Platinum Metals Review

UK ISSN 0032-1400

PLATINUM METALS REVIEW

A quarterly survey of research on the platinum metals and of developments in their application in industry

VOL. 35 JANUARY 1991 NO. 1

Contents

Platinum in High Temperature Superconductor Technology 2 Polymetallic Activation 10 Advances in the Study of Platinum Group Elements 16

A Means to a Cleaner Environment 17 Quasicrystals in Rapidly Solidified Alloys 21 Grove Fuel Cell Symposium 21 The Photogeneration of Hydrogen 22 Cleavage in Iridium Crystals 23 Metal-Hydrogen Systems 24 Palladium Membrane Reactors 27 Isomers of Platinum(I1) and Palladium(1I) Complexes 28 Magneto-Optical Recording Materials 31 Osmium and Ruthenium Complexes 31 Abstracts 32 New Patents 47

Communications should be addressed to The Editor, Platinum Metals Review Johnson Matthey Public Limited Company, Hatton Garden, London EClN 8EE Platinum in High Temperature Superconductor Technology LITERATURE SURVEY SUGGESTS POTENTIAL USES By E. F. Maher Johnson Matthey Technology Centre

High temperature superconducting oxides are being subjected to intensive investigation, designed to establish the basic mechanisms governing their superconductivity and to enable their electrical and mechanical properties to be optimised and commercial applications developed. Chemical composition, crystallography, microstructure and the concentration of point defects are all factors that have a crucial bearing on superconductivity. Progress in fabrication and thermal processing would elevate these high temperature superconducting oxides from laboratory curiosities to a position where widespread commercial use could be envisaged. Much has already been published on the use of the platinum group metals with the new superconductors. This article has been compiled from a search of the literature and indicates some of the applications that are, or could be, of commercial significance.

The phenomenon of superconductivity, that Superconductivity is dependent upon many is the total absence of electrical resistance in a factors including chemical composition, material when it is maintained below a critical crystallography, microstructure and point temperature, has found limited commercial ap- defect concentration, and for virtually any application. For example, body scanners used for plication the stability of the superconducting medical imaging make use of conventional property is crucially important. The supercon- niobium-tin superconductors. However the re- ducting phase in the new materials is thought to quirement for liquid helium cryogenic cooling be inherently thermodynamicallyunstable, and systems, which hold the temperature below the thus any thermal treatment will play a vital critical temperature, restricts the use of conven- role, particularly for power applications where tional low temperature superconductors. the material would be used in bulk form. Applications for superconducting materials The published literature on high critical would be expected to increase very significantly temperature superconducting oxides amounts if their critical temperatures were higher, and to tens of thousands of papers and patents, therefore easier to achieve. Progress towards many referring to the use of platinum group this is being made following the discovery and metals. Indeed, over one hundred papqrs have development of so-called high temperature been published specifically on the use of noble superconductors. These are complex oxide metals with the new superconductors, mostly materials that have critical temperatures above on aspects of high temperature processing. One the boiling point of liquid nitrogen (77K). The critical factor for the successful production of processing of these materials, in order to im- high temperature superconductors is the oxy- prove both their mechanical and electrical pro- gen defect concentration. This is neither easy perties, and hence their performance, is being to measure nor control. The simple exclusion of studied in laboratories all over the world. oxygen during processing is not sufficient to

Platinum Metals Rev., 1991, 35, (l), 2-9 2 Principal Uses of Platinum in Superconductivity

Containers crucibles, substrates, coated substrates, pipes Wires wire substrates, grids as substrates, barrier layers in fabricating YBCO wires Ceramic processing powder as a densifying agent during sintering Electrochemical electrodes for characterisation, synthesis and oxygen control Electrical contacts usually sputter deposited, also thick film Composites barrier layers at interfaces of composite structures:. coatings on YBCO fibres in a matrix, fibres coated with YBCO in a matrix, laminated structures Thin films/devices barrier layers allowing use of inexpensive and common substrates, e.g. Si barrier layers for YBCO orientation/ texturing

Chemical studies compatibility studies with superconductors

control the oxygen defects, which from ther- forward in the development of superconduc- modynamic considerations must exist in the tors. Some applications for conventional superconducting oxide materials; but a reduc- superconductors-such as high power tion in the number of extraneous perturbing in- magnets- were already developed and com- fluences on the oxygen content must contribute mercially viable, despite needing liquid helium to improved materials. Thus the use of noble cooling. Until 1986 the critical temperature had metals as containers, &sion barriers and risen by only about 2OoC since the first observa- electrical contacts, for example, can assist in tions of superconductivitywere made by Onnes improving process control. in 1911 (1). Within weeks of the disclosure by The driving force behind research and Bednon and Muller of a new class of supercon- development of these superconducting ducting material based on copper oxides con- materials is their potential application in areas taining barium and rare earth elements (2), such as high power magnets and high speed critical temperatures as high as 100 K were be- switches for computers. At this early stage it is ing reported. For nearly two years a new high not clear which application areas will emerge as temperature superconducting material or the dominant ones, and hence the specific variant was being reported weekly, but relative- technologies required cannot yet be identified. ly little progress was made in understanding the However by making comparisons with the phenomenon. In some respects, the classical semiconductor industry it may be possible to superconductivity theory (3) is inadequate to make some general predictions on how the describe the new superconductors, but even technology and application areas will develop, now there is no universally accepted replace- and the roles which platinum will play. ment. Certain parts of the theory, including Cooper pairs of charge carriers, are retained by Overview of High Temperature most newer theories. Superconductivity The main drawback arises when attempting The advent in 1987 of the new high to explain the pairing interaction and how it can temperature superconducting materials, such survive to much higher temperatures than the as YBaCuO (YBCO), was hailed as a major step classical phonon coupling mechanism allows.

Platinum Metals Rev., 1991, 35, (1) 3 Frantic formulation, patenting and publicis- sheaths around niobium-tin wire, was the key ing of new combinations of materials with to establishmg the very high critical currents superconducting properties at temperatures now possible in conventional superconductors. above 77 K has now been replaced by an alter- Successful commercialisation of many new native approach driven by potential applica- materials has generally depended to a large tions. Investigators were initially obsessed with extent on the recognition of the role of in- raising the critical temperature ever higher, but homogeneities. In the broadest possible sense it became clear that once critical temperatures we can regard any departure from perfect substantially above 77 K had been reached, fur- crystallinity, or a local departure from a single ther increases would not be of great phase amorphous material, as an inhomogen- significance, unless mom temperature could be eity . Deliberately introduced inhomogeneities achieved. Indeed, for most applications the have been used to enhance, and frequently most important parameter is the critical stabilise, the properties of materials. Thus current-the maximum current that can be at- while extremely high purity levels are essential tained until the self-induced magnetic flux for growing single crystal semiconducting associated with this current causes the system materials, regions deliberately doped with con- to become unstable and collapse due to interac- trolled amounts of impurities are used to pro- tions between nearby superconducting regions. duce, for example, the pn junctions which are The low critical currents observed were the ma- the basis of many electronic devices. The same jor barrier to commercialisation, and to a large is true of the mechanical properties: the work extent this is still the case, although progress hardening of metals leads to the interaction and has been made. The same was true of the entanglement of dislocations such that further classical Type I superconductors, for example deformation becomes progressively more dif- niobium, until Type I1 superconductors such as ficult. Similarly, the stabilisation of grain boun- niobium-tin, were discovered. daries in materials, such as ZGS platinum, The increase in critical current in Type I1 gives enhanced properties. Furthermore superconductors depends on the recognition of mechanical damage on the back of silicon the phenomenon of flux pinning. Essentially, wafers is used to “getter” unwanted impurities flux pinning ensures that the magnetic flux from the bulk material during quenching after associated with localised high current densities high temperature diffusion processes. of superconducting regions does not interact The role of inhomogeneitiesin the new super- with the flux due to neighbouring regions in conductors is also crucial to their operation, if such a way as to exceed the critical magnetic only because they are Type I1 superconductors. flux density and thereby collapse the supercon- Different thermal treatments of these materials ducting currents. A modem Type I1 supercon- give rise to widely differing microstructures ductor is an inhomogeneous system by design, and electrical properties. Inhomogeneities can with the discontinuities serving to stabilise the be regarded as real and possibly essential parts system, and effectively prevent instabilities of superconducting behaviour, rather than as from escalating and destroying the system via a unwanted artefacts. In fact the occurrence of domino effect. Clearly, any region which the higher critical temperatures seems to be becomes even momentarily non- associated with “dirty” specimens (4). superconducting will give rise to a Joule heating effect, which, if the heat is not conducted away Comparison of Semiconductor rapidly, will result in other regions exceeding and Superconductor Development the critical temperature, losing their supercon- Certain parallels can be drawn between the ductivity, and precipitating further thermal development of semiconductor materials, as a runaway. Thus the thermal design of supercon- part of the electronics industry (9,and the new ducting systems with, for example, copper superconductors which may help to predict

Platinum Metals Rev., 1991, 35, (1) 4 major applications for the latter, and identify there has been a massive upsurge in effort since technological goals that will have to be achieved 1987 when the new high temperature supercon- before commercialisation can take place. The ductors were discovered. new superconductors are generally semiconductors above the critical temperature, and Platinum in High Temperature their discovery was also driven by the same re- Superconductors quirement for high speed solid state switching. At temperatures as low as two millionths of a Another reason for comparing semiconduc- degree Kelvin and magnetic fields as low as two tors and superconductors is that the required milli Gauss, no superconductivitywas observed performance of the latter is only likely to be at- in platinum, palladium and rhodium, according tainable, at least for the forseeable future, using to a study in 1978 (6). However, a number of techniques which give very close control over alloys of platinum have been found to be super- material properties, such as crystallinity and conducting, such as UR (7) and MoPt (8), but chemical composition. Single crystal growth with one possible exception these have all been and thin film deposition are currently able to low temperature superconductors. The possible give higher performance characteristics than, exception is CUR, which a recent patent sug- for example, ceramic processing, and the gests is superconducting at temperatures as former techniques are more likely to be used in high as 200K (9)! This work has not been con- the first commercial applications. The semicon- firmed, however, and no other reference to it ductor industry is skilled in such matters and has been found in the literature. much information is available on the techniques Over 100 papers and patents have been for depositing thin films on single crystal published specifically mentioning platinum in substrates, and so on. connection with high temperature supercon- There are likely to be problems in processing ductivity in either the title or the abstract, and superconductors but, except for applications in addition many more papers refer to platinum needing bulk materials, the techniques used in and its uses in the text. These can be divided in- the electronics industry are immediately rele- to several main groups, in terms of: the final vant. This is also true of many of the analytical form of the superconducting materials, the methods, such as secondary ion mass spec- techniques used for production and the appli- troscopy and X-ray scanning auger cation areas. microanalysis, that are necessary to achieve the In this way, we can attempt to predict the ap- required control. Thus, there is not the same plication areas that may be commercially viable learning curve, which compensates for the fust, the form these superconducting materials greater complexity of chemical composition and will take, the materials processing technologies microstructure of the materials. Fortunately it which will be most relevant and fdywhat the appears that chemical purity of itself is not as uses of the platinum are likely to be. It is essential as it is with semiconductors. assumed here that a high level of activity relates to a market need, and that such activity is likely Growth in Literature on to lead to the first commercial products. Superconductors Superconductivitywas first reported in 191 1 Electrical Contacts (1). Coincidentally, the first element Onnes in- Good electrical contacts for superconductors vestigated was platinum, which does not ex- are of importance, since there is no point in hibit superconductivity. Now there are over having high critical currents if contact 46,000 publications on superconductors. Com- resistance precludes their use because of Joule mercial applications for the “old” supercon- heating effects. Platinum, gold and silver are ductors are still growing, mostly for the best materials for making contact to the YB- applications requiring high power magnets, but CO ceramics (10,lI), since other metallic films

Platinum Metals Rev., 1991, 35, (1) 5 interact with the oxide materials to produce (32). Studies of the chemical reactions of alloys with semiconducting behaviour. Such platinum group metals additions during sinter- contacts are usually sputter deposited, but can ing of YBCO have highlighted their importance also be formed by pressing (12). Platinum in high temperature processing of the supercon- powders and pastes have been successfully used ducting oxides, although an additional thermal for fabricating terminal electrodes to supercon- treatment is needed for optimum properties (33). ducting ceramics with high critical currents (1000 A/m2). As with semiconductors, ohmic Electrochemical Uses contacts are not the only ones of use. A In a number of publications electrochemistry platinum-aluminium alloy has been used to is specifically involved in the preparation or produce a tunnel junction on a Josephson junc- characterisation of superconducting material. tion single crystal YBCO device (13). Platinum electrodes are extensively used both for the synthesis of material (34,35) and during Containers its analysis by electrochemical techniques (36, An obvious use of platinum is as a contain- 37). Electrophoretic deposition on a roughened ment vessel during high temperature process- platinum substrate is reported (38) and various ing of oxide superconductors. Single crystals of superconducting articles have been fabricated these materials are frequently grown in by electrodeposition (39). platinum or iridium crucibles (14, 15, 16), There have been novel schemes for control- which are also used during the preparation of ling the oxygen content of the materials, even melts prior to tape casting and wire drawing during active service, using platinum electrodes operations (17). Oxide powders have been and solid state electrolytes, which allow sintered on platinum substrates (18) or occa- transport and control of oxygen ions. For exam- sionally in platinum pipes, foils and capsules ple hot isostatic pressing in a partial pressure of (19-25), and sometimes the powders are quen- oxygen (with electrically biased electrodes to ched on platinum plates (26). Clearly the high control oxygen migration) has produced a melting points, general chemical stability and mechanically strong superconductor (40). A non-magnetic qualities of the platinum group similar process has been reported to produce a metals are ideally suited to thermal processing thin film superconductor device (41). in oxidising environments. Containers made from materials other than platinum metals are Wires used, frequently with a platinum coating (27). Frequent use is made of platinum wires during the processing of the oxide superconduc- Ceramic Processing tors, because of their stability at high In addition to containers and substrates, temperatures and their resistance to oxidation. there is another potentially significant use for On passing platinum wires through a melt of platinum. A number of reports refer to the use oxide materials, superconducting coatings are of platinum powder as a densifying agent dur- deposited (42-45); single crystal coatings of ing sintering, and for improving the mechanical superconducting material have also been pro- properties of the new superconductors (28-30). duced (46).Platinum grids have acted as sup- Indeed in one case (28), it is claimed that the ports for silicon nitride membranes prior to superconducting properties were enhanced deposition of YBCO for in-situ studies of ther- when finely divided platinum was used at a mal processing by electron microscopy (47). loading below 0.2 per cent. Platinum deposi- Ceramic composites of platinum wires and ox- tion on the oxide powders during thermal pro- ide superconductors have been fabricated (48, cessing is also reported (31). Fired 49). Fibres and ribbons of superconducting superconducting thick films have been pro- materials have been produced using the laser duced from solutions containing noble metals heated pedestal technique in combination with

Platinum Metals Rev., 1991, 35, (1) 6 platinum wire (50). Platinum has also been us- ducting oxide core. In one instance, the super- ed during the fabrication of wires of supercon- conducting core was surrounded by a glass envel- ducting material. Platinum and platinum alloy ope with a platinum barrier layer at the inter- substrates have been employed when powders face (72). A laminate structure with glass has or oxide layers have been melted by laser beam, also been used in the fabrication of a device (73). and subsequently solidified, so forming wires of superconducting material (5 1, 52). Supercon- Superconducting Thin Films for Devices ducting wires have also been fabricated from Probably the most commonly cited applica- mixes of oxides and noble metal powders (53) tion of platinum to date has been in connection or by lining a metal tube holding oxide powder with thin film electronic devices. Platinum has with silver, gold or platinum powders and then been used extensively in thin film form as a bar- sintering (54). Platinum barriers have been us- rier diffusion layer with three major objectives: ed around superconducting material contained (i) to maintain and control the oxygen in a copper sheath, when drawing wires (55, stoichiometry 56), and for cladding oxide preforms prior to (ii) to prevent chemical impurities diffusing wire drawing (57). Base metal wire with a from the substrate and contaminating the platinum diffusion barrier and a magnesium ox- superconducting layer ide intermediate layer has been a substrate for (iii) to orient the oxide film fabricating superconducting wire (58). crystdographically. Thus the commonly used substrates for devices, namely silicon, gallium Composites arsenide, sapphire, alumina and zirconia, have Superconducting composites comprising ox- all been used to support superconducting oxide ides, metallic and even glass components of films, very often with platinum buffer layers to vastly differing shapes and structures have minimise substrate interactions and provide received much attention. The most obvious orientation. composite structure, that of a container with For optimum superconducting properties, the superconducting oxide inside, has already the thin oxide film needs to be preferentially been referred to above. If the container remains aligned with the c-axis vertical. Platinum buffer in place as a sheath of metal after the contents films have been shown to have an orienting ef- have been sintered or processed, then the fect on the oxide film, even for amorphous resulting structure is clearly composite, with substrates such as alumina (74) or zirconia (75, the inner core being the superconducting com- 76). Although there have been many reports of ponent. Apart from the use of platinum barrier single crystal strontium titanate and layers for the processing of powder compacts magnesium oxide substrates being used, thin (59, 60), such diffusion barrier coatings have films of these materials on amorphous been used on the inside of base metal container substrates have also been used with platinum sheaths (61, 62). buffer layers to give superconducting oxide There have been a number of composites bas- films with high critical current density (77). ed on platinum fibres (48, 63, 64), and dis- Clearly, the practicality of electronic devices us- persed metal phases giving additional ing new superconductors will depend to a large mechanical strength (65,66). Platinum coatings extent on the film-substrate compatibility (78). on superconducting oxide fibres in a solder matrix have been proposed (67). Platinum Conclusions stabilisation layers for wire strips and tapes are High temperature superconductors show reported (68, 69), and there have been ex- every promise of being a commercial success amples of laminated structures, both planar despite their technical complexity. Potential (70) and concentric (71) with alternate layers of application areas, currently unsatisfied, oxide and metal alloys sumunding a supercon- abound. Academic institutions are striving

Platinum Metals Rev., 1991, 35, (1) 7 to unravel the complexities of materials and tions for the new superconductors, magnetic mechanisms and major companies are investing and optical detectors, satellite communications, substantially in research and development. magnetic screening, and magnedmotor Never have so many different technologies and technology may be among the first to be com- analytical techniques been applied to the mercialised. In terms of volume of platinum, understanding and advancement of a class of the use for superconductingmagnets is likely to materials. This is partly the result of the probe the dominant one, but critical current den- liferation of the new techniques and analytical sities will need to be substantially increased. instrumentation available, and partly because The use of thin films rather than wire in this ap- of the wide range of potential applications. plication warrants serious study, since in thin As with semiconductor materials, thermal films the critical currents can be much larger processing will be important and there are than in bulk material. numerous opportunities here for platinum to Electronic device applications, using thin assist in the achievement of the desired degree films, will probably be commercialised sooner of process control and material stability. The than high temperature superconducting exclusion of ferromagnetic materials during magnets. Specialised detectors (such as anten- processing is particularly important, as is con- nas) and superconducting interconnects on trolling oxygen migration. silicon are emerging as likely applications in the &h temperature superconductivity will short to medium term. In the long term, the have an impact on power applications, such as high speed switching application may compete for transportation and energy storage devices with advances in optical computing for the next (79). However, of the many potential applica- generation of electronic devices.

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Platinum Metalr Rev., 1991, 35, (1) 9 Polymetallic Activation A REVIEW OF THE INTERNATIONAL SYMPOSIUM By P. Braunstein Universitk Louis Pasteur, Laboratoire de Chimie de Coordination, Strasbourg, France

An International Symposium on Polymetallic Activation was held at the Universita di Parma, Italy, from the 13th to 15th September 1990, as part of a collaboration, supported by the European Commission, involving university laboratories at Strasbourg, Freiburg, Torino and Parma which carry out research on diverse aspects of polymetallic activation. An international panel of speakers presented plenary lectures giving the state of the art in their area, discussing and evaluating the results of this initiative and suggestingfuture actions aimed at developing and strengthening the linbbetween European laboratoriesperforming complementary research.

Polymetallic activation occupies a central posi- maceuticals, necessitates the development of more tion in organometallic and co-ordination complex and sophisticated catalysts of a tunable chemistry as it has frontiers with the synthesis nature. Molecular design and polymetallic activa- of new materials, with the study and applications tion thus become central themes. They need to of pure metals and metal particles, and brings an be studied in greater depth and in a enormous insight into how organic substrates multidisciplinary manner, using the different can interact with metal atoms and surfaces and techniques which are now available, but the costs undergo coupling/or decoupling reactions. The of which require optimum utilisation of the dynamics of clusters and of their ligands have also equipment and co-operative research. shown how uniquely an ensemble of atoms Professor A. J. Carty of the University of behave. The development of new catalytic pro- Waterloo, Ontario, Canada, presented the struc- cesses requires a fundamental understanding of tural chemistry, hydmgen activation and substitu- the elementary steps responsible for molecular tion reactions associated with a series of activation and transformation. The desired high tetranuclear clusters of ruthenium or osmium, chemo-, regio- and enantioselectivity, essential such as Ru,(CO),,(p,-PPh) and Ru,(CO),,oL- for the manufacture of fine chemicals and phar- PPh,) ,. The latter undergoes reversible

(C0)3

H2 (C0)3 RU(CO) 3 (C0)2 -- -- co P h2 ;AR/P P h2 (C0)3 (C0)2 Fig. 1 A reversible hydrogen activation of Ru, (CO) 11 (y.-PPh,) under photochemical conditions leads to the static tetrahedral 60-electron cluster Ru,(CO),,(y.-PPh,),(p-H),. This can be reversed under carbon monoxide

Platinum Metals Rev., 1991, 35, (l), 10-16 10 hydrogen activation under photochemical con- ditionsleadingto Ru,(CO),,(p-PPh,),(p-II),,a static tetrahedral 6O-electron cluster, see Figure 1. This net 4-electron change on metal-metal bond formation is reversed under an atmosphere of carbon monoxide (1). The role of the ligands (carbonyls, phosphido, phosphinidene .. .) was shown to be very important for the chemistry of these and related clusters, and the wide variety of structural types encountered in the regime of M, clusters hav- (C 0)3 ing a 62-64 electron count was illustrated by X- ray diffraction results. Fig. 2 A Ru4 butterfly cluster showing an interaction between a wing-tip metal atom The theoretical nature of the metal-metal bon- and the amide CO ding in clusters of low nuclearity was discussed by Dr. C. Mealli, C.N.R., Florence, Italy. A number of systems were presented where the (7 -C Me )Ta(PPh, )&-PPh ,) ,Rh( PMe ) adds distance between the metal atoms cannot be us- hydrogen acms the Ta = Rh double bond, formed as a sufficient criterion for deciding about the ing (q-CsMes)TaH(p-PPh,) RhH(PMe,) (3). bonding between the metals. Valuable pieces of Professor E. Sappa of the Universith di ToMo, information can howwer be obtained from the Italy, one of the partners in the European pro- nature and energy levels of the molecular orbitals gramme, presented reactions of homo- and involved. It was also emphasised that a negative heterometallic carbonyl clusters of iron, Overlap Population is not always in conflict with ruthenium and cobalt with functionalised alkynes the existence of a direct u bond (2). and dialkynes. The flexibility of the metal core The synthesis and co-operative reactivity of un- allows unusual bonding modes of the organic saturated heterobimetallic complexes containing fragments to occur and the resulting clusters often early and late metals zirconium, hafnium, display novel features of catalytic relevance (4). rhenium, and ruthenium, rhodium, iridium, For example, the nucleophilic reactivity of palladium, platinum, respectively, were de- acetylides co-ordinated to many metal centres scribed by Dr. R. T. Baker, E.I. Du Pont de represents a model of related behaviour on metal Nemours, Wilmington, U.S.A. Their synthesis surfaces, where formation of new carbon-carbon, involves metal complexes containing multiply- carbon-nitrogen or carbon-sulphur bonds may bonded terminal (PR,)- ligands which lead to occur, see Figure 2. Some clusters have been built-in electronic unsaturation at the early metal found to catalyse selectively the homogeneous centre, see below: hydrogenation of diems and alkynes (5) or repre- R, sent possible models, isolable in the case of ruthenium, for the intermediates involved in the cobalt mediated co-oligomerisation of functionalised alkynes leading to heterocyclic products. [MI = (~-C,Hd,Zr,(v-C,H,),Hf The construction of new bridging ligands in [M’l = Ru, Rh, Ir, Pd, Pt dinuclear and trinuclear cobalt complexes was Reactivity studies have demonstrated the im- presented by Dr. M. J. Mays of the University portance of the bridging ligands in allowing, Chemical Laboratory, Cambridge, U.K. The amongst other things, different core structures coupling of small molecules or fragments such (planar, bent, with metal-metal interactions) to as Ph,P, RC=CR‘, CH,=C=CH, and CO be stabilised. For example, the d2-d8complex may follow different pathways, and a high regio

Platinum Metals Rev., 1991, 35, (1) 11 selectivity has been observed, depending on the nuclearity of the initial cobalt complex, the nature of the R or R' groups and the order of addition of the ligands. Inorganic units may serve as unique templates for the coupling of organic moieties (6a). A daerent chemistry will take place at a dimolybdenum centre (6b). Professor K. Vrieze of Van't Hoff Instituut, Amsterdam, The Netherlands, described the activation of metal cluster-co-ordinated enimine by hydrogen and carbon monoxide, see Figure 3. A sequence of isomerisations which took place about a Ru, chain of atoms was carefully monitored. The diastereoselectivity of the reactions was emphasised, illustrating the importance of introducing chirality in such molecular systems. Two processes were observed in an unprecedented interconversion between diastereoisomers of a linear tetranuclear ruthenium complex: a mdical mechanism and an intramolecular conversion induced by carbon monoxide addition. The chemistry of carbon-carbon, carbon- nitrogen and nitrogen-nitrogen multiple bonds on clusters was described by Professor H. Vahrenkamp of the UniversitAt Freiburg, Ger- many, another member of the four-party joint research project. By varying the ligands and the metals in a systematic way (isoelectronic and isolobal relationships) he described the basic aspects of the cluster-surface analogy and various substrate interconversions in the ligand sphere (7), see Figure 4. The key influence of the substrate bonding mode on its reactivity is illustrated, for example, by the fact that the p3- v2-C=CH, unit is electrophilic at the outer carbon atom, in contrast to vinylidene ligands in mono- or dinuclear complexes. Selected examples illustrated the pathway from the fundamental study of cluster-ligands interactions to cluster- mediated organic synthesis. The reversible and diastemxpecific insertion of the pmhiral alanine precursor, 2-acetamidoacrylic methyl ester, into the metal-hydrogen function of the chiral clusters HCoMM'(p,-CR)Cp(CO), , see Figure 5, (where M = Ru, 0s; M' = Mo, W, R = Me, Ph) was shown to be of the Markovnikov-type. The diastereospecificityobserved illustrates the

Platinum Metak Rev., 1991, 35, (1) 12 Fig. 4 This clueter-aurface analogy shows the core structures Of (a) HzRU~(CO)~~(C~H~O)and (b) RU,(CO)~~(TV~E~~)produced hmreactions of RU,(CO)~,with (a) phenol and (b) N2Et,

transfer of chiral information from a cluster to an organic substrate (8). The preparation of unusual clusters, \/Ru organophosphorus and organobomn cage compounds, and organic cyclic addition products of alkynes and akenes by using the highly reactive intermediates generated in metal vapour reactions was described by U. anneck of the Universittit Heidelberg, Germany. Mild reaction conditions may thus be used, owing to the enhanced reactivity which characterises bare metal atoms (9). Professor L. A. Or0 of the University of R Zaragoza, Spain, presented a number of C multinuclear rhodium and iridium complexes whose structures arnlargely controlled by binucleating m, N 0 or N? ligands. The stabilisation provided by these ligands enables different arrangements of metal atoms to be characterised. Their flexibility allows, in many cases, the promotion of intra- or intermolecular interactions. A linear tetrairidium complex was

