Platinum Metals Review

UK ISSN 0032-1 400

PLATINUM METALS REVIEW

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

VOL. 42 OCTOBER 1998 NO. 4 Contents

Platinum Metals Review and the Internet 134 Biphasic Homogeneous Catalysis 135 By Paul 3. Dyson, David J. Ellis and Thomas Welton Progress in Dye-Sensitised Photovoltaics 140 By R. 3. Potter Formation and Decomposition of Palladium Hydride Particles 141 By P. D. Cobhn, B. E. Nieuwenhuys, V. V. Gorodetskii and V. N. Pamzon Carbon Monoxide Sensing Technology 144 By Gavin Troughwn Platinum Labware Catalog 144 Aqueous-Organic Biphasic Catalysis 145 By Paul 3. Dyson The Build-Up of Bimetallic Transition Metal Clusters 146 By Paul R. Raithby Construction of Miniature Organo-Rhodium Boxes 157 Conferences Report Progress in Catalysis 158 By C. F. 3. Barnard and W. Weston; K. E. Simons and A. F. Chafley Combinatorial Chemistry Identifies Fuel Cell Catalyst 163 Catalysts for Butane Reforming in Zirconia Fuel Cells 164 By K. Kendall and D. S. Williams Geoffrey Wilkinson and Platinum Metals Chemistry 168 By M. L. H. Green and W. P. GnfSlth Abstracts 174 New Patents 179 Indexes to Volume 42 183

Communications should be addressed to The Edizor, Susan V. Ashton, Platinum Metals Rev& Johnson Matthey Public Limited Company, Hatton Garden, London ECl N 8EE PLATINUM METALS REVIEW AND THE INTERNET

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Platinum Metals Rev., 1998,42, (4), 134 134 Biphasic Homogeneous Catalysis By Paul J. Dyson, David J. Ellis and Thomas Welton Department of Chemistry, Imperial College of Science, Technology and Medicine. London

Biphasic catalysis is becoming an area of environmentally responsible catalysis, but its development and use have until recently been somewhat neglerted. Here, the basic principles and the design of features going into such systems are explained, and ageneral overview is presented with the intention of encour- aging greater interest in this under utilised technique. Some well-established aqueous-organic regimes are described and there is a discussion of some possible future directions involving ionic-liquidlorganic systems.

There are many benefits to be gained by using then be performed as shown in Figure 1. Here homogeneous catalysis in place of heterogeneous the catalyst resides in solution in one of the two catalysis in organic synthesis, the most notable phases and the substrate resides in the other being the use of less aggressive reaction condi- phase. During reactions, the two layers are vig- tions and increased selectivity. orously stirred, thus allowing suitable interac- The main disadvantages of traditional organic tion of catalyst and substrate. Once the reaction phase reactions employing homogeneous tran- has reached the appropriate stage, the stirring sition metal catalysts are the difficulties asso- is stopped and the mixture of phases separates ciated with separating the catalyst ii-om the prod- into two layers, one containing the product and uct and solvent. Separation techniques, such as the other containing the catalyst. Separation distillation, require an extra expenditure of of the two is then carried out by simple decanta- energy and can, in certain instances, lead to tion and, in principle, the catalyst solution is degradation of both the products and the cat- available for immediate reuse. Clearly, these alyst used. As the catalyst requires extraction biphasic reactions offer a potential answer to before a new reaction run can be performed, the problems mentioned above. the ‘turn around time’ between runs also This type of approach was first used com- becomes a prime factor. mercially for the polymerisation of ethylene These problems coupled with the inevitable (Shell Higher Olefins Process (1)) although in loss of the catalyst species (allowing for some this case the catalyst and substrate are initially imperfection in the separation techniques in a single phase and the product forms the sec- employed) tend to redress the balance between ond, immiscible phase; the principal, however, heterogeneous and homogeneous catalysis. is the same. Clearly, this approach is not One possible solution to these problems is to suitable for many other processes and has thus heterogenise the catalyst and product into two lead to the selection of water as the preferred separate and immiscible phases. Reactions may catalyst solvent for biphasic conditions.

Fig.Fig. 11 AA schematicschematic representation of a two- phase process showing how Reactant Solution Product solution thethe initial initial reactant reactant solution solution andand productproduct solutionsolution areare immiscible with the catalyst Catalyst SoIuticn Catalyst solution solutionsolution

Platinum Metals Rev., 1998, 42, (4), 135-140 135 SOjNa s09" Fig. 2 Two water-soluble phosphines: (a) triphenylphosphine mono-sulfonate and (b) triphenylphosphine

~ p~ tri-sulfonate.The latter phosphine has a solubility of 1.1 kg I-' and thus has been used extensively / /

SOjNa

The selection of water is straightforward and polar groups onto the phosphine substituent. offers many benefits. First, wide ranges of In this respect, one of the most widely used organic solvents are immiscible with water; water groups is a sulfate (SO,') group which can be is cheap, easily purified, and readily obtained attached to the phenyl rings in PPh,. These and disposed of. However, despite the many represent, at the current time, the most widely advantages offered by aqueouslorganic bipha- commercially exploited ligand system. sic systems, the level of commercial exploita- The first of these sulfonated phosphines, triph- tion is still relatively low. This is probably due, enylphosphine mono-sulfonate (TPPMS, see at least in part, to a lack of suitable water-sol- Figure 2(a)) was reported as early as 1958 and uble catalysts. However, having said this, inter- was produced by the oleum sulfonation of triph- est in fundamental research has escalated rapidly enylphosphine (9). Modification of this syn- in recent years. There have been a number of thesis led to the production of the tri-sulfonated reviews published (2-6), for instance, an entire ligand (TPPTS, see Figure 2(b)) which is now volume of the Journal of Molecular Catalysis, with the most common ligand in use (10, 11). The an excellent editorial dedicated to the subject tri-sulfonated ligand has an extremely high water (7), and a .recent book, reviewed here on page solubility of ca. 1.1 kg 1.' (2). Formation of the 145, which examines aqueous phase catalysts catalyst complex is then carried out by co-ordi- from an industrial perspective (8). nation of the sulfonated phosphine ligand. Although direct sulfonation of pre-complexed Sulfonated Phosphines triphenylphosphine ligands should be possible, and Their Industrial Use the extremely acidic conditions needed to effect The main consideration when attempting to the change make the process unreliable. design a water-soluble complex is how to ren- Concentrating for the moment on the tri-sul- der hydrophilic a typical hydrophobic organo- fonated ligands, a whole range of water-soluble metallic complex. In order to do this, an appro- catalysts based on monometallic and cluster priate ligand (or ligands) must be placed around compounds has been reported, and a review by the metal centre (or centres); alternatively, ionic Kalck and Monteil includes a comprehensive catalysts, such as Dipamp Rh(cod)+ and list of these compounds (3). (binap)Ru cations, could be used. One class Of particular interest here is the rhodium com- of ligands that are widely used in homogeneous plex which is used in the RuhrchemielRhBne- single phase catalysis are phosphines and diphos- Poulenc process for the biphasic hydroformy- phines and it is therefore not surprising that the lation of propene to n-butyraldehyde (12), a synthesis of water-soluble phosphine derivatives process which is used to produce about 330,000 is attractive and has been the focus of much lig- tons of n-butyraldehyde per year. This process and design. Inducing hydrophilicity into a phos- is highly selective and gives a linear aldehyde to phine may be achieved by the introduction of branched aldehyde (nliso) ratio of 9515 with

Platinum Metals Rev., 1998,42, (4) 136 99 per cent substrate conversion. Side reactions and loss of catalyst are both negligible. Since the use of this process commenced, catalyst development has continued and more active catalysts have been reported, although the selectivity has decreased ( 13, 14). RhBne-Poulenc have also expanded the use of co co their biphasic production facilities into the manufacture of alcohols by hydrogenation and hydrodimerisation (5). A similar process with a rhodium/TPPTS catalyst is also used for the production of valeraldehyde from butene (15), which is the basis of n-valeric acid, used in the manufacture of CFC-free refrigerants.

Although the majority of work has concen- 60 co trated on sulfonated phosphines there are other Fig. 3 The structures of (a) Rm(CO),,(TI'PTS) polar groups that can be used to induce water and (b) RU~(CO)~(TPPTS),; both catalyse the solubility. These include (in no particular order) hydrogenation of non-activated olefins hydroxyl, ether, carboxylate and amine groups. Ligands with these water solubilising groups will not be discussed in detail, due to the large num- two main types have been reported (17, 18). ber which exist, and in most cases the catalytic The first of these is based on TPPTS deriva- properties of complexes with these ligands have tives, two examples of which are shown in Figure not been investigated in detail. The reviews men- 3. In most cases the synthesis of this type of clus- tioned previously present a more comprehen- ter is simple and is achieved by the replacement sive and fuller picture of these ligands (2-6). of one or more carbonyl ligands with the water- soluble phosphine ligand under reflux in a Metal Clusters as Water-Soluble suitable solvent. Cata 1 y st s The use of these compounds in the water- The use of metal clusters in conventional gas shift reaction (the reduction of water to homogeneous processes has been widely stud- hydrogen) has also been examined (19). This ied because they are considered to have prop- is a particularly valuable reaction, as it would erties intermediate between homogeneous and potentially allow water to be the source of hydro- heterogeneous catalysts. As a cluster consists of gen for biphasic hydrogenations. AU of the clus- several metal atoms, activation of an organic ters tested were found to catalyse the water-gas substrate may take place at more than one metal shift reaction, although no quantitative mea- atom and this can have a profound effect on the surements were performed, and some changes activity. The number of catalytic processes in in the catalysts were found to have taken place which clusters are effective is extensive, although during the course of the reaction. examples where they are used in commercial We have since directed our attention to the use processes are rare (16). Also, there is often uncer- of this range of catalysts in both hydroformy- tainty as to whether the cluster is broken down lation and hydrogenation reactions. Early results into mononuclear fragments during catalytic for hydrogenations of olefins have proved pos- processes or whether the metal core remains itive although catalytic turnovers are quite low. intact. A similar change in the catalyst also occurs dur- A new aspect of biphasic catalysis has been the ing hydrogenation and this is now thought to synthesis of water-soluble clusters. There are be independent of the catalytic reaction. only a few water-soluble clusters at present and However, the change in species does not seem

Platinum Metals Rev., 1998, 42, (4) 137

of conversion. Also, catalysts which are sensi- *+ tive to moisture (as many are) cannot be used 1 in water. The ideal situation would be an alter- a native solvent, capable of dissolving a wide range I of metal compounds without reacting with the metal centre and so deactivating the catalyst. Even without modification, ionic liquids may represent an alternative solvent. Ionic liquids are fundamentally molten salts. Molten sodium chloride (m.p. SOSOC) is an example of a single component ionic liquid. It is clear to see - from its high melting point - that sodium chloride would not be suitable as a solvent for biphasic catalysis. However, a range of dual-component ionic liquids is available Fig. 4 The structure of [HBu,(q-C,H,),]a'; this cluster catalyses the hydrogenation of which are molten at and near room tempera- benzene and other arenes in water and ionic ture (2 1). The physical properties of these liq- liquid biphasic reactions uids are quite interesting but the main properties of interest here are: their immiscibility with a wide range of to affect catalytic activity. A detailed analysis of organic solvents (making them ideal for bipha- our findings will be published in due course. sic systems); An alternative series of water-soluble clus- their polar nature (making them good ters has also been reported (17). These are not solvents); and based on phosphine ligands but on cationic the low nucleophilicity of their component tetraruthenium clusters with arene and hydride ions (preventing deactivation of the catalyst). ligands. Several have been synthesised and char- The ionic liquids we are interested in using acterised and one of the clusters, see Figure 4, are formed from two chemical components: an has been-successfully used to hydrogenate ben- organic component (either 1-ethyl-3-methyl- zene and some simple arenes -which is encour- imidazolium chloride, see Figure 5(a), or aging from an industrial perspective (20). The clusters are reported to be quite active, especially for the hydrogenation of benzene to cyclohexane, but not unexpectedly the conversion of the arene derivatives showed slightly lower activity and was not particularly selective. Indeed, where the substrate molecules possessed unsaturated side- groups, these were preferentially hydrogenated. L J

Ionic Liquids - the Future of Biphasic Catalysis? 'a- While water has proved to be the most widely used solvent for biphasic reactions there are several problems associated with it. For example, the chemical modifications to the catalyst which are needed to induce water solubility often Fig. 5(a) 1-ethyl-3-methyl-imidazolium reduce the catalytic activity, and certain active chloride and (b) 1-butyl-3-methyl-imidazolium chloride homogeneous catalysts are unsuited to any type

Platinum Metals Rev., 1998, 42, (4) 138 1-butyl-3-methyl-imidazolium chloride, see disadvantage is that uncharged species have Figure 5(b)) and an inorganic salt (aluminium decreased solubility in this ionic liquid whereas chloride or sodium tetrafluoroborate). a wide range of neutral compounds can dissolve A number of studies in biphasic catalysis have in the chloroaluminate melts. The tetrafluoro- already been performed using an ionic liquid as borate melts are still, however, very strongly the catalyst solvent (22-26). Ionic liquid sys- polar in character and as such will dissolve tems have been used for hydrogenations (with charged species easily. We are currently design- rhodium, ruthenium and cobalt complexes), ing new catalysts based on these requirements. hydroformylations (with rhodium complexes), Heck coupling (with palladium complexes) and Conclusions oligomerisations (with nickel complexes). Biphasic catalysis is an under-exploited tech- So far our interest has concentrated on the use nique, but with increasingly demanding envi- of metal clusters in the ionic liquid. We have ronmental legislation the opportunity for this carried out a preliminary investigation into the technique to become more widespread in indus- effect of the chloroaluminate acid melt (a 2: 1 try is quite clear. In addition to those discussed molar ratio of AlCl, and 1-butyl-3-methyl- above, other biphasic regimes are also available, imidazolium chloride) on a range of metal car- for example, a group of perfluorinated ethers bonyls. The strongly Lewis acidic environment which are chemically inert, non-toxic and gen- presented by the ionic liquid causes a change in erally immiscible with other organic solvents, the metal carbonyls over a period of time, but has been reported (27-29). As with aqueous we have been unable to draw any conclusions biphasic catalysis, the catalytic species have to at the present time. be modified to achieve solubility, but in this case, Since our preliminary work into the effect of such modifications are based on the replace- the acidic melt and with the experience of sev- ment of traditional ligands with partially fluo- eral low-pressure hydrogenation attempts (in rinated or perfluorinated ligands. However, the which the melt has initiated rapid oligomeri- high cost of both the fluorous solvent phase and sation of the olefins used) we have shifted our the catalyst systems required has, at the present attention to ionic liquids based on the tetra- time, made this type of biphasic system less fluoroborate ion. These ionic liquids, unlike attractive to industry even though they are envi- those based on chloroaluminates, are air sta- ronmentally friendly compared to the systems ble and are thus much easier to handle. They currently available. also do not cause oligomerisation of the olefin The use of biphasic catalysis is gradually substrates. The main disadvantage concerned becoming increasingly acceptable and it can be with the tetrafluoroborate range of ionic liquids expected that the number of processes involv- is that they exhibit considerably greater vis- ing it will continue to grow as the benefits that cosity than the chloroaluminatevariety and thus it offers are shown to be both environmentally very aggressive agitation is required. Another sound and cost effective.

References 1 W.W. Keim,Keim, Chem.Chem. Ing.Ing. Tech.,Tech., 1984,56,8501984,56,850 8 B. Cornils and W. A. Herrman, “Applied 2 E.E. G.G. Kuntz, Kuntz, Chemtech,Chemtech, 1987,17,5701987, 17, 570 Homogeneous Catalysis by Organometallic 3 P.P. Kalck Kalck andand F.F. Monteil,Monteil, Adv.Adv. Organomet.Organomet. Chem.,Chem., Catalysts”, Wiley-VCH, Weinheim, 1998 1992,34,2191992,34,219 9 S. Ahrland, J. Chatt, N. R. Davies and A. A. 4 W.W. A.A. HerrmannHerrmann andand C.C. W.W. Kohlpainter,Kohlpainter, Angew.Angew. Williams,J. Chem. SOL.,1958, 276 Chem.,Chem., Int.Int. Ed.Ed. Engl.,Engl., 1993,32,1993,32, 15241524 10 E. G.Kuntz, French Patent 2,314,910; 1975 5 B. Cornils, W. A. Herrman and R. Eckl, J. Mol. B. Cornils, W. A. Herrman and R. Eckl, J. Mol. J. Sabot, European Patent CutuZ.Catal. A:A: Chem.,Chem., 1997,1997, 116,116, 2727 11 L. 61104,967; 1982 66 F.F.JOC, JOC, andand A. A. Katho,JKatho,J MoZ.Mol. Cud.Cad.A: A: Chem., Chem., 1997,1997, 12 C. Larpent, R. Dabard and H. Patin, lnorg. Chem., 116,3116,3 1987,22,2922 77 I.I. T.T. Horvath,J.Horvath,J. MoZ.MoZ. Cutul.Catal. A:A: Chem.,Chem., 1997,116,1997,116, 13 Y.Amrani, L.Lecomte, D. Sinou, J. Bakos, I. Toth EditorialEditorial and B. Heil, Organometallics, 1989, 8, 542

Platinum Metals Rev., 1998, 42, (4) 139 14 A. Avey, D. M. Schut, T. J. R. Weakley and D. 22 Y. Chauvin, L. Mussmann and H. Olivier, Angew. R. Tyler, Inorg. Chem., 1993, 32, 233 Chem., Int. Ed. Engl., 1995, 34, 2698 15 H. Bahrmann, C. D. Frohning, P. Heymanns, H. 23 P. Suarez, J. E. L. Dullius, S. Einloft, R. F. Kalbfell, P. Lappe and D. Peters, 3. Mol. Catal. DeSouza and J. Dupont, Polyhedron, 1996, 15, A: Chem., 1997, 116,35 1216 16 L. N. Lewis, Chem. Rev., 1993,93,2693 24 A. L. Montiero, F. K. Zinn, R. F. DeSouza and 17 L. Plasseraud and G. Suss-Fink, J. Organomet. J. Dupont, Tetrahedron Asymm., 1997, 8, 177 Chem., 1997, 163, 539 25 J. E. L. Dullius, P. A. Z. Suarez, S. Einloft, R. F. 18 B. Fontal, J. Orlewski, C. C. Santini and J. M. DeSouza, J. Dupont, J. Fischer and A. DeCian, Basset, Inorg. Chem., 1986, 25, 4320 Organometallics, 1998, 17, 8 15 19 D. F. Bryce, P. J. Dyson, B. K. Nicolson and 26 Y. Chauvin, Actual. Chim., 1996, 44 D. Parker, Polyhedron, in press 27 I. T. Horvath and J. Rabai, Science, 1994,266,72 20 G.Meister, G. Rheinwald, H. Stoeckli-Evans and G. Siiss-Fink,J. Chem. SOC.,Ddwn Trans., 1994,3215 28 J. R. Gladysz, Science, 1994, 266, 55 21 C. L. Hussey, Adv. Molten Salt Chem., 1983, 5, 29 B. Cornils, Angew. Chem., Int. Ed. Engl., 1997, 185 36,2057 Progress in Dye-Sensitised Photovoltaics The 12th International Conference on the diffusive processes, although under some Conversion of Solar Energy into Photovoltaic conditions this is likely to be field-assisted. Power and Storage, IPS-12, was held in Berlin The extraordinarily slow time-constants from 9th to 14th August. This is the principal (typically hundreds of ms) of the cell in response technical conference on photovoltaics and solar to chopped illumination is almost certainly due energy storage worldwide, and is held every two to extensive trapping of electrons in surface states years. This year there were over 400 delegates, on the TiO,. with most coming from academic institutions. I Increased cation (for example Li') penetra- The major surprise of the conference was the tion into the pores of the TiO, probably improves growth in activity in dye-sensitised photovoltaics the efficiency of the electron transfer process (DSPVs), with over half of the presentations and certainly assists the ionic (iodide) current and posters being related to this topic. in the liquid phase. The net benefit is an increase The basic science behind dye-sensitised in cell current, although the type of cation also photovoltaic cells is well known (1). Cells are affects the cell open-circuit potential in ways typically constructed from a glass/ITO electrode that are not yet clearly understood. coated with a thin layer of dyed titania (TiO,). 0 The electron-hole recombination may be The TiO, is dyed with ruthenium-based com- retarded by virtue of the fact that the iodide pounds, such as Ruo(2,2'-bipyridyl-4,4'-dicar- 'hole-carrier' is negatively charged. boxylate),(NCS),, and then impregnated with I The electron-injection kinetics (not the a liquid electrolyte containing the I-/I; couple efficiency) are relatively insensitive to the dye as a regenerative redox shuttle between the dye type and very sensitive to the surface condi- and the counter electrode (platinum-coated tion of the TiO,. glass/ITO). The cell power-conversion efficiency Perhaps the highlight of the conference was can be remarkably high, with figures of > 10 per a 'live' demonstration of DSPV technology by cent under AM1.5 conditions being quoted, Dr K. P. Hanke, Institut fiir Angewandte Photo- due to the broad absorption spectrum of the voltaik, Gelsenkirchen, Germany, who used a dye (extending into the infrared region for some prototype module to turn an electric fan, during dyes (2)) and the absence of significant charge his lecture on issues involved in cell scale-up. recombination in the (n-type) semiconducting In summary, the work presented at this TiO,. conference has shown that dye-sensitised pho- While the complex photophysics and chem- tovoltaic cells are continuing to show promise istry of this system are still challenging, some as practical devices, and may, in the longer term, consensus emerged as to what makes these cells open up a new market for ruthenium and work as well as they do: platinum-based materials. The more advanced ruthenium-based dyes References show evidence for provided 1 M, GrHael, platinumMetals Rev., 1994, 38, (4), that proper sealing of the cell is achieved to 1 ct -- - IJI prevent ingress of oxygen and water (which 2 Md. K. Nazeeruddin, R. Humphry-Baker, M. initiate free-radical attack of the dye). Gratzel and B. A. Murrer, Chem. Commun., 1998, Electrons move primarily through TiO, by 7 19 R. J. POlTER

Platinum Metals Rev., 1998, 42, (4) 140 Formation and Decomposition of Palladium Hvdride Particles J IMAGING PICTURES ON THE NANOMETRE SCALE By €? D. Cobden and B. E. Nieuwenhuys Leiden Institute of Chemistry, Leiden University, The Netherlands and Y V. Gorodetskii and Y N. Parmon Boreskov Institute of Catalysis, Novosibirsk, Russia

Nanoscale changes in surface structure that accompany the low temperature exposure of palladium to hydrogen are reported. Field Emission Microscopy, a method for rapid in situ imaging of surfaceprocesses, has been used to exam- inepalladium tips of radius - 200 nm, produced by a novel technique. Images are presented of the initial stages of the uptake of hydrogen. Subsurface hydrides were initiallyformed when palladium tips were exposed to hydrogen gas at low temperatures, starting at highly open surfaces present on the tip. Extruding PdH particles were also formed on top of the palladium tip and their growth was observed to proceed in a ‘staccato’-like manner. Palladium crystallites remained on the surface after most of the hydrogen had been removed from the palladium sample by heating in vacuum. On heating the crystallites remained quite stable up to a temperature of - 700 K, but then melted back into the tip.

A detailed understanding of the process of - 10 to 20 pm in size, have been seen hydrogen absorption by metallic phases (met- developing during the early stages of hydrogen als, alloys and intermetallic compounds) is loading of a Pd( 11 1) single crystal (4). In addi- important for the development of new materi- tion, networks in parallel lines have been als for hydrogen storage. The interaction of observed on large single crystals by Sugeno and hydrogen with palladium in particular has been Kawabe (5). These patterns became apparent extensively studied (1,2), since the first report on complete transformation to the P-phase and of the absorption of hydrogen into palladium in could sometimes be seen after desorption of 1866 and since the first measurements of the hydrogen (5). palladium-hydrogen pressure-constitution-tem- Field Emission Microscopy (FEM) (resolu- perature relationship in 1895 (3). Two non-sto- tion - 2 nm) images of surface processes were ichiometric hydride phases can co-exist below observed in situ during exposure of stable clean the critical temperature (- 3OO0C),and on going palladium tips to hydrogen, see Figure 1. The from the a- to the P-phase there are large tips, produced by a novel technique (6), were increases in volume, with the lattice constant held in hydrogen at a pressure of 2.6 x 10” mbar increasing by - 3.3 per cent, which is a volume and 147 K. Figure l(a) is characteristic of a increase of - 11 per cent. These changes occur clean palladium tip with the (1 10) plane in its continuously over the phase transition. centre. In general, a FEM pattern represents a It is surprising that comparatively few stud- work function map of the various crystal faces ies have been focused on the structural changes on the end of a hemispherically shaped single occurring at the metal surface under the strain crystal tip. Figure 1(b) shows the growth of high of the expanding lattice. Triangular shapes, of intensity patches (that is, patches of increased

Platinum Metals Rev., 1998, 42, (4), 141-144 141 Fig. 1 (a) A clean palladium tip, produced by a new technique for making atomic tips for Field Emission Microscopy, showing the disposition of the principal faces. (b) After dosing with hydrogen at a rate of 1040 x lo" mbar s, at 147 K, showing the initial build-up of high emission centres on the more open surfaces. (c) After dosing with hydrogen at 26 x lo3 mbar s, and 147 K, showing the situation at saturation

case at saturation is represented, where these high intensity patches stop growing. Surfaces defects have been found to be very important for the low temperature uptake of hydrogen below 147 K (7,s). At 147 K, no build-up of such high electron emission centres has been observed at pressures below the one primarily studied here. We have examined in detail the 'staccato'-like growth of these novel structures. There appears to be overall continuous slow growth of particles, separated by periods of acceleration. The shape of most of the particles was rectangular or triangular, with the latter having previously been seen on a larger scale on the Pd( 1 1 1) surface (4). After evacuation of hydrogen from the gas phase, such structures formed on the surface at 147 K still remained intact. The effects of heating the hydrided tip are shown in Figure 2. The majority of the hydrogen desorbs from the tip at -190 K, but many of the structures formed have remained on the surface (6). There are only slight changes in the palladium tip between 300 K (Figure 2(a)) and 600 K (Figure 2(b)), with Figure 2(b) showing the situation after several minutes at 600 K. For the low-temperature H,-loaded palladium wire and for a Pd( 1 10) surface, no high temperature 0- desorption peak has been observed, suggesting that there was no hydrogen penemtion into the bulk (9-1 1). However, the P-desorption peak does appear when hydrogen is loaded at a temperature of 300 K. With the palladium wire, heated at a rate of 5 K s-', the P-peak appears at 620 K (1 1). Even if hydrogen had still been present in the palladium tip, it would have diffused out of the sample work function) first occurring around after several minutes at 600 K (7-1 1). It therefore (55 1) surfaces, which are basically (1 10) seems possible to conclude that the patches left on the terraces separated by (1 11) steps. Similar surface at this point are palladium microcrystals, still structures were found to grow on a very on top of the palladium tip. At 700 K however (Figure open (320) face, and were also observed 2(c)) these crystallites have all but disappeared, the on the (553) surfaces. In Figure 1(c) the obvious interpretation being that the palladium atoms

Platinum Metals Rev., 1998, 42, (4) 142 FigT 2 FEM image of a palladium tip in vacuum after low temperaturetemperature hydrogen hydrogen loading: loading: (a)(a) AtAt 300300 K, K, wherewhere the the bulk bulk of of hydrogen hydrogen has has been been removed, removed, butbut thethe structuresstructures formed formed on on the the surface surface remain. remain. (b)(b) AtAt 600600 K,K, wherewhere anyany remainingremaining hydrogenhydrogen willwill havehave desorbed,desorbed, andand onlyonly palladiumpalladium microcrystallites microcrystallites remain remain onon toptop of of thethe palladiumpalladium tip. tip. (c)(c) AtAt 700700 K, K, atat which which point point pal1,adium pal1,adium atoms atoms have have home beeome mobile,mobile, soso that that the the palladium palladium microerystallitea microerystallitea dissolvedissolve back back intointo thethe tiptip

are now becoming mobile and that the palladium microcrystals are melting back into the tip. One of the questions that remains to be answered is whether the structures formed on the palladium surface under the hydrogen dosing at low temperature (that is, 147 K), also contain hydrogen, or whether they are pure palladium crystals formed on top of a surface hydride. It is clear that the palladium atoms are mobile on the surface at low temperatures under the influence of an expanding PdH lattice, although possibly only in the topmost layers of the tip. The staccato growth of the treated particles gives an indication that the structures are actually PdH crystallites at low temperature. The slow growth can be equated to PdH lattice expansions in a- to p-phase transitions and the accelerated growth periods c'an be equated to stress causing palladium atoms to radically change positions. Indeed, the fact that the tip could take on a new orientation after high temperatuFe annealing of a sample exposed to H, at low temperatures, also seems to indicate the influence of stress.

Conclusions The use of FEM has provided a high resolution view of the kinetics of the initial stages of PdH formation at palladium surfaces exposed to H2at low temperatures. At patches of increased emission, initiated on the more open surfaces of the palladium tip, growth is mainly slow - since the palladium lattice must expand in taking up the hydrogen atoms, but there are rapid increases in the growth rate as the strains in the p- phase cause atoms to be expelled or rearranged. At satura~onthe particles have grown not only two dimen- that hydrogen has the ability to cause sionally, but also in height, such that when hydrogen movement of the palladium atoms at such is removed, microcrystals of palladium remain on top low temperatures is significant. Indeed, of the palladium tip. These palladium microcrystals many recent studies have shown that such are stable until temperatures are reached at which the metal surfaces can be quite mobile and palladium atoms become thermally activated. The fact the present study has demonstrated that

Platinum Metals Rev., 1998, 42, (4) 143 large reconstructions can occur when palladium prevent material degradation, when metal- interacts with hydrogen at 150 K. However, in hydrogen reservoirs are being designed. the bulk of a metal in which a hydride is being formed, there are few places for the atoms to go Acknowledgement when the lattice expands. As a consequence it The authors acknowledge financial Support from the Netherlands Organisation for Scientific Research appear that more thought needs to [WO)in the frameworkofthe ‘Russia Propramme’- be given to stabilising the surface in order to and of the Priority Programme “on-Linear Systems’.

