Platinum Metals Review

VOLUME 55 NUMBER 2 APRIL 2011

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A quarterly journal of research on the platinum group metals and of developments in their application in industry http://www.platinummetalsreview.com/

APRIL 2011 VOL. 55 NO. 2 Contents

Microstructure Analysis of Selected Platinum Alloys 74 By Paolo Battaini

The 2010 Nobel Prize in Chemistry: 84 Palladium-Catalysed Cross-Coupling By Thomas J. Colacot

Dalton Discussion 12: Catalytic C–H 91 and C–X Bond Activation A conference review by Ian J. S. Fairlamb

A Healthy Future: Platinum in Medical Applications 98 By Alison Cowley and Brian Woodward

Fuel Cells Science and Technology 2010 108 A conference review by Donald S. Cameron

11th International Platinum Symposium 117 A conference review by Judith Kinnaird

The Discoverers of the Rhodium Isotopes 124 By John W. Arblaster

“Asymmetric Catalysis on Industrial Scale”, 2nd Edition 135 A book review by Stewart Brown

Publications in Brief 140

Abstracts 142

Patents 146

Final Analysis: Flame Spray Pyrolysis: 149 A Unique Facility for the Production of Nanopowders By Bénédicte Thiébaut

Editorial Team: Jonathan Butler (Publications Manager); Sara Coles (Assistant Editor); Margery Ryan (Editorial Assistant); Keith White (Principal Information Scientist) Platinum Metals Review, Johnson Matthey Plc, Orchard Road, Royston, SG8 5HE, UK E-mail: [email protected]

Microstructure Analysis of Selected Platinum Alloys

doi:10.1595/147106711X554008 http://www.platinummetalsreview.com/

By Paolo Battaini Metallographic analysis can be used to determine the 8853 SpA, Via Pitagora 11, I-20016 Pero, Milano, Italy; microstructure of platinum alloys in order to set up E-mmail: [email protected] working cycles and to perform failure analyses. A range of platinum alloys used in jewellery and industrial applications was studied, including several commonly used jewellery alloys. Electrochemical etching was used to prepare samples for analysis using optical metallography and additional data could be obtained by scanning electron microscopy and energy dispersive spectroscopy. The crystallisation behaviour of as-cast alloy samples and the changes in microstructure after work hardening and annealing are described for the selected alloys.

Introduction Optical metallography is a widely used investigation technique in materials science. It can be used to describe the microstructure of a metal alloy both qualitatively and quantitatively. Here, the term ‘microstructure’ refers to the internal structure of the alloy as a result of its composing atomic elements and their three-dimensional arrangement over dis- tances ranging from 1 micron to 1 millimetre. Many alloy properties depend on the microstructure, including mechanical strength, hardness, corrosion resistance and mechanical workability. Metallography is therefore a fundamental tool to support research and failure analysis (1–3). This is true for all industrial fields where alloys are used. A great deal of literature is available on the typical methods used in optical metallography (4–6). A large amount of useful information is available in the literature for precious metals in general (7–10). However, there is less information specifically focussed on platinum and its alloys. The present work aims to give some examples of platinum alloy microstructures, both in the as-cast and work hardened and annealed conditions, and to demonstrate the usefulness of optical metallography in describing them. This paper is a revised and updated account of work that was presented at the

24th Santa Fe Symposium® on Jewelry Manufacturing condition, the initial samples must have the same Technology in 2010 (11). size and shape. Mould casting or investment casting can produce different microstructures, with different Materials and Methods grain sizes and shapes, depending on parameters A wide variety of platinum alloys are used in jew- such as mould shape, size and temperature, the ellery (12–18) and industrial applications (10,19–21). chemical composition of the mould, etc. Therefore, Different jewellery alloys are used in different markets whenever possible, the specimens for the present around the world, depending on the specific coun- study were prepared under conditions which were as try’s standards for precious metal hallmarking. The similar as possible, including the casting process. alloys whose microstructures are discussed here The specimens were prepared by arc melting and are listed in Table I. These do not represent all the pressure casting under an argon atmosphere to the alloys available on the market, but were chosen as a shape shown in Figure 1. A Yasui & Co. Platinum representative sample of the type of results that can Investment was used, with a final flask preheating tem- be obtained using metallographic techniques. The perature of 650ºC. The captions of the micrographs related Vickers microhardness of each alloy sample, specify whether the original specimen is of the type measured on the metallographic specimen with a described above. load of 200 gf (~2 N) in most cases, is given for each The preparation of the metallographic specimens microstructure. consists of the following four steps: sectioning, If metallographic analysis is aimed at comparing embedding the sample in resin, polishing the metallo- the microstructure of different alloys in their as-cast graphic section, and sample etching for microstructure

Table I Selected Platinum Alloys

Composition, wt% Melting rangea, Vickers microhardnessb,

ºC HV200

Pt 1769 65c Pt-5Cud 1725–1745 130 Pt-5Cod 1750–1765 130 Pt-5Aud 1740–1770 127 Pt-5Ird 1780–1790 95 Pt-5Rud 1780–1795 125 70Pt-29.8Ire 1870–1910 330 70Pt-30Rh 1910f 127 90Pt-10Rh 1830–1850f 95 60Pt-25Ir-15Rh n/a 212 aSome melting ranges are not given as they have not yet been reported bThe microhardness value refers to the microstructure of samples measured in this study and reported in the captions of the Figures c HV100 dThese alloys are among the most common for jewellery applications. Where it is not specified, it is assumed that the balance of the alloy is platinum eThis alloy composition is proprietary to 8853 SpA, Italy fSolidus temperature

Microstructures of the Platinum Alloys Diameter: In this section the microstructures of the selected 25 mm platinum alloys in different metallurgical conditions are presented. As already stated, this selection is a representative sample and not a complete set of the platinum alloys which are currently on the market.

As-Cast Microstructures: Metallography of Crystallisation Examination of the as-cast microstructures shows Cross-ssection diameter: 3 mm the variation in size and shape of the grains in different platinum alloys. However, a noticeable dendritic Fig. 1. General shape of specimens grain structure is quite common. The largest grain prepared by investment casting for this size was found in platinum with 5 wt% copper study. The microstructures of different alloys (Pt-5Cu) (Figure 2) and platinum with 5 wt% gold obtained by investment casting can be (Pt-5Au) ( ), with sizes up to 1 mm and 2 mm, compared, provided that the specimens have Figure 3 the same size and shape. The dashed line respectively. The Pt-5Au alloy sample also shows shows the position of the metallographic shrinkage porosity between the dendrites. The core sections examined in these samples of the dendritic grains showed a higher concentration of the element whose melting temperature was detection. The detailed description of these steps the highest in both cases. This behaviour, known as will not be given here, as they have been discussed ‘microsegregation’, has been widely described (12, in other works (4–10). 23, 24). Electrolytic etching tended to preferentially Further advice relevant to platinum alloys was given dissolve the interdendritic copper- or gold-rich in the 2010 Santa Fe Symposium paper (11) and in regions, respectively. In a platinum with 5 wt% iridium this Journal (22). In these papers, procedures for the (Pt-5Ir) alloy (Figure 4), since iridium has the higher metallographic analysis of most platinum alloys are melting temperature, the dendritic crystals were described. The samples for the present study were enriched in iridium in the first solidification stage. prepared by electrolytic etching in a saturated solution It is important to point out that the higher or lower of sodium chloride in concentrated hydrochloric visibility of microsegregation within the dendrites is acid (37%) using an AC power supply, as described not directly related to the chemical inhomogeneity, previously (22). but to the effectiveness of the electrolytic etching in

500 µm 500 µm 500 µm

Fig. 2. As-cast Pt-5Cu alloy showing Fig. 3. As-cast Pt-5Au alloy showing Fig. 4. As-cast Pt-5Ir alloy with dendritic grains with copper shrinkage porosity between the columnar grains (sample shape microsegregation (sample shape as dendrites (sample shape as in as in Figure 1; flask temperature in Figure 1; flask temperature 650ºC; Figure 1; flask temperature 650ºC; 650ºC; microhardness microhardness 130 ± 4 HV200 ) microhardness 127 ± 9 HV200 ) 95 ± 2 HV200 )

revealing it. For example, the microsegregation in the However, because EDS is a semi-quantitative platinum with 5 wt% cobalt (Pt-5Co) alloy is hardly method, it can only give the general distribution of visible in Figure 5, despite being easily measurable by the elements on the metallographic section. It is other techniques (24). worthwhile remembering that metallographic prepa- Scanning electron microscopy (SEM) and energy ration reveals only a few microstructural features. By dispersive spectroscopy (EDS) are very effective in changing the preparation or the observation tech- showing the presence of microsegregation. Figure 6 nique, some microstructural details may appear or shows an as-cast sample of a platinum with 25 wt% become more clearly defined, while others remain iridium and 15 wt% rhodium alloy (60Pt-25Ir-15Rh). invisible. The SEM backscattered electron image is shown in The melting range of the alloy and the flask pre- Figure 7.The EDS maps in Figures 8–10 give the ele- heating temperature affect the size and shape of mental distribution on the etched surface.If the maps grains significantly. In order to decrease the dendritic were obtained on the polished surface the approxi- size and obtain a more homogeneous microstructure, mate concentration of each element may be different the temperature of the material containing the solidi- due to the etching process and a possible preferen- fying alloy is lowered as much as possible. The effec- tial dissolution of different phases of the alloy. tiveness of such an operation is, however, limited by