C Fig. 5 Insertion of a pmhiral substrate 2-acet Me' Me' 'COOMe amidoacrylic methyl ester into the M-H bond of a chiral cobalt cluster

Fig. 6 The flexible framework of birmclear iridium complex [Ir,@-pz)@-SBu')@- MeO,CC=CCO,Me) (CO)2{P(OMe),}z](a) before and (b) after oxidative addition of I2

Plotinurn Metals Rev., 1991, 35, (1) 13 Platinum Group Metale-Based Bimetallic Couples Used in Heterogeneous Catalysis

Catalysed reaction Bimetallic couples

Hydrocarbon skeletal rearrangements Cr-Pd W-lr, W-Pd Re-Pt Fe-Ru, Fe-Pt Ru-Ni, Ru-Pt Co-Rh, Co-Pt Rh-lr, Rh-Pt Ir-Pt

~~~ ~~~~~

Hydrogenationhomerisation of Ru-Os, Ru-Ni carbon-carbon multiple bonds 0s-Ni

____~ ~

Hydrogenation of CO and CO, Mo-Fe, Mo-Os, Mo-Co W-0s Mn-Co, Mn-Fe Fe-Ru, Fe-Os, Fe-Co Ru-CO, Ru-0s 0s-Rh, 0s-Ni Co-Rh

Hydrogenation of ketones 0s-Ni

Hydroformylation of olefins Fe-Rh Ru-CO Co-Rh

Reductive carbonylation of nitro derivatives Mo-Pd Fe-Pd

Hydrodesulphurisation Mo-Fe, Mo-Co

shown to be an intermediate in the transannular ed during thecourse of the joint research project oxidative addition of I ,to an Ir , complex (10). on the use of homo- and heterobimetallic car- Oxidative addition of I, to the triply bony1 clusters as precursors of heterogeneous heterobridged complex [Ir, (p-pz)(p-SBut)(p- catalysts. This important area of catalysis has Me0 ,CC = CCO, Me)(CO), {P(OMe)3} ,1 (pz = been recently reviewed and the Table indicates pyrazolate), as shown in Figure 6 results in a the major role played by the platinum group remarkable change in the Ir-Ir distance from metals in such mixed-metal cluster-derived 2.614(2) to 3.626(2) A (11). heterogeneous catalysis (12). Professor G. Predieri of the Universith di Par- The pentanuclear cluster [NiOs,(v-C, H,) ma, Italy, presented some recent results obtain- 01-W {p-Cu(PPh )}(CO) I, supported on

Platinum Metals Rev., 1991, 35, (1) 14 Chromosorb and thermally activated under hydrogen, forms a heterogeneous catalyst for the hydrogenation-dehydrogenation of several substrates, in particular alcohols. It shows higher dehydrogenating ability than the systems derived from the parent cluster [NiOs,(v-C,Hs)(p H) ,(CO) 1 orfbdNiRu (vCsH, )&-HI,(CO) 1 (13). The latter cluster has also been supported on alumina in the presence of potassium hydroxide and thermally decomposed, with the aim of preparing catalysts for ammonia synthesis which would work under milder conditions than the current industrial catalysts. Bimetallic particles MnG) were generated, as shown by energy-dispersive Fig. 7 The core structure of the OC- X-ray analysis. Although it was hund that the tanuclear Pd,Mn, cluster [(OC)Pd&- NC)MnCp ‘(CO) 1, containing bridging Ru ,(CO) ,2 -derived catalyst was more than twice cyanide ligands as active as the Nib,-derived catalyst for the same metal loading and at 400°C, the addition of small amounts of cobalt (0.1 per cent) or cop- stituted of twu helices of opposite chirality (16) per (0.05 per cent) to the 5 per cent ruthenium prompted its use as the “logo” for the Sym- catalyst resulted in an increased productivity at posium, Figure 7. lower temperature (14). It is known that The excellent local organisation by Professor ruthenium, promoted by alkali metals, is much A. Tiripicchio of the Universiti di Parma, Italy, more active than iron in ammonia synthesis and who is a participant in the joint project and who is less affected than iron by the poisoning effects has determined crystal structu~for many of the of water and carbon monoxide but suffers much speakers at this Symposium, and the limited more from the inhibitory effects of hydrogen. number of participants, facilitated numerous ex- Finally, Dr. l? Braunstein, the co-ordinator of cellent discussions. the European research project, described The synergy between the different studies per- heterometallic complexes held together by formed by the research groups represented at this diphosphine or phosphido bridges and which are Symposium was very obvious and was emphasis- good candidates for the study of site selectivity ed during the round-table discussion at the end in heterometallic systems. The first complexes of the meeting. Among the conclusions reached containing an alkoxysilyl ligand which forms a were that concerted European actions, which are v2-p2-Si0bridge, where M is palladium or also increasingly needed in industry, are essential to successfully perform competitive fun- l-7 damental research; and that the high-level (OC), Fe- \ 7“’ teaching facilities available in various Centres of (MeO), Si-0 Excellence must be optimised by encouraging the \ Me mobility of post-graduate and post-doctoral platinum were discussed, where the unexpected students and staff, and by co-ordinating com- interaction between the oxygen donor and the soft plementary expertise. metal centre was demonstrated by X-ray analysis It was felt that the areas covered by this Sym- and IH NMR spectroscopy (15). posium are more topical than ever, and that con- The unprecedented structure and topology of tinuity in performing such studies and training an octanuclear Pd,Mn, cluster containing bridg- post-gmduate students constitutemajor priorities. ing cyanide ligands was discussed. The highly Initiatives were taken to promote these ideas, par- symmetrical structure of this molecule con- ticularly at the European level.

Platinum Metak Rev., 1991, 35, (1) 15 References 1 G. Hogarth, M. Hadj-Bagheri, N. J. Taylor and 10 M. A. Ciriano, S. Sebastian, L. A. Oro, A. Tiripic- A. J. Carty,J. Chem. SOC.,Chem. Commun., 1990, chio, M. Tiripicchio Camellini and F. J. Lahoz, 1352 and references cited Angew. Chem., In[. Ed. Engl., 1988, 27, 402 2 c. Mealli and D. M.bserPb,3. Am. them. SOC., 11 M. T. Pinillos, A. Elduque, L. A. Oro, F. J. 1990, 112, 5484 Lahoz, F. Bo~ti,A. Tiripicchio and M. Tiripic- 3 R. T. Baker, J. C. CalabreseCalabreseandT. and T. E. Glassman, chioCamellini,J. Chem. Soc., DahTrans., 1990, Orgamtallics,Organometallics, 1988, 7, 1989; R. T. Baker, W. 989 C. Fultz,FUltzy T. B. hderMarder and I.I. D. c. Williams, 12 P. Braunstein and J. Rose, in “Stereochemistry of Orgamtallics,Organometallics, 1990, 9, 2357 Organometdic and Inorganic Compounds”, ed. 4 G. Predieri, A. Tiripicchio, M. Tiripicchio I. Bernal,&rnal, Amsterdam, Elsevier, 1989, ~01.3,Vo1.3, camellini,M. Costaand E. Sappa, Organ~metallic~, Chapter 1, pp.pp 3-138 1990, 9, 1729 5 Castiglioni, Giordano and Sappa, 13 F. Castagno, M. Castiglioni, E. Sappa, A. Tiripic- 5 M. Castiglioni, R. Giordano and E. Sappa, J.3. chio,chio, M. Tiripicchio Camellini, P. Braunstein and Organornet. 1989,362,399; ibid., 1989,369, M. p. and Organornet. Ch.,1989y 362, 399;ibid‘, 1989,3699 J.J. Rod, J. Chem. SOC.,Dalton 1989, 1477 419 3. SOC., Trans., 1989, 1477 6 (a) D. Braga, A. J. M. caffyn, M. C. Jennings, M. 14 P. Moggi, G. Men,G. Albanesi, S. Papdopulos J. Mays, L. Manojlovic-Muir, P. R. Raithby, P. and E. Sappa, Appl. Catal., 1989, 53, L1 Sabatino and K. W. Woulfe,3. Ch.Soc., Chm. 15 P. Braunstein, M. Knorr, A. Tiripicchio and M. Commun., 1989, 1401; (b) G. Conole, M. Tiripicchio Camellini, Angezu. Chem., Znt. Ed. McPartlia, M. J. Mays and M. J. Morris,J. Chem. Engl., 1989, 28, 1361; P. Braunstein, M. Knorr, SOC.,Dalton Trans., 1990, 2359 E. Villarroya and J. Fischer, “New Perspectives 7 H. Vahrenkamp, fire Appl. Chem.,1989,61,1777; in Organometdic Chemistry”, ed. P. Braunstein 3. Organomet. Chem., 1990, 400, 107 and W. A. Herrmann, New 3. Chem., 1990, 14, 8 D. Mani, H.-T. Schacht, A. K. Powell, H. 583 Vahrenkamp, Chem. Ber., 1989, 122, 2245 16 P. Braunstein, B. Oswald, A. Tiripicchio and M. 9 U. Zenneck, Angew. Chem., Znt. Ed. Engl., 1990, Tiripicchio Camellini, Angezu. Chem., Int. Ed. 29, 126 Engl., 1990, 29, 1140 Advances in the Study of Platinum Group Elements Progress in the understanding of the iron-copper alloys and osmium-iridium- mineralogy of platinum group metals ruthenium minerals appear to have crystallised worldwide is reported in The Canadian directly from a silicate magma. This paper Mineralogist, 1990, 28, (3). Of the twenty-one serves as a link to the next section, which in- papers included, twelve were presented at the cludes discussions on ophiolite deposits con- annual meeting of the Geological and taining platinum group metals. It is suggested Mineralogical Associations of Canada that sulphur concentration is the factor con- (GAC-MAC) which was held in Montreal, in trolling mineralisation in a silicate matrix. May 1989. The remainder are new papers, all Hydrothermal processes for the transport and relevant to the theme of the above title. deposition of platinum group metals are also The section on occurrences consists of nine considered, including a study by J. H. Cmket papers, commencing with the 1990 MAC of platinum group metal mineralisation in Presidential address given by J. M. Duke on sulphide-rich deposits near to sub-sea the implications of magmatic segregation pro- hydrothermal vents on Ocean ridges. For sur- cess models for Kambalda-type nickel sulphide face deposits, the importance of ground water deposits. A uIllfying model of the magmatic transport involving fulvic acid and simple mineralisation process in layered intrusions is organic analogues is discussed by S. A. Wood. proposed by A. J. Naldrett, G. E. Briigmann A mineralogical study of the system and A. H. Wilson. This attempts to account for platinum-antimony-tellurium has been carried the various platinum group metal concentra- out by W.-S. Kim and G. Y. Chao, and a new tions found in different deposits of apparently palladium-copper-tellurium-sulphur mineral similar genesis. species, Vasilite, is reported by A. V. Atanasov. As these magmatic processes become better While some of the deposits considered may understood, the apparent exceptions to the never be economically viable, either for rule, such as the Alaskan-type Tulameen platinum group metal or base metal exploita- deposits in British Columbia, attract greater tion, the implications of the work reported for interest. There, as discussed by G. T. Nixon, the overall understanding of the subject cannot L. J. Cabri and J. H. G. Laflamme, platinum- be over-estimated. J.H.F.N.

Platinum Metals Rev., 1991, 35, (1) 16 A Means to a Cleaner Environment ENERGY EFFICIENT PLATINUM-CONTAINING FUEL CELLS TO BE INTRODUCED COMMERCIALLY IN THE EARLY 1990s The twelfth National Fuel Cell Seminar held Los Angeles in particular, the regulations will in Phoenix, Arizona, U.S.A. from 26th to 28th require 40,000 zero emission motor vehicles by November 1990, was attended by some 450 1998, increasing to 200,000 by 2003. This will delegates from 17 countries, representing provide a major incentive for the development both developers and potential users world- of fuel cell powered vehicles. The SCAQMD is wide. “Fuel Cells - An Answer to a Cleaner working with the U.S. Department of Energy Environment” was the key theme running to promote development of a viable fuel cell throughout the conference. This was strongly system. The new standards will also require linked to the firm belief that fuel cells would greater efficiencies from the electricity make an important contribution to the world’s generation industries. This will present energy needs over the next ten years as further opportunities for the fuel cell economically viable fuel cell power plants developers. become commercialised. The conference heard The growing concern regarding environmen- that platinum containing phosphoric acid fuel tal problems had accelerated Japan’s fuel cell cells (PAFC) are soon to be produced on a com- research and development programme, accor- mercial basis. Both Fuji and Toshiba announc- ding to T. Sugimoto from the New Energy ed that they had opened PAFC production Development Organisation (NEDO).Coupled facilities in Japan during 1990. The key pro- with the increasing pressure to produce more gress regarding development of Proton Ex- efficient energy generation technology, this has change Membrane Fuel Cells (PEMFC) was the led the Japanese Ministry of International announcement of a U.S. Government spon- Trade and Industry to expect fuel cell plants to sored programme, to be led by General Motors, be generating 1.9 million kW of power by the to produce a PEMFC powered motor vehicle. year 2000, and 8.3 million kW by 2010. The conference reflected the growing extent It was predicted by K. Joon of the of the multi-national collaborations that are Netherlands Energy Research Foundation that now underway to develop fuel cell technologies. in Europe too, current energy generating The Seminar Organising Committee comprised technologies would not be able to comply with the United States Department of Energy, the future emission standards. With the imposition Electric Power Research Institute, the Gas of carbon dioxide constraints, he forecast that Research Institute, the National Aeronautics fuel cells would achieve 10 per cent penetration and Space Administration, and, for the first of the Dutch combined heat and power (CHP) time, the Commission of the European Com- market by the year 2010. In Europe the PAFC munities and the Fuel Cell Development Infor- is generally regarded as the market opener for mation Centre, Japan. Over half of the the higher temperature molten carbonate and attendees were from Japan or Europe. solid oxide fuel cell systems. K. Seip of the Centre for Industrial Research, Norway, An Environmental Overview reported on his work using a model to quantlfy The “Keynote Address” was given by J. the benefits of fuel cells versus coal- and gas- Lents of South Coast Air Quality Management fxed electricity generation plants in terms of District (SCAQMD). Focus was directed their effects on the natural environment, towards the recently approved new U.S. Clean buildings and materials, socio-economic, and Air Act which will enforce ever more stringent health and safety impacts. His model predicted emissions standards over the next 20 years. In that on health costs alone, it would be cost

Platinum Metals Rev., 1991, 35, (l), 17-21 17 effective to switch from coal produced to fuel totype nearing completion at Tokyo Electric cell produced electricity. Power’s Goi Thermal Power Station. Plant costs of $2000/kW were said to be competitive Phosphoric Acid Fuel Cells in Japan, although the fully commercialised for Stationary Applications target cost would be $lOOO/kW. For on-site Evaluation of PAFC demonstrator plants, systems Toshiba have supported the formation both in the 50-200 kW CHP and multi- of a subsidiary company to International Fuel megawatt utility power generation modes, and Cells (IFC), known as ONSI. Fifty-three 200 the progress being made towards commer- kW units have been ordered for U.S., Japan- cialisation of the technology, were reviewed by nese and European customers. Toshiba also has several speakers from Japan, Europe and the its own programme for cogenerators in the U.S.A. In recent years progress has been 50-200 kW size range. They anticipate enter- greatest in Japan. ing commercial production of these units in Activities at Fuji were described by R. 1993. Matsushita reported that Toshiba had Anahara. Following the successful demonstra- also opened a PAFC production plant during tion of a 50 kW on-site cogeneration plant by 1990, with current capacity of 10 MW/year. Tokyo Gas Company, Fuji have now received Although Toshiba are also working on molten orders for 31 of these units with options on carbonate electrolyte fuel cells (MCFC), they another 50. Seven sets of 100 kW have also believe that it would be sometime into the 21st been ordered. Although mostly destined for century before this technology could be com- Japanese gas companies, four of the 50 kW mercialised. They saw the PAFC and MCFC units will be supplied for demonstration pro- playing a role alongside each other, rather than grammes in Europe. Based on the experience competing, from about the year 2010 onwards. gained of a 1 MW power plant during the Progress on the 11 MW PAFC plant at Goi Moonlight Project, Fuji is now planning to con- was outlined in more detail by N. Kato of struct 5 MW plants suitable for electric Toshiba. The bulk of the plant has been install- utilities, in association with Kansai Electric ed, and process and control tests are currently Power Company. Compactness is seen as a key ahead of schedule. The final fuel cell stack design feature that will be a requirement for ur- assemblies, being manufactured by IFC, are ban installation. Fuji opened a semi mass pro- due to be installed early in 1991 with the plant duction facility in November 1990 to meet the becoming operational by the spring of the same early demand for 50 kW and 5 MW power year. Demonstration objectives will be to run plants. The current production capacity is 15 for over 10,000 hours, with 3000 hours of MW per year. Improved cell performance, uninterrupted operation, with electrical and principally through improved catalysis by the heat efficiencies of 41.1 and 31.6 per cent, platinum based electrocatalysts, was seen by respectively. Several poster presentations Fuji as critical to the reduction of both the cost described the operation of IFC’s pre- and the size of the entire plant. Current power production 200 kW cogeneration plants in of- densities had improved to 160 mW/cm2, from fice and hotel situations. Several thousand 80 mW/cm2 in 1986. The target performance hours of operational experience has now been was cited as 230 mW/cm2 by 1992. Fuji were gained by both the gas and electricity power confident that these targets would be met. companies in Japan. Progress by Toshiba in commercialising the In the United States, the major customer for PAFC for both electric utility and on-site use, the ONSI 200 kW units is Southern California was discussed by T. Matsushita. Toshiba in- Gas Company who will start taking delivery of tend to commence production of the 11 MW the first of their ten units in 1992. David Moard units during 1995-96. Plant size would be reported that customer interest had been very about one third of the current size of the pro- high; he commented that through the provision

Platinum Metals Rev., 1991, 35, (1) 18 of Partial Energy Service (PES), fuel cells chromium, platinum-cobalt-chromium and would be a profitable business for Southern platinum-nickel-cobalt. Platinum alloy elec- California Gas. In this scenario the gas com- trocatalysts were also shown to have high activi- pany purchases the fuel cell, and installs and ty for hydrogen oxidation in the presence of maintains the unit on the customer’s property trace levels of carbon monoxide. At platinum while the producer is responsible for perfor- loadings of 0.1 mglcm’ and with 2 per cent car- mance guarantees, provision of spare parts, etc. bon monoxide in hydrogen, an alloy catalyst ex- The customer has no primary responsibility for hibited minimal over-potential at 2OO0C, the fuel cell or its operation, nor direct invest- although this performance declined as the ment in the capital equipment. temperature was reduced to 160OC. Westinghouse Electric Corporation are pro- A poster presentation by T. Ito of NE Chem- ceeding with the development of their air cool- cat Corporation, Japan described the produced PAFC system. With improved cell and stack tion of a higher power density fuel cell system technology they have now achieved cell perfor- with improved cost performance by the use of mance of 702 mV, with a decay of only 6mV per platinum alloy catalysts with higher loadings of 1000 hours. The 2.5 kW demonstration stack platinum than the conventional 10 per cent has so far achieved 5300 hours of operation. platinum supported on carbon. Hatinum-iron- The ultimate Westinghouse product will be a cobalt catalysts at 10,20, 30 and 35 weight per 400 kW module, and the first demonstration cent platinum loadings gave performances of will be at Norsk Hydro in Norway. This plant 734, 752, 765 and 769 mV, respectively, at 200 will be fuelled with by-product hydrogen from mA/cm2. At 700 mV, this translated into 21,36 the chloralkali process. The demonstration, and 39 per cent more power output with the currently at the design stage, is intended for higher loading materials compared to the con- start-up in mid 1992. Westinghouse see a niche ventional 10 per cent alloy catalyst. It was market for the PAFC in industrial applications. calculated that these increased power densities In Europe the major PAFC demonstration is can lead to benefits which outweigh the extra currently the 1 MW plant being built into a new cost of the catalyst. civic centre development in Milan. The plant is Work at the Institute CNR-TAE in Italy on being installed by Ansaldo using fuel cell stacks the influence of particle size of platinum supplied by IFC. Site work is nearly finished catalysts in PAFCs was presented by N. Gior- with installation of the fuel cell system due for dano. Catalysts with particle sizes ranging from completion in September 1991. It is intended to 15-125 exhibited a particle size effect, as commence power generation by mid 1992. The previously demonstrated by other groups, in plant is rated at 1150 kW with an output which the smaller particles possessed intrin- voltage of 23 kV/50 Hz. The power will be sup- sically lower activity. Giordano believed that plied to the Milan electricity distribution grid. this was related more to a change in the propor- tion of specific crystal faces at the surface as the Platinum Catalysts for particle size changed, rather than to the in- Phosphoric Acid Fuel Cells fluence of inter-crystallite separation as propos- A paper on high stability platinum alloy elec- ed by other workers. trocatalysts was presented by K. Tsurumi of Tanaka Kikinzoku Kogyo. He reported cell Fuel Cells for Transportation performances of 780 mV with the latest alloy Applications material, compared to 680 mV with pure Over the past two years there has been platinum systems. Using base metal dissolution increased interest in the potential application of as a guide to long term stability, this alloy fuel cells to vehicular transportation. This has showed very little decay in comparison to prior arisen due both to increased concern about, and art alloys of platinum-vanadium, platinum- regulation of, vehicle emissions in the United

Platinum Metak Rev,, 1991, 35, (1) 19 States, and the recent technical advances in the selectively oxidise the carbon monoxide (in the performance of Proton Exchange Membrane presence of hydrogen) to the required levels of Fuel Cells. For the first time, this year’s less than 10 ppm. seminar attached major importance to transpor- The benefits of a partial oxidation of tation applications. methanol reforming process were outlined by Details of a major new programme, spon- R. Kumar of Argonne National Laboratory. sored by the U.S. Department of Energy, to Although less efficient than steam reforming, build an advanced reformate/air PEMFC power the direct heat transfer characteristics of this plant were revealed at the conference. The pro- type of reformer facilitates good transient ject will be led by the Allison Gas Turbine Divi- response to fluctuating load demands. This sion of General Motors, which will co-ordinate property is seen to be very important for a fuel the effort between General Motors, Los Alamos cell automotive power system. National Laboratory, Ward Power Systems, Ballard Power Systems of Canada will be pro- Dow Chemical Company and the South Coast ducing the fuel cell stacks for the vehicle pro- Air Quality Management District. The overall gramme sponsored by the U.S. Department of aim of the six and a half year programme is an Energy. In addition, D. Watkins reported that actual fuel cellhattery hybrid vehicle further applications for their PEMFC stacks in- demonstration. Although it is intended that the clude a 100 kW unit for a British Columbia bus fuel cell will take as much of the load as possi- programme, with an on-the-road demonstra- ble, batteries are included in the system to cope tion by the end of 1992. Military and utility ap- with part of the power surge demands. Target plications of the PEMFCs are also being performances of the demonstration vehicle in- considered. Demonstrations in small two-man clude fuel economy improvements of 60 per submersibles and at the Dow chloralkali plant cent over conventional engines, a 40 per cent in Sarnia, Canada, are currently underway. reduction in carbon dioxide emission, and a 90 Other fuel cell types being evaluated for per cent reduction of the emissions currently transportation applications were also reported regulated in the U.S.A. A contract has been at the seminar. In particular, PAFCs have an awarded for the first phase of the programme, application in the 50-120 kW range for buses, which has the objective of producing a 10 kW trucks and heavy duty vehicles. R. Kevala of power source system evaluator over a 24 month Booz, Allen and Hamilton, and K. Okano of period. Component research and development Fuji presented updates on the Department of will be carried out in this initial phase and will Energy funded PAFChattery hybrid bus pro- include studies to improve the efficiency of the ject. A 25 kW brassboard design has been suc- platinum based electrocatalyst. cessfully evaluated against typical bus driving One of the greatest challenges in this pro- cycles. The next phase of the project will ad- gramme will be the development of suitable dress the design of the test buses incorporating methanol reformer technology. Several papers both a 50 kW fuel cell and a 132 amp-hour lead addressed reformer concepts. N. E. Vander- acid battery. borgh of Los Alamos outlined the components of a reformer operating via the steam reforming Submarine and Space route. For use with a PEMFC it is necessary to Applications have three reactors in the fuel processing stage. Fuel cells continue to be developed for the After the initial fuel converter and shift reactors more specialised space power requirements, the hydrogen stream still contains 1 per cent and certain marine applications. In particular carbon monoxide. To avoid severe poisoning of there were several presentations on the use of the platinum catalyst the refonnate is passed PEMFCs as air-independent submarine propul- through a preferential oxidation reactor, into sion systems. W. Bette reported that Siemens which small quantities of oxygen are injected to are currently developing a 34 kW laboratory