References 1 F. A. Lewis, “The Palladium Hydrogen System”, 8 H. Okuyama, W. Siga, N. Takagi, M. Nishijma Academic Press, 1967, LondonNew York and T. Aruga, Sud Sci., 1998,401,344 2 F. A. Lewis, Inz. J. Hydrogen Energy, 1981,6, 319 9 R. J. Behm, v. Penka, M.-G. Cattaniaj K. Christmann and G. Ertl, J. Chem. Phys., 1983, 3 C. Hoitsema, Z. Phys. Chem., 1895, 17, 1 78.7486 4 T. J. Tiedema, B. C. de Jong and W. G. Burgers, 10 M.-G. Cattania. V. Penka. R. 1. Behm. K. Proc. Kon. Ned. Akad. Wet., 1960, 63B, 422 Christmann and*G.Ertl, Suh ScI., 1983,126, 5 T. Sugeno and H. Kawabe, Mem. Inst. Scient. Ind. 382 Res. Osaka Univ., 1957, 14, 25 11 0. M. Ilinitch, F. P. Cuperus, V. V. Gorodetskii, M. Yu. Smirnov, 0. P. Burmatova and I. 0. 6 P. D. Cobden, V. V. Gorodetskii and B. E. Ilinitch, Proc. 4th Workshop “Optimisation of Nieuwenhuys, to be published Catalytic Membrane Reactor Systems, European 7 R. Dus, E. Nowicka and Z. Wolfram, Surf Sci., Science Foundation, 1997, SINTEFF Materials 1989,216, 1 Technology, Oslo, p. 89 Carbon Monoxide Sensing Technology Growing awareness of the hazard of carbon is produced diffuses out from the sensor. monoxide (CO) in the home environment has The electrode reactions take place under acidic aroused great interest in detector alarms in the conditions to avoid a build up of CO, in the sen- U.K. and North America. Various sensing tech- sor. Under these conditions platinum is required nologies have been used to detect the gas. to catalyse the electrode reactions. Platinum has The first commercial sensor, the Taguchi sen- the ability to form a range of chemisorbed sur- sor, correlated the change in conductivity of a face species, thereby lowering the activation energy heated tin oxide pellet to the concentration of CO of intermolecular reactions. Platinum forms car- present. However, due to its high power require- bony1 species and surface bound hydroxyl species ments, this sensor required mains wiring. The required for the overall anode reaction. first battery powered CO detectors used an opti- In practice porous electrodes made from a high cal detection technique based on colour chem- surface area platinum material are used. This istry, the colour change being the same as in the provides a three-phase boundary between the formation of carboxyhaemoglobin in the blood. gas, the electrolyte and the electrode where Recently, electrochemical units, suitable for the electrode reactions can occur rapidly in the use in battery powered alarms, have become presence of CO. GAVIN TROUGHTON commercially available. These have significant advantages over prior technologies in their accu- racy and reliability over a wide range of gas con- Platinum Labware Catalog centrations. Some instruments have visual dis- Alfa Aesar in North America has just pub- plays to differentiate between acute high CO lished a “Platinum Labware Catalog” which concentrations and hazardous chronic low con- describes a range of laboratory products incor- centrations. Carbon monoxide and oxygen dif- porating platinum, platinum group metals and fuse into the sensor &om the ambient air to react: Zirconia Grain Stabilised (ZGS) platinum, util- ising the inertness and malleability of platinum. Anode: CO + H,O 4 CO, + 2H’ + 2e The catalogue describes typical uses of the Cathode: %O, + 2H+ 2e~+ HZO equipment and contains reference data and Overall: CO + %02+ C02 information on a recycling programme. The current flowing between the anode To obtain a copy of the catalog contact Alfa and cathode through an external circuit is pro- Aesar; in North America, tel: 800-343-0660 portional to the CO present over a wide con- ext. 6404, fax: 800-322-4757; Rest of the World, centration range. The carbon dioxide (COJ that tel: 978-521-6404, fax: 978-521-6350.

Platinum Metals Rev., 1998, 42, (4) 144 Aqueous-Organic Biphasic Catalysis Aqueous-Phase Organometallic Catalysis: Concepts and Applications EDITED BY BOY C0RNIL.S AND WOLFGANG A. HERRMA”, Wiley-VCH, Weinheim, 1998,615 pages, ISBN 3-527-29478-3, E140.00

This is the first book devoted entirely to the and olefin metathesis are all reviewed and the subject of aqueous-organic biphasic catalysis r81e of the platinum metals in these reactions is and is both timely and important for this envi- described. In keeping with the underlying theme ronmentally clean technology. Biphasic catal- of clean catalysis, the hydrogenation and ysis involves two immiscible liquid phases, one hydrogenolysis of organosulfur compounds, and containing the catalyst and the other the sub- dehalogenationsusing hydrophilic catalysts, are strate, so that the separation of the catalysts is also covered. These sections are written by drastically simplified. Many eminent scientists notable experts including M. Beller, J. G. E. contribute chapters, including F. Joo and E. G. Krauter, W. A. Herrmann, C.-P. Reisinger, D. Kuntz whose papers are seminal. The editors Sinou, N. Yoshimura, S. Haber, W. C. are well-known experts, one from academia and Schattenmann, R. H. Grubbs, D. M. Lynn, C. one from industry, and this is reflected in the Bianchini, A. Meli, M. Bressan and A. Morvillo. range of contributions. The book covers other The penultimate chapter on other biphasic catalysts besides those of the platinum group concepts includes non-aqueous biphasic regimes. metals, but since it describes many industri- The section on fluorous-organic systems by I. ally important catalytic processes, ruthenium, T. Horvath covers rhodium and iridium cata- rhodium and palladium frequently feature. lysts. Ionic liquid-organic systems are described The book contains eight main chapters made by H. Olivier who illustrates the use of ruthe- up from between one and twenty-five individ- nium, rhodium, palladium and platinum cata- ual contributions. Certain chapters, such as that lysts. P. C. J. Kamer and P. W. N. M. van on environmental and safety aspects of bipha- Leeuwen describe an amphiphilic approach and sic catalysis, are essential reading for a rounded M. Beller and J. G. E. Krauter conclude with picture of the subject. a section on water-soluble, polymer-bound cat- The platinum metals feature most prominently alysts. These methodologies are emerging as in the chapter entitled “Typical Reactions” which important - but related - alternatives to the is more than 250 pages in length, with contri- aqueous-organic protocol. butions from many authors. Hydroformylation The book is full of factual data presented in is discussed first, with B. Cornils and E. G. Kuntz tables and graphs and as such is an invaluable providing a resume of the development of a com- source of information when coupled with the mercial biphasic 0x0 plant employing a water- extensive bibliographies at the end of each sec- soluble rhodium catalyst. Hydroformylation of tion. There are also a large number of figures lower and higher oletins, as well as functionalised and schemes which help to clarify the text. olefins, is described, and not surprisingly, The editors have succeeded in producing a rhodium catalysts feature prominently. F. Joo book of interest to everyone working with plat- and A. Katho write a section on hydrogenation inum metals in homogeneous catalysis and com- which is dominated by rhodium and ruthenium pliments their earlier volume entitled “Applied catalysts. After this comes a series of shorter sec- Homogeneous Catalysis with Organometallic tions beginning with carbonylation and carbon- Compounds”. It sets out ways in which carbon coupling reactions, the emphasis being organometallic catalysts can be made hydrophilic firmly on palladium-based catalysts. Allylic sub- and shows their wide range of uses in biphasic stitution, hydrodimerisation, asymmetric syn- catalysis for small-scale synthesis and industrial- thesis, fine chemical syntheses, polymerisation scale work. PAUL J. DYSON

Platinum Metals Rev., 1998, 42, (4), 145 145 The Build-Up of Bimetallic Transition Metal Clusters By Paul R. Raithby Department of Chemistry, University of‘ Cambridge, England

The synthesis and reaction chemistry of high nuclearity transition metal carbonyl clusters is briejly reviewed, and new synthetic strategies leading to the “rational” synthesis of bimetallic clusters containing metal cores of over 1 nm in dimension are described. The solid state structures of a number of usmiuml mercury, osmiumlgold and rutheniumlcopper bimetallic clusters are discussed with regard to the nature of their formation, und of their bonding and redox properties. Suggestions are made as to how the synthetic strategies can be adapted to prepare bimetallic clusters of industrially useful combinations of metals. Recent work showing that bimetallic nunuparticles prepared frum clusters are catalytically active when anchored inside mesoporous silica is also discussed.

Transition metal carbonyl cluster chemistry lic properties as the nuclearity increases, has been an important and developing topic although different sizes of cluster exhibit dif- of research in organometallic chemistry for the ferent types of metal-like properties under last three decades (1). One of the main appeals different conditions (2). of clusters is that they lie at the interface between One of the main thrusts of cluster chemistry ‘‘conventional” organometallic chemistry and at Cambridge has been to prepare ever larger the chemistry of colloids and of the bulk metal. transition metal clusters and to investigate their Figure 1 illustrates the progression in particle physical and chemical properties. A range of size from a single atom through clusters, with clusters containing more than ten metal atoms metal core sizes of around 1 nm; nanoparticles, has now been prepared and crystallographically with sizes up to 100 nm; leading into the col- characterised (3) and examples in which the loid regime; and then on to the bulk metal. metal atoms “condense” to form structures cor- Indeed, at what size (number of metal atoms) responding to the hexagonal, cubic and body- does a metal cluster stop behaving like an centred cubic packings found in bulk metal have organometallic complex, with bonding proper- been observed, as well as other clusters, such as ties that can be described in terms of discrete [Pt19(C0)22]4-(4), which exhibit five-fold sym- molecular orbitals, and take on metallic prop- metry packing. erties, where the bonding can be described in The diameters of the metal cores in the largest terms of band structure? There is no immedi- of these clusters, such as [Ni,,Pt,(CO)4aH,,]”~ ate answer to this question, but there is a clear (n = 5, 4) are of the order of 2 nm (5). Even progression towards the clusters taking on metal- larger clusters containing copper and selenium

*. .. - ;.;:. .. - .*. 4

Single Cluster Nanoparticle Colloid Bulk metal metal Fig. 1 The progression in particle atom size from a single metal atom to Particle diameter roi -lo2i 403i )lo% the bulk metal

Platinum Metals Rev., 1998, 42, (4), 146-157 146 have been prepared, and the largest of these to have been crystallographically characterised is [CU~~~S~~~(PP~~)~~]in which the selenium atoms exhibit “ABA” stacking and the copper atoms occupy interstitial sites (6). There are also reports of transition metal clusters, for instance those containing Auss(7) and Rhss(8), Pt,09(9) and Pd,,, (10) units, and a series of palladium clusters containing up to 2000 metal atoms (I I), which have not yet been crystallographically characterised, but which must have dimensions of the order of 4 nm. Several research groups have proposed that clusters can act as good building blocks in nanoscale architecture and thus will find application in the fabrication of single electron devices (12). Small metal particles and other transition metal clusters have also been clearly shown to Fig. 2 The metal core structure of form densely packed monolayers on electron [Os,(CO),]*- showing the four triangular microscope grids when they are ligated by faces of the Osmtetrahedron organic surfactant molecules (13). From the viewpoint of catalysis, metal clusters can be considered as fragments of a metal under catalytic conditions is rather more surface surrounded by a layer of “adsorbed” lig- challenging. However, for the majority of clus- and molecules. Even the largest osmium cluster models, for example [Os,,(CO),,]’- (14), only ter carbonyl so far characterised, [Os,,(CO),]’~, “surface” atoms are present, and since the where the metal framework is approximately sub-layers of the bulk metal influence the chem- 0.9 x 0.9 x 0.9 nm in size, contains only surface istry of the surface atoms on a catalytic surface, atoms, with each osmium atom being bonded some aspects of the model are not valid, so the to at least one carbonyl ligand, see Figure 2, “analogy” should be treated with caution. (14). Therefore, the simple answer to the question However, can clusters be regarded as good of whether clusters are good models for models of metal surfaces in heterogeneous cat- heterogeneous catalysts would be “no”. alytic reactions? The “cluster/surface” analogy was pointed out quite early in the development “Rational” Synthesis of High of cluster chemistry (1 5), and ever since then Nuclearity Mixed-Metal Clusters clusters have been used as models for catalytic With a view to preparing precursor materials systems (1 6). that could have applications in catalysis and Certainly, organic molecules bond to catalyt- nanoparticle technology, the “cl~~ter”group in ically active metal surfaces in the same way as Cambridge has been developing strategies for to metal clusters, and analysis of cluster systems synthesising high nuclearity mixed-metal clus- is easier because they can be subjected to the ters containing ten or more metal atoms in their full range of solution spectroscopic techniques, cluster cores. Even the smallest of these clus- such as IR and multinuclear NMR spectro- ters should have a core diameter in excess of 0.5 scopies, mass spectrometry and, in the solid nm and have the advantage, unlike bimetallic state, single crystal X-ray crystallography, particles prepared by other routes, that the exact whereas analysing the bonding modes of ratio of the two metallic elements is known. co-ordinated molecules on a metal surface As much of the early cluster synthesis work

Platinum Metals Rev., 1998, 42, (4) 147 Fig. 3 The formation of the “spiked”-triangular cluster [Os,H,(CO),,] from the reaction of the I activated cluster [OS~(CO)~~(M~CN)~]with [OsHZ(CO)d] involved pyrolysis or thermolysis techniques and cluster with a neutral monometal complex. resulted in a range of products, all in low yields, The second route involves the ionic coupling fiom a single reaction, it has been necessary to reaction between a carbonyl cluster anion and develop synthetic strategies where one target a monometal cationic species, again to increase cluster molecule can be obtained in good yield the cluster nuclearity by one. In Figure 4, the (17). tetranuclear osmium cluster [Os,H,(CO) ,,I is In order to achieve this, two fairly straight- initially reduced with WPh,CO to form the forward synthetic routes are available, given that dianion [Os,H,(CO) ,,I ‘-, and then treated the starting materials for the production of high immediately with the labile cation [M(q6- nuclearity clusters are usually low nuclearity C6H6)(MeCN),I2+(M = Ru, 0s) to form the carbonyl clusters. pentanuclear, neutral cluster [Os&W,(CO),,(q6- The first route, illustrated in Figure 3 by the C6H6)](1 9). By choosing appropriate cation formation of [OS~H~(CO)~~],involves the acti- and anion charges and ratios, the cluster nuclear- vation of the binary carbonyl [Os,(CO),,] with ity can be increased by two units, as in the Me,NO, in the presence of MeCN and results reaction of [Os,(CO),,]’~with two equivalents in the oxidation of carbonyl ligands to carbon of [Ru(q5-CsH5)(MeCN),]’to give the pen- dioxide and the occupation of the vacant co- tanuclear cluster [Os3Ru,(CO),,(q’-C,H,),] (20). ordination sites with labile MeCN ligands. The This latter ionic coupling route has been par- subsequent addition of the neutral mononuclear ticularly successful, and has been extensively complex [OSH,(CO)~]displaces the MeCN exploited to prepare a wide range of higher groups and affords the “spiked”-triangular clus- nuclearity clusters containing carbocyclic ter [OS,H~(CO),~](18). In this method the ligand groups (21). cluster nuclearity is increased by one, by the The method has also been used by a number reaction of a neutral, activated, low nuclearity of research teams for synthesising mixed-metal

Insertion M = Ru, 05 NCMe (Oc)2 ..!.a \ [H,Os,CCO),,]

(C0)3 H ,,OS,,M(CO)~I(C~H~)

Fig. 4 The synthesis of [OsdMH,(CO),,(~6-C6H6)](M = Ru, 0s) from the coupling of [OS~H~(CO)~~]~~with [M(t16-C6H6)(MeCN),]2+ (M = Ru, 0s)

Platinum Metals Rev., 1998,42, (4) 148 has a core diameter in the surface plane of approximately 1.2 nm (12 A). %P This coupling process, more correctly called redox condensation, resulting in cluster build- up, can also be achieved between the carbido- stabilised, decanuclear cluster anion [OsloC(CO)z4]z~and [Hg(O,SCF,),] to afford the anion [ { OsloC(CO)z4}zHg]2,Figure 6. Here the mercury atom links the two decanuclear clusters by bridging an edge of each Oslounit, forming a cluster containing 2 1 metal atoms (24). In this reaction, the appropriate choice of the mercury(I1) salt, [Hg(O,SCF,),], is the key b to the formation of the higher nuclearity mixed- Fig. 5 The structure of the “raft” cluster metal cluster. This is partly because the deca- [{Os,(CO)rlHg}s] showing the linking ofthree osmium dianion precursor has low nucleo- Os, triangles to the central Hg3 triangle philicity (the negative charge being delocalised over the ten metal centres) and because there is an increased propensity for the reaction to clusters containing the coinage metals by the follow alternative pathways involving partial reaction of carbonyl cluster anions with cationic degradation or rearrangement of the metal copper, silver and gold complexes (22).

Osmium-Mercury Clusters So far, our most extensive series of studies into the formation of mixed-metal clusters containing ten or more metal atoms have also involved the reaction of a range of ruthenium and osmium cluster carbonyl anions with late transition metal cations, such as [Ha]’ (X = C1, CF,), [AuPR,]’ (R = alkyl, aryl) and [CU(NCM~)~]’.The first indication that cluster build-up could occur to produce higher nuclearity clusters came from the metathesis reaction of [OS,H(CO)~~]~with mercury(I1) salts. The product of the reaction was the extremely photolabile, dodecanuclear ‘‘rafl” cluster [ { Os,(CO) IHg},] shown in Figure 5 (23). It is significant that the three mercury atoms form a central triangle with Hg-Hg distances in the range 3.08-3.12 A. The “OS,(CO)~~”fragments bridge this central triangle, with each “Os(CO),” group forming bonds to two mercury atoms (0s-Hg in the range 2.71-2.76 A); the co-ordinated “Os(CO),” b groups each form one bond to a mercury atom L (0s-Hg in the range 2.98-3.05 A). This clus- Fig. 6 The molecular structure of the mercury ter can be viewed as a model for a bimetallic linked cluster dianion [{Os,,C(CO),,},Hg]*~ surface, and while being only one layer thick

Platinum Metals Rev., 1998,42, (4) 149 The Hg-Hg bonds in the Hg, dianion are an average 2.927 A long, but in the HgZdianion 0 0 0 [Os,,Hg2C,(CO)42]2~,which has also been crys- 4 PLP4 tallographically characterised and found to have a pair of mercury atoms linking the two Os, units, the Hg-Hg bond is significantly shorter at 2.745 A long.

Osmium-Gold Clusters A wide range of reactions which form high nuclearity osmium-gold clusters has been carried out (27), but this discussion will be restricted to two key syntheses which yield important information about the build-up processes in high nuclearity clusters. The first reaction is that between [OS,~C(CO),,]~~and the polygold cation [(AuPR,),O]+(PR, = PCy,, PPh,, PMeJ’h) which affords the fourteen atom cluster [OsloC(CO) ,,Au(AuPR,) ,] (28). The structure of the PCy, derivative has been characterised crystallographically and is shown in Fig. 7 The structure of the dianion Figure 8. The tetracapped octahedral geome- [MisHgX~(Co)u]’- try of the parent Os,, dianion is retained, and the four gold atoms form a tetrahedral cluster which is linked to the osmium core via one gold framework. Again, the metal core in this cluster atom that bridges an 0s-0s edge of one of the is somewhat asymmetric but has a maximum dimension of approximately 1.6 nm.

When a similar reaction occurs between Q I) [M,,C(CO),,]’~(M = Os, Ru) and the mercury \8P salt [Hg(O,CCF,),], a different type of product, [M18Hg3CZ(CO)IZ]2~,is obtained (24, 25), although the metal core still contains 21 metal atoms. This also contains a central Hg, triangle, Figure 7, linking two “M9C(CO)ZI”units, derived from the framework of the tetracapped octahedral starting materials [MI&( CO)zr] 2- by the loss of an “Os(CO),” vertex. As in [{OS,(CO),~H~},I it is of interest that the mercury atoms have linked together between two osmiumhthenium cores forming, in metal- lurgical terms, a mercury domain. Another fascinating feature of the cluster dianion [OS,,H~,C~(CO)~~]~-is that it undergoes reversible photochemical and redox extrusion of mercury atoms to give a complete series of Fig. 8 The molecular structure of high nuclearity clusters with general formula [OS~~C(CO),~U(A~PC~~):~] [Os,sHg,Cz(CO),2]”~(n = 1-3, m = 1-4) (26).

Platinum Metals Rev., 1998, 42, (4) 150 Fig. 9 (left) The molecular structure of the osmium-gold complex [Osla(CO),,(AuPPhzMe),] Fig. 10 (right) The structure of the [OS,~(CO)~,(AUPP~~M~),]complex when it is viewed from one end of the cluster. The novel tubular nature of the metal cnre composed of osmium atoms is clearly visible

tetrahedral caps. The mean Au-Au distance to indicate a bonding interaction, while the truns within the Au, tetrahedron is only 2.7 1 A, which axial osmium atoms [Os(2)... Os(3a) and suggests that the Au-Au bonds are relatively Os(3)... Os(2a)l have moved closer together than strong. As also observed for the osmium-mer- would be expected in an octahedron, to an aver- cury clusters, the gold atoms have a tendency age distance of 3.3 A. The pairs of gold atoms to “cluster” together to form a domain, and are separated by 4.43 A, and the length of the do not become incorporated into the osmium tube including the gold phosphine groups atom framework. exceeds 1 nm. In order to support this type of In the second key reaction the non-carbido geometry the metal bonding must be delocalised decaosmium cluster dianion [0~10(c0)26]’~is in character. further reduced with KPh,CO, presumably to give a tetra-anion, that is treated in situ with Ruthenium-Copper Clusters [AuPPh,Me]+ to give a new type of high Of all the cations discussed above, nuclearity cluster [Oslo(CO),,(AuPPh2Me),],[Cu(NCMe),]’ is the most versatile for use in see Figure 9 (29). cluster build-up reactions. It has been used in At first sight, from the structure of this four- combination with a number of ruthenium clus- teen atom cluster, it appears that the four ter anions to produce a range of novel, high [AuPPh,Me]+cations merely cap the four end nuclearity, mixed copper-ruthenium clusters. faces of a bioctahedral osmium core, but the For example, in dichloromethane, the view looking from one end of the cluster to the reaction of the octahedral ruthenium anion other, Figure 10, shows that the octahedra are [RU~(~~-H)(CO),~]~with an excess of distorted and that a novel tubular structure has [Cu(NCMe),]’ affords the dianionic cluster formed. The 0s-0s equatorial edges [Os(4)- [{Ru,H(C0)12)2Cu7C1,]2~,see Figure 11 (30). Os(5a), Os(1)-Os(la), Os(5)-0s(4a)] have The fifteen-atom cluster core contains two expanded to lie in the range 3.29-3.32 A, a dis- Ru, tetrahedra linked through a Cu7unit which tance that is significantly longer than is judged may be described as two fused square-based

Platinum Metals Rev., 1998, 42, (4) 151 Fig. 11 The structure of the [{RulH(CO)lr}rCu,Cld]2~dianion showing the central Cu: unit

-vCIO)

pyramids sharing a common triangular face. tion of the original Ru, octahedron has not Three chloro ligands each symmetrically bridge occurred, and the two octahedra are linked pairs of copper atoms, while the remaining cop- through two Cu, tetrahedra which share a com- per atom, Cu(5), forms no bonds with ligands mon edge, generating two butterfly arrange- but has eight metal contacts. Thus, the imme- ments which bond to the ruthenium units. diate environment around Cu(5) is similar to Overall, the eighteen-atom cluster can be viewed that in metallic copper and, overall, again it is as a linear condensation of four octahedra. Two seen that the element with the formal d'O elec- edges of the Cu, unit are symmetrically bridged tron configuration has formed the central by chloride ions. domain, and the transition metal units are fused For both reactions, the presence of chloride to its periphery. ions is apparently necessary, even if, in the first The product of this reaction is very sensitive case, they are abstracted from the solvent. to the nature of the solvent used. In the However, by simply altering the solvent, from presence of [(Ph,P),N]Cl in MeCN, when dichloromethane to [(Ph,P),N] C1 in MeCN, [Ru,H(CO),J is treated with a large excess good yields of high nuclearity clusters with ruthe- of [Cu(NCMe),]+, a different product, nium:copper ratios of 8:7 (approximately 1: 1) [{RU,H(CO),,),CU~C~,]~,is obtained in good and 2:1, respectively, are obtained from a room yield, see Figure 12 (30). In this case degrada- temperature reaction.

Fig. 12 The structure of the O(21I [ {Ru,H(CO)17}2C~CI,]2~dianion

Platinum Metals Rev., 1998, 42, (4) 152 Fig. 13 The core geometry in the [ {R~~OHZ(CO)~~}~CU,CI~]~- dianion

This synthetic methodology can be expanded nuclearity cluster, was obtained in quantitative further. The reaction of the decanuclear dian- yield, see Figure 14 (32). The two Ru, octahe- ion [RU,,H,(CO)~~]~~with excess [CU(NCM~)~]+,dra are linked by a rectangular planar arrange- in dichloromethane, in the presence of chloride ment of four copper atoms, opposite edges of ions, affords the twenty-six-atom cluster which are bridged by chloride ions. Thus, with [ {RuloH,(CO),,}2C~~ClZ]~~with a 70 per cent chloride ions present in the starting material the yield and a ruthenium:copper ratio of 10:3 (31). cluster build-up is not so efficient, resulting in Here, the two Rule units are fused on either side a sixteen-atom cluster with a ruthenium:copper of a Cu, unit which adopts the same geometry ratio of 3: 1, but the yields of the product are as that found in [ { Ru,H(CO) !,} ,CU,CI,]~- improved. (Figure 12). The overall core geometry can be In all of the copper-ruthenium clusters inves- described as six fused octahedra with an addi- tigated, the copper atoms condense to form a tional ruthenium atom at each end capping a central domain and the ruthenium cluster units butterfly face to form a trigonal bipyramid, condense around the periphery to produce nano- Figure 13; this metal framework is over 1.6 sized particles based on the fusion of octahedral nm long. or tetrahedral units, just as is observed in other In order to investigate the role of the high nuclearity clusters and in close packed met- chloride ions in these reactions, the carbido als (3). The advantage of the strategy employed dianion [RU~C(CO)~~]*-was treated with in the synthesis of these copper-ruthenium CuCl, instead of the [Cu(NCMe)J+cation, clusters is that by carefully controlling the reac- and [ {Ru,C(CO),,)2Cu,Cl,]2~,another high tion conditions, nanosized particles with

Fig. 14 The structure of the dianion [{hC( C0)w) iC~,Clz]*

Platinum Metals Rev., 1998, 42, (4) 153 the species [OS,,H~,C~(CO)~,]”’(n = 1-3, m = 1-4) (26) have been characterised, and it is not possible to assign realistic oxidation states for the individual mercury atoms in these species. For example, in [OS~,H~,C~(CO),,]~-,in order to balance the formal -4 charge from each “OS,C(CO)~,”fragment, each mercury atom would have to be assigned an unrealistic oxidation state of +3. The network of reversible redox transformations shown in Figure 15 confirms that this series of clusters can act as “electron sinks” (26) with a description of the bonding within the metal core best described terms Fig. 15 The network of reversible redox in transformations of [Os,,Hg,,C,(CO),,]”’- of delocalised molecular orbitals. (11 = 1-3, m = M),Fr = ferroeene Clusters as Nanoparticle Precursors For the chemistry outlined above it is clear particular ruthenium:copper ratios can be that it is now possible to prepare a wide vari- obtained in high yields. This control has not ety of bimetallic, nanosized clusters in good yield been evident in previous studies (3). with specific, known ratios of the two metals. In principle, this strategy can be applied with- Some Electrochemical out difficulty to other combinations of transi- Considerations tion metal atoms, such as palladium-rhodium If higher nuclearity bimetallic clusters become and platinum-rhodium, and high nuclearity “metallic” in character they would be expected clusters could be prepared. However, would to undergo extensive redox chemistry, with the these systems have real uses with industrial appli- cluster cores behaving as “electron sinks”. For cations? all of the copper-ruthenium clusters described It has long been established that metal clus- above it is possible to assign a formal oxidation ters can be anchored to oxide surfaces such as state of + 1 to each of the copper atoms in the silica and alumina, and even encapsulated in structures, despite the view that the bonding zeolite cages; after heating the residual metal must be delocalised over the metal core. particles have high catalytic activity (33). It is Similarly, for the tubular osmium-gold clus- also known that bimetallic catalysts often exhibit ter [Osin(CO)?,(AuPPh,Me),](Figure 9) each superior operating stability to monometal sys- gold atom can be assigned an oxidation state tems, and experiments have shown that rhenium- of + 1 (29). Cyclic voltammetry studies show platinum clusters, supported on alumina, are that this cluster undergoes two reversible one- effective catalysts for naphtha reforming (34). electron reductions, indicating that there is However in these experiments the exact nature no major change in core geometry with the of the cluster precursors and the catalytically uptake of two electrons (27). This is consistent active materials were not known. with the cluster being able to act as an “elec- Recently, Shapley and co-workers have pre- tron sink” since it is able to reversibly take up pared a set of supported bimetallic catalysts from and release a pair of electrons repeatedly, with- two structural isomers of [RejIrC(C0)2,]’ by out it degrading, or without any major struc- deposition onto high surface area alumina and tural change that would cause the redox process activation in dihydrogen at 773 K (35). The spe- to become irreversible. cific activities of the catalysts depend on both The situation for the osmium-mercury sys- the metal framework structure and the coun- tems is more complicated. As noted earlier, all terion present in the precursor (either [NEt,]’