50 µm

Fig. 7. 60Pt-25Ir-15Rh alloy: 500 µm 200 µm scanning electron microscopy (SEM) backscattered electron Fig. 5. As-cast Pt-5Co alloy Fig. 6. 60Pt-25Ir-15Rh alloy cast image of the etched sample. The with small gas porosity (sample in a copper mould. From the sample is the same as that shown shape as in Figure 1; flask transverse section of an ingot in Figure 6 temperature 650ºC; microhardness (microhardness 212 ± 9 HV200 ) 130 ± 6 HV200 )

50 µm 50 µm 50 µm

Fig. 8. 60Pt-25Ir-15Rh alloy: Fig. 9. 60Pt-25Ir-15Rh alloy: Fig. 10. 60Pt-25Ir-15Rh alloy: energy dispersive spectroscopy energy dispersive spectroscopy energy dispersive spectroscopy (EDS) platinum map acquired (EDS) iridium map acquired on (EDS) rhodium map acquired on on the surface seen in Figure 7, the surface seen in Figure 7. The the surface seen in Figure 7. The showing the platinum microsegre- iridium concentration is lower rhodium distribution follows the gation. The network of high where that of platinum is higher behaviour of iridium. The zones of platinum content shows this higher iridium and rhodium content approximate composition (wt%): show this approximate composition 72Pt-14Ir-14Rh (wt%): 55Pt-28Ir-17Rh

the melting range and by the chemical composition the high iridium and rhodium content also con- of the alloy. An example of the flask temperature tributed to the lower grain size in the as-cast sample. effect is shown in Figure 11 for Pt-5Ir poured into a Homogenising thermal treatments result in a flask with a final preheating temperature of 890ºC. microstructural change. Comparing Figure 16 with This microstructure is to be compared with that in Figure 17 highlights a reduction in microsegregation Figure 4, in which a flask preheating temperature of in Pt-5Cu as a consequence of a homogenisation 650ºC was used. treatment performed at 1000ºC for 21 hours. A smaller grain size was observed in the platinum with 5 wt% ruthenium (Pt-5Ru) alloy, which showed Work Hardened and Annealed a more equiaxed grain (Figure 12) with a grain size Microstructures: Metallography of of about 200 µm. The addition of ruthenium led to Deformation and Recrystallisation finer grains in the platinum alloy. Optical metallography can reveal the changes in Pouring the alloy in a copper mould produces microstructure that occur after work hardening and a smaller grain size due to the high cooling rate, as recrystallisation thermal treatments and allows visible in Figure 6 and Figures 13–15. In this case, recrystallisation diagrams like the one in Figure 18 to

500 µm 500 µm 200 µm

Fig. 11. As-cast Pt-5Ir alloy (sample Fig. 12. As-cast Pt-5Ru alloy showing Fig. 13. 70Pt-29.8Ir alloy: cast in a shape as in Figure 1; flask shrinkage porosity at the centre of copper mould. From an ingot trans- temperature 890ºC; microhardness the section (sample shape as in verse section. A high iridium content 105 ± 2 HV200 ) Figure 1; flask temperature 650ºC; contributes to grain refinement microhardness 125 ± 5 HV200 ) (microhardness 330 ± 4 HV200 )

200 µm 200 µm 500 µm

Fig. 14. 70Pt-30Rh alloy: cast in a Fig. 15. 90Pt-10Rh alloy: cast in Fig. 16. Higher-magnification image copper mould. From the transverse a copper mould. From the trans- of as-cast Pt-5Cu alloy showing section of an ingot. A high rhodium verse section of an ingot. The gas dendritic grains with copper micro- content enhances the grain porosity is visible (microhardness segregation (microhardness 130 ± 4 refinement (microhardness 95 ± 5 HV200 ) HV200 ). Compare with Figure 17 127 ± 9 HV200 )

Fig. 17. Pt-5Au). However, after annealing, the microstructure Microstructure becomes homogeneous and the fibres formed after to of Pt-5Cu alloy the drawing procedure are replaced by a recrystallised after thermal treatment at microstructure (Figures 23 and 24). Using the tech- 1000ºC for 21 niques described elsewhere (11),analyses can be per- hours. The formed even on very thin wires,as shown in Figure 25 microsegregation of for a platinum 99.99% wire of 0.35 mm diameter. copper is It is worth pointing out that some binary platinum reduced (micro- alloys have a miscibility gap at low temperatures, as hardness 120 ± shown by their phase diagrams (19, 20, 25). Examples 4 HV ). 200 of this are given in Figures 26 and 27 for Pt-Ir and 500 µm Compare with Figure 16 Pt-Au, respectively. Similar behaviour is observed for Pt-Co, Pt-Cu and Pt-Rh alloys. As a consequence, a biphasic structure is expected be drawn. This makes it a valuable aid in setting up of each of them. However, this may not occur for var- working cycles. It is necessary to establish the right ious reasons. The phase diagrams refer to equilibrium combination of plastic deformation and annealing conditions, which hardly ever correspond to the treatment in order to restore the material’s worka- as-cast conditions. One of the two phases is some- bility. This allows suitable final properties to be times present but in low volumetric fraction, due to achieved. the chemical composition of the alloy, in which one An example of the changes in microstructure after of the two elements has a low concentration. various stages of work hardening and annealing is Furthermore, the thermal treatments may have shown in Figure 19 for the 60Pt-25Ir-15Rh alloy. This homogenised the alloy. Finally, the metallographic can be compared to the as-cast structure shown in preparation may not be able to reveal such biphasic Figure 6. structures. Therefore, it is necessary to use other Drawn wires show a very different microstructure analytical techniques to detect the type and along the drawing (longitudinal) direction in compar- concentration of the alloy phases. Only in specific ison to the transverse direction (Figures 20–22 for cases can the biphasic structure be revealed.

Fig. 18. Recrystallisation diagram of a platinum- rhodium alloy annealed at a set temperature for a given time after a deformation of ε %. Adapted from (10). By increasing the annealing temperature the grain size 1.6 increases. During annealing the grain size also increases if the previous deformation 1.1 1700 is reduced 1500 1300 0.6 1100 Size of grain, mm 900 0.1 700 01020 40 60 80 Annealing temperature, ºC Deformation, ε %

200 µm 500 µm 500 µm

Fig. 19. 60Pt-25Ir-15Rh alloy: from Fig. 20. Pt-5Au alloy: longitudinal Fig. 21. Pt-5Au alloy: transverse the transverse section of an ingot, section (along the drawing direction) section of the drawn cold after various stages of work hard- of a drawn cold worked wire worked wire seen in Figure 20 ening and annealing (microhardness (microhardness 190 ± 4 HV200 ) (microhardness 190 ± 4 HV200 ) 212 ± 5 HV200 ). Compare with the as-cast sample shown in Figure 6

50 µm 500 µm 50 µm

Fig. 22. Pt-5Au alloy: detail of Fig. 23. Pt-5Au alloy: transverse sec- Fig. 24. Pt-5Au alloy: detail of Figure 21 showing the deformation tion of the wire seen in Figure 21, Figure 23, showing the of the grains after oxygen-propane flame anneal- recrystallised grains ing (microhardness 104 ± 6 HV200 )

Fig. 25. Pt The best results in working platinum alloys are gen- 99.99% wire: erally achieved by hot forging the ingot during the transverse sec- first stages of the procedure. Metallography shows the tion of the wire after various differences between a material that has been cold stages of draw- worked and annealed (Figures 28 and 29 for Pt-5Cu) ing and anneal- and a material that has been hot forged (Figures 30 ing (diameter and ). Hot forging more easily achieves a homoge- 0.35 mm; 31 microhardness neous and grain-refined microstructure, free of 65 ± 3 HV100 ) defects. This is due to the dynamic recrystallisation that occurs during hot forging (26).

