ABSTRACTS: July 1991152-165

ABSTRACTS

of current literature on the platinum metals and their alloys

PROPERTIES

Scanning Tunneling Microscopy

of

the

Annealing of

a

Thin

Platinum Film on

Highly

Oriented Pyrolytic Graphite

X. CHuAN ZHOU and E. GULARI, Acta ctyst., 1991,

Scanning tunneling microscopy was used to study morphological changes in a thin

Pt

film deposited on highly oriented pyrolytic graphite (HOPG) during annealing. In air the film could be imaged with a ver- tical resolution of 0.5A and a lateral resolution of 20A. After annealing below 573 K surface mor- phology changed only slightly; at 573-873 K the originally uniformly distributed “rolling hills” of Pt

coagulated into larger lumps. Above 873 K Pt crystal facets started to form on the surface. At 1123 Kmuch of the surface turned into well defined F’t crystal facets. Above 1123 K the

Pt

f h started to crack and formed scattered crystals on the HOFG surface. The crystabed Pt was preferentially oriented with the (1 11) plane parallel to the substrate graphite (0001) basal plane, indicating epitaxy of the

Pt

overlayer with the graphite substrate underneath.

Kinetic

Studies of the Chemical Vapor

Deposition of Platinum

S. ROY and P. A. YOUNG, Chem Muter., 1991, 3, (2),

The chemical vapour deposition

(CVD)

of

Pt

was monitored by

FTIR

and UV spectroscopies using cis-[PtMe,(MeNC),l as precursor in order to ex- amine the effects of H, and UV irradiation, which can enhance CVD.

Pt

deposition in a 2 cm pathlength UV cell under

UV

irradiation at <300 MI occurred on a pyrex target. Irradiation at longer wavelengths gave negligible deposition. The effect of H, in a 10 cm pathlength pyrex cell was to accelerate the reaction.

Hydrogen,

Hydrogen

SuKde

and

Hydrocarbon Coadsorption on P t ( l l 1 )

and Pt(l10): Selective Formation of

A47, (l), 17-21

B. MXON, P. R. NORTON, E. C. OU, R. J. PUDDEPHATT,

222-224

Alkylthiols

D. VASSILAKIS, C.-M. PRADIER, Y. BERTHIER and J. OUDAR, Appl.

surf. Sci., 1991,

47, (3), 273-280 The simultaneous adsorption of diolefme, H, and H, S on Pt single a y s t a l s forms mercaptan and alkanes. The nature, amount and temperature of desorption of these p d u c t s depend on the size and configuration of the diolefme and on the structure of the surface. Mechanisms are proposed to explain the observed surface reactions. Some compounds are selectively produced when H, S reacts firstly with the diolefme; this occurs with C,H, on (111) and (110) orientations, and with C,H, on Pt(ll0).

Magneto-Optical

Kerr

Effect and Perpen-

dicular

Magnetic

Anisotropy

of

Evaporated

and

Sputtered

Co/Pt

Multilayer Structures

McDANIEL and H. Do,

3.

Appl. Phys., 1991, 69, (7),

Thin and ultrathin Co/Pt multilayered structures were prepared on glass substrates by electron-beam evaporation at room temperature and by sputtering at various substrate temperatures and sputtering pressures. Perpendicular magnetic anisotropy was found in samples with Co/Pt bilayer thicknesses near 3 &lo

A

and total thicknesses of the layer stack of (300

A.

The effects of sputtering parameters, such as pressure and substrate temperature, on the magneto-optical Kerr effect were studied.

Perpendicular Magnetic Anisotropy

in

PtlFe Multilayers

and M. HASHIMOTO,

3.

Appl. Phys., 1991, 69, (S),

Perpendicular magnetic anisotropy and related magnetic properties in Pt/Fe multilayers were in- vestigated. Pt/Fe com sitionally modulated f h s (CMFs) with

-

an 18w”pt layer and Fe layer <5A become perpendicularly magnetised films. Surface magnetic anisotropy (KJ was 0.46 erg/cmz and volume anisotropy (K.,) was

-

-2 x 10’ erg/cm3 at room temperature. The K, is almost equivalent to that of Pt/Co CMFs and increases with decreasing temperature. The absolute value of K., is much larger than that of the Pt/Co s stem. The effective

changes from positive to negative at T

-

200 K with decreasing temperature.

Permanent Magnetic Properties

in

Fe-Pt-

Nb

System Alloys

P. HE, W. A. MCCAHAN, J. A. WOOLLAM, F. SEQUEDA, T.

402 1-428

T. KATAYAMA, Y. SUZUKI, Y. MSHIEURA, T. SUGMOTO

Part IIB, 5658-5660

magnetic anisotropy of IFe(4.7

x

)/Pt(18.5A)Im CMF

K. WATANABE,

3.

3m.

h t . Met., 1990, 54, (11), 1284- 1290

Magnetic properties and temperature dependence of Fe-Pt-Nb ternary alloys were investigated by various techniques. Permanent magnetic properties were ob- tained by water-quenching from the 7-phase region and tempering at -850-900 K in the phase region. A Fe-39.5 at.%Pt-0.75 at.%Nb alloy exhibits the maximum energy product of 167 kJ/m3, with a residual flux density of 1.05 T and a coercivity of 398 kA/m. These properties are superior to those of basic binary Fe-Pt. The Fe-Pt-Nb composition range is wider than that of Fe-Pt, so the heat-treatments can be easily controlled, and the reproducibility of the magnetic properties can be improved. Fe-38Pt-1Nb has excellent rectangular hysteresis loops at 400 and 290 K with stable thermal properties.

Amorphous Phase Formation in an As-

Deposited Platinum-GaAs Interface

D.-H. KO and R. SINCLAIR, Appl. Phys. Lett., 1991,58,

A thin amorphous intermixed layer at the Pt-GaAs in- terface in as-deposited Pt/GaAs and Si/Pt/GaAs

samples has been investigated by various techniques. The intermixed layer forms below the native oxide of the GaAs substrate and consists of the elements: Pt, Ga and As. It is suggested that this layer forms during the deposition process of the Pt.

High Temperature Reactions between

Sic and Platinum

T. C. CHOU,

3.

Muter. sci., 1991, 26, ( 5 ) , 1412-1420 Solid state reactions between Sic and

Pt

were per- formed at 900-11OO0C. In the reaction zones, alter- nating layers of

Pt,

Si and C, and Pt,Si and C were formed at 900 and looO°C, respectively. Both the Pt,Si and R,Si phases were stable at respective temperatures, but annealings at ll0OoC produced alternating layers of mixed Pt silicides and C. The formation of Pt silicides gave rise to interfacial melting between Sic and Pt and Sic decomposed into C and Si at all the temperatures. The Si reacted with Pt and formed Pt silicides, while the carbon formed clusters and was unrective.

Solid State Reactions of Sic with Co, Ni,

and Pt

T. c . CHOU, A. JOSHI and J. W A D S W O R ~ ,

7.

Muter. Res., 1991, 6, (4), 796-809

Solid state reactions between Sic ceramics and Pt, Ni and Co were studied at 800-1200OC for various times under He or vacuum. The WSiC reactions at 900, 1000 and ll0OoC were very similar to each other; in- terfacial melting was observed and Pt,Si, Pt,Si and a mixture of Pt silicides, respectively, were formed upon annealing. C precipitation behaviour, annealing conditions, diffusion phenomena and major reaction products for diffusion couples are given. A CPFZ(C precipitation free zone) was generated in Ni/SiC and &/Sic but not in Pt/SiC. While a CPZ(carbon precipitated zone) was formed in all the systems, both M-CPZ(modulated) and R-CPZ(random) were noted in the Pt and Ni systems, but only a R-CPZ in the

Co

system.