Platinum Metals Rev., 1991, 35, (1) 20 module for this application. Performance potential for longer term catalyst stability targets are 540 mA/cm2 and 684 mV per cell, compared to the alkaline systems. with a cell active area of 1180 cm2.Small single cells operating under 2 bar pressure of COmdusionS hydrogen and oxygen have exceeded this target “Fuel cells are five years from commer- and shown excellent stability up to 18,000 cialisation’’ has been a frequently used phrase hours, with only 2 pV per hour decay. The cells for many years! We now, however, appear to comprised DuPont Nafion membranes and 4 have reached the time when this phrase can be mg of platinum/cm2 electrode loading. Recent stated more in truth than in false hope. Led by improvements in cell construction and water the Japanese companies, Fuji and Toshiba, the management have increased the current density phosphoric acid fuel cell will won become a to 700 dcm’ at the rated cell voltage. practical reality for 50-200 kW combined heat Emphasis on fuel cells for manned space mis- and power applications. Worldwide concerns sions is presently focused on the development about pollution and global warming continue to of regenerative fuel cell systems, as evidenced increase, and in the coming years this will serve by presentations from NASA, Los Alamos and to broaden further the scope for commercialisa- the Hamilton Standard Division of United tion of these fuel cells. Similarly, a major new Technologies Corporation. The use of elec- opportunity for the Proton Exchange Mem- trolysers powered from solar arrays in conjunc- brane Fuel Cell has opened up, with the start of tion with either alkaline or PEM fuel cells, to programmes to build fuel cellhttery hybrid provide power during dark orbiting periods, of- power systems for transportation, which could fers the best opportunity as energy storage lead to the development of pollution free motor systems for the long duration space missions vehicles. As noted by several speakers, “the being planned for Mars and beyond. PEMFCs future for fuel cells is brighter now than ever appear to be attracting favour due to their before.” G.A.H.

Quasicrystals in Rapidly Solidified Alloys Five-fold electron diffraction patterns were tion have found two new hexagonal aluminium- found in a rapidly solidified aluminium- iridium phases (Pages 27-35). L. Ma, R. Wang palladium alloy in 1978. Although a number of and K. H. Kuo confim the presence of quasicrystals have since been identified in decagonal quasicrystals in rapidly solid5ed particular alloys of aluminium with a platinum AlsPd, but Wt in AlsPt (Pages 37-49). metal, no systematic study has been made. Now a series of papers on the topic, reporting Grove Fuel Cell Symposium work carried out in the P. R. China, has been The successful First Grove Cell Symposium, published in the J. Less-Gnnnwn Met., 1990, held in London, England during September, 163, (1). An overview of quasicrystals in 1989, was reviewed here immediately after the aluminium-transition metal alloys in general, conference (D. G. Lovering, Platinum Metals and aluminium-platinum group metals in Rev., 1989, 33, (4), 169-177). A second particular, is presented by K. H. Kuo (Pages meeting is now planned, and this will again be 9-17). Aluminium-ruthenium and aluminium- held at the Royal Institution, London, from osmium alloys have been studied by Zhong- 24th to 27th September, 1991. Min Wang, Yi-Qun Gao and K. H. Kuo, main- In addition to those already engaged in fuel ly by transmission electron microscopy. They cell technology, the Symposium is expected to observed icosahedral quasicrystalsin melt-spun be of particular importance to people involved ribbons of Al,Ru, but not in Al,Os. Decagonal with advanced energy systems, and those quasicrystals form readily in the latter, but only responsible for energy and environmental rarely in the former (Pages 19-26). policy making. Rong Wang, Lina Ma and K. H. Kuo have Further information can be obtained from: discovered decagonal quasicrystals in both Kay Russell, Elsevier Seminars, 256 Banbury rapidly solidified Al Rh and Al Ir, and in addi- Road, Oxford OX2 7DH, England.

Phtinum Metals Rev., 1991, 35, (1) 21 The Photogeneration of Hydrogen EFFECTIVE PLATINUM-GOLD COLLOIDAL CATALYSTS By Anthony Harriman Center for Fast Kinetics Research, University of Texas at Austin, Texas, USA.

Bimetallic colloidal particles, comprising variable mol fractions of platinum and gold, function as eflective catalysts for the photochemical production of hydrogen under sacrificial conditions. With increasing mol fraction of gold there is a significant decrease in the rate of hydrogenation of the reactants such that higher yields of hydrogen are attainable.

Colloidal dispersions of platinum, stabilised 0 to 1. The actual composition of each colloidal with various surfactants, have been used as dispersion, after treatment with ion-exchange catalysts for the photoreduction of water to resins, was determined by atomic absorption hydrogen as a means of storing solar energy in and the average particle sizes were established the form of chemical potential (1, 2). Hydrogen by high resolution transmission electron evolution can be extremely efficient over short microscopy. X-ray emission spectroscopy car- irradiation periods but, unfortunately, the col- ried out in conjunction with scanning transmis- loids catalyse hydrogenation of unsaturated sion electron microscopy confiied that bonds as the reaction proceeds (3). The total individual particles contained both platinum yield of hydrogen is limited, therefore, by the and gold but their relative intensities, com- susceptibility of the reactants towards pared to the atomic absorption results, sug- hydrogenation. Often, the performance of a gested segregation with surface enrichment of catalyst can be improved markedly by forming gold. an alloy with a compatible metal and it is The platinum-gold colloids were used to known that adding small amounts of gold to catalyse hydrogen-evolution from a well- macroscopic platinum catalysts inhibits alkane established sacrificial photosystem using zinc hydrogenolysis while increasing the rate of tetrakis(N-methyl-4pyridinium)prphyrin as dehydrogenation (4). Preliminary studies have photosensitiser, methyl viologen (MV2+) as suggested that this approach may be applied to electron relay, and dihydronicotinamide highly dispersed catalysts supported on adenine dinucleotide (reduced form) as graphite (5), and we have shown recently that sacrificial electron donor in nitrogen-saturated bimetallic platinum-gold colloids can function water at pH4 (7). Upon illumination of this as efficient hydrogen-evolving catalysts in solar photosystem with visible light, the reducing energy storage devices operated under ambient radical MV+.is formed in high yield and it conditions (6). persists for many hours in the absence of oxygen. Photolysis in the presence of a colloid Results and Discussion ([metall =2 x lo-‘ mol/dm’) resulted in evolu- Colloidal dispersions of platinum and gold tion of hydrogen. As the rnol fraction of gold in- were prepared by y-radiolysis of mixtures of creases, there is an increase in the rate of Na Pt Cl and NaAuCl , in nitrogen-saturated evolution of hydrogen (RH,) until an optimum water at pH7 containing Carbowax 20M value is reached at about 20 to 30 per cent gold (1 x lo-’ molldm’) (1,2). The total metal con- after which RH, decreases. There is also a pro- centration was fmed at 5 x lo-‘ mol/dm’ and gressive increase in the total yield of hydrogen the mol fraction of each metal was varied from on exhaustive photolysis ([H,])as the mol

Platinum MetaLs Rev., 1991, 35, (l), 22-23 22 fraction of gold increases. Overall, the advantages that may be gained by using alloys optimum composition for the catalyst appears in place of pure metals. to be about Pto,,Auo,,. The increased yields of hydrogen obtained Acknowledgement8 with increasing mol fraction of gold are at- The Center for Fast Kinetics Research is supported tributed to inhibition of hydrogenation of the jointly by the Biotechnology Resources F’rogram of the National Institutes of Health (RR00886)and by reactants by surface gold atoms. With mol frac- the University of Texas at Austin. tions of gold exceeding 20 per cent, hydrogen is not consumed upon prolonged irradiation References although this is a serious problem for colloids 1 A. Henglein, J. Phys. Chem., 1979, 83, 2209; 1980, 84, 3461 containing little or no gold. Many of the 2 P. Neta and A. Harriman, in “Photoinduced platinum atoms on the colloid surface are Electron Transfer. Part B. Experimental Techni- prevented from functioning as active catalytic ques and Medium Effects”, ed. M. A. Fox and M. Chanon, Elsevier, Amsterdam, 1988, Chapter hydrogen evolving sites because of specific ad- 3, pp. 110-162 sorption. The adsorbate may be Ha atoms, 3 E. K. Rideal,J. Am. Chem. SOC., 1920, 42, 748 MV2+, MV+* or surfactant used to protect the 4 R. C. Yates and G. A. Somorjai,J. Catal., 1987, colloid against flocculation. Incorporating gold 103, 208 5 P. A. Sermon, J. M. Thomas, K. Keryou and G. atoms into the colloid surface dilutes platinum- R. Milward, Angezu. Chem., Int. Ed. Engl., 1987, platinum co-ordination sites where specific ad- 26, 918 sorption occurs, allowing surface platinum 6 A. Harriman, J. Chem. SOC., Chem. Commun., atoms to operate as active hydrogen sites. 1990, (l), 24 7 A. Harriman, G. Porter and M.C. Richoux, 3. In hydrogen-saturated aqueous solution at Chem. SOC., Faraday Trans. IZ, 1981, 77, 833 pH4 containing colloidal platinum (2 x lo-’ 8 R. Gomez, G. Corro, G. Diaz, A. Maubert and F. mol/dm’), hydrogenation of MV+ occurs Figueras, Nouv. J. Chim., 1980, 4, 677 very slowly. The reducing radical MV’., 9 H. Kubicka, 3. Catal., 1%8, 12, 223 10 J. J. Prinsloo and P. C. Gravelle, J. Chem. Soc., however, is hydrogenated readily under Faraday Trans. I, 1980, 76, 512 ambient conditions and it is apparent that this 11 J. R. Anderson, K. Foger and B. J. Breakspere, reaction is responsible for consumption of J. Catal., 1979, 57, 458 12 J. H. Sinfelt, in “Bimetallic Catalysts”, Wiley In- hydrogen during photolysis. The rate of terscience, New York, 1983 hydrogenation of MV’. (RMV), as catalysed by the various colloids, was measured by elec- Cleavage in Iridium Crystals trochemical methods. It was found that RMV As the only metal with good mechanical pro- decreased sigmficantly with increasing mol perties in air at temperatures above 16OO0C, fraction of gold. The inhibition of hydrogena- iridium is used for the crucibles in which tion of MV+*on the bimetallic particles is a presintered mixed oxides are melted during the growing of high purity single crystals for elec- consequence of the decreased mobility of H. tronic applications. Fabrication techniques atoms (8) and the increased energy of adsorp- have been developed to enable these crucibles tion of H, (9, 10). to be manufactured to the required high stan- This study has shown that the use of dard, none-the-less the factors that govern the bimetallic platinum-gold colloids can improve deformation of iridium are not yet fully established. the rates and yields of hydrogen evolution from A recent letter from the Department of photosystems in which one or more of the reac- Physics of the Urals State University, tants is susceptible towards hydrogenation. U.S.S.R.,where the deformation and fracture This arises because gold atoms at the surface of of metals is a traditional subject of research, the colloidal particle inhibit specific adsorption contributes to the topic with a discussion of the possible cause of cleavage in iridium single and hydrogenation of the reactants. This crystals (P. Panfidov, A. Yermakov and G. behaviour, which is well known for Baturin, 3. Muter. Sci., Lett., 1990, 9, (lo), macroscopic catalysts (11, 12), shows the 1162-1164).

Platinum Metals Rev., 1991, 35, (1) 23 Metal-Hydrogen Systems

A REVIEW OF PALLADIUM AND PALLADIUM ALLOYS

The second International Symposium on Japan. The lattice constants observed were con- Metal-Hydrogen Systems, Fundamentals and verted into deuterium concentrations and poten- Applications, was held from the 2nd to 7th tials by the use of known data on the phase September 1990, in Banff, Canada. This survey relation. A maximum deuterium content, outlines a selection of the papers presented at the expressed as an atomic ratio, D:Pd = 0.80 at conference on work involving hydrogen inter- room temperature was reported. action with the platinum group metals. A limiting concentration of D:Pd = 0.78 was The chairman of the organising committee, reported by P. R. Stonadge, M. J. Benham, S. Professor F. D. Manchester, opened the con- M. Bennington, J. P. A. Fairclough and D. K. ference by commenting on the many new Ross from Birmingham University, who used developments that have arisen within the field time-of-flight neutron W&on and concurrent of metal-hydrogen studies since the 1988 Sym- resistivity measurements to investigate electro- posium in Stuttgart - perhaps most notably as chemical charging of palladium rods. a consequence of the “cold fusion” controversy On a positive note, an alternative approach which has brought many aspects of metal- taken by researchers H. Uchida, Y. Matsumura, hydrogen research to world attention. T. Hayashi and M. Kawachi (Tokai University, Japan) was the use of GM- and NaI-scintillation Cold Fusion counters to measure y- or X-ray emissions from As a reflection of this particular area of interest, an electrolytically deuterided palladium elec- a significant propomon of the papers were con- trode. They reported 20 to 35 per cent excess cerned with various aspects of cold fusion. radiation during deuteriding of palladium wire A group from Japan, K. Tsuchiya (Tokyo in KOD solution at greater than 600 mA/cm2 National College of Technology), K. Ohashi and 20 V but no excess radiation on hydriding (Tamagawa University), Y. H. Ohashi and M. of palladium in KOH at similar current and Fukuchi (Keio University) approached the ques- voltage input. tion by estimating the nearest neighbow distance Negative results were again however reported between two deuterium atoms in a f.c.c. by Y.-Q. Lei, Y.-L. Chen, D.-L. Sun, J. Wu palladium lattice using the Schriidinger equation, and Q.-D. Wang from Zheijiang University, taking into account the electronic screening China, no excess heat or y-ray emission higher cloud. They estimated the D-D distance to be than background were detected during a 290 0.66 A, which is smaller than the molecular hour electrolysis of deuterium oxide using a value of 0.74 A. palladium bar cathode. Several researchers tackled the question of elec- The subject of cold fusion was raised in debate trolytically induced cold fusion by using various again at the conclusion of the conference. Despite techniques to determine the maximum possible the huge number of negative results, and deuterium content of palladium. apparent irreproducibility of the effect, some An in-situ X-ray diffraction observation of a delegates cautioned against complete dismissal palladium foil cathode during electrolysis of of the phenomenon. heavy water solution, particularly concentrating on the nature of the transformation into the Electronic Structure deuteride (p-PdD,) phase, was reported by T. Electronic band structure calculations featured Yamamoto, T. Oka and R. Taniguchi from the in several of the reported theoretical studies of Osaka Prefectural Radiation Research Institute, metal hydride systems. In work motivated once

Platinum Metah Rev., 1991, 35, (l), 24-27 24 again by interest in cold fusion possibilities, A. diffusion relaxation processes, by Gorsky relax- C. Switendick from the Sandia National ation and internal friction measurements, respec- Laboratories in New Mexico, repoxted on the use tively, designed to compare the local motion of of band structure and density of state calculations hydrogen in the ordered and disordered Pd Mn to determine the stability of the palladium system. It was concluded that the relaxation pro- deuterides PdD, PdD, and PdD,. The only cesses appear to be due to stress assisted stable system was concluded to be PdD. hydrogen interstitial reorientation processes. The use of density of state calculations to A comprehensive study of hydrogen induced analyse the Pd-H, alkali metal-H and H-H in- ordering in palladium-manganese alloys over the teractions in the recently synthesised hydrides wider composition range 10 to 31 per cent Na, PdH, and Li, PdH, , was reported by M. manganese, investigated by metallography, X- Gupta (Universit6 Paris-Sud, France) and W. M. ray and electron difhction studies, and by elec- Temmerman (Daresbury Laboratory, Warr- trical resistance measurements, was presented by ington, UK). Since the pure intermetallic com- K. Baba, Y. Niki and Y. Sakamoto from pounds cannot be synthesised in the absence of Nagasaki in collaboration with T. B. Flanagan. hydrogen, such calculations have provided a valuable insight into the role of hydrogen atoms Hydrogen Solubility in the lattice. and Diffueivity The wide range of papers reporting on aspects Order-Disorder Transformations of hydrogen solubility and diffusivity in An area of study in which the platinum group palladium and palladium alloys again reflects metals featured prominently was that of order- continued special interest in the properties of this disorder transformations. Professor T. B. element among its congener elements in the Flanagan of the University of Vermont opened platinum group, and indeed among other metals. a session on this topic by reviewing literature A paper by American workers, G. J. Thomas, evidence and presenting recent observations of S. E. Guthrie, (Sandia National Laboratory), R. how hydrogen can induce lattice mobility in W. Siege1 and J. A. Eastman (Argonne National metals, and lattice changes in disordered alloys. Laboratory) reported pressure-composition There is segregation of palladium-nickel alloys measurements on nanophase palladium, in- into palladium- and nickel-rich regions under vestigating the effects of high surface:volume conditions of ultra high hydrogen pressure and ratio on hydrogen-metal interactions. It was temperatures greater than 493 K, and there is found that in comparison with coarse grained also evidence that the palladium-rhodium- materials, there is an increase in the a-phase hydrogen system may be subject to segregation solubility, but that the &phase on a small scale. Under high pressures of hydr0gen:paUadium solubility limit is decreased. hydrogen, disordered Pd,,Cu,, and Pdo.sAgo.s Thermodynamic parameters of hydrogen and transform to ordered tetragonal structures. At deuterium absorption and desorption by PH2 > 1 MPa and T > 450 K, disordered palladium as derived by calorimetry were Pd Mn transforms to an ordered form which has reported in a paper by W. J. Luo, J. D. Clewley an increased hydrogen solubility. This can be and T. B. Flanagan of the University of Ver- seen as a variation on Le Chatelier’s Principle; mont. It was found that, within the limits of if a disordered alloy can dissolve more hydrogen experimental error, the enthalpies of protide by either ordering or segregating then the stress (deuteride) formation and decomposition were is reduced. equal, and further that there is no evidence of Two papers contributed by researchers B. any anomalous excess heat evolved in the PdD Sobha, B. Coluzzi, C. Costa and F. M. Mazzolai system as compared to PdH. of the University of Perugia, Italy, reported on Although the stability of palladium hydride a combined study of long range and short range itself tends to be too high for convenient kinetic

Platinum Metals Rev., 1991, 35, (1) 25 study of its formation and decomposition, Z. Also dealing with the same alloy system, U.S. Gavra, J. R. Johnson and J. J. Reilly of investigators, T. J. Udovic, J. J. Rush (National Brookhaven National Laboratory, New York, Institute of Standards and Technology, reported the use of Pdo.85Nio.,sas a suitable Gaithersburg) and H. Schone (College of William substitute. Experiments carried out with the and Mary, Williamsburg) in collaboration with hydride particles suspended in n-undecane I. S. Anderson from the Paul Scherrer Institut, revealed the decomposition kinetics to be in ac- Switzerland, reported on the use of inelastic cord with a phase controlled boundary model in neutron scattering in studying the effect of scan- which the rate limiting process is the phase dium impurity atoms on the vibrational density transformation taking place at the interface bet- of states of hydrogen absorbed in palladium. ween the unreacted hydride core and a hydrogen Preliminary analysis of spectra obtained at 296 saturated metal product layer (shrinking core K and 80 K with hydrogen concentrations of 2 model). The model is to be tested in the future per cent and below, suggested hydrogen trapp- with other systems. ing of less than 1per cent by the scandium atoms A poster by H. Zuchner and T. Rauf from the in a 2 per cent scandium alloy, and the existence University of Munster, Germany, reported of clusters looking like P-phase but modified by derivation of pressure-composition isotherms for having a central scandium atom. the palladium-hydrogen and palladium-silver- In a further analysis of the palladium-platinum- hydrogen systems by using an electrochemical hydrogen system F. A. Lewis, S. G. McKee and bielectrode charging method. This was found to R.-A. McNicholl (Queen’s University, Belfast) be a simple and convenient technique provided reported that relationships between increment of certain specific conditions, such as using thin specific resistivity and hydrogen content, n, for foils and low charging current densities, are the higher platinum content alloys seemed adhered to in order to avoid anomalies in systems representable to a good approximation by a com- where phase transformations occur. mon curve of similar type to “Nordheh” forms Solubilities and thermodynamic quantities of of relationships between resistivity and composi- hydrogen in palladium-ytterbiumsolid solution tion appropriate to substitutional alloys. alloys in the composition range 2.0 to 8.0 atomic Assessments were made as to how far deviations per cent ytterbium, as determined from absorp- from the common curve in the case of palladium tion pressure-composition isotherms between and the lower platinum content alloys could be 273 -473 K and hydrogen pressures up to 100 accounted for in terms of coexistence of phases Torr were reported by F. L. Chen, M. Furukawa with differing levels of hydrogen occupation. and Y. Sakamoto from Nagasaki University . A paper presented by R. V. Bucur and N. 0. Plateau pressures corresponding to the alp phase Ersson from the University of Uppsala, Sweden, equilibrium decrease with ytterbium content. with the help of X. Q. Tong (Belfast), reported Results were compared with previously studied work on Pd 77 Ag2, and pure palladium samples palladium-rare earth alloy-hydrogen systems. designed to investigate the dual influence of Pressure-composition and resistivity- foreign atoms and defects in a host palladium lat- composition relationships derived by an elec- tice on the diffhivity and solubility of hydrogen. trochemical technique at 298 K and 323 K for palladium alloyed with 1, 2 and 4 atomic per cent Amorphous Alloys scandium were presented by R.-A. McNicholl The work reported on amorphous alloys and F. A. Lewis of the Queen’s University, included a study by investigators K. Tanaka, Belfast. In accordance with palladium-scandium T. Araki and T. Abe (Nagoya Institute of being an expanded alloy, the absorption plateau Technology, Japan) of thermal desorption spec- pressures decrease with increasing alloy content tra of hydrogen on glassy and crystalline Zr,Pd but a somewhat unique invariance of the desorp- alloys. By simulation analysis using plural Gaus- tion plateaux was observed. sian curves to reproduce the different possible

Platinum Metals Rev., 1991, 35, (1) 26 site energy distributions of the hydrogen atoms iron or palladium, acting as catalysts, are present (which are dependent on their metal atom on the surface of oxidised titanium or environments), they deduced that in the glassy intermetallic storage materials. This may prove alloy, hydrogen atoms sit on Zr,, Zr,Pd and a significant advance in the development of Zr,Pd2 type sites, whereas in the crystalline poisoning-resistanthydrogen storage systems. A alloy, they sit only on the Zr, sites at low promising material for a hydrogen separation hydrogen contents. membrane was reported by M. Amano, M. 0. Yoshinari from Nagoya Institute of Tech- Komaki and C. Nishimura (National Research nology, Japan and R. Kircheim from Max Planck Institute for Metals, Tokyo, Japan). Palladium Institute, Stuttgart reported that the solubility plated vanadium-15 atomic per cent nickel alloy of hydrogen in amorphous Pd 73. Si ,, membranes show good resistance to hydrogen (X = silver, copper, chromium, iron or nickel) embrittlement while having superior hydrogen alloys decreased in comparison with solubility in permeability compared to palladium. amorphous Pd, Si,, . Difksion coefficients were quite different in various ternary palladium- Concluding Remarks silicon alloys but this could be attributed to dif- and Future Developments fering activation energies when a constant The conference concluded with a rapporteur reference diffusivity was assumed. session in which it was agreed that while some aspects of metal-hydrogen research have reach- Instrumental Techniques ed maturity, the future holds many openings and A number of papers dealt with the use of scope for development of new areas of study par- various instrumental techniques for exploring ticularly, for example, examination of bonding aspects of metal-hydrogen interactions. A paper theories including the idea of pairing interactions, by D. H. W. Carstens and P. D. Encinias (Los and exploring the realm of new intermetallic Alamos National Laboratory, New Mexico) in- materials. volved the use of Laser-Raman Spectroscopy for Proceedings of the Symposium will be publish- studying hydrogen isotopic exchange over ed in the Journal of Less-Common Metals in palladium metal. A joint U.S. group from Spring 1991. The next International Symposium Washington University, St.LouiS and Iowa State on Metal Hydrogen Systems is to be held in University, Ames(D. B. Baker, M. S. Conradi, Uppsala, Sweden from 8th to 13th June 1992. R. E. Norberg, D. R. Torgeson and R. G. R.-A. MCN. Barnes) presented a paper on novel measurements of nuclear spin cross-relaxation in Palladium Membrane Reactors metal hydrides using NMR. D. K. Ross, M. W. The oxidative dehydrogenationof cyclohexane McKergow and D. G. Witchell (University of can take place with high yield when a palladium membrane is used to divide the reactor into reac- Birmingham) with J. K. &ems (Riso National tion and separation sections. In order to establish Laboratory, Denmark) reported the use of dif- the effect of the gas flow patterns when a sweep fuse neutron scattering to monitor super lattice gas is used to remove the permeated hydrogen, reflections as the deuterium atoms order at the five ideal flow models have been analysed and 50 K anomaly in palladium-deuterium. compared by N. Itoh, Y. Shindo and K. Haraya of the National Chemical Laboratory, Tsukuba, Japan u. Chem. Eng. Jpn., 1990, 23, (4), Applications 420-426). promising practical applications involving the Concurrent, counter current, plug-mixing, platinum metals were proposed in a number of mixing-plug and mixing-mixing models were papers presented. A group from the Max Planck considered. It was found that the highest performance was shown by the second of these, Institute in Stuttgart (H. H. Uchida, H.-G. Wulz where the feed gas on one side of the palladium and E. Fromm) have observed remarkable membrane flows in the opposite direction to the enhancement of hydrogen dissociation if nickel, sweep gas on the other.

Platinum Metals Rev., 1991, 35, (1) 27 Isomers of Platinum(I1) and Palladium(I1) Complexes PREDICTING THE DIRECTION OF ISOMEXISATION AND RELATIVE THERMODYNAMIC STABILITY By Professor Yu. N. Kukushkin The Lensoviet Institute of Technology, Leningrad