50 µm The Limits of Metallography Optical metallography is only the first step towards the study of the microstructure of an alloy. A wide variety of analytical techniques can be used alongside

Iridium content, wt% Gold content, at% Pt 20 40 60 80 Ir Pt 20 40 60 80 Au 1800 2454 Liquid 2200 Liquid 1600

1800 1769 α 1400 1400 α Temperature, ºC Temperature, 1200

1000 ºC Temperature, α1 α2 α1 + α2 600 1000 Pt 20 40 60 80 Ir Iridium content, at% 800 Fig. 26. Pt-Ir phase diagram showing a miscibility Pt 20 40 60 80 Au gap at low temperatures (20) Gold content, wt%

Fig. 27. Pt-Au phase diagram showing a miscibility gap at low temperature (25)

2 mm 200 µm 2 mm

Fig. 28. Pt-5Cu alloy: from a trans- Fig. 29. Pt-5Cu alloy: detail of Fig. 30. Pt-5Cu alloy: from a transverse section of a 19 mm × 19 mm Figure 28, with coarse grains and verse section of a 19 mm × 19 mm ingot, which was rod milled, small opened cracks evident bar, which was hot hammered, annealed in a furnace and finished torch annealed and finished by at 10 mm × 10 mm by drawing. The drawing. The sample has sample shows residual coarse grain homogeneous microstructure with microstructure from the as-cast small grain size (microhardness condition and fractures along the bar 200 ± 9 HV200 ). The small square axis (microhardness 208 ± 13 HV200 ). shows the position of the detail The small square shows the position seen in Figure 31 of the detail seen in Figure 29

Fig. 31. Pt-5Cu solution of sodium chloride in concentrated alloy: detail of hydrochloric acid can be successfully used for a great Figure 30, many platinum alloys, both in the as-cast condition showing recrystallised and after work hardening. Optical metallography pro- grains partially vides essential data on the alloy microstructure deformed due which can be used in setting up the working proce- to the work hardening dures. Other techniques can be used alongside it to achieve a more complete knowledge of the material, the effects of the working cycles on it, and to interpret and explain any remaining problems. 200 µm

References 1 S. Grice, ‘Know Your Defects: The Benefits of it to provide a far more complete knowledge of the Understanding Jewelry Manufacturing Problems’, in microstructure. One of the most widely used “The Santa Fe Symposium on Jewelry Manufacturing Technology 2007”, ed. E. Bell, Proceedings of the 21st techniques is SEM. In addition to this, EDS allows the Symposium in Albuquerque, New Mexico, USA, relative concentration of the contained chemical ele- 20th–23rd May, 2007, Met-Chem Research Inc, ments to be determined, as shown in Figures 8–10. Albuquerque, New Mexico, USA, 2007, pp. 173–211 Further studies can be performed by X-ray diffraction 2 P. Battaini, ‘Metallography in Jewelry Fabrication: How (XRD), which reveals the different crystal phases to Avoid Problems and Improve Quality’, in “The Santa present in the alloy. Fe Symposium on Jewelry Manufacturing Technology When working with platinum alloys, often only 2007”, ed. E. Bell, Proceedings of the 21st Symposium in Albuquerque, New Mexico, USA, 20th–23rd May, very small specimens are available, therefore more 2007, Met-Chem Research Inc, Albuquerque, New Mexico, recent techniques may be required in order to study USA, 2007, pp. 31–65 them. One of these is the focused ion beam (FIB) 3 “Failure Analysis and Prevention”, eds. R. J. Shipley and technique, which can produce microsections of a W. T. Becker, ASM Handbook, Volume 11, ASM specimen (27, 28). The microsections are then International, Ohio, USA, 2002 analysed by other techniques, such as transmission 4 G. F. Vander Voort, “Metallography: Principles and electron microscopy (TEM). In this case the details of Practice”, Material Science and Engineering Series, ASM microstructure can be detected due to the high spatial International, Ohio, USA, 1999 resolution of the technique. The crystal structure of 5 “Metallography and Microstructures”, ed. G. F. Vander the primary and secondary phases can be studied by Voort, ASM Handbook, Volume 9, ASM International, Materials Park, Ohio, USA, 2004 electron diffraction. Another interesting technique is 6 G. Petzow, “Metallographic Etching”, 2nd Edn., ASM nano-indentation, performed with micron-sized International, Ohio, USA, 1999 indenters, which allows hardness measurements to 7 T. Piotrowski and D. J. Accinno, Metallography, 1977, be performed with a spatial resolution far better than 10, (3), 243 that attainable with ordinary micro-indenters. The 8 D. Ott and U. Schindler, Gold Technol., 2001, 33, 6 data obtained from these measurements allows the 9 “Standard Practice for Microetching Metals and Alloys”, measurement of fundamental mechanical properties ASTM Standard E407, ASTM International, West of the alloy, such as the elastic modulus (Young’s Conshohocken, Pennsylvania, USA, 2007 modulus) (29). 10 E. M. Savitsky, V. P. Polyakova, N. B. Gorina and N. R. Roshan, “Physical Metallurgy of Platinum Metals”, Conclusions Metallurgiya Publishers, Moscow, Russia, 1975 (in Russian); The metallographic analysis of platinum alloys can English translation, Mir Publishers, Moscow, Russia, 1978 be profitably carried out by using a specimen prepa- 11 P. Battaini, ‘The Metallography of Platinum and Platinum ration methodology based on the techniques used for Alloys’, in “The Santa Fe Symposium on Jewelry Manufacturing Technology 2010”, ed. E. Bell, Proceedings gold-based alloys. However, electrochemical etching of the 24th Symposium in Albuquerque, New Mexico, is required in order to reveal the alloy microstructure USA, 16th–19th May, 2010, Met-Chem Research Inc, and observe it by optical microscopy. A saturated Albuquerque, New Mexico, USA, 2010, pp. 27–49

12 M. Grimwade, “Introduction to Precious Metals: 21 K. Vaithinathan and R. Lanam, ‘Features and Benefits of Metallurgy for Jewelers and Silversmiths”, Brynmorgen Different Platinum Alloys’, Technical Articles: Alloys, Press, Brunswick, Maine, USA, 2009 Platinum Guild International, USA, 2005: http://www. 13 J. Maerz, ‘Platinum Alloy Applications for Jewelry’, in platinumguild.com/output/page2414.asp (Accessed on “The Santa Fe Symposium on Jewelry Manufacturing 31 December 2010) Technology 1999”, ed. D. Schneller, Proceedings of the 22 P. Battaini, Platinum Metals Rev., 2011, 55, (1), 71 13th Symposium in Albuquerque, New Mexico, USA, 23 D. Miller, T. Keraan, P. Park-Ross, V. Husemeyer and 16th–19th May, 1999, Met-Chem Research Inc, C. Lang, Platinum Metals Rev., 2005, 49, (3), 110 Albuquerque, New Mexico, USA, 1999, pp. 55–72 24 J. C. McCloskey, ‘Microsegregation in Pt-Co and Pt-Ru 14 J. Huckle, ‘The Development of Platinum Alloys to Jewelry Alloys’, in “The Santa Fe Symposium on Jewelry Overcome Production Problems’, in “The Santa Fe Manufacturing Technology 2006”, ed. E. Bell, Symposium on Jewelry Manufacturing Technology 1996”, Proceedings of the 20th Symposium in Nashville, ed. D. Schneller, Proceedings of the 10th Symposium in Tennessee, USA, 10th–13th September, 2006, Met- Albuquerque, New Mexico, USA, 19th–22nd May, 1996, Chem Research Inc, Albuquerque, New Mexico, USA, Met-Chem Research Inc, Albuquerque, New Mexico, 2006, pp. 363–376 USA, 1996, pp. 301–326 25 “Smithells Metals Reference Book”, 7th Edn., eds. E. A. 15 D. P. Agarwal and G. Raykhtsaum, ‘Manufacturing of Brandes and G. B. Brook, Butterworth-Heinemann, Ltd, Lightweight Platinum Jewelry and Findings’, in “The Oxford, UK, 1992 Santa Fe Symposium on Jewelry Manufacturing 26 R. W. Cahn, ‘Recovery and Recrystallization’, in Technology 1996”, ed. D. Schneller, Proceedings of the “Physical Metallurgy”, eds. R. W. Cahn and P. Haasen, 10th Symposium in Albuquerque, New Mexico, USA, Elsevier Science BV, Amsterdam, The Netherlands, 1996 19th–22nd May, 1996, Met-Chem Research Inc, 27 P. R. Munroe, Mater. Charact., 2009, 60, (1), 2 Albuquerque, New Mexico, USA, 1996, pp. 373–382 28 E. Bemporad, ‘Focused Ion Beam and Nano-Mechanical 16 J. Maerz, ‘Platinum Alloys: Features and Benefits’, in Tests for High Resolution Surface Characterization: Not “The Santa Fe Symposium on Jewelry Manufacturing So Far Away From Jewelry Manufacturing’, in “The Santa Technology 2005”, ed. E. Bell, Proceedings of the 19th Fe Symposium on Jewelry Manufacturing Technology Symposium in Albuquerque, New Mexico, USA, 2010”, ed. E. Bell, Proceedings of the 24th Symposium 22nd–25th May, 2005, Met-Chem Research Inc, in Albuquerque, New Mexico, USA, 16th–19th May, Albuquerque, New Mexico, USA, 2005, pp. 303–312 2010, Met-Chem Research Inc, Albuquerque, New 17 R. Lanam, F. Pozarnik and C. Volpe, ‘Platinum Alloy Mexico, USA, 2010, pp. 50–78 Characteristics: A Comparison of Existing Platinum 29 D. J. Shuman, A. L. M. Costa and M. S. Andrade, Mater. Casting Alloys with Pt-Cu-Co’, Technical Articles: Alloys, Charact., 2007, 58, (4), 380 Platinum Guild International, USA, 1997: http://www. platinumguild.com/output/page2414.asp (Accessed on 31 December 2010) The Author 18 G. Normandeau and D. Ueno, ‘Platinum Alloy Design for Paolo Battaini holds a degree in nuclear the Investment Casting Process’, Technical Articles: Alloys, engineering and is a consultant in failure analysis for a range of industrial Platinum Guild International, USA, 2002: http://www. fields. He is responsible for research platinumguild.com/output/page2414.asp (Accessed on and development at 8853 SpA in 31 December 2010) Milan, Italy, a factory producing dental alloys and semi-finished products in 19 R. F. Vines and E. M. Wise, “The Platinum Metals and gold, platinum and palladium alloys, Their Alloys”, The International Nickel Company, Inc, and is currently a professor of precious New York, USA, 1941 metal working technologies at the University of Milano-Bicocca, Italy. 20 “Handbook of Precious Metals”, ed. E. M. Savitsky, Professor Battaini is also a recipient of ® Metallurgiya Publishers, Moscow, Russia, 1984 (in the Santa Fe Symposium Ambassador Award and regularly presents at the Russian); English translation, Hemisphere Publishing Santa Fe Symposium® on Jewelry Corp, New York, USA, 1989 Manufacturing Technology.