Platinum Metals Rev., 1998, 42, (4) 154 or [N(PPh,)2]+).Interpretation of EXAFS data described above, had been successfully anchored has enabled specific models to be developed for inside mesoporous silica (37). Activation and the catalyst particle nanostructures which cor- anchoring of the adsorbed cluster on the MCM- relate with their catalytic activities. The more 41 silica support was achieved by heating the active catalysts are modelled by a hemisphere sample under dynamic vacuum. EXAFS spec- of close packed metal atoms, with an average troscopy confirmed the presence of a bimetal- diameter of 1 nm, with iridium at the core. In lic particle anchored to the silica oxygen atoms a series of related studies, Shapley has also shown through the silver atoms of the cluster. High- that [PtRu,C(CO),,] can be used as a neutral resolution electron microscopy of the heat- cluster precursor for the formation of carbon- treated material shows a uniform distribution supported platinum-ruthenium nanoparticles of the bimetallic nanoparticles aligned along the with exceptionally narrow size and composition zeolite channels. The catalytic performance of distributions (36). The bimetallic particles are the activated, supported bimetallic particles obtained by reduction of the carbido cluster with was tested for hydrogenation of hex-1-ene to hydrogen. A detailed structural model of the hexane. Initial experiments showed a high selec- nanoparticles was deduced on the basis of in situ tivity (in excess of 99 per cent) and a turnover EXAFS, scanning transmission electron frequency of at least 6300 mol hexane per mol microscopy, microprobe energy-dispersive X- [Ag,RuIo]per hour. ray analysis and electron microdifiaction stud- The success of these studies led to the ies. These experiments show that the nanopar- incorporation of the copper-ruthenium cluster ticles have a Ru:Pt ratio of 5:1, an average anion, [ {RU,C(CO),,}~CU~CI.']~~,described pre- diameter of approximately 1.5 nm and adopt viously (Figure 14) (32), into the mesoporous a face centred cubic close packed structure. This channels of silica (38). Gentle thermolysis of is in contrast to the stable phase of the bulk alloy the anchored clusters gives the bimetallic which is hexagonal close packed. The EXAFS nanoparticles, characterised by X-ray absorp- studies also show that there is a non-statistical tion and FT-IR spectroscopies, and high-reso- distribution of different metal atoms in the lution scanning transmission electron micro- nanoparticles: the platinum atoms exhibit pref- scopy. The copper and ruthenium K-edge X-ray erential migration to the surface of the particles absorption spectra show that these catalytically under an atmosphere of dihydrogen. active particles have diameters of approximately Of particular interest is a recent report by 1.5 nm and display a rosette-shaped structure Johnson, Thomas and colleagues that a clus- with 12 exposed ruthenium atoms that are con- ter anion [A~,Ru,~C~(CO),,C~]~-(Figure 16) nected to a square base composed of relatively with a structure in which a central Ag, triangle concealed copper atoms. In turn, these are links two Ru, square based pyramids, closely anchored by four oxygen bridges to four silicon related to the copper-ruthenium systems atoms of the mesopore. The nanoparticles are

Fig. 16 The structure of the metal core of dianion: [A~J~&(CO)UC~]*-

Platinum Metals Rev., 1998, 42, (4) 155 active catalysts for the hydrogenation of hex- ity of the osmiudmercury, rutheniudmercury, 1-ene, diphenylacetylene, phenylacetylene, stil- osmiumigold and copperiruthenium systems bene, cis-cyclooctene and D-limonene, with investigated, the mercury, gold or copper atoms turnover frequencies of 22400, 17610,70, 150 form a central domain and the osmium or ruthe- and 360, respectively, at 373 K and 65 bar of nium cluster units are fused onto the periphery dihydrogen. The catalysts showed no tendency of these central units. In no case did the two to sinter, aggregate of fragment into their metallic components become dispersed through- component metals during these experiments. out the metal core. Lastly, evidence is beginning to emerge that nanoparticles derived from Conclusions these and related clusters may prove to be active In this review it has been shown that synthetic catalysts when anchored on silica or alumina strategies to prepare high nuclearity, bimetallic supports. clusters in good yields have been developed. The metal cores of these clusters have dimen- Acknowledgements sions in excess of 1 nm. By careful control of My grateful thanks go to Professor the Lord Lewis reaction conditions it is possible to obtain spe- and Professor Brian F. G. Johnson for their support and encouragement over the years, and for initiating cific target molecules with known ratios of the the research described in this review. I am also indebted two metallic components, and the methodol- to the many research workers in the Department of ogy may be extended further to encompass the Chemistry, at Cambridge, who have carried out the synthetic and structural work described, and to majority of the late transition elements. In the Johnson Matthey for the generous loan of the heavy “condensed” clusters obtained, for the major- transition metal salts.

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Platinuni Metals Rev., 1998,42, (4) 156 16 B. F. G. Johnson, J. Lewis, C. E. Housecroft, M. 27 Z. Akhter, Ph. D. Thesis, University of Cambridge, A. Gallop, M. Martinelli, D. Braga and F. 1995 Grepioni,J. Mol. Catal., 1992, 74, 61; B. F. G. Johnson, M. A. Gallop and Y. V. Roberts,J. Mol. 28 V. Dearing, S. R. Drake, B. F. G. Johnson, J. Lewis, M. McPartlin and H. R. Powell, J. Chem. SOC., Catal., 1994, 86, 51 Chem. Commun., 1988, 1331 17 B. F. G. Johnson and J. Lewis, Adv. Inorg. Chem. 29 Radiochem., 1981,24, 225 Z. Akhter, S. L. Ingham, J. Lewis and P. R. Raithby, Angew. Chem., In?. Ed. Engl., 1996, 35, 18 E. J. Ditzel, B. F. G. Johnson, J. Lewis, P. R. 992 Raithby and M. J. Taylor, J. Chem. SOC.,Dalton Trans., 1985, 555 30 M. A. Beswick, J. Lewis, P. R. Raithby and M. C. Ramirez de Arellano, Angm. Chem., Int. Ed. Engl., 19 J. Lewis, C.-K. Li, M. C.Ramirez de Arellano, P. 1997,36,291 R. Raithby and W.-T. Wong, J. Chem. Soc., Dalton Trans., 1993, 1359 3 1 M. A. Beswick, J. Lewis, P. R. Raithby and M. C. Ramirez de Arellano, Angm. Chem., Int. Ed. Engl., 20 R. Buntem, J. Lewis, C. A. Morewood, P. R. 1997,36,2227 Raithby, M. C. Ramirez de Arellano and G. P. Shields, J. Chem. SOC.,Dalton Trans., 1998, 1091 32 M. A. Beswick, J. Lewis, P. R. Raithby and M. C. Ramirez de Arellano, J. Chem. SOC.,Dalton Trans., 21 D. Braga, P. J. Dyson, F. Grepioni and B. F. G. 1996,4033 Johnson, Chem. Re%, 1994,94, 1585; P. R Raithby and G. P. Shields, Polyhedron, 1998, in press 33 S. Kawi and B. C. Gates, in “Clusters and Colloids. From Theory to Applications”, ed. G. 22 I. D. Salter, Adv. Organomet. Chem., 1989, 29, Schmid, VCH Publishers, Weinheim, 1994, p. 249 299 23 M. Fajardo, H. D. Holden, B. F. G. Johnson, J. 34 J. H. Sinfelt, “Bimetallic Catalysts: Discoveries, Lewis and P. R. Raithby, J. Chem. SOC.,Chem. Concepts and Applications”, Exxon Monograph, Commun., 1984,24 Wiley, New York, 1983 24 L. H. Gade, B. F. G. Johnson, J. Lewis, M. 35 M. S. Nashner, D. M. Somerville, P. D. Lane, McPartlin and H. R. Powel1,J Chem. Sac., Chem. D. L. Adler, J. R. Shapley and R. G. Nuzzo, J. Commun., 1990, 110 Am. Chem. SOC.,1996, 118, 12964 25 P. J. Bailey, B. F. G. Johnson, J. Lewis, M. 36 M. S. Nashner, A. I. Frenkel, D. L. Adler, J. R. McPartlin and H. R. Powel1,J. Chem. SOC.,Chem. Shapley and R. G. Nuzzo, J. Am. Chem. SOC., Commun., 1989, 1513; P. J. Bailey, M. J. Duer, B. 1997,119,7760 F. G. Johnson, J. Lewis, G. Conole, M. McPartlin, H. R. Powell and C. E. Anson, J. Organomet. 37 D. S. Shephard, T. Maschmeyer, B. F. G. Johnson, Chem., 1990,383,441 J. M. Thomas, G. Sankar, D. Ozkaya, W. Zhou, R. D. Oldroyd and R. G. Bell, Angew. Chem., Inz. 26 E. Charalambous, L. H. Gade, B. F. G. Johnson, Ed. Engl., 1997, 36, 2242 T. Kotch, A. J. Lees, J. Lewis and M. McPartlin, Angew. Chem., Znt. Ed. Engl., 1990,29, 1137; L. 38 D. S. Shephard, T. Maschmeyer, G. Sankar, J. M. H. Gade, B. F. G. Johnson, J. Lewis, M. McPartlin, Thomas, D. Ozkaya, B. F. G. Johnson, R. Raja, T. Kotch and A. J. Lees,J. Am. Chem. SOC.,1991, R D. Oldroyd and R. G. Bell, Chem. Eur. 3,1998, 113,8698 4, 1214

Construction of Miniature I1Organo-Rhodium Boxes Many types of molecular cages exist in which C5H5)were used to prepare a series of molec- ions, atoms or molecules can be trapped. These ular “squares”, by reaction with [Cp’RhCl,] or cages are usually held in suspension and are typ- [(cymene)RuCl,] (cymene = 4-isopropyl- ically constructed from bifunctional ligands, with toluene). To assemble the box from the square planar or tetrahedral metal centres at the “squares” the chloride ligands were removed by vertices. Until now there have been no cubic AgPF,. The “molecular boxes” of most inter- shaped organometallic cages. However, if octa- est have the structure [(C5R5)8M8(p-CN),z](M hedral transition metal building blocks could = Rh or Co) and are a subunit of hexa- be constructed, then the assembly of cubic- cyanometalates, of which Prussian blue is one shaped structures should be possible. example. Now, researchers fi-om the University of Illinois The most interestingbox has alternate rhodium have succeeded in constructing a molecular box and cobalt atoms at the vertices, linked by CN from a cubic array of cyano-linked rhodium and groups. Each metal atom can adopt its preferred cobalt octahedra (K. K. Klausmeyer, T. B. octahedral position. The box has edges 5.1 A Rauchfuss and S. R. Wilson, Angew. Chem. long with a volume of - 132 A’, giving enough Znt. Ed., 1998, 37, (12), 1694-1696). space inside to encapsulate a caesium atom. The Tricyanometalates Et4N[Cp’Rh(CN),] and box is also soluble so it could therefore be used K[CpCo(CN),] (where Cp‘ = C5Me5,Cp = for trapping molecules in solution.

Platinum Metals Rev., 1998, 42, (4) 157 Conferences Report Progress in Catalysis llTH INTERNATIONAL SYMPOSIUM ON HOMOGENEOUS CATALYSIS

This series of meetings, which began in 1978, ing functionalised cyclopentadienyl ligands, has regularly drawn around 400 researchers from Me,CpCH,X. The ruthenium complex around the world to discuss new developments [RuCl(Me,CpCH,Cl)(CO),] (I) is sufficiently in homogeneous catalysis. For this eleventh meeting, held from July 12th to 17th, the delegates gathered at St. Andrews University, Scotland, and enjoyed traditional Scottish hos- pitality and a very full programme of both oral and poster presentations. stable to allow the CH,Cl functional group to undergo a wide range of organic transforma- Professor Peter M. Maitlis tions while leaving the parent complex intact. On this occasion, the opening day of the sym- However, the carbonyl and chloride ligands are posium was a celebration of the work of Professor sufficiently reactive to undergo the expected Peter M. Maitlis, marking his 65th birthday and reactions for such organometallic compounds, 45 years of chemical research. The organising for example, substitution reactions. The committee had reflected the global reach of his complexes are active catalysts for the cyclo- influence by inviting speakers from Canada, propanation of styrene with ethyldiazoacetate. Mexico, Japan, Russia and Israel, as well as Europe, including his own group at the Palladium-Catalysed Coupling University of Sheffield, U.K. The topics dis- Reactions cussed covered a wide range of applications of The considerable progress made recently in homogeneous catalysis in organic synthesis (for the area of palladium-catalysed coupling reac- example carbonylation, cycloaddition, addition tions was emphasised by several talks and many to alkenes, oxidation chemistry and C-C cou- posters. J. F. Hartwig (Yale University, U.S.A.) pling). The association of Professor Maitlis’s discussed the use of 1,l’-bis(phosphin0) research with current industrial developments ferrocene ligands for C-C and C-X (X = N or was emphasised in the presentation by M. J. 0) coupling. Mechanistic considerations sug- Howard (BP Chemicals, U.K.) on the iridium- gested that the large bite angle of this ligand was catalysed Ca&aTM process for the carbonylation effective in stabilising the reaction intermediate of methanol to give acetic acid. This has replaced and that increasing the basicity of the phosphine the rhodium (Monsanto) process in plants in the would lead to rate enhancements. This was U.S.A. (from 1995) and more recently in Korea, borne out by the comparison of 1,l’-bis- increasing capacity there from 200 kt to 350 kt (dipheny1phosphino)ferrocene and 1, 1’-bis(di- per annum. Retrofitting of the CativaTMprocess t-buty1phosphino)ferrocene (11) ligands. The in BP plants in the U.K. is underway and on completion the process will account for almost 20 per cent of worldwide acetic acid production. The first new plant using this technology is planned for operation in Malaysia in 2000. The day concluded with a retrospective lec- latter proved to be an effective ligand for the ture by Professor Maitlis, reviewing some of his coupling of aryl chlorides which were otherwise early collaborations. However, he did not deny unreactive. 1,2-Disubstituted ferrocenes are also himself the opportunity to describe some new suitable ligands for this reaction and provide a results on the chemistry of complexes contain- convenient route for varying the substituents on

Platinum Metals Rev., 1998, 42, (4), 158-163 158 each of the phosphorus atoms. A mixed di-t- Friedel-Crafts reaction. Evidence supporting butyl/diphenyl (111) was used for the selective both Pd(O)/Pd(II) and Pd(II)/Pd(IV) cycles as possible mechanisms for Heck reactions was presented during these many presentations and this topic provided some lively discussion.

Polymerisation Catalysts In the area of polymerisation catalysts, R. H. mono-arylation of primary amines. Grubbs (California Institute of Technology, J. M. Brown (University of Oxford, U.K.) U.S.A.) and others described the development described mechanistic studies employing low and application of ruthenium-alkylidene com- temperature heteronuclear NMR to characterise plexes, such as [RuCl,(CHPh) {P(c-C,H,,),},] intermediate species.inthe catalytic cycle for the (VI), for olefin metathesis. Improvements in the Heck reacdon involving oxidative addition, alkene insertion and reductive elimination steps. Factors influencing the insertion of palladium and rhodium into C-X (X = C, H, 0 or halogen) bonds were discussed by D. Milstein weizmann Institute of Science, Israel) for complexes con- preparation of these catalysts have been made taining 1,3-disubstituted aryl ligands (IV) by several groups so that they can now be prepared in high yield, one-pot processes and are available commercially. The initial industrial application of these catalysts will be for the polymerisation of dicyclopentadiene, but due to the ability of the complexes to tolerate water and ('pincer' ligands). The palladium complexes are the presence of a wide variety of functional highly stable catalysts for Heck reactions. groups further applications will soon follow. The The application of MeO-Biphep ligands (V) use of this type of catalyst for ring closing metathesis in synthetic organic chemistry was described by A. Fiirstner (Max-Planck-Institut fiir Kohlenforschung, Germany). Using an dlyli- dene complex (also described by P. H. Dixneuf, Universite de Rennes, France, along with other metallacumulenes LRu(C=C,=CRJ]) the synthesis of a number of large ring molecules from M=o@wh2 a,o-dienes was achieved. Functional groups in for enantioselective Heck reactions was described the diene play an important role in the com- by P. S. Pregosin (ETH Zurich, Switzerland), plexing of the olefin to the metal allowing ring while, by contrast, J. G. de Vries (DSM closure to predominate over oligomerisation Research, The Netherlands) described the of the diene. development of phosphine-free Heck chemistry for industrial applications. Through the use of Polyketone Synthesis a decarbonylative reaction with benzoic anhy- The use of palladium catalysts for polyketone dride, the arylation of olefins is possible in good synthesis by alternating copolymerisation of CO yield with easy reprocessing of the reaction by- and olefins is being developed by Shell products (CO and benzoic acid). This elimi- International. Modelling of the reaction inter- nates the environmental problems caused by the mediates was described by K. Vrieze waste streams associated with an equivalent (Universiteit van Amsterdam, The Netherlands).

Platinum Metals Rev., 1998, 42, (4) 159 The use of rigid, potentially terdentate nitro- moisture sensitive or tolerant. The wide choice gen donor ligands (VII) gave very high rates for of quaternary ammonium and phosphonium salts as cations, combined with different anions, such as AICI, , BF,- and organic carboxylates, allows the properties of the solvent to be tuned to suit the needs of a specific reaction, for instance to give easy product separation. The potential of supercritical carbon dioxide, scCO,, as a medium for catalysis was discussed CO insertion. The strain created by the rigid in a number of posters and by a presentation by backbone leads to one nitrogen donor being eas- T. Sakakura (National Institute of Materials and ily displaced to create a site for CO or olefin Chemical Research, Japan). Arylphosphine com- binding. Development of a catalytic system for plexes have inadequate solubility in scCOz for COktyrene copolymerisation and COiethanei satisfactory catalysis, so modification of the phos- styrene terpolymerisation was described by B. phine ligands with perfluoroalkyl substituents Milani (University of Trieste, Italy). With has been used to improve their solubility. These [Pd(bipy),] [PF,], as catalyst, the use of triflu- ligands are also applicable to catalysis in per- oroethanol instead of methanol as solvent fluorohydrocarbon solvents, as described by resulted in significantly greater stability for the A. M. Stuart (University of Leicester, U.K.). catalytic intermediate and hence high produc- Examples of rhodium-catalysed hydroformyla- tivity from the catalyst, and high molecular tion for higher olefins in each of these media weight (-75,000) for the polymer. were given in poster presentations, the main benefit being the easier separation of the product Unusual Solvents from the catalyst. Presentations on catalysis in unusual media as Many other excellent presentations were made solvents reflected the growing interest in this on homogeneous catalysis using platinum group area. K. R. Seddon (Queen's University of metals (pgms) and non-pgm transition metal Belfast, U.K.) discussed the potential of ionic catalysts. This high standard and the sustained liquids. These are good solvents for many interest of the many delegates will no doubt lead organic, inorganic and polymeric compounds. to continued success for these symposia. The They remain liquid over a much wider tem- 12th meeting is scheduled for Stockholm, from perature range than conventional solvents and August 27th to September lst, 2000. by selection of the constituents they may be C. F. J. BARNARD AND W. WESTON

9TH INTERNATIONAL SYMPOSIUM ON RELATIONS BETWEEN HOMOGENEOUS AND HETEROGENEOUS CATALYSIS

The 9th meeting in this series was held in (University of Lyon- 1, France) examined the Southampton from 20th to 24th July 1998 and field of immobilised homogeneous catalysis, a attracted over 200 participants, the vast major- theme that was well represented in the remain- ity coming from overseas. As is often the case, der of the conference. Basset's remarks that syn- the experience and knowledge gained from ergy - as opposed to relations - between homo- studying one type of system can often be applied geneous and heterogeneous catalysis, should be to others, so this Symposium on homogeneous what is considered, were thus rather prophetic. and heterogeneous catalysis, was aimed at help- A highlight of the first day was undoubtedly ing the flow of ideas between these two very sim- the presentation by Richard Lambert (University ilar areas of catalysis. of Cambridge, U.K.) who has developed STM The opening plenary talk, by Jean-Mane Basset (scanning tunnelling microscopy) techniques to

Platinum Metals Rev., 1998, 42, (4) 160 the point where he is able to apply surface use of model catalysts to try to explain catalytic science techniques to fine chemical synthesis. behaviour under real reaction conditions gen- Lambert described the palladium-catalysed erated controversy. However, Whyman’s obser- trimerisation of acetylene to benzene. For the vation that minute quantities ofwater were essen- Pd(0) surface, under low coverage the ben- tial to attain a rate enhancement, although not zene molecules lie flat, whereas at high cover- yet understood, must be relevant to the rate age they are tilted to the palladium surface. enhancements seen under normal operating Several isotopic studies have been conducted conditions. using C2D,to gain insight into the possible Peter Wells (University of Hull, U.K.) pre- mechanism for this reaction. In conjunction with sented molecular modelling which supported several surface techniques, the statistical distri- the generally accepted mechanism for the asym- bution of products has indicated that the mech- metric reaction. The same ideas were also used anism proceeds via a C,H, metallocycle inter- to explain the mechanism for the functioning mediate. Lambert found that the desorption of oxycodone as a modifier, the major differ- temperature for the flat benzene coverage is ence being that a step-site on the metal sur- higher than for the tilted configuration. face is required to enable the enantioselective Using pseudo-real time STM he was able to site to form. identify the likely active site for alkyne coupling Martin Wills (University of Warwick, U.K.) reactions on various Au/Pd surfaces. Extensive spoke on two aspects of the asymmetric reduc- mixing of the two metals occurred around 500°C tion of ketones to secondary alcohols. Firstly and palladium was found to deposit onto the using chiral phosphinamide catalysts in the pres- gold particles in an orderly fashion. The activ- ence of a borane Lewis acid. The catalysts are ity of these particles towards alkyne coupling air- and moisture-stable, with the reactions pro- increased as the palladium coverage approached ceeding in good yield. However, the reactions a monolayer. At a coverage above one mono- require 10 mol per cent of catalyst and high layer the activity began to fall, as the palladium temperature conditions (1 10°C). surface became rough (with steps and terraces, The second part of his talk involved ruthe- and so on) and was no longer the regular nium(I1) catalysed hydrogenation reactions. Pd( 1 1 1) surface. These systems have the advantage of running at room temperature which is advantageous for Enantioselective Hydrogenation less stable ketones. The active species is derived The second day was dominated by enantio- from [RuCl, (p-cymene)] and a hydroxylamine selective hydrogenation. A. Baiker (ETH Ziirich, ligand, such as 1 -amino-2-indanol. The rigid- Switzerland) gave a broad review of the work ity of the indanol ligand structure is necessary performed on the asymmetric hydrogenation of for achieving the desired high stereoselective con- a-ketoesters over chirally modified supported trol, see Figure 1. Enantiomeric excesses (e.e.) platinum metals catalysts during the last decade. of up to 98 per cent have been obtained using His more recent work on the application of the just 1 mol per cent of ligand and 0.5 mol per technology to new reactants, including ketopan- tolactones, (the hydrogenated product of which is useful in the manufacture of vitamins) was also presented. John Bradley (Max-Planck-Institut fur Kohlenforschung, Miilheim, Germany) and Robin Whyman (University of Liverpool, U.K.) reported their respective studies into the use Fig. 1 Ruthenium catalyst giving optimal of colloids as model catalysts for the study of results fur ketone hydrogenation enantioselective hydrogenation. As always, the

Platinum Metals Rev., 1998, 42, (4) 161 cent of ruthenium. Both yield and e.e. were shown to decrease with different, less rigid hydroxylamine ligands.

Polymer Synthesis I Fig. 3 Trimethylsilyldiazomethane (TMSD) A series of ruthenium catalysts for ring opening metathesis polymerisation (ROMP) and ring closure metathesis reactions (RCM) have been and was activated by the carbene precursor, developed by R. H. Grubbs (California Institute trimethylsilyldiazomethane see Figure 3. The of Technology, U.S.A.), who talked at length polymers produced from this reaction have high about his work. Some of the ruthenium carbene stereo-regularity reaching 99 per cent zruns con- catalysts (VI) have been commercialised and are figuration. Even in the absence of stabilising now being sold in kg quantities. phosphines the catalysts are still quite stable. He stated that the activity of the catalyst The activities of these catalysts were not signif- depends on the phosphine ligand. Bulkier groups icantly different to those produced by Grubbs. tend to give higher activity catalysts such that Interestingly, the addition of a phosphine (tri- P(Cy), >P'Pr, > PPh,. cyclohexylphosphine) to the reaction actually Heterogeneous analogues to these systems leads to a decrease in both yield and selectivity. have been attempted by attaching the ruthenium to a phosphine polymer support. Unfor- Clusters in Catalysis tunately the supported phosphine is typically G. Schmid (Universitat GH Essen, Germany) labile and undergoes ligand exchange reactions. spoke of recent developments in the field of This leads to the ruthenium becoming detached metallic cluster catalysis. Cluster molecules can from the support and consequently leaching be thought of as being somewhere between dis- from the catalyst. Grubbs has also incorporated crete molecules and bulk metal. Schmid functionalised phosphine ligands into the cat- explained how the absorbance relaxation of gold alysts to obtain water soluble metathesis cata- clusters changed with size. Au,, clusters exhib- lysts, see Figure 2. Such catalysts require the ited molecular optical behaviour whereas Auss presence of HCl to give acceptable rates and clusters acted like a bulk metal. yields but do offer a great benefit for carrying The transition from molecular to bulk prop- out aqueous phase reactions. erties occurs somewhere between the two clus- L. Delaude (University of Liege, Belgium) con- ter sizes. The different clusters should exhibit tinued with the subject of ROMP catalysts in a properties relating to homogeneous and het- paper on the polymerisation of 2,3-dicar- erogeneous catalysis, respectively. Recently boalkoxy-norbornadienes. The active catalytic Schmid has put clusters into nanoporous alu- species was similar to Grubbs' Ru(I1) carbene, mina membranes. These membranes are formed but without co-ordinated phosphine ligands. The by the anodisation of aluminium and contain catalyst was derived from [RuC12(p-cymene)], small channels running perpendicular to the surface. The pore walls can be functionalised with alkoxysilanes and used to trap catalytically active (cluster) species. These systems are still under development and show good potential for

CIh,.,! Ph gas phase catalysts. R"-/ tl' tl' I PR 3 Ionic Liquids H. Olivier (Institut FranCais du Pktrole, France) Fig. 2 Water soluble ruthenium catalyst with gave a lecture on the use of ionic liquids and functionalised quaternary arnine how they can be used in reactions that involve

Platinum Metals Rev., 1998, 42, (4) 162 complexes or ligands that are either poorly sol- Other novel ideas were presented in the two uble in water or unstable in water. Ionic liquids poster sessions and some of these will undoubt- have been explored as solvents for transition edly mature in time for the next conference in metal catalysts for over 20 years, and used in this series, which is to be held in Lyon, France hydrogenation and hydroformylation reactions in 2001. (DuPont, Texaco, Unilever). A new range of One poster, which won a poster prize was by room temperature non-aqueous ionic liquids R. L. Augustine (Seton Hall University, U.S.A.), (NAILS) were presented by Olivier based on who described the immobilisation of homoge- organic cations (such as quaternary phospho- neous catalysts on high surface area supports nium or ammonium ions) and inorganic anions such as carbon, silica and alumina. It will be (such as AlCl, ,Al,Cl;, BF,, PF;).The transi- interesting to see whether his work will justify tion metal catalysts remain in the ionic liquid, the opening remarks on synergy made by giving the benefits of reduced catalyst consump- Professor Basset. tion and disposal. By changing the combina- The proceedings of this conference will be tions of anions and cations the ionic liquids can published in a special issue of the Journal of be tailored to industrial reactions, thus provid- Molecular Catalysis. ing new solvents for hard or soft metal catalysts. K. E. SIMONS AND A. F. CHIFFEY

Combinatorial Chemistry Identifies Fuel Cell CatalvstJ The combinatorial chemical screening of large samples were characterised by various tech- numbers of samples has received much atten- niques and tested as anode catalysts in DMFCs. tion in recent years, particularly due to its use The best combination was Pt(44)/Ru(41)/ in drug discovery for the identification of new Os(lO)/Ir(5), which had a current density 40 leads, although the approach has been used per cent higher than presently used Pt-Ru at for about twenty years to find new inorganic 400 mV and more than double the value under materials. The technique is now being adapted short circuit conditions. and applied to finding new materials (1). With this method a wide range of composi- Direct methanol fuel cells (DMFCs) have an tions was searched rapidly and thoroughly, allow- advantage over other fuel cells in converting ing areas of apparent inactivity to be investi- methanol directly at the anode to electricity, but gated. In fact, the activity of this particular poor performance has limited their commer- combination does not lie in the expected active cialisation, the major limitations being anode regions. Such optical screening may be useful and membrane performances (2). Combinatorial to identify other electrochemical materials. screening can be used to find more active elec- References trochemical catalysts, but presently-used current-voltage methods are time-consuming and 1 Chem. Week,Aug. 12, 1998, 501, p. 18 2 M. P. Hogarth and G. A. Hards, Platinum Metals cumbersome for such large numbers of sam- Reo., 1996, 40, (4), 150 ples. In other combinatorial screenings, a flu- 3 E. Reddington, A. Sapienza, B. Gurau, R. orescent indicator has been used to detect the Viswanathan, S. Sarangapani, E. S. Smotkin and presence of ions (such as H+), the intensity of T. E. Mallouk, Science, 1998, 280, (5370), 1735 the fluorescence being an indication of activity. Now, fluorescent detection and combinator- The Development of the Platino-Calixarenes ial chemistry have been used by scientists at the January 1998 issue of Platinum Metals Pennsylvania State University, Illinois Institute In of Technology and ICET in Massachusetts to Review, on page 15, right hand column, the sev- identify a combination of platinum group met- enth line should read “obtained by reacting complex with 4,4’-bipyridine, see Scheme the als with improved properties, which they say 3 v.” In legend of Scheme V L* must be replaced by 3. may be used as the anode in a DMFC (3). Platinum, ruthenium, osmium, iridium and Polymers of Platinum Metals Complexes rhodium were combined in a 645-electrode Immobilised on Electrodes array, deposited onto carbon paper and screened In the April 1998 issue of PIaFinum Metals Rmkw, in a methanol/fluorescent indicator medium. on page 6 1, right hand column, the thirteenth The most active components were selected; bulk line should read “[Rh(bpy)(PPhzEt)z(CI)(H)]”’.