Magnetic-Field-Induced

Strong

Diamagnetic Transition

in

the Quasi-One-

Dimensional Halogen-Bridged Platinum

Complex

[Pt(en) I[Pt(en)

212

I(Cl0,)

(Where

en

Represents Ethylenediamine)

M. HARuKI and P. WACHTER, Phys.

Rev.

B,

1991,43,

DC magnetisation measurements on the quasi-one- dimensional halogen-bridged Pt title complex show a magnetic-field induced strong diamagnetic transition at fields above 20 kOe. The diamagnetic signals are

as large as 3.5-72% of complete diamagnetism and show large fluctuations. The transition temperature to pararnagnetkm is at

-

180 K.

(17), 1851-1853

(7), 6273-6276

Interfacial Reactions between Palladium

Thin

Films and

InP

D. G . IVEY, L. ZHANG and P. JIAN,

3.

Mazer. sci., Muter. E l e c n m , 1991, 2 , (l), 21-27

The reaction between a thin layer of Pd( = 100 nm) and an InP substrate was studied at annealing temperatures of 250-45OOC for up to 30 s, which are typical annealing conditions encountered during con- tact fabrication. Pd reacted readily with InP forming an amorphous ternary phase which later transformed to crystalline Pd,InP on annealing. Pd,InP had an ordered cubic structure, and mkrotwins, 2-3 atomic layers thick, were identified in the ternary phase and these formed along the (110) and (1 10) planes.

Comparative Study

on

Phase Formation

in AI-Pd

Thin

Film by Ion Beam Mixing

and Thermal

Annealing -

R. Y. LEE, J. H. PARK and

c.

N. WHANG,

3.

Muter. sci.,

1991, 26, (3), 721-725

Ion beam mixing and/or thermal annealing were con- ducted to study the phase formation and dissociation in Al-Pd thin films prepared by sequential evapora- tion. The intermetallic compounds formed by ion mixing with

Ar+

were found to be Al3PdZ and AlPd at a dose of 1.5 x 10l6 Ar+/cm2. Thermal annealing after t h i s radiation gave two new phases of All Pd and Al,Pd, in addition to AllPd2 and AlPd. For an as- annealed sample without

Ar+

bombardment, the observed phases are Al, Pd, Al Pd 2 and AlPd.

Retardation

of

Grain

Boundary Reactions

in Ag-Pd-Cu AUoys by Additions of Small

Amounts

of Other Elements

I. KAWASHIMA, Y. ARAI<I and H. OHNO,

3.

Muter. Sci.,

The grain boundary reactions in Ag-ZS%Pd-lO%Cu (mass%) with 1% of Al,

Co,

Sn,

G

or In were studied. Addition of Sn and

G

retarded grain boun- dary reactions. Grain interior reactions were ac- celerated with Q, Sn and In additions, with

G

being the most effective. The activation energies for the grain interior and grain boundary reactions were 192-1% and 144-208 kJ/mol, respectively. Addi- tions retarded the growth but not the nucleation at the grain boundary.

Mechanical-Strain-Induced Influences

on

Hydrogen Diffkion within Pd,,Ag2,

AUoy Membranes

x.

Q. TONG and P. A. LEWIS,

3.

Less-Common Met.,

Sudden changes in H z gas pressure on the upstream side of tubular membranes of Pd7,AgZl and Pd,,

Pt

,,

alloys are known to produce complementary changes of H pressure an the downstream side; this has been attributed to “elastic dynamic” or “mechanically in- duced memory” effects. Further experiments show that such effects could be associated with combina- tions of Gorsky effect and self-strain-induced diffusion-elastic effect migrations of H interstitials in the walls of the membranes.

1991, 26, (4), 1113-1118

1991, 169, (l), 157-165

Hydrogen Permeable Palladium-Silver

Alloy

Membrane Supported

on

Porous

Ceramics

S. UEMNA, T. MATSUDA and E. KIKUCHI, J . Membrane

Sci., 1991, 56, (3), 315-325

The H permeability and selectivity of a composite membrane consisting of misable Pd-Ag alloy film supported on the outer surface of a porous alumina cylinder were investigated. The membrane had much higher flux than commercially obtained Pd-based membranes for H separation. The high H flux was due to the thinness of the f h and its high H solubili- ty. H embrittlement was suppressed by alloying the thin Pd film with Ag, and 100% H selectivity was re- tained even at relatively low temperatures.

On the Origin of

a

Lattice Expansion

in

Palladium and Pd-Au Vapour Deposits

on

Variaus Substrates

c. KUHRT and R. ANTON, Thin Solid Films, 1991, 198,

Vapour deposits of'Pd and Pd-Au alloy particles and films were produced under UHV or in high vacuum, with and without the admission of H,O, on amor- phous fdms of C and SiO, and single crystal surfaces of NaCl and KBr. In all cases lattice expansions of up to 2.6% were measured, depending on the condition of degassing of the substrate and on the residual gas composition during deposition, especially with respect to water vapour. Lattice expansion correlated with the presence of H on or in the substrate materials, as detected by SIMS.

Mechanical Behavior

of Nanocrystalline

Cu and Pd

Muter. Res., 1991, 6, (3, 1012-1027

Bulk mechanical properties of nanocrystalline Pd and Cu samples, consolidated from powders prepared by inert gas condensation, were measured. Average grain sizes were 3-50 nm and mean lattice strains ranged from 0.02-3%. Densities rang from 97-72% of that of a coarse-grained standard. Microhardness exceeds that of annealed, coarse-grained samples by a factor of 2-5, despite indications that sample porosity reduces hardness values below the ultimate value. Uniaxial tensile strength is also high.

The

Palladium-Rich P&Ho(Er) Systems

Y. SAKAMOTO, K. TAKA0 and Y. NAGAOKA, J . Muter.

Pd-Ho and Pd-Er alloys containing 10-21.0 at.% Ho(Er) prepared by arc-melting in

Ar

and heat treated to

-

1193 K for 10 min followed by quen- ching in iced H,O were studied by various metallographic, spectroscopic and electrical resistance measurements. It is concluded that the magnitude of the order-disorder transition temperature,

T,,

for the reaction a-Pd

+

L1,-type Pd,RE (or

W,RE

where RE is

Ce,

Sm or Eu)=Pd,RE of the Pd-RE alloys is due to the mag- nitude of the metallic radius of the rare-earth metals. (1-2), 301-315

G . W. NIEMAN, J. R. WEERTMAN and R. W. SIEGEL, J .

S C ~ . , Lett., 1991, 10, (6), 341-344

A

Contribution

to

Coupled Reduction of

Rare Earth Oxides with Pd and H,

and R. FERRO,

z. Metallkd.,

1991, 82, (3), 169-173 Stoichiometry and structural types of Pd-rare earth alloys are presented. Results from reacting Gd,O,- Pd mixtures with H

,

are reported. For alloys contain- ing up to 20 at.% Gd the reduction was nearly com- plete and Pd-rich Gd-Pd alloys were obtained. For Pd solid solutions containing up to

-

12 at.% Gd nearly single-phase samples of composition close to the nominal ones were obtained. For 10-22 at.% Gd when two solid phases, Pd and GdP,, are stable at temperatures over 537OC, twephase alloys not too far from the nominal ones of eutectic appearance were obtained.