The 2010 Nobel Prize in Chemistry: Palladium-Catalysed Cross-Coupling The importance of carbon–carbon coupling for real world applications

doi:10.1595/147106711X558301 http://www.platinummetalsreview.com/

By Thomas J. Colacot The 2010 Nobel Prize in Chemistry was awarded jointly to Professor Richard F. Heck (University of Delaware, Johnson Matthey, Catalysis and Chiral Technologies, 2001 Nolte Drive, West Deptford, New Jersey 08066, USA), Professor Ei-ichi Negishi (Purdue University, USA; USA) and Professor Akira Suzuki (Hokkaido University, E-mmail: [email protected] Japan) for their work on palladium-catalysed cross- coupling in organic synthesis. This article presents a brief history of the development of the protocols for palladium-catalysed coupling in the context of Heck, Negishi and Suzuki coupling. Further developments in the area of palladium-catalysed cross-coupling are also briefly discussed, and the importance of these reactions for real world applications is highlighted.

The 2010 Nobel Prize in chemistry was the third awarded during the last ten years in the area of platinum group metal (pgm)-based homogeneous catalysis for organic synthesis. Previous prizes had been awarded to Dr William S. Knowles (Monsanto, USA), Professor Ryoji Noyori (Nagoya University,Japan) and Professor K. Barry Sharpless (The Scripps Research Institute, USA) in 2001, for their development of asymmetric synthesis reactions catalysed by rhodium, ruthenium and osmium complexes, and to Dr Yves Chauvin (Institut Français du Pétrole, France), Professor Robert H. Grubbs (California Institute of Technology (Caltech), USA) and Professor Richard R. Schrock (Massachusetts Institute of Technology (MIT), USA) in 2005 for the development of the ruthenium- and molybdenum-catalysed olefin metathesis method in organic synthesis. Figure 1 shows some of the researchers who have made significant contributions in the area of palladium-catalysed cross-coupling, including 2010 Nobel laureate, Professor Akira Suzuki, during a cross- coupling conference at the University of Lyon, France, in 2007 (1).

Palladium-Catalysed Reactions Organometallic compounds of pgms are vitally important as catalysts for real world applications in

Fig. 1. From left: Professor Kohei Tamao (a significant contributor in Kumada coupling), Professor Gregory C. Fu (a significant contributor in promoting the bulky electron-rich tert-butyl phosphine for challenging cross-coupling), Professor Akira Suzuki (2010 Nobel Prize in Chemistry Laureate), Dr Thomas J. Colacot (author of this article) and Professor Tamejiro Hiyama (who first reported Hiyama coupling) in front of a photograph of Professor Victor Grignard (who initiated the new method of carbon–carbon coupling) in the library of the University of Lyon, France synthetic organic chemistry. Chemists are continually coupling is smaller in terms of the number of pub- striving to improve the efficiency of industrial lications, but its popularity is growing due to the processes by maximising their yield, selectivity and functional group tolerance of the zinc reagent in safety. Process economics are also important, and comparison to magnesium, in addition to its signifi- chemists work to minimise the number of steps cant potential in sp3–sp2 coupling, natural product required and thereby reduce the potential for waste synthesis and asymmetric carbon–carbon bond form- and improve the sustainability of the process. ing reactions (1). Homogeneous catalysis is a powerful tool which can The history and development of the various types help to achieve these goals. Of the three Nobel Prizes of palladium-catalysed coupling reactions have been in pgm-based homogeneous catalysis, perhaps the covered in detail elsewhere (3, 4). This short article most impact in practical terms has been made by will focus on the practical applications of palladium- palladium-catalysed cross-coupling (2). catalysed coupling reactions. In order for an area to be recognised for the Nobel Prize, its real world application has to be demon- Heck Coupling strated within 20 to 30 years of its discovery. Although Between 1968 and the area of metal-catalysed cross-coupling was initi- 1972, Mizoroki and ated in the early 1970s, there were a very limited num- coworkers (5, 6) and ber of publications and patents in this area before the Heck and coworkers 1990s (see Figure 2). However, the area has grown (7–9) independently rapidly from 1990 onwards, especially since 2000. discovered the use of In terms of the number of scientific publications, Pd(0) catalysts for patents and industrial applications, Suzuki coupling coupling of aryl, ben- is by far the largest area, followed by Heck, zyl and styryl halides

8000 Suzuki 7000 Heck Sonogashira 6000 Stille 5000 Negishi Buchwald-Hartwig 4000 Kumada Hiyama

and patents 3000 Alpha ketone arylation 2000

Total number of publications Total 1000 0 Pre-1990 1991–2000 2001–2010 Decades

Fig. 2. Growth in the number of scientific publications and patents on platinum group metal-catalysed coupling reactions

Scheme I. The Heck coupling reaction R’ H Pd catalyst R’ H RX + H H Base H R R, R’ = aryl, vinyl, alkyl X = halide, triflate, etc.

pounds, now known as the Heck coupling reaction The Negishi Reaction (Scheme I) as Heck was the first to uncover the mech- During 1976–1977, anism of the reaction. Negishi and co- The applications of this chemistry include the syn- workers (10–12) and thesis of hydrocarbons, conducting polymers, light- Fauvarque and Jutand emitting electrodes, active pharmaceutical ingredi- (13) reported the use ents and dyes. It can also be used for the enantio- of zinc reagents in selective synthesis of natural products. cross-coupling reac- Heck coupling has a broader range of uses than the tions.During the same other coupling reactions as it can produce products period Kumada et al.