Platinum Metals Rev., 1998, 42, (4) 163 Catalysts for Butane Reforming in Zirconia Fuel Cells By K. Kendall and D. S. Williams Birchall Centre for Inorganic Chemistry and Materials Science, Keele University, England

The ability of fuel cells to use hydrocarbon fuels efficiently is important if they are to compete with battery power. Solid oxide fuel cells, particularly zirconia fuel cell devices, are generally well suited to utilise a variety of fuels. They are commercially attractive, especially in remote locations where battery supply and muintenunce costs are prohibitive but wherefwl, particularly butane, is readily available. Butane can be safely stored at high energy density and is thus a useful fwlfor zirconia fuel cells in remote areas. Partial oxidation would be the preferred route to reform butane, but this requires a suitable catalyst. Ruthenium is an excellent partial oxidation catalyst, giving nearly total reformation of butane and producing high levels of hydrogen. However, problems such as carbon deposition and catalyst optimisation need to be addressed. Here, work with a zirconia fuel cell successfully fuelled by butane and using a ruthenium catalyst under controlled reaction conditions is discussed.

Zirconia fuel cell devices can be small-scale such as formaldehyde or butadiene (8,9).Such and portable. They can generally use a variety products are not suitable as feeds for fuel cells. of fuels, including hydrocarbons, since they are Therefore, new catalysts must be found to con- not susceptible to carbon monoxide poisoning. vert the butane to synthesis gas - the preferred They do not require external reformation of the form of butane reaction product for fuel cell use fuel. (10): Butane is a particularly attractive fuel because C,H,, + 20,+ 4CO + 5H, (1) it is cheap, easily stored and is available at remote sites, where battery power is expensive. The while preventing the total oxidation of the butane main problem with butane, when fed directly to water and carbon dioxide: into zirconia devices, is its tendency to deposit C,H,, + 6.502 + 4C02 + 5Hz0 (ii) carbon on the fuel cell anodes. A possible solution to eliminate this is by reforming the butane This reaction requires more than simple restric- through the addition of steam (l), carbon diox- tion of the availability of oxygen (1 l), as carbon ide (2), or air to bring about partial oxidation tends to be deposited on the anode during the (3). For the fuel cell device described here par- reaction: tial oxidation of butane by air has been used, as C4H10+ xOz + aCO + bCO, + CC+ dHz + eH,O (i) this provides the simplest device construction. The system in Figure 1 shows the position of where the numbers x, a, b, c, d and e vary the partial oxidation catalyst upstream of the according to the conditions. fuel cell electrodes on the zirconia tubes (4). A number of catalysts are known to convert methane to synthesis gas (1 2-1 6) on a variety Catalytic Reactions of catalyst supports (17-2 l), but methane reacts Partial catalytic oxidation is widely used for in a much simpler way than butane since it has the reformation of butane (5) and other paraf- no C-C bonds to give the intermediate hydro- fins (6,7) to higher value chemical feedstocks, carbon products formed by butane. Even so,

Platinum Metak Rev., 1998, 42, (4), 164-167 164 Partial Oxidation catalyst Fuel cell electrodes I

Ztrconia tubes

Thermal insulation /

Fig. 1 Butane powered zirconia fuel cell system showing the butane supply, valve and veuturi passing the butanelair premix into zirconia tubes containing the ruthenium catalyst, then to the fuel cell electrodes and the platinum oxidation catalyst for the spent fuel. Excess fuel is converted by the platinum to generate heat for the fuel cell operation

there are ten principal reactions of methane (22), and helium carrier gas to measure the concen- and correspondingly more with butane. trations of hydrogen, carbon monoxide, carbon The purpose of this work, therefore, was to dioxide and C1 to C4 hydrocarbons, before the find a catalyst formulation capable of favouring gas entered the fuel cell section. the production of synthesis gas from butane. The catalysts investigated were those already known to produce synthesis gas from methane, Catalyst Materials that is: nickel, ceria, platinum and ruthenium Various catalyst materials were tested in the (23), supported on &alumina fibres (Saffil, ICI) rig shown in Figure 2. By separating the cata- mounted in a nickel support within a stainless lyst from the fuel cell, better control of the exper- steel reactor tube. The reactor temperature was imental conditions was possible than in Figure controlled between 600 and 850°C. 1. Product gas from the catalyst could be Three conditions were found to be necessary analysed by gas chromatography, with ther- for the successful partial oxidation of butane to mal conductivity detection, using both nitrogen synthesis gas:

Catalyst Zirconia fuel cell 650-800% 700-850.C

I Hydrogen . I

Fig. 2 The catalyst test rig r-I sh&iog the. gas supplies, thi Butam daloxidation catalyst and I ;he fuel cell test uni;. GC is the gas chromatographyunit

Platinum Metals Rev., 1998,42, (4) 165 the correct catalyst the correct temperature and the correct butane:air ratio. The amount of butane conversion and hydrogen generation for the four catalysts tested at 700°C is shown in Figure 3. It can be seen that ceria and nickel catalysts were not much more efficient than the reactor tube without catalyst: only about 40 per cent of the fuel was converted and hydrogen production was less than 55 per cent of its potential. Significant quanti- 650 760 750 8k 850 ties of butane and intermediate hydrocarbons TEMPERATURE, .C remained in the product gas, causing severe Fig. 4 Optimised values for output gas coking problems. composition at various temperatures for two Platinum yielded the highest butane conver- butane:air ratios sion rate but tended to push the reaction through to total oxidation, giving predominantly carbon dioxide and water, and much coking. Ruthenium negligible coking was observed and the output was the best catalyst, giving a high butane con- gas had a high hydrogen content and sufficient version, and generating 80 per cent of the pos- carbon dioxide to assist in reforming any resid- sible hydrogen. Optimum performance condi- ual hydrocarbons, downstream on the fuel cell tions for the ruthenium system were therefore anode. investigated more fully. Reformed output produced under optimised conditions was fed to a zirconia fuel cell tube Optimisation of the Ruthenium which had a nickel cermet anode and a lan- Catalyst Performance thanum strontium manganite cathode, main- The temperature of operation of the ruthe- tained at 850°C.Electrical power could be drawn nium on alumina catalyst was tested over the from this cell at 0.7 volts, which compared favor- range 600 to 850°C with various butane:air mix- ably over short term tests with results obtained tures. The optimum temperature range was using pure hydrogen fuel. Although there were found to be 750 to 800°C at a butane:air ratio some current fluctuations, the power output was of 1: 10, see Figure 4. Under these conditions, maintained over a period of several hours. By contrast, non-optimised conditions resulted in erratic and rapidly diminishing performance with time, as the cell then coked up almost immediately. The effect of using a ruthenium catalyst was [7 Hydrcgen generation demonstrated dramatically in Figure 5. Here, using the apparatus of Figure 2, the catalyst in the partial oxidation unit was varied. When alumina fibre was used as a reference with hydrogen as the fuel gas, a good fuel cell output was observed, as expected, over many hours, shown by the horizontal line in Figure 5. However,

NO catalyst Ceria Nickel Platinum Ruthenium when hydrogen was replaced by a mixture of butane:air in a 1:lO ratio and passed over the Fig. 3 Catalyst performance in terms of butane conversion and hydrogen generation alumina fibre support, the fuel cell failed within 5 hours, as is shown in Figure 5.

Platinurn Metals Rev., 1998, 42, (4) 166 increased to a higher value than with hydrogen. /------The ruthenium catalyst was thus seen to Hydrogen / 7: \ promote the partial oxidation of butane. 4 roo.+ , >-€\ / Nickel + ruthenium reformer E \-/ Conclusions 6 -I.--.- Butane can be successfully converted by a I- so. -* ruthenium catalyst for use in zirconia fuel cells. w *-I-- The optimum conditions are to employ par- a Alumina reformer-- . U -- tial oxidation of the butane above 750°C at a --\. 1: 10 butane:air ratio with the ruthenium supported on alumina. The fuel cell performance is then comparable to the output obtained when Fig. 5 The zirconia fuel cell performance at using hydrogen, and the deposition of carbon 0.7 V output and 850C, comparing hydrogen on the catalyst and the cell is eliminated. with butane reformate and showing the advantage of using a ruthenium over alumina As it is known that methane conversion to syn- catalyst. The downwards sloping dotted line thesis gas by ruthenium is aided by using tita- shows the failure of the cell using a butaneair nia as the support material (17), the effects of mixture over alumina fibre other support materials, including zeolites and lanthanides (24), are going to be tested and the influence of the catalyst support on the prod- After coating the alumina fibre catalyst sup- uct characteristics will be examined in long term port with 10 weight per cent ruthenium, and evaluation of the system. repeating the procedure, the fuel cell initially gave a slight drop in performance on switch- Acknowledgements Funding for this research was provided by Adelan ing from hydrogen to the butane:air mixture. from a SMART award. Advice and assistance were However, after a short time the power output provided by T. Alston, M. G. Palin and J. Z. Staniforth.

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Platinum Metals Rev., 1998,42, (4) 167 Geoffrey Wilkinson and Platinum Metals Chemistry By M. L. H. Green University of Oxford, England and W. P. Griffith Imperial College of Science, Technology and Mrtlic.inr. London

At this time, the second anniversar?,of Geoffrey WZkinson’s death on 26th September 1996, his work and influence on the development ojinorganic chemistry and the chemistry of the platinum group metals are recalled by two of his former students and colleagues. Geoffrey Wilkinson’.s early life and career, important areas of his platinurn metals research and work leading to the award in 1973 of the Nobel Prize are surveyed. He is remembered by his relationship with Johnson Matthex his work at Imperial College and by affectionute anecdotes,from the laboratory

Professor Sir Geoffrey Wilkinson, F.R.S. (or of his ex-students came to work for it. On his Geoff as he was always called by his students twice-yearly visits to the Technology Centre in and colleagues) was one of the greatest inter- Sonning Common he would always take a plas- national post-war inorganic chemists; he made tic shopping bag filled with platinum metals remarkably original contributions to many areas residues, garnered from his research group and of transition metal chemistry, especially homo- from his colleagues - the used materials from geneous catalysis, organometallic and co-ordi- the loan scheme. nation chemistry. His research career, spanning On his retirement in 1988 to become Professor some 54 years, involved well over half of the ele- Emeritus, Johnson Matthey expressed their ments of the Periodic Table - he worked with appreciation of this mutually productive rela- almost every d-block transition metal, most of tionship by providing Geoff with the spacious the lanthanides and some of the actinides and Johnson Matthey laboratory at Imperial College. main group elements. Much of his work con- Here he continued very productive work with a cerned the six platinum group metals, and indeed small, creative team to the day before his death. many of his most important discoveries involved In 1964 Geoffrey Wilkinson wrote an article them. Ofhis 557 publications (l), well over one for Platinum Metals Review on platinum group third are concerned with the platinum metals. organometallic n-aromatic complexes (2). This article, however, preceded his important dis- The Johnson Matthey Connection coveries in the catalytic chemistry of these ele- The platinum metals Geoff used were invari- ments. As a fuller account of Geoff’s chemistry ably supplied by Johnson Matthey through the has already been published (l), this report will loan scheme (inaugurated in 1955 by his great focus on his life and work with the platinum friend, the late Frank Lever). This scheme has metals in the order of their interest to him, list- done much to foster university research in plating items published in Platinum Metals Review. inum metals chemistry in the U.K. and overseas. Over the years Geoff developed a close Early Life and Education connection with Johnson Matthey: not only were Geoffrey’s grandfather (also Geoffrey there the patents (involving for the most part Wilkinson) came to Todmorden, a small ‘cot- his rhodium catalysts) and consultancy, but also ton town’ in the West Riding of Yorkshire, close he had many kiends in the company - and some to Lancashire, from the Yorkshire town of

Platinum Metals Rev., 1998, 42, (4), 168-173 168 Professor Sir Geoffrey Wilkinson 1921-1996 A Yorkshireman by birth, Geoffrey Wilkinson started his working life, during World War 11, on the atomic bomb project in Canada and then the United States. He returned to England in 1956 to the Sir Edward Frankland Chair of Inorganic Chemistry, at Imperial College in London. He was awarded the Nobel Prize for Chemistry in 1973

Boroughbridge. Geoffrey’s father, Harry, better taught. Geoff won a County Scholarship married Ruth Crowther, a weaver, and Geoffrey in 193 1 to Todmorden Secondary School (later was born on 14th July, 1921, the first of three Todmorden High School). A remarkable num- children, in the village of Springside on the ber of its pupils later became famous, including outskirts of Todmorden. Sir John Cockcroft, who worked with Rutherford In 1926 the family moved into Todmorden, at Cambridge and was to become, in 195 1, the which lies at the junction of three deep valleys first of the school’s two Nobel Laureates. Geoff in the heart of the Pennines, where the sur- made exceptional progress and in 1939 won a rounding moors rise 1000 feet above the town. Royal Scholarship to the Imperial College of The present population of 13,000 is about half Science and Technology, London University. that before the decline of the cotton industry, At Imperial his main subject was chemistry but there is still a strong local pride and sense but he also studied geology as an ancillary of community which Geoff shared all his life. subject, indeed in those early days he almost His eyes would light up when he spoke of “Tod” gave up chemistry in favour of geology. He or of the superb countryside close by. He often graduated in 1941 with a first class honours returned to the town to see friends and family, B.Sc. degree, the top student of his year, and and enjoyed walking and climbing in the area, went on to do a Ph.D. under H. V. A. Briscoe in the Lake District and the Yorkshire Dales. (at that time the only Professor of Inorganic Geoff‘s interest in chemistry began early. At Chemistry in the country) on “Some Physico- the age of six he was fascinated to see his father chemical Observations on Hydrolysis in the - a house painter and decorator - mixing his Homogeneous Vapour Phase”. This rather materials. His uncle managed a factory making Delphic title conceals the fact that the main sub- Epsom and Glauber’s salts in Todmorden, and strate studied was phosgene (Geoff later Geoff would recall how he loved to go on remarked that Briscoe “directed his Ph.D. Saturday mornings to tinker in the small labo- research from a safe distance”). ratory at the factory. Indeed, the family hoped In 1942 he was selected by the Joint Recruiting that he would eventually become its manager. Board as a scientific officer at the Atomic Energy His parents, like most people at that time, had project in Canada, and sailed to Halifax, Nova left full-time education by the age of 12 and they Scotia in January 1943. In Canada he worked were determined that their children should be at the University of Montreal and then at Chalk

Platinum Metals Rev., 1998, 42, (4) 169 River, Ontario, on nuclear fission with many this day. Twenty years later Geoff wrote a vivid celebrated scientists -John Cockcroft (from his personal account of the discovery (4). From old school), Bertrand Goldschmidt, Charles 1952 to 1953 he made a number of other Coryell, Alfred Maddocks (later to go to bis(cyclopentadieny1) complexes, including those Cambridge), Jules Gueron and Pierre Auger of ruthenium, rhodium and iridium. During this being amongst them, and two scientists later period he used the fledgling technique of nuclear convicted of being spies for the Soviet Union, magnetic resonance (NMR) to show that cova- Alan Nunn May and Bruno Pontecorvo. lent metal hydrides (in this case Cp2ReH)gave After the war Geoff returned briefly to Britain high-field ‘H NMR shifts. This was crucial to and then went to the Lawrence Livermore his later work on rhodium hydrido complexes Laboratory at the University of California, and their catalytic properties. Berkeley, to work with Glenn T. Seaborg on the production of neutron-deficient isotopes of the Return to Imperial College transition elements and the lanthanides. It was In 1955 Geoff was appointed to Briscoe’s old

said by Seaborg (and Geom that he made more chair at Imperial College ~ still the only estab- artificial isotopes - eighty nine - than anyone lished chair of inorganic chemistry in Britain - has ever made. From this time he started to and arrived there in January 1956. At 34 he was amass his vast knowledge of descriptive inor- one of the youngest professors that the College ganic chemistry, since in those days it was essen- has ever had, and here he did most of his plat- tial for nuclear chemists to have a profound inum metals work. It is tempting to trace this knowledge of the chemistry of the transition profound interest in platinum metals chemistry metals, the lanthanides and the actinides in order to his wartime and early peacetime radiochem- to devise appropriate means of separating and ical work, when he had made new radioisotopes identifying the products of nuclear fission reac- of rhodium and ruthenium. However, it is much tions. One of his nuclear transmutations was more likely that his fascination with these met- that of platinum into gold, which caught the als derived from his early experience and knowl- public imagination after a report in 1948 in the edge of their general chemistry, and in partic- ‘San Francisco Chronicle’ (“Scientist discovers ular with the remarkable versatility of oxidation gold mine in the cyclotron”). state changes exhibited by the metals, later In 1950 he went to M.I.T. and turned to co- harnessed for his catalytic work. ordination chemistry research. His first paper on this concerned the isolation of the unusual Rhodium Chemistry zerovalent complex, [Ni(PCl,),] (3). In 1951 he Geoff once said that much of his chemistry was appointed Assistant Professor of Chemistry concerned the ‘three Rs’ - rhodium, ruthenium at Harvard, and it was here that he did the and rhenium. At Berkeley, as part of his radio- research on ferrocene and other cyclopentadi- chemical work, he isolated the short-lived ‘%h, enyl compounds which was to lay the corner- one of the many fission products of ‘W, and stone of his Nobel Prize. In 1976, after this in 1953 he made salts of the [CpzRh]’ cation. award in 1973, he received his knighthood. Then in 1961, in work that he himself carried out, he reacted cis- and tr~ns-[RhCl~(en)~]’with The Structure of Ferrocene and sodium borohydride in aqueous solution to give Early Platinum Metals Work [RhHCl(en)’]’ (detected by the high-field shift In 1951, the joint recognition by Wilkinson of the hydridic proton by ‘H NMR) (5). It was and R. B. Woodward of the unique “sandwich” on this occasion that he rushed into the labo- structure of ferrocene (bis(cyclopentadienyl)iron, ratory, demanded a Bunsen burner and a test Cp,Fe) was perhaps the most crucial point in tube, and returned later with the tube full of a his career; it launched the new wave of ‘organo- foaming brown liquid which he brandished transition metal chemistry’ which remains to about, calling “Who wants a Ph.D?” This early

Platinum Metals Rev., 1998, 42, (4) 170 work led to a paper on the isolation of was RhH(CO)(PPh,),. Nowadays most of the [RhH2(en),](BPh,), and the establishment of butyraldehyde used for synthesis of bis(2-ethyl- the reduction of quinone to quinol by hydride hexyl)phthalate, a plasticiser for PVC, uses transfer from [RhH(trien)Cl]+.In collaboration RhH(CO)(PPh,), as the catalyst. with that wizard of platinum metals chemistry, The early hydrogenation and hydroformyla- A. R. Powell of Johnson Matthey, salts of tion work was documented in a short article in [~UIH(NH,)~]’’and [RhH(H20)(NH,)4]”were this journal exactly thirty years ago, with fuller isolated; these materials were used to prepare papers in 1975 and 1988 (9). There is no doubt hydrido complexes of ethylenediamine and that this catalysis work, together with his work propylenediamine (6). in so many other areas, contributed to his Nobel prize of 1973, though the citation was for “sand- Hydrogenation and Hydroformylation wich” compounds. with Rhodium Complexes Geoff’s work on this topic has revolutionised Other Work with Rhodium our view of homogeneous catalysis effected by One of Geoff‘s major fascinations (foreshad- transition metal complexes and constitutes some owed in his only paper in this journal (2)) was of his most celebrated work. It is well reviewed with homoleptic alkyl and aryl complexes, mainly in articles by his graduate student, Fred Jardine, of the early transition metals. In 1968 he made who was the first to isolate the compound [Rh(CZHj)(NH,)5]”and, much later, in 1988 RhCI(PPh,),, universally known as Wilkinson’s and 1990, isolated salts of the remarkable methyl catalyst (7). complex [Rh(CH,),]’ and of the dimeric oxo- In 1965 Geoff reported that catalytically small bridged neopentyl complex R~&I-O)~[CH~C- amounts of reducing agents (such as hypophos- (CH,),],, respectively. Another achievement was phorous acid, zinc amalgam and dihydrogen the synthesis in 1991 of Rh(mesityl),, which has itself) would catalyse the otherwise slow sub- a pyramidal structure in the solid state. stitution reactions of rhodium(II1) complexes. He had earlier shown that RhCl,.nH,O would Ruthenium Chemistry absorb dihydrogen and convert hex-1 -ene Ruthenium he called “an element for the con- to hexane, and in 1965 he found that fac- noisseur’’. Again his first approach to this metal RhCI,(PPh,), would convert hex-1-ene to n- was via its radiochemistry in his early work in heptaldehyde, with dihydrogen and carbon Canada and the United States, followed by the monoxide under pressure at 55°C. However preparation of ruthenocene Cp,Ru and the RhCI,(PPh,), is difficult to make, and it was dur- ruthenicinium [Cp,Ru]+cation as a logical fol- ing an attempt to make some that RhCI(PPh,), low-up to his classic ferrocene paper. was produced. This compound was a much more In the 1960s he isolated a number of ruthe- effective catalyst for the hydrogenation of alkenes nium(I1) and (111) complexes of phosphines, and alkynes and also hydroformylated hex-l- arsines and stibines, including RuX,(LPh,), (X yne to n-heptaldehyde and 2-methylhexalde- = C1, Br; L = P, Sb) and RUX,(LR,)~(CH,OH) hyde. RhCl(PPh,), was made from the surpris- (L = P, As). These were precursors for many ingly simple reaction between RhCl,.nH,O in other complexes with a wide variety of ligands, ethanol with excess triphenylphosphine. It is such as dithiocarbamates, amines, nitriles and described in a classic paper of 1966 (8). carboxylates, and a number of them had use- Although RhCI(PPh,), is a hydrogenation cat- ful catalytic activities. Another highlight was the alyst (and subsequently chiral analogues were isolation of the first paramagnetic second-row developed by others for asymmetric synthesis, transition metal complexes, Ru2(OCOR),C1 (R for example for L-Dopa) Geoff later showed that = Me, Et, n-Pr). A variety of carboxylato com- it was not a hydroformylation catalyst, and that plexes of the form RuH(OCOCH,)(FPh,), were the compound responsible for the latter process found to be efficient hydrogenation catalysts for

Platinum Merals Rev., 1998, 42, (4) 171 The Nobel Prize for chemistry awarded to Sir Geoffrey Wilkinson in 1973 for his work on “sandwich” compounds

in 1982. His most celebrated work with osmium however lay with the aryl and imido complexes -he liked to refer to such highly unusual species as “text- book cases”. He made the alkyl complexes Os(VI)O(CH2SiMe,), and also the dimeric neo-pentyl OS*(vI)(O~CCHI)~(CH~S~M~J)+ In 1984 the tetrakis phenyl com- alk-1-enes. A review of this and other work on plex Os(IV)Ph, was isolated and in 1988, the ruthenium carboxylates has been described by tetrahedral complexes Os(IV) (2-CH3C,H,), and Steve Robinson, one of his former students ( 10). [Os(V)(2-CH,C6H,),]+were prepared. At that His later work with ruthenium was also very time, tetrahedral co-ordination was unprece- productive. In 1986 the novel aluminohydride dented for the tetra- or pentavalent oxidation complexes L,HRuAIH(p-H),AlH(p-H)2RuHLj states of second or third-row transition elements. (L = PMe,, PEtPh2, PPh,) were obtained from For imido chemists, the ‘Holy Grail’ was the RuClL and lithium aluminium hydride. In the isolation of a homoleptic complex containing mid-1 980s he isolated the alkyl complexes the =NR ligands, and in 1991 Geoff achieved RU~(IV)(~-O)~%(R = neopentyl, CH,SiMe,), this with the isolation and structural character- the tetrahedral homoleptic RuR., (R = o- isation, by electron diffraction, of the tetrahe- CH,C,H,, mesityl), salts of [Ru(CH,),]’-, and dral tertbutylimido complex Os(1V) (NBu),. some unusual ruthenium(n3 and (V) imido complexes. Alkyl complexes had become of increas- Iridium Chemistry ing interest to him; in fact, his Nobel Prize award Geoff did some work in the late 1960s on “irid- speech in 1973 was entitled “The long search ium iodate” (13), but he then seems to have for transition metal alkyls” (1 1) and in 1993 he neglected the metal until 1989 when he isolated wrote a review paper on the homoleptic alkyls salts of [Ir(CH,),]’-. and aryls of the platinum group metals ( 12). In 1991 he made the tetrahedral complexes Ir(IV)R.,, where R is a sterically hindered aryl, Osmium Chemistry such as 2-tolyl, 2,5-xylyl; and in 1992 he made Although he made ruthenocene and the Ir(mesityl),. In the same year he made ruthenicinium cation in 1952, soon after his fer- Ir(mesityl), which, like its rhodium analogue, rocene work, it was E. 0. Fischer (with whom has a pyramidal structure in the solid state. Also he shared the Nobel Prize) who first made in 1992 he isolated Ir(mesityl)2(SEt2)2,a very osmocene, Cp20s,in 1958. Geoff‘s first paper rare example of a planar iridium(I1) complex, at Imperial College concerned K[OsO,N], but by reaction of mer-IrC1,(SEt2),with the Grignard apart from this he came to osmium chemistry reagent Mg(rnesityl),(SEtJ2. relatively late in his research career. In the 1980s he made the acetato complexes: Palladium and Platinum Chemistry [Os(OCOCH3),(PMe~)llCl, OS~OCOCH,),C~@Y), Of the six platinum group metals, palladium and sky-blue K[OsO2(0COCH,),].2CH,COOH, and platinum received far less attention from the X-ray crystal structure of which was obtained Geoff than did the other four, perhaps because

Platinum Metals Rev., 1998, 42, (4) 172 these elements are less versatile in their oxida- which he would dismiss as ‘stamp collecting’. tion states and also, perhaps, because other well- Sometimes when a reaction seemed not to be known chemists in the country were doing much working he would offer the suggestion “Why palladium and platinum work. But, between don’t you goose it up” meaning, raise the tem- 1966 and 1970, he did show that the zerovalent perature. Geoff was not sympathetic to theo- complex Pt(PPh,), reacts with CS, to give retical chemistry and would often cite the story Pt(PPh3)z(CSz), while the reaction of of how the brilliant young Harvard theoretician Pt(PPh,)2(0,) with CO, CO, and CS2yielded Bill Mofitt had advised him that bis-benzene Pt(PPh,)2(C0,), Pt(PPh,),(C04) (a peroxocar- chromium would be unlikely to be stable. E. 0. bonate) and Pt(PPh,),(OZCS2), respectively. Fischer shortly afterwards reported this famous compound. Wilkinson the Man Geoff was always in a great hurry to publish For both of the authors of this article, Geoff new results and, from time to time, this led to was an academic supervisor in the late 1950s. errors; one example was the reaction product We wrote, in our joint obituary of him for ‘The between thiophene and iron pentacarbonyl Independent’: “The spirit in his research group which was published as thiopheneirontricar- was more like that of an urgent gold rush in bonyl. Gordon Stone later showed that there the West than the scholarly and disciplined calm was no sulfur present and the product was the expected in academia.” (14). If anything this unexpected butadieneiron tricarbonyl. Geoff understates the truth: he expected his students was not given to sulking over such matters but to work as hard as he did - seven days a week looked forward to the next new compound. or at least six, from early morning to late evening. Geoff was a doughty fighter for chemistry in He was, however, not a slave driver and was gen- the U.K., writing in blunt style to Prime erally tolerant of eccentric behaviour. When Ministers, ministers of education, vice chan- thwarted or stirred he made creative and inge- cellors and others charged with the care of fun- nious use of expletives - quite unsuitable for damental scientific research. He would refer quotation here - and he always had a ready sense to such powerful people in administration of fun. His enthusiasm was always infectious, dismissively as “the apparatchiks”. and he was an excellent raconteur and anec- Geoffrey Wilkinson was a remarkable scien- dotalist, with a remarkable memory. In those tist and an unforgettable person. His belief that days (the late 1950s) Geoff would often emerge innovative and creative synthesis is a powerful from his office in the late afternoon and wander tool for new chemistry is borne out by his vast up to each student in turn and say “Well, what’s range of scientific achievements. His legacy to new?”: his whole ethos being the search for some his former students and his enthusiastic influ- new aspect of chemistry. ence on chemistry have given us all many long- He was a severe critic of derivative chemistry term, far reaching benefits.

