nitrite and NO

on

Pt Single

Crystal Electrodes

in

Alkaline Solution

s. YE, H. HATTORI and H. KITA, Ber. Bunsenges. Phys. Chem., 1992,96, (12), 1884-1886

The reductions of nimte and NO on Pt single crys-

tal electrodes were studied by a voltammetric method in alkaline solution. The reductions of nitrite and NO were very structure sensitive in alkalme solution and proceeded exclusively in a potential region of 0 . 3 4 5 V (RHE) at pH > 8. Product analysis and the pH dependence showed direct reduction of nitrite and

NO to NH, occurring on Pt(100) in alkaline solution with an efficiency of > 80%.

Impedance Measurements of Platinum

Electrodes

on a

Solid Protonic Conductor

T. A. WHEAT and P. G. KOMOROWSKI, Solid State Ionics,

Impedance measurements were performed on an electrochemical system consisting of a Pt-paste electrode, a protonic conductor, hydronium-NASICON electrolyte, and a NJHJI-I,O gas phase, at room temperature. Dramatic changes in the electrode impedance with H partial pressure were shown. A comparison of the Pt-paste elemode morphology and reactions, with those of Zr0,-based cells is given. A rise in diffusion- controlled effects at low H partial pressure is seen.

Cyclic Voltammetric Investigation

of

the Cu-

Histidine System

at

Platinum Conventional

and

Microelectrodes

s. DANIELE and M. J. PENA, Ekcmchim. Acta, 1993,38,

Cyclic voltammetric studies of the reduction of C u m in solutions containing histidine (L) at Pt electrodes of conventional and microscopic size showed that the behaviour of the Cu-histidine system at the Pt working electrodes depended on the nature of the sup- porting electrolytes. When there was insufficient amount of ligand, LCu(I1) I 2, the voltammetric studies recorded with the macroelectrode displayed splitting or drawn out curves.

Methanol Oxidation

at

Carbon Supported Pt

and Pt-Ru Electrodes: An

on

Line MS Study

Using Technical Electrodes

s.

WASMUS and

w.

VIELSTICH, J. Appl. Electrochem.,

The oxidation of MeOH at highly porous Pt and Pt- Ru C-base electrodes, prepared by reduction of chloroplatinic acid and Ru(II1) chloride with

K

formate in the presence of the C slurry and bonded with PTFE was studied in 0.05 M H,SO, under acid methanol fuel cell conditions, by a combination of cyclic voltammetry and on line MS, which was found to be a very suitable method, especially for C”-labelled MeOH. Pt(5% on Norit BRX) and Pt-Ru (40/60; 30% on Norit BRX) were used as the C-supported catalysts. Pt-Ru showed the best performance.

The

Mechanism of

Electrocatalytic

Hydrogenation of Organic Molecules at

Palladium Black Cathodes

S. J. C. CLEGHORN and D. PLETCHER, Elecrrochim. Acta, 1993, 38, (2/3), 425-430

The range of hydrogenation reactions possible at a Pd black cathode, prepared by electrodeposition onto graphite in an acid chloride bath, was assessed by voltammetry at rotating and stationary disc electrodes. Studies of the mechanism for the electrocatalytic hydrogenation of organic molecules at this cathode in MeOWethanoic acid showed that a Pd(H) species is the key intermediate and its electrogenated form causes reduction of the organic molecules. S. F. CHEHAB, J. D. CANADAY, A. K. KURUKOSE, A. AHMAD,

1993, 59, (l), 125-132

(2/3), 165-174

1993, 23, (2), 120-124

(4)

Mechanism of Deuterium Cracking in

Palladium

D. SUN, Y. LEI, Y. CHEN, J.

wu

and Q. WANG, Acta MetaZl. Sin., 1992,28, (lo), 456-460

Optical and transmission electron microscopy studies of D, cracking in Pd after 290 h electrochemical- ly D charging showed an increase in the density of dislocations in well-annealed Pd from 10*/cm2 to above

1 O'z/cmz, and a large amount of bubble-like structure or cracks. XRD data showed that the lattice constant of Pd increased fiom 0.3890 to 0.4034 nm. The mechanism of D cracking was considered to be the formation of D, which resulted from the segregation and recombination of D atoms around dislocations.

Electrochemistry of Colloidal Palladium. An

Experimental Study

of

Sol Formation and

Electrocatal ysis

A.M.T.VONDERPWI-I-EN,

].-w.

G. D E B A K K E R ~ ~ L. G. J.

FOKKINK,

3

Electrochem. soc., 1992, 139, (12),

Small colloidal Pd particles were formed in aqueous solution by electroless reduction of PdC&-- species by hydrophosphorus acid, both in the presence and absence of polymer. The presence of H,O-soluble polymers, such as polyvinylalcohol (PVA) and polyvinylpyrrolidone improved the colloid-chemical stability against flocculation and stabilised the particle size of the sols. PVA-stabilised Pd sols were highly cat- alytical for electroless Ni deposition, in contrast to conventional SnPd colloids.

Direct Electrosyntbesis of Halo and Mixed-

Halo Complexes of Palladium(II and

IV)

by

the Dissolution of

a

Sacrificial Palladium

Anode in Aqueous Medium

M.

c.

CHAKRAVORTI and G. v. B. SUBRAHMANYAM, Polyhedron, 1992, 11, (24), 3191-3195

Chloro and bromo complexes of Pd(I1 and

IV),

such as M,[PdX,] and M,[PdXJ (M = Rb, Cs,

NH,

and (CH,),N;

X

= C1 or Br), were elecwsynthesised rapid- ly in a single-step method by the dissolution of a Pd foil anode in chloride or bromide containing media. Electrolysis of dilute HX solution in the presence of pyridine, 2,2'-bipyridyl or 1,lO-phenanthroline yielded non-electrolytes, such as trans-[PdX,(py)J.

Electrode Kinetics of Oxygen Reduction at

Carbon-Supported and Unsupported Platinum

MicrocrystallitelNafionR

Interface

A. PARTHASARATHY,

s.

SRINIVASAN, A. J. APPLEBY and C. R. MARTIN,

3.