Kinetic and Thermodynamic Investiga-

tion of Hydrogen Absorption by Ternary

LaNi

Al and LaNi A1-Pd Alloys

M. v. SUSIC and Y. M. SOLONIN, Int. J . Hydrogen

Differential scanning calorimetry and X-ray analysis of H, absorption by ternary LaNi,Al and a LaNi,Al- Pd alloy containing 4 % Pd showed that in a flowing

H,

atmosphere H absorption by the fmt alloy took place exothermally at about 150 and 45OOC. The alloys containing Pd behaved similarly with absorp- tion facilitated by the presence of Pd, and the forma- tion of a new phase with a phase transition at 150°C was observed.

Mechanical Alloying of the Pd-Si System.

Investigation of the Early and

Late

Mill-

ing

Stages

V. CONTARDI, R. MARAZZA, G. RAMBALDI, G. ZANICCHI

Emrgt, 1991, 16, (4), 271-276

M. MAGINI, N . BASILI, N . BURGIO, G . ENNAS, S. MARTELLI, F. PADELLA, E. PARADISO and P . SUSINI, Muter. Sci. Eng., 1991, A134, 1406-1409

Four Pd-Si compositions: Pd,.,Si, Pd,Si, Pd,Si and Pd

,

Si, have been processed by mechanical alloying. After the early milling stages, consisting of very fine fragmentation of the Si particles into a Pd matrix, the Pd Si, Pd, Si and Pd, Si can nucleate intermetallic Pd

,

Si, depending on the milling conditions and/or the milling apparatus. Further milling seems to pro- mote amorphisation, probably starting from the previously formed Pd

,

Si compound.

Standard Molar Enthalpies of Formation

of Me,Ge, (Me Zr,

Nb,

Mo),

MeGe

(Me

Ru, Rh, Pd) and PdlGe by High-

Temperature Calorimetry

W.-G. JUNG and 0. J . KLEPPA, J . Less-Common Met.,

The standard enthalpies of formation of the above 4d

transition-metal germanides were determined using a high-temperature calorimeter at 1473+2 K. Liquid (Ni

+

Ge) alloys were used as solvents in the solute- solvent drop experiments, and values were obtained for Zr,Ge, and

I%,&,.

Values of -56.9e1.4 kJ/mol for R U G , - 113.8k2.1 kJ/mol for RhGe and

-92.921.5 kJ/mol for PdGe were obtained. 1991, 169, (l), 93-103

Hydrazine Decomposition on a Clean Rhodium Surface: A Temperature Pro- grammed Reaction Spectroscopy Study J. PRASAD and J. L. GLAND, hngmuir, 1991, 7, (4), 722-726

The adsorption, desorption and decomposition of N,H, on a Rh foil surface was studied as a function of its coverage by temperature programmed reaction spectroscopy. The gas-phase products observed de- pend markedly on the initial hydrazine coverage. At low coverage only H, and N2 desorb from the sur- face, but at near monolayer Coverage H,, NH,, N, and diimide are observed. Simultanmus desorption of N2 and NH, at 220 K for high coverages suggests the direct decomposition of hydrazine N,H,- N, +H(ad) and N,H,+H(ad)-NH,. Diimide for- mation was observed over a wide range of N,H, coverages above 220K

Dissociation of Nitric Oxide and Reaction with Hydrogen on Rh(l11) and Various Stepped Rh(ll1) Surfaces

Surf. Sci., 1991, 246, (1-3), 135-140

The reaction between NO and H, was studied on Rh(ll1) and stepped surfaces: Rh(331), Rh(211) and Rh(321) by scanning field emission probe-hole microscopy. Reaction start-up temperature strongly depends on NO coverage, and is sensitive to surface structure. At low NO coverage the reaction starts by 240 K on Rh(321), and at a much higher temperature on Rh(211) and Rh(ll1). On Rh(321) characteristic features of both (100) and (1 11) steps are observed.

Infrared Spectroscopy at High Pressure. Interaction

of

N 2

with

Rh/Al,O,

at

Am-

bient Temperature

WORLEY,

3.

Am. Chem. Soc., 1991, 113, (8),

A new high-pressure infrared cell reactor capable of variable temperature operation was used to study the interaction of N, with Rh/Al, 0, catalyst fdms in the pressure regime 1 x to 9000 Tom at 298 K. The results were in good agreements with those previously obtained for similar catalysts at low temperatures and pressures. Infrared bands for chemisorbed and physisorbed N, species were detected and assigned.

Solidifcation

of

Copper-Rhodium Alloy Single Crptal~

R. M. WOLF, J. W. BAKKER and B. E. NIEUWENHUYS,

J. P. WEY, H. D. BURKElT, W. C. NEELY and S. D.

2919-2922

M. P. DELPLANCKE, M. JARDINIER-OFFERGELD and F. BOUILLON, Mater. Chem. Phys., 1991, 27, (3), 225 -2 33

The preparation of Cu-Rh alloy single crystals by the vertical Bridgman method is described. Dendritic structures are formed during the solidification pro- cess of 1.5, 4, 8.75 and 15 at.%Rh alloys. Various methods are used to characterise the solute distribu- tion. Formation conditions and the thermal stability of the structures are also discussed.

Ditrusion of Ir-Dimers on Ir(l10)

Sur-

faces by Atomic-Exchange and Atomic- Hopping Mechanisms

T. T. TSONG and c.-L. CHEN, Surf. Sci., 1991, 246,

On the Ir(ll0) surface, single Ir adatoms and Ir- dimers can diffuse along, as well as across, the 1101 surface channels. The across-channel diffusion most probably occurs by an atomicexchange mechanism. The visited-site-lattice for Ir and Ir, is the (1 x 1) net of the substrate lattice. Atomic jumps are concluded to extend only to the nearest-neighbour sites. For single Ir-adatoms, a s i o n across the channels is easier than along the channels. For Ir-dimers the along-channel diffusion is easier. The energies need- ed for single Ir-atoms and I r - h e r s to hop along the channel and to displace across the channel by atomic exchanges are derived. The binding energy of the dimer is 1. 10+0. 11 eV.

Structure and Magnetic Properties

of

FeRuGaSi Multilayer Thin

Film

(1-3), 13-24

T. M. JAGIELINSKI, A. M. ZELTSER and C. F. BRUCKER,

J. Appl. Phys., 1991, 69, (8), Part IIB, 5628-5630 The structure and magnetic properties of FeRuCaSi thin films used in VHF (150 MHz) recording heads have been studied. The best soft magnetic properties of coercivity (0.2-0.3 Oe), permeability (2000 at 1

MHz and 400-500 at 150 MHz), and magnetostric- tion ( < W 6 ) , were obtained after annealing at 450-50O0C. This magnetic behaviour is attributed to the phase transformations and the increase in the

grain size of the films occurring during annealing.