References 1 M. A. Bennett, A. A. Danopoulos, W. P. Griffith 7 F. Jardine,Rhodium Express, 1997,16,4;F. Jardine, and M. L. H. Green,J. Chem. SOC.Dalton Trans., Prog. Inorg. Chem., 1981, 28, 63 1997,3049 8 J. A. Osborn, F. H. Jardine, J. F. Young and G. 2 G.Willdnson, Platinum Metals Rev., 1964,8, (l), 16 Wil!&son,J. Chem. Soc. (A), 1966, 171 1 Platinum Metals Rev., J. 3 J. W. Irvine and G. Wilkinson, Science, 9 1968, 12, (4), 135; F. 195 1,113, Smith, op. cit., 1975,19, (3), 93; M. J. H.Russell, 742 op. cit., 1988, 32, (4), 179 4 G. Wilkinson, J. Organomet. Chem., 1975,100, 10 A. Dobson and S. D. Robinson, Platinum Metals 273 Rev., 1976, 20, (2), 56 5 G.Wilkinson, Proc. Chem. Soc., 1961, 72 11 G.Wilkinson, Nobel Foundation, 1974 6 K.Thomas, J. A. Osborn, A. R. Powell and G. 12 G. Wilkinson, Sci. Progress, 199314, 71, 15 Wilkinson,J. Chem. Soc. (A), 1968, 1801; A. R. 13 Platinum Metals Rev., 1969, 13, (4), 152 Powell, Platinurn Metals Rev., 1967, 11, (2), 58 14 “The Independent”, October 1, 1996

Platinum Metals Rev., 1998, 42, (4) 173 ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES Face-Coordinated C, Complexes with Carbido Peutarutheuium Cluster Cores Including The Pd I Spectrum, Term System, Isotope a Bimetallic Platinum-Pentaruthenium Shift and Hyperfine Structure - Revised and Complex Extended Analysis Based on FTS Emission K. LEE and J. R. SHAPLEY, Organometallics, 1998, 17, Spectroscopy (14), 3020-3026 R. ENGLEMAN, U. LITZEN, H. LUNDBERGandJ.-F. WART, The interaction of C,,, with RU,C(CO),~or PtRusC- Phys. Scr., 1998, 57, (3), 345-364 (CO),,(COD) in hot chlorobenzene, followed by treat- The spectrum of a neutral Pd atom emitted from hol- ment with solubilising phosphines, gave compounds low cathode discharges was studied by Fourier trans- with a hexahapto co-ordination of C,,) to a Ru, face form spectroscopy in the 1750-55000 tf region. 684 of the square pyramidal Ru,C or octahedral PtRu,C lines were identified as transitions between 67 even cluster framework. The C,,-cluster bond is robust. and 76 odd levels. Isotope shift and hyperfine structure were seen and interpreted in 24 lines. Forbidden Convergent and Divergent Noncovalent lines caused by Stark-effect mixing were observed. Synthesis of Metallodendrimers Most Pd I lines below 64000 cm-' are now known. W. T. S. HUCK, 1.. 1. PRINS, R. H. FOKKENS, N. M. M. Formation of Thin Single-Wall Carbon NIBBERING, F. c.J. M. VAN VEGGELand D. N. REINHOUDT, J. Am. Chenz. SOL.,1998, 120, (25), 6240-6246 Nanotubes by Laser Vaporization of RhlPd- Graphite Composite Rod A new building block, with one pyridine and two kinet- ically inert complexed Pd(I1) ions, is reported for con- H. KATAURA, A. KIMURA, Y. OHTSUKA, S. SUZUKI, trolling the assembly of metallodendrimers by a con- Y. MANIWA, T. HANYU and Y. ACHIBA,Jpn. j? Appl. Phys., vergent or a divergent route. A double pincer ligand 1998,37, (5B), L616-L618 was cyclopalladated with Pd[CHICN],(BF,)2 and con- Single-wall C nanotubes (1) were prepared in high verted to a neutral bis-I'd chloride complex (1). The yield by laser vaporisation of a Rh/Pd-graphite com- pyridine moiety of (l), covalently attached to the posite rod at 1200°C. Lattice constants of the bundle spacer bridging the two pincer complexes, co-ordi- were found to be 1.&1.5 nm. Nine Raman peaks orig- nates to activated Pd centres. Via pyridine- and cyano- inating from the breathing modes were observed, and based building blocks, dendrons up to the third gen- these frequencies and lattice constants indicate the eration were assembled and characterised, by divergent presence of the (1) indexed from (53) to (8,s) which and convergent routes, respectively. are thinner than (1) obtained with a NiiCo catalyst. Preparation and Structure of [Ru(CO),- CHEMICAL COMPOUNDS (PPh3)(q-CsMe5)] [Fe3( ps-C2Bu')(CO)9] M. I. BRUCE, N. N. ZAITSEVA, B. w. SKELTON and A. H. Facile Synthesis of Isomerically Pure cis- WHITE,AUSt. 3 Chew., 1998, 51, (5), 433435 Dichlorodiammineplatinum(II), Cisplatin The reaction between RuCI(C=CHBu')(PPh,)(q- V. YU.KUKUSHKIN, A. OSKARSSON, L. I. ELDING and C,Me,) and Fe2(C0)9 produced the Ru salt N. FARREL Inorg. Synth., 1998, 32, 141-144 [Ru(CO),(PPh,)(q-CSMe,)][Fe,(p,-CZBu')(CO).].X- The rapid and facile one-step synthesis of isomeri- ray structure studies showed a piano-stool structure cally pure cis-[PtCl,(NH,),] (cisplatin), an important for the cation while the anion contained a CCBu' anticancer agent, is described. This involves heating ligand sitting on a triangular Fe, cluster. a mixture of K,[PtCl,], NH,CO,CH, and KCl in H,O under reflux. A Simple and Convenient Synthesis of cis/trans-RuH2(Ph2PCH2PPh,),and of trans- Pd(I1) and Pt(I1) Complexes with RuHCI(Ph2PCHZPPh2)z Chalcogenide Derivatized Phosphathia G. s. HILL, D. G. HOLAH, A. N. HUGHES and E. M. Ligands PROKOPCHUK, Inorg. Chim. Acta, 1998, 278, (2), J. CONNOLLY, A. R. J. GENGE, s. J. A. POPE and G. REID, 22 6-2 2 8 Polyhedron, 1998, 17, (13-14), 2331-2336 Treatment of a suspension of cis-RuC1,(Ph2PCH,Ph,), The mixed phosphine sulfide/thioetherand phosphine (cis-1) in EtOH or 2-propanol with a large excess of selenide/thioether ligands L'-L' react with PdC1, or KOH, gave cisitrans-RuH,(Ph,PCH,PPh,)2(2) in 5 PtC1, in the presence of TIFF, in MeNO, solution 90% yields, with the reaction taking < 2 min in EtOH. to give the distorted square planar complexes A similar reaction with a small excess of KOH gives [Pd(L)](PF,), or [Pt(L)](PF&. The complexes are trans-RuHCI(Ph,PCH,PPh2)2in 64% yield, which can characterised by IR spectroscopy and "'Pt NMR stud- be converted into (2) in moderate yields. Under these ies and the X-ray crystal structure of L' is reported. conditions, (trans-1) is unreactive.

Platinum Metals Rev., 1998, 42, (4), 174-178 174 Ruthenium Nitrosyl Complexes with N- A Catalytic Hydrogen Wave of the Osmium- Heterocyclic Ligands Cysteine System S. DA S. S. BORGES, C. U.DAVANZO, E. E. CASTELLANO, M. KAWASAKI, T. KAKIZAKI, W. HU, K. TOYOTA and J. Z-SCHPECTOR, s. c. SILVA and D. w. FRANCO, Znorg. K. HASEBE, Electroanalysis, 1998, 10, (4), 276-278 Chem., 1998,37, (1 l), 2670-2677 Os(VIII)O, in the presence of cysteine in HC1, exhibits The synthesis of a series of Ru nitrosyl complexes of a well-defined maximum wave at -0.85 V (vs. SCE). formula rrans-[Ru(NH,),L(NO)] (BF,),, where L = The effects of the 0svalence states and the coexist- imidazole, L-histidine, pyridine or nicotinamide, is ing anions on the reduction wave have been studied described. The compounds have relatively high v(N0) polarographically in acidic solution. The high, as stretching frequencies showing that a high degree of opposed to low, axidation states (Os(VII1) and (VI)), positive charge resides on the co-ordinated nitrosyl greatly influence the height of the H, wave. group. The nitrosyl complexes react with OH-. The crystal structure of trans-[Ru(NH,)mi~NO]~(SiF~),PHOTOCONVERSION confirms the presence of a Ru"-NO' moiety. Photocatalytic Degradation of Trichloro- Reaction of (Ru(PPh,),Cp},(p-C,) with benzene using Immobilized Ti0, Films Tetracyanoethene: Macrocycle Formation by Containing Poly(tetrafluoroethy1ene) and Intermolecular CN Coordination Platinum Metal Catalyst M. I. BRUCE, 1. LOW, B. SKELTON and A. H. WHITE, r. w. H. UCHIDA, S. KATOH and M. WATANABE, Electrochim. New3 Chem., 1998,22, (5), 419-422 Acta, 1998, 43, (1P15), 2111-21 16 Reactions between (Ru(PPh,),Cp},(p-C4) and A new photocatalyst film is described which has Pt- C,(CN), add the cyanocarbon to one of the C-C loaded Ti0, and poly(tetrafluoroethy1ene) particles bonds forming the allylic complex Ru{q3- immobilised on an In-Sn oxide glass substrate. This C(CN)zC [CEC{ Ru(PP~&CP}]C=C(CN),} (PPh3)Cp gives rapid and complete degradation of trichloroben- (1). In solution, (1) is in equilibrium with its dimer zene in dilute aqueous solutions under illumination, (2). Structural studies of (2) show the presence of a with higher catalytic activity than Pt-TiO, or TiOJNi- ten-membered macrocyclic ring formed by displace- PTFE films. The decomposition rate was enhanced ment of the co-ordinated double bond in one mole- by the efficient consumption of photogenerated elec- cule of (1) by a CN group from a second molecule. trons and holes in the reduction of 0, and oxidative Enhancement of ~~l~~~l~~~~~d~~~i~degradation of trichlorobenzene, respectively. Hyperpolarizabilitiesin Ruthenium(I1) 4,4'- Large Enhancement in Photocurrent BipYridinim Complexes by N-PhenYlation Efficiency Caused by UV Illumination B. J. COE, J. A. HARRIS, L. J. HARRINGTON, J. c.JEFFERY, of the Dye-Sensitized Heterojunction L. H.REES, s. HOUBRECHTS and A. PERSOONS, Inorg. Ti02/RuLL%CS/CuSCN: Initiation and Chem., 1998,37, (13), 3391-3399 Potential Mechanisms Dipolar Ru(I1) tetra- or pentaammine complexes of B. O'REGAN and D. T. SCHWARTZ, Chem. Muter., 1998, N-substituted 4,4'-bipyridinium ligands show static 10, (9,1501-1509 first hyperpolarisabilities, Po, among the largest reported for transition metal complexes. The d6, 18- When subjected to low-power UV illumination for electron Ru(I1) centres function as powerful rr-elec- 10-30 min, the wide band-gap, dye-sensitised het- tron donors, and the nonlinear optical properties erojunctions, n-Ti0,lRu-dyelp-CuSCN (Ru-dye = are readily tuned by ligand changes. N-phenylation Ru polypyridyl dyes) undergo a dramatic increase in of 4,4'-bipyridinium ligands is shown as an effective efficiency. The W illurnination increases the incident means to increase Poin MLCT-based chromophores. photon-to-current efficiency for light absorbed by the dye by a factor of 5-1 0 and increases the open circuit voltage by 1OC-300 mV. This effect is stable for months ELECTROCHEMISTRY after the W illumination has ceased. Electrocatalytic Dehalogenation of Photocatalytic Activity of RuSz/SiO, for Water chloroaromatics on Palladium-Loaded Carbon Decomposition Felt Cathode in Aqueous Medium K. HARA, K. SAYAMA and H. ARAKAWA, Chem. Lett. Bn., A. I. TSYGANOK, I. YAMANAKA and K. OTSUKA, Chem. 1998, (9,387-388 Lett. Jpn., 1998, (4), 303-304 HI and 0, were produced from the photocatalytic The selective dechlorination of highly toxic chloroaro- decomposition of H20using a RuS, powder catalyst matic herbicides based on phenoxyacetic acid is (1) in the presence of sacrificial agents. The activity reported. This was achieved under mild conditions towards H, production was greatly improved by sup- in H20by electrocatalytic reduction using a Teflon porting (1) on SiO,, with a 1 wt.% RuS,/SiO, catalyst membrane-separated flow-through cell with a 5 wt.% giving 213 pmol of Hz after 46 hours. No 0, was PdC felt cathode and a Pt foil anode. After 4 hours, formed over a non-supported (l), but 0, was pro- all the compounds underwent > 90% conversion giv- duced over 1 wt.% RuS2/Si0, (121 pnol 0,after 25 ing 80-93% yield of C1-free phenoxyacetic acid. This hours) and 0.2 wt.% Pt/l wt.% RuS2/Si0, with the method is also applicable to other chloroaromatics. yields increasing with increasing irradiation time.

Platinum Metals Rev., 1998, 42, (4) 175 Fine-Tuning the Electronic Properties of ElectrochemiluminescenceOxalic Acid Sensor Binuclear Bis(terpyridyl)ruthenium(II) Having a Platinum Electrode Coated with Complexes Chitosan Modified with a Ruthenium (11) M. HISSLER, A. EL-GHAYOURY, A. HARRIMAN and Complex R. ZIESSEL,Angezo. Chem. Int. Ed., 1998, 37, (12), C:Z. ZHAO, N. EGASHIRA, Y. KURAUCHI and K. OHGA, 1717-1720 Electrochim. Acta, 1998, 43, (1&15), 2167-2173 Two Ru(terpy)-based binuclear chromophores with An electrochemiluminescence (ECL) sensor con- vastly improved photophysical properties are described taining a Pt electrode coated with a tris(2,2’-bipyri- in which the butadiynylene bridge is interspersed with dine)Ru(II)-modified chitosan responded to oxalic either a 1,4-phenylene or a 5,5’-(2,2‘-bipyridylene) acid (1) more strongly than to other substrates, includ- spacer. Further improvement in the photoproper- ing malkylamines. The ECL response to (1) was repro- ties was achieved by complexation of cations, such as ducible within 5% over 10 runs and the calibration Zn‘+, Cd” or BaZ+,to vacant co-ordination sites of the curve gave a straight line in the concentration range aromatic nucleus in the central unit, due to a better 0.1-10 mM with a detection limit of 3 x 10 M. blending of the respective LUMO levels. HETEROGENEOUS CATALYSIS APPARATUS AND TECHNIQUE Mechanistic Considerations for the Reduction Sulphur Dioxide Gas Detection by Reversible of NO, over PtlA1203and AI2O3Catalysts under q’-SO,-Pt Bond Formation as a Novel Lean-Burn Conditions Application for Periphery Functionalised R. BURCH, J. A. SULLIVAN and T. c. WATLING, Catal. Metallo-Dendrimers Today, 1998,42, (l-z), 13-23 M. ALBRECHT, R. A. GOSSAGE, A. L. SPEK and G. VAN The reduction of NOx under lean-burn conditions is KOTEN, Chem. Commun., 1998, (9), 1003-1004 compared over a series of catalysts and the reaction Multimetallic dendrimers, functionalised at their mechanisms are divided into 2 classes. In (l), NOx periphery with square planar Pt(I1) metal centres, reduction occurs on the Pt surface (such as C,H,-NO- reversibly absorb SO, to yield macromolecules with 0, over Pt/Al,O,), and is active at the lowest tem- significantly enhanced solubility. Drastic colour peratures and resistant to S poisoning. In (2), DeNOx changes from colourless to bright orange occur in the reactions OCCUT on ALO, with a weakly adsorbed reduc- presence of traces of SO2 as low as 10 mg dm-’, giv- tant (such as C,H,-NO-02 over Pt/Al,O, and A120,, ing highly active sensors for toxic SO, gas detection. and C,H,-N02-0, over Al,O,). They are strongly poi- soned by S and occur via formation of a surface nitrate Pd-Doped SnO, Thin Films Deposited by species on the ALO, which activates the reductant. Assisted Ultrasonic Spraying CVD for Gas Sensing: Selectivity and Effect of Annealing Pt/MCM-41 Catalyst for Selective Catalytic D. BRIAND, M. IABEAU,J. F. CURRIE and G. DELABOUGLISE, Reduction of Nitric Oxide with Hydrocarbons Sens. Actuators B: Chem., 1998, 48, (1-3), 395-402 in the Presence of Excess Oxygen Polycrystalline Pd-doped SnOl thin films (1) R. LONG and R. T. YANG, CUtal. Lett., 1998, 52, (1, 2), (0.25-1.75 pm) have been deposited on Si nitride 91-96 by spray pyrolysis at 460-540°C. The gas sensitivity 0.5-5 wt.% PtlMCM-41 (1) catalysts were used for of (1) was tested in air for CO (300 ppm), EtOH (100 the selective catalytic reduction of NO with CW, C& ppm) and CH, (1000 ppm). Those synthesised at C,H, and C,H, in the presence of excess 02.High 46&500”C are most sensitive to CO and, in the steady activity was seen with C2H, or C,H, as the reductant, state, sensitivities 5 4500 were obtained for the thinnest with a maximum NO reduction rate of 4.3 mmol g-’ films at 100°C. Cross-sensitivity to EtOH and CH, h-’ achieved with 1000 ppm NO, 1000 ppm C,H,, 2% was observed. Annealing under air at 500°C for 12 O2 and He as the balance. Little or no activity was hours stabilises the microstructure and gives a 2-10 observed with CH, or C,H,. (1) showed good stabil- fold increase in CO sensitivity. ity and H,O and SO2 did not cause deactivation. Effect of Plasticizer Viscosity on the Sensitivity Activity and Stability of Two Polymer- of an [Ru(bpy),2’(Ph4B-),] -Based Optical Supported Rhodium-Based Catalysts for the Oxygen Sensor Vapour Phase Carbonylation of Methanol A. MILLS and M. D. THOMAS, Analyst, 1998, 123, (5), N. DE BLASIO, E. TEMPESTI, A. KADDOURI, C. MAZZOCCHIA 1135-1 140 and D. J. COLE-HAMILTON, 3. Card., 1998, 176, (I), The quenching of the electronically-excited, 2 5 3-2 5 9 lumophoric state of [Ru(bpy),Z’(Ph,B-),] by 0, was Rh catalysts supported on a diphenylphosphinated studied in various neat plasticisers. The compatibil- copolymer of styrene and divinylbenzene (SDT) or ity of the polymer-plasticiser combination is the dom- polyvinylpyrrolidone (PVP) were tested for the car- inant factor in determining the O2sensitivity. For bonylation of MeOH at 80 bar and 180-190°C. highly compatible combinations, such as TPP-PMMA, WPVP catalysts showed excellent activity and selec- the plasticiser with the lowest viscosity, TPP, produces tivity, as well as very high stability, with no Rh leach- films of the highest O2sensitivity. ing during 50 h testing, unlike WSDT catalysts.

Platinum Metals Rev., 1998, 42, (4) 176 Hydroformylation of I-Octene under Palladium-Catalyzed Cross-Coupling Atmospheric Pressure Catalyzed by Rhodium Reactions in Supercritical Carbon Dioxide Carbonyl Thiolate Complexes Tethered to D. K. MORITA, D. R. PESIRI, s. A. DAVID, w. H. GLAZE and Silica W.TUMAS, Chem. Commun., 1998, (13), 1397-1398 H. GAO and R. J. ANGELICI, Organometallics, 1998, 17, The C-C bond coupling Heck and Stille reactions are (14), 3063-3069 reported in supercritical C02(scC0,) with various The SO,-tethered Rh thiolate complex catalysts phosphines giving rates and selectivities comparable Rh-SISiO, and Rh-S-P/SiO, were prepared by the con- to those in toluene. Fluorinated phosphines, in par- densation of SiO, with Rh,[pS(CH2),Si(OCH,),],- ticular tris [3,5-bis(trifluoromethy)phenyl] phosphine (CO), or R~,[C~-S(CH,),S~(OCH,),],[Ph2P(CH,),- (l), give high conversions (> 99%) as they enhance Si(OC,H,),],(CO),. These catalysts were highly active the solubility of metal complexes in scC0,. for the hydroformylation of 1-octene in the presence of phosphine donor ligands at 60°C and 1 atm. The A Highly Active Palladium Catalyst System high activity resulted from the stabilisation of for the Arylation of Anilines Rh(SR)(CO),(PR3) species on the catalyst surfaces. J. P. SADIGHI, M. c. HARRIS and s. L. BUCHWALD, Tetrahedron Lett., 1998,39, (30), 5327-5330 Effect of Support on the Conversion of A 0.5 mol% Pd(OAc),/DPEphos system, where Methane to Synthesis Gas over Supported DPEphos is bis [2-(diphenylphosphmo)phenyl] ether, Iridium Catalysts was a highly active catalyst for the arylation of pri- K. NAKAGAWA, K. ANZAI, N. MATSUI, N. IKENAGA, mary anilines by aryl bromides giving products in 5 T. SUZUKI, Y. TENG, T. KOBAYASHI and M. HARUTA, Cad. 99% yield. This system is effective for electron-poor Lett., 1998, 51, (3, 4), 163-167 anilines and electron-rich aryl bromides. The production of synthesis gas from CH, (1) via par- Palladium-CatalyzedCarbon-Nitrogen Bond tial oxidation was studied using Ir catalysts supported on various metal oxides. The reaction proceeded via Formation: A Novel, Catalytic Approach a two-step process consisting of combustion of (1) to Towards N-Arylated Sulfoximines give H,O and CO, followed by the reforming of (1) C. BOLM and J. P. HILDEBRAND, Tetrahedron Lett., 1998, from CO, and steam. The combustion and reform- 39, (32), 573 1-5734 ing of (1) from steam was not dependent on the cat- Pd(OAc),, in the presence of chelating bisphosphines, alyst support, but reforming of (1) from CO, with Ir catalyses the coupling of sulfoximines with aryl bro- was highly dependent on the support in the order: mides (l), giving N-arylated products. High yields (I TiO,> ZrO, 2 Y,O, > LazO,> MgO 2 AlzO, 5 SiO,. 96%) were obtained with (1) containing electron- withdrawing groups in the ortho- or para-positions. HOMOGENEOUS CATALYSIS Rhodium Cationic Complexes Using Asymmetric Direct a,p-Functionalization of Dithioethers as Chiral Ligands. Application Allenes via Asymmetric Carbopalladation in Styrene Hydroformylation K. HIRoI, F. KATO and A. YAMAGATA, Chem. Lett. Jpn., A. OREJON, A. M. MASDEU-BULTO, R. ECHARRI, M. 1998, (3,397-398 D&GUU, J. FO&S-ChER, C. CIAVER and C. J. CARDIN, The asymmemc direct a$-functionalisation of allenes J. Organomet. Chem., 1998,559, (1-2), 23-29 with chiral phosphine ligands in the presence of The dithioethers (-)-DIOSR, (R = Me, 'Pr) (2,3-0- Pd(dba), in various solvenrs is described. The reac- isopropylidene-1,4-dimethyl (and diisopropyl) tion of racemic allenes with iodobenzene and a nucle- thioether-L-threitol) react with [Rh(COD),] Clop ophile (malonate carbanion) using chiral phosphines (COD = 1,5-cyclooctadiene) in CH,Cl, to give occurred with extremely high enantioselectivity. [Rh(COD)(DIOSR2)]C10,. These were active cata- However, a similar reaction of the chiral allene using lyst precursors for styrene hydroformylation, giving an achiral phosphme ligand proceeded with complete conversions of 2 99% at 30 atm and 65"C,with regio- enantiospecificity, selectivity in 2-phenylpropanal as high as 74%. Heterocycles via Pd Catalysed Molecular Transition Metal Catalysis in Fluorous Media: Queuing Processes. Relay Switches and the Application of a New Immobilization Principle Maximisation of Molecular Complexity to Rhodium-Catalyzed Hydrogenation of R. GRIGG and v. SRIDHARAN, Pure Appl. Chem., 1998, Alkenes 70, (5), 1047-1057 D. RUTHERFORD, 1. I. J. JULIETTE, C. ROCABOY, Pd(0) catalysts facilitate the orderly assembly of com- I. T. HORVATH and J. A. GLADYSZ, Catal. Today, 1998, plex heterocycles and carbocycles containing 3-7 42, (4), 381-388 membered rings from diverse building blocks (allenes, Biphase systems comprise toluene solutions of vari- CO, alkenes, etc.) by polymolecular queuing. Certain ous alkenes and CF,C,F,, solutions (1) of the pre-cat- compounds are identified as relay switches because alyst, CIRh[P(CH2CH2(CF,)rCF,)3]3(1.1-0.8 mol%) they extend the relay phase of the cyclisation-anion (1). After 8-26 hours under 1 atm of H, at 45"C, capture cascade while the Pd catalysed cascades switch hydrogenation products were extracted in 98-87% between inter- and intra-molecular processes. yields from (l),which could be reused.

Platinum Metals Rev.,1998, 42, (4) 177 New Catalysts and Methods for Highly Selective Aerobic Oxidation of Primary Enantioselective Metal Carbene Reactions Alcohols Catalyzed by a Rh(PPh3)3C12/ M. P. DOYLE, Pure Appl. Chem., 1998, 70, (5), Hydroquinone System 1123-1 128 A. HANYU, E. TAKEZAWA, s. SAKAGUCHI and Y. ISHII, Chiral diRh(I1) carboxamidate catalysts, with bridg- Tetrahedron Lett., 1998, 39, (31), 5557-5560 ing chiral pyrrolidone, oxazolidinone, azedinone or The selective aerobic oxidation of primary alcohols imidazolidinone ligands, are effective for highly enan- to aldehydes, even in the presence of secondary alco- tio-, diastereo- and regioselective syntheses of lac- hols, was catalysed by a Ru(PPh,) ,Cl,/hydroquinone tones and lactams by cyclopropanation, cycloprope- system under atmospheric 0,at 60°C. Aliphatic and nation, C-H insertion, and ylide derived reactions cyclic primary alcohols gave aldehydes in good yields, of diazoacetates and diazoacetamides. Reactions occur while allylic alcohols gave unsaturated aldehydes in with high turnover numbers and give products in high high yields without intramolecular H transfer. yield with enantiomeric excesses 2 90%. Homogeneous Catalysis. Use of a Rhodium Complex-Catalysed Allylic Rnthenium(I1) Complex for Catalysing the Alkylation of Allylic Acetates ene Reaction R. TAKEUCHI and N. KITAMURA, New J. Chem., 1998, w. w. ELLIS, w. ODENKIRK and B. BOSNICH, Chem. 22, (7), 659-660 Commun., 1998, (12), 1311-1312 [Rh(COD)Cl],-P(OPh), (P:Rh = 2-3) is an efficient The complex rrans-[Ru(salen)(NO)(H,O)]' (1) catal- catalyst for the allylic alkylation of allylic acetates yses the ene reaction between activated enophiles and giving products in < 90% yield. Alkylation at the more olefins to give homoallylic alcohols by a stepwise substituted allylic terminus is predominant. process. Using 1 mol% of (l), (+)-citronella1 was converted 10 I-isopulegol after 6 h in 80% yield. It may and Mechanism Of be possible to use chiral analogues of this catalyst Catal~sedOxidation of Formaldehyde by for asymmetric catalytic intramolecular ene reactions. Cerium(1V).. in Aqueous Sulfuric Acid Media D. KAR, s. K. MONDAL, M. DAS and A. K. DAS, 3. Chem. FUEL CELLS Res. (S), 1998, (7), 394-395 Studies of the kinetics and mechanism of the Ir(II1) Carbon Supported and Unsupported Pt-Ru (-1 0-6mol dm-')catalysed oxidation of formaldehyde Anodes for Liquid Feed Direct Methanol Fuel to formic acid by Ce(IV) were performed in aque- Cells ous H,SO,. An intermediate, involving an association L. LIU, c.PU, R. VISWANAI'HAN, Q. FAN, R. LIU and E. s. of the catalyst, substrate and oxidant, was formed SMUI'KIN, Elecmchinz. Acta, 1998,43, (24), 3657-3663 prior to the electronic transfer step and the Ir(III)/Ir(IV) catalytic cycle. The performance of supported (1) (< 0.8 mg cm-l, Pt-Ru (l:l)/C) and unsupported (2) (Pt-Ru (1:l)) Cationic Ruthenium Allenylidene Complexes catalysts was compared in DMFCs having a reversible as a New Class of Performing Catalysts for H reference electrode. The measured specific activi- Ring Closing Metathesis ties of (1) were 3 times higher than (2) but membrane electrode assemblies made with (1) showed no A. FURSTNER, M. PICQUET, c. BRUNEAU and P. H. improvement with loadings > 0.5 mg cd.Fuel cells DIX~TEUF,Chem. Commun., 1998, (12), 1315-1316 with 0.46 mg cm-' supported electrodes performed The cationic 18-electron allenylidene Ru complexes as well as unsupported electrodes with 2 mg cm-'. [Ru=C=C=CR,Q(CI)(arene)]PF, (L = PCy,, PPt,), were found to be excellent catalyst precursors for ring closing olefm metathesis. Particularly important are ELECTRICAL AND ELECTRONIC the smooth cyclisations ofthe conformationally flex- ENGINEERING ible dienes to 16- and 18-membered cycloalkenes. Electrical and Structural Properties and Phase Catalysis in Aqueous Solution: Hydrogenation Diagram of a Molecular Superconductor of Benzene Derivatives Catalysed by (@- P-[(CH&N] [Pd(dmit),I2 CJh)2R~2Clr A. KOBAYASHI, A. MIYAMOTO, R. KATO, A. SATO and E. G. FIDALGO, L. PLASSERAUDand G. SUSS- FINK,^ Mol. H. KOBAYASHI, Bull. Chem. SOC.Jpn., 1998, 71, (5), Catal. A: Chem, 1998, 132, (l), 5-12 997-1006 The catalyst precursor (q"-C,H,),Ru2Cl, was used for P-[(CH,),N] [Pd(dmit),], (1) is isomorphic to the hydrogenation of benzene and various alkyl-ben- [(CHJ,N] mi(dmit)2],which is the first pure n accep- zene derivatives. Under biphasic conditions, cyclo- tor molecular conductor exhibiting a superconduct- hexane derivatives were obtained with turnover rates ing transition. The phase diagram of (1) resembles of 20-2000 cycles per hour. The less active species, that of typical organic superconductors. The super- [(qo-CbH,),Ru,H,]" and [(rl~'-C,H,),Ru,H,]'+, were conducting phase appeared at 69kbar. (1) has a char- found in the reaction mixture after the catalytic runs. acteristic "pre-superconducting region" at - 5.5 kbar, A more active intermediate, [Ru,(~~'-C,H~)~(CI~-CI)~~,-where resistivity decreases very rapidly with lowering O)(pm-H),]' was also detected. temperature. The highest Tc was 6.5 K.