Geometrical isomers of platinum(l4 and palladium(lZ) differ substantially in their chemical and biological properties. Under certain conditions one isomeric compound can transform into another. It is essential for chemists to be aware of the probable direction of the isomerisation process, and to predict which isomer is likely to be relatively more stable. The rules in this paper will permit such judgements to be made.

Complex compounds of platinum(1I) have picture could be observed for other played an important part in the formation and diaminedihalogen complexes of platinum(I1). development of co-ordination theory, and this This discovery was used as a basis for a per- has given a strong impetus to the growth of in- ceived application in medicine; namely the use organic chemistry. The existence of two isomeric of co-ordination compounds for the chemical forms for the PtX,A, compounds (where A is treatment of cancer. amine, and X is anion) allowed Werner to con- Isomeric compounds are often different in their clude that platinum(I1) complexes have square- thermodynamic stabilities. Thus, Chernyaev and planar structures (1). These isomeric forms are his co-workers established that the total energy a result of the cis- and trans- locations of ligands of trans-[PtCl,(NH,),l is about 13 kJ/mol less A and X. than that of the cis-isomer (5). Thus, under certain conditions, it can be expected that cis-[PtCl,(NH,),I will undergo isomerisation in- A X X A to trans-[PtCl,(NH,),l.The existence of isolable Cis Warn isomeric pairs is caused by the inertness of Later, the conclusion about the square-planar platinum(I1) complexes. Square-planar com- structure of platinum(I1) complexes was plexes of nickel(1I) are more labile than repeatedly confirmed by various physical and platinum(I1) complexes; for this reason, cis- and chemical methods of investigation. trans-isomeric pairs are almost unknown for Isomeric compounds of platinum(I1) differ nickel(I1) complexes. Palladium(I1) complexes significantly in their reactivities, and many of the have intermediate lability. Therefore, isomeric chemical methods used for the identification of cis- and trans-pairs of palladium(I1) are fewer in individual forms are based on this (2). Different number than for platinum(II), but are more rates of substitution of ligands often result in a numerous than for nickel@). substantial difference in the catalytic properties Experimental evidence shows that the isomeric of two isomeric complexes. A remarkable complexes of platinum(I1) and palladium(I1) discovery was made twenty years ago when it was interconvert, often spontaneously or in the found that cis-[PtCl (NH,) ,I had clearly pro- presence of catalytic agents. Sometimes, trans- nounced anticancer properties, while its trans- configuration complexes transform to their isomer was completely inactive (3,4). The same respective cis-configuration complexes, but more

Platinum Metals Rev., 1991, 35, (l), 28-31 28 frequently this occurs the other way round, that trans-effect, then such a compound should not is the &form being less stable converts to the isomerise. trans-form. These conversions can be observed As was noted above, the following process both in the solid phase and in solution. For ex- takes place in the solid phase at 25OOC: ample, the complex [PtBr, (NH,),1 isomerises into trans-[PtBr,(NH,),l at 25OOC (6), while with trans-[PtCI,py(Et, SO)] (where py is pyridine and Et is ethyl), the reverse takes place, - r:xH.]trans and it isomerises into cis-[PtC12py(Et,SO)l at [:::.:I Cis 134OC (7). In the intial compound, the ammonia molecule Predicting the direction of isomerisation is very has the lowest trans-effect and the bromide ion important for chemists. If such a prediction can has the greatest. Thus, in the initial compound, be made, then the relative thermodynamic both of the ammonia molecules will be prone to stabilities can be predicted simultaneously for isomerisation. Isomerisation takes place in the individual isomeric complexes. direction of formation of the trans- Different approaches can be used to explain [PtBr ,(NH 3) ,1 complex wherein the ammonia the direction of isomerisation. Many facts about molecules are located opposite the ligand the isomerisation of platinum(I1) and having the lowest trans-effect, (that is trans to palladium(I1) complexes have been considered themselves). by the author with regard to the trans-effect of In contrast, rrans-tPtCl,py(Et, SO)]isomerises the ligands (2). As a result, a subsmntial amount into the cis-configuration compound: of experimental data has been explained and the direction predicted for yet unknown isomerisation processes (8, 9). LI4"Et I SO]+[yy Et SO] The trans-effect phenomenon has kinetic and static aspects. In a study of the kinetic and static trans Cis aspects of the phenomenon, two respective series In the intial complex the pyridine molecule has of ligands are obtained. the lowest trans-effect, while the greatest trans- Since isomerisation is connected with the effect is exhibited by the diethyl sulphoxide dynamic side of the said phenomenon, then for molecule co-ordinated to platinum(I1) by its the most common ligands the trans-effect series sulphur atom. Thus, in the initial complex, can be written as follows: H,0 < NH,, amines pyridine is labilised by the trans diethyl sulphox- < C1- < Br- < NO-, < PR,, R,SO < CO < ide ligand with its strong trans-effect and so CR- ,. It should be noted that ligands are isomerisation takes place. The molecule of arranged in order of increasing trans-effect. pyridine in cis-tPtCl,py(Et, SO)] is less labile, The more to the right a ligand is in the trans- and this complex happens to be more stable effects row, the greater its lability-producing thermodynamically. action will be. Two more examples from numerous ex- In order to predict the direction of geometric perimental results will now be considered. Thus, isomerisationfor platinum(II) and palladium(I1) it has been established that the following process complexes, it is necessary to select a neutral takes place in the solid phase (10): ligand with the lowest trans-effect to use as. an indicator. The isomerisation goes in the direc- PMe ,Ph Me PMe,ph tion which results in the formation of a complex where that hgand will be located opposite another I4 PMe,J --> [PhMezP .Cl ] ligand with the smallest trans-effect. If, in the Cis tram complex in question, the indicator ligand is Since in these complexes the methyl ligand has located opposite a ligand with the next smallest the greatest trans-effect, the phosphine molecule

Platinum Metals Rev., 1991, 35, (1) 29 is labilised and hence isomerisation occurs. The possible to explain comprehensively the process occurs in the given direction despite the isomerisationprocesses which take place both in fact that the other phosphine molecule is mov- the solid phase and in solution. ing from the position trans to the chloride ligand A Russian proverb states that: “There are no into a trans-position relative to the phosphine rules without exceptions”, and this rule also has ligand, that is from a ligand with relatively low exceptions. In particular, the rule does not trans-effect towards a ligand with a somewhat describe all of the experimental facts for the greater trans-effect. The important thmg is that isomerisation of [PtX2(PR,) ,I-type phosphine- the phosphine molecule moves away from the halogenide complexes. On the other hand, it is ligand having the greatest trans-effect. quite possible that this rule holds true not only It has been established that the use of for platinum(I1) and palladium(I1) complexes, sulphamic acid to remove two niwhgands from but also for the square-planar complexes of the [Pt(NO,), I - complex in a water medium nickel(II), rhodium(I), iridium(1) and gold(II1), leads tothe formationofcis-[Pt(NO,),(H,O),l, that is for complexes with a d*-electron con- which would then isomerise into figuration of the central atom. As was noted trans-[Pt(NO,),(H,O),l (11). Bothof thesepro- previously, the square-planar complexes of cesses are caused by the high rrans-effect of the nickel(I1) are rather labile, and for this reason nitro-ligand, with isomerisation proceeding in both cis- and trans-isomeric forms are extremely accordance with the rule. unlikely to be encountered for [Nix,L, 1-type Isomerisation of complexes in the solid state compounds. However, if we want to see which can be clearly demonstrated using differential of the two possible forms exists, then it will be thermal analysis (DTA) curves. In many cases, the particular form in whose direction the isomerisation is accompanied by an exothermic isomerisation process should be taking place. peak, as forexample, forcis-[PtBr,(NH,),l. Fre- No doubt there are different approaches which quently, isomerisation shows on the DTA curve could be used to explain the direction of as coupled endo- and exothermic peaks, as for isomerisation processes in square-planar com- example, for rrans4PtCl ,py(Et ,SO)] . The en- plexes. Thus, Js(rgensen has formulated the dothermic peak corresponds to the melting of the ligand anti-symbiosis principle which enables a initial complex, while the following exothermic judgement to be made about the relative ther- peak reflects two processes: isomerisation of the modynamic stability of isomeric complexes (12). complex and crystallisation of the isomerisation However, this principle does not describe all of products from the melt. Identical coupled endo- the known experimental facts, either. For exam- and exothermic peaks can also be ple, in a recent paper it was shown that observed during isomerisation of [PtCl, LYI-type complexes (where L is pyridine ~is-[PtMeU(PMe,Ph)~l(10). Thus, the presence and its derivatives, and Y is a ligand with a donor of an exothermic peak and, especially, of atom of oxygen), always have the form of a rrans- characteristic coupled endothermic and exother- isomer (13). Such a situation cannot be explain- mic peaks (without any change in mass in both ed using the anti-symbiosis principles (13). It is cases) can point to the isomerisation process. worth mentioning that the same experimental Since in many cases, platinum(I1) and facts can, however, be explained by the rule palladium(I1) complexes isomerise without any described in this paper. change in mass, it may be concluded that, in the In conclusion, we must note that in addition absence of a solvent, isomerisation proceeds to the trans-effect of inner-sphere ligands, the without loss of ligands, that is in an intra- nature of the solvent and the steric difficulties molecular manner. Probably, a complex of created by large ligands can be important factors tetrahedral type is an intermediate in the which sometimes influence isomerisation. isomerisation process (2). Naturally, these could complicate the predictions Thus, using the rule described, it becomes for the direction of the isomerisation process.

Platinum Metah Rev., 1991, 35, (1) 30 Refereneee 1 A.A. Werner,Werner, “Lehrbuch“Lehrbuch derder Stemxhemie”,Stemxhemie”, htavhtav 7 Yu. N. Kukushkin and V. N. Spevak, Zh. Neorg. Fischer,Fischer, Jena,Jena, 1904,1904, p.p. 338338 Khim., 1971, 16, (2), 435 2 Yu.Yu. N.N. Kukushkin,Kukushkin, “Chemistry“Chemistry ofof CoordinationCoordination 8 Yu. N. Kukushkin, Koord. Khim., 1979,5, (12), Compounds”,Compounds”, VysshayaVysshaya Shkola,Shkola, Moscow,Moscow, 1985,1985, 1856 p.p. 455455 9 Yu. N. Kukushkin, Koord. Khim., 1982,8, (2), 201 3 B.B. Rosenberg,Rosenberg, L.L. VanCamp,Van Camp, J. J. E.E. TroskoandV.Trosko and V. H. Mansour, Nature, 1969,222, (5191), 385 lo M. P. Brown, R. J. Puddephatt, C. E. E. Upton H. Mansour, Nature, 1969,222, (5191), 385 and S. W. Lavington,3. Chem. Soc., Dalton Tmns., 4 B.B. Rosenberg,Rosenberg, MetalMetal IonsIons Bwl.Bwl. Syst.,Syst., 1980,1980, 11,11, 1974, 1613 127127 11 F. E. Wood and A. L. Balch, Zrwrg. Chim. Acta, 5 I.I. I.I. Chernyaev,Chernyaev, V.V. A.A. SokolovSokolov and and V.V. A.A. Palkin,Palkin, 1983, 76, 163 Izv.Izv. SectorsSectors PlatinyPlatiny IONKhIONKh ANAN SSSR,SSSR, 1954,1954, issueissue 28,28, p.142p.142 12 C. K. Jbrgensen, Inorg. Chem., 1964, 3, 1201 66 Yu.Yu. N.N. KukushkinKukushkinandE. and E. S. S. Posmikova,Posmikova,Zh. Zh. M.M. 13 J. Auffret, P. Courtot, R. pichon and J.-Y. Salaun, Khim.,1972,Khim.,1972, 45,45, (l),(l), 180180 3. Chem. Soc., Dalton Trans., 1987, 1687

Magneto-Optical Recording Materials In 1989 the attention of readers of this Jour- cobalt-palladium systems, before going on to nal was drawn to research work being carried out describe and discuss current work on at the Philips Research Laboratories and at E. cobalt/platinum and cobalt/palladium I. du Pont de Nemours on layered cobalt and multilayers. Magnetic hysteresis of the platinum structures, which were considered to multilayers, their magneto-optical properties, have potential for magneto+ptical recording. In and the effect of sputtering conditions and the same issue an abstract of a paper from the underlayers on the coercivity ,were considered. Sony Corporation Research Center describing With large Kerr rotation at shorter wavelengths, some magneto-optical properties of ultrathin and hlgh resistance to corrosion, ultrathin cobaltfplatinumand cobalt/palladium layers, also multilayers of both pairs of materials are con- indicated the potential of these materials for high sidered to be promising candidates for high den- density recording. Continuing interest was sity magneto-optical recording. An examination demonstrated during 1990 by further reports of dynamic read/write characteristics of the from these organisations, and from elsewhere. materials was made, with ultrathin multilayers Progress continues to be made in the subject, deposited on photo-polymerisation glass as can be gathered from the recent literature substrates, pre-grooved with 1.6pm pitch. which includes, among others, papers from the Carrier-to-noise ratios of 53 and 46 dB, at 780 three establishments named earlier. nm, were seen for cobalt-platinum and According to a combined paper from the first cobalt/palladium, respectivdy. A hgher ratio will two establishments, large magnetic anisotropy be achieved by refining the noise level and op- and coercivity in platinudcobalt multilayers is timising the disc structure (S. Hashimoto and Y. dependent on sharp interfaces between the Ochiai,J. Mu@. Mugn. Mum.,1990,88, (1&2), layers. Krypton and xenon are better mass- 2 11-226). matched to the platinum sputtering target than argon, and their use results in less energexic bom- Osmium and Ruthenium Complexes bardment by reflected gas neutrals during the Recent work on organic oxidations by osmium film growth. Thus interfacial mixing of the and ruthenium 0x0 complexes has been the sub- platinum and cobalt films is reduced, and ject of review No. 22 in the TMC Literature magnetic properties improved. Another way to Highlights series (W.P. Griffith, Trans. Met. reduce the mixing of the platinum and cobalt Chem., 1990, 15, (3), 251-256). layers, caused by energetic reflected argon atoms, The most important osmium oxidant is OsO, is to sputter at high pressure; this increases the which, when functioning catalytically, is one of number of collisions that the atoms make before the most effective, selective and efficient organic arriving at the substrate, and so reduces their oxidants. Ruthenium complexes in the higher ox- energy (P. F. Carcia and W. B. Eper, IEEE idation states are more powerful oxidants than Trans. Mugn., 1990, 26, (9, 1703-1705). their osmium analogues. While ruthenium(VI) A further paper from the Sony Corporation complexes are mild, effective oxidants, gives a review of previous studies on the magnetic osmium(VI) complexes have virtually no properties of cobalt-platinum and oxidative properties. (71 Refs.)

Platinum Metals Rev., 1991, 35, (1) 31 ABSTRACTS of current literature on the platinum metals and their alloys PROPERTIES Magnetic and Transport Properties of the UTIn Series (T = Rh, Pd and Pt) Electrical Properties, Stability, and v. H. TRAN and R. mOC, J. Magn. Map. Muter., Applications of Ultrathin Porous Pt Films 1990, 88, (3), 287-294 on Si02 Magnetic susceptibility, magnetisation, electrical R. NOWROOZI-ESFAHANI and G. J. MACLAY,J. VUC. SCi. resistivity and magnetoresistivitymeasurements have Technol. A, 1990, 8, (4), 3591-3597 been performed for the U(Rh, Pd, Pt)In series The morphology of 25 di porous Pt films deposited crystallising in the hexagonal Fe,P type structure. on thermally grown SiO, at mom temperature and Results for URhIn are reported for the first time. An- 25OOC is presented. The impedance was measured tiferromagnetic ordering in URhIn and UPtIn with a over the range 100 Hz to 1 MHz. At 1 kHz, the im- Nee1 temperature of 7 and 22 K and metamagnetic pedance was measured in electric fields up to 250 transitions in fields of - 1.5 and 3.5 Tat 4.2 K have V/cm at temperatures - 192 to 140OC. The AC im- been observed, respectively. Resistivity anomalies at pedance of the 25 hi Pt fdm deposited at room low temperatures have been observed. UPdIn was temperature decreased by 25% in 21 days at 15OOC in antiferromagnetic with a N&l temperature of 20 K. room air, but the AC impedance of the Pt film deposited at 25OOC did not change. Effects of High Concentration CO and C02 on Hydrogen Permeation through Volatilization of Pt-Rh Alloys at High the Palladium Membrane Temperature M. MNO, c. NISHIMURA and M. KOMAKI, Muter. Y. NING, D. DENG and Y. WANG, Guijinshu (Precious Ttans., JIM, 1990, 31, (5), 404-408 Met.), 1990, 11, (2), 12-17 The effects of high concentrations of CO and C02on Studies of the volatilisation of Pt-7Rh and Pt-Rh-Au the H permeation characteristics of a Pd membrane alloys at high temperature showed that the volatilisa- 0.7 mm thick, 12 mm diameter cut kom cold-rolled tion loss of the alloys at 1200-135OoC obey a Pd plate, followed by annealing were investigated us- parabola-straight line rule, and the transposition time ing pure HI, H2-C0 (10%,50%), and H2-50%C02 from the parabola loss to straight line loss decreased at 423-723 K and pressures 0.9-250 kPa. Deteriora- with increasing temperature. The volatilisation loss tion in H permeability and diffusivity in the Pd mem- increased with increasing Rh content and by addition brane occurred for H,-C0(10%,50%) gas below 523 of Au to Pt-Rh alloys. The activation energy of K with a concentration dependence on CO, while on- volatilisation of Pt-7Rh-3Au alloy is 167 kJ/mol. ly slight deterioration occurred for H,-50%C02 gas below 473 K. Results are explained by different ad- Columnar Epitaxy of PtSi on Si( 11 1) sorption energies of CO and CO, at the Pd surface. R. W. FATHAUER, Q. F. XIAO, S. HASHIMOT0 and C. W. Deterioration in H2 permeability is attributed to a NIEH, Appl. Phys. Lett., 1990, 57, (7), 686-691 decrease in effective area for HI dissociation by the Columnar grains of PtSi surrounded by high quality weak adsorption of CO. epitaxial Si were obtained by ultrahigh vacuum codeposition of Si and Pt in an 8:l ratio on Si(ll1) Kinetic Description of the Transition substrates heated to 610-810OC. The areal density of from a One-Phase to a Two-Phase columns varied from 120 to 3.8/pm1,and layers with Growth Regime in AlPd Lateral Diffu- thicknesses from 100 nm to 1 pn were displayed. The sion Couples PtSi grains are also epitaxial and have one of three B. BJANPAIN, J. W. MAYER, J. C. LIU and K. N. TU, 3. variants of the relation defmed by PtSi(OlO)//Si(l ll), Appl. Phys., 1990, 68, (7), 3259-3267 with PtSiIOO11//Si. The kinetics of the solid-state reaction between Al Properties of a Platinum-Yttrium-Boron and Pd is studied in the geometry of a lateral A-Pd diffusion couple at 250-43OOC. The fmt reaction Alloy phase is the crystalline AllPd2 (6) phase and after its K. SCHWARZ and w. MOLLE, Neue Hiitte, 1990, 35, growth to a critical length, the quasicrystalline (lo), 391-393 decagonal AllPd(y’) phase starts to grow in between The properties of a Pt-0.03Y alloy was improved by the Al and the AllPd2 phases. The first-phase adding a small amount of B. The addition of B All Pd I and second-phase Al Pd grow simultaneous- resulted in an increase in the rate of internal oxidation ly. Excellent agreement between the data and the and a fme dispersion of the Y oxide particles was ob- model is found. From the analysis the effective tained. High creep rupture strength, a high creep interface growth constant for the AllPd is extracted resistance and a decreased grain growth were found. as a function of temperature.

Platinum Metals Rev., 1991, 35, (l), 32-46 32 Electrical Resistivity Changes Due to The (a+/$ Hydrogen Miscibility Gaps in Interstitial Hydrogen in Palladium-Rich Hydrogenated Palladium-Rich Pd-Y(Gd)- Substitutional Alloys Ag Ternary Alloys K. BABA, U. MIYAGAWA, K. WATANABE, Y. SAKAMOTO Y. SAKAMOTO, F. L. CHEN, M. FURUKAWA and K. MINE, and T. B. FUNAGAN, 3. Mater. sci., 1990, 25, (9), 3. Less-Common Met., 1990, 166, (l), 45-56 3910-3916 Pd-rich Pd-Y(Gd)-Ag ternary alloys were investigated The changes in electrical resistivity of Pd solid solu- as possible diffusion membranes for H pdication, tion alloys, alloyed with Ag, Au, Cu, Y, Ce, Ti, Zr, and their alloying behaviour and the extent of (a +/.I) V, Nb and Ta, with H concentration were measured H miscibility gaps in hydrogenated alloys were at 301 K up to t(WM)=1.5 x lo-*. The H was studied. Metallographic and X-ray studies of anneal- introduced by electrolysis and measurements of elec- ed Pd~~~x~y(Y(Gd)),Agyalloy with a Ag content y trode potential were also made. The specific electrical of 5-24 at.% and x in at.% giving the value of the resistivity of H-free Pd alloys increased with increas- content of Y and/or Gd, indicate that every one of ing solute contents. these alloys forms as a single a-Pd phase. It was found that the (a + p) H miscibility gaps in the hydrogenated Internal Oxidation of Pd-40Ag-1RE alloys with any given Ag content decrease gradually (RE=Sm, Eu, Gd) Alloys and Their as the content of Y and/or Gd increases, and the critical compositions for the disappearance of the Properties miscibility gaps are approximately isoelectronic. Y. LI, H. DAI and Y. NING, Guijimhu (precious Met.), 1990, 11, (2), 18-22 Do Thermal Spikes Contribute to the Ion- The internal oxidation of Pd-4OAg-1RE (RE=Sm, Induced Mixing of Ni into Zr, Ti, and Pd? alloy wires their properties were studied Eu, Gd) and P. BBRGESEN, D. A. LILIENF'ELD and H. H. JOHNSON, in air at 800-1200°C. For the alloys containing Sm or Appl. Phys. Lett., 1990, 57, (14), 1407-1409 Gd,the oxidation rate along the grain boundaries was higher than that of grains in some parts. It is conclud- Low-temperature ion beam miXing rates for Pd-Ni, ed that the internal oxidation of Pd-40Ag-1RE alloys Ni-Ti and Zr-Ni bilayers greatly exceeded binary col- is controlled by volume diffusion. lision estimates, and appeared quite sensitive to thermodynamic driving forces. In the absence of a temperature dependence such a behaviour is usually Microstructural Stability of Diluted Pb- ascribed to interdiffusion within thermal spikes. It is Cu-(Sn-Se-Pd) Alloys suggested that interdiffusion within a thermal spike A. DE LA TORRE, P. ADEVA, G. CARUANA and M. ABALLE, of the Vineyard-Johnson type is not the dominant Z. Metallkde., 1990, 81, (8), 594-600 mechanism. The evolution of microstructure was followed in homogeneous, fme grained Pb-Cu, Pb-Cu-Sn-Se and On the Constitution of the Pd-Te System Pb-Cu-Sn-Se-Pd alloy optically, by SEM and by up to 28 at.% Te microanalyticalidentification of phases and measure- M. KELM, A. GRTZEN,H. KLEYKAMP and H. PEN- ment of several microstructural parameters, at TINGHAUS, 3. Less-common Met., 1990, 166, (I), temperatures between 323 and 423 K for 4 to 125-133 700 h. Small Cu and Se additions substantially reduce The constitution of the Pd-Te system was completed Pb grain size; Pd acts as a grain stabiliser during heat in the Pd-rich range up to 28 at.% Te and at XOOOC. treatments. Grain size distributions in one or two The solid solution between Pd and Te has a max- dimensions are lognormal and invariant with treat- imum Te content of 16.3 at.% at -77OOC. The ment temperature and time. The Pd containing alloys system shows a eutectic with 23.0 at.% Te at 773OC. have high microstructural stability at the Three phases Pd,,Te, (19 at.% Te), Pd,Te, (26 temperatures studied, making them suitable for at.% Te) and dimorphic Pd3Te (25 at.% Te) were chemical plant application. observed in the subsolidus region. Magnetic Properties of Nonequilibrium Structure Changes on Relaxation of Dif- Fe-Pd Alloys Produced by DC Triode ferently Cooled Pdo.s35Sio.165 Alloy Glass sputtering Y. NISHI, H. =NO, S. UCHIDA and K. OGURI, 3. K. SUMIYAMA, H. FUJIMORI, M. KATAOKA, J. Y. KIM and Mater. Sci., 1990, 25, (lo), 4477-4482 s. L. ZHANG, Jpn. 3. Appl. Phys., Part 2, Lett., 1990, The radial distribution function (RDF)of X-ray dif- 29, (3,1261-1265 fraction was studied for liquid-quenched Pd, .81J Sputter-deposited Fe, -xPd, alloys of - 1OOpm Si,,. 165 alloy glasses in relation to cooling conditions. thickness were prepared by DC triode sputtering. The atomic distance (r,),total co-ordination number The single b.c.c. phase was obtained for x= 0-0.25 (n) and volume (V) were obtained by a first peak of in contrast to the MITOW single b.c.c. of x=O-O.O3 in RDF. The faster the cooling rate, the larger the r, , the equilibrium phase diagram. The lattice constant n and V become. Based on the relaxation theory, it is and the magnetisation increased by annealing below shown that linear changes in r, , n and V with the 500 K and decreased by annealing above 500 K. thickness (0)indicate the reciprocal cooling rate.

Platinum Metals Rev., 1991, 35, (1) 33 High-Temperature Oxidation of Synthesis and X-Ray Crystal Structure of Rhodium Trimesitylrhodium(III) L. A. CAROL and G. S. MA", oxid. Met., 1990, 34, R. S. HAY-MOTHERWELL, B. HLlSSAIN-BATES, M. B. (1/2), 1-12 HURSTHOUSE and G. WILKINSON, 3. Chem. soc., The oxidation kinetics of Rh were measured in air at Chem. Commun., 1990, (18), 1242-1243 1 atm at temperatures 600-1000°C. The oxidation The first neutral homoleptic aryl of Rh(III), weight gain proceeds logarithmically at 6OO-65OoC, Rh(2,4,6-Me1C,H,),, was prepared by interaction followed by power law behaviour at >800°C. The of RhCl, (C, H, S) , and mesitylmagnesium bromide. logarithmic growth kinetics comes from thickening of X-ray crystal studies showed that there is "agostic" hexagonal Rh,O, scales. The transition reflects a interaction between Rh and an orrho-CHi, group in a thickening of hexagonal and orthorhombic Rh,O, distorted fac-octahedral geometry but no evidence for scales. Over 800OC the growth kinetics result from agostic H bonding was found. H NMR spectra over thickening of a predominantly orthorhombic Rh,O, a temperature range indicate synchronised rotation of scale. At 1000°C the oxide becomes volatile. the mesityl group about the Rh-C bond. The Controlled Oxidation of the High A Novel Zwitterionic otho-Metallated Chromium Steel Alloys Fe40Cr and Ruthenium@) Phenolate Fe4OCr3Ru N. BAG, s. B. CHOUDHURY, G. K. LAHIRI and A. M. J. VAN STADEN and J. P. ROUX, &PI. surf. sci., CHAKRAVORTY,J. Chem. SOC.,Chem. Commun., 1990, 1990, 44, (4), 263-269 (22), 1626-1627 Fe40Cr steel with and without 3% Ru added were ex- Decarbonylative metallation of the dialdehyde by posed to 0 at different temperatures in an UHV [Ru(PPh,) ,Cl ,I produced the unusual complex system to fmd out how the Ru enhanced the corrosion [Ru(MeL)(CO)(PPh,),(CI)l. X-ray crystallographic resistance of the alloy. Cr was oxidised before Fe in studies showed that the Ru"P, C, ClO co-ordination both Fe4OCr and Fe40Cr3Ru, but only in the Ru unit has a single net negative charge and the alloy did the G also enrich the surface, at Ru(MeL) fragment incorporates a four-membered temperatures over 275OC, to form a substantial oxide, C,O-chelated phenolato function with a neighbouring possibly because of an attractive interaction between monoprotonated azomethine moiety. Fe and Ru in the bulk. Preparation of Uniform Colloidal Metallic New Compounds in the 30-40 at.% Ru Ruthenium and Its Cornpounds Range of the Rare Earth-Ruthenium F. PORTA, W. P. HSU and E. MATIJEVIC, COhidS surf., (R-Ru) Systems 1990, 46, (l), 63-74 A. PALENZONA and F. CANEPA, J. LeSS-COmnUm Met., Colloidal spherical particles with narrow size 1990, 162, (l), 267-272 distribution of a Ru double salt, New compounds were prepared and identified in the (NH,) ,Ru"10(NO).2Ru1VOC0, SH, 0 were ob- rare earth-Ru (R-Ru) systems and a complete com- tained by ageing solutions of RuCl, containing pound formation scheme was constructed. Two new K, SO, and urea at elevated temperatures. The amor- crystal structures were found and completely resolv- phous product was readily converted to RuO, by ed. Y,Ru, and Er,Ru,, while for a third one calcination at 400%. The same original powder, (RRuJ the complexity of the structure prevented dried and heated at 250-3OOOC in a stream of H, any structural determination. yielded metallic Ru.