Phase Equilibria in the RuO -Bi

0 X u 0

System

Len.,

1991, 10, (2), 69-70

Studies of interactions between CuO and the conduc- tive phases RuOz or Bi,Ru,O, in thick-fdm resistors have been performed and the ternary phase diagram of the Ru0,-Bi,O,-CuO system is presented. The phase equilibria indicate reactions between the con- ductive Bi,Ru,O, phase in thick-fh resistor material and the CuO, which was added as a temperature coefficient of resistivity modifier, with CuO being incorporated into the pyochlore crystal structure, resulting in the Bi, - , C ~ R u , O , solid solution. When RuO, was the conductive compo- nent, CuO did not react with it.

Growth and Characterization of RuSe, Single Crystals

Mazer. Res. E d . , 1991, 126, (l), 11-17

Single crystals of RuSe,, up to 10 x 8 x 6 mm’, were grown by an oscillating chemical vapour transport method using ICI, as the transport agent. Optimum conditions for the growth of large single crystals are given. Crystal stoichiomeuy is discussed, and electrical resistivity and Halleffect measurement indicate n-type semiconducting properties.

S. BERNlK, M. HROVAT and D. KOLAR, J . Mater. sci.,

J.4. SHEU, Y.-S.SHIH, S.4. LIN and Y . 4 . HUANG,

CHEMICAL COMPOUNDS

Crystal Growth and Properties of

R2Ba2CuPt08 (R

=

Ho, Er, Y),

R 2

Ba Cu, PtO

,,,

and Ba, CuPt

O9

and T. FUKUDA,

3.

Cyst. Growth, 1991, 109, (1-4),

Three new Pt complex oxides have been identified as products of the CuO-flux growth of R-Ba-Cu-0 (R =

Ho, Er, Y) superconducting oxides in

Pt

crucibles. These oxides are formed under normal atmospheric conditions and a growth mechanism for the com- pounds involving incorporation of Pt from the crucible is proposed. The crystal structure of R,Ba,CuPtO, has been determined. The T-1”

temperature dependence of the conductivity is ex- plained by a

-Cu~+-O~--Pt‘+-O~-

conduction chain model. The magnetic susceptibility measurements reveal an antiferromagnetic interaction of spins Ho”, El’+, and Cuz+.

High-Nuclearity Platinum-Osmium Alloy

Cluster

Complexes.

Synthesis

and

Structural Characterizations of Pt

0 s 6

-

(CO)

2 2

(COD) and Pt,

a 6

(CO)

21

(COD)

2 R. D. ADAMS, J.C. LII and w. wu, Inorg. Chem., 1991,

The f m t example of a possible series of new high- nuclearity Pt-0s carbonyl cluster complexes having structures based upon alternating layers of Pt and 0 s

are reported. The clusters were formed when Pt,0s3(CO),,,(COD),, where COD is 1,s-cyclo- octadiene, was refluxed under N, for 30 min.

The Synthesis of Os3Pt Clusters. X-ray

Crystal Structure of Os,Pt(CO)

I I

(PPh3)2

D. H. FARRAR, R. R. GUKATHASAN and J. A. L~NNISS,

Inorg. Chim. Acra, 1991, 179, (2), 271-274 The reaction of 0s,(CO),,(NCMe) (1) with sources of PtL, gave new clusters 0s,Pt(CO),,L, as major products, where L is PPh, or

PBu,Ph.

Each 0s-Pt edge was bridged by a carbonyl ligand, while the re- maining nine carbonyl ligands were terminally bound to 0s atoms. The minor products from the reaction of (1) and PtL, were phosphine-substituted derivatives of Os,(CO),, and the raft clusters 0s,(CO),, -,(NCMe), with n = 1, 2. Crystal struc- tures of the products are given.

Syntheses and Crystal Structures of

[Pd9As8

(PPh,)

D. FENSKE and c. PERSAU,

z.

Anorg. Allg. Chem., 1991, 593, (2), 61-68

A new cluster [Pd,As,(PPh,),l which was prepared by reaction of [PdCI,@Ph,),l with As(SiMe,), was characterised by X-ray crystal structure analysis. The cluster molecule has four [Pd,(PPh,),l units bridged by As, units with a further Pd atom being located in the centre of the cluster. The reaction of [PdCl,(PPh,),l with Sb(SiMe,), yielded [Pd,Sb,(PPh,),l which has a b.c.c. Pd,-cluster.

Y. SAITO, T. SHISHIDO, N . TOYOTA, K. UKEI, T. SASAKI

426-43 1

30, (lo), 2257-2258

and [I’d9 Sb 6(PPh3)

Structural,

Magnetic,

and

Charge

Transport Properties of Bis[(5,10,15,20-

Tetrameth ylporph yrinato)Palladium(II)l

Perrhenate, [Pd(tmp)l [ReO,

1

E. M. MCGHEE, B. M. HOFFMAN and J. A. IBERS, Znorg.

Chem., 1991, 30, (9), 2162-2165

Electrochemical oxidation was used to produce the new molecular conductor [Pd(tmp)l ,[ReO, 1, which is composed of partially oxidised Pd(tmp) cations stacked metal-over-metal and surrounded by chains of ReO, anions. Single crystal room temperature con- ductivity along the needle axis averages 30/Q cm, and can be fitted to an expression that describes a semiconductor with temperature-dependent carrier mobility, and is comparable with that of the best

Pt-

spine conductors, despite the interplanar separation being -3.38

hi,

compared to that for

Pt-Pt

of 2.95

hi.

This conductor is isostructural with [Ni(tmp)l ,[ReO,l and LCu(tmp)l ,[ReO,I.

Ring

Migration

Reactions

of

(C5Mes)Rh(PMe3)H2.

Evidence for

q 3

Slippage and Metal-to-Ring Hydride

Migration

w. D. JONES, v. L. KUYKENDALL and A. D. SELMECZY,

Orgamtallics, 1991, 10, ( 3 , 1577-1586

The reactions of (C,Me,)Rh(PR,)H, (PR, =PMe,, PMe,Ph, PMePh,, PPh,) with D, gas occurred quickly at 25OC, leading to the stepwise exchange of H for D. Kinetic studies showed a second-order reac- tion mechanism involving Rh and D. (C,Me,)Rh(PMe,)H, also reacted with PMe, at 4OoC to yield C,Me,H and HRh(PMe,), in a reac- tion displaying bimolecular kinetics. Isotope effect studies showed no rate difference with the dideuteride

Rh

complex.

Synthesis

and

Reactivity of

Rhodium(I)

Complexes

of

the

Type

Rh(G

E. KwASKOWSKA-CHEC and A. M. TRZECIAK, Transinim Met. Chem., 1991, 16, (2), 212-214

The carbonyl ligands in the Rh’ complexes Rh(L-L)(CO), (L-L is anthranilate (AA) or N-phenylanthranilate (FA) ions) were replaced by P(OPh), to form the mono- or disubstituted products. Under

Ar

at [P(OPh),lfiRhl)4 the ortho-metdated Rh’ complex Rh[P(OPh) I

-

[P(OC,H,)(OPh),l was formed. The Rh(AA)(CO), complex was used as a catalyst precursor in hydro- formylation of olefms.

Reaction of Ru(q-RC5

H4)C1(PPh3)2

with

Carbon Dieulfide

Coord. Chem., 1991, 22, (4), 255-258

The reaction ofCS, with Ru(q-C,H,)Cl(PPh,), pro- duced [Ru(q-C,H,)(CS,)(PPh,),l+ by two different routes. Results suggest that the formation of the CS, derivatives is related to the partial dissociation of the Ru-CI bond, which increases with the basicity of the phosphine attached to the metal.