Platinum Metals Rev., 1998, 42, (4) 178 NEW PATENTS ELECTROCHEMISTRY APPARATUS AND TECHNIQUE Insoluble Anode Electric Connection for Oxygen Detection TOBATA SEISAKUSHO K.K. Japanese Appl. 10172,690 ROBERT BOSCH G.m.b.H. European Appl. 831,565A An insoluble anode has an electrode substrate with at A high melting point electrically conductive connec- least one of Ti, Ta, Nb, Zr, and an electrode active tion for I.C.E. lambda probes, used for detecting layer of Pt group metal, such as Ru, Rh, Pd, Os, Ir or the O2content in exhaust gas, connects a contact point Pt, supported on the electrode substrate through a with a contact member. These are separated by a dif- diffusion layer. The anode is used in electrolytic sur- fusion active layer of a Pd-Ni alloy, 2-20 pm thick. face treatment, including electroplating. The anode The contact member is heated to a welding temper- displays superior durability at high current densities ature at the contact point. The contacts have high and during electrolysis. temperature and mechanical stability with relatively large surface area electric contact. ELECTRODEPOSITION AND Electrode for Detection of Nitric Oxide SURFACE COATINGS UNN. DUKE World Appl. 98114,639A Activation Bath An electrode for detecting NO, especially in biological samples, has a surface, preferably comprising Ru METAL ARTS CO. INC. US. Patent 5,753,304 and/or Ru oxide, which forms a complex, preferably An activation bath comprises 0.1-2 g of a Pd salt, a nitrosyl complex, with NO. A specific electrode is 20-250 g of an alkali metal fluoride or hydrofluoric formed by conditioning such an electrode in saline at acid, 0.05-0.5 1 of carboxylic acid as a complexing +675 mV for 2 hours. The electrode has a sensitiv- agent, 1-3 g of an alkali metal salt of gluconic acid, ity for NO in the nM range, a response time of a few 1-5 g of an Fe salt, 10-30 g of a Ni salt and suffi- seconds, and is stable in biological fluids and tissue. cient deionised HzOto make 1 gallon. The bath is used for the electroless plating of Ni onto Al-containing Exhaust Gas Sensor substrates, such as automobile wheels and computer GENERAL MOTORS cow. US. Patent 5,733,504 discs. The process is efficient and requires fewer steps. An exhaust gas sensor for I.C.E. comprises inner and Oxidation Resistant Coatings outer electrodes separated by a solid, porous electrolyte. A porous protective coating which covers GENERAL ELECTRIC CO. US. Patent 5,759,380 the outer electrode is coated with a microporous com- A protective CrRuAl-based coating is formed on a posite layer made of 80-99.998 wt.% ceramic and the shaped substrate by electrodeposition of Ru and Cr, remaining 0.002-20 wt.% is a catalyst material selected followed by aluminising by heating in a powder pack from Pt, Pd, Rh or other transition metals. This layer to form the final coating. The Cr is 55-70 vol.% of is 10-500 pm thick to reduce H, induced lean shift. the Cr and Ru layers. The coating may be formed on internal surfaces, especially on Nb-based substrates Nitrogen Dioxide Sensor in jet engine components. SHIMADZU COW. Japanese Appl. 10190,22 1 Glossy Palladium Plating Bath A controlled potential electrolysis type NO, sensor has a metal layer and a Pt layer formed on a gas per- OKUNO PHARM. m.K.K. Japanese Appl. 9/235,69 1 meable diaphragm, which is in the contact surface A plating bath contains 1-40 g 1 ' of Pd, 0.04-6 mol of an electrolyte and a tested gas. A counter electrode 1 ' of an NH, compound and aromatic sulfonamide and a reference pole are formed on a detection pole or sulfobenzoic acid imides. The pH of the HZO- on the diaphragm. The concentration of NO2detected soluble Pd salt mixture is > 10. The plating is per- is based on the current between the counter electrode formed at 20-50°C with a current density of 0.1-10 and the detection pole. A dm'. The plating has superior corrosion resistance, antiwear and electrical properties. It is used for electric contact points and connector circuit substrates. HETEROGENEOUS CATALYSIS Thin Platinum Films Palladium Composite Catalyst TONG YANG CEMENT cow.Japanese Appl. 10184,086 AKIN AW CO. LTD. European Appl. 826,419A A thin Pt film is formed on a substrate used in elec- A composite ZnO-Pd catalyst is prepared by dispersing tronic components by depositing Pt on an insulated and fixing Pd on the surface of a ZnO (1) substrate, oxide layer on a substrate under an oxidising amos- by adsorption of Pd" ions from an acid solution, phere, followed by heating to form an 02-freePt layer followed by reduction of the adsorbed Pd ions to metal- with a specified orientation, preferably (200). This lic Pd. Active C fibres and/or TiO, are additionally method forms pure Pt thin films positively oriented integrated in, and deposited on, the surface of (1). in the polarisation direction. The electronic compo- The catalyst is used in the elimination of hazardous nent has greatly enhanced performance and an components, such as CO and NOx, from automobile improved fatigue effect. exhaust gases.

Platinum Metals Rev., 1998, 42, (4), 179-182 179 Solid Bed Catalyst Catalytic Reforming of Hydrocarbons BASF A.G. European Appl. 841,090A UOP US.Patent 5,755,956 Solid bed catalysts containing either Pd and Se and/or Reforming a gasoline-range hydrocarbon feedstock Te on a SiO, carrier have a BET surface area of 80-380 to an aromatics-rich effluent stream, involves con- m* g-’, a pore volume of 0.6-0.95 cm’ g-’ and a pore tacting it with a catalyst comprising a multigradient diameter of 3 nm-300 pm. They are used as iso- noble metal of Pt and surface-layer Ru, a non-acidic merisation catalysts, especially for 3-buten-1-01 com- large-pore molecular sieve, and an inorganic oxide pounds. The process gives fewer hydrogenation reac- binder. The process has increased selectivity for the tion by-products or low boiling point compounds. conversion of paraffins to aromatics and improved catalyst stability, particularly in the presence of S. Diesel Engine Catalyst CATALER IND. CO. LTD. European Appl. 842,692A Hydrogenation Catalyst A catalyst for punfylng diesel engine exhaust gas com- MITSUBISHI CHEM. COW. Japanese Appl. 10171,332 prises SiO, and Al,O, supports in a mixing weight A hydrogenation catalyst comprises a C support and ratio of 98:2-72:28, and 0.01-0.55 g Pd per litre of Ru, Sn and optionally another Group VIII metal, uni- support. The catalyst can oxidise SO, in the exhaust formly distributed inside the support. The catalyst gas at higher temperatures, so it can effectively inhibit is used for the catalytic hydrogenation of carboxylic the formation of sulfates, as well as simultaneously acids giving high yields of 1,4-butanediol andlor control the emission of particulates. tetrahydrofuran, from maleic anhydride, maleic acid, etc., under relatively mild conditions. Purification of Exhaust Gases INST. FRANCAIS DU PETROLE Diesel Engine Catalyst European Appl. 842,693A HINO MOTORS LTD. Japanese Appl. 10176,159 A process for the low temperature purification of A purification catalyst has a fine particle-like carrier exhaust gases from I.C.E. comprises the incorpora- comprising Rh, Pt, Ir, Pd, Au, Ag or Ru, with a grain tion of a Pd-based catalyst or an absorbent up-stream size of 0.1-50 pm; a metallic oxide fine particle, such of the conventional three-way catalyst to eliminate as A1203,Ti02 or SiO,; and an inorganic binder, such alkynes, particularly acetylene, at 220-250°C. The as sols of SiO, or A1,0,, etc. The rate of NOx reduc- system eliminates hydrocarbon pollution from cold tion of exhaust gas from a diesel engine is improved. start either by hydrogenation or absorption of the acetylene using the Pd-based compound. The process Diesel Exhaust Purification Catalyst should meet the envisaged EC legislation for levels of NISSAN MOTOR CO. LTD. Japanese Appls. 10176,162-3 CO, HCs and NOx in the years 2000 and 2005. A catalyst for exhaust gas purification for diesel and lean burn engines, has a catalyst layer chosen from Nitrogen Oxide Trap for I.C.E. Rh, Pd and Pt, and a ceramic component selected FORD GLOBAL TECHNOLOGIES INC. from Si carbide, Si nitride and B nitride along with European Appl. 845,289A at least one rare earth element selected from lan- A NOx trap for I.C.E. exhaust gases comprises a thanum, neodymium, etc. The catalyst shows high porous support loaded with (in wt.%): 6-15 Sr oxide; temperature durability and excellent purification 0.5-5 Pt, Pd and/or Rh; 3.5-15 Zr and 15-30 sulfate. capacity for hydrocarbons, CO and NOx. It traps NOx during lean burn operation and releases absorbed NOx when the O2concentration falls; the Exhaust Gas Purification from I.C.E. desorbed NOx is converted to N, and 02. TOYOTA CHUO KENKYUSHO K.K. Japanese Appl. 10/85,600 Noble Metal Support A catalyst, for the oxidation and purification of hydro- ASAHI KASEI KOGYO K.K. World Appl. 98126,867A carbons contained in exhaust gas from I.C.E. com- A noble metal support comprises a Pd-free layer inside prises Zr oxide particles and a catalytic noble metal, the support, and a layer where Pd is supported in a with 2 50% of the latter being in a high oxidation state. region > 100 pm deep from the outer surface of the Pt carrying hydroxide, obtained by adding Pt to Zr support. It has high activity and resistance to wear hydroxide, is also included. The purification capac- and is useful as a catalyst for oxidation, reduction and ity of SOF in a low temperature region is good and hydrogenation, esterification of acrolein and/or metha- the oxidation of SO2and the formation of sulfates is crolein, or as a catalytic converter for car exhausts. suppressed. Preparation of High Octane Paraffin Removal of NOx TEXACO INC. US. Patent 5,744,667 KYOCERA COW. Japanese Appl. 10185,602 A high octane paraffin for use as a blending compo- An oxide catalyst material for removal of NOx from nent in gasoline is prepared by reacting a 5-10 C exhaust gas contains 0.5-20 wt.% Pd oxide and oxides acceptor olefin and a 3-1 0 C donor parafin (l), with of Ga and Ni. The NOx contained in the exhaust gas different backbone structures, in the presence of a Pt is directly decomposed into N, and O2without the catalyst supported on a Li neutralised large pore B p- use of a reducer. The catalyst is used for the removal zeolite. The catalyst contains 0.1-2 wt.% Pt and of NOx from exhaust gas from factories, power 0.05-2 wt.% B, to dehydrogenate a portion of (1). stations and motor vehicles.

Platinum Metals Rev., 1998, 42, (4) 180 Purification of Exhaust Gas Hydrosilation of Unsaturated Compounds DENKI KAGAKU KOGYO K.K.Japanese Appl. 10185,604 DOW CORNING CORP. US. Patent 5,756,795 A catalyst, for purifymg exhaust gas from I.C.E., com- The hydrosilation of unsaturated organic and Si comprises a catalyst component containing Si nitride pounds, such as Si hydrides, in the presence of a Pt andlor B nitride, Si carbide, Rh and Pt and/or Pd. compound or Pt complex catalyst, and a specific accel- The Si nitride andor B nitride are in the Pt- andor erator, such as 1,7-octadiyne or maleic anhydride, is Pd-containing layer while the Si carbide is in the described. The acceleratorsimprove yields in the pres- Rh-containing layer. The catalyst improves exhaust ence or absence of 0,and are very effective in the gas purification. Catalytic activity and endurance hydrosilation of internal unsaturated bonds. under a stoichiometricenvironment are also improved. Platinum Complex Catalysts Hydrogenation of Aromatic Amines RHONE-POULENC CHIM. French Appl. 2,750,349 BAYER A.G. German Appl. 1196141,688 Pt complexes with various olefin ligands are claimed A catalyst for the hydrogenation of aromatic amines for use as homogeneous and thermo-activatable cat- to cycloaliphatic amines comprises an alkalised sup- alysts in hydrosilylation reactions between silanes or port impregnated with 0.05-10 wt.% Ru and Pd in siloxanes, and compounds with reactive unsaturated a weight ratio of Ru:Pd of (1:30)-(30:1), and con- aliphatic andor polar functional groups. The catalyst tains no halogen. Aromatic amines can be completely is stable at 3040°C for long periods. The Si oil prod- converted even at high catalyst loadings, with a high uct is used for anti-adhesive coatings on fibres, tak- selectivity for primary cycloaliphatic amines, without ing dental impressions, adhesives, etc. addition of NH, and with no hydrogenolysis or methanation. Selective Chlorine Component Removal GES BESEITIGUNG VON UMWELTSCHAEDEN Hydrogen Peroxide Production German Appl. 2/97122,331 BASF A.G. German Appl. 1196142,770 A catalyst for the selective hydrogenative removal of The production of H,02 solutions containing 2 2.5 fluorochlorohydrocarbons and halones from gases wt.% H20,involves continuously reacting H2and comprises a carrier with a fixed active component of 0,on catalysts containing Pd as an active component. Os.Ru&Y, (where X = Group VIII metal; Y = Group The reaction takes place in H20or 1-3 C alkanol 111 or IV metal or rare earth metal; and a, b, c and d on moulded catalyst bodies. The catalysts used have = 0-100, with a + b # 0). The catalyst is used for a long service life. the removal of ozone-damaging C1-containing components, such as FCHCs from gases evolved in FHC production. The catalyst has higher activity and longer HOMOGENEOUS CATALYSIS life than the PdAlF, previously reported. Aromatic Haloamino Compounds NOVARTIS A.G. European Appl. 842,920A FUEL CELLS A catalyst is comprised of a Rh, Ru, Ir, Pt or Pd catalyst modified with an inorganic or organic P com- Platinum Electrocatalyst for Fuel Cells pound with an oxidation state e 5, and a V compound. NE CHEMCAT CORP. European Appl. 827,225A The catalyst is used in the preparation of aromatic An electrocatalyst (1) comprises a skeleton alloy of Pt haloamino compounds by hydrogenation of the cor- with Ga, V, Cr, Mn, Fe, Co, Ni or Cu. Also claimed responding halonitro compounds. Haloaminos are is an electrode and its production comprising the elec- intermediates in the production of dyestuffs and pes- trocatalyst and a H,O repellent binder, bound to a ticides. The reaction gives very high selectivity with conductive and gas permeable support substrate. (1) few side products, high yields and short reaction times, is a cathode for proton exchange membrane or phos- at low pressures (5 bar) and temperatures (100%). phoric acid type fuel cells and may also be a gas button cell diffusion electrode, etc. It has high activity Supported Phase Chiral Catalyst and long term stability for 0, reduction compared CALIFORNIA INST. OF TECHNOLOGY to conventional electrocatalysts. US. Patent 5,736,480 A supported phase catalyst, with a metal selected from Catalyst for Use in Fuel Cells Rh, Ru, Ir, Pd, Pt, V, Pb, Sn and Ni, comprises an JOHNSON MATTHEY PLC European Appl. 838,872A organometallic compound of chiral2,2'-bis(diphenyl A catalyst, for use in gas diffusion electrodes for fuel phosphino)-1,1 '-binaphthyl (BINAP) solubilised in cells, particularly PEMFCs, comprises a Pt-M alloy a solvent having two alcohol groups. Each phenyl in intimate contact with Y, where M is one or more group is at least monosulfonated. Also claimed is transition metal, Group IIIA or Group IVA metal, the use of the above catalyst in the asymmetric hydro- and Y is a bronze-forming element or oxide (M is not genation of 2-arylacrylic acids, especially dehydrona- Ru ifY is WO,; M is optionally two or more metals proxen. The catalyst system is soluble in highly polar where one metal is Ru). A catalyst comprising Pt- solvents but not in non-polar solvents so the catalyst Ru alloy alloyed with W is also claimed. The cata- may be solvated on a solid catalyst support, facilitat- lyst is tolerant of poisons and can be used as the ing easy separation from the product after synthesis. electrocatalyst on the anode and the cathode.

Platinum Metals Rev., 1998, 42, (3) 181 Electrocatalyst Particles Electrically Conducting Body UNIV. MASSACHUSETTS US. Patent 5,702,836 FURUKAWA ELECTRIC CO. LTD. Particles for a fuel cell electrocatalyst for oxidising Japanese Appl. 10184,065 alcohols comprise an Fe oxide core with an outer Pt The body comprises an electrically conductive base oxide shell. The electrocatalyst is colloidal, lightweight carrying a Ni or Ni alloy foundation layer on its sur- and cheaper to manufacture due to the non-Pt core. face. Upon this is an interface layer of Pd or Pd alloy, 0.005-0.1 pm thick, carrying a monoatomic layer of Anode Catalyst for Fuel Battery Au or Au alloy. The member has excellent soldering TOSHIBA K.K. Japanese Appl. 10174,523 properties and oxidation of the interface layer is pre- A catalyst for a fuel battery has Pt or fine Pt alloy par- vented. It is used in diodes, transistors, etc. ticles for H, storage distributed on the surface of a conductive C powder carrier. A highly active anode TEMPERATURE MEASUREMENT is obtained and battery durability is improved. Temperature Sensor Hydrogen Fuel Cell Accumulator HONEYWELL MC. US. Patent 5,726,624 R. WOLLHERR German Appl. 1196144,864 A tubular temperature sensor for use in ovens at - A hydrogen fuel cell accumulator, for use in electric lOOO"F, has conductive strips of Pt-Ag alloy deposited vehicles, comprises a polymer electrolyte membrane on a rigid Al oxide substrate, with insulating glass lay- cell with a Ru catalyst, an air filter, a metal hydride ers over and between the conductive strips. A resis- storage unit, a small compressor and a thermoelec- tive temperature detector (RTD) is placed on one end tric heat exchanger. The H, from the hydride storage region of the substrate and attached electrically to the unit is converted electrochemically with O2from the conductive strips. Fibreglass sleeved wires are not air. The air is cleansed by passing through a filter. The needed and electrical connections can be made to the accumulator is economical to produce. RTD in parts where the sensor is at high temperatures. ELECTRICAL AND ELECTRONIC MEDICAL USES ENGINEERING Crosslinkable Silicone Dental Compound Glass Circuit Substrate ZHERMACK S.P.A. European Appl. 822,233A CANON K.K. European Appl. 838,980A A crosslinkable Si compound for use in dentistry com- A glass circuit substrate comprises a layer of Pd nuclei prises a crosslinkable Si polymer, a crosslinking agent, carrying a Pd-P plating layer. Also claimed is the pro- a Pt catalyst and a Na-A1 zeolite. The composition duction of a semiconductor device, by fabricating the remains stable under storage conditions, even at tem- above substrate, patterning the plating layers to define peratures higher than those normally recommended. wiring and electrodes, and bonding IC chips to the The Pt catalyst is protected by the zeolite against electrodes. A wiring pattern can be formed by wet the action of potential contaminants. plating, without degrading the smoothness of the glass surface or the adhesion against external thermal effects. Precious Metal Dental Alloy Adhesion to the substrate is enhanced, thus resistance BEG0 BREMER GOLDSCHLAEGEREI to peeling is improved. German Appl. 1197119,677 A precious metal dental alloy contains Au, Ag, Pt, Pd Magnetic Recording Medium and Mn, with the Ag, and preferably the Mn, content SHOWA DENKO K.K. US. Patent 5,731,070 higher than the Pt content. The alloy is free from Cu, A magnetic recording medium comprises a Si layer Sn, In, Mg and Ca. The use of the above Cu-free pre- on a non-magnetic substrate and a layer comprising cious metal alloy is claimed as material for false teeth, at least one Pt group metal or alloy, or C, with the bridges, crowns, etc., which may be covered with Pt being partly silicified and the C being partly amor- ceramic and supported by implants, etc. The alloy phous, both due to Si diffusion. An undercoat is has high hardness (250 HV5) and strength, resists formed over the Pt/C layer, followed by a magnetic corrosion and tarnishing, and is free from toxic Cu. layer and a protective overcoat. The medium, used for magnetic recording disks, has a high coercive force Dental Palladium-Based Alloy and squareness ratio which increases the magnetic SUPERMETALL RES. PRODN. COMPLEX recording density. Russian Patent 2,092,603 palladium-containing hi^ ~~~di~~An alloy for use in dentistry contains in wt.%: 45-70 wire Pd, 10-25 Au, 10-15 Cu and 10-15 Sn, at a Cu:Sn STEEL Japanese Appl. 10183,71 ratio of 1: 1. The allov is non-toxic. strong. has good _I .2 A thin Au alloy wire for bonding the electrode of a flowability for casting complex dental prostheses, and semiconductor device and an external lead includes good adhesion to a wide range of ceramic coatings. 0.005-1 wt.% Pd and 0.005-0.3 wt.% Mn, the remainder being impure Au. The wire improves corrosion resistance, ensures long-term reliability, improves The New Patents abstracts have been prepared from junction properties and allows high density mounting. material published by Derwent Information Limited.

Platinum Metals Rev., 1998, 42, (4) 182 NAME INDEX TO VOLUME 42 Page Page Page Page Abarra, E. N. 123 Berzias,A. R I24 then, W. 82 Denisovich, L. I. 35 Abe., K. 83 Bianchi, D. 38 Chen, Y.-w. 126 Deronzier,A. 60, 163 Abid, Z. 34 Bhchini,C. 35, 145 Chen, z. 36 Maz, V. 38 AchiiY. 174 BhqM. C. 34 Chmg, C.-H. 81 Maz&da,M.E. 80 Ahlafi, H. 38 Bockholt, A. 37 Cheung,K.-K. 123, 124 DiCguez, M. 177 Ahmed, G. 127 Bogdanovic, s. 39 Cheung, T.4. 124 Dixneuf, P. H. 159, 178 Aissi, F. 37 Bolm, c. 177 Chiba, A. 68 Donnerstag, A. 56 Aizel, G. I27 Bon, M. 81 Chickos, J. S. 128 Doyle, M.P. 178 Ajjoy A. N. 127 Bond, A. M. 36 chiffey,A. F. 25, 160 Driver, R 55 ALashiM. 125 B6m- H. 78 (30,H.-J. 83, 124 -is, D. L. 79 Alam,M.R 39 Borges, S. D.S. S. I75 Ch04 S.-H. 37 I)lmn,B. 83 Albrecht, F. 57 Bosnich, B. 178 Chong, E. K. 55 Dyer, S. E. 125 Albrecht, M. 176 Braddock-Wilhng, J. 128 christofides,C. 36, 125 Dyson, P. J. 135, 145 Al-4 E. I. 38 Bradley, J. S. 161 C!h.auow&i,W. 128 Allen, F. M. 126. Briise, S. 126 Chuang, K T. 81 %itmi, K 38,82 AW,H. 127 Bnssan, M. 145 Chuman, T. 10 Echani, R 177 Anderson, N. L. 55 Breuer, K. 39 chun& c. w. 80 Eckert, M. 39 Angelici, R J. 177 Briand, D. 176 churchill, D. G. 127 Egashira, N. 176 Angell,C.H. 27,46, i16 Briscoe, H. V. A. 169 Churchill, M.R 127 Egaw4 T. 128 Antonid, M. 38 Britz, P. 78 claver, c. 177 Eicher, S. 34 Antonmi P. L. 34 Bronger, W. 78 Clegg, w. 100 El GMi,A. 37 Antonmi v. 34 Brook, T. E. 37 cobdQ1,P. D. 141 Elding, L. I. 174 AnzaiK. 177 Brown, D. A. 78 Cockcroft, J. 169 El-Glmyoury, A. 176 Aonuma, S. 78 Brown, J. M. 159 Coe,B. J. 175 Elliott, J. M. 36 M. 128 Brown, S. N. 34 Col+Hamilton, D. J. 176 Ellis, D. J. 135 Arakawa, H. I75 Bmce, M.I. 174, 175 Coleman,N.RB. 36 Ellis, W. W. 178 -K. 125 Brick, R 56 Connolly, J. 174 Emori, M. 128 AKlR P. 38 Bnmeay C. 178 Cook, J. D. 125 Enders. D. 39 Aricd, A. S. 34 Bmer, H. I24 comilp,B. 145 EnglematZR 174 Artemenko,Yu.A. 99 Buchwald, S. L. I77 Conon. J. B. 27,46,116 Eremenlro, I. L. 83, 123 Asahw,K. 38 Bulgakov, R G. 35 Curie, J. F. 176 Eremenko, L. T. 83 Ashton, S. V. 24,98, Bmh, R I76 WWA. 69 Ertz G. 24 134, 163 Burkov, A. 78 Estcruelas, M.A. 82 Asomom, R 80 Buschinger, B. 78 D& L.-X. 82 Attard, G. S. 36 Das,A.K. 178 Faltermeier, G. 56 AuguStine, R L. 163 Cai, M.-2. 126 Dap, M. 178 Fan, J. C. 128 Caiazza, A. 82 Davanzo, C. U. 175 Fan, Q. 178 Bm, D.4. 37 Calvo, R L. 127 David, S. A. 177 Famll, N. 174 Baker, A. 161 Cameron, D. C. 83 Davidson, L. 90 Farrugin, L. J. 100 Bajusz, 1.4. 80 cardin, C. J. 177 Daviea, H. M.L. 127 Fenga, P. G. 79 Barlow, S. 81 Carpentier, J.-F. 127 Daviea, H. 0. 78 Fidalgo, E. G. 178 Barnard, C. F. J. 17, 158 Casaw, J. A. 35 Davies, R J. H. 79 Fischer, A. 128 Barth, J. V. 24 castau* Y. 127 Davydov, A. A. 81 Fodor, K 108 Bartle P. N. 36 castellano, E. E. 175 De Blasio, N. 176 Foklrens, R H. 174 Beshilov, V. V. 18 than, H. S. 0. 124 DeGiovaui,W.F. 79 Fords, J. 78 Basset, J.-M. 160 cyhan, M.C.-W. 123 de Meijere, A. 126 FomiW%mer, J. I77 Baur, J. E. 124 chang,J.-R 81 De Souza, J. P. I. 79 Fkter, S. 38 Be,D. 127 chao,s. 125 DeVries J.G. 127, 159 France, D. W. 175 Becker, R 56 che,C.-M. 123, 124 Degi- L. 78 Fremy, G. 127 Bea,H.B. 27,46, 116 Chen, c.-w. 125 DeGraff, B. A. 80 Fry, B. E. 123 Beldarain, T. R 34 Chen, D. 128 Delabouglise,G. 176 Fy W. 73 BeUer, M. 39, 145 Chm,K.Y. 128 Delaude, L. 162 Fq Y. 81 -A.K 38 chen, L. 124 Demes, J. N. 80 Fujie, Y. 82 Benniston, A. C. 100 Chen, M.-Q. 125 Denisov, N. N. 79 Fujii, H. 98