Electroanal. Chem., 1992, (1 and 2), 10 1-1 21

Electrode kinetics of 0 reduction at the Pt micro- crystallite/NafionR interface was studied as a function of temperature and pressure, using porous gas-dfi- sion electrodes containing unsupported Pt or WC, in proton exchange membrane fuel cells, and H, and 0,

as reactants. At current densities of 1-1000 &an2 the Tafel slope was -60 mV per decade and was independent of temperature and 0, pressure. 3475-3480

Kinetics and Mechanism of the Substitution

Reaction of

Ethylene Diaminetetra-

acetatoruthenate(II1) with Cyanide in

Aqueous Solutions

M. M. TAQUI KHAN, D. CHATTERJEE, H. C. BAJAJ, K. N . BHATT and s. SANAL KUMAR, Indian

3

Chem., 1992, 31A, (9), 714-715

Studies of the kinetics of the ligand substitution of

Rum (EDTA)/(H,O)- (EDTA

=

ethylenediamine- tetraacetate anion) with CN- were performed spec- trophotomemcally as a function of ligand concentration, pH (5.C11.0) and temperature (20-5OoC). The kinetic and activation parameters were consistent with an associative interchange mechanism. The substitution reaction was studied at four Merent temperatures.

Molecular Structure and Electrochemistry

of

Ru,(dpf),(CdXJI,),

(dpf

=

N,N'-

Diphenylformamidinate

Ion):

A Novel

Ru(III)-Ru(III) Dimer

J. L. BEAR, B. HAN and s. HUANG,

3.

A m . Chem. Soc.,

The synthesis, structural characterisation, and spectroscopic and electrochemical studies were performed on the novel Ru? title complex. The Ru complex (1) was obtained from the reaction of Ru,(dpf),Cl with excess LiC=CC,H, in T H F under

Ar

at room temperature. The red solution was opened to air, and the residue was dissolved in CH,Cl,. The product was purified on a SiO, gel column, and after evaporation of CH,CI, (1) was obtained in

-

30% yield. 1993,115, (3), 1175-1177

Effect of Composition

on

the Point of Zero

Charge of RuO,+TiO, Mixed Oxides

L. A. DE FARIA and

s.

T R A S A ~ ,

3

Electroanal. Chem.,

Studies of RuO,+TiO, mixed oxides prepared by thermal decomposition of RuCl,+TiCl, at 450°C were carried out. The point of zero charge (pzc) was measured by potentiomemc titration of oxide suspensions in KNO, solution. The charge-pH curves were transformed into capacitance values which were used at the pzc to estimate in-situ the real surface area and the inner layer capacitance. The rude form of TiO, has a pzc close to that of RuO, which results in a pzc vary- ing very little between 40 and 100% RuO,.

1992,340, (1 and 2), 145-152

PHOTOCONVERSION

A Study of Ultraweak Luminescence in

Evolution of Oxygen

at

Pt Electrodes

z.

WANG,

x.

JIN, s. CAI, Y. LIU and A. FUJISHIMA, Electrochim. Acta, 1993, 38, (2/3), 267-269

Studies of ultraweak photoemission at a Pt electrode in aqueous solutions containing no luminescer were made using a photon counter. Weak photoemission accompanied 0 evolution at the Pt electrode in solutions H,SO, or KOH, and borate or NaHCO, buffer systems. It is suggested that the uluaweak photo-emis- sion comes &om the recombination of singlet 0.

(5)

Generation of Homogeneous Rhodium

Particles b Photoreduction of Rh(II1)

on

TiO, Colloi& Grafted

on

SiO,

A. FERNANDEZ, A. R. G O N Z h Z - E U P E , C. REAL, A.

CABALLERO and G. MUNUERA, Laflgmuir, 1993, 9, (I), 121-125

Spectroscopic studies of photochemical deposition of metallic

Rh

on three TiOJSiO, samples, containing 3,6 and 12 wt.% TiO,, prepared by the reaction of OH groups and H,O on the SiO, surface with Ti(OCH(CH,),), showed the formation of

Rh-

TiOJSiO, composite materials. Small metallic particles with very narrow size distributions were formed which depended on the amounts of TiO, grafted on the SiO, and on the initial concentration of Rh.

Visible Light Induced Hydrogen Production

with Cu(II)/Bi,O, and Pt/Bi,O,/RuO, from

Aqueous Methyl Viologen Solution

IAN and M.

v.

c. SASTRI, Int. J. Hydrogen Energy, 1993,

The oxide semiconductor y-Bi,O, was doped individually with Cu(II) ions, or loaded with Pt a n d or RuO, (0.5 at.%) and used as a fine powder for photocatalytic production of H, fiom H,O in the presence of methyl viologen (MV’? as an electron relay. The aqueous slurry of the catalyst was irradiated for 90 min in the presence of MV” resulting in generation of 0.79 and 0.66 ml of

H,

by 4 at.% Cu(II)/Bi,O, and PtlBi,OJRuO,, respectively.

Study of Photoelectrochemical

Cells:

Micellar

Effect

on

the [R~(bpy),]~’-Sensitized

Photoreduction of Dyes by NhEDTA

Transition Met. Chem., 1992, 17, (6), 506-508 Studies on photoelectrochemical cells using [Ru(bpy),l2* as sensitiser in the presence of Na,EDTA reducing agent along with various dyes in various types of anionic, neutral or cationic micellar media were performed in order to find out the ability of the Ru sensitiser to generate photocurrents and photo- voltages. The yield of photocurrent was found to be dependent upon the dye and micellar medium.

P. MARUTHAMUTHU, K. GURUNATHAN, E. SUBRAMAN-

18, (l), 9-13

S . UNGAMURTHY, B. SETHURAM and T. N. RAO,

Photoresponsive Electrode Based

on

the

Reaction between Oxygen and the Excited

Ru(bpy)F Complex Incorporated

in

a

Coated

Nafion Film

and M. KANEKo, Elecrrochim. Acra, 1993, 38, (I),

A photoresponsive electrode was prepared by coating a Nafion film on an InSn oxide

(ITO)

electrode having the Ru(bpy),” complex in the film. A photocurrent was induced at the coated electrode dipped in an aqueous electrolyte in the presence of 0. Viologen molecules present as a solute or as the second film on the top of the Nafion[Ru(bpy);T film increased the induced photocurrent by

-

a factor of 2.

Y. UENO, K. YAMADA, T . YOKOTA, K. IKEDA, N. TAKAMIYA

129-133

Formation of

a

Stabilized Coordinatively

Unsaturated Metal Carbonyl Cluster,

H$u,(CO),,, by Photochemical Reaction of

€I&,(

CO),, Adsorbed

on

the Surface of Silica

S. YAMAMOTO, K. ASAKURA, K. MOCHIDA, A. NITTA and

H. KURODA,

3

Phys. Chem., 1993,97, (3), 656-660 Studies of the photochemistry of H,Ru,(CO),, ( 1 ) adsorbed on the surface of SiO, showed that during irradiation by W-visible light, ( 1 ) lost one CO lig- and, giving selectively co-ordinatively unsaturated H,Ru(CO),, on the SiO, surface. The initial photo- product, H,Ru,,(CO)

,,

interacts weakly with surface hydroxyl groups, which are the only functionality available to act as a stabilising ligand.