L)(CO)[P(OPh)

3

1

and Rh(GL)[P(OPh)

3

1

2

A. GUTIERREZ-ALONSO and L. BALLESTER REVENTOS,

3.

ELECTROC HEMISTRY

Electrocatalytic Properties of Ultrafine

Platinum Particles for Oxidation of

Methanol and Formic Acid

in

Aqueous

Solutions

and Y . TAKASU, Electrochim. Acta, 1991, 36, (5/6),

The effect of size of ultrafime Pt particles prepared by vacuum evaporation onto a glassy C rod, on the elec- trochemical oxidation of MeOH and HCOOH acid was examined by cyclic voltamwtry. The specific ac- tivity for the oxidation of MeOH decreased by decreasing the Pt particle size, whereas that of the HCOOH acid increased as the particle size decreased.

XPS Analysis of Amorphous Ni-Nb-Sn-Pt

Alloy Catalysts for Electro-Oxidation of

Formaldehyde

Sci. Eng., 1991, A134, 1070-1073

Amorphous Ni-40Nb-xSn-(3-x)F't alloy ribbons were prepared and used for the electrmxidation of HCHO after surface activation by HF. Maximum activity was observed at

-

0.4 at.%Sn.

X P S

revealed that the surface layer was rich in Pt and deficient in Ni, but that the surface concentration decreased continuously with increasing Sn content.

Electrochemical Properties of Ultra-Fine

Palladium Particles for Adsorption and

Absorption of Hydrogen in an

Aqueous

HClO, Solution

K. YAHIKOZAWA, Y. FUJII, Y. MATSUDA, K. NISHIMURA

973-978

A. KAWASHIMA, K. ASAMI and K. HASHIMOTO, Maoter.

N . TATEISHI, K. YAHIKOZAWA, K. NISHIMURA, M. SUZUKI, Y. IWANAGA, M. WATANABE, E. ENAMI, Y.

(7), 1235-1240

MATSUDA and Y. T ~ UElectrochim. Acta, , 1991,36,

Ultra-fine Pd particles were prepared by vacuum evaporation onto a plane of glassy C

(GC)

rod. Their diameters were estimated to be 2-10 nm by SEM. Properties of Pd/GC electrodes in H adsorption and absorption were characterised by cyclic voltammetry. Adsorption strength of H species on the Pd particles of Pd/GC did not depend on the particle size, whereas amounts of the adsorbed H species and the absorbed ones into the Pd particles were dependent.

Electrochemical Hydrogen lnsertion into

Palladium and Palladium-Nickel

Thin

Films

tmchim. Acta, 1991, 36, (7), 1203-1208

A generator-detector mode with the rotating ring- disk electrode was used to determine the difference between Pd and Pt electrode behaviour and the origin of the larger overpotentials at Pd-H evolving cathodes. The use of thin f h (1-10 pm) Pd disk electrodes has allowed full H or D charging of the metal phase in short times. This electrode system enables measurements of the H uptake in PdH, f h s to be made, with PdH,.,, being the maximum.

J. M. ROSAMILIA, J. A. ABYS and B. MILLER, Elec-

The Role

of the Electrolyte

Anion

in

Anodic Dissolution of the Pd(100)

Surface

T. SOLOMUN, J. Electroanal. Chem. InteflaCial Elec- tmchem., 1991, 302, (1 and 2), 31-46

Electrodissolution of Pd during its electro-oxidation in H,SO, was studied by

XPS,

LEED, cyclic voltammetry and IR spectroscopy. At the beginning of the surface electro-oxidation reaction Pd species, showing a rather large shift of the (34 core levels (2.5 eV towards the high binding-energy site), were elec- trogenerated at the surface in H,SO,, but not in HCIO, electrolyte. Their concentration was directly related to the anion surface concentration. A surface complex of the type PdO(HS0,) acted as a precursor in the formation of highly soluble PdSO, .

Adsorption Properties of

an

Iridium

Oxide Electrode: A Thermodynamic

Approach

0. A. PETRII and A. VITIN'SH, Elektdhimiya, 1991, 27, (4), 461-476

Adsorption properties of electrodes made of thermal- ly prepared IrOx, deposited on Ti layers were studied by potentiometric titration during isoelectric conditions in 0.1 M KNO, . A strong dependence of the acid-oxidation properties of the IrO,/Ti electrode on the stoichiometry of the active oxidation surface, characterised by the value of the e l e c t d e potential at the determined pH of the solution, was observed.

Characterization of DSA-Type Oxygen

Evolving Electrodes. Choice of Base

Metal

HINDEN, T h e m h i m . Acta, 1991, 176, 31-47 The effect of the base metals: Ti, Ta, Zr, Nb and some of their alloys, on the performance of Ir02- Ta 0 coated DSA-type 0 -evolving electrodes was investigated. The thermal behaviour and 0 affinity sequence of the metals in relation to the electrode preparation procedure were determined ther- mogravimetrically

.

The chemical and electrochemical stability of the base metal was directly related, through the wear mechanism, to the savice life of the electrode, measured in 30% H z SO, at 8OoC and 750 mA/crnZ. Ta-based electrodes have the longest ser- vice life of 1700 h, compared to 120 h for Ti-based electrodes.

Morphological and Microstructural Study

of the TinrO, -Ta 0 Electrode: Effect of

the Preparation Temperature

Electrochim. Acta, 1991, 36, (5/6), 991-998

Morphological and structural examinations of dimen- sionally stable electrode coatings (Ir02-Taz0,) (70:30 mol %) show that at moderate fumg tempexatures,

-

55OOC, separation of phases occurs with the formation of agglomerates of I r 0 2 crystals and amorphous Ta,O,. At -750OC both crystalline IrO, and Ta,O, are present.

G. P. VERCESI, J. ROLEWIW, C. COMNINELLIS and J.

G. P . VERCESI, J.-Y. W I N and C. COMNINELLIS,

Reaction between [(TPP)Ru(CO)l'- and

Methyl Iodide. Evidence for Formation of

a

Ruthenium(I1) Carbonyl Methylated

Tetraphenylchlorin Derivative

WISH, Inorg. Chem., 1991, 30, (8), 1957-1960 This study provides the first example for elec- trogeneration of a methylated chlorin. The reaction between [(TPP)Ru(CO)l'-, where TPP is the dia- nion of tetraphenylporphyrin, and CH,I differs from that of reduced

Co,

Fe, and Rh porphyrins because a stable o-bonded CHI derivative is not formed. Y. J. DENG, X. H. MU, P. TAGLIATESTA and K. M.

PHOTOCONVERSION

Photocatalytic Dehydrogenation

of

Pen-

tane in the Presence of RhCl(CO)(PR,),

(R

=

CH,, iso-C,H, and n-C,H9)

CHIKOVA, E. A . GRIGORYAN, A. 0. BORISOV and v. D. MAKHAEV, Kinet. Katal., 1991, 32, (2), 473-477 Studies of the effect of the nature of phosphine ligands on the activity and selectivity of the process during dehydrogenation of p t a n e solutions in the presence of RhCI(CO)(PR,), (R = CHI, iso-C,H, and n-C, H,) were performed in the IR spectra region on >270nm light exposure.