of different regio (linear and branched) and stereo Copyright © The Nobel Foundation. Photo: Ulla Montan (14–17) and Corriu (cis and trans) isomers. Typically, olefins possessing et al. (18) independ- electron-withdrawing groups favour linear products ently reported that nickel–phosphine complexes while electron-rich groups give a mixture of branched were able to catalyse the coupling of aryl and alkenyl and linear products.The selectivity is also influenced halides with Grignard reagents. Kumada and cowork- by the nature of ligands, halides, additives and sol- ers later reported (in 1979) the use of dichloro[1,1′- vents, and by the nature of the palladium source.The bis(diphenylphosphino)ferrocene]palladium(II) reaction has recently been extended to include direct (PdCl2(dppf)) as an effective catalyst for the cross- arylation and hydroarylation, which may have future coupling of secondary alkyl Grignard reagents with potential in terms of practical applications. Heck cou- organic halides (19).One common limitation to both pling also has the unique advantage of making chiral Ni- and Pd-catalysed Kumada coupling is that cou- C–C bonds,with the exception of α-arylation reactions. pling partners bearing base sensitive functionalities

are not tolerated due to the nature of the organomag- nesium reagents. Pd catalyst RBZ2 + R’X R–R’ In 1982 Negishi and coworkers therefore carried out Base a metal screening in order to identify other possible R, R’ = aryl, vinyl, alkyl organometallic reagents as coupling partners (20). X = halide, triflate, etc. Several metals were screened in the coupling of an Z = OH, OR, etc. aryl iodide with an acetylene organometallic reagent, catalysed by bis(triphenylphosphine)palladium(II) Scheme III. The Suzuki coupling reaction dichloride (PdCl2(PPh3)2). In this study, the use of zinc, boron and tin were identified as viable counter- It should be noted that Heck had already demon- cations, and provided the desired alkyne product in strated in 1975 the transmetallation of a vinyl boronic good yields. The use of organozinc reagents as cou- acid reagent (30). Perhaps the greatest acomplish- pling partners for palladium-catalysed cross-coupling ment of Suzuki was that he identified PdCl2(PPh3)2 as to form a C–C single bond is now known as the an efficient cross-coupling catalyst, thereby demon- Negishi reaction (Scheme II). strating the relatively easy reduction of Pd(II) to Pd(0) during catalysis. The Suzuki coupling reaction is widely used in Pd catalyst RZnY + R’X R–R’ the synthesis of pharmaceutical ingredients such as losartan. Its use has been extended to include R, R’ = aryl, vinyl, alkyl coupling with alkyl groups and aryl chlorides X = halide, triflate, etc. through the work of other groups including Fu and Y = halide coworkers (31). Subsequent work from Buchwald, Scheme II. The Negishi coupling reaction Hartwig, Nolan, Beller and others, including Johnson Matthey,has expanded the scope of this reaction. The Negishi reaction has been used as an essential step in the synthesis of natural products and fine Other Name Reactions in Carbon–Carbon chemicals (21–23). Coupling In 1976, Eaborn et al. published the first palladium- Suzuki Coupling catalysed reaction of organotin reagents (32), fol- During the same lowed by Kosugi et al. in 1977 on the use of organotin period as the initial reagents (33,34). Stille and Milstein disclosed in 1978 reports of the use of the synthesis of ketones (27) under significantly palladium–phosphine milder reaction conditions than Kosugi. At the begin- complexes in Kumada ning of the 1980s, Stille further explored and improved couplings, the palla- this reaction protocol, to develop it into a highly ver- dium-catalysed cou- satile methodology displaying very broad functional pling of acetylenes group compatibility (28). with aryl or vinyl In 1988, Hiyama and Hatanaka published their work

Copyright © The Nobel Foundation. Photo: Ulla Montan halides was concur- on the Pd- or Ni-catalysed coupling of organosilanes rently disclosed by with aryl halides or trifluoromethanesulfonates (tri- three independent research groups, led by flates) (35). Although silicon is less toxic than tin, Sonogashira (24), Cassar (25) and Heck (26). a fluoride source, such as tris(dimethylamino)- A year after the seminal report on the Stille cou- sulfonium difluorotrimethylsilicate (TASF) (35) or cae- pling (27, 28), Suzuki picked up on boron as the last sium fluoride (CsF) (36), is required to activate the remaining element out of the three (Zn, Sn and B) organosilane towards transmetallation. Professor S. E. identified by Negishi as suitable countercations in Denmark has also contributed significantly to this area. cross-coupling reactions, and reported the palladium- catalysed coupling between 1-alkenylboranes and Industrial Applications aryl halides (29) that is now known as Suzuki cou- In the early 1990s the Merck Corporation was able to pling (Scheme III). develop two significant drug molecules, losartan, 1,

1 Losartan 2 Montelukast

Fig. 3. Structures of losartan and montelukast

(also known as CozaarTM, for the treatment of hyper- diode (OLED) applications in display screens (42, tension) (37) and montelukast, 2, (also known as 43). SingulairTM, for the treatment of asthma) (38, 39), The research and development group at Johnson (Figure 3) using Suzuki and Heck coupling processes Matthey’s Catalysis and Chiral Technologies has devel- respectively. This also increased awareness among oped commercial processes for preformed catalysts related industries to look into similar processes. such as PdCl2(dtbpf) (Pd-118), 3, (44–46), L2Pd(0) Today, coupling reactions are essential steps in the complexes, 4, (47) and precursors to twelve-electron t preparation of many drugs. Recent reviews by Beller species such as [Pd(µ-Br) Bu3P]2 (Pd-113), 5, (48) (40) and by Sigman (41) summarise the applications and LPd(η3-allyl)Cl, 6, (49, 50) (Figure 4). These cata- of Pd-catalysed coupling in the pharmaceutical,agro- lysts are all highly active for various cross-coupling chemical and fine chemicals industries. Apart from reactions which are used for real world applications. the major applications in the pharmaceutical and More details on the applications of these catalysts agrochemical industries (the boscalid process is the are given elsewhere (48, 51, 52). A special issue of world’s largest commercial Suzuki process), cross- Accounts of Chemical Research also covered recent coupling is also being practiced in the electronics updates of these coupling reactions from academia industry for liquid crystal and organic light-emitting in detail (53).

PtBu 2 Cl Br t t Pd LLPd Bu3P–Pd Pd–P Bu3 Fe P Br Cl 4 t Pd P Bu2 5 3 Cl 6 t P Bu2 t 4a L = P Bu3 t t P Bu2 4b L = P Bu2Np Ph Fe Ph 4c L = PCy3 4d L = Q-Phos Ph Ph 4e L = Ata-Phos Me2N 4f L = P(o-tolyl)3 t Ph 4g L = PPh Bu2 Ata-Phos ligand Q-Phos ligand

Fig. 4. Examples of highly active Pd cross-coupling catalysts developed and commercialised by Johnson Matthey

In order to address the issue of residual palladium ticularly important for developing compounds con- in the final product, several solid-supported taining carbon–nitrogen bonds for applications in preformed palladium complexes have been devel- industry, as well as α-arylation of carbonyl com- oped and launched onto the catalyst market pounds such as ketones, esters, amides, aldehydes (54–56). etc., and nitriles (57). The significant growth of cross- coupling reactions can be summarised in Professor Conclusions K. C. Nicolaou’s words: Palladium-catalysed cross-coupling is of great impor- “In the last quarter of the 20th century, a new tance to real world applications in the pharmaceu- paradigm for carbon–carbon bond formation has tical, agrochemicals, fine chemicals and electronics emerged that has enabled considerably the prowess industries. The area has developed quite rapidly of synthetic organic chemists to assemble complex beyond the work of Heck, Negishi and Suzuki, molecular frameworks and has changed the way though all three reactions are widely used. Academic we think about synthesis”(58). groups such as those of Beller, Buchwald, Fu, Hartwig More detailed articles summarising the history of and Nolan as well as industrial groups such as that cross-coupling in the context of the 2010 Nobel Prize at Johnson Matthey,are now developing the field even in Chemistry with an outlook on the future of cross- further. Buchwald-Hartwig coupling has become par- coupling will be published elsewhere (59, 60).

Glossary Ligand Name Ata-Phos p-dimethylaminophenyl(di-tert-butyl)phosphine Cy cyclohexyl dppf 1,1′-bis(diphenylphosphino)ferrocene dtbpf 1,1′-bis(di-tert-butylphosphino)ferrocene Np neopentyl Ph phenyl Q-Phos 1,2,3,4,5-pentaphenyl-1′-(di-tert-butylphosphino)ferrocene tBu tert-butyl

References 1 T. Colacot, Platinum Metals Rev., 2008, 52, (3), 172 10 E. Negishi and S. Baba, J. Chem. Soc., Chem. Commun., 2 “Metal-Catalyzed Cross-Coupling Reactions”, 2nd Edn., 1976, (15), 596b eds. A. de Meijere and F. Diederich, Wiley-VCH, 11 E. Negishi, A. O. King and N. Okukado, J. Org. Chem., Weinheim, Germany, 2004 1977, 42, (10), 1821 3 C. Barnard, Platinum Metals Rev., 2008, 52, (1), 38 12 A. O. King, N. Okukado and E. Negishi, J. Chem. Soc., 4 ‘Scientific Background on the Nobel Prize in Chemistry Chem. Commun., 1977, (19), 683 2010: Palladium-Catalyzed Cross Couplings in Organic 13 J. F. Fauvarque and A. Jutand, J. Organomet. Chem., Synthesis’, The Royal Swedish Academy of Sciences, 1977, 132, (2), C17 Stockholm, Sweden, 6th October, 2010: http:// 14 K. Tamao, K. Sumitani, Y. Kiso, M. Zembayashi, A. Fujioka, nobelprize.org/nobel_prizes/chemistry/laureates/2010/sci. S. Kodama, I. Nakajima, A. Minato and M. Kumada, Bull. html (Accessed on 24 January 2011) Chem. Soc. Jpn., 1976, 49, (7), 1958 5 T. Mizoroki, K. Mori and A. Ozaki, Bull. Chem. Soc. Jpn., 15 K. Tamao, Y. Kiso, K. Sumitani and M. Kumada, J. Am. 1971, 44, (2), 581 Chem. Soc., 1972, 94, (26), 9268 6 K. Mori, T. Mizoroki and A. Ozaki, Bull. Chem. Soc. Jpn., 16 K. Tamao, K. Sumitani and M. Kumada, J. Am. Chem. 1973, 46, (5), 1505 Soc., 1972, 94, (12), 4374 7 R. F. Heck, J. Am. Chem. Soc., 1968, 90, (20), 5518 17 M. Kumada, in “Organotransition Metal Chemistry”, eds. 8 R. F. Heck and J. P. Nolley, J. Org. Chem., 1972, 37, Y. Ishii and M. Tsutsui, Plenum Press, New York, USA, (14), 2320 1975, p. 211 9 H. A. Dieck and R. F. Heck, J. Am. Chem. Soc., 1974, 18 R. J. P. Corriu and J. P. Masse, J. Chem. Soc., Chem. 96, (4), 1133 Commun., 1972, (3), 144a