ELECTRODEPOSITION

AND

SURFACE COATINGS

Thermal Stability of

a

Platinum Aluminide

Coating

on

Nickel-Based Superalloys

H. M. TAWANCY, N. SRIDHAR, B. S . TAWABINI, N. M. ABBAS and T. N. RHYS-JONES, J. Mater. Sci., 1992, 27, (23), 6463-6474

The thermal stability of a Pt aluminide coating on

the directionally solidified alloy MAR M 002 and its single crystal version alloy, SRR 99, was studied at 800,1000 and 1100°C. The morphology of the coating was characterised. In the as-deposited state the coating was two layers, most Pt was in the outer coating layer, which consisted of a fine dispersion of PM, in a manix of p-(Ni, Pt)AI containing Co and Cr.

Interdiffusion of the Aluminized and

Pt-Aluminized Coatings

on

MAR-M247

Superalloy

K.-L.

m

and c.-M. HWANG, sut$ Coat. Technol., 1992,

The interdiffusion behaviour of Pt-aluminised (1) and aluminised (2) coatings were investigated on MAR-M247 superalloy. A NiAl phase formed for the (2) coating, while the PtA1, phase was identified as well as the NiAl phase for coating (1). It was concluded that Ni diffuses outwards for coating (2) but for coating (1) Pt acts as the diffusion media, which enhances the outwards diffusion of Ni and the inward diffusion of Al to form the two phases.

The Roles of the Ruthenium Concentration

Profile, the Stabilizing Component

and

the

Substrate

on

the Stability of Oxide Coatings

NIKOUC and R. T . ATANASOSKI, p Electroanal. Chem., 1992,339, (1 and 2), 147-165

Electrochemical studies of oxide coatings with variable concentration profiles of RuO, as the active component, were performed on components obtained through a combination of separately applied layers of RuO,, TiO,, IrO,, RuO,”TiO,, and RuO,’IrO, on T i and glassy C substrates. Both the stability of the coatings and their related charge depended strongly on the sequence of layers in the Ru0,-TiO, coating. 56, (l), 81-87

V. M. JOVANOVIC, A. DEKANSKI, P. DESPOTOV, B. Z.

(6)

APPARATUS AND TECHNIQUE

Mediated Micro-Glucose Sensors

Using

2 pm

Platinum Electrodes

SUZUKI, T. TAKEUCHI, E. TAMIYA and I. KARUBE,

Elecnoanalysis, 1992,4, (9), 859-864

Glucose-oxidase (GOD) and glucose-dehydrogenase (GDH) sensors, immobilised in a photocrosslinkable polymer, were fabricated on a cylindrical Pt micro- electrode of 2 pm diameter, and characterised by using 1,4-benzoquinone and ferricyanide as electron mediators, respectively. For the GOD micro-glucose sensor, a calibration plot was obtained that was linear up to

-

40 mM glucose, which is superior to values obtained with a disk electrode of 1 mm diameter.

"rimethylamine-Sensing Mechanism of Ti0,-

Based

Sensors.

1. Effects

of

Metal Additivea

on

Trimethylamine-Sensing Properties of TiO,

Sensors

Y. TAKAO, Y. IWANAGA, Y. SHIMIZU and M. EGASHIRA,

Sens. Acruawrs B, 1993,10, (3), 229-234

Studies were performed of the effect of Pt, Pd, Rh, Ru,

In or Au additives on the trimethylamine (TMA)-

sensing properties of TiO,. The sensitivity to TMA was enhanced by the addition of 0.5 wt.% Ru, 2.0% In or 0.5 wt.% Au, while the addition of 0.5 wt.% Pt, 1.5 wt.% Pd or 1.5 wt.% Rh lead to a decrease in the sensitivity. Ru acted as a stronger electron donor from TiO, than expected from its work function.

K. YOKOYAMA, K. NAKAJIMA, S . UCHNAMA, S . SUZUKI, M.

HETEROGENEOUS CATALYSIS

The Catalytic Effect of Platinum

on

the

Oxidation of Carbon Fibres

R G. IACOCCA and D. J. DUQUETTE,

3

M m . Sci., 1993,

The effects of Pt on the oxidation behaviour of PAN- based 5C carbon fibres has been investigated at 500, 550 and 600°C in air. Fibres oxidised in Pt holders had a higher activation energy than those oxidised in SO,. The pre-exponential term for fibres oxidised in Pt was six orders of magnitude larger than the fibres oxidised in the SiO, holders. Spheres formed along the longitudinal axis of many fibres and one fibre bifur- cated with a sphere forming on each remaining fibril.

28, (4), 1 11 3-1 11 9

Isomerization of Xylene Isomers

on

a PtRe-

H-Mordenite Catalyst

A. K. A B O U L & ~ , s. M. ABDEGHAMID and F. M. ABDEL HAY, A". C a d . A: Gen., 1993,93, (2), 131-140 Studies of the isomerisation of xylene isomers performed on a 0.35 wt.%Pt-0.35 wt.% Re/H-mordenite catalyst in a pulse catalync microreactor showed the presence of para-xylene as the highest C8 aromatic component of the hydroconversion of any xylene isomer, whereas orrho-xylene was the lowest. Trimethylbenzenes and ethylbenzenes were not detected in the reaction products. The results indicate an

excellent shape-selectivity for paru-xylene production on the PtRe/H-mordenite catalyst.

Catalytic Activity and Characterization of

Pt/SiO, Catalysts Prepared by the Sol-Gel

Method

M. ASOMOZA, T. LOPEZ, A. ZAMALLOA, R GOMEZ and E.

GARCIAFIGUEROA, New J . Chem., 16, 1992, (lo),

Pt/SiO, catalysts were prepared by the sol-gel method by adding [PtCIJ* to tetraethoxysilane, followed by hydrolysis and condensation. The addition of H,PtC&.6HZ0 during the formation of the gel resulted in solids with surface area of up to 1,100 m2/g. The catalysts with a low metal concentration were active for the hydrogenation of alkenes but not for the hydrogenation of aromatics. Deactivation stud- ies showed that sol-gel Pt catalysts were more resistant to poisoning by thiophene than impregnated ones.