Platinum Metals Rev., 1998, 42, (4), 183-186 183 Page Page Page Page Fujisaki, Y. 39 Ihlimaq A. I76 Ishikawa, H. I28 King, D.A. 8 Fukuda,H. 36 Haniugton, L. J. 175 Islam, M. S. 83 Kirsch-De Mesmaeker, Fukui, M. 37 Harris, J. A. 175 Ito, H. 10 A. 79 FulNshima,N. 83 Harris, M. C. 177 Ito, s.4 38 Kisenyi, M. 57 Fukuyama,T. 126 Hartwig, J. F. I58 Ito, Y. 82 Kishida, M. 126 Fiastner,A. 159, 178 Hmuta, M. 177 Itoh, N. 78 Kitamura, N. 178 Fumya, N. 83 Hasebe, K. 175 Ivanov, A. V. 81 Klausmeyer, K. K. 1 57 Hascgawa, Y. 39 Ivey, D. G. 34 Klier, K. 34 Gamble, S. 98 Hashiguchi, S. 39 Iwakura,c. 35 KlingeMfer, S. 38 Gao, H. 177 Haasan, J. 127 Iwasaki, s. 10 Kobayashi, A. 178 Geibl, c. 78 Hayashi, H. I26 Iwasawa,Y. 38 Kobayashi, H. I78 Geissler, H. 39 Hayfield, P. C. S. 27, Iwuoha, E. I. 37 Kobayaahi, S. 82 Genge, A. R J. I74 46, 116 Jzawa, Y. 39 Kobayashi, T. 177 Gengembre, L. 37 Heck, R M. 126 w M. 83 Kohle, 0. 35 Gielen, E. 39 Hegedlls, L. 108 Kolesnichenko, N. V. 38 Gladysz, J. A. 39, 177 Heinrich, A. 78 JwWL. 79 Koncki, R 37 Goldshleger, N. F. 79 Heitz, W. 38 Jeffery, J. C. I75 Kmdo, T. 35 Goltsov, V. A. 99 Herman, R. G. 34 Jezkova, J. 37 Konovalova N. P. 83 Goltsoq M. V. 99 Herrero, J. 82 JiqM. 81 -is, S. 36 Goluboichaya, M. A. 83 Hemnann, W. A. 145 Jimbo, T. I28 Krauter, J. G. E. 145 Golunski, S. E. 2 Hess, J. S. 34 Jhdra, J. 128 K~kdkin, 106, 174 &eZ, P. 59 Hibbert, D. B. 36 Job, F. 145 V. Yu. G6rnez-Sas0, M. A. 78 Hildebraud, J. P. I77 JOO, S.-K. 34 Kulilrov,A.V. 79 Goodwin, J. G. 80 Kiu, A. F. 39 Juliette, J. J. J. 39, 171 Kumar,A. 39 -V.V. 141 Hill, G. S. 174 Kung, H. H. 125 Goaaage, R A. 176 Hiratani, M. 39 Kaddouri, A. 176 KunimOri,K. 38 Gottberl3, I. 56 mi,K. I77 Kaji, H. 35 Kuntz,E.G. 145 Gozzi, c. 127 Hissler, M. 176 Kakaki, T. 175 Kuramhi,Y. 176 Grkel, M. 35 Hockaday, R 115 Kalli, K. 36, 125 Kurosaka,T. 125 Graze, W. H. 177 Holah, D. G. 174 heda,N. 39, 127 Kurt,R 78 Green, M. L. H. 168 Hor, T. S. A. I24 her,P. 145 Kwtov, L. M. 81 Gregory, 0. J. 125 Horii, H. 83 KandaSamy, K. 99 Kuwano,R 82 Greiner, A. 38 Homes, J. 78 KamhK. 38, 82 Kuzin,A.P. 99 Glifti& w. P. 168 HorvAth, I. T. 39, 145, mg,c. s. 83 Kuzina,I.A. 99 R 177 I71 Kqlunov, M. G. 19 Kw&D.J. 80 Grimblot, J. 37 HOU, X.-L. 82 Kar, D. 178 Grove, D. E. 16 Houbrechtp, S. I75 Kaphimura, Y. 78 Labeau,M. 176 Grubbs, R H. 34, 145, 159 Howard, M. J. I58 Kataura, H. 174 Lahav,M. 81 Gu, J.-H. 124 Hu, W. I75 Kath6, A. 145 Lahoz,F. J. 82 Guelton, M. 37 Hu, Z. 126 Kato, F. 177 Lai,S.-W. 123 Guo, A. 123 Huan, Z. 124 Kato, R. 78, 178 -,RE. 126 Guraq B. 163 Huang, X. 126 Kato4 s. 175 Lam,M.H.W. 124 Gu& w. 78 Hmk, W. T. S. 174 Katsnel'son, A. A. 99 Lambert,RM. 160 Hughes, A. N. I74 Kawasaki, M. 175 Lan, M.-H. 36 HabR, s. 145 Hwang, C. S. 83, 124 Keiderw, T. A. 128 Latef, A. 37 Haberman, J. X. 128 Kelling, S. 8 Lattes, A. 81 Han, K-s. 37 Idoffsson, T. 56 Kelly, J. M. 79 Laurell, M. 56 -wK. 35 Ikenaga, N. 177 Kendall, K. 164 LaVenOG L. 127 HanasaLi,N. 78 Imam= s. 126 Khaselev, 0. 124 Lluzaron, R. 82 Me,K. P. 140 JJlabaIY. 82 Kikuchi, H. 82 Leclercq, G. 37 Hsnkin, D. M. 105 Inoue, H. 35 Kim, H. J. 124 Leclercq, L. 37 Hauyu, A. 178 Inow, s.4. 39 Kim, W. D. 83 Lee, B.-I. 34 Hanylz T. 174 Iorio, L. E. 123 Kim, w.-Y. 126 Lee,B. T. 83 Hara,K. 175 Isaac, I. 127 Kimura, A. 174 Lee, C.-H. 126 Hara, s. 78 Ishiguro, K. 82 Kimura, H. M. 78 Lee, c. P. 128 Harding, I. s. 37 Wii, Y. 178 Kimura, M. 35 Lee, C.-T. 36

Platinum Metals Rev., 1998, 42, (4) 184 Page Page Page Page Lee, J.-H. 125 Matsui, N. 177 Nibbering, N. M.M. 174 Ped, D. R 177 Lee, J.-K. 37 Matsui Y. 39 Nieuwenhuys, B. E. 141 Peters, A. 57 Lee, J. M. 124 Matsumura, Y. I26 Nishio, T. 126 F'falzgd, B. 56 Lee, K. I74 Matsushita,K. 80 Nishiyama, Y. 128 wrmz,K. 124 Lee, K. H. 83 Matt, D. 11, 163 Nix, R M. 37 Picquet, M. 178 Lee, M. Y. 83 Maw,w. 56 Nolan, K. B. 78 Pi- s. 37 Lee, s. I. 83 Mazzocchia, C. 176 Noll, B. C. 79 Pitachke, w. 78 Lee, s.-K. 36 McGrath, R B. 68 Nomum, K. 39 Plassaaud, L. 178 Lemaire, M. I27 McNally, P. J. 83 Noto, V. D. 79 Pletcher, D. 124 Lester, T. P. 34 McNamara, K. P. 125 Novikov, Y. N. 35 Ponina,M. 0. 123 Lev- w. 124 Meli, A. 145 Noyori, R 39 Pope, S. J. A. 174 Lewis. F. A. 99 Menj6n, B. 78 Nyokong, T. 79 Popov, B. N. 123 Li, A.-W. 124 Meyer, A. F. 35 PwVik-Biro,R 81 Li, C.-J. 128 Meyer, T. B. 35 odenkirk, W. 178 Potgieter, J. H. 123 Li, M. 124 Miedaaer, A. 79 oestreich, s. 38 Potter, R J. I40 Li, T. 36 Miki, H. 39 Ogasawara, K. 10 Regosin, P. s. 159 Li, x 125 Milani, B. 160 Oh, H.-S. 34 Price, J. M. 80 Li, X. G. 68 Miller, J. M. 83 Ohga, K. 176 Pringle, P. 26 Li, z. 81 Mills, A. 176 Obkamhi, H. 35 Prins, L. J. 174 Liebl, J. 57 Milstein, D. 81, 159 Ohtsuka, K. 36 Pmkopchuk, E. M. 174 Lima, E. C. 79 Mitchell, S. 36 Ohtsuka, Y. 174 pu, c. 178 Lin, G. 128 Mitose, K. 83 Okano, M. 82 pu, Y. 128 Lin, I. 124 Miyamoto, A. 178 Oh-K. 38 mWRJ. I23 Lin, T.B. 81 Mizugaki, T. 38 OkUmura,Y. I26 puech, L. 81 Likh, U. 174 MocaL, J. 36 OM,E. 83 Liu, L. 178 Modica, E. 34 0- I. 36 Quinn, Y. 90 Liu, Q. 124 Mondal, S. K. 178 okuyama, K. 80 Liu, R 178 Mder,E. 127 oklIyam&s. 80 Raithby, P. R 146 Liu, W. 73 Montanaro, L. 58 Olivier, H. S. 145, I62 Rani V. 125 Long,R 176 Mo~imoto,Yu. 123 Olvera, M. D. L. L. 80 Rao, z. 55 W-kla, 34 Monta, D. K. I77 mte, E. 82 ~~, T. B. 157 M. A. Morhmx, A. 127 Ono, T. 68 Reddington, E. 163 Low, P. J. 175 Mdo,A. 145 O'Regaq B. 175 Rees, L. H. 175 Lu, z. 124 Momer, M. 127 WbA. 177 Rei, M.-H. 80 L-, L-, H. 174 Moulijn, J. A. 69 Om,L. A. 82 Reid, G. 174 LuIldM@ I. I25 MowJ. C. 60, 163 oskarsson, A. 174 Rehhoudt, D. N. 174 Lymao, C. E. 126 Mi~ller,P. 78 -R 35 ReiSinger. C.P. 145 Lynn, D. M. 145 Muralcam, Y. 35 Othonos, A. 36, 125 Reshetnikov, A. v. 123 Murase, K. 83 OtsUkrsK. 83, 175 Rh-, H.-K. 37 Ma, Y. H. 80 Murray, R W. 34 Otto, E. 57 Ric- J. T. 69 Mackie, P. R 100 Owen, J. R 36 Rico-Laaes, I. 81 Maitlis, P. M. 25, 158 Nacltochenk0,V.A. 79 Rivadulla, J. F. 34 Mallouk, T. E. 163 Nagata, H. 126 Parmon, V. N. 141 Rims, J. 34 Maugiaracina,A. 39 Naksgawa, K. 177 Parsons, s. 100 RocaboY, c. 177 Mali- Y. I74 Nakamura,K. 128 Passalacqua,E. 34 Rodriguea, I. D. A. 79 Marder, S. R 81 Nakamura, T. 35 Pastor, E. 79 Romero, J. R 79 Mardilovicb P. P. 80 Narayanaswamy,R 37 PattiSon, D. I. 35 Romero, T. 37 Martin,A. 78 Nart, F. C. 79 Paulose,K. v. 55 Rosenzweig, z. 125 Martin, M. 82 Navarrete, J. 78 Pekala,RW. 83 Rothe, J. 78 Martinez, F. 78 Nawdali, M. 38 Penalva,v. 127 Ruck, M. 34 Mas&& M. 37 Nech,D.C. 123 Peregudova,S. M. 35 Rucnpf, T. 123 Masdeu-Bult6,A.M. 177 Nefedov, S. E. 83, 123 Perez, E. 81 Rusov, V. D. 99 Manu& H. 34 Nephi,N. 10 Periana, R A. 98 Rutherford, D. 177 Masumoto, T. 78 Nep,A. 58 Persoons, A. 175 Ryumstana, T. A. 99 M&M, T. 108 Nestetenlr0,D.A. 83 Peruk, R N. 35 Matmhdi, H. 125 Ng,S. C. 124 P-, M. 35 sadahiro, Y. 82

Platinum Metals Rev., 1998, 42, (4) 185 Page Page Page Page Sadigbi, J. P. 177 Steger, J. J. 126 Twigg, M.V. 56 Wilkinson, G. 168 Sakaguchi, s. 178 Steglich, F. 78 Wilson, S. R 157 Sakahaa,T. 82, 160 Stephan, M. S. 127 Uccello-Barretta, G. 82 Wilton-Ely, J. D. E. T. 39 Sako, T. 82 Stevens, M. G. 55 Uchida, H. 128. 175 Winner& J. 24 Sanger, A. R 81 Skoh, N. I24 Umeno, M. 128 Woodward, R. B. I70 Santhanam, K S. V. 125 Stuart, A. M. I60 Uno, M. 82 WoH, I. M. I23 Sapienza, A. 163 Stull, A. D. 125 Usami, H. 80 Wnesien, K. 78 Sarmgapani, s. 163 Suga, M. 39 Usatov, A. V. 35 wu, L.-z. 124 Sato, A. 178 suk, c.4. 124 utani, K. 126 WyaJ.-F. 174 Satoh, T. 98 Sullivan, J. A. I76 Sawabe, A. 36 SiiSs-Fink, G. I78 Valencia-Godez, XO xiao, z. 124 Sayana, K I75 SWK. 36 M.J. Xie, Q.C. 82 scha- w. c. I45 Suzuki, M. 35 Van Koten, G. 176 Xiong, G.-X. 124 Scheers, P. V. T. 123 Suzuki, s. 174 VanLeeuwen, 25. 145 Xiong, H. 73 Schmid, G. 162 Suzuki, T. 123, 177 P. W. N. M. Xu, G.4 124 Fichumaan, J. 78 Van Veggel, I74 xu, w. 80 Schwartz, D. T. 175 Tabata, M. 82 F. C. J. M. xu, w.-c. 78 Schwaq P. F. 79 Tajima, H. 78 Velasco-Garcia, N. 80 xu, Y. 83 Seaborg, G. T. I70 Takahashi, M. 82 Vergara, M.C. 34 Seddon,K.R 160 Takahashi, S. 68.82 Venijl, G. K. M. I27 Yamada, H. 80 Sekota, M. 79 Takapy Y. 35 vescoli, v. 78 Kamada, Y. 123 Serizawa, T. 125 Takeuchi, R I78 Viswanathan, R 163, 178 Yamagata,A. 177 Settambolo, R 82 Takeznwa, E. I78 Vogel, W. 78 Kamaoaka, I. 175 Sbaharulzamwn, M. 28 Tam, C.N. 128 Volkova, L. M. 83 Kamashiica, T. I26 Shamsuzmha, M. 39 Tan, K-L. I24 VollmUer, F. 39 Yang, R T. 176 Shapley, J. R 174 Tanaka, S. 83 Vrieze, K. I59 Yang, w. 82 She, Y. 80 Tanaka, T. 37 Vytras, K. 37 Yang, Y. 73 Shibata, M. 83 Tamai, T. I08 Yanowky, A. I. 78 shimifll, s. 83 Taube, D. J. 98 Wadowhi, A. 127 YarimiZy T. 38 shim- Y. 35 Taube, H. 98 Waegell, B. 126 Yeager, E. B. 123 Shirai, H. 35 Teat, S. J. I00 Wakabayashi, K 126 Yokoshima, S. 126 Shirai, M. 128 Teleahev, A. T. 38 Walsh, M. 56 Yokota, K. 31.82 Sidorov, A. A. 83, 123 Tempesti, E. I76 wan, c. z. 126 Yon& T. 39, 127 Sigan, A. L. 35 Ten& Y. I77 Wmg, D. 128 Yoshida, Y. 35 Silva, R A. G. D. 128 TerekhOVa, G. V. 38 Wang, E. 36 Yoshjkawa, T. I0 Silva, s. c. 175 Teny, M. 83 Wang, J. H. 36 Yoshimura, N. 145 Simons, K. E. 160 Teunissen, A. J. J. M. 127 Wang, R 38,81 Yu, R I24 Shu,D. 145 Thayumanavan,s. 81 Wan& s. Y. I28 Yuzaki, K. 38 Skelton, B. W. 174, 175 Thomas, J. 78 Wang, X. F. 126 Skryabiha, N. E. 99 Thomas, M. D. 176 Watanabe, M. 128, 175 Zaitseva, N. N. 174 Sliviapky, E. V. 38 Thompson, D. T. 71 Watling, T. C. 176 Zambelli, T. 24 smirnov, L. I. 99 Tishin, B. A. 35 Watson,R 56 Zelentsova, T. N. 99 Smith, A. M. 124 Tokuyama, H. 126 Wells, P. B. 161 Zeng, H. C. 126 Smotkin, E. S. 163, 178 Ttillner, K. 81 Welton, T. 135 m,M. 81 Smyth, M.R 37 Tomalia, D. A. 79 Wendt, H. 128 m,R 34 Sokolov, V. I. 18 Toyota, K. 175 weston, w. I58 zhan& x. 83 Sone, T. 82 Tran, T. D. 83 wetzig, K. 78 zhang, x.4. 35 song, c.4. 126 Troughton, G. 144 White, A. H. 174, I75 zhao, c.-z. 176 Song, H. G. 80 Trzmiak, A. M. 127 White, P. 10,55, 157 Zhao, H.B. I24 Spaine, T. W. 124 Tsai, C.-D. 36 White, R E. 123 Zheng, G. I23 Spek, A. L. 176 Tsai, C. M. 128 Whyman,R 161 zhitomlrq, I. 80 Spek, A. 125 Tsyganok, A. I. 175 Wieckowski, A. 128 Zhu, B. 38,8l Spivak, L. V. 99 Turnas, w. 177 WieSer-Jeune~pe.C. 1 1,163 Zhu, G. 83 sriuv. 177 Tunglcr, A. 108 Wilhelm, T. E. 34 Zieasel, R 176 stasilr, I. I27 Turner, J. A. I24 Wmams, D. S. 164 Zi6lkowski, J. J. 127 Steele, D. F. 90 Turro, N. J. 79 Wills, M. 161 Z-Schpector, J. 175

Platinum Metals Rev., 1998, 42, (4) 186 SUBJECT INDEX TO VOLUME 42 Page Page a = abstract Carbon oxides, CO,(contd.) Acid Chlorides, phenylation, a 126 oxidation, motorcycle emissions, a 126 Acoustic Waves, for catalytic rate enhancement, over Pd-WSiO,, a 38 on Pt surfaces 8 on Pt, Pt-Sn, Pt-Ru electrodes, a 123 N-Acyl Amino Acids, synthesis, a 39 on Pt, sonochemical rate enhancement 8 Alcohols, allyl, hydrogenation, over Pt colloids, a I25 removal, from fuel cell vehicles 2 ethyl, from ethyl acetate, a 38 sensors, a 80, 176 from aldehydes, over Rh clusters, a 38 battery powered 144 from methyl ketones, Rh catalysed, a 39 carbonylation. MeOH, over RhlSDT, WVP,a 176 homoallylic, isomerisation, a 128 propane to butanal, a 82 synthesis, a I78 Catalpis, acoustic enhancement 8 methyl, carbonylation, a I76 biphasic, a 177, 178 from syngas, a I26 book review 145 on-board Hi production, for fuel cell vehicles 2 homogeneous 135 oxidation, in fuel cells, a 128 heterogeneous, a 37-38,8041, 125-126, 176-177 over Pdy-Al,O,, a 38,81 homogeneous, a 39,81-83, 126-128,177-178 primary allylic, oxidation, a 82 conference reports 158 primary, oxidation, a 178 “Catalysis Technical Guide‘‘, Johnson Matthey 72 1 -propanol, 2-propano1, electrooxidation, a 79 Catalp, automotive, at the SAE congress 56 propargyl, reaction with norbomene, a 82 Catalysts, Iridium, lr(IIl)/Ce(lV), cis-4-substituted cyclohexane- 1-methanoh, a 82 formaldehyde oxidation, a 178 synthesis, over Rh-Mo-WAI,O,, a 81 metal oxide-supported, synthesis gas production, a 177 Aldehydes, hydrogenation, over Rh clusters, a 38 Pt(44)/Ru(41)/Os( IO)/Ir(5), for DMFCs 163 synthesis, a 178 Catalysts, Iridium Complexes, hydrogenation, a$-unsaturated, from alcohols, a 82 asymmetric transfer, of aromatic ketones, a 39 Alfa Aesar, “Platinum Labware Catalog” 144 [I~(TFB)(PJP~),]BF,,olefin hydrogenation, a 82 Alkanes, dehydrogenation, by (PCP)lrH, 71 (PCP)lrHI, alkane dehydrogenation 71 Allmres, hydrogenation, biphasic, a 177 on polymer electrodes, hydrogenation 60, 163 Akylation, allylic, allylic acetates, a I78 Catalysts, Osmium, Pt(44)/Ru(41)/0s( IO)/Ir(5), Allmes, a$-functionalisation, asymmetric, a I77 for DMFCs 163 Allylic Acetatea, allylic alkylation, a 178 Catalysts, Osmium Complexes, (DMS0)20s”Pc, Amidea, reduction, via hydrosilylation, a 82 cysteine oxidation, a 79 Amidowrbonylation, Kacyl amino acid synthesis, a 39 Catalysts, Palladium, colloids, Heck reactions, a 38 Am@on, Pd,(dba), catalysed, a 81 on gas diffusion electrodes, in fuel cells, a 83 Ammes, tertiary, from amides, a 82 motorcycle emissions control, a 126 triatyl, synthesis, a 81 PdG-AI,O,, isoprene hydrogenation, a 81 Anilines, arylation, a I77 Pd/y-Al,O,, MeOH oxidation, a 38,81 ha,reactions with I-bromoadamantane. a I26 PdC felt cathode, dechlorination, a I75 Aryl Halides, homocoupling reactions, a 127 PdC, Heck reactions, a I26 Aryl Iodi&s,.phenylation, a 126 Pd(O)/SiO,, phenylation reactions, a 126 Arylation, anilines, a 177 Pd-Rh/Si02, CO oxidation, a 38 PdZrO,, CO hydrogenation, a I26 Pd/Z#,, Pd/SOdZrO,, a 81 Benzene, hydrogenation, biphasic, a I78 in supercritical CO,, Heck, Stille reactions, a 177 oxidation, over Pt-F/AI,O,, a 81 Catalysts, pall ad@^ Complexes, C,Pd(PPh,),, Benzylic Compounds, electrooxidation, a 79 hydrogenation of tnple bonds 18 Book Reviews, “Aqueous-Phase Organometallic halides, for amidocarbonylation, a 39 Catalysis: Concepts and Applications” 145 on polymer electrodes, hydrogenation 60. 163 lnorganica Chimica Acta: Special Volumes on Pd(O), heterocycle assembly, a 177 Platinum Chemistry 17 [Pd(Bu,PetpE)Br](BF,),, CO, reduction, a 79 “Structured Catalysts and Reactors” 69 PdCI,, Heck reactions, a 127 Idromonrlnmantaue, reaction with styrenes, norbomene polymerisation, a 81 arenes, a 126 PdCli(PPh,),, ketone synthesis, a I26 Butanal, from propane, a 82 Pd(dba)2,allenes, asymmetric carbopalladation, a I i7 Butane, reforming, zirconia fuel cells 164 Pd2(dba),, triarylamine synthesis, a 81 Pd(OAc),, Karylated sulfoximines, a 177 Pd(OAc),iDPEphos, aniline arylation, a 177 Cdhrenea, complexes with Pt metals 11, 163 Pd(OAc),/nBaNBr, homocoupling, aryl halides, a 127 Cancer, drugs, a 78,83, 174 PdJs,phen,(OAc),,, alcohol oxidation, a 82 capacitors,a 35,39 Pd phosphine complexes, C02electroreduction, a 79 supercapacitors, RuOJC, a 83 selectivity, towards hydrogenation I08 thin film, Pt/(Ba, Sr)TiO,/Pt, a 83 Catalysts, Platinum, motorcycle emissions control, a 126 (SrRuOJBa,Sr, ,TiO,/SrRuO,), a 83 in PEMFCs, a I28 carbenes, (PCy,),Cl,Ru=CHR, a 34 for photovoltaic devices, a 124 Carbocycles, Pd-catalysed synthesis, a 177 Pt(44)/Ru(41)/0s(10)/1r(5), for DMFCs I63 carbon oxides, CO,, reduction, electrochemical, a 79 Pt( 110) crystal, CO oxidation, sonochemistry R sensors, I#*-, WO,-based, a 125 Pt colloids, allyl alcohol hydrogenation, a I25 supercritical, as catalysis medium I58 Pt, Pt-lO%Rh, HCN synthesis, a 37 Heck, Stille reactions, a 177 Pt/AIIO,, NOx reduction, a 176 0,chemisorption, on RdALO,, a 38 Pt/y-Al,O,, NO reduction, a 125 electrooxidation, on Pt-RdC, a 34 Pt-F/AI,O, benzene oxidation, a 81 hydrogenation, over PdZrO,, a 126 Pt-K /SiO,, methanation, a 80

Platinum Metals Rev., 1998, 42, (4), 187-192 187 Page Page Catalysts, Platinum, (conrd.) Catalysts, Ruthenium Complexes, (mrd.) Pt-Mo-NdSiO, NOx removal, a 37 [R~(4,4'-Me,bpy),(PPh,)(H,O)](C10,)~,benzylic Pt-Mo/SiO, hydrocarbon reactions with H,, a 37 oxidations, a 79 Pt-Rh, 3-way HC/CO/NO conversion, a 126 [Ru=C=C=CR,(L)(Cl)(arene)]PF,,ring closing Pt-SOJZrO,, dehydrogenative CH, coupling, a 125 olefin metathesis, a 178 Pt/H-beta, PVH-MOR, n-hexane isomerisation, a 37 Ru[BINAP], mono-ethyl fumarate, maleate, Pt/MCM-41, NO reduction, a 176 reduction, a 128 Pt/Ru, in fuel cells, a 128 [RuCI2(C,H,)li, hydrosilylation of ketones, a 83 Pfli02/€'TFE, trichlorobenzene photodegradation, a 175 RuCl>(PPh,),, homoallylic alcohol isomerisation, a 128 Catalysts, Platinum Complexes, [(bpym)PtCL], Ru04, electrochemical oxidation of organic waste 90 CHI oxidation 98 Ru(PPh,),Cl,/hydroquinone,alcohol oxidation, a 178 hydrodesulfurisation 25 frans-[Ru(salen)(NO)(H20)]~,ene reactions, a 178 Pt(ll)bis(benzoylacetonate), Pt(I1) bis- "Catalytic Reaction Guide", from Johnson Matthey 16 (trifluoroacetylacetonate), Pt(I1) bis- [2]-catenanes, 0scomplexes 100 (benzoyltrifluoroacetonate), photocuring. a 123 Cathodic Protection, by Pt/Ti electrodes 27,116 Catalysts, Rhodium, biphasic 135 Chemiluminescence,during oxidations, motorcycle emissions control, a 126 by Ru(bpy),'-, a 35 Rh-Mo-WAliOl, alcohol synthesis, a 81 see also Luminescence Rh-Pt, 3-way HCICOINO conversion, a 126 Chlor-Alkali, electrodes, development 27,46 Rl-Pt, HCN synthesis, a 37 Chlorine, sensor, using Ru tris bipyridyl, a 37 Rl-Pd/SiO,, CO oxidation, a 38 Chlmmmatics, herbicides, dechlorination, a 175 Rl-SISiO,, Rh-S-PISiO,, 1 -octene Cisplatin, a 174 hydroformylation, a 177 Clusters, Bi,RhBr,, structure, a 34 Wone-atomic layer GeO,/SiOi, ethyl acetate metallic, catalysis 160 hydrogenation, a 38 Os, OsIRu, OsIHg. OsIAu, RdCu, RuMg 146 WVP,WSDT, MeOH carhonylation, a I76 Pd,,,phen,,(OAc),,,. alcohol oxidation, a 82 RhAJSY, Rh/AI,O,, N,O decomposition, a 38 Rh,(CO),,, aldehyde hydrogenation, a 38 Catalysts, Rhodium Complex?, acacRh(CO)i, Ru,(CO),,(TPPTS), Ru,(CO),(TPPTS),, biphasic hex- 1 -ene hydroformylation, a 38 hydroformylation, hydrogenation I35 chiral diRh(I1) carboxamidate, carbene reactions, a 178 RUC(CO),~,PtRu,C(CO),,(COD), with C,", a 174 CIRh[P(CH,CH,(CF,),CF,),],, alkene Coatings, electrodes, for chlor-alkali cells 27,46 hydrogenation, a 177 Pt, from electroplating bath, a 124 (DMSO)(CI)~"'Pc,[(CN),Rh"'Pc] ,cysteine see also Electrodeposltionand Deposition electrooxidation, a 79 Cold Cathodes, for flat panel display 10 hydroformylation 25 Cold Start, in fuel cell powered vehicles 2 on polymer electrodes, hydrogenation 60, 163 Colloids, Pd, for Heck reactions, a 38 Rh,(OOct),, 2,3-dihydrofuran synthesis, a 127 Pt, ally1 alcohol hydrogenation, a 125 %(CO),,, vinylpyrrole hydroformylation, a 82 formation, light catalysed, a 34 Rh,(CO),, clusters, polymer bound, aldehyde PtRu[N(Oct),CI], alloys, a 78 hydrogenation, a 38 Combinatorid Chemistry, for fucl cell catalysts I63 WPA(Na')/DPPEA polymer, olefin Conferences, 9th International Symposium on hydroformylation, a 127 Relations between Homogeneous and RhCI(CO)(PMe,),, propane carbonylation, a 82 Heterogeneous Catalysis, Southampton, [RhCI (P[CH,CH,(CF,),CF,],},], hydroboration, a 39 England. 20-24 July 1998 160 [RhCI(PPhl),([9]aneS,)]PF,, ligand substitution, a 39 I Ith International Symposium on Homogeneous [Rh(COD)CI],-P(OPh),, allylic alkylation, a 178 Catalysis, St Andrews, Scotland, [Rh(COD)CI],IPPh,, hydroboration, a 82 12-17 July, 1998 158 [Rh(COD)(DlOSR,)]ClO,, styrene 12th International Conference on the Conversion hydroformylation. a 177 of Solar Energy into Photovoltaic Power and [RhH,( Ph,N,)(PPh,),], phenylacetylene Storage, Berlin, Germany, 9-14 August, 1998 140 hydrogenation, a 39, 127 SAE, Detroit, U.S.A., February, 1998 56 RhH(CO)(PPh,),, amide reduction, a 82 Second Anglo-Dutch Symposium, Amsterdam, [Rh(Hdmg)l(PPh,)]2, [Rh(Hdmg)(CIZndmg)(PPh,)],, 26 September, I997 25 I-hexenc hydroformylation, hydrogenation, a 127 Second International Conference on the Hydrogen [Rh(he~adiene)CI]~i4,4'-diheptadecyl-2,2'- Treatment of Materials, Donetsk, Ukraine, bipyridine LB films, a 81 2-5 Junc, 1998 99 RhH(PPhJ),, itol oxidation, a I27 Corrosion Protection, by Pt/Ti electrodes 27, 116 [Rh(norbornadiene)CI],, phenylacetylene reinforced concrete 116 polymerisation, a 82 Coupling Reactions, aryl halides, a 127 Rh(triazolinylidene), hydrosilylation, asymmetric, a 39 Pd catalysed 158 Rh trisulfonated triphenylphosphine, acrylic ester Cyclohe-, 4-substituted 1 methylidene- hydroformylation, a 127 cyclohexanes, hydroboration, a 82 Catalysts, Ruthenium, biphasic 135 from benzenes, a I78 Pt(44)/Ru(41)/0s( 10)/1r(5), for DMFCs 163 cis-Cyclooctene, hydrogenation 156 Ru/AI,O,, H,O/NiO decomposition, a 126 Cyclophaues, Ru, 0scomplexes 100 hydrogenation isotherms, a 38 CycloproPanaton, for mctal carbene reactions, a 178 Ru/AI,OI, butane reforming, zirconia fuel cells 164 norbornene, a 82 Ru/Mn/Ce, waste water oxidation, a 126 Cysteine, electrooxidation. a 79 Ru/Pt, in fuel cells, a I28 RuS,/SiO,, HiO decomposition, a 175 DechloWon, chloroaromatic herbicides, a 175 Catalysts, R~theni~~Complexes, (T~'-C~H,)~RUZCL. Decomposition, H,/N,O, over Ru/A120,,a 126 benzene hydrogenation. a 178 N?O, over Rh, a 38 (rl'-cyclopentadienyl)tris( acetonitrile)Ru, Dehydrogenation, alkanes, by (PCP)IrH, 71 norbornene cyclopropanation, a 82 DehydrogenativeCoupling, CH,, over Pt-SOJZrO,, a 125 [(DMSO),Ru"Pc].2DMSO, cysteine oxidation, a 79 Dendrimm, Pd, synthesis, a I74