Tris(2,2 '-bipyridine)

Ruthenium(I1)

Complex by

Viologens

m

Anionic

Micellar and Polyelectrolyte Solutions:

Variation with Alkyl Chain of Viologens

J. w. PARK, M. Y . SUK and B.-T. AHN, Bull. Korean Chem. Soc., 1990, 11, (6), 552-557

Luminescence quenching reactions of photoexcited

tris(2,2 '-bipyridine) Ru(I1) complex cation, Ru(bpy) +

,

by dialkylviologens were studied in Na

dodecyl sulphate (SDS), poly(styrenesu1phonate) (PSS) and poly(vinylsu1phonate) (WS) solutions. The relative quenching rate varies widely with the microheterogeneous media used. The highest quen- ching rate was observed for methyldodecylviologen in homogeneous aqueous medium, dibenzylviologen in SDS and PVS and dimethylviologen in PSS.

Preparation and Photochemical Charac-

teristics of the Copolymer Pendant

Tris(2,2

'-bipyridine)Ruthenium-Mercury

[Ru(bpy), ,+.Hg2C16 Complex

R . RAMARAJ, A. K I M and M. KANEKO, J . Photochem. Photobwl. A : Chem., 1991, 56, (2-3), 287-293 The title Ru-Hg copolymer pendant complex was prepared and characterised by IR, visible absorption and emission spectroscopies and emission decay measurements. The solubility and excited state lifetime both in DMF solution and the film state were quite different from those of the low molecular Ru- Hg complex reported before. The emission from the excited ply-Ru-Hg was much longer than that from the poly-Ru in DMF solution.

N . K. KHANNANOV, E. A. KOCHETKOVA, G. N. MEN-

Luminescence

Quenching

of

APPARATUS AND TECHNIQUE

Preparation of

an

Oxygen Sensor Com-

posed of Tightly Stacked Membranel-

ElectrodelElectrolyte

K. KATAKURA, A. NOMA, z. OGUMI and

z.

TAKEHARA, Denki Kugaku, 1991, 58, (12), 1184-1189

An amperometric 0 sensor operating at room temperature was constructed using a porous Pt cathode on Nafion and perfluoropolymer as the 0 transport limiting membrane, which was directly bound on the cathode by plasma polymerisation. The 0 reduction current increased with increasing 0 con- centration, from 0 to 30 ppm. A microsized 0 sensor can be prepared in principle.

Kinetics of Oxygen Interaction with

PtKeO, Sensors: Application

of a New

Pressure Modulation Spectroscopy

A . DUBBE, H. D. WIEMHOFER, K. D. SCHIERBAUM and w. G ~ P E L , Sens. Actuators B, 1991,4, (1 & 2), 23-28 A new method for characterisation of the dynamic response of the electrode potential upon sinusoidal 0, partial-pressure variations, and its powerful ap- plication was demonstrated in a study of the kinetics of different Pt electrodes on GO-doped G O , elec- trolytes. Surface diffusion effects play a major part in the overall kinetics of the 0, response of their microstructures. Gradients of the 0

,

surface concen- tration were analysed in an independent spec- troscopic study on CeO, samples with Pt contacts.

A Laser Power Detector Built Up by Ap-

plication of Thick-Film Technology

J. NICOLICS and w. S M ~ A N A , Sens. Actuators A , 1991,

A structure for a laser power detector using thick-film technology was developed. The incident laser radia- tion caused a heat flow in a metal plate where the resultant temperature differences, detected by thick- fdm Pt sensor elements, acted as a measure of the laser power. The sensitivity of the sensor was calculated and experimentally determined. The in- dicated laser power was independent of the radial in- tensity distribution of the laser beam.

Schottky-Barrier and Conductivity Gas

Sensors Based upon PdISnO, and

PtiTiO,

K. D. SCHIERBAUM, u. K. KIRNER, J . F. GEIGER and w . &PEL, Sens. Actuators B, 1991, 4, (1& 2), 87-94 Electronic conductivity, mixed conductivity and Schottky-barrier sensors based on SnO, and TiO, modified by Pt and Pd metals can be used to detect CO, CH,, H , and 0, gases. Sensor response signals result from changes in surface and bulk conduc- tivities or in Schottky-barrier heights, which are measured using different geometric arrangements of Pt or Pd metal contacts. Studies showed that reliable sensor properties can only be achieved either by for- ming stable metal/oxide interfaces or by adjusting a stable dopant distribution.

25, (1-3), 235-239

HETEROGENEOUS CATALYSIS

Hydrogenation of Olefms

on

Platinum

c.-M. PRADIER and Y. BERTHIER,

3. Catal.,

1991,129,

The hydrogenation of buta-1,3-diene and isoprene was studied on three Pt planes. The reaction for buta- diene was structure sensitive, with an increase in the turnover frequency by a factor of 5 from the denser to the rougher planes: Pt(111)<Pt(100)<Pt(110). There is a remarkable correlation between variations of the reaction orders and changes in the selectivity. The surface works as a bi-functional catalyst: hydrogenation and exchange seem not to occur upon the same kind of sites. The catalytic surfaces works with a HC layer present, not identical on the three

studied surfaces.

Hydrocracking and Isomerization

of n-

Octane and 2,2 ,.l-Trimethylpentane over

a Platinum/Alumina-Pillared Clay

c . DOBLIN, J. F. MATHEWS and T. w. TURNEY, Appl.

The hydrocracking and isomerisation of n-octane and 2,2,4trimethylpentane

(TMP)

over an AlzO,- pillared clay (A-PILC), containing 0.16%

Pt

were studied in a microreactor at atmospheric pressure, at 175-325OC and weight hourly space velocity of 0.48-7.5h. The Pt/A-PILC catalyst underwent an initial stabilisation period of -30 h, resulting in changes in the physical structure of the catalyst. The catalyst showed ideal hydrocracking behaviour for nC, giving high isomerisation yields, with a max- imum isomer yield of 64% at 80% conversion. For hydrocracking 2,2,4-TMP, the major reaction was A type &scission giving a product with >96% isobutane at all conversions.

Platinum-Tin Complexing and Its Ap-

plication

to

Catalysis

Catalysts for the dehydrogenation of long chain

alkanes were prepared by impregnating a y-Al,O, support with a

[PtCl,(SncI,),l2

-

complex using H,PtCl, and SnCl, solutions in an acidic medium. The catalytic performance of the catalyst prepared by the complex method was remarkably improved com- pared to the Pt-Sn dehydrogenation catalyst prepared by non-complex methods.

Infrared Study

of

CO Adsorption

on

Pt-

Rh/A12 0 Catalysts

Faraday

Trans.,

1991, 87, (9), 1479-1483

Studies of CO adsorption on Pt/Al,O,, Rh/Al,O, and

Pt-Rh/Al,O,,

at 303-573 K were performed by FTIR spectroxopy. Catalysts containing Rh were precalcined at either 673 K or 873 K before reduction in H, and exposure to CO. The intensities of IR bands due to gem-dicarbonyl and linear carbonyl species were a function of both the precalcination temperature and the temperature of contact with CO. (2), 356-367

Catal., 1991, 70, (2), 197-212

L. Y. JIN, Apfd. catd., 1991, 72, (I), 33-38

J. A. ANDERSON and C. H. ROCHESTER, J. Chem. SOC.,

Improved Higher Alcohols Selectivity

in

Syngas Reaction (CO

+

H2) over

Platinum Deposited

on

Rare

Earth

Ox-

ides of the Fluorite Structure

J. EL FALLAH, F. LE NORMAND, s. BOUJANA and A. KIENNEMANN, Eur.

3.