High Catalytic Activity of Platinum-ZSM-5

Zeolite below 500 K in Water Vapor

for

Reduction of Nitrogen Monoxide

H. HIRABAYASHI, H. YAHIRO, N. MIZUNO and M. IWAMO- TO, Chem. La. a n . , 1992, (ll), 2235-2236 A pronounced catalytic activity of Pt ion-exchanged ZSM-5 (SiO,/Al,O,

=

23.3) zeolite is reported below 500 K for the selective reduction of NO by ethene even in the presence of 8.6 MI.% of H,O vapour. The most active temperature of Pt-MFI-97 (cation-zeolite structure-degree of exchange) in the absence of H,O vapour was 485 K and the conversion into N, and N,O were 18% and 36%, respectively. The conversion of C,H, at 485

K

on Pt-Mm-97, Fe-MOR-7 1 and Cu-MFI-105 were 100,4 and 1 %, respectively. 959-963

Non-Faradaic Electrochemid M&cation of

Catalytic Activity.

M. The

Case

of Methane

Oxidation

on

Platinum

P. TSIAKARAS and C. G. VAYENAS,

3

catal., 1993, 140, (l), 53-70

The catalytic activity of Pt for CH, oxidation increased reversibly by up to 7000 % by depositing polycrys- talline Pt films on Y,O,-doped ZrO,, and by polaris- ing the Pt-solid electrolyte interface. The catalytic rate is increased by supplying and by removing 0'- to or from the Pt catalyst through the gas-impervi- ous solid electrolyte. The rate of CH, oxidation depended exponentially on catalyst potential and work function, e$, over wide (up to 0.8 eV) e$ ranges.

Reactions

of

Labelled Hexanes

on

Pt-

wo,/A120,

Catalysts

J. M. FARBOTKO, F. GARIN, P. GIRARD and G. M A I R E 3

CataL, 1993, 139, (I), 256-267

Hexane hydrocracking and isomerisation on Pt-

WO,/AI,O, catalysts (Pt:W

=

l:l), prepared by different methods, and studied by isotopic tracer measurements, showed that the systems catalysed the isomerisation with low selectivity. The reaction proceeded via classical cyclic and bondshift mechanisms. No correlation between the relative contribution of the cyclic mechanism and the non-selective hydrogenolysis of the methylcyclopentane was found.

(7)

Highly Selective Pt-Cr/C Alloy Catalysts for

Single-Step

Vapour

Phase Hydrogenation of

Phenol

to

Give Cyclohexanone

s. T. SRINIVAS and P. KANTA R A O , ~ Chem. SOC., Chem. Commun., 1993, (l), 33-34

Studies of the catalytic activity of Pt-Cr/C catalysts during the single-step vapour phase hydrogenation of phenol showed them to be active for the hydrogenation of phenol with total selectivity to give cyclohexanone. Alloying of the 5 wt.%Pt/C with Cr improved the cyclohexanone selectivity from 84 to 100% in the hydrogenation without giving any side products. The H uptake on the alloy catalyst correlated directly with the phenol conversion.

Effects

of Alcoholic Solvents

on

the Formation

of Cyclohexanones in the Hydrogenation of

Phenols over Pd-C Catalysts

M. HIGASHIJIMA and

s.

NISHIMURA, Bull. Chem. SOC.

Studies were performed of the hydrogenation of phenol and isomeric cresols in cyclohexane and t-pentyl alcohol (t-PeOH) as solvents with a commercial P d C and acid-treated P d C (PICIA) catalysts under H pressure at 120'C. In both catalysts, the maximum yields of the cyclohexanone intermediates as well as the hydrogenation rates of the phenols decreased markedly in t-PeOH compared with hydrogenation in cyclohexane.

'JDTz., 1992, 65, (1 l), 2955-2959

The Reactivity of High Oxygen Coverages

on

Pd(ll0)

in

Catalytic CO Oxidation

(1/2), 14-22

The catalytic oxidation of CO on a Pd( 1 10) surface was studied during CO titration and under steady- state conditions at 10-'Torr. The titration studies with the 0-saturated Pd( 1 10) surface showed a change in the reaction mechanism from a uniform reduction of the 0 coverage at high temperatures,= 400

K,

to a hole-eating mechanism at low temperature. High 0

coverages inhibited the rate of CO, production which was atnibuted to a lowering of the CO residence time and to a reduction of the CO sticking coefficient.

Effect of Sulfur

on

the Performance and

on

the Particle Size and Location of Platinum

in

Ptw,

Hexane Aromatization Catalysts

S. LADAS, R IMBML and G. ERTL, SU?$ &., 1993,280,

G. B. McVICKER, J. L. KAO, 1. J. ZIEMIAK, W. E. GATES, J. L.

ROBBINS, M. M. J. B C Y , S. B. RICE, T. H. VANDERSPURT, V. R CROSS and A. K GHOSH,J catd., 1993,139, (I), 48-6 1

When S was introduced to a working PtML hexane aromatisation catalyst in the form of thiophene, it functioned as a very potent poison which reduced the number of Pt sites accessible within the channels of the KL zeolite. However, the intrinsic catalytic activity and selectivity of in-channel Pt sites were not significantly modified by the presence of

S

on the catalyst. Extremely low thiophene feed S concentra- tions at 50-200 wppb accelerated Pt agglomeration.

Phenylawtaldehyde and Carbon Monoxide

as

Effective Additives

for

the Selective

Hydrogenation of Cyclooctadienes

to

Cyclooctene over Palladium Catalysts

M. HIGASHIJIMA, H . s . MAN and s. NISHIMURA, Bull. Chem. SOC. JPn., 1992,65, ( l l ) , 2960-2965 Isomeric 1,5-, 1,4- and 1,3-cyclooctadienes (COD) were hydrogenated with phenylacetaldehyde (FA)- or CO-treated Pd black in tetrahydrofixan at 25°C and atmospheric pressure of H. Catalysts poisoned by PAA greatly promoted isomerisation of 1,5-COD to 1,4-COD, while the rate of hydrogenation of 1,4- and 1,3-COD decreased.

n-Butane Hydrogenolysis

as a

Probe of

Surface Sites in Rhodium

Metal

Particles:

Correlation with Single Crystals

D . KALAKKAD, S. L. ANDERSON, A. D. LOGAN, J. P&A, E. J. BRAUNSCHWEIG,

c.