CHEMICAL COMPOUNDS ELECTROCHEMISTRY Complex Formation of Platinum with Electrochemical Behaviour of Basal Tm(II) in Aqueous Solution of Malic Acid Single Crystal Pt Electrodes in Alkaline P. G. ANTONOV, T. P. LUTSKO and I. A. AGANOV, Zh. Medium Obshch. Khim., 1990, 60, (8), 1846-1851 E. MORALL~N, J. L. VkQUEZ and A. ALDAZ, 3. Elec- Studies of the interaction of K,PtCl, with troanul. Chem. Interfacial Electrochem., 1990, 288, SnCI,.ZH,O in 1 M malic acids at 2OoC showed the (18~2)~217-228 formation of bimetallic Pt(I1) complexes of anion type The electrochemicalbehaviour of basal single crystal with maximum content of SnC, H, 0; ligands, with Pt electrodes in 0.1 M NaOH has been studied. The the molar ratio=5. Chloride ions in voltammogram for the Pt(ll1) surface orientation (Me, N) I [Pt(SnCl 1 and (Me, N) [Pt, (SnCI,) ,I shows two clearly defmed zones; one corresponds to dissolved in the malic acid were completely replaced weak H adsorption states and the other could ten- by malate-anions, thus preserving the Pt-Sn bond. tatively be assigned to strong H adsorption states. During heating, Pt-Sn complexes undergo inter- The voltammogram for a pt( 100) surface shows four molecular conversion, which result in the formation different H states while for the Pt(ll0) orientation of bimetallic compounds with Pt oxidation order - 1. only one H state is obtained.

Platinum Metals Rev., 1991, 35, (1) 34 Electrochemical Oxidative Cleavage of Rectifying Bilayer Electrodes: Layered the Platinum-Hydrogen Bond in Conducting Polymers on Platinum truns-[PtHCl(PEt3) I w. TORRES and M. A. FOX, Chem. Muter., 1990,2, (3), L. CHEN and J. A. DAVIES, hrg. China. Acta, 1990, 306-31 1 175, (l), 41-45 The preparation of sequential bilayer structures made The electrochemical oxidation of the Pt(I1) hydride, from any pair of polybithiophene, (I), polypyrrole, nuns-[PtHCl(PEt,),l, in CH,CN containing (11) and poly(3-bromothiophene), (III) by anodic NBu,ClO, at a Pt gauze electrode produces almost electropolymerisation on Pt electrodes is described, exclusively Pt(I1) complexes as products, none of and the electrochemical properties of the junction which contain Pt-H bonds; zrans-[PtCl(solvent) between the two conducting polymers are discussed. (PEt,),]+ is the major oxidation product. Titrations The polymers in the outer layers of the electrodes on the electrochemicallyoxidised solutions show that PtAAI and PtAIIAI can be trapped in the oxidised Pt-H cleavage occurs with H+ formation. The state for several hours and charge can be released overall oxidation process is therefore: H- -.H+ and from the outer layers via an appropriate redox couple not Pt(II) -+ Pt(1V). in solution. Reactor Control and Reaction Kinetics Hydrochloric Acid Electrolysis Using for Electrochemical Urea Oxidation Solid Polymer Electrolytes. II. Gas Purity J. F. PATZER, S. K. WOLFSON and S. J. YAO, Chem. Eng. and Current Efficiency Sci., 1990, 45, (8), 2777-2784 I. UEHARA, Y. KAWAMI, N. WAKABAYASHI, M. MOTONE The electrochemical oxidation of urea on anodic Pt and H. TAKENAKA, Denki Kagaku, 1990, 58, (51, surfaces to NH, and C02 was studied in the range 459-464 0.5-1.1 V relative to Ag/AgCl to develop a model to Current efficiencies and purities of H and c1 in HCl mimic the experimentally observed phenomena. The acid electrolysis by membrane-elecuocatalyst com- model indicates maximum urea current utilisation posites of Ir-PtNafion 117iPt-Ir prepared by can be achieved by appropriately controlling the ap- chemical plating were investigated over the range plied current density in the system. The absolute urea 1.7-12 molkg HCl concentrations, and temperatures conversion rate can be maintained by increasing the 25-75OC and current densities up to 100 Ndm2. available Pt surface ma. Cathodic current efficiencies of 97-98% were found. A New Fluoride Resistant Ceramic Elec- The Electroxidation of Methanol in the trode for Electrochemical EMuent Treat- Potential Region of Platinum-Oxygen ment Processes Layer s. K. HARNSBERGER and I. ROMODA, Plat. Sut$ H. MTSUI and A. KUNUGI, Bull. Chem. SOC.Jpn., Finish., 1990, 77, (7), 40-42 1990, 63, (3,1427-1432 The effect of F ion on two inert anode materials, Pt- Methanol oxidation at a Pt electrode in 0.5 mol/dm’ clad Nb and Ir oxide-coated Ti, and a new Ir oxide- H2SO, at high potentials was retarded by the forma- coated Ti suboxide ceramic electrode was determined tion of an 0 layer and a new type of retarding to find its effect when used for treating electrolyte ef- substance from MeOH. During retardation due to fluent. The materials were tested under laboratory the formation of 0 layer, the rate of MeOH oxidation conditions in a HISO, acid-based fluoride containing decreased and increased with increasing 0 coverage solution. The ceramic material had superior corrosion and potential, respectively. Reverse effects in 0 resistance and hence longer life than either of the coverage and potential concurrently occurred when metal oxides. the potential was variable. At low 0 coverage, the decreased effect from 0 coverage was more notable Corrosion Resistance and Electro- than the increased effect from the potential, but this chemical Behaviour of Platinised Porous reversed at medium coverages. Titanium Electrodes in Acid Media during Water Electrolysis Electrochemical Activity of Silicides of Some Transition Metals for the Hydrogen L. S. NANOVA, T. G. BOGATSKAYA, L. A. MIKHAILOVA, S. G. OGRYZ’KCbZHUKOVSKAYA, L. M. YAKIMENKO, G. Evolution Reaction in Acidic Solutions P. BELYAKOV, A. G. VAGANOV and S. D. KHODKEVICH, A. K. VIJH, G. BELANGER and R. JACQUES, ht. J. Elecmkhimiya, 1990, 26, (6), 696-700 Hvdmgen Ew~,1990, 15, (ll), 789-794 Studies were performed of the corrosion resistance of The H evolution reaction was examined on silicides of platinised porous Ti electrodes with a Pt layer transition metals in H,SO, solutions. The highest deposited either galvanically or by ionic coverage us- rates were observed on Pt and Pd silicides, followed ing a magnetron, on thin (0.5 mm) porous (30%) Ti by those of Cu, Cr and Ni. If Fe silicides are used as base during polarisation by a high density current of typical transition metal silicides their electrocatalytic up to 1.0 Ncm’ in 10% HISO, solution. Cumulative activity for the H evolution reaction is enhanced con- data of tested elecuodes in a compartment with solid siderably by electrodepositing traces of Ru, and polymeric electrolyte are given. especially Pt on their surfaces.

Platinum Metals Rev., 1991, 35, (1) 35 Morphological Changes in Silver Col- Catalytic Oxidation of Methanol by loidal Particles during Oxidative Treat- Ruthenium Oxides ment in Complex Solutions of Gold and B. J. KENNEDY, A. w. SMITH and F. E. WAGNER, Awt. Palladium J. Chem., 1990, 43, (9,913-921 M. V. ARTEM'EV, G. A. BRAMTSKII and B. D. The electrocatalytic behaviour of Ru oxidelC elec- STASHONOK, Vest. Akad. Navuk BSSR, Ser. Khim. trodes for 0 evolution and MeOH oxidation in acid Nmk, 1990, (3), 33-37 solutions is reported. The electrodes were The treatment of polychromatic imaging Ag particles characterised by various techniques which showed in H,PdCI, and HAuCl, solutions resulted in a the Ru to be present as a mixture of Ru" oxides, in- change in the spectral and colour properties of an im- cluding the stable rutile phase. Electrochemical age. During the process, the spectral Ag particles studies show that a Rum species promotes the transform to Ag shells with Pd and Au particles being catalytic oxidation of MeOH, while surface-bound ultradispersed on a surface. RuO, is involved in the 0 evolution reaction. Poly@yrrole-2,2'-bipyridyl Rhodium(m) Topotactic Two-Phase Reaction of Complexes) Modified Electrodes: Ruthenium Dioxide (Rutile) in Lithium Molecular Materials for Hydrogen Evolu- Nonaqueous Cell tion and Electrocatalytic Hydrogenation T. OHZUKU, K. SAWAI and T. HIRAI, 3. Electrochem. SOC.,1990, (lo), 3004-3010 I. M. F. DE OLIVEIRA, J.C. MOUTET and N. 137, vLAcnornuLos, 3. Electmanal. Chem. Interfacial Electrochemical and X-ray diffraction studies were Electmchem., 1990, 291, (1&2), 243-249 performed for the reduction of RuO, with rude The synthesis and electropolymerisation of new structure in 1M LiClO, propylene car- (1: 1) [Rh"'(L),Cl,]+BF,- complexes, where L = 2,2'- bonate: 1,2-dimethoxyethane solution. RuO, bipyridine bearing pendant pyrrole units, and the was topotactidly reduced to LiRuO, which is electrochemical behaviour of the resulting polymers othorhombic via an intermediate phase having a are examined. Films of this material are highly stable tetragonal lattice. The reaction was reversible. for bulk electrocatalytic reactions, especially for effi- Although three phases coexisted during the reduction ciently reducing water to H, and for the hydrogena- of RuO, and oxidation of Li,,,RuO, the reaction tion of cyclohexanone to cyclohexanol. was classified as a topotactic two-phase reaction where an intermediate phase existed between the The Electrochemical Reduction of RuO, and LiRuO, phases. Cp*Rh Complexes u. KOELLE, 3. Electrwnal. Chem. Interfacial Elec- PHOTOCONVERSION mchem., 1990, 292, (1&2), 217-229 An Ultramicrostructured Photoelectrode The electrochemical reduction of ICp*RhCl,l,(l) or System Composed of TiO, Single Crystal [(Cp*Rh)@-Cl),IPF, (2) in methylene chloride and acetone and of [(Cp*Rh)(pOH),lPF, and and Layered SiO, and Pt Thin Film Cp*Rh(acetone),'+ in acetone was investigated by M. HIRAMOTO, K. HASHIMOT0 and T. SAKATA, Chem. cyclic voltammeuy and coulomeuy. An involved Len. Jpn., 1990, (8), 1343-1346 stepwise reduction sequence with electron transfer, An ultramicrostructured photoelectrode system com- Cl- loss and disproportionation from (1) or (2) proposed of a TiO, single crystal and thin fdms of SiO, duces the novel blue, air-sensitive, binuclear RU" and Pt was prepared by exposing the vertical section species [Cp*RhClll. of the layered SiO, and Pt fh. The SiO, layer is -140 nrn thick. The electrode showed Application of Ion ImplantationlRBS to photoresponse under irradiation in the presence of the Study of Electrocatalysis NH3,water vapour, EtOH and acetone. This may be the first microphotoelectrode system which can work E. J. KELLY, C. E. VALLET and C. W. WHITE, 3. Elec- tmchem. SOC., 1990, l37, (8), 2482-2491 in the gas phase. Ir-implanted Ti near-surface alloys were prepared by Photocatalytic One-Step Syntheses of ion implantation, characterised by Rutherford Cyclic Imino Acids by Aqueous Semicon- backscattering (RBS) and subsequently anodically oxidised to form electrocatalytically active ductor Suspensions Ir,Ti ,-,O, /Ti electrodes, and their electrochemical B. OHTANI, S. TSURU, S.-I. NISHIMOTO, T. KAGIYA and behaviour in acidic chloride, sulphate and perchlorate K. IZAWA, 3. Org. Chem, 1990, 55, (21), 5551-5553 solutions was studied. The specific catalytic activities Photocatalytic cyclisation using aqueous suspensions (rate per catalyst surface site) of Ir,Ti,-,O,/Ti and of TiO, or CdS loaded with Pt oxides under Ar at Ru,Ti I-,O, /Ti and their relative catalytic activities room temperature was applied to the one-step syn- were evaluated. Ir,Ti, .,O ,/Ti was only 45% as effec- thesis of optically active cyclic imino acids, tive a catalyst for Cl, evolution as Ru,Ti I .,/Ti, but it pipecolinic acid and proline from the cr,w-diamino was far more stable, with a corrosion rate of only 5% carboxylic aads and their Nu-substituted that of Ru,Ti, .,O,/Ti. derivatives.

Platinum Metals Rev., 1991, 35, (1) 36 A Direct Absorber ReactorlReceiver for A Luminescence Quenching Study on the Solar Thermal Applications Localization Problem of R~(bpy)~’+in R. E. HOGAN, R. D. SKOCYPEC, R. B. DIVER, J. D. FISH, Micelles and Hemimicelles M. GARRAIT and J. T. RICHARDSON, chem. Eng. sci., J. T. KUNJAPPU, P. SOMASUNDARAN and N. J. TURRO, 1990, 45, (8), 2751-2758 3. Phys. Chm., 1990, 94, (l), 8464-8468 A novel catalytic reactor concept of 3.5 kW is describ- Quenching studies on the luminescence emission of ed where concentrated radiant solar energy is directly compound Ru(bpy) :+with femyanide ion, absorbed on Rh/Al,O,, thus avoiding the heat- 9-methylanthracene and dioxylstearic acids were car- transfer limitations of conventional tubular reactors ried out in hemimicellar and micellar aggregates to for high-flux conditions. gain insight into the location of this Raman and luminescence probe. Ru(bpy),*+ is bound to a more Photocatalytic Asymmetric Reduction of nonpolar hemimicellar hydrophobic region. Stern- 3-Methyl-2-Oxobutanoic Acid with Chiral Volmer constants for the doxylstearic acid quenching Rho Complexes and Powdery Semicon- of its luminescence in micelles indicated that the optical electron in the metal-ligand charge-transfer state ductors of the probe molecule resides in a bipyridyl ring H. WANG, T. SAKATA, M. AZUMA, T. OHTA and H. which appears to be close to position 7 of the stearic TAKAYA, Chm. htt. 3p., 1990, (8), 1331-1334 acid chain. Photocatalytic asymmetric reduction of the title acid giving 2-hydroxy-3-methylbutanoicacid has been Conversion of Light into Electricity with performed at up to enantiomeric excess of 60% in Trinuclear Ruthenium Complexes Ad- aqueous MeOH with chiral BINAP-Rh(1) complexes and semiconductor photocatalysts, TiO, or US.The sorbed on Textured Ti02 Films efficiency of the asymmetric reduction is still low, but M. K. NAZEERUDDIN, P. LISKA, J. MOSER, N. the asymmetric hydrogenation of a-ketocarboxylic VLACHOPOULOS and M. GRXTZEL, Helvetica Chim. acid has been obtained without using H, . Acts, 1990, 73, (6), 1788-1803 A series of CN-bridged trinuclear Ru complexes of Simultaneous Photodissociation of H, structure [RuL,(p-(CN)Ru(CN)L,‘),I, where and PMe Ph from OsH, (PMe, Ph) :Pro- L = 2,2‘-bipyridine-4,4-dicarboxylic acid and , L’=2,2’-bipyridine (l), and other bipyridines, etc, duction of Dimeric and Paramagnetic have been synthesised. The two carboxylic functions Osmium Polyhydrides act as interlocking groups through which the dye is J. W. BRUNO, J. C. HUFFMAN, M. A. GREEN, J. D. attached at the TiO, film surface. The interlocking ZUBKOWSKI, W. E. HATFIELD and K. G. CAULTON, groups provide strong electronic coupling, allowing Orga~metallics,1990, 9, (9), 2556-2567 charge injection to proceed at quantum yields close to Concurrent photodissociation of H, and PMe,Ph 100%. Monochromatic incident photon-toturrent (=P)from OsH,P, in benzene, THF and EtOH has conversion effxiencies are >SO% in some cases. been proved by chemical trapping. It is the fmt Regenerative cells with these trinuclear complexes polyhydride to undergo two distinct photoprocesses and ethanolic triiodide/iodide redox electrolyte have with comparable efficiencies. The fmal products optimal results with (l), giving a fd factor of 75% observed on photolysis of OsH, P , under vacuum is and a power conversion efficiency of 11.3% at 520 an equilibrium mixture of Os,H,P, and Os,H,P,. nm. The former is also photosensitive, leading to products of P-CH , cleavage (0s, H, (PMe ,Ph), (p-PMePh),), Design of Antenna-Sensitizer Poly- as well as to a product of Os-H heterolysis, nuclear Complexes. Sensitization of tOs,H,P,+l [trans-OsH,P,-l, which contains a uni- Titanium Dioxide with [Ru(bpy), que paramagnetic polyhydride anion. (CN) 2 I2RU(bPY(C00) 2 12, - R. AMADELLI, R. ARGAZZI, c. A. BIGNOZZI and F. SCAN- Spectral, Photophysical and MI LA,^. Am. chem. soc., 1990,112, (20), 7099-7103 Photochemical Properties of Ru(bpy) * + The use of antenna-sensitiser molecular devices is on Porous Vycor Glass proposed as a possible strategy to increase the light H. D. GAFNEY,Coord. Chem. Rev., 1990, 104, (l), harvesting eficiency of sensitised semiconductors. 113-141 The cyano-bridged trinuclear complex The properties of Ru(bpy) :+adsorbed on porous t Ru(bpy!, (CN), 1 Ru(bpy(COO), 1 I’- was prepared Vycor glass have been charactaised. The complex is and stuhed. The complex adsorbs on Ti02 via the immobilised on the glass surface and can be quenched negatively charged -Ru(bpy(COO),) ,-central unit. by 0, ,N,O and SO2. Other forms of quenching are Photophysical and photoelectrochemicalstudies were discussed, as are the few differences in behaviour due performed and emission and excitation spectra show- to the Ru being on a solid support and not in a fluid ed that in this complex the light energy absorbed by medium. The net photoredox chemistry initiates with the terminal Ru(bpy) ,(CN) , (antenna) groups is eff- a two-photon ionisation of Ru(bpy) :+. Electron con- ciently funnelled to the central -Ru(bpy(COO),),- duction may occur by a surface mechanism. (sensitiser) fragment.

Platinum Metals Rev., 1991, 35, (1) 37 ELECTRODEPOSITION AND Platinum Metal Etching in a Microwave SURFACE COATINGS Oxygen Plasma c. H. CHOU and J. PHILLIPS, 3.Appl. Phys., 1990,65, (5), 2415-2423 Deposition of Transition Metal and Mixed The etching of Pt foils in an 0 plasma generated in Metal Thin Films from Organometallic a flow-type microwave system was studied as part of Precursors a general effort to understand the etching of metals in H. D. KAESZ, R. S. WILLIAMS. R. F. HICKS, J. I. ZINK. both plasma and chemical systems. It was found that Y.-J. CHEN, H.-J. MihLER, 2. XUE, D. XU, D. K. SHUH very rapid etching (- 6 ks) took place even at low and Y. K. KIM, New 3. Chem., 1990, 14, (6/7), power inputs of 200 W. The principal plasma 527-534 parameters, including oxygen atom and ion concen- High purity films of Pt, Ir, Rh, Ni and Re have been trations, and electron temperature, were measured as grown by organometallic chemical vapour deposition a function of distance below the microwave coupler. OMCVD (a), while thin fdms of Pt, Rh or Ir have Etching of pt in an 0 plasma jet resulted from the been grown by photo-assisted OMCVD of volatile concomitant action of 0 atoms and high energy hydrocarbon precursors, but these contained more C electrons. than films grown under (a). Short-path OMCVD for organometallicprecursors of limited volatility was us- Use of Oxide Electrodes for Proton- ed to deposit films of intermetallic compounds, Conductor Gas Sensor PtGa, and CoGa. Substrates to be coated are placed in the reaction tube at the temperature needed for N. MIURA, K. KANAMARU, Y. SHIMIZU and N. controlled decompositionof the precursor complexes. YAMAZOE, Solid State Zonics, 1990, 4/41, (Part I), The various hydrocarbon derivatives, carrier gases, 452-455 substrates, light sources, temperatures and means of An amperometric proton-conductor CO sensor producing thin films are discussed. operative at room temperature was developed by using a Pt/SnO, and a Pt/WO, electrode. The CO sen- Preparation of Thin Palladium Films by sitivity of this sensor was about 7 times higher than the H, sensitivity and the 90% response time was - 3 Use of an Electroless Plating Technique minutes. The sensor became H, selective when a Pt- s. UEMIYA, H. sw,T. MATSUDA and E. KIKUCHI, black electrode was combined with a Pt/WO, elec- Nippon Kagaku Kaishi, 1990, (6),669-675 trode. Sensing mechanisms are discussed. An electroless plating technique was used to prepare supported thin Pd fdms permeable only to H. Before The Hydrolysis Products of cis-Dichloro- plating, Pd nuclei were depositied on the outer sur- diammineplatinum(I1). 3. Hydrolysis face of a porous tube by sensitisation and activation at treatments with Sn(1I) chloride and Pd(I1) chloride Kinetics Physiological pH solutions, respectively. The rate of Pd deposition s. E. MILLER and D. A. HOUSE, Znorg. Chim. Acta, during plating was related to the Pd nuclei concentra- 1990, 173, (l), 53-60 tion, which increased with repeated number of The rate of hydrolysis of cis-PtCI,(NH,), has been treatments. Sn deposition retarded Pd deposition, measured in non-buffered aqueous solutions at I =0.2 but treating with AgNO, solution before activation M NaClO, and T=45OC at constant pH over the promoted the formation of Pd nuclei. An alkaline range 4.0-8.5; the reverse reaction was also solution was used to plate the Pd on the porous glass monitored. This allowed models for the hydrolysis of tube, twice as fast as conventional plating methods. cis-PtCI,(NH,) , under physiological conditions to be tested, and shows that the Rosenberg model for Pt(I1) transport in vivo may need modification. APPARATUS AND TECHNIQUE Study by UV-Visible Potential-Modulated An Oxygen Sensor Composed of Tightly Reflectance Spectroscopy of the Stacked Membrane/Electrode/Elec- Chemisorption of CO, Methanol and trolyte Ethanol on Several Noble Metal Elec- K. KATAKURA, A. NOMA, z. OGUMI and 2.-I. TAKEHARA, trodes Chem. Lett. Jpn., 1990, (8), 1291-1294 1. A. CARAM and c. GUTI~RREZ, J. Electroanal. Chem. An 0, sensor which operates at room temperature Interfacial. Electrochem., 1990, 291, (1&2), 289-294 has been constructed using Nafion, a porous Pt The title method has been used as a technique to cathode directly deposited on Nafion and a determine the energy of electronic transitions in polyethylene (PE) film directly covering the cathode chemisorbed carbonyls and the type of bonding of surface. The sensor is amperometric and all the com- CO. This was used to examine the electroadsorption ponents are tightly stacked. The 0, reduction cur- of CO, MeOH and EtOH on Pt, Pd, Rh, Ru and Au rent is limited by the 0 diffusion rate through the electrodes. A maximum is reported, which depends diffusion-limiting PE fdm and it changes in propor- only on the type of bonding of CO to the surface, i.e. tion to 0 concentration of gases up to 100%. linear, bridge-bonded or multiply bonded.

Platinum Metals Rev., 1991, 35, (1) 38 Manufacture and Performance of Sulphur-Resistant Character of Titania- Rhodium/Carbon Mdtilayer X-Ray Supported Platinum Catalysts Mirrors Y. CHEN, Y. CHEN, w. LI and s. SHENG, Appl. Catal., P. BOHER, P. HOUDY, P. KAIKATI, hi. OUAHABI and R. 1990, 63, (l), 107-115 BAR~HEWITZ, Appl. Phys. Lett., 1990, 57, (8), The resistance of Pt/TiO, catalysts to H,S was 834-836 studied by pulse reactions with Pt/AI,O, as a A diode r.f. sputtering technique was used to produce reference. Pt/TiO, was found to be much more resis- Rh/C multilaym for application in the soft X-ray tant than Pt/AI,O, to H,S poisoning. The results region. In situ kinetic ellipsometry, grazing X-ray showed that in TiO, there is labile 0 that can react reflectivity and absolute soft-X-ray reflectivity are us- with H,S to form SO, or SO,, which leave the ed to make measurements. A model assuming a catalyst. Thus, with the F’t/TiOz system a con- quasi-sharp C-Rh interface (4 hi thick) and a diffus- siderable part of S contamination is “auto- ed Rh-C interface (22 hi) in the stack is used to fit regenerated” and the poisoning effect of S on Pt is the reflectivity curves at three experimental therefore mitigated. However, for the Pt/AI,O, wavelengths. Reflectivities as high as 22% at 13.3 hi system, H,S decomposes on Pt giving H, and PtS. and 24% at 44.7 A were measured on a 17 riod multilayer strumre having a period of =69 rOne Study of Pt-Ga/Al,O,Catalysts. I. The interface is relatively ideal and it is sufiicient to give good reflectivities. Reaction of n-Hexane over Pt-Ga/AI,O, Y.-H. SUN, S.-Y. CHEN and S.-Y. PENG, 3. cataf. (Dalian, China), The Use of RuO, in Studies of Polymer 1990, 11, (4), 259-264 The reduction and chemisorption properties of the Blends by Scanning Electron Microscopy Pt-Ga/Al,O, catalysts were studied during n-heme B. OHLSSON and B. TORNELL, 3. Appl. Pol$n. Sci., conversion in a flow microreactor. The addition of Ga 1990, 41, (5/6), 1189-1196 into Pt/AI,O, improved its stability, and the catalyst Flat samples of blends of polypropylene (PP) and containing >3.5% Ga promoted n-hexane conversion. (SEBS) were con- The selectivity for aromatisation, isomerisation and styrene-ethylene-butylene-styrene hydrocracking could be adjusted by changing the Ga trasted with RuO, and studied by SEM having a content of the catalyst. back-scattering electron (BSE) detector. The SEBS phase had bright areas with dark dots and the PP phase was dark. The dots were unstained EB- Role of Sulfur in Catalytic Reforming of domains of the triblodr SEBS polymer. This method Hydrocarbons on Platinum-Rhenium/ gave high resolution images due to the intrinsic elec- Alumina trical conductivity on the surface from the deposited G. hi. BICKLE, J. N. BELTRAhUNI and D. D. DO, hd. Ru species; the RuO, vapour gave electrical conduc- Eng. Chem. Res., 1990, 29, (9), 1801-1807 tivity to the stained areas. This method allows a BSE Cyclohexane and n-heptane reforming were studied detector to be used in morphological studies. on 0.3-0.3% Pt-Re/AI,0,-0.95% Cl catalyst in the presence of S. The combined effect of Re-S and Pt-Sj (where Si is the irreversible form of Pt) that modified the Pt ensemble size and the electronic interactions HETEROGENEOUS CATALYSIS caused the hydrogenolysisand dehydmyclisation activities to decrease. Due to the added effect of Re-S A Heterogeneous “Ligand-Accelerated” decreasing the ensemble size, the fewer “available” Reaction: Enantioeelective Hydrogena- free Pt crystallites on Pt-Re/AI,O, compared to tion of Ethyl Pyruvate Catalyzed by Pt/AI,O, means the toxicity of reversible S was Cinchona-Modified Pt/AI 0 , Catalysts greater for the bimetallic catalysts. M. GARLAND and H.-U. BLASER, J. Am Chem. Soc., 1990, lU, (19), 7048-7050 XPS Studies of Pt-Sn Naphtha Reforming The effect of low modifier concentrations on the rate Catalysts and enantioselectivity of ethyl pyruvate hydrogena- Y .-x. LI, J. hi. STENCEL and B. H. DAVIS,Appl. Catal., tion catalysed by Pt/AI,O, modified with 1990, 64, (1-2), 71-81 10,lldihydrocinchonidine (HCd) was studied in XPS studies of Pt-Sn catalysts with porous and non- order to test the concept of “ligand-accelerated” porous AI,O, and SiO, gel surface areas of 250 m’/g catalysis for a modified heterogeneous system. The and 110 mz/g, and 700 mz/grrespectively, were per- reaction mechanism was found to be in complete formed. Both Pt(0) and Sn(0) were observed in the agreement with a simple two-cycle mechanism. The reduced samples. Sn(O), and alloy formation, occurs adsorption of HCd on the Pt surface must be when Pt and Sn are added as a complex dissolved in reasonably strong and/or only a small fraction of the acetone. The ratio of Pt(0) to Sn(0) varies, at constant surface Pt is modifiable. Simple geometric considera- Pt loading, with the total amount of Sn added in the tions indicate that a modified ensemble should be one preparation. This Pt:Sn ratio varies from about 0.4 to adsorbed cinchona molecule and 10-20 Pt atoms. about 6 for the catalysts studied.