Platinum Metals Rev., 1998, 42, (4) 188 Page Page Dendrimers, (contd.) Films, (confd.) photoproperties, with ‘Ru(4,7-(S0,C,H5),-phen),c, a 79 [Ru(bpy),]” in organogel, 0, sensor, a 80 Pt(II), SO, sensor, a 176 Ru(I1)-polymer, photoproperties, a 35 Deposition, chemical spray, Pt:SnO, films. a 80 RuO,, Ru0,-TiO,, on Pt, a 80 Pt, on C nanotubes, a 124 see also Langmuir-Blodgett PZT films, on Pt-coated Si, a 39 see also Thin Films see also Coatings and Electdeposition Flat Panel Displays 10 Detectols, see Sensors Formaldehyde, oxidation, a 178 Diesel Engines, pollution control, at SAE conference 56 Fuel Cells, a 83, 128, 178 Diodes, A1-AI,OI-Pd, H, sensor, a 80 DMFCs, catalysts 163 Diphenylacetylene, hydrogenation 156 Pt-Ru anodes, a 178 Dissociation, CH,, at Pd single crystals, a 34 HotSpotTMreactor, for on-board H, generation 2 DNA, photoaddition to Ru(tap)2(bpy)’+.a 79 NO reduction, Pd catalysts, a 83 PEMFCs, a 128 Electrical Contacts, ohmic contacts, PdPtlAdPd, a 34 portable systems 115 PdSn, Pd/Ge, thermal stability, a 83 Pt/Ru catalysts, MeOH oxidation, a 128 Electrochemistry, a 34-35, 79, 123, 175 zirconia, butane reforming 164 oxidation of toxic organic waste 90 Fullerenes, Ir complexes, a 79 Rh, Ir fullerenes, oxidation, reduction, a 35 Pt metal complexes 18 Ele&dpsition, Ir oxide films, a 124 Pt, Ru complexes, a 174 RuOi, Ru0,-TiO,, on Pt, a 80 Rh, Ir complexes, electrochemical oxidation, see also Castings and Deposition reduction, a 35 Eleclnxh, anodes, 0, evolution 116 Furans, 2,3-dihydrofurans, synthesis, a I27 Pt-foil, dechlorination, a 175 Pt-Ru, for DMFCs, a 178 cathodes, cold, PtlSiOJSilAI, flat panel display 10 Glucose, biosensor, Os/polymer based electrode, a 37 PdC felt. dechlorination, a 175 Gold, reduction, stripping, at Pd, Rh, Ir electrodes, a 36 PEMFCs, a 128 gas diffusion, in fuel cells, with Pd catalysts, a 83 ir oxiddglassy C, a 124 Heck Reactions, Pd catalysed 126, 127, 158 noble metal/oxide coated Ti, development 27,46, 116 Pd colloid catalysed, a 38 Osipolymer, in C paste, glucose sensor, a 31 in supercritical COi, a 177 Pd filmipoly(4-~inyl)pyridine,hydrazine detection, a 36 Heterocycles, Pd-catalysed synthesis, a 177 Pd-coated LaNi,,sAlo,l, a 123 Heterojunctions, TiO,/RuLL’NCS/CuCN, Pd, palladinised, for hydrogenations, a 35 photoproperties, a 175 phthalocyanine modified, cysteine oxidation, a 79 *Hexme, isomerisation, Pt catalysed, a 37 polypyrrole film, with Rh, Ir, Pd 60, 163 1-Hexene, hydroformylation, by acacRh(CO)*, a 38 Pt, bottom, O2diffusion, a 39 hydrogenation 156 in capacitors, a 83 hydrogenation, hydroformylation, a 127 CO sensors 144 History, development of noble metalioxide inorganic ion detection, a 36 coated Ti electrode 27,46, 116 pbotovoltaic devices 140 Geoffre Wilkinson 168 on polymers, medical implants 55 Hotspot9 Reactor, H, generation, on-board with Ru(I1)-modified chitosan, oxalic acid sensor, a 176 fuel cell vehicles 2 Pt, Pta,Rua ,,, electrooxidation, a 79 Hydrazine, detection, at Pd film electrode, a 36 Pt, Pt-Sn, Pt-Ru, CO oxidation, a 123 Hydridea, Rh, Ir complexes, electrocatalysis 60, 163 Pt, Rh, Ir, for Au reduction and stripping, a 36 Hydrohtion, Rh catalysed, a 39 Pt-RdC, electrooxidation, of CO, a 34 4-substituted 1 -methylidenecyclohexanes,a 82 Ru containing, benzylic oxidations, a 79 Hydrocarbons, oxidation, motorcycle emissions, a 126 RuO, nanooarticlesiC aerods..... for sunercaoacitors... a 83 reactions with HI. over Pt-Mo/SiO,, a 37 RUO;, PH sensors, a 37 HY*- on, crude oil, using Pt catalysts 25 Ru0,-VO,, for electrochemical capacitors, a 35 thiophene, a 128 RuOJTi, improved, a 35 Hydrodimerisation, biphasic 135 Electrogalvanising, Zn onto steel strip 116 Hydroformylation, acrylic esters, a 127 Electroless Plating, for Pd composite membranes, a 124 biphasic 135 Pd membranes, a 80 by Rh complexes 25 Pt, onto polymers, for medical implants 55 1-hexene, a 38, 127 Electrolytes, K,PdCI&Fe(CN)dPEG 600, a 79 I-octene, a I77 Electron Trausfer, photoinduced, Ru, 0scomplexes 100 olefins, a 127 Electroplat+g Baths, Pt coatings, a I24 styrene, a 177 Electro- 116 vinylpyrroles, a 82 Emission Control, at SAE congress 56 Hydrogen, absorption, by Pd 141 motorcycle catalysts, a 126 generation, on-board a fuel cell vehicle 2 Esters, acrylic, hydroformylation, a 127 permeability, in Pd,, &, a 78 Etclung, Pt, thin films, a 80 permeation, through Pd membranes, a 128 Ethyl Acetate, hydrogenation, Rh catalysed, a 38 photoproduction, a 124, 175 4Ethyltoluene. from 4-methylstyrene, a 35 reactions with hydrocarbons, over Pt-MoiSiO,, a 37 sensors, a 36,80, 125 Films, hydrous Ir oxide, a 174 storage, using (PCP)lrH, 71 Pd, in H, sensor, a 36 treatment of materials, at HTM-98 conf. 99 polymer, for fi-,Ir-, Pd-substituted, electrodes 60, 163 wave, catalytic, from OsOJcysteine, a 175

Pt. bottom electrodes.1L in caoacitors. a 39 Hydrogen Cyanide, synthesis, over Pt, Pt-lO%Rh, a 37 mesoporous, on Au, a 36 Hydrogenation, aldehydes, over h(CO),sclusters, a 38 WTiOJF’TFE, trichlorobenzene degradation, a 175 alkenes, biphasic, a 177

Platinum Metals Rev., 1998, 42, (4) 189 Page Page Hydrogenation, (contd.) Medical, (conrd.) ally1 alcohol, over Pt colloids, a 125 antitumour properties, a 83 aromatic ketones, asymmetric, Ir catalysed, a 39 razoxane, anti-cancer drug, a 78 benzenes, biphasic, a 178 Medical Uses, a 83 b ip h a si c 135 Membranes, composite, Ru-doped TiO?, a 37 C=O bonds, by Rh LB films, a 81 Pd, by electroless plating, a 124 CO, over Pd/ZrO,, a 126 defect free, a 80 cis-cyclooctene 156 H: permeation, a I28 enantioselective 160 at HTM-98 conf. 99 ethyl acetate, Rh catalysed, a 38 in small fuel cells 115 1-hexene, a I127. 156 Pt-PEMs, for fuel cells, a 128 isoprene, over Pd/S-AI,O,, a 81 Mercury, demercuration, of bis-(alkynyl)mercurials,a 39 isotherms, of C species, on RdALO,, a 38 Methanation, on Pt-K’/SiO,, a 80 o-limonene 156 Methane, conversion to synthesis gas, a I77 4-methylstyrene, using palladinised Pd electrode, a 35 dehydrogenative coupling, a 125 olefins, a 82 dissociation, at Pd single crystals, a 34 organics, at Rh, Ir, Pd electrodes 60, 163 HCN synthesis, over Pt, Pt- 1 O%Rh, a 37 Pd catalysed, liquid-phase, selectivity 108 oxidation, by [(bpym)PtCL] 98 phenylacetylene, diphenylacetylene, a 39. 127, 156 CMethyMyene, hydrogenation, a 35 stilbene 156 Molecular Cages, [(C-R,)~M~(P-CN),~] 157 triple bonds, using C,Pd(PPh,), 18 Hydrosilylation, amides, giving amines, a 82 asymmetric, ketones, a 83 Nau@cles, Pt, optical properties, a 34 methyl ketones, a 39 [(RuC(CO),,)~CU~CI~]~/SO,, hydrogenation catalyst I46 RuOK electrodes, in supercapacitors, a 83 Nanotechnology, C nanotubes, from RhiPd-graphite, a I74 Inorganic Ions, detection, at Pt electrodes, a 36 Pt on C nanotubes, a 124 Internet, Platinum Metals Review I34 Nitrogen, from NO. in fuel cells, a 83 Ionic Liquids, biphasic catalysis 135 Nitrogen Oxides, N,O, decomposition, over Rh, a 38 in catalysis 158, 160 over Ru/A1201.a I26 Iridium, Au reduction and stripping, a 36 NO, reduction, by propene, over Pt/y-Al,O,, a I25 films, hydrous oxide, a 124 over Pt/MCM-41, a I76 lr(001). with diamond thin films, a 36 to N,, in fuel cells, a 83 IIQ, COi sensors, a 125 NOx, reduction, at the SAE conference 56 Iridium Alloys, IrAl, Ir, ,Ni,AI, structural properties 68 lean bum. over Pt/AI,O,, a 176 1r.S *, thin films, a 78 removal, over Pt catalysts, a 37 Iridium Complexes, fullerenes, electrochemical Norbornme, cyclopropanation. a 82 oxidation, reduction, a 35 polymerisation. PdCI, catalysed, a 81 H,lr(PPh,),, interaction with C,, a 79 photoreactions 73 Isomerisation,n-hexane, Pt catalysed, a 37 1-Octene, hydroformylation, a 177 homoallylic alcohols, a 128 Ohmic Contacts, see Electrical Contacts Isoprene, hydrogenation, over Pd/G-AI,O,, a 81 Olefins, hydroformylation, a 127 Itols, unprotected, oxidation, a 127 hydrogenation. a 82 ring closing metathesis, a 178 Johason Matthcy, “Catalysis Technical Guide” 72 Optical properties, Pt nanoparticles 34 “Catalytic Reaction Guide” 16 Ru(l1) 4,4‘-bipyridinium complexes, a I75 HotSpotTMreactor 2 RuSi, a 78 Internet 134 Organic Industrial Waste, destruction, new autocatalyst manufacturing plant in Argentina 59 electrochemical 90 “Platinum 1998” 105 Osmium Complexes, bis-bipyridyl, polymer modified, glucose biosensor, a 37 Ketones, aromatic, asymmetric hydrogenation. a 39 clusters, 0s. Os/Ru, OsiHg, OsiAu 146 asymmetric hydrosilylation, a 83 [Os(bipy),(L)]”’,molecular assemblies I00 methyl, hydrosilylation, a 39 Os(PP,)H,. photochemical properties, a 35 synthesis, using PdCli(PPh,),, a I26 Os(VllI)OJcysteine, H, wave, a I75 Oxalic Acid, sensor, a I76 Lactams, synthesis, a 178 Oxidation, benzene, over Pt-F/AI,O,, a 81 Lactones, synthesis, a 178 CO, over Pd-RhiSi02, a 38 Langmuir-Blodgett Films, Rh complex, on Pt surfaces, sonochemistry 8 C=O hydrogenation, a 81 CO, HC, motorcycle emissions, a 126 see also Films electro. benzylic compounds, a 79 Lean Bum, engines, at SAE conference 57 CO, on Pt, Pt-Sn. Pt-Ru electrodes. a 123 NOx reduction, a I76 on Pt-RuiC, a 34 D-Limonene, hydrogenation 156 cysteine, by phthalocyanines, a 79 LuminwcenCe, ECL, in oxalic acid sensor, a 176 1 -propanol, 2-propanol, a 79 Rdpolymer complexes, pH sensors, a 80 toxic organic waste, by RuO, 90 [Ru(bpy),]’-, Oi sensor, a 80 electrochemical, of Ir, Rh fullerene complexes, a 35 see also Chemilumhmcence formaldehyde, a 178 MeOH, in fuel cells, a 128 Magnetic Fmpertiea, Pd/Co thin film multilayers, a 34 over Pd/y-Al,O,, a 38,81 Magnetism, in PtCo thin films, a 123 methane, by [(bpym)PtCI,] 98 Medical, cisplatin, anti-cancer, a 174 synthesis gas production, a 177 implants, Pt-coated 55 Na anthracenide, pyrenide. by Ru(bpy),”, a 35 trans-[Pt(NC5H,C(O)NHC2H,oNo,)2C121. partial, butane reforming 164

Platinum Metals Rev., 1998, 42, (4) 190 Page Page Oxidation, (contd.) Photosynthesis, artificial models, Ru, 0scomplex ;es 100 primary alcohols, a 178 Photovoltaic Cells, with c~s-Ru"(LH,),(NCS)~,a 35 primary allylic alcohols, a 82 Photovoltaic Devices, at solar energy conference 140 unprotected itols, a 127 H2 production from H,O, a 124 waste water, domestic, over RdMdCe, a 126 "platinum 1998" 105 Oxygm, diffusion, in Pt bottom electrodes, a 39 Platirmm,Au reduction and stripping, a 36 dissociation, at Pt surfaces, mechanism 24 deposition, on C nanotubes, a 124 evolution, lr0,/Taz05anode coatings 116 onto polymers, medical implants 55 photoproduction,.. from HiO, over RuS,/SiO?, a 175 electrodes, CO sensors 144 sensor, a 80 inorganic ion detection, a 36 fibre-optic, Ru-based, a 125 oxalic acid sensor, a 176 oDtical. a 176 films, bottom electrodes. 0, diffusion, a 39 photoluminescent, with Pt porphyrin, a 36 mesoporous, on Au, a 36 nanoparticles, optical properties, a 34 Palladium, P-[(CHI),N][Pd(dmit)J2, superconductor, a 178 Pd/Pt/AdPd ohmic contacts, a 34 electrodes, Pd-coated LaNi,,Al,,,, a 123 polymer-coated Pt plates, in transistors, a 125 film electrode, in hydrazine detector, a 36 polymers, containing Pt, a 123 film, in H, sensor, a 36 Pt( 1 10) crystal, sonochemistry 8 H, treatment, at HTM-98 conf. 99 Pt( I1 I) surface, mechanism of Oi dissociation 24 membranes, composite, by electroless plating, a 124 Pt:Sn02 thin films, as CO sensors, a 80 defect free, a 80 Pt. Pb,,Ru, ,,, electrooxidation, a 79 for fuel cells 115 Pt, Pt-Sn, Pt-Ru electrodes, CO oxidation, a 123 H, permeation, a 128 Pt-coated Si, PZT film growth, a 39 neutral atoms, Fourier transform spectrum, a I74 Pt-PEMs, for fuel cells, a 128 palladinised Pd electrode, for hydrogenations, a 35 Pt-Ru anodes, for DMFCs, a 178 Pd-AI,O,-AI, H, sensor, a 80 Pt-RdC, electrooxidation, of CO, a 34 Pd/Co multilayer thin films, magnetic properties, a 34 PtlSiOJWAl, cold cathodes 10 PdGaN Schottky diode, a 128 with RuOi, RuO,-TiO,, films, a 80 Pd/Ge/Pd interlayers, between n-GaAs and Si, a 128 thin films, by etching, a 80 Pd/Pt/AdPd ohmic contacts, a 34 on SiO& by MOCVD, a 124 Pd/Rh-graphite, C nanotube production, a 174 Ti/Pt/Au, Schottky contact with InGaP, Pd/Sn, Pd/Ge, ohmic contacts, a 83 photodetectors, a 36 Pd/SnO, thin film, CO sensor, a 176 Platinum Alloys, Pt, ,Al,.,, phase transitions, a 78 PdH particles, imaging 141 PtCo thin films, magnetic properties, a 123 single crystals, CH, dissociation, a 34 PtRu[N(0~t),Cl]~colloids, a 78 thin films, H2 sensors, a I25 Platinum complexes, calixarenes 11, 163 Palladium Alloys, H, treatment, at HTM-98 conf. 99 fullerenes 18 Pd,.,,Si,, H2permeability, a 78 [NBb][fran~-Pt"(C,F~)~Br(C0)],structure, a 78 PdCr, strain gauges, a I25 (OC)Pt[p-N,N'-N(NPh)CJL]r Ti-Pd-Ni, shape memory properties, a 83 ReCI[NH(NPh)C,H,], a 123 Palladium Complexes, P'-Et,Me,P[Pd(drnit),],, photoreactions 73 superconductor, a 78 [PtlL'2(p-dppm)l~,[PtJ-'2(p-dppm)l*-, calixaienes 11, 163 photoproperties, a 124 dendrimers, from Pd[CH,CN],(BF,),, a 174 Pt porphyrin, for 0,sensing, a 36 fullerenes 18 cis-[PtCI2(NH,),], cisplatin, a 174 K,PdCh/K,Fe(CN)dPEG 600 electrolyte, a 79 cis-, frans-[PtCI,(PhCH,CN)i], [Pd(L)](PF&, synthesis, a I74 [Pt(EtCN),] [ S0,C FA]? 106 photoreactions 73 cis-PtCl,(razoxane), structure, a 78 Patents 4W,84-88, 129-132, 179-182 [ (Pt(CN)(CloH,INl))s],photoproperties, a 123 pH, sensors, a 37,80 Pt(ll) dendrimers, SO2 sensor, a 176 wenylacetylene, homologs, hydrogenation, a 127 [Pt(L)](PFs),, synthesis, a 174 hydrogenation 39, 156 trans-[Pt(NCIH,C(0)NHC,H,ONOi)lCli], polymerisation, a 82 antitumour properties, a 83 Phenylation, acid chlorides, aryl iodides, a 126 Pt(N0,)(H20)'*, in electroplating baths, a 124 phoaphines, sulfonated, H,O-soluble catalysts 135 PtRu5C(CO),.(COD), with C,, a I74 Photccatalysk,,photocuring, "platinum Labware Catalog", Alfa Aesar 144 of ceramic precursors, a 123 Pollution Control, at 2nd Anglo-Dutch Symposium 25 F'hotoumvemion,a 35.79, 123-124, 175 at the SAE conference 56 Phot&t&or, a 36 toxic waste, electrochemical destruction 90 Photonics, LEDs, a 81 using fuel cell powered vehicles 2 Ph~bppties,'R~(4,7-(SO,C~~),-phen),~, Polyamtylene, from phenylacetylene. a 82 with dendrimers, a 79 Polyketones, synthesis 158 in combinatorial chemistry 163 PolymerisatiOn, norbornene, PdCI, catalysed, a 81 PfliOJPTFE, trichlorobenzene degradation, a I75 phenylacetylene, a 82 [ (Pt(CN)(C,,H,,N!)I,l, a 123 Ru catalysed 158 Pt(1I) complexes, in probes for SDS micelles ,a 124 Polymm,containing Pt, a 123 Ru dye molecules, on TiO, surfaces, a 124 electrolytes, a 79 Ru(PP3)H2,Os(PP,)H2, a 35 films, with Pt, in 0, sensors, a 36 RuS,/SiO,, H20decomposition, a 175 with Ru(ll), photoproperties, a 35 bis(terpyridyl)Ru(lI), a 176 with Pd colloids, Heck reactions, a 38 TiOJRuLL'NCSICuSCN heterojunction, a 175 polypyrrole film electrodes, with Rh, Ir, Pd 60, 163 Photoreadons, in cyclophanes and catenanes 100 Pt coated, for medical implants 55 H,Ir(PPh,), with Cm,a 79 Rh/PPA(Na+)/DPPEA, olefin hydroformylation, a 127 Pt, Pd, Ru, Ir, Rh complexes 73 siloxane ring, in Ru pH sensors, a 80 Ru(tap)2(bpy)'', addition to DNA, a 79 synthesis, Pd catalysed 160

Platinum Metals Rev., 1998, 42, (4) 191 Page Page Ropane, carbonylation. a 82 Ruthenium Compounds, ( conrd. ) Protoas, reduction, by Rh. Ir. Pd complexes 60, I63 (SrRuO,/Ba,Sr, ,TiOdSrRuO?).thin film capacitors. a 83 Razoxane, anti-cancer drug, a 78 Schottky Contacts, InGaP. with TiiPtlAu. Reduction, electro. CO,, Pd catalysed, a 79 photodetectors, a 36 electrocatalytic, of protons 60. 163 Schottky Diode, PdiGaN, a 128 electrochemical. of Ir. Rh fullcrcnc complexes, a 35 Selectivity, in Pd catalysed hydrogenations 108 mono-ethyl fumarate, maleate, a 128 Sensors, CI2. using Ru tris bipyridyl. a 37 NO, by propene. over Pt/y-Al,O,. a 125 CO,, Ir02-. W0,-based. a I25 tertiary amides, by hydrosilylation, a 82 CO, battery powered I44 Reformin& butane, zirconia fuel cells I64 Pd!Sn02 thin films. a 176 Relay Switches, in heterocycle. Sn0,:Pt films. a 80 carbocycle assembly, a 177 glucose, with Osipolymer complcx. a 37 Rhodium, Au reduction and stripping, a 36 H:, AI-AI?O,-Pd diode. a 80 Rh/Pd-graphite, C nanotube production, a I74 by Pd film, a 125 Rhodium Co@exe~, [(C,Rs),Mx(p-CN),,]. thermal, with Pd films, a 36 molecular cages 157 inorganic ions, at Pt elcctrodes, a 36 calixarenes 11. 163 O?,by [Ru(bpy),]' , in organogel. a 80 fullerenes, electrochemical oxidation. reduction. a 35 fibre-optic. Ru-based. a 125 photoreactions 73 optical. a I76 Rhodium Compounds, BiXhBr,, structure, a 34 photoluminescent. a - 36 Ruthenium, Pt-RdC, electrooxidation, of CO. a 34 oxalic acid, a I76 Ru-doped TiOl composite membranes. a 37 Pd(l), properties, a 174 Ru-Pt anodes, for DMFCs, a I78 pH, at RuO? electrodes, a 37 Ru-Pt electrodes, CO oxidation, a I23 luminescent Ru complexes. a xo RuO:-VO,, dip-coated electrodes, photo, performance. a 36 electrochemical capacitors. a 35 SO,. by Pt(lI) dendrimers. a 176 RuOJTi electrodes, from RuOl-La20,/Ti, a 3s strain, a 125 TiOdRuLL'NCSiCuSCN heterojunction, Shape Memory, in Ti-Pd-Ni. a 81.. photoproperties, a 175 Sodium Antbwnide, oxidation, by Ru(bpy),", a 3s Ruthenium Alloys, PtRu[N(Oct),CI], colloids, a 78 Sodium Pyrenide, oxidation, by Ru(bpy)?'*, a 35 Ru, ,,Ph,, electrooxidation, a 79 Smochemislry, for catalytic rate enhancement. Ru modified Fe40Cr. Fe-35Cr-5Al. a 123 on PI surfaces 8 RuSi, optical properties, a 7x Spectra, Pd(l). properties, a 174 Ruthenium Complexes, 'R~(4,7-(SO,C,H,)~-phen),i. Sputtering, of PdKo thin film multilayers. a 34 with dendrimers, photoproperties, a 79 Stilbene, hydrogenation IS6 tris(2,2'-bipyridine)Ru( I I)-modified chitosan. Stille Reactions, in supercritical CO,. a 177 oxalic acid sensor, a 176 Strain Gauges, PdCr thin films, a 12s tris(5-acrylamid0,l ,I0 phenanthroline) Ru chloride, Styrene, from phenylacetylene. Rh catalysed. a 39 O2 sensor, a I25 hydroformylation, a I77 tris-bipyridyl, CI2 sensor. a 37 reaction with I-bromoadamantane, a 126 [(bpy),Ru(phendione)I(PF,)I, Sulfoximines, N-arylated, synthesis, a I77 [(bpy),Ru(phendioxime)](PF,)~, Sulfur Dioxide, sensor, Pt( 11) dendrimers. a 176 photoproperties, a I24 Supercapacitors, Ru0: nanoparticlesiC aerogels, a 83 calixarenes 11. 163 Superconductor, P'-Et,Me2P[Pd(drnit),],. a 78 clusters, RdOs, RdCu RdHg I46 I.1-[(CH,),N][Pd(dmit)~]~,a 178 photoreactions 73 Supramolecules, Ru, 0s complexes. electron transfer 100 RuC(CO),,, PtRu,C(CO),,(COD), with C,. a 1 74 Surface Science, H. uptake on Pd 141 [R~(bipy)~(L)]".molecular assemblies 100 Pd(0) surfaces 160 [Ru(bpy),]- , 0,sensor, a 80 Synthesis Gas, from methane. a I77 Ru(bpy)l'*, oxidation of Na anthracenide, pyrenide, a 35 giving MeOH, a 126 [Ru(bpy)l'(PhB )?I, optical 0, sensor, a I76 [Ru(bpy)N(bpy(C02MePEG-3S0),),.,](C10,)2. ThinFilms, capacitors. Pt/(Ba, Sr)TiO,/Pt. a 83 molten salts, a 34 (SrRuOJBaSr, ,TiOdSrRuO,), a 83 [Ru(CO),(PPh,)(rl-C,Mer)l[Fe~(~~-C2Bu')(CO)"],a 174 diamond, epitaxial. on Ir(001). a 36 cis/trans-RuH,(Ph,PCH,PPhi)i, lrS, ". a 78 ~ncRuHCI(Ph,PCH.PPh,),. a I74 Pd, H2sensors. a 12s RU(I~'-C(CN)~C[C=C{ Ru(PPh,)Fp] ]C=C(CN).)- PdKo multilayers, magnetic properties. a 34 (PPhXp, a 175 PdiSnO,, CO sensor, a 176 Ru(H)(H,)CI(PCy,),, reactivity, a 34 PdCr, strain gauges, a 125 Ru(II)(2 2'-bipyridyl-4.4'dicarboxylate),(NCS).. Pt:SnO,, as CO sensors, a 80 photovolth 140 Pt. etched, a 80 Ru(I1) 4,4'-bipyridinium. optical properties, a 175 on SiOJSi, by MOCVD, a 124 Ru(lI), in polymer film, photoproperties. a 35 PtCo, magnetic properties. a 123 cis-Ru"(LH,),(NCS),, sensitiser for see also Films photovoltaic cells, a 35 Transistors, polycarbazole conducting polymer. a 125 trans-[Ru(NH,),L(NO)](BF,),, a 175 Trichlorobemme, photodegradation, a I75 [R~(phen)~[phen(OH)~]]'-,[Ru(Ph2phen)?- [phen(OH),]]", pH sensors, a 80 Vinylpymles, hydroformylation. a 82 Ru(PP,)Hi, photochemical properties, a 35 Ru(tap),(bpy)'+, addition to DNA, a 79 Waste, industrial, destruction 90 bis(terpyridyl)Ru(ll), photoproperties, a 176 Water, domestic, oxidation, a 126 Ruthenium Compounds, Ru02, pH sensors, a 37 photodecomposition, over RuS,/Si02, a I75 RuO?, Ru02-Ti02,films, on Pt. a 80 waste, oxidation, over RdMniCe, a I26 RuO, nanoparticlesiC electrodes, in supercapacitors. a 83 Willrinson, Geoffrey. Prof. Sir 168

Platinum Metals Rev., 1998, 42, (4) 192