H. F. PEDEN and A. K. DATYE, J. Fhys. Chem., 1993,97, (7), 1437-1444

The effect of particle sue and pre-oxidation on the hydrogenolysis activity and product selectivity was studied during n-butane hydrogenolysis, on Rh metal catalysts supported on Al,O, and Si,O with the metal particle size varied (from < 1 to 5 > nm) by changing the metal loading from 0.03-7.2 pmol of Rh/mz of support. The ethane selectivity of the highly dispersed Rh was very different from that of the low index single crystal surfaces of Rh. As particle size was increased, the selectivity of the catalysts approached that of Rh(ll1).

Zirconium-Based Intermetallics

as

Heterogeneous Catalysts for the Fischer-

Tropsch Reaction: In. Zr-Co-Ni-Cu and Ru

Catalysts

TERBOTTOM and I . R. HARRIS,

J.

Chem. Technol. Biotechnol., 1992, 5 5 , (4), 375-378

Intermetallic alloys of type Zrs,J4&ssz, where 0 I x

S O , were prepared by

Ar

arc melting. M and N are combinations of Co, Ni, Cu and

Ru.

The alloys were powdered by H decrepitation, after which they were used in this form as catalysts. The H,/CO reaction was performed in a semi-micro-tubular flow reactor. A. F. Y. ALSHAMMARY, 1. T. CAGA, A. Y. TATA, J. M. WIN-

HOMOGENEOUS CATALYSIS

Palladium-Catalyzed Aldol-Type

Condensation by Enol Esters with SnCI,

Y. MASUYAMA, T. SAKAI and Y. KURUSU, Tetrahedron

En01 esters caused aldol-type condensation with aldehydes in the presence of PdCI,(PhCN),.SnCl, catalyst at 50°C in acetonitrile to give (6-a$-unsaturated carbonyl compounds. Cyclic enol ester, such as

u-

angelicalactone, also reacted with aldehydes under the same conditions to produce ysubstituted bacetyl- yburyrolactones and/or 5-substituted 4-acetyl-2(5H)- furanones. yButyrolactones were only obtained with arenecarbaldehydes.

Lett., 1993, 34, (4), 653-656

(8)

Palladium-Catalyzed Carbonylative

Vi

lation

of Arylmercuric Chlorides with Jarbon

Monoxide and Olefins

D.-S. RYU, K.-H. SONG, J.-T. LEE and J.-I. KIM, B d . Korean Chem. SOC., 1992, 13, (4), 345-355

Arylmercuric chlorides reacted with CO and olefins in the presence of PdC1,(PPh3), catalyst, a base and CuCl,, under mild conditions, to give the corre- spondmg aryl vinyl ketones in moderate to good yields.

An increase in CO pressure enhanced the yields of the desired aryl vinyl ketones. The mechanism of this carbonylative vinylation involves o*ansmetallation of the Pd(II) catalyst, CO insertion to give the aroyl Pd(I1) complex, reaction with olefins, and reoxidation of Pd(0) to Pd(I1) with CaC1,.

Catalytic Asymmetric Synthesis of Optically

Active Alcohols via Hydrwilylation

of

Olefins

with

a

Chiral Monophosphine-Palladium

Catalyst

T. HAYASHI and Y. UOZUMI,

Am

ApPr Chem., 1992,64,

The reaction of terminal alkenes with trichlorosilane at 40°C in the presence of 0.1 and 0.01 mol% of Pd catalyst prepared in situ from [PdCl(rr-C,H,)], and

(~-2-(diphenylphosphino)-2'-methoxy- 1,l '-binaph- thy1 proceeded with unusual regioselectivity at up to 94% and with high enantioselectivity to give high yields of 2-(mchlorosilyl)alkanes and a minor amount of 1-(mchlorosily1)alkanes. Oxidation of C-Si bond gave optically active alcohols with enantiomeric puri-

ty ranging between 94% and 97% ee.

The Palladium-Catalyzed Cross-Coupling

Reaction

of

Enol

Acetates

of a-Bromo

Ketones

with

l-Auren

1-

and 'heir Enol Acetates

s. ABE, N. MIYAURA and A. SUZUKI, Bull. Chem. SOC. Jpn., 1992,65, (lo), 2863-2865

Pd-catalysed cross-coupling reaction between alkyl-, aryl- or 1-alkenylboron reagents with enol acetates of a-bromo ketones using Pd(PPhJ, catalyst readi- ly produced stereodefined enol acetates of ketones. Hydroboration of alkene with 9-borabicyclo-

[3.3. llnonane followed by coupling with Q-2-ethoxy- 1-bromoethene gave the enol ether of aldehyde.

Synthesis

of

Phthalides through Palladium-

Catalysed Heteroannulation of Acetylenic

Compounds

N. G. KUNDU and M. PAL, J. Chem. SOC., Chem. Commun., 1993, (l), 86-88

The heteroannulation of acetylenic compounds in the presence of (PPh,),PdCl, and Pd(OAc), catalysts, yielded phthalides [ 1-(3H)isobenzofuran-3-ones] as major products and isocoumarins as minor products. The reactions were carried out by heating a mixture of o-iodobenzoic acid and acetylenic compound in the presence of the Pd catalyst, Cu(1) iodide and a base in dimethylformamide.

(12), 1911-1916

Com ounds; A Faci

1

e

Synt

'

9!-9

esis

Or

of

YZbron

etones

Formation of 2-Imino-1,3-Oxathioles and

2(3H)-Oxazolethione by the Rhodium(I1)

Acetate-Catalyzed Reaction of a-Diazo-

carbonyl Compounds with Isothiocyanates

T. IBATA and H. NAKANO, Bull. Chem. SOC.

m.,

1992,

Studies of Rh,(OAc), catalysed reaction of various a- diazocarbonyl compounds with alkyl, phenyl and ben- zoyl isothiocyanates showed good yields of 2-imino- 1,3-0xathioles and a by-product 2(3H)-ox-azolethione, which was only produced in the reaction of dia- zodimedone with methyl isothiocyanate. The prefer- able formation of thiocarbonyl ylide was explained by heat of formation and frontier molecular orbital calculations.

65, (1 l), 3088-3093

Rhodium( 11)-Catalyzed Cyclization of 2-

Alkynyl 2-Diazo-3-oxobutanoates as

a

Method for Synthesizing Substituted Furans

A. PADWA and F. R. KMDER, J. Org. Chem., 1993, 58,

Studies of a series of 2-alkynyl 2-diazo-3-oxobutanoates treated with a catalytic quantity of Rh(I1) acetate showed the synthesis of furo[3,4-c]furans in good yield. The reaction occurred by addition of a Rh-stabilised carbenoid onto the acetylenic rr-bond to produce a vinyl carbenoid which cyclises onto the adjacent carbonyl group to produce the furan ring.