Solid Stnte Inorg. Chem., 1991,

The effect of rare earth oxide as support on the reac- tivity of

Pt

in syngas conversions was tested. A chain growth process, giving up to C, alcohols is observed on Pt deposited on rare

earth

oxides of the fluorite

type(CeO,,Pr,O,,,Tb,O,).Thisremarkableselec-

tivity is explained by the creation of anionic vacancies at the interface of the metallic particle and the sup- port, similar to that previously reported for Pd. On

such catalytic sites both the dissociation of the CO molecule and the chain growth process occurs. F'raseodymia gives the most effective support for im- proved higher alcohol formation.

Hydrogenation of Acetylene over

Various

Group ,VnI Metals: Effect of Particle Size

and Carbonaceous Deposits

A. J. DEN HARTOG, M. DENG, F. JONGERIUS and

v.

Supported Pt, Pd, Rh and Ir catalysts were studied for the hydrogenation of CzH2 and the effect of the particle size on this reaction was established. Rh and Ir show effects that can most probably be explained by the influence of the particle size on the in- termediate of direct hydrogenation to C,H, while for Pt and Pd the effect of deposition of carbonaceous layers prevails.

Gas-Phase Hydrogenation

of Styrenes by

Transfer over Pd/AlPO, Catalysts

MARINAS and M. E. SEMPERE, React. Kinet. catal.

Lett., 1991, 43, (11, 1-6

The hydrogenation of styrene and a-methylstyrene over Pd/AlPO,, using cyclohexene as donor is reported. The catalysts were activated in the pulse reactor and retained H, which was subsequently used to reduce the olefm. The amount of ethylbenzene produced from the styrene can be ac- counted for by H transferred by cyclohexene and H stored over the catalyst surface during treatment with cyclohexene, intended to reduce the impregnating metal salt.

Kinetics of Liquid-Phase Hydrogenation

of

Hexene-1

on

Palladium Sulphide

Catalyst

L.

v.

SHALIMOVA, A. D. BERENTS, s. v.

wwv

and 0.

v. CHEBAEVA, Kinet. Katal., 1991, 32, (I), 55-59 Studies of the kinetic dependence of hexene-1 hydrogenation in benzene solution in the liquid phase in a flow system over a Pd sulphide/Al,O, catalyst were performed at 50-150°C and

H I

pressure of

5 MPa. Intermediate adsorption stages were calculated and an equation for the rate of change of the concentrations of basic components was obtained.

28, Suppl., 433-436

PoNEc,

J.

Mol. Catal., 1990, 60, (l), 99-108

M. A. ARAhiENDfA, V. BORAU, C. J I M k N E Z , 1. M.

A

New

Palladium-Catalyzed Coupling

Reaction

of

Vinyl and Allylic Triflates

with Pyrimidine Nucleoeides

Vinyl trifluoromethane sulphonates (triflates) form Pd intermediates which react with pyrimidine nucleosides to yield C-5 alkyl substituted nucleosides, after hydrogenation of the vinyk coupling products with H, and Pd/C in MeOH under mild conditions. The reaction is a general one since mono-, disubstituted and cyclic vinylic triflates give high yields of the corresponding C-5 alkyl-substituted nucleoside.

Oxidation State of the Surface of

Palladium

in

the Catalytic Combustion of

Hydrogen

M. G. JONES, T. G. NEVELL, R. J. EWEN and c. L.

HONEYBOURNE, Appl. Catal., 1991, 70, (2), 277-286 The activity of supported Pd catalysts for the oxida- tion of H, was studied at 80-500°C using a microcalorimetric technique and XPS. The reaction involved a surface layer of 0,

,

and was inhibited by adsorbed H,O. Palladium(I1) oxide was formed on the surface of metallic Pd under 0, at 45OOC. Heating in H, at 25OOC reduced this surface layer and produced deactivated catalyst but the activity was subsequently restored by exposure to 0,.

Methylcyclopentane Conversion Catalysis

by

Zeolite

Encaged Palladium Clusters

and Palladium-Proton Adducts

M. E. HASAN, Can.

3.

Chem., 1991,69, (2), 198-200

X. BAI and W. M. H. SACHTLER,

3.

Caul., 1991, 129,

(l), 121-129

The conversion of methylcyclopentane (MCP) was studied over the prototype catalysts HY, Pd/HY, PdNaHY and proton-free Pd/NaY. Ring opening of MCP to hexane isomers was catalysed by Pd, clusters, but ring enlargement (RE) of MCP to cyclohexane and benzene required metal sites and protons. The RE of MCP was catalysed by the “electrondeficient” [Pd,HI + adducts more effec- tively than by separate metal and acid sites. The catalysts containing Pd and protons in the same zeolite cavity, were dramatically more active for RE than a mixture of HY and proton-free PdNaY.

Direct and Indirect Promotion

of

P d N

and

CaZ + Ions

x. BAI, z. ZHANG and w. M. H. SACHTLER, Appl. Catal., 1991, 72, (l), 165-178

Studies of Pd in Nay or Cay zeolites tested as catalysts for HC conversion reactions showed that the pre-exchanged Caz + cations in Y zeolite increase the

concentration of [Pd,HI+ adducts and subsequently improve the rate and stability of the catalyst for ring enlargement, while decreasing the ring opening rate of methylcyclopentane. The results suggest a direct interaction of the charge compensating ions (Ca’ + or Na+) with Pd particles and an indirect effect viz. by affecting the concentration of electron-deficient Pd- proton-adducts.

Liquid-Phase Oxidation

of

Propylene on

Supported

Palladium

Mono-

and

Bimetallic Catalysts

in

Acetic Acid

A. I. BORONIN and E. M. MOROZ, Kinet. Katal., 1991,

Studies of the oxidation of propylene and propylene glycol and their acetates in acetic acid solutions, in HNO, were performed in the presence of heterogeneous Pd, Pd-Pt and Pd-Rh catalysts deposited on C, S O , and TiO, supports. The Pd-Pt catalysts were found to be most resistant to deactiva- tion in the presence of reactive S. One of the reasons for deactivation of the catalysts was the formation of cyanide metal complexes on the support surfaces.

Effect of Promoters on the

Catalytic Ac-

tivity

of

Rh,(CO),2/TiOz

for

CO

Hydrogenation

Y. CHEN, J. DU, Y. CHEN and

z.

DU,

3.

Fuel Chem. Technol., 1991, 19, (l), 1-7

The activities for CO hydrogenation in a continuous flow microreactor of promoted Rh catalysts were in the order Rh, N-TiO, >Rh, /Ti0

,

>Rh, /Mg-TiO,

.

On the Rh,N-TiO, catalyst CO was completely con- verted to CH, at 200OC, while for CO hydrogenation at various H,:CO ratios on Rh,/Mg-TiO,, CO, was always present in the product. Catalyst dispersions were determined by H , - 0 , titrations. A high H:M ratio occurred for Rh,(CO),,N,O,-TiO,, which was caused by the low temperature reduction of

V,O,

catalysed by metallic Rh. The H:Rh ratio was in the same order as their activities. Only a twin CO band without linear or bridged CO was found during temperature programmed adsorption and desorption of

co.