19 T. Hayashi, M. Konishi and M. Kumada, Tetrahedron 46 T. J. Colacot and H. A. Shea, Org Lett., 2004, 6, (21), Lett., 1979, 20, (21), 1871 3731 20 E. Negishi, Acc. Chem. Res., 1982, 15, (11), 340 47 H. Li, G. A. Grasa and T. J. Colacot, Org. Lett., 2010, 12, 21 S. Hirashima, S. Aoyagi and C. Kibayashi, J. Am. Chem. (15), 3332 Soc., 1999, 121, (42), 9873 48 T. J. Colacot, Platinum Metals Rev., 2009, 53, 22 P. Wipf and S. Lim, J. Am. Chem. Soc., 1995, 117, (1), (4), 183 558 49 L. L. Hill, J. L. Crowell, S. L. Tutwiler, N. L. Massie, C. C. Hines, 23 B. A. Anderson, L. M. Becke, R. N. Booher, M. E. Flaugh, S. T. Griffin, R. D. Rogers, K. H. Shaughnessy, G. A. Grasa, N. K. Harn, T. J. Kress, D. L. Varie and J. P. Wepsiec, C. C. C. Johansson Seechurn, H. Li, T. J. Colacot, J. Chou and J. Org. Chem., 1997, 62, (25), 8634 C. J. Woltermann, J. Org. Chem., 2010, 75, (19), 6477 24 K. Sonogashira, Y. Tohda and N. Hagihara, Tetrahedron 50 L. L. Hill, L. R. Moore, R. Huang, R. Craciun, A. J. Vincent, Lett., 1975, 16, (50), 4467 D. A. Dixon, J. Chou, C. J. Woltermann and K. H. Shaughnessy, J. Org. Chem., 2006, 71, (14), 5117 25 L. Cassar, J. Organomet. Chem., 1975, 93, (2), 253 51 T. J. Colacot and S. Parisel, ‘Synthesis, Coordination 26 H. A. Dieck and F. R. Heck, J. Organomet. Chem., 1975, Chemistry and Catalytic Use of dppf Analogs’, in 93, (2), 259 “Ferrocenes: Ligands, Materials and Biomolecules”, ed. 27 D. Milstein and J. K. Stille, J. Am. Chem. Soc., 1978, P. Stepnicka, John Wiley & Sons, New York, USA, 2008 100, (11), 3636 52 T. J. Colacot, ‘Dichloro[1,1’-bis(di-tert-butylphosphino)- 28 J. K. Stille, Angew. Chem. Int. Ed., 1986, 25, (6), 508 ferrocene]palladium(II)’, in “e-EROS Encyclopedia of 29 N. Miyaura and A. Suzuki, J. Chem. Soc., Chem. Commun., Reagents for Organic Synthesis”, eds. L. A. Paquette, 1979, (19), 866 D. Crich, P. L. Fuchs and G. Molander, John Wiley & Sons, 30 H. A. Dieck and F. R. Heck, J. Org. Chem., 1975, 40, (8), published online 2009 1083 53 Cross-Coupling Special Issue, Acc. Chem. Res., 2008, 41, 31 A. F. Littke and G. C. Fu, Angew. Chem. Int. Ed., 1998, (11), 1439–1564 37, (24), 3387 54 T. J. Colacot, W. A. Carole, B. A. Neide and A. Harad, 32 D. Azarian, S. S. Dua, C. Eaborn and D. R. M. Walton, Organometallics, 2008, 27, (21), 5605 J. Organomet. Chem., 1976, 117, (3), C55 55 T. J. Colacot, ‘FibreCat’, in “e-EROS Encyclopedia of 33 M. Kosugi, K. Sasazawa, Y. Shimizu and T. Migita, Chem. Reagents for Organic Synthesis”, eds. L. A. Paquette, Lett., 1977, 6, (3), 301 D. Crich, P. L. Fuchs and G. Molander, John Wiley & Sons, published online 2009 34 M. Kosugi, Y. Shimizu and T. Migita, Chem. Lett., 1977, 6, (12), 1423 56 W. Carole and T. J. Colacot, Chim. Oggi-Chem. Today, May/June 2010, 28, (3) 35 Y. Hatanaka and T. Hiyama, J. Org. Chem., 1988, 53, (4), 918 57 C. C. C. Johansson Seechurn and T. J. Colacot, Angew. Chem. Int. Ed., 2010, 49, (4), 676 36 N. A. Strotman, S. Sommer and G. C. Fu, Angew. Chem. Int. Ed., 2007, 46, (19), 3556 58 K. C. Nicolaou, P. G. Bulger and D. Sarlah, Angew. Chem. Int. Ed., 2005, 44, (29), 4442 37 R. D. Larsen, A. O. King, C. Y. Chen, E. G. Corley, B. S. Foster, F. E. Roberts, C. Yang, D. R. Lieberman and R. A. 59 C. C. C. Johansson Seechurn, T. J. Colacot, M. Kitching Reamer, J. Org. Chem., 1994, 59, (21), 6391 and V. Snieckus, Angew. Chem. Int. Ed., manuscript under preparation 38 A. O. King, E. G. Corley, R. K. Anderson, R. D. Larsen, T. R. Verhoeven, P. J. Reider, Y. B. Xiang, M. Belley and 60 H. Li, T. J. Colacot and V. Snieckus, ACS Catal., manuscript Y. Leblanc, J. Org. Chem., 1993, 58, (14), 3731 under preparation 39 R. D. Larsen, E. G. Corley, A. O. King, J. D. Carroll, P. Davis, T. R. Verhoeven, P. J. Reider, M. Labelle, J. Y. Gauthier, Y. B. Xiang and R. J. Zamboni, J. Org. Chem., 1996, 61, (10), The Author 3398 Dr Thomas J. Colacot, FRSC, is a 40 C. Torborg and M. Beller, Adv. Synth. Catal., 2009, 351, Research and Development Manager in Homogeneous Catalysis (Global) of (18), 3027 Johnson Matthey’s Catalysis and 41 R. Jana, T. P. Pathak and M. S. Sigman, Chem. Rev., Chiral Technologies business unit. 2011, 111, (3), 1417 Since 2003 his responsibilities include developing and managing a new cat- 42 X. Zhan, S. Barlow and S. R. Marder, Chem. Commun., alyst development programme, cat- 2009, (15), 1948 and references therein alytic organic chemistry processes, 43 H. Jung, H. Hwang, K.-M. Park, J. Kim, D.-H. Kim and scale up, customer presentations and technology transfers of processes Y. Kang, Organometallics, 2010, 29, (12), 2715 globally. He is a member of Platinum 44 G. A. Grasa and T. J. Colacot, Org. Process Res. Dev., Metals Review’s Editorial Board, 2008, 12, (3), 522 among other responsibilities. He has co-authored about 100 publications 45 G. A. Grasa and T. J. Colacot, Org. Lett., 2007, 9, (26), and holds several patents. 5489