Platinum Metak Rev., 1991, 35, (1) 39 Molecular Die Catalysis: Hexane Selective Acetylene Hydrogenation in Aromatization over PtlKL Mixtures with Ethylene in the Presence of s. J. TAUSTER and J. J. STEGER, J. Cazal., 1990, 125, a Palladium Catalyst (2), 387-389 I. M. ZHVANETSKY and A. S. BERENBLYUM, Studies of n-hexane aromatisation over 0.6-0.8% Neftekhimiya, 1990, 30, (4), 453-457 Pt/KL, prepared by exchanging zeolite L powder Studies of hydrogenation of C, H ,-C, H, mixture on with Pt(NH,),Cl, solution at room temperature for Pdly-Al,O, catalyst performed at 311-373 K in a 20 h, and l%Pt/SiO, catalysts were performed at wide range of reagents concentrations showed the for- 510°C, 100 psig pressure, with a H,/hexane mole mation of C,H, from the intermediate compound ratio of 6. Pt/KL catalysts showed a much greater systems ZH,-C,H, (where Z are new active centres selectivity for hexane aromatisation than Pt/SiO, of the catalyst) which proceeds in two paralled routes. catalysts and a strong preference for cracking the ter- It is shown that in the case of C,H,-C,H, interac- minal C-C bond as opposed to interior bonds. tion, the mechanism of ethylene and acetylene with H, is the same as that during hydrogenation of in- Preparation of Platinum Cluster Catalyst dividual hydrocarbons. Supported on Porous Chelate Resin- Metal Complexes for Hydrogenation of The Effect of Bismuth on the Selective Olefin and Diene Oxidation of Lactose on Supported N. TOSHIMA, T. TERANISHI, H. ASANUMA and Y. SAITO, Palladium Catalysts Chem. Lett. Jpn., 1990, (S), 819-822 H. E. J. HENDRIKS, B. F. M. KUSTER and G. B. MARIN, Catalysts of Pt clusters/chelate resin-metal complexes Carbohydrate Res., 1990, 204, 121-129 of Na(I), Mg(II), and AI(II1) were prepared by reduc- The selective oxidation of lactose by 0, has been tion of F’t ions immobilised on the high porosity sup- studied in a batch reactor containing an aqueous ports. The catalytic activity of the supported clusters slurry of 0.5 kmol/m’ and 1.0 kg/m’ of Pd/C pro- increased in the order: Na(I)

Carbon Monoxide Restructuring of An Infrared Study of the Hydrogenation Palladium Crystallite Surfaces of Carbon Monoxide and Carbon Dioxide R. F. HICKS, H. QI, A. B. KOOH and L. B. FISCHEL, 7. at High Pressure over Pd/La,O, Cutal., 1990, 124, (2), 488-502 n. D. BURKETT, s. D. WORLEY and c. n. DAI, Chem. Six Pd/Al, 0 catalysts, with dispersions ranging Phys. Lett., 1990, 173, (5,6), 430-434 from 3 to 86% were studied during repeated cycles of A new high-pressure IR cell reactor has been used to exposure to CO at 25OC and reduction at 300OC. CO study the reactions of CO and CO, with H, over cycling lowers the dispersion of all the samples by 20 Pd/La,O, films at a pressure of 8300 TOR.The ac- to 50%. The loss of surface sites was higher on the tivation energy for the CO, hydrogenation (25.1 small crystallites. The adsorption capacity recovered kcal/mol) which produces MeOH is higher than that with oxidation at 55OoC and reduction at 300OC. The reported elsewhere for the analogous CO hydrogena- H solubility in the bulk of the Pd crystallites was not tion reaction. The CO, reaction may proceed through affected by CO cycling. Surface restructuring may be hydrogenation of adsorbed CO, rather than by direct used to enhance the catalytic activity of Pd. hydrogenation of CO, over Pd/La 0 j.

Platinum Metals Rev., 1991, 35, (1) 40 Structure-Sensitivity of the Deactivation CO Adsorption on Rhodium(1) and on of Pd/SiO for Methylcyclopropane Metallic Rhodium Supported on Titanium Hydrogenolysis by CO Dioxide J. B. BUTT and c. L. M. JOYAL, 3. Chem. SOC.,Faraday J. HERRERO, C. BLANCO, A. R. GONZLEZ-ELIPE, J. P. Trans., 1990, 86, (16), 2911-2917 ESPIN~Sand L. A. ORO, 3. Mol. catal., 190, 62, (2), Pd/SiO, catalysts with 5-8Ooh metal exposed have 171-177 been characterised for reactivity for The interaction between a cationic organometallic methylcyclopropane hydrogenolysis as a function of Rh(1) compound and TiO, in acetone leads to CO poisoning. The CO surface coverage and metal Rh(I)/TiO,. The reduction with H, at atmospheric crystallite size are important in the deactivation pressure and ambient temperature yields a supported behaviour of the catalyst. &treatment conditions metallic Rh catalyst which is active in 1-hexene help to determine reaction and deactivation structure hydrogenation. The precursor and catalyst have been sensitivity patterns. As CO coverage increases a characterised, and the predominant species is dicar- monotonic decrease in activity occurs for large Pd bony1 on both. Dissociative CO adsorption is particles, while catalysts with >40% metal exposed discussed. have a near-step drop in activity between 20-30% coverage. Selectivity Changes in the Ring-Opening Reaction of Methylcyclopentane over Effects of Promoters of PalladiumlSilica Rhodium Catalysts Caused by the Addi- Catalysts for the Synthesis of Methanol tion of Silver and Metal-Support In- H. s. HAHM and w. Y. LEE, Appl. Coral., 1990,65, (l), teractions 1-9 R. J. FENOGLIO, G. M. -2 and D. E. RESASCO, Methanol synthesis from syngas on promoted Appl. Catal., 1990, 63, (2), 319-332 Pd/SiO, catalysts was carried out at 1-20 atm (H:CO=2) and 230-310OC. The effects of Ca, K or The hydrogenolysis of methylcyclopentane (MCP) La promoters on the activity and selectivity for was studied over Rh-Ag/TiO, catalysts after various methanol formation were studied. The highest reduction/oxidation treatments. The addition of Ag methanol activity was achieved with O.ht.% Ca pro- resulted in a decrease in activity, accompanied by an moted Pd/SiO, catalysts and was about four times increase in the selectivity toward n-hexane (n-Hx). higher than that of non-promoted catalyst. This increase in selectivity was enhanced when Ag and Rh are impregnated simultaneouslyand when the catalysts are reduced at 773 K. The selectivity Effects of Cerium Addition on the CO-NO changes can be interpreted in terms of a shift in the Reaction Kinetics over Alumina- ring-opening mechanism. This shift is caused by a Supported Rhodium Catalysts blockage of large ensembles required to constitute the s. H. OH, 3. Caul., 1990, 124, (2), 477-487 multi-site complexes. This blockage would be more effective when Ag and TiO, species are Laboratory reactor studies showed that the addition of Ce to a low-loaded Rh/Al,O, catalyst resulted in simultaneously present on the Rh surface. changes in CO-NO reaction kinetics, mainly suppres- sion of N, 0 formation, decreased apparent activation Carbon Dioxide Hydrogenation on energy, and a shift to a positive-order dependence of Rhodium Supported on Transition Metal the rate on NO partial pressure. The Ce-induced Oxides. Effect of Reduction Temperature modification of the kinetics leads to increases in the NO reduction activity at low temperatures. on Product Distribution A. TROVARELLI,C. MUSTAZZA, G. DOLCETTI, 1. KAXPAR and M. GRAzIANI, Appl. caral., 1990, 65, (I), Effect of Potassium on the Formation of 129-142 Isocyanate Species in the NO + CO Reac- Studies of the effects of metal reduction conditions tion on Rhodium Catalyst during CO hydrogenation on Rh/TiO, and 8. NOVAK and F. SOLYMOSI, 3. catal., 1990, 125, (I), Rh/Nb,O, catalysts showed the presence of C,-C, 112-122 hydrocarbons which followed Anderson-Schulz- Adsorption and IR spectroscopic studies of the effect Flory statistics. For Rh/TiO,, the role of CO as an in- of K on the formation of isocyanate species in the termediate in CO,hydrogenation was clearly evident. NO + CO reaction on supported Rh catalysts showed In both catalysts, the formation of the SMSI state that the addition of K to 5% Rh/Al,O, significantly (strong metal-support interaction) during high decreased the uptake of H,, CO and NO at 300 K. temperature reduction greatly affected catalytic ac- Preadsorbed K caused a significant increase in the tivities and selectivities. The differences in the formation of the NCO complex, with the maximum general behaviour of the two oxides as far as the intensity obtained for a sample containing 2.5% K. reversibility of the SMSI in the reaction conditions The same effect was observed on Rh/SiO, catalyst was concerned was ascribed to thermodynamic where two NCO species were identified (2180cm- ' and/or kinetic constraints in the formation of SMSI for Rh-NCO and 2310cm- for Si-NCO). during high temperature reduction.

Platinum Metals Rev., 1991, 35, (1) 41 Synthesis of Hydrocarbons and Alcohols Surface Structure and Catalysis for CO from CO and H2 over Co-Rh Catalysts Hydrogenation of the Supported Ru A. L. LAPIDUS, Z. NOVAK, M. M. SAVEL'EV, B. LYUKKE, Species Derived from the Ru (CO) 12 In- T. ZIMMERMAN, S. D. PIROZHKOV, KH. E. MANEK, S. D. organic Oxides SOMINSKII and L. F. RAR, Zzv. Akad. Nauk SSSR, K. ASAKURA and Y. IWASAWA, 3. Chem. soc., Faraday Ser. Khim., 1990, (8), 1707-1709 Trans., 1990, 86, (14), 2657-2662 Studies of synthesis of hydrocarbons and alcohols Supported Ru cluster particles were prepared by the from CO and H2 (CO:H,= 1:2) over Co catalysts surface reaction of Ru,(CO),, with inorganic oxides promoted by addition of Rh and Cu were performed followed by H, reduction at 723 K. On V,O, the at 250-3OO0C and pressure of 0.1-6.0 MPa. The cluster was converted to three-atomic-layer Ru metal results show that 4.5% Co-0.1% Rh-5:10% Cu/TiO, particles, while one-atomic-layer [Rul, clusters were catalysts are highly active in the above synthesis and formed on SiO, (n=12) and TiO, (n=6). Clusters have much higher selectivity in regards to the formed [Ru,(OZ),l (Z=Al or Mg) with Ru-0 surface bonds alcohols as compared to the traditional Co-catalysts. were formed on Al,O, (n=6), K-doped Al,O, (n=6) and MgO (n=3). CH, was predominantly Immobilization of Rhodium Complexes formed on [Rul ,,/SiO, . The bRu atom clusters with with Chiral Cationic Water Soluble Ru-Ru distances of 0.262-0.265 nm had the highest Ligands on Nafion-H and Other Strongly selectivity for C, -C, hydrocarbon formation. Metallic [Ru16 clusters on TiO, had higher activity Acidic Cation Exchange Resins than [Ru,(OAl),I clusters bonded to the surface I. T6TH, B. E. HANSON and M. E. DAVIS, 3. Organomel. through 0 atoms. The smallest surface-bound Chem., 1990, 397, (l), 109-117 clusters on MgO produced mainly CH, and CO,. Rhodium complexes of the chiral cationic water solubleligands, [(S,S)-2,4-bis[-bis(-p-N,N-dimethyl- ammoniumpheny1)phosphinolpentanel' +,etc., were HOMOGENEOUS CATALYSIS immobilised on cation exchange resins. All these supported complexes catalyse the asymmetric A New Platinum-Based Catalyst System hydrogenation of dehydroaminoacid derivatives with for Olefm Asymmetric Homogeneous no detectable loss of Rh into the substrate phase. Hydroformylation Rates and enantioselectivities depend on the ligand and the nature of the exchange resin. S. PAGANELLI, U. MAlTEOLI and A. SCRWANTI, 3. Organomet. Chem., 1990, 397, (l), 119-125 A number of Pt(I1) diphosphino complexes in com- IR Study of CO Adsorption and Its In- bination with SnCI, are known to be active in olefm teraction with Oxygen over Ir/A1203 hydroformylation. It is now reported that the com- Catalyst plex [Pt(C,H,)((+) -DIOP)I interacts with H.-Y. LOU, Y.-z. CHU, c.4. xu and Y.-s. ZHOU, 3. [ptCl,((+)-DIOP)l to give catalysts active in the Catal., 1990, 11, (4), 284-289 hydroformylation of styrene and 1-hexene. The ac- An IR study of the behaviour of CO adsorption and tivities of the systems depend upon the molar ratio of its interaction with 0 over Ir/Al ,0, catalyst showed the two Pt complexes and the nature of the substrate. that CO adsorption on Ir/Al,O, with high Ir loading The systems display good chemioselectivity and in- was an activation process, and the intensity of the ad- duce asymmetry in the branched aldehydes formed. sorbed CO band increased with the increase in ad- 2-Phenylpropanal can be isolated in -27% optical sorption temperature from ambient to 300OC. The purity from styrene hydroformylation. amount of adsorbed CO at 15OOC was approximately one half that of the maximum. The migration of ad- Evidence for a Bis(aUrylidene) sorbed CO and 0 was increased by increasing the silacyclopropane Intermediate in the temperature. Platinum-Mediated Formation of a Silacyclobutene Zeolite A-Supported Ru Catalysts A. C. DEMA, C. M. LUKEHART, A. T. MCPHAIL and D. R. J. C. S. WU, J. G. GOODWIN and M. DAVIS, 3. catal., MCPHAIL, 3. Am. Chem. Soc., 1990, 112, (20), 1990, 125, (2), 488-500 7229-7233 A number of zeolite A-supported Ru catalysts were The treatment of Ph,Si(CECCMe,), with a cationic prepared either by addition of Ru precursor to the Pt-H reagent resulted in the formation of a zeolite A synthesis gel [ZSI with resulting metal being 4-alkylidene-I-silacyclobutenyl ring system. Acetic dispersed intrazeoliticdy, although not uniformly, or acid cleaves at Pt-C bond to yield alkenylsilane pro- by surface deposition of Ru on zeolite A with metal ducts, showing the intermediate formation of a Pt, Si- particles primarily on the external surfaces of the palkenylidene complex. ROH reagents react with a zeolite crystallites. With the exception of the strong proposed bis(alkylidene)silacyclopropane in- molecular sieving effect on the reaction of termediate to initiate ring opening and to form q3- cyclopropane found for RuNaNZSI, the most impor- butadienyl complexes (where R=H, Me, Et or Ph). tant effect on the catalysis was Ru particle size. The R=H complex ion structure was confirmed.

Platinum Metals Rev., 1991, 35, (1) 42 Hydroformylation with Platinum Heteropoly Anion-Moaied Palladium Phosphiuito Complexes Catalyst for Reductive Carbonylation of P. W. N. M. VAN LEEUWEN and C. F. ROOBEEK, Nepv J. Nitrobenzene Chem., 1990, 14, (6/7), 487-493 Y. IZUMI, Y. SATOH and K. WE, Chem. Lett. Jpn., Pt complexes containing phosphinito ligands afford 1990, (9, 795-796 active hydroformylation catalysts at 30-100 bar and An efficient catalyst system of PdQ, and Keggin- 80-10O0C. The hydroformylation rates for a-alkenes type heteropoly anions containing Mo and V which are the same as those obtained with Pt- had a noticeable promoting effect on the Pd, were us- trichlorostannate catalysts. Products are a mixture of ed in a reductive carbonylation of nitrobenzene to alcohols and aldehydes with linearities in excess of form N-phenylcarbamate in the presence of alcohol in 90%. Internal alkenes can also be hydroformylated dimethoxyethane solvent. Turnover numbers were 98 with linearities as high as 70%. and 196 in terms of moles of Pd and heteropoly anion.

Homogeneous Catalysis of Platinum Blue ?r-Olefin-Palladium-Copper Complexes Related Complexes in Photoreduction of as Intermediates in Formation of Water into Hydrogen Propylene Glycol Monoacetate during K. SAKNand K. MATSUMOTO, J. Mol. caul., 1990,62, Oxidation of Propylene in the System (l), 1-14 PdC12/CuC12 lHOAc The evolution of H, is reported on dissolving A. V. KARANDIN, E. V. GUSEVSKAYA, V. A. LIKHOLOBOV, platinum blues [Pt, (NH I ,(C, H, NO) ,1 , (PF,), , A. G. STEPANOV and E. P. TALZI, Kinel Katal., 1990, [R, (MI)s(C,&NO), I(NOi)z (PF6) 1 -5H, 0, etc- 31, (3), 580-584 in water. The H, seems to be due to an interaction Studies of the kinetic and physical-chemical between [Pt,(NHl),(C,H,NO),16+ (1) and proton. mechanisms during propylene oxidation by 0, in the A homogeneous photochemical H-producing catalyst system PdCl I /CuQ ,/HOAc were performed by system is made with (1) or [Pt,(NH])S various electron spectroscopic techniques. The con- (C,H,NO),ls+, using EDTA as sacrificial electron tact of propylene-oxygen gaseous mixture with donor, and Ru(bpy),’+ as photosensitiser and MV’ + acetate solutions of PdQ,, CuClz, LiCl and LiOAc as elecuon relay. Quantum yields for their H, pro- resulted in a catalytic reaction yielding propylene duction are 0.022 and 0.11, respectively. glycol monoacetate and acetone. Palladium-Catalyzed Hetero- and Car- Phase Transfer Pd(0) Catalyzed boannulation of Vinylic Cyclopropanes Polymerization Reactions. 111. and Cyclobutanes Polymerization by Cross-Coupling R. C. LAROCK and E. K. WM, synthesis, 1990, (9), of Alkyl-Boron Compounds and Aromatic 529-530 Halides Catalyzed by PdCl,(dppf) and ortho-Functionally substituted aryl iodides react Bases under mild conditions with vinyl- and E. CRAMER and v. PERCEC, J. Poljm sci.: part A: isopropenylcyclopropane and isopropenylcyclo- P01w. Chm., 1990, 28, (ll), 3029-3046 butane in the presence of Pd(1I) acetate and an ap- A novel one flask polymerisation of a sequence propriate base, K acetate, viethylamine or Na of hydroboration of a diolefm with carbonate to give 2-(l-akenyl)-substituted 9-borabicyclo[3.3. llnonane followed by the inter- 2,3-dihydrObe1120fu~, indolines and indans in molecular cross-coupling of the resulting a-w-bis(B- good yield. This gives a novel versatile route to a alkanediyl-9-borabicyclo[3.3.llnonanes with variety of heterocycles and carbocycles, amenable to dihaloarenes is described. The reactions are catalysed unsaturated cycloalkanes, 1,2-, 1,3- and 1,4- dienes by PdCl,(dppf) and a base and are performed in a as well as alkynes. two-phase (organic liquid-liquid or solid-liquid) phase transfer catalysed system. This provides uni- Carboxylic Acid Transvinylation as que synthetic routes to the preparation of functional Catalysed by Complexes of Palladium polymers containing CC bonds in the main chain. Acetate with Phenanthroline-Like Ligands Hydrodechlorination of CCI, in the A. A. KE~TERLING, A. s. LISITSYN, A. v. NOSOV and v. Presence of Pd(0Ac) A. LIKHOLOBOV,AP~~.Caul., 1990,66, (l), 123-132 G. s. DASAEVA, s. M. VELICHKO, w. A. TREGER and I. The complexing of Pd acetate with di-imine ligands I. MOISEEV, Kinet. Katal., 1990, 31, (4), 858-862 results in a promotion effect on the vinyl exchange Methane was produced by the reaction of Hz on CQ, processes and ensures excellent selectivity and stabili- in acetic acid in the presence of Pd(OAc), catalyst ty of the catalyst under reaction conditions. Vinyla- under 0.1 MPa and at 20-80°C. In the presence of tion of both saturated and unsaturated carboxylic aliphatic alcohols, CH, content in the reaction pro- acids by vinyl acetate proceeds smoothly even at an ducts decreased sharply yielding chloroform and increased concentration of H,O in the mixture. ethyl chloride as main hydrodechlorination products.

Platinum Metals Rev., 1991, 35, (1) 43 Synthetic Methodology Involving the Optically Active Phenanthrolinee in Carbopalladation of Allenes Asymmetric Catalysis. 111. Highly Effi- B. CAZES, Pure Appl. Chem., 1990, 62, (lo), cient Enantioselective Transfer 1867-1878 Hydrogenation of Acetophenone by Carbopalladation of denes by vinylic or arylic Pd Chiral Rhodium/3-&yl Phenanthroline species (vinylic or arylic halides +Pd(O)L, catalyst) Catalysts gives new 2-substituted ,-ally1 Pd complexes, which S. GLADIALI, L. PINNA, G. DELOGU, S. DE MARTIN, G. have interesting stereochemicalproperties due to the ZASSINOVICH and G. MESTRONI, Tetrahedm:Asym- conjugated unsaturated system on the central C atom metty, 1990, 1, (9), 635-648 of the q3-aUyl ligand, and react with high regio and The in situ catalysts prepared from [Rh(Diol)CII, stereoselectivitieswith delocalised carbonucleophiles. (Diol= 1,Shexadiene or 1,5-cyclooctadiene) and The overall process creates two new C-C bonds in a 3-alkylphenanthrolines display extremely high single reaction and leads to functionalised 1,3-dienic catalytic activity in the transfer hydrogenation of (or styryl) compounds of known stemhemistry. acetophenone. Turnover rates up to 10,OOO cyclesh have been recorded in 2-propol solution at 83T, Expanding Industrial Applications of with KOH as promoter. Asymmetric inductions up Palladium Catalysts to 65% e.e. have been obtained, using a ligand with J. TSUJI, Synthesis, 1990, (9), 739-749 a chiral trimethylpropyl substituent. In the asymmetric process the most active and stereoselective A review of Pd in industry as homogeneous and catalytic species might be a Rh hydride complex con- heterogeneous catalysts classifies them into having taining two phenanthroline ligands in a chiral C, oxidative reactions with olefm and aromatic com- array. pounds and oxidative carbonylation, by Pd(I1) salts and appropriate reoxidants; and Pd(0) complexes for reactions of organic halides and reactions via TI- An Experimental and Modelling Study of allylPd complexes. Careful selection of reaction con- Polybutadiene Functionalization to ditions, solvents, choice of ligand and catalyst Polyaldehydes Using a Homogeneous modifiers are necessary to achieve long catalyst life Rhodium Catalyst and high selectivity. (89 Refs.) S. J. TREMONT, E. E. REMSEN and P. L. MILLS, Chem. Eng. Sci., 1990, 45, (8), 2801-2808 Rhodium Phosphine Complexes as The liquid-phase hydroformylation of a polybuta- Acetalization Catalysts diene containing 1,2 and 1,4 olefm units can be per- J. OTT, B. SCHMID, L. M. VENANZI, G. WANG, T. R. formed using a homogeneous Rh-phosphine ligand WARD and G. M. RAMOS TOMBO, New J. Chem., 1990, catalyst (Wilkinson’s) with excess phosphine ligand 14, (6/7), 495-498 at mild reaction temperatures. The product is a Complexes containing Rh(1II) triphos moieties as polybutadiene whose degree of olefim unit hnc- catalyst precursors have been studied for acetalisation tionalisation can be controlled through use of proper and trans-acetalisation reactions. The complexes are reaction conditions. The olefm units in the polybuta- reactive under mild conditions and give a hlgh diene are selectively hydroformylated to the 1,2 ter- turnover rate and induce interesting diastereo- minal branched and 1,4 internally branched aldehyde selectivities. For methyl-substituted acetals products. The aldehyde addition is reasonably [RhCl,(rtiphos)l (1) with substrate:catalyst ratio uniform in the range of polymer molecular weight. 2000: 1 can be used, though a ratio of 10,000: 1 may be possible. Proton-sensitive substrates can be in acetalised with (l), giving products with yields of Unusual Activity and Selectivity Alkyne 80-90%. Hydrosilylation with an Iridium Catalyst Stabilized by an 0-Donor Ligand Asymmetric Metal Complexes Catalysis. R. S. TANKE and R. H. CRABTREE, J. Am. Chem. soc., 1990, 112, (22), 7984-7989 5. Asymmetric Hydrosilylation on the Phosphine Complex [Rh(COD)CIl (3- Studies of alkyne hydrosilylationby Ir in the 0-donor Phephos ligand environment of Grim’s triso ligand ( = tris(diphenyloxophosphorany1)methanide) showed E. YU. ZHOROV, V. A. PAVLOV, W. D. KOROSHKOV and that the reaction is selective for 1-akynes and E. I. KLADUNOVSKII, Izv. Akad. Nauk SSSR, Ser. regioselective for @-products.However, it gave the Khim., 1990, (9), 1951-1955 thermodynamically less favoured cis-vinylsilane pro- Studies of the asymmetric hydrosilylation of ducts by an unexpected anti addition of Si-H to the acetophenone by diphenylsilane in the presence of triple bond. Mechanistic studies suggest that the [Rh(COD)CIl (S)-Phephos showed high activity and alkyne fmt inserts into the M-Si, not the M-H, bond enantioselectivity of the catalysts. Enantioselectivity and that a rrans to cis rearrangement occurs via an q - of the catalyst increased with increase in the reaction vinyl intermediate before reductive elimination. A temperature, and the reaction still proceeded at number of Rh and Ir complexes of the type acetophenone:Rh ratio of up to 20,000. [(triso)ML,I are prepared.’

Platinum Metals Rev., 1991, 35, (1) 44 Selective Oxygenation of Aliphatic Ethers 0x0 Transfer and Metal Oxidation in the Catalyzed by Ruthenium(II) Complexes Reaction of [Ru(PPh,), C1, I with m- M. BREW, A. MORVILLO and G. ROMANELLO, Ztwrg. Chloroperbenzoic Acid: Structure of Chem., 1990, 29, (16), 2976-2979 [Ru(PPh,),(m-CIC,H,CO*)CI, 1 Studies of selective and fast conversions of primary S. CHATTOPADHYAY, N. BAG, P. BASU, G. KUMAR LAHIRI ethers to esters (or lactones) were performed using Li and A. CHAKRAVORTY,3. Chem. Soc., Dalton Trans., hypochlorite in the presence of catalytic amounts of 1990, (ll), 3389-3392 Ru(I1) complex catalysts RuX,L, (L is (CH,),SO One mol and 0.5 mol of peracid were consumed for and (L), is 1,3-bis(diphenylphosphino)propane). 0x0 transfer to PPh , and oxidation of metal, respec- Isopropyl ether undergoes oxidative cleavage to tively, in the reaction of [Ru(PPh,),Cl,l with m- acetone, while secondary ethers bearing methylene ClC,H,CO,H. X-ray studies of the product groups in the 0-position are converted into 0-keto [Ru(PPh,),(m-ClC, H,CO,)Cl,l showed that after ethers. Methyl ethers are unaffected by the oxidation. 0x0 transfer the carboxylate residue remains chelated to the metal centre. The tmns,cis,cis-RuP,O,Cll, A New Ruthenium(VI) Oxidant: Prepara- co-ordination sphere has twefold symmetry. The tion, X-Ray Crystal Structure, and Pro- complex undergoes one-electron quasi-reversible perties of (Ph4)[Ru02(OAc)CI,I reduction but only at low potentials. w. P. GRIFFITH, 1. M. JOLLIFFE, s. v. LEY and D. 1. WILLIAMS, 3. Chem. Soc., Chem. Commun., 1990, FUEL CELLS (18), 1219-1221 The title compound was obtained by the addition of “Development of Advanced Noble Metal- RuO, in CCl, to a slight excess of PPh,CI and glacial Alloy Electrocatalysts for Phosphoric acetic acid in acetonitrile, followed by recrystallisation or by recrystallisation from dichloromethane- Acid Fuel Cells (PAFC)” CCl,. The compound has a quasi-trigonal P. STONEHART, Ber. Bensenges. Phys. Chem., 1990, bipyramidal structure with a symmetrically bound 94, (9), 913-921 acetato ligand and cis-dioxo ligands in the trigonal Highly dispersed Pt and Pt alloys for PAFC elec- plane. It is an effective oxidant for halides, alcohols, trocatalysts of crystallite size 12 A diameter are sulphides and phosphines, functioningcatalytically in discussed. For the cathodes advanced alloys have the presence of N-methylmorpholine-N-oxide. been developed of higher performance than Pt. For anodes diluting the Pt with less expensive materials Autocatalysis and Free Radical gives a superior performance to Pt alone. For 0 in reduction modifications to produce ordered alloys Mechanism a Ruthenium Cluster have given stability for over 9000 hours in the hot Catalysed Hydrogen Transfer Reaction PAFC environment, as have alloys of Pt-Co and/or 0 s. BHADURI, D. MUKESH and K. SHARMA, 3. Chem. containing Ga additions. For H oxidation Pt-Pd SOC.,Chem. Commun., 1990, (21), 1506-1508 alloys show greater tolerance to poisoning and greater The mechanisms of the [(P~,P),NI[H,Ru,(CO),~I stability against crystallite growth. For successful (1) catalysed disproportionation and transfer- commercialisationfuel cells must achieve high perfor- hydrogenations of cyclohex-2-en-1-one have been mance, low cost and long life. shown to involve free radicals. In the latter reaction (1) is converted to other carbonyl species via autocatalysis. Spectroscopic analyses at the end of a ELECTRICAL AND ELECTRONIC catalytic run at 82OC and 5h, and > 100 turnovers of ENGINEERING cyclohexanol with (1) as the precatalyst showed that all of (1) was converted into a mixture of soluble car- Display of Wide Dynamic Range Infrared bony1 and hydridic species. Images from PtSi Schottky Barrier Cameras Ruthenium-Catalysed C-H Bond Activa- J. SILVERMAN, J. M. MOONEY and v. E. VICKERS, Opt. tion. Evidence for a Concerted Eng., 1990, 29, (2), 97-104 Mechanism in Oxyfunctionalization of Twelve-bit digitised infrared images taken with PtSi Cyclic Saturated Hydrocarbons Schottky barrier detector arrays have been processed A. TENAGLIA, E. TERRANOVA and B. WAEGELL, 3. on work stations. Two techniques for 8-bit global Chem. SOC.,Ch. Commun., 1990, (19), 1344-1345 display are compared. The projection technique gives Oxidation of bridged polycyclic alkanes with in situ superior results based on an extensive set on indoor, generated RuO, occurred by a concerted mechanism day and night imagery. The new projection algorithm involving interaction of the highly electrophilic 0x0 can be used as a powerful and robust local contrast Ru species with tertiary unhindered C-H bonds. enhancement technique. A real-time implementation However, it is not yet clear whether an of the projection alogrithm is now incorporated into alkoxyhydroxo-or alkoxyhydrido-oxoRu species was a specially designed camera and gives a very satisfac- involved as a key intermediate. tory automated alternative to the offset/gain controls.