HCN Synthesis from NH, and CH,

on

Rh

and

Ir

M. P. s u k ~ z and D. G. L~FFLER, React. Kinet. catal. Lett., 1991, 43, (l), 195-199

The synthesis of hydrocyanic acid from CH, and NH, on Rh and Ir wires was studied at temperatures between 1200 and 1500 K, at a pressure of one at- mosphere. Activation energies and pre-exponential factors are reported.

The Effect of CeO Support upon Activity

and Selectivity of Ru and Co Fischer

Tropsch Catalysts

M. WINTERBOTTOM, Eur. J . solid state Inorg. Chem.,

1991, 28, (2), 453-456

5% Ru and Co catalysts supported on G O , were prepared by impregnation and characterised by TPR. Their catalytic activities and selectivities were tested in H, and

CO

reactions and compared with a Ru/SiO, catalyst in the range 1-9 atm and 260OC. RdSiO, and Co/SiO, catalysts gave CH, only at 1 atm and 70% CH, at 9 atm, while Ru/GO, and

Co/CeO, gave significantly smaller quantities (20-80%) of CH, over the same pressure range. A. V. KARANDIN, E. V. GUSEVSXAYA, V. A. LIKHOLOBOV,

32, (2), 367-374

A. F. Y. AL-SHAMhtARY, I. T. CAGA, A. Y. TATA and J.

HOMOGENEOUS CATALYSIS

Substitution of Halogen

in

Vinylbromide

and Reduction of Vinylhalogenides

to

Ethylene

in

the Syetem PtO-NaI-

HClO4-H

2

0

S. A. MITCHENKO, V. V. ZAMASHCHIKOV and A. A. SHUBIN, Kinet. Katal., 1991, 32, (2), 343-345 Studies of the kinetics of the NaI (2.5 M)- HClO4(O-2.5 M)-H20 system at 8OoC catalysed by Pt(I1) (0.004-0.06 M) showed the substitution of B

by iodine in vinylbromide (RBr). When tHCl0,I

>

0, parallel substitution of RBr occurred by reduction to ethylene, and in acid solutions the formed vinyliodide also reacted with Pt(II) yielding ethylene. A phase mechanism is provided which includes oxidative addition of vinylhalogenide to Pt(I1) with the intermediate formation of a-vinyl Pt(IV) complexes.

’

H-NMR-Study of Deuterium Exchange

in Styrene

under

the Conditions of

Hydrocarboxylation

Catalysed

by

Palladium Complexes

YU. G. NOSKOV, N. A. NOVIKOV, M. I. TEREKHOVA and E.

s.

PETROV, Kinet. Katal., 1991, 32, (2), 331-335 A study of the hydrocarboxylation of styrene catalys- ed by PdCI,(Ph,P), at 1 10°C and CO pressure of 2.0

MPa by the deuterium exchange method showed that terminal protons of unreacted substrate were noticeably substituted by D, but that proton ex- change in the a-position of phenyl groups was not observed. When the pressure was decreased and SnCl, was added, proton exchange occurred in both

C atoms of the vinyl styrene group.

Homogeneous Catalytic Hydrogenation

of

Alkenes by Zero-Valent Palladium

Complexes

of

cis-Fiued

Dinitrogen

Ligands

R. VAN ASSELT and C. J. ELSEVIER,

3. MOl. Catd.,

1991, 65, (3), L13-Ll9

Zero-valent Pd complexes (DIAN)Pd(olefm) contain- ing a cis-fmed dinitrogen ligand (DIAN)

(N,N’-diaryl-diiminmenaphthene) are active as catalysts in the homogeneous hydrogenation of various unsaturated substrates. The title hydrogena- tion can be performed under mild conditions (THF,

2OoC and 1-1.5 bar of H, pressure). This results in complete conversion of various substituted alkenes to the corresponding alkanes.

Palladium-Catalyzed Coupling Reactione

of

Trifluoroacetimidoyl Iodides with

Olefins and 1-Alkynes

K. ~ A M and A H. WATANABE, Tmahedtim Lett.,

Pd-catalysed coupling of trifluoroacetimidoyl iodides with olefins and also 1-alkpes produced vifluoromethylated a, &unsaturated imines which were transformed into N heterocycles bearing CF

,

-

group. N-aryl vifluoroacetimidoyl iodides underwent smooth palladation with Pd

,

(dba)

,

.CHU 3 .

1991, 32, (ll), 1459-1462

Palladium Catalysed Tandem Cyclieation-

Anion

Capture Processes Initiated by

Alkyl- and ?r-Allyl-Palladium Species

R. GRIGG,

s.

SUKIRTHALINGAM and

v.

SRIDHARAN, Tetrahedron Len., 1991, 32, (22), 2545-2548 Palladium catalysed tandem cyclisation-anion capture processes initiated by oxidative addition of benzylic or allylic halides or acetates to Pd(0) occurred regio- and stereo-specifically in good yield. The benzylic halide reacted with Na tetraphenylborate in the presence of Pd(0) to yield 69 % of the organic species. Examples of “anion” capture involving formate (H-), and organo- Sn, -Zn and

-B

species are described.

Palladium-Catalyzed

@-Vinylation of

Vinyl Acetate with

En01 Triflates.

An

Entry

to

1 -Acetoxy-1

,

3-Dienes

P. G. CIATTINI, E. MORERA and G. ORTAR, Tetrahedron

Reaction of enol viflates with vinyl acetate in the presence of Pd(0Ac)

,

catalyst produced 1-acetoxy-1, 3-dienes as the major products in 40-79% isolated yields. Formation of the 8-vinylated product was si@icantly favoured. The results showed that steric effects prevail over electronic factors in these organo- Pd reactions, in contrast to the corresponding reac- tions with enol ethers where electronic factors predominate.

Synthesie of Carboxylic

and

Phosphonic

a-Amino

Acids Using Palladium Allylic

Alkylation

Lett., 1991, 32, (12), 1579-1582

J. P. GENET, S. JUGE, I. BESNIER, J. UZIEL, D. FERROUD, N. KARDOS, S. ACHI, J. RUIZ-MONIES and S.

78 1-786

THoRIMBERT, Bull. sot. Chim. Fr., 1990, 12, (6),

Schiff bases derived h m glycine and alanine esters were alkylated in the presence of Pd catalysts under neutral or basic conditions using dylic carbonates, esters or halides. Asymmetric Pd allylic alkylation of the benzophenone imine glycine methyl ester using Pd(OAc),

+

(+)DIOP was achieved with up to 70% ee. After hydrolysis, several functionalised a- aminoacids-enzyme inhibitors-were obtained.

Cationic

PaUadium(II)-Diphosphine

Com-

plexes

as

Catalysts

for

the Carbonylation

of Alkenes to Ketones

Chem. Soc., Chem. Commun., 1991, (6), 421-423 Cationic Pd complexes of the type [(dppp)Pd (solvent),ltXI,, where X = a non or weakly co-ordinating anion and dppp = 1,3-bis(diphenyl- phosphino)propane, are active catalysts for the carbonylation to ketones, for the selective formation of E-1,5-diphenylpent-l-en-3-one from styrene. In the presence of water and depending on the acidity conditions dimerisation to the much less catalytically active [(dppp)Pd(p-OH),Pd(dppp)IX, takes place, the structure of which has been determined by X-ray crystallography.

C. PISANO, G. CONSIGLIO, A. SIRONf and M. MORET,

3.