Electronic and Steric Control

in

Carbon-

Hydrogen

Insertion

Reactions

of

Diazoacetoacetates

Catalyzed

by

Dirhodium(I1)

Carboxylates

and

Car box a mid

es

M. P. DOYLE, L. J. WESTRUM, W. N. E. WOLTHUIS, M. M. SEE,

w.

P. BOONE,

v.

BAGHEM and M. M. PEARSON,J Am. Chem. SOC., 1993, 115, (3), 958-964

Studies of the unique capabilities of Rh(I1) carboxylates and carboxamides in modifyrng regiocontrol in C-H insertion reactions were performed in order to idennfy the electronic and steric factors which control regioselectivity. 2,3,4-Trimethyl-3-pentyl diazoace- toacetate formed y-lactone products from insertion into primary and tertiary C-H bonds in a statistical distribution (61:39) with diRh(I1) tetrakis(peduorobutyrate), but only tertiary C-H insertion was observed with diRh(I1) tetraacetamide.

Highly

Efficient

Re ioselective

Silylcarbon lation of Alkynes dtalyzed by

DirhodiumKI) Perfluorobutyrate

M. P. DOYLE and M. s. SHA", Organometdics, 1993,

12, (l), 11-12

Studies of the activity of R h o peduorobutyrate catalyst during silylcarbonylation of terminal acetylenes showed it to be highly effective, giving high catalyst turnovers, exceptional E:Z isomer ratios and high yield of Psilylacrylaldehydes with substantial stereo- control at atmospheric pressure, and at or below room temperature. The stereochemistry of the major isomer formed is that of cis addition.

(l), 21-28

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Room-Temperature Catalytic H drogenation

of Aromatic Hydrocarbons 6sing

[(1,5-

COD)RhH],

as a

Catalyst Precursor

z.

DUAN and M. J. HAMPDEN-SMITH, Chem. Muter., 1992,4, (6), 1146-1 148

[(1,5-COD)RhHl, (1) (COD = cyclooctadiene) was synthesised by the reaction of [(1,5-COD)RhCI], with LiBEt,H at room temperature in THF under N, conditions, and used as a source of 2-nm-sized Rh

crystallites under mild conditions. Solutions of (1) were very stable in aromatic and aliphatic hydrocar- bon solvents under inert atmosphere in the absence of H, but aromatic H C solvents were unstable in H.

Acetic Anhydride Synthesis from Meth 1

Formate Catalysed by Rhodium-Iodiie

Complexes

B. SEUILLET, Y. CASTANET, A. MORTREUX and F. PETIT, Appl. Cutal. A: Gen., 1993, 93, (2), 219-229

Studies of a “one pot” synthesis of acetic anhydride fkom methyl formate in the presence of a RhI,(CO), showed that it requires a two stage procedure, due to the incompatibility of the activations used to sustain the two consecutive reactions of homologation and carbonylation. In the fist stage, an alkaline iodide, LiI, was used with an accurate M:Rh ratio, to avoid acetic acid production, while in the second stage, an alkyl iodide was required to provide the synthesis of acetic anhydride.

Formation and Reaction of Acyl Substituted

Nitrile Ylide through the &(OAc),-Catalyzed

Reaction of a-Diazocarbonyl Compounds

with Benzonitrile

T. IBATAand K. FUKUSHUIA, Chew. Let?.

m.,

1992, ( l l ) , 2197-2200

The Rh,(OAc), catalysed decomposition of p-chloro- a-diazoacetophenone in benzonitrile in the presence of dimethyl acetylene-dicarboxylate produced 5-@- chlorophenyl)-2-phenyloxazole and dimethyl 2-@-

chlorobenzoyl)-5-phenylpyrrole-3,4-dicarboxylate in 63 and 1 1 % yields, respectively. The reaction gave oxazoles and pyrrole-3,4-dicarboxyylates through the 1,5-cyclisation and 1,3-dipolar cycloaddition of the acyl substituted nitrile ylide intermediates generated by the reaction of ketocarbenoids with benzonitrile.

Rhodium(1p

Trifluoroacetamide;

an

Excellent

atalyst for Carbenoid 0 - H

Insertion Reactions

G . G. cox, J. 1. KULAGOWSKI, c. J. MOODY and E.-R H. B. s~~,S’len, 1992, (12), 975-976

Studies of Rh(II) acetate and trifluoroacetamide catalysts during cyclopropanation of ethyl diazoacetate with alkenes showed very rapid conversion of the diazo compound in the presence of Rh(I1) trifluoroacetamide (1) catalyst when using an intermolecu- lar insertion reaction into the 0 - H bond of 2- propanol. Catalyst (1) was found to be extremely effective for inter- and intra-molecular carbenoid

0 - H insertion reactions.

Diastereoselectivity

in

the Osmium

Tetraoxide

Promoted Dihydroxylation of Chiral ( E ) -

Gotylsilanes: Asymmetric Synthesis of Silyl-

Functionalized plactones

J. S . PANEKand J. ZHANG,J &g. Chem., 1993,58, (2), 294-296

Studies of the catalytic osmylation of enantiomeri- cally enriched (E)-crotylsilanes (2S,3R)-1 and (2R,3R)-2 containing a homoallylic, N-bearing stere- ocentre, using OsO, catalyst, showed good to high levels of diastereoselection generating silyl-functionalised trans-4,5 substituted y-lactones as the major diastereomers. The selectivity exhibited by the silane reagents together with the high degree of functional- isation contained in the derived y-lactones showed them to be intermediates in asymmetric synthesis.

Catalytic Oxidation of Partially and Fully

Fluorinated Olefins with

Osmium

Tetroxide

w.

A. HERRMANN,

s.

J. EDER and w. SCHERER, Angew. Chem. Znt. Ed. Engl., 1992,31, (lo), 1345-1347 The formation of cycloadducts of partially and fully fluorinated olefins and their conversion into fluorinated diols and products of subsequent reactions in the presence of OsO, is reported, which is contrary to a previous assumption that very electron-poor olefins do not react with the OsO,. Fluoroalkenes reacted with OsO, in hexane in the presence of pyridine and N-containing bases at room temperature giving cyclic osmate(VI) esters quickly and quantitatively.