Platinum Metals Rev., 1991, 35, (1) 45 Temperature Dependence of the Stability of Amorphous Ir-Ta Diffusion Resistance in the PtlTi Nondoyed Ohmic Barriers between Cu and Si Contacts to pInAs Induced by Rapid R. DE REUS, R. J. I. M. KOPER, H. ZEIJLEMAKER and F. Thermal Processing w. SARIS, Muter. Lett., 1990, 9, (12), 500-505 A. KATZ, S. N. G. CHU, 8. E. WEIR, W. C. DAUTREMONT- Thin film amorphous Ir-Ta (a-IrTa) was tested as a SMITH, R. A. LOGAN, T. TABUN-EK, w. SAVIN and D. w. diffusion barrier between (100) Si and Cu. Sandwich HARRIS, 3. Appl. Phys., 1990, 68, (8), 4141-4150 structures of (100) Si/a-IrTa/Cu/a-IrTa were stable The temperature dependence of the resistance in the during annealing in vacuum up to 700OC. At 75OOC Pt(60 nm)/Ti(SOnm) nonalloyed ohmic contacts to p- interdiffusion of Cu and Si occurred. The crystallisa- InAs (Zn doped 1 x 10” to 1x 10’9/cm3)induced by tion temperature of thin fha-Ir,sTa,, was reduced rapid thermal processing at 300-60O0C was studied. from 900 to 75OOC in the presence of Cu. The high The ohmic nature of these contacts was attributed to stability of the metallic a-IrTa buffer layer makes it both the low metal-semiconductorinterfacial barriers useful for application in miniaturisation of very large and to the heavily doped semiconductor contacting scale integrated electronics. layers. The results showed conversion from thermionic emission as the dominant carriers transport mechanism across the interfacial barrier for the as- MEDICAL USES deposited sample to a combination of thermionic and field emission mechanisms for the heat-treated Metal Complexes as Anticancer Agents. samples. The Future Role of Inorganic Chemistry in Cancer Therapy Electrical and Structural Properties of B. K. KEPLER, New 3. Chem., 190, 14, (6/7), PtlTi/p+-InAsOhmic Contacts 389-403 A review of the background and reasons for the suc- A. KATZ, S. N. G. CHU, B. E. WEIR, W. SAVIN, D. W. cess of cisplatin in the treatment of various tumours HARRIS, W. C. DAUTREMONT-SMITH, T. TANBUN-EK and is discussed. Other metal complexes with cancer in- R. A. LOGAN, 3. Vac. sci. Technol. B, 1990, 8, (5), hibiting properties for chemotherapy are examined; 1125-1127 these include Ru compounds, Ti compounds and The thermally stable Pt/Ti metallisation scheme was possibly Au and Sn compounds; as well as drug applied to Zn doped p+-InAs layers to evaluate the targetting with R complexes showing affinity to hor- mone receptors and osteotropic properties. (77 Refs.) influence of the outstanding electrical properties of the p+-InAs, such as the narrow band gap and the [Bis(aminomethyl)dimethylsilanel platin- surface Fermi level pinning in the conduction band um(II)dichloride: A Potential Antitumor on the ohmic contact performance. Zn doping was Agent 1x10” to I~lO~~/cm’.After rapid thermal R. D. HAUGWITZ, W. K. ANDERSON, J. PLOWMAN, R. processing for 30 s the specific contact resistances KASLINAL, D. M. HOUSTON and v. L. NARAYANAN, were lowered to <6 x 10- ’Qcm’ for a 45OOC anneal. Appl. Orgamt. Chem., 1990, 4, (4), 375-378 This heat treatment enhanced limited reactions in The title compound was synthesised by a three-step both the Pt/Ti and Ti/InAs interfaces, but did not procedure and its anti-tumour activity was in- degrade the stable microstructure. vestigated against L1210 leukaemia in mice. With suitable dosing it extended the life span by at least 100% and resulted in 40-50% survivors (day 30) in Hole Trap Level in Pt-TilpInGaAsln-InP two experiments. It appeared to be as least as active Heterostructures Due to Rapid Thermal as cisplatin under these conditions. Processing K. L. JIAO, A. J. SOLTYKA, W. A. ANDERSON and A. Effect of Palladium Addition on the KATZ, Appl. Phys. Lett., 1990, 57, (18), 1913-1915 Tarnishing of Dental Gold Alloys Deep level transient spectroscopy and I-V-T M. OHTA, M. NAKAGAWA and S. MATSUYA, 3. Muter. measurements were performed on R-Tilp- Sci.: Muter. Med., 1990, 1, (3), 140-145 InGaAs/n-InP heterostructure mesa diodes annealed Tarnishing tests were performed on Au-Cu-Pd and by rapid thermal processing (RPT).Four electron Au-Cu-Ag alloys. Tarnish resistance was almost trap levels with activation enellgies of 0.61,0.45,0.35 perfect for the alloys with nobility of >SO%, but it and 0.30 eV were observed which are believed to be seemed to relate to the Pd:Au atomic ratio for the native defects in InP, and they were independent of alloys with low nobility. Pd inclusion reduced the tar- RTP conditions. A new hole trap, with an activation nish susceptibility up to - 10 at.%. Tarnishing of the energy of 0.89 eV was found only for samples anneal- alloy with low nobility was very sensitive to its ed at >5OO0C and thought to be introduced by Ti dif- miCrOStruCture. Pd-bearing alloy showed no increase fusion at high temperature. I-V-T data were in the degree of tarnishing by phase separation. This consistent among all samples, indicating that the hole may be attributed to the enrichment of Pd in the Cu- trap level is not dominant in the current mechanism. rich phase.

Platinum Metals Rev., 1991, 35, (1) 46 NEW PATENTS METALS AND ALLOYS ELECTRODEPOSITION AND SURFACE COATINGS Gold Based Alloy for Jewellery LENGD. RUSSKIE SWOT. Russian patent 1,498,809 Non-Corrosive Palladium Electroplating A Au based alloy contains 58.0-59.0 wt.% Au, Solution 3.5-4.5 wt.% Pd, 7.5-8.5 wt.%,Ag, 0.7-1.5 wt.% AT. & T. BELL LAB. U.S. Patent 4,911,798 In, 0.5-1.2 wt.% Mn and balance Cu. The alloy has Electroplating of Pd and Pd alloys uses a bath con- improved ductility and is used for jewellery. taining 0.0001M to 0.1-0.5M (saturated) Pd, an alloying metal from Pt, Rh, Ir, Ru, Au, Ag, Cu, Ni, Co, G,and Mn, an akylhydroxyamine as complex- ELECTROCHEMISTRY ing agent, and a buffer system. A corrosion resistant coating with high electrical conductivity is produced, Oxygen Generating Electrode for for example, for connector pins. Electromagnetic Propulsion Vessel hi. MUROYA Japanese Appl. 2/77,394 Palladium Electroplating Bath An 0, generating electrode consists of a Ti base AT. & T. BELL LAB. U.S. Patent 4,911,799 marerial coated with at least one oxide of RuO, or A novel electroplating process uses a bath of pH XrO,, on which is a Mn oxide layer. The RuO, 6.0-13.5, containing a Pd source, an alkyl am- and/or IrO, layer promotes the O2 generating reac- monium chloride surfactant with 4-392, and a tion, prevents dissolution of the Ti, and attaches the specified brightener, for example o-benzaldehyde- Mn oxide layer. The electrode has good 0, sulphonic acid. The process is used for electrical con- generating efficiency, is used for electromagneticpro- tact surfaces in contact devices or electrical connec- pulsion vessels, and generates less chlorine, thus tors. The plated films have excellent adhesion and reducing environmental pollution. ductility, are crack-free, have a bright ffish, and show excellent electrical contact and wear properties. Electrochromic Material Containing Rhodium Electroplating Process for Through Hole OSAKA GAS K.K. Japanese Appl. 2186,683 Circuit Boards An electrochromic material consists of a viologen Rh SHIPLEY CO. U.S.Patent 4,919,768 complex prepared by reaction of Rh chloride and A non-conductive body is electroplated by treating

4,4'-dimethyl-2,2'-bi~ridine by heating so that they the surface in sequence with a >0.01 M Sn' + salt dissolve in a solvent such as dimethyl formaldehyde. solution, a 0.00001-1.0 M sulphide solution, a The complex shows an electrochromic phenomenon 0.001-0.01 M Pt or Pd salt solution, and elec- of red coloration to decoloration by electrochemical troplating the resulting surface with Cu or solder. oxidationlreduction. Erosion Resistant Coating with Platinum Electrolysis Electrode Manufactured Layer Using Ion-Beam Mixing AVCO COW. US.Patent 4,919,773 LIMES K.K. Japanese Appl. 2188,785 A coating used to impart erosion resistance to a An electrode is manufactured by using an ion-beam stainless steel or Ti alloy substrate has 3 layers: a duc- mixing method to form an amorphous alloy layer con- tile barrier layer of e.g. Pt of 0.1-1.5 mils thickness, sisting of at least one Fe group element, at least one a layer of pure metal selected hmGroups 111-VI of platinum group element, and at least one of Ti, Zr, thickness 0.2-1.5 mils, and a layer of a bride, car- Nb and Ta, on the surface of a metal substrate, and bide, oxide or nitride element from the above Groups treating the alloy fhwith acid. This provides an of thickness 0.2-2.5 mils. The coating may be used electrode material with an irregular surface suitable for components of a gas turbine engine, and gives im- for electrolysis of brine water. proved erosion resistance without degradation of the mechanical properties of the substrate. Activating Titanium Anodes for Electrochemical Processes Addition of Palladium Solution to Copper VEB. CHEM. BITTERFELD Plating Liquid East German Patent 273,364 TOYAMA NIPPON DENKI Japanese Appl. 2/70,069 A Ti anode is activated by andsing in an electrolyte A Pd solution is added quantitatively to a Cu plating containing sealing components, fluoride and liquid extracted into a reaction cell, while the Cu ion 0.01-2.0 molfl Ru chloride. Oxidising is by spark concentration is measured continuously by col- discharge under a direct voltage of 10-200 V, follow- orimeter. This determines the time period until the ed by optional treatment with platinum group metal concentration reaches a set value, and a deficient chlorides, and tempering. amount of stabiliser is added to the plating bath.

Platinum Metak Rev., 1991, 35, (l), 47-56 47 Ground Coating Conductive Paint Gas Sensor with Stable Properties Composition FIGARO GIKEN K.K. Japanese Appl. 2128,548 SUMITOMO METAL MINI K.K. A gas sensor has a heat resisting insulating substrate, Japanese Appl. 2186,665 a RuO, heater and a metal oxide semiconductor A paint composition contains 50-80 wt.% metallic membrane, with a region of potential graduation bet- powder which is either Ag powder or a mixture of ween the RuO, heater (low potential) and the mem- 90-99 wt.% Agpowder (0.5-3.0 prn) and 10-1 wt.% brane (high potential). Contamination of the metal Pd powder (up to 0.3 pm), acid-proof glass powder, oxide semiconductor with alkali metal ions such as PbOIZnOIB,O,/SiO1 glass powder, and an organic Na by migration from the RuO, heater can be vehicle. The composition is used prior to metal prevented, and stabilised characteristicsare maintain- plating on the terminal electrodes of laminated Pb ed for a long time. perovskite capacitors of the sintered type. Responsive Oxygen Sensor with Thin- Two-Tone Coloured Metal Plating for Film Platinum Electrode Watch Casings TANAKA KIKINZOKU KOGYO Japanese Appl. 2138,964 CASIO COMPUTER CO. LTD. Japanese ApPl. 2/111,537 A solid electrolyte type thin-film 0, sensor has a A two-tone coloured metal plated synthetic resin pro- porous thin-fdm Pt electrode formed from an organic duct is prepared by coating the surface of a moulded Pt ink and a thin-fdm zirconia solid electrolyte form- synthetic resin product with an underplating metal, ed from an organic Zr ink. The organic Pt ink con- plating with Pd metal, plating with Au metal, partly sists of 20% Pt resinate, 3% Bi resinate, 1% Pb masking the Au layer, releasing the unmasked Au resinate, 2% Si resinate, 1% Sb resinate, 53% gum layer to expose Pd, and releasing the mask to reveal rosin, and 20% terpineol. A small-sized inexpensive, the Au plated portions. This method has high plating and highly responsive 0, sensor is obtained. workability, and is used for making aesthetic watch casings. Adsorbing Plate for Collection of Improved Rhodium Deposition on Discs Evaporated Platinum Particles TANAKA KIKINzOKU KOGYO Japanese Appl. 2183,291 AUTOM. ELEMENT CONS. Russian Patent 1,507,878 When melting ferrite blocks or rods in a Pt or Pt alloy Improved Of with enhanced crucible for growing a ferrite single crystal, a pt or pt uniformity is achieved a unit a drive alloy adsorbing plate is placed the crucible at for lifting and lowering the disc, a shaker mechanism a lower temperature, and evaporating from the and a vibrator attached to rigidly tied screens. The pt crucible is The amount of Pt particles gives Rh film On working floating in the grohfurnace environment is reduc- faces of discs, and eliminates coat porosity. ed, giving rise to a very pure ferrite single crystal. APPARATUS AND TECHNIQUE Platinum Crucible for Preparation of Sample Glass Bead Carbon Monoxide Gas Sensor with NIPPON STEEL CORP. Japanese Appl. 2183,431 Platinum Coils A sample for use in fluorescent radiation is prepared SEIKO CO. LTD. European Appl. 358,925A by fusing a powdery sample in a Pt crucible to form A catalytic combustion type CO gas sensor includes a glass bead. Oxidant, sample, flux, and separating a gas sensitometer to determine the CO concentra- agent are put in the Pt crucible, oxidised at tion, based on the dXerence in resistance of two Pt 800-9OO0C for 5-15 minutes, and fused at coils on the catalytic combustion of CO, one in the ac- 1050-1200OC for 3-10 minutes. The glass bead can tive section and the other in the compensating sec- be prepared automatically in a short time, and can be tion. The device has low cost, high reliability and analysed with high accuracy without damaging the Pt provides easy handling, and may be used to detect crucible. CO emitted from domestic gas appliances due to in- complete combustion. Enzyme Sensor with Precious Metal Substrate Rapid Oxygen Sensing Device TERUMO CORP. Japanese Appl. 2187,056 NAT. AERO & SPACE ADMIN. U.S. Patent 4,911,890 An enzyme sensor has a conductive substrate of Ir, A device for sensing the amount of molecular 0, in Ru or Pd-oxide, Pt or Au, preferably in thin mem- a gas includes a heated ceramic electrolyte disc coated brane shape, and an enzyme fmed membrane. The with Pt electrodes, which generates a voltage output enzymes, for example glucokinase, are obtained from proportional to the partial pressure difference of the a thermophilic organism and can be grown at, and do 0, in the product gas and the reference air. The not lose activity at >40°C, so heat and solvent amount of 0 in a combustion product gas is quickly resistance are improved, and life is extended. The sensed, to control the amount of 0, in the gas, in sensor can be easily used in mass production pro- order to maximise efficiency and minimise pollution. cesses, and storing is easy.

Platinum Metals Rev., 1991, 35, (1) 48 Apparatus for Determination of Acid JOINING Concentration in Fluids SUMITOMO ELEC. IND. K.K. Brazing Alloy for Joining Superalloy Japanese Appl. 21122,249 Metals Apparatus used for determination of acid concentra- GTE PRODUCTS COW. U.S. Patent 4,839,141 tion in fluids consists of a measuring vessel, a A brazing alloy with good gap fding and high graphite anode, a Pt cathode, a DC current supply temperature properties consists of 15-35 wt.% Pd, unit, and a conductivity measuring unit. The acid 5-30 wt.% Au, 10-30wt.% Ni, 20-48 wt.% Cu, and concentration can be found with high sensitivity. The 5-25 wt.% Mn, and has a brazing temperature of apparatus is easy to handle, has good chemical 1025-1O8O0C, a solidus temperature above 1000°C resistance, and corrosion and breakdown of the elec- and a liquidus temperature above 1018OC. The braz- trodes do not occur. ing alloy is used in joining superalloy metals. Long Life Gas Concentration Sensor FUJIKURA CABLE WORKS K.K. HETEROGENEOUS CATALYSIS Japanese Appl. 21126,149 A gas concentration sensor with long life consists of Production of a Hydrocarbon White Oil porous Pt electrodes on either side of a solid elec- UOP European Appl. 360,010A trolyte plate, with a cap covering the electrode and forming an internal chamber between the electrode A hydrogenation catalyst, consisting of 0.05-5 wt.% and partition. Each electrode has a porous protective of a platinum group metal on a refractory oxide support, is used in the production of a hydrocarbon layer which is a mixture of AI,O, and Au. The white by hydrogenating a feed stream of 15-30C Al ,0 , has a good Au adsorption, hence there is no oil decrease in electrode efficiency, and the electrodes hydrocarbons obtained from an aromatic alkylation are protected from SO,. process. A white oil product is obtained. Sensor for Controlling the Level of Novel Catalyst for Ally1 Acetate Liquid Coolant Preparation VEB. HOCHVAK DRESDEN East German Patent 274,757 SHOWA DENKO K.K. European Appl. 361,484A The level of low boiling point liquid is controlled by A novel catalyst for ally1 acetate manufacture consists a Pt resistance wire resistor covered with a ceramic of a carrier impregnated with 0.3-1.0 wt.% Pd, layer, which is sealed inside a poor heat conducting 0.2-1.0 wt.% of Cu, Pd, Rh andlor Ru, and an alkali protection tube. A heating current of 50-90 mA is metal acetate. The catalyst is used for the gas phase applied to the Pt resistor which is part of a reaction of propylene, acetic acid and 0, at Wheatstone bridge unit. The sensor can distinguish 140-17OoC and 2-10 atm, giving high relative activi- between liquid or gas which avoids false recordings, ty and selectivity, long life, and enabling a lower reac- and is used to control the level of liquid coolant, tion temperature to be used, which reduces the especially liquid N, . corrosive effects of the acetic acid. Higher Quality Selective Electrode for Hydrogen Production by Shift Reaction Lactose Determination Process AS. LITH. BIOCHEM. INS. Russian Patent 1,502,995 IMPERIAL CHEM. INDS. P.L.C. An electrode with increased selectivityfor determina- European Appl. 361,648A tion of lactose consists of a Pt electrode coated with Catalysts showing good activity for the shift reaction a 5/un thick separating membrane, and then with a process contain a metal such as Pd and preferably an bi-enzyme membrane containing co-immobilised alkali metal oxide or an alkaline earth metal oxide. A glucooxidase and 0-galactooxidase, with a H, containing gas stream is produced from a car- microporous fhon top. The current is measured bonaceous feedstock by forming a gas stream contain- versus a reference electrode, giving a linear current ing H,, CO and steam at >7OO0C, cooling to versus lactose content relationship up to 3.0 mM of 55O-65O0C, passing over the Fe-free catalyst (no lactose. methanation activity) to catalyse the shift reaction, and cooling to <500°C. Carbon Monoxide Thick Film Sensor D.-W. LEE South Korean Patent 8912,572A Platinum Hydrogenation Catalyst for A CO thick film senwr has a diffused resistor layer Preparation of Photostabilisers deposited between the Si base plate and Si02 layer, CIBA GEIGY A.G. Eumpean Appl. 363,318A with vacuum deposited electrodes on the layer, an The preparation of 2-(2-hydroxrphenyl)-2H- auKiliary layer coated above the electrodes, followed benzotriazoles is carried out by catalytic hydrogena- by the CO sensing layers and electrodes formed in se- tion of a nitrobenzene (2-azo-2) phenol compound in quence. The CO sensing material consists of 0.3-0.7 the presence of a supported 0.1-3 wt.% Pt wt.% of Pt and 99.3-99.7 wt.% of Ti02 or ZnO. hydrogenation catalyst and an organic amine.

Platinum Metals Rev., 1991, 35, (1) 49 Platinum Based Knitted Fabric Catalyst Catalytic Removal of Carbon Monoxide JOHNSON MAmYP.L.C. European Appl. 364,153A and Hydrocarbons from Waste Gases A knitted precious metal fabric for use as a catalyst JOHNSON MA~YINC. World Appl. 90/5,579A consists of a metal from the platinum group, Au and A catalyst having good activity, durability, long life Ag; particularly Pt or Pd. The fabric is made by knit- and resistance to S oxides consists of 0.005-2 wt.% ting the metal fibre with a supplementary fibre which Pt,Pd,Rh,Ir,Osand/orRuonaSiO,,ZrO,,TiO,, is later removed. The fabric is used as a catalyst for zeolite and/or a-Al, 0 support mated, which may NH, oxidation, and results in increased conversion be applied to a ceramic or metallic monolith. The efficiency-90 to 95% compared with 90% for a con- catalyst is used below 5OOOC in an oxidising at- ventional material-when tested in an NH, oxidation mosphere to treat waste gas from engines burning reactor at medium pressure. fossil fuels, and gives above 90% conversion for CO and above 50% for C,H,, C,H, and so on. Catalytic Production of Hydrogen Peroxide in an Aqueous Medium Preparation of Mixture of AT-. European Appl. 364,374A Paraphenylenediamines A catalytic process for production of H,O, involves MONSANTO CO. US.Patent 4,900,868 reacting H, with 0, at above atmospheric pressure in Preparation of a mixture of 2 or more different an aqueous medium fke from organic compounds N,N'-disubstituted paraphenylenediamines is by and containing a platinum group metal catalyst, reductive alkylation of a Ncontaining compound especially Pt or Pd. The aqueous medium is fmt con- such as 4-Ntrodiphenylamine, with 2 or more ketones tacted with HI, and then with 0,. The process is safe in sequence, in the presence of HI and a Pt/C to opeate, allows any chosen proportions of HI and catalyst. The cost effective, mixed ketone process is 0, to be used, and allows unused HI and 0,to be problem-free; a single ketone is recovered, a desired recycled. ratio of paraphenylenediamines is achieved, and less ketone is hydrogenated to alcohols. Laminated Combustion Catalyst Element GENERAL ELECTRIC co. European Appl. 370,244A Preparation of Polymethylene in High The element has a metal alloy substrate, an oxidation Yield resistant layer of Pt, Pd or Ru <0.0001 inches thick, U.S. DEFT. OF ENERGY U.S. Patent 4,904,700 and an Al,O, washcoat layer containing Pt, Pd, Rh Polymethyleneis prepared by contacting a H,/CO or or metal oxide as combustion catalyst. The element waterKO mixture in a solvent with catalyst slurry of can be used in an oxidising atmosphere at high at least 1 wt.% Pt and/or Pd on a support having a temperatures for an extended time, for example at deposit of Fe. The catalyst can operate under mild 1800-2500°F, with a service life up to 8000 h. It is pressure and temperature conditions (100-300°C), used as a combustion catalyst to reduce exhaust emis- and can be used in slurry form with dilute reactant sions from gas turbines. concentrations to obtain high yields of the product. The polymer materials produced are useful as diesel Three-Way Catalyst with Suppressed or jet fuels. Hydrogen Sulphide Emissions NIPPON SHOKUBAI KAGAKU One Step Preparation of 2-Pyrrolidone European Appl. 372,156A PHILLIPS PETROLEUM CO. U.S. Patent 4,904,804 An exhaust gas purifration catalyst consists of ac- Preparation of 2-pyrrolidone is effected by contacting tivated Al,O supporting 5-30 wt.% Pt and/or Pd, a 1-10 molar excess of NH, with succinic acid or 1-20 wt.% Rh, Ce oxide, activated M,O,, and op- anhydride and HI,in the presence of at least one tionally an alkali metal and/or Ni oxide; all coated on diluent and a PdAl, 0, catalyst, with a molar ratio of a honeycomb monolith carrier. The catalyst removes succinic acid or anhydride:Pd of 1- IOOO. Reaction is CO, hydrocarbons and NOx from the exhaust gases at 200-30O0C and at least lo00 psig for 0.5-18 h. of vehicle engines, while suppmsing HISemissions. The process enables a one step preparation of 2-pyrrolidone in higher yields than prior art Palladium Catalyst for Hexamethylene processes. Imine Preparation DU PONT DE mourn Co. European Appl. 372,492A Catalyst Panels for Stationary Power A gaseous mixture containing hexamethylene Plant Exhaust Purification diamine vapour, water vapour and H, is contacted W. R. GRACE CO. U.S. Patent 4,916,001 with a solid catalyst of 0.1-10 wt.% Pd on M,O, Removal of pollutants from the exhaust of spheres, at 160-260% and 0-100 psig, to prepare hydrocarbon-fuelled power plants is achieved using hexamethylene imine. The mixture may also contain rectangular unitised monolithic honeycomb catalyst at least one of NH,, CH, or N, which are believed panels, with a catalyst of Pd-V,O, on A120,-Zr0,. to increase catalytic activity. High conversion of the Less structural material is required in the panels, diamine and high yields of the hexamethylene imine which allows more catalyst to be exposed to exhaust are obtained in the process. gas, and reduces the pressure drop through the unit.