Dalton Discussion 12: Catalytic C–H and C–X Bond Activation

doi:10.1595/147106711X554071 http://www.platinummetalsreview.com/

Reviewed by Ian J. S. Fairlamb The 12th Dalton Discussion (DD12) conference was Department of Chemistry, University of York, Heslington, held at Durham University, UK, from 13th–15th York YO10 5DD, UK; September 2010 (1). It was the first Dalton Discussion E-mmail: [email protected] to have been jointly organised by the Dalton and Organic Divisions of the Royal Society of Chemistry (RSC). A special issue of Dalton Transactions,containing refereed papers (both original and perspective articles), accompanied all the presentations at the conference (2).The DD12 meeting was supported by generous sponsorship from BP, Pfizer and the Dalton and Organic Divisions of the RSC, and poster prizes were provided by Springer, Dalton Transactions and Catalysis Science and Technology. The principal aim of DD12 was to bring together both organic and inorganic chemists from around the world to highlight and discuss important aspects relevant to the design, development and application of late transition metal-catalysed protocols involving the activation of either carbon–X (X = halogen or pseudohalogen) or carbon–hydrogen bonds. The investigation of mechanism and synthetic applications of catalytic processes by both experimental and theoretical methods underpinned many of the oral and poster contributions at the conference. Common themes discussed at DD12 included: • Ligand design and kinetic studies of catalytic processes involving C–H and C–X activation; • New opportunities in C–X activation; • Fundamental experimental aspects of C–X and C–H activation; • Mechanistic and theoretical aspects of C–X and C–H activation. It was quite fortuitous that DD12 occurred just a few weeks prior to the announcement on 6th October 2010 that the Nobel Prize in Chemistry 2010 would be awarded to Professors Richard F.Heck, Ei-ichi Negishi and Akira Suzuki for work in the field of palladium- catalysed cross-coupling reactions in organic synthesis (3), which highlights the general importance and timeliness of the topic. Over one hundred delegates attended DD12 from across Europe, Asia, the Middle East and North America. Both academic and industrial groups were

represented at the conference, with around 25% of modified Ullmann reaction, highlighting the impor- attendees being from major industrial organisations. tance of copper(III) species, but also issues surround- The DD12 meeting comprised eight single sessions ing the complex catalytic reaction systems. run over three days. Individual sessions began with A careful study of manganese-catalysed C–H oxi- either a Keynote lecture or an invited lecture. These dation with hydrogen peroxide showed that spe- were followed by three five-minute contributed pre- cially designed multidentate ligands were oxidised to sentations. With the exception of the sixth session pyridine-2-carboxylic acid prior to catalytic substrate (see below), questions were taken during the lively oxidation, which explains the observed catalytic and lengthy discussions held after all of the session activity (Scheme I). This work by Wesley R. Browne lectures had taken place. (University of Groningen, The Netherlands) showed that some caution should be exerted in ligand design, Ligand Design metal catalysis and reaction mechanism analysis, Professor Todd Marder (Durham University, UK) especially where the ligand can change chemical chaired the first session of the meeting. Professor form under the catalytic reaction conditions used. Hans de Vries (DSM Pharmaceutical Products, The Netherlands) gave the Keynote lecture, which pro- Selective Catalysis vided an overview of cross-coupling reactions and The second session was chaired by Warren B. Cross issues of ‘ligand design’ versus ‘ligand-free’ catalysis. (University of Leicester, UK) who introduced a His lecture nicely set the tone of the meeting and Keynote lecture from Professor Aiwen Lei (Wuhan stimulated lots of discussion; for example, on the University, China). Professor Lei discussed selective nature of the catalytically active species and the oxidative cross-coupling using palladium(II) catalysis role of palladium nanoparticles. Professor de Vries (with a suitable oxidant) between two different then went on to present several mechanisms for the nucleophiles (for example Process A, Scheme II) and

N N N N CO2H Mn/H2O2 Mn/H2O2 Active N N Ligand oxidation catalyst OH species HO

Scheme I. Ligand degradation in a manganese-catalysed oxidation process

Scheme II. M New catalytic Process A R1 cross-coupling processes with activated or 1 or: R unactivated arenes X H Pd catalyst Process B R1 + R2

or: R2 H Process C R1

M = metal X = halogen or pseudohalogen

went on to elaborate on issues surrounding the rates functionalisation of secondary methylene carbon of reductive elimination processes. Crucially, fast centres in the presence of other secondary sites was reductive elimination and transmetallation rates were a particular highlight. found to determine the selectivity of the hetero- During the discussion session of these lectures, coupling reaction. several of the pharmaceutical chemists present at the George Fortman (University of St Andrews, UK) meeting debated the role of fluoroaryl groups in discussed work on the synthesis of gold–acetylides pharmaceutical compounds. Several viable synthetic formed by alkyne C–H activation. The serendipitous methods for incorporating fluoro substituents into discovery of a palladium-catalysed regioselective arenes were highlighted. C–H functionalisation of 2-pyrones was then reported by Professor Fairlamb.Two catalysts were used in this Mechanistic Aspects work,namely trans-Pd(Br)N-Succ(PPh3)2 and Pd2(dba- The fourth session of DD12 was chaired by Professor 4-OMe)3 (N-Succ = succinimide; dba-4-OMe = 1,5-bis- Susan Gibson (Imperial College London, UK), and (4′-methoxyphenyl)penta-1E,4E-dien-3-one). began with an invited lecture by John M. Brown The third session of the meeting was chaired by (Oxford University, UK). Brown introduced anilide Professor Fairlamb, and began with a Keynote lecture activation of adjacent C–H bonds in the palladium- by Professor Jennifer Love (The University of British catalysed Fujiwara-Moritani reaction using catalytic

Columbia, Canada). Love presented a brief overview Pd(OAc)2 in the presence of tosic acid and p-benzo- of carbon–fluorine activation processes including quinone. Kinetic aspects such as induction periods cross-coupling reactions of polyfluoroarenes. She and palladacycle formation were presented as well as focused on the development of nickel and platinum synthetic aspects. During the discussion session a catalyst systems for arylboronic acid cross-coupling number of mechanistic aspects of these processes with fluoroarenes containing ortho-directing groups. were raised, which led to David (Dai) Davies This presentation was followed by Professor Philippe (University of Leicester, UK) defining the ambiphilic Dauban (Centre National de la Recherche metal ligand activation (AMLA) process in which the Scientifique (CNRS), France), who presented studies number of atoms thought to be involved in the transi- of catalytic aminations involving nitrene insertion tion state is specified, as illustrated in Scheme IV for into C–H bonds (Scheme III). The selective C–H AMLA-4 (4 electrons) and AMLA-6 (6 electrons)

Scheme III. Selective Rh* NHS(S) carbon–hydrogen (S) Yield ≤91% activation-catalytic S NH2 + Iodine(III) R’ amination using R de ≤99% Concerted rhodium catalysis or stepwise? Iodine(I) H Rh*=NS(S) R’ R Terpenes or polycyclic systems

O (S) S NH2 = Rh* = S NH2 O N SO2-p-Tol N

O O O Rh2((S)-nta)4 nta = nitrilotriacetate Rh Rh

intermediates which are of general relevance to C–H Dai Davies went on to present alkyne insertion activation. The concerted metalation-deprotonation reactions of cyclometallated pyrazole and imine (CMD) is identical to AMLA-6. complexes of iridium, rhodium and ruthenium, with Esteban P. Urriolabeitia (University of Zaragoza, emphasis on establishing substrate/catalyst/product Spain) reported stoichiometric and catalytic correlations through detailed structural and spectro- regioselective C–H functionalisations including a scopic studies. The last speaker of the session, Xavi palladium-catalysed oxidative etherification of imino- Ribas (Universitat de Girona, Spain), discussed reduc- phosphoranes. Finally, a combined theoretical and tive elimination from a ‘model’ aryl–Cu(III)–halide experimental study on the use of ruthenium vinyli- species which was triggered by a strong acid, and its dene complexes as catalysts for carbon–oxygen bond relevance to the mechanism of Ullmann-type cou- formation was presented by Jason M. Lynam plings (Scheme VI). (University of York, UK). The role of carboxylate ‘acetate’ ligands was discussed, and a variant of the C–H Activation AMLA/CMD mechanism proposed, namely the ligand- The sixth session was chaired by Professor Peter assisted-proton shuttle (LAPS) (Scheme V). Scott (The University of Warwick, UK), and the first The fifth session was chaired by Anthony Haynes invited lecture was from Professor Robin Bedford (The University of Sheffield, UK). Professor Zhang-Jie (University of Bristol, UK). Bedford presented an Shi (Peking University, China) gave an interesting introduction to the field of ‘C–H activation’, and went presentation, particularly the unusual results of a on to discuss mild and selective ‘solvent-free’ aro- ‘metal-free’ coupling of an aryl halide with an arene matic C–H functionalisation/halogenation reactions using potassium tert-butoxide and 1,10-phenanthro- catalysed by Pd(OAc)2. The second lecture was line (4). given by Professor Fairlamb on surface-catalysed

Scheme IV. Alkenylation H H Pd(OAc) , p-TsOH, butyl chemistry (top); ambiphilic N 2 N metal ligand activation acrylate, p-benzoquinone O O (AMLA) and concerted metalation-deprotonation (CMD) mechanisms for carbon–hydrogen activation CO Bu 2 (bottom)