Asymmetric H drogenation of 2-Fluoro-2-

alkenoic AcidYs Catalyzed by Ru-binap

Complexes: A Convenient Accees

to

Optically

Active 2-Fluoroalkanoic Acids

M. SABURI, L. SHAO, T. SAKURAI and Y . UCHIDA, Tetrahedron Lett., 1992,33, (51), 7877-7880 Studies of asymmetric hydrogenation of (2)-2-fluoro- 2-alkenoic acid (1) in the presence of Ru,Cl,(binap),(NEt,) catalyst (binap = (R)- or

(9-

2,2’-bis(dipheny1phosphino)- 1, 1’-binaphthyl) showed a yield of 2-fluoroalkanoic acids with high enantiomeric purities of up to 90% ee. When the ( R ) -

binap catalyst was used, both (2)- and (E)-(l) were smoothly hydrogenated to give (R)-Zfluorohexanoic acid with comparable asymmetric induction.

Reactivity

of

**Cp*Ru’**

with Acyclic

Unsaturated Hydrocarbons: A Novel Catalytic

Carbon-Carbon Bond Activation Reaction

R. CARRENO, B. CHAUDRET, D. LABROUE and

s.

SABO-

ETIENNE, Orgunometallics, 1993, 12, (l), 13-14 The versatile reactivity of the electrophilic fragment Cp*Ru’, which was generated in situ through protonation of [Cp*Ru(OMe)], by CF,SO,H with 1,3,5-hexatriene, toward unsaturated acyclic hydrocarbons is described. A catalytic reaction performed with neohexene produced three different types of products: (a) neohexene oligomers, (b) 2,3-dimethyl- 2-butene and 2,3-dimethyl-l-butene in 92% yield, and (c) CH, together with C,, and C,, hydrocarbons.

(10)

Ruthenium

Catalyzed

Reconstitutive

Condensation. Application to Functionalbed

Steroid Side

Chains

B. M. TROST, R J. KUZAWIEC and A. HAMMES, Temhednm

bis(Tripheny1phosphe)cyclopentadienylruthenium

chloride catalysed the addition of steroidal acetylenes with ally1 alcohols to introduce functionalised side chains illustrated by the construction of the side chain of ganoderic acid which is a novel angiotensin-con- verting enzyme inhibitor. The excellent chemoselec- tivity and atom economy of the

Ru

catalysed reconstitutive condensation make it a useful method for elaborating steroid side chains with minimal need for protecting groups.

Studies

on

Transition-Metal

0 x 0

and Nitrido

Complexes.

13. Perruthenate and Ruthenate

Anions

as

Catalytic Organic Oxidants

A. J. BAILEY,

w. P.

G R I F ~ ,

s. I.

MOSTAFA and P. A. SHERWOOD,horg. Chem., 1993,32, ( 3 , 268-271 The [RuOJ ion, which was generated in aqueous base at pH 1 1 from aquated RuCl,.nH,O with

BrO,-

as co-oxidant, catalytically oxidised primary alcohols, activated alkyl halides, aldehydes, 1,2-diols and nitroalkanes to carboxylic acids. However, the sec- ondary alcohols and halides were oxidised to ketones, bromate being the co-oxidant.

htt., 1993, 34, (4), 587-590

FUEL CELLS

A Unitized Approach

to

Regenerative Solid

Polymer Electrolyte Fuel Cells

H. P. D ~Appl. Electrochem., 1992,23, (l), 32-37 J Unitised regenerative fuel cell data were obtained with a cell design which allows the same unit to function both as a power producer and as an electrolyser. The cell contained Pt/C and Pt/Ir/C gas diffusion electrodes on the 0 side and W C electrodes on the H side, membranes and a solid polymer electrolyte, usually used in fuel cells. The current-potential data in the regenerative electrolysis decreased with time but the fuel cell current was very stable. The membrane-electrode assemblies functioned well, and no visible corrosion was observed.

Surface and Catalytic Properties of Iron-

PlatindCarbon Electmcataly&a for Cathodic

Oxygen Reduction in PAFC

K . T. KIM, J. T. HWANG, Y. G. KIM and J. s. CHUNG, 3. Elecmchem. SOC., 1993, 140, (l), 31-36

Studies of surface and catalytic properties of Pt-Fe catalysts were made in phosphoric acid fuel cells, on catalysts prepared by impregnation of Fe(NO,), solution into WC. The catalyst was heat-treated in a flow of Ar at 450,750 and 900"C, or this process was followed by an acid-treatment in 1 M H,SO,. With increased heat-treatment temperature, the Pt surface area measured by H chemisorption decreased rapid- ly due to particle sintering, an alloying effect and enrichment of Fe on the surface.

Direct Electrooxidation of Methanol

on

Highly Dispersed Platinum-Based Catalyst

Electrodes: Temperature Effect

G. h&U, 1.-M. L ~ G E R , c. LAMY and R DURAND, J Appl.

The direct elemoxidation of MeOH in acid medium was studied on a perfluorinated Nafion membrane containing small amounts of Pt, about 1

mgkm', and other metal catalysts, incorporated by chemical reduction. Pt modified by other metals was the best catalyst to obtain oxidation potentials much more compatible with a working anode in a direct MeOH fuel cell. Ru and Sn lead to a negative shift of > 250 mV as compared to the potential obtained with pure Pt.

Platinum-Iridium Bimetal Catalyst-Based

Porous

Carbon

Eleetrodea for H,-Cl, Fuel Cells

S. M. A. SHlBLl and M. NOEL, In?.

3

Hydrogen Energy,

Teflon bonded Pt-Ir bimetal catalyst-based porous electrodes were prepared for use in H,-Cl, fuel cells. These gas d f i s i o n electrodes, fabricated by a hot pressing technique, had optimised performance at

2.5 wt.% Pt and 5 wt.% Ir, for both H, oxidation and C1, reduction reactions. The fuel cells has optimised operation at 333 K, gas pressure of 60 mm Hg on both electrodes, 5 M HCl electrolyte and interelec- w d e distance of 6 mm. Under these conditions wlt- ages of 1 .O V at current densities of 100 W c m 2 for

300 h were obtained.

E l e ~ m c h t ~ ~ . , 1993,23, (3), 197-202

1192, 18, (2), 141-147

CORROSION PROTECTION

The Nature

of

the Passive Film

on

Cathodieally Modified Stainless Steels

Elecmchem., 1993,23, ( l ) , 11-18

The effect of additions of platinum group metals on the composition of the passive surface layer formed on stainless steels in reducing acid media was studied. An accumulation of the platinum group metals occurred on the surface of the alloy during the peri- od of active dissolution.