Platinum Metah Rev., 1991, 35, (1) 50 Three-Way Automotive Exhaust Catalyst Hydrocarbon Reforming Process with W. R. GRACE CO. U.S.Patent 4,916,105 Dual-Zone Catalyst The catalyst has a substrate, to which is applied a UOP U.S.Patent 4,929,332 washcoat slurry Consisting of water; 0.2-7 wt.% of a Gasoline range hydrocarbons are reformed in two se- metal ferrite of formula MFe,O, where M is Co, Ni, quential catalyst zones; the fmt having a catalyst Cu, Zn, Mn or Fe; and 20-50 wt.% of catalysed composite with 0.01-2 wt.% Pt, 0.05-5 wt.% Ge, Al,O, having 0.1-7.5 wt.% Pt, Pd and/or Rh (in- Al,O, and a Cl component, and the second catalyst dividually not above 2.5 wt.%), and 0-50 wt.% rare composite having the same components, plus a pro- earths; followed by drying and calcining. The catalyst moter from Rh, Ir, Ru, Re, Co andlor Ni. This controls emissions of hydrocarbons, CO and NOx, system gives improved yield of petroleum aromatics and virtually eliminates H,S, while containing a or gasoline products compared with a single catalyst minimal amount of Ni. system. Catalyst for Methanol and Formaldehyde Palladium Catalyst for Dimerisation of Vapour Oxidation Aromatic Halogen Compounds FORD MOTOR CO. US.Patent 4,919,903 MITSUBISHI KASEI cow. Japanese Appl. 2153,742 A dispersed catalyst consisting of Pd with Rh andlor Aromatic halogen compounds having one or more CeO, at a Rh:Pd wt. ratio of 0-0.3 and a Ce0,:Pd halogen atoms on aromatic ring carbon(s) are dimeris- wt. ratio of 0-50, is used for complete oxidation of ed by heating at 20-250°C, under ordinary pressure CH,OH andlor HCHO vapour at 85-20O0C, in the of 100 kglcm’, with reducing agents, halogen ab- exhaust from a CH,OH fuelled I.C. engine calibrated sorbents, surfactants, water, and a supported Pd for stoichiometric &fuel mixtures. Gases having catalyst present at 0.1-30 mg Pd per mol of starting 0.01-1% CH,OH vapour and 0.001-0.05% HCHO material. Aromatic dimers are used for various vapour are more efficiently converted than by prior- chemicals, for example, 3,4,3’,4’-biphenyl- art AglCeO, catalysts. tetracarboxylic acid is useful for polyimide resins. Platinum Catalyst for Preparation of N- Noble Metal Three-Way Catalyst with Alkyl-Aniline8 Zeolite Layer CIBA-GEIGY COW. U.S. Patent 4,92 1,980 TOYOTA JIDOSHA K.K. Japanese Appl. 2156,247 N-alkyl-anilines are prepared by reacting an aniline A three-way catalyst consists of a support having a with an alcohol in the presence of H, and a catalyst zeolite coating, and an Al, 0, coating loaded with (for at 150-3OO0C and 0.5-6 bar pressure. The catalyst example) 1.5 gA Pt, 0.3 gA Rh, 0.03 molA La, and 0.3 consists of 0.2-10% Pt, 0.05-3% of a Group Ia molA Ce. The catalyst is used to remove hydrocar- andlor IIa metal compound, and at least one other bons, CO and NOx hmcombustion exhaust, and compound on a SiO, gel carrier. The reaction can be can remove hydrocarbons with higher efficiency at continuous and gives high conversion and selectivity. lower temperatures, even from fuel-rich combustion exhaust, by the action of the zeolite embedded in the Platinum or Palladium Catalyst for Wax catalyst. Isomerisation EXXON RES. & ENG. CO. U.S. Patent 4,923,588 Preparation of Carbamic Acid Esters A wax isomerisation catalyst consists of Pt or Pd and BABCOCK-HITACHI K.K. Japanese Appl. 2156,458 0.1-1.5 wt.% fluoride on an AI,O, or &o,- Carbamic acid esters are prepared by reaction of containing support in the form of 1120 inch trilobes. amines or amino acids with COYorganic nitro com- Waxes are isomerised into hydrocarbons by passing pounds and organic hydroxyl compounds, at over the catalyst in the presence of HI. The method 60-23OoC, using a catalyst of Pd, Rh or Ru on SO, is used for conversion of slack waxes from dewaxing or Al,O, and an aqueous solution of hydrogen hydrocarbon oils, or synthetic waxes from the halides. The esters axe prepared under mild condi- Fischer-Tropsch process into liquid hydrocarbons tions, in high yield, without using phosgene, and are boding in the range 37O+OC. useful for pesticides, isocyanates, and so on. Less catalyst is used and it is readily recovered. Naphtha Reforming to Improve Gasoline Octane Value Combustion Equipment with Two Types UOP U.S. Patent 4,923,595 of Rhodium Catalyst Naphtha is reformed by contact with H, and a TANAKAKIKINZOKU KOGYO Japanese Appl. 2157,808 catalyst consisting of an Al,O, support with 0.05-1 Fuel such as town gas is fed into combustion equip- wt.% Pt, uniformly dispersed; 0.1-2 wt.% Ge, Pb or ment having an upstream catalyst with 5-50 nm grain Sn, uniformly dispersed; 0.1-2 wt.% Rh, Ir, Ru, Co diameter Rh, and a downstream catalyst having Rh of or Ni, which is surface impregnated; and 0.5-1.5 0.05-2 pn grain diameter and 0.1-10 wt.% Ce to wt.% Cl. The catalyst has dual hydrogena- prevent Rh deactivation, with the catalyst dispersed uoddehydrogenation and cracking functions, and is on a stabilised-oxide coated support. The upstream highly active, selective and stable. catalyst promotes improved ignition performance.

Platinum Metak Rev., 1991, 35, (1) 51 Exhaust Gas Purification Catalysts Exhaust Pdication Catalyst with No MITSUI MINING & SMELTING Hydrogen Sulphide Generation Japanese Appl. 2174,530 TOYOTA JIDOSHA K.K. Japanese Appl. 21107,334 Exhaust gas purification catalysts with good catalytic An exhaust gas purification catalyst consists of Pt, Pd properties are prepared by immersing ceramic sup- or Rh supported on a metal oxide layer where Ce ox- ports in Pt salt solutions prepared by adding ide exists on the surface of Al,O, and a Ni-Ba com- dinitrodiamino Pt to a HNO, solution, under posite oxide, with the oxide layer formed on a heat pressure at 10O-16O0C. The Pt salt solutions are ad- resistant substrate. The catalytic activity of the Ni is sorbed efficiently on the supports and then reduced. increased, and H, S generation is prevented. In an example the catalyst showed 98%, 100% and 97% Oxidation Catalyst for Exhaust removal of hydrocarbons, CO and NOx, respectively. Purification MATSUSHITA ELEC. IND. K.K. Ruthenium Catalysts for Preparation of Japanese Appl. 2175,348 Perfumed Products The catalyst consists of a honeycomb structure, a KAO CORP. Japanese Appls. 21108,642 and 21121,938 perovskite structure composite oxide of formula Catalysts consisting of 5 or 7% Ru on active C are us- ABO, where A is at least one of La, Ce and Sr, and ed in hydrogenation reactions for the production of B is Co andlor Ni, mixed with an inorganic binder, (a) 2-cyclohexylpropanol from 2-phenylpropanol or and at least one of Pt, Pd and Rh. The catalyst carrier 2-phenylpropanal, or (b) a substituted produced has a larger surface area, enabling the cyclopentane-2-01 from the corresponding catalytic substance to be homogeneously dispersed cyclopentane-2-one. A basic aqueous solution of pH and tightly held. The catalyst is used to oxidise CO 8.0-10.5 is added to the reaction medium or is used and hydrocarbons in exhaust gas to CO, and water. to wash the Ru catalyst. Product (a) can be used as a perfume and can be obtained in high yields, while Particulate Oxide Catalyst Filter for product (b) has a woody odour, and can be produced Diesel Exhaust industrially in high yields, in a short time. SAKAI CHEMICAL IND. K.K. Japanese Appl. 21102,315 A particulate oxide catalyst filter is obtained by sup- Platinum-Loaded Catalyst Supports for porting Pt, Pd, Mn oxide, Cr oxide or Fe oxide on a Combustion thin metal netting or plate which may be of stainless TANAKA KIKINZOKU KOGYO steel, and has many small holes of diameter230 pm. Japanese Appl. 211 15,040 Waste gas from diesel engines is forcibly passed Catalyst supports for combustion are prepared by im- through a number of fdters; particulates are stably removed over long periods, and increase in mersing Al, 0, fibre laminated supports in an HNO, an solution of dinitrodiamine to which reducing agent pressure loss of the filter is prevented. Pt is added, fhgPt, drying and firing. Small Pt particles are loaded uniformly on the catalyst supports, Three-Way Catalyst with Improved which can be used for burners in which gas fuels or Durability vaporised liquid fuels are burnt at low temperatures. TOYOTA JIWSHA K.K. Japanese Appl. 21102,735 A catalyst for purification of exhaust gas consists of Production of Hydrogen-Containing Gas a heat resistant carrier coated with an Al,O, layer for Car Fuel containing Pd-Nd and Rh-La composite oxides obtained by coprecipitating Pd-Nd and Rh-La, respec- MITSUBISHI HEAVY IND. K.K. Japanese Appl. 2/116,603 tively. The catalyst is used for simultaneous removal of CO, hydrocarbons and NOx from car exhaust H,-containing gas is produced by reacting CH,OH gases, and has improved activity and durability, with 0,-containing gas at 100-6OO0C, using a resulting in effective utilisation of the noble metals. catalyst of Pt andlor Pd on a support preferably containing 10-98 wt.% of rare earth element oxides, for selected from La,O,, GO,, Nd,O, or mixtures. Rhodium Solutions Exhaust Catalyst The gas can be produced at low temperature, with Preparation good selectivity, and stability over a long time. CATALER KOGYO K.K. Japanese Appls. 21102,736-37 Rh-containing solutions are prepared by mixing Rh Production of Nucleosides hydroxide crystals with either (a) weak basic nitrates selected from ammonium nitrate and rare earth metal AJINOMOTO K.K. Japanese Appl. 211 17,689 nitrates, or (b) a wate soluble organic acid having at Production of 2f,3f-dideoxynucleosidesis effected by least one carboxyl group, and dissolving in HNO,, converting a nucleoside into an intermediate com- crystallising the HNO, solution, and dissolving the pound, and then reducing in an aqueous organic sol- resultant crystals in water or HNO,. The Rh solu- vent in the presence of a Pd catalyst and a base, under tions are used to prepare waste gas purification an atmosphere of H, . The products are prepared in catalysts, with higher efficiency. high yield with high selectivity using this process.

Platinum Metals Rev., 1991, 35, (1) 52 Curable Fluorosilicone Composition Homogeneous Rhodium Hydrogenation SHINETSU CHEM. IND. K.K. Japanese Appl. 21123,163 Catalyst A curable fluorosilicone composition consists of 100 RANBAXY LAB. LTD. US. Patent 4,902,447 parts wt. of an organopolysiloxane, an a-6-Deoxytetracycline derivatives are prepared by organohydrogensilox, 0.01-10 parts wt. of hydrogenation of substituted methylenetetracyclines another organopolysiloxane, and a catalytic amount in the presence of a bis(tripheny1phosphine)(hydrox- of F't, Pd or Rh series compound. The composition ylamine hydrohalide) dichloro Rh catalyst. The pro- has high heat resistance, and is used for potting and ducts are obtained in high yields and purity, and coating of elecmc and electronic parts. include the known antibiotic doxycycline. The process is more economical than known processes as less Preparation of Aromatic Urethanes Rh is used for the catalysts. SUMITOMO METAL IND. K.K. Japanese Appl. 211 24,865 Preparation of a-Phenyl Propionic Acid Aromatic urethanes are prepared by reaction of an Derivatives aromatic nitro compound with CO and a hydroxy- DAICEL CHEM. IND. K.K. Japanese Appl. 2148,544 containing organic compound, in the presence of a Pd a-Phenylpropionic acid derivatives are prepared by or Ru catalyst fmed in a reactor, a Lewis acid pro- reacting an a-phenylethyl alcohol derivative with CO, moter such as FeC12, and a N-containing at 30-130°C, in a mixture of a hydrocarbon and an heteroaromatic compound as ligand. Aromatic a-phenylpropionic acid derivative, in the presence of urethanes can be prepared without use of phosgene, a Pd, GI or Ni compound as catalyst, and preferably without recovery, drying and reactivation of the a cocatalyst such as I, HI, or alkyl iodide. The pro- platinum group metal, and with little metal loss. ducts have analgesic, anti-inflammatory and anti- pyretic activities, and can be produced in high yield Ammonia Converter with Increased by this process. Reliability TEKHENERGoKHIMPROM.TEKHENERGOKHIMPROM. Russian Patent 1,493,3031,49333 Prepmation of Indole-Carboxylic Acid An NH -air mixture isis fedfed toto an NH converter hav- Esters ing a vertical cylindrical body and containing a Pt kg a vertical cylindrical and a Pt NIPPON STEEL QIEM. K.K. Japanese Appl. 2/73,060 catalystcatalyst mesh.Illesh' Oxides ofOf nitrogen areare formed, which Indole-7-carboxy~cacid esters are prepared by reac- areare fmedfmed by cooling,cooling, and used toto make dilute HNO, with increased reliability. tion of dihydro-indolyl thallium bis-trifluoroacetate with increased reliability. with CO in a lower alcohol in the presence of Pd acetate. The indole esters are useful as intermediates in the preparation of drugs and agrochemicals, and HOMOGFJEOUS CATALYSIS can be Droduced from indolines in high yield and Visible Radiation Activated regiospe&cally by this short process. Hydrosilylation Reaction Palladium Catalyst for Preparation of MINNESOTA MINING MFG. CO. European Appl. 358,452A Indole Compounds NIPPON STEEL CHEM. K.K. Japanese Appl. 2173,061 A hydrosilylation process comprises reacting an unsaturated aliphatic compound and a composition con- Indole compounds are produced by reacting a taining at least one Si-bonded H in the presence of a halogeno-indole with an olefin in the presence of Pt complex and a sensitiser. The sensitiser absorbs 0.3-50 mol.% of a Pd catalyst such as Pd acetate or visible light on exposure and transfers energy to the Pd chloride, a uiarylphosphine and a base. The reac- (qs-cyclopentadienyl) tri (u-aliphatic) Pt complex SO tion is carried out in a solvent at 8O-14O0C, for that reaction is initiated. The method is used for visi- 0.5-48 h. The process produces indole compounds ble light curable impression material for dental ap- easily with low cost; which are useful as a starting plications, and enables use of a heat-sensitive material for pharmaceuticals or agrochemicals. substrate, and safer visible radiation. Rhodium Complex Catalyst for Selective Alkadienol Production with Recirculating Preparation of Silanes Palladium Catalyst TOSHIBA SILICONE K.K. Japanese Appl. 2196,583 MITSUBISHI KASEI cow. European Appl. 361,304A Aminoalkylalkoxysilanes us& as glass-plastics Alkadienols are produced by reaction of a conjugated binders are prepared by reaction of silane compounds alkadiene and water in the presence of CO, and a with allylamines in the presence of a Rh complex catalyst consisting of a Pd compound and a phosphine catalyst having N andlor S containing heterocyclic or phosphite. The method efficiently separates high compounds as ligands. The products are prepared boiling point by-products from the Pd catalyst, which selectively using the Rh complex catalyst, which can is then recirculated into the reaction system with be prepared readily from the Rh complex and ligands higher activity. Alkadienols are produced, which are in situ. An example of the Rh complex is hydrated dimers of a conjugated alkadiene. bis( 1,5-cyclooctadiene) Rh(1) tetrafluoroborate.

Platinum Metals Rev., 1991, 35, (1) 53 Palladium Catalyst for Preparation of FUEL CELLS Polymerisable Monomers MITSUI PETROCHEM. IND. K.K. Amorphous Alloys as Reversible Japanese Appl. 211 11,767 Hydrogen Storage Media Preparation of 1,3-dioxolen-2-0ne derivatives is by STANDARD OIL CO. (OHIO) U.S. Patent 4,923,770 hydrogenation of 4,5-dihalo-l,3dioxolan-2-one Amorphous alloys for reversible H, storage contain derivatives at 2O-7O0C, under atmospheric pressure Pt, Ag andlor Hg; Ru, Fe, Ni, Al, Co, Mo, Mn to 10 kglcm' ,in the presence of a Pd catalyst (Pd at and/or others; and Zr, Ti, Cd,Ca, Mg and/or others. 0.1-3 wt.% of starting material), aliphatic tertiary A reversible H, storage electrode for use in alkaline amines and alkali metal compounds. or acid electrolyte can be formed using the alloy as a thin film or powder on a Ti or Ta substrate. The Palladium Complex Carbonylation alloys can be repeatedly cycled without becoming em- Catalyst brittled or phase separated, oxidised or corroded. NIPPON PETROCHEM. K.K. Japanese Appl. 21117,636 A mixture of two or more unsaturated hydrocarbons Methanol Fuel Electrode Catalyst is reacted with CO and water or a lower alcohol at Containing Platinum and Ruthenium 40-25OoC, with 10-600 kg/cmz of CO pressure, in MATSUSHITA ELEC. IM). K.K. the presence of a carbonylation catalyst such as Japanese Appl. 215 1,865 bistriphenylphosphine dichloro Pd. Selective A new method for preparing a catalyst for the hydrocarboxylationor hydroesterificationof the vinyl CH, OH fuel electrode of a fuel cell involves attaching radical produces a-aryl propionic acid derivatives or highly dispersed Pt and Ru on C fine particles. their esters, which are intermediates for production Suspended, highly dispersed C fine particles are of a-(4-isobutylphenyl) propionic acid (Ibuprofen). ultrasonically blended into a colloidal liquid containing dispersed Pt and Ru, and then the catalyst par- Platinum Group Metal Hydrogenation ticles are filtered, washed, dried, and heat treated at Catalysts 200-5OO0C in air. An electrode with improved CENTRAL GLASS K.K. Japanese Appl. 2/121,952 capability can be prepared by a simplified process. Halomethyl-nitrobennes undergo fluorination and hydrogenation by reaction with HF and H, in the Electrocatalyst for Methanol Fuel Cells presence of a hydrogenation catalyst, to give the MATSUSHITA ELEC. IND. K.K. 4-fluoroaniline derivative. The catalyst may be Pt, Japanese Appl. 211 11,440 Pd, Rh, Ir, 0s or Ru in the form of metals, oxides, An electrode catalyst for use in fuel cells is prepared halides or hydroxides. The reaction yield and by supporting noble metal particles (including Pt) on position-selectivityare high, giving products useful as a C powder support using an alcohol as reducing intermediates for bactericides, herbicides and agent, and 5-10% H,O, as reaction promoter. The medicines. catalyst can be used for a CH,OH fuel cell, in which case Pt and Ru are solid-meltedto give an alloy on the Improved Preparation of Phthalides C, giving improved CH,OH oxidation potential. MITSUBISHI KASEI COW. Japanese Appl. 2/121,976 Phthalide(s) are prepared by hydrogenation of Combustion Catalyst for Fuel Reformer aromatic ortho-dicarboxylic acid(s) or their FUJI ELECTRIC MFG. K.K. Japanese Appl. 2/111,601 anhydride(s) in the presence of a catalyst of Ru, A fuel reformer has parallel tubes with a reforming organophosphines, and conjugated bases. The catalyst such as a Ni system on the inner face and a phthalides are prepared under mild conditions in combustion catalyst such as Pt or Pd on the outer high and steady yield (60-90%), and are useful as in- face. In the reformer natural gas and CH,OH are termediates for naphthalenes, anthracenes and cer- reacted with steam, and H -rich reformed gas is pro- tain alkaloids. The catalyst does not cause corrosion duced for use in a fuel cell. of the apparatus and shows steady, high activity for a long time. GLASS TECHNOLOGY Hydrogenolysis of Carbonyl Protective Groups on Peptides Platinum Bushings for Glass Fibre BERLIN CHEMIE VEB. East German Patent 274,822 spinning Carbonyl protecting groups on amino acid and pep- TANAKA KIKINZOKU KOGYO Japanese AppI. 2197,433 tide derivatives can be removed by hydrogenolysis Bushings for spinning glass fibre or continuous glass without affecting sensitive histidine and tryptophan filament are made of Pt ot Pt alloy, with the bushing components. Hydrogenolysis is in an organic solvent, plate being reinforcedly supported from the under- under a H, pressure of 1.5-50 bar, with a Pd catalyst side by a support of Si,N, having a surface coating present at 1-6 mg Pd per mmol of amino acid or pep- of A,o, or ZrO, fh. This support has high tide derivative; itself present at 200-600 mmolil. material strength and excellent durability.

Platinum MeiaLs Rev., 1991, 35, (1) 54 ELECTRICAL AND ELECTRONIC Oxidation Resistant Rare Earth ENGINEERING Permanent Magnet TOHOKU METAL IND. LTD. Japanese Appt. 2187,502 Corrosion Resistant Permanent Magnet A rare earth permanent magnet consists of a matrix SUMITOMO SPEC. METAL K.K. of a rare earth-Ru-transition metal phase, dispersed European Appl. 361,308A in which is a rare earth-transition metal-B tetragonal A permanent magnet consists of a sintered body of magnetic compound. The magnet is made by 10-30 at.% rare earth metals, 2-28 at.% B and magnetic moulding a starting powder which is a mix- 65-80 at.% Fe, with the surface having a layer of Pt, ture of the magnetic compound and the matrix. Pd, Au and/or Ag, an electroless layer of Ni, Cu, Sn andlor Co,and an adherent electroplated layer of Ni, Fine Ruthenium Oxide Particles for Cu, Sn and/or Co. The magnet has high corrosion Resistance Pastes resistance and stability, showing up to 5% deteriora- TANAKA KIKINZOKU KOGYO tion in properties after 500 h at 80°C and 90% relative Japanese Appls. 2188,431 -32 humidity. Ru oxide fine particles are prepared by neutralising an acidic aqueous solution of Ru chloride with Thin Film Amorphous Alloy aqueous NH, or ammonium solution, and converting MITSUI PETROCHEM. IND. K.K. Ru hydroxide into Ru oxide. The particles obtained European Appl. 364,631A have a spherical shape, and a sharp particle size A thin amorphous alloy film with a perpendicular axis distribution, with 70% having sizes 0.2-0.3 pm, and of magnetisation consists of Fe and/or Co, Pt and/or are used in resistance pastes for thick film circuits. Pd, and at least one other element from specified groups. The fhhas high oxidation resistance, high Ferromagnetic Thin Film for Magnetic reflectance, and excellent magneto-optic properties, Head including high coercive force and large Kerr and HITACHI K.K. Japanese Appl. 2190,505 Faraday angles. A ferromagnetic thin film consists of an Fe-B alloy containing 1 at.%6 A thick). The element gives an increased carrier to noise ratio, and requires less materials and Magnetic Recording Medium with Cobalt- manufacturing time than conventional magneto- Phosphorus-Platinum Layer optical recording elements. MITSUBISHI WE1 CORP. Japanese Appl. 2/108,221 A magnetic recording medium consists of a Co-P type Stable Electrolytic Capacitor Containing magnetic layer which includes 0.01-10 wt.% Pt (with Palladium respect to the Co), on a nonmagnetic substrate. MATSUSHITA ELEC. IND. K.K. Coercivity of the medium is enhanced, and high den- European Appl. 372,519A sity recording can be obtained. A solid electrolytic capacitor includes a dielectric ox- Mat for ide film, a solid electrolyte layer, and a C layer, with Catalyst Coated Plastic Fibre a cathode layer andlor conductive adhesive consisting Screening of a polymer and a Pdcontaining electrically conduc- ASEA BROWN BOVERI A.G. German Appl. 3,840,200 tive powder. By using the Pd powder a small initial Mats for screehhg and dissipating any static charges tan 6 value is obtained which is stable at high are made of nonmetallic fibres, such as plastic fibres, temperatures and humidities, as well as a high which are at least partly coated with a Pd catalyst resistance to short circuit failures. layer and lined with a Cu film 0.1 pm thick by a cur- rentless technique. Thick Film Thermistor Composition DU PONT DE NEMOURS CO. U.S. Patent 4,906,406 Electroconductive Paste for Metallising The composition consists of an admixture of finely Ceramics divided particles of a Ru based pyrochlore and a V.S. KOSTROMAROV Russian Patent 1,485,315 borosilicate glass or glass mixture which has a viscosi- An electroconductive paste contains 48-65 wt.% Pt- ty of 10-10000 poises upon fhg at 700-100OoC. Pd alloy powder, 0.1-1.0 wt.% MnCo,, ethyl Novel compositions have a good temperature range, cellosolve, ethyl cellulose, white spirit, pine oil and a high positive temperature coeffkient of resistance, triethanolamine. The paste is used for metallising and give a wide range of resistance values. non-fired Bi containing ceramic articles.

Platinum Metah Rev., 1991, 35, (1) 55 MEDICAL USES Novel Platinum Compounds with Potent Anti-Tumour Activity Stable Cisplatin Solution for Parenteral TORAY IND. INC. Japanese Appl. 2132,086 Administration New Pt containing compounds may be prepared by BRISTOL-MYERS SQUIB. European Appl. 369,714A reacting a compound such as dinitrato A stable aqueous solution of cisplatin in a sealed con- (1,2-diaminocyclohexane)Pt(II)and an alkali/alkaline tainer contains up to 1 mg of cisplatin and a source earth metal hydroxide with another mmpound. The of chloride ion equivalent to 20-100 mg of NaCl per new compounds exhibit potent anti-tumour action in ml of solution. It contains less aquated Pt species and a test using mice inoculated with leukaemia L1210. is of pH 5-7.5 which is closer to physiological pH than known solutions. The cisplatin can be New Anti-Oncotics with Low parenterally administered and is an important anti- Nephrotoxicity neoplastic agent used for treating metastatic TANABE SEIYAKU K.K. JUpneSe Appl. 2167,217 testicular, ovarium and advanced bladder cancer. New anti-oncotics contain an organoplatinum complex, for example a substituted donate trans- New Platinum Anti-Tumour Agent with L-1,2-diaminqclohexane Pt, as effective compo- High Therapeutic Index nent. The anti-oncotics show good action against S.S. PHARMACEUTICALK.K. European Appl. 376,076A solid tumours, ascites hepatoma and leukaemia; in- A new Pt complex possessing excellent anti-tumour hibit propagation of tumour cells, and extend the sur- activity has 1,2diaminocyclohexaneas a ligand in the vival period of animals with these tumours. The cis, trans-I-, trans-d- or transdl-configuration. The organoplatinum complexes have a wide range of complex may be used in the treatment of genital anti-oncotic effects for various tumours, and low cancer, bladder cancer, or head and neck cancer, and nephrotoxicity. has a high therapeutic index, good water solubility, and may be administered as an anti-tumour agent at Metal Material for Dental Use a daily dose of 1-50 mgkg orally, or 0.5-18 mglkg TOKURIKI HONTEN K.K. Japanese Appl. 21142,710 parenterally. An alloy consisting of 10-25 wt.% Au, 15-35 wt.% Pd, 47-70 wt.% Ag and 0.1-5 wt.% of one or more Polysaccharide Anti-Cancer Agent’ of Sn and In is made into a plate 0.05-0.5 mm thick. Containing a Platinum Complex Fe powder of diameter 0.04-0.8 mm is applied on KURARAY K.K. World Appl. 9013,402A one surface and pressed, and dissolved to make an New derivatives of activated polysaccharides and uneven phase. The material has excellent adhesion their pharmaceutically acceptable salts consist of a strength, processability, support strength and polysaccharide containing -SO,H, -COOH, or - durability, and is used for stabilising teeth with P(0)(OH)Lacidic groups, bound to which are com- mobility and for supplementing front teeth with a plexed (trans-l,2-~yclohexanediamine)Pt groups. defect. The derivatives are anti-cancer agents with a reduced tendency to cause vomiting. New Platinum Complexes with Cytostatic Activity Medical Preparation Prepared Using BEHRINGWERKE A.G. German Appl. 3,834,098 Palladium Complex Catalyst New Pt complexes with a 1,3-diaminopropane YAMASA SHOYU K.K. World Appl. 9015,526A derivative as ligand have cytostatic activity and low A pharmaceutical preparation contains as active com- cytotoxicity. The Pt complexes possess cytostatic ac- ponent a 2-alkynyladenosineprepared by reaction of tivity as shown in “in vivo” tests in mouse L1210 2-bromoadenosine or 2-iodoadenosine with a leukaemia cells, B16 melanoma, and M5076 1-alkyne in the presence of cuprous iodide and reticulum cell sarcoma, and are also effective against bis(tripheny1phosphine)-Pd dichloride. The prepara- resistant tumour cells. tion is used in the treatment and prophylaxis of ischemic disease of the heart and brain. Palladium-Silver Alloy for Dental Use DEGUSSA A.G. German Appl. 3,905,987 Boron-Free Palladium Dental Alloy A Pd-Ag alloy used as a tooth replacement consists of PIERCE & STEVENS CO. U.S. Patent 4,917,861 45-80 wt.% Pd, 7-45 wt.% Ag, 6-2 wt.% Pt, 0-1 A dental alloy having exceptional high temperature wt.% Ru, Ir andlor Re, 0-5 wt.% Au, 0-5 wt.% Sn, strength consists of 50-85 wt.% Pd, 5-40 wt.% of Co 0-5 wt.% In, 0-3 wt.% Zn, 0-2 wt.% Cu, 0-1 wt.% and/or Cu, 1-15 wt.% Ga, up to 5 wt.% of a modifier W, Mo andlor Ta, 0-7 wt.% Ga, 0-5 wt.% Co, and of Ru, Au, Ni, In, Snand mixtures, 0.01-0.05 wt.% 0-3 wt.% Ge. The alloy can be fired with dental of an 0, scavenging component from Ge, Li and mix- ceramics without colouring them. tures, and up to 0.5 wt.% of a grain refmer from Ir, Re and mixtures. The novel alloy can be used for den- The New Patents abstracts have been prepared from tal restorations and has high tarnish resistance. material published by Dement Publications Limited.

Platinum Metals Rev., 1991, 35, (1) 56