J. H. POTGIETER, W. SKINNER and A. M. HEYNS,J Appl.

CHEMICAL TECHNOLOGY

Alloys

of

Palladium with Metals of the

Platinum Group

as

Hydrogen-Permeable

Membrane Components

at High

Temperahma

of Gas Separation

F. N. BERSENEVA, N. I. TIMOFEEV and A. B. ZAKHAROV, Inr. J Hydrogen Energy, 1993,18, ( l ) , 15-18 Studies of the effect of phase composition of the binary Pd-Pt and Pd-Rh matrices in which the concentration of Pt and Rh in the uniform f.c.c. solid solution was 0-25%, were performed. The effects of dissolved H on the phase composition and mechan- ical properties of Pd-Pt and Pd-Rh alloys were exam- ined. Multicomponent alloys of Pd with platinum group metals are suitable membrane materials.

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ELECTRICAL

AND ELECTRONIC

ENGINEERING

Optimization of the Tradeoff between

Switching Speed of the Internal Diode and

On-Resistance in Gold- and Platinum-

Implanted Power Metal-Oxide-Semiconductor

Devices

M. F. CATANIA, F. FRISINA,N.TAVOLO, G. FEFL4,S. COFFA

and S. U. CAIWISANO, IEEE Trans. Electron Devices, 1992,39, (12), 2745-2749

The effect of

Pt

and Au doping on the switching characteristics of the internal diode of power MOS devices was studied. The tradeoff curve between the on-resistance of the device and the reverse recovery charge of its internal diode was measured after diffusion of the metallic impurities. It is concluded that Pt implan- tation applied to power MOS device fabrication gives an improved tradeoff between dynamic and static device characteristics with respect to Au doping. High-

voltage n-channel power MOS devices with a fast internal diode and a limited increase in the on-resistance were produced by this fabrication process.

Ti/Pt/Au Ohmic Contacts

to

n-Type ZnSe

T. MIY~TIMA, H. OKIJYAMA and K. AKIMOTO,

Jpn.

J

Appl. Phys., Pan 2 Lett., 1992, 31, (12B), L1743-L1745 A Ti/Pt/Au multilayered metal structure was found to form a nonalloy ohmic contact to n-ZnSe with an electron concentration of 1019/cm3. A specific contact resistance as low as 3.4 x104R an* was obtained for an n-type C1-doped ZnSe layer with a high electron concentration of 2 x 101q/cm3. The lower contact resistance can be ascribed to the higher reactivity and adhesion of Ti metal with the surface of ZnSe at low temperature, and to the lower work h c t i o n of Ti metal. A small improvement in the specific contact resistance was made by thermal annealing at 250°C for 5 min, which yielded the lowest value of 1.1 x lo4 Q anz. The electrical properties of the contact are stable up to 300°C.

Magnetooptical Spectra in PtlCo and PtlFe

Multilayers

K. TSUZUKIYAMA, Y . TOGAMI, M. FUJISAWA and T. FUKAZAWA, Jpn.

3.

Appl. Phys., 1992, 31, (1 l),

Magnetooptical (MO) spectra were measured at 1.2-5.9 eV in Pt/Co and Pt/Fe multilayers and corresponding Pt-Co and Pt-Fe alloys which were produced by DC magnetron sputtering. Simulation of MO spectra performed by the virtual optical constant method showed that spectral behaviour of multilayers can be explained by formation of an alloy layer of thickness

-

6.5

A

at the interface between the Pt layer and the transition metal layer comprising the multilayers. The off-diagonal conductivities obtained suggest that magnetooptical spectra of multilayers are caused by those of corresponding alloys formed at the interface.

K. SATO, H. HONGU, H. IKEKAME, J. WATANABE,

3603-3607

Microstructures of Pt/Co Films Deposited

on

Sputter-Etched Underlayers

TSUNASHIMA and S. UCHIYAMA, Jpn.

3.

Appl. Phys.,

k/Co multilayered films deposited on a sputter etched SiN underlayer show larger magnetic anisotropy, 1 x 10' erg/cm3, and better squareness = 1, than those on non-etched underlayers. The etching is shown to improve the multilayer structural order. The etching of underlayers transforms the Pt/Co films &om island structure to continuous structure in an early stage of film growth. SEM and STM suggest that the sputter etching flattens the surface of the underlayer.

Subpicosecond Photoinduced Switching of

Second-Harmonic Generation from a

Ruthenium Complex

in

Supported

Langmuir-

Blodgett Films

S. SUMI, K. TANASE, Y. TERAGAKI, K. TORAZAWA, S.

1992,31, (lo), 3328-3331

H. SAKAGUCHI, L. A. GOMEZ-JAHN, M. PRICHARD, T. L. PENNER, D. G. WHITTEN and T . NAGAMURA,

3

Phys. Chem., 1993,97, (8), 1474-1476

Ultrafast modulation of the second harmonic (SH) intensity &om a Langmuir-Blodgett film consisting of a Ru complex, Ru bipyridyl, with one of the ligands being substituted by amide groups, is shown by laser irradiation of the film at 1064 nm. The switching of the SH intensity is shown to occur in less than 2 ps by a picosecond pump-probe experiment.

Size Effect

on

the Electrical Conduction and

Noise of Ru0,-Based Thick Film Resistors

B.-S. CHIOU, J.-Y. SHEUand W.-F. W W , J Electron. Muter.,

The temperature dependence of sheet resistance for a generic Ru0,-based resistor of composition 20

12 Wt.%SiO,) was evaluated. A combined tunnevpar- allel conduction model was used to describe the resistance behaviour with respect to temperature variation. The geometry of the film, such as aspect ratio and thickness, has a significant effect on the electrical characteristic of the thick film assembly.

1992, 21, (12), 1105-1110

Wt.%R~0,-80 W.% glass (63 ~t.%Pb0-25 wt.%&O,-

MEDICAL USES

Crosslinking of Adjacent Guanine Residues

in

an

Oligonucleotide

by

cis-

[Pt(NH,),(H,O),]z': Kinetic Analysis of the

Two-step Mechanism

F. GONNET, J. KOZELKA and I.-C. CHOTTARD, Angew. Chem. Int. Ed. Engl., 1992, 31, (lo), 1483-1485 A new method for determination of the four rate constants of the two-step reaction between an oligonucleotide containing a GpG unit and cis- [Pt(NH,),(H,O)JZ' has been developed. The method consists of treating known amounts of oligonucleotide with nearly stoichiometric Pt complex in aqueous solution, and periodically taking aliquots which are quenched by addition of a saturated KCl solution followed by cooling to liquid N, temperature.