Oxidative σ-Bond Ambiphilic metal ligand activation addition metathesis (AMLA)

R’ + R’ + X + R’ + O LnM LnM LnM H H H LnM O R R R RH AMLA-4 AMLA-6*

R’ = H, hydrocarbyl, boryl *AMLA-6 is essentially identical to X = heteroatom with lone pair(s) concerted metalation deprotonation (CMD)

Scheme V. Ligand- R Ru R [Ru] R assisted-proton O O [Ru] C shuttle (LAPS) mechanism H H O H O O O 2 [Ru]=Ru(κ -OAc)(PPh3)2

+ X

CF3SO3H (1.5 equiv), CH3CN, 298 K, <1 h III I + H N Cu N H H N X N H + [Cu (CH3CN)4] ( ) ( ) ( ) + ( ) 3 N 3 3 N 3 – – CH3 X = Cl or Br H3C H CF3SO3 (TFO )

Scheme VI. Aryl–X reductive elimination from an aryl–Cu(III)–X species via protonation with triflic acid

Suzuki-Miyaura cross-coupling over palladium nano- William D. Jones (University of Rochester, USA). particles stabilised by polyvinylpyrrolidinone (PVP). Professor Jones discussed various kinetic and ther- This work, in collaboration with Professor Adam Lee, modynamic aspects of C–H bond activation by transi- gave details about the reaction mechanism, including tion metals. A key focus of the lecture was placed on results from kinetic studies, X-ray photoelectron spec- the ortho-fluorine effect by drawing on both rhodium– troscopy (XPS) and X-ray absorption spectroscopy carbon and carbon–hydrogen bond energy correla- (XAS), of a heterogeneous surface-catalysed Suzuki tions in a series of fluorinated aromatic hydrocarbons cross-coupling (Figure 1). Extended X-ray absorption (Figure 2). Professor Robin Perutz (University of fine structure (EXAFS) measurements proved particu- York, UK) delivered a presentation on studies in col- larly informative in showing that palladium nanopar- laboration with Professor Odile Eisenstein (Université ticles do not change size in a typical Suzuki-Miyaura Montpellier II, France), discussing the effect of ortho- cross-coupling. Finally, Professor Yoshiaki Nakao fluorine substituents on Pd/C catalysed C–C bond (Kyoto University,Japan) presented a nickel-catalysed formation, particularly C–H functionalisation and the alkenylation of aromatic C–H bonds in indoles and CMD/AMLA-6 mechanism. Together, the Jones and pentafluorobenzene. Perutz presentations showed that one should con- The seventh session was chaired by Jason M. Lynam sider both C–H acidity and metal–carbon (aryl) and the Keynote lecture was given by Professor bond strengths when explaining the regioselective C–H functionalisation accelerated by ortho-fluorine substituents. Kinetically stable metallic Pd nanoparticles Theoretical Aspects (<5 nm) The final session was chaired by Professor Odile Eisenstein, and began with an invited lecture by Professor Stuart Macgregor (Heriot-Watt University, UK). Macgregor delivered an introduction to theoretical approaches, following previous comments on the strengths, weaknesses and pitfalls of certain aspects of density functional theory (DFT) calcula- Ar1X tions. More detailed computational studies were Ar –Ar 1 2 presented on catalytic alkene hydroarylation with 2 + Ar2B(OH)2 [CpIr((κ -OAc)(PH3)] , with particular emphasis on Heterogeneous catalytic cycle the AMLA-6 mechanism. This once again highlighted the key role played by the ‘flexible’ acetate ligand. Fig. 1. Palladium-surface catalysed Eric Clot (Université Montpellier II, France) went on Suzuki-Miyaura cross-couplings (From to present a DFT study of the mechanism of Pd(PR3)- A. F. Lee et al., in (2). Reproduced by 3 permission of The Royal Society of catalysed benzocyclobutene formation via C(sp )–H Chemistry) activation. In the final presentation, Professor Mike

Fig. 2. The ortho-fluorine effect in Rh–C/C–H [Rh] H R = 2.15 promoting carbon–hydrogen activation. Rh–C/C–H R3P R = slope of line on plot of Rh–C vs. C–H bond strength (From [Rh] H T. Tanabe et al., in (2). Reproduced by R3P F [Rh] H permission of The Royal Society of –1 Fn Chemistry) 8 kcal mol R3P F F F ortho –1 n -fluorine effect 5 kcal mol

[Rh] = Tp’Rh Tp’ = tris(3,5-dimethylpyrazolyl)borate

George (The University of Nottingham, UK) presented a combined experimental (fast time-resolved infrared spectroscopy (TRIR)) and theoretical investigation of the C–H activation of cyclic alkanes by cyclopentadi- enyl rhodium(I) carbonyl complexes. He highlighted the inherent mechanistic differences in C–H activation of linear versus cyclic alkanes by half-sandwich rhodium complexes. Interestingly, C–H activation in cyclic alkanes depends primarily on the strength of alkane–metal binding. Note that this paper appeared in a later issue of Dalton Transactions (5).

Poster Prizes Following the conference dinner in the famous Fig. 3. Poster prize winners of Dalton Discussion 12: Durham Castle, Professors Love and Perutz awarded Julien Panetier (Heriot-Watt University), Toritse four poster prizes. The poster content of the awardees Bob-Egbe (Imperial College London), Anne Germeroth (Figure 3)highlighted the breadth of subjects covered (University of Edinburgh) and Amanda Jarvis (University of York) and the high standard of all of the posters presented at the meeting.The winning posters were: • ‘Hydrodefluorination of Fluoroaromatics by Concluding Remarks

[RuH2(CO)(NHC)(PPh3)2]: An Explanation for From the oral presentations, numerous posters and the 1,2-Regioselectivity’, Julien Panetier (Heriot- lively discussions at the DD12 meeting, there was Watt University,UK) overwhelming evidence that a better understanding • ‘Development of Chiral 4-(DAAP)-N-oxide of the mechanisms of metal-catalysed C–X and C–H Catalysts for the Sulfonylative Kinetic Resolution functionalisation processes is emerging. Quite strik- of Amines’, Toritse Bob-Egbe (Imperial College ingly,studies in inorganic and organometallic coordi- London,UK) nation chemistry,theoretical and kinetic studies, new • ‘Reversible Reactions Across the M–C Bond of synthetic methodologies and applications are driving Lanthanide NHC Complexes to Form New N–E this understanding. The platinum group metals play and C–E Bonds’, Anne Germeroth (University of an important role in many of the catalytic processes Edinburgh, UK) under discussion. • ‘Novel Multidentate Phosphine-Alkene Ligands As a first joint discussion conference between the for Catalysis’, Amanda Jarvis (University of York, RSC Dalton and Organic Divisions, it was a great suc- UK) cess, and showed quite clearly that both the organic

and inorganic communities need to work together to K. Huang, S.-F. Zheng, B.-J. Li and Z.-J. Shi, Nature deliver powerful, clean and efficient methods for the Chem., 2010, 2, (12), 1044 preparation of functionalised organic building blocks 5 M. W. George, M. B. Hall, P. Portius, A. L. Renz, X.-Z. and fine chemicals. Sun, M. Towrie and X. Yang, Dalton Trans., 2011, 40, (8), 1751

The Reviewer References 1 RSC Conferences and Events, Dalton Discussion 12: Professor Ian Fairlamb is currently a Catalytic C–H and C–X Bond Activation (DD12): http:// Full Professor in Organic Chemistry at www.rsc.org/ConferencesAndEvents/RSCConferences/ the University of York, UK, and has research interests in catalysis, synthetic dd12/index.asp (Accessed on 31 December 2010) chemistry, mechanistic understanding, 2 Dalton Discussion 12: Catalytic C–H and C–X bond nanocatalysis, metals in medicine, and activation (DD12), Dalton Trans., 2010, 39, (43), applications of catalysis in chemical biology. In 2004, he was awarded 10321–10540 both a Royal Society University 3 The Nobel Prize in Chemistry 2010: http://nobelprize.org/ Research Fellowship and the Royal Society of Chemistry Meldola Medal nobel_prizes/chemistry/laureates/2010/ (Accessed on 31 and Prize for outstanding contributions December 2010) to the field of palladium chemistry 4 C.-L. Sun, H. Li, D.-G. Yu, M. Yu, X. Zhou, X.-Y. Lu, in synthesis.

A Healthy Future: Platinum in Medical Applications Platinum group metals enhance the quality of life of the global population

doi:10.1595/147106711X566816 http://www.platinummetalsreview.com/

By Alison Cowley The world’s growing population demands increasing Johnson Matthey Precious Metals Marketing, Orchard access to advanced healthcare treatments. Platinum is Road, Royston, Hertfordshire SG8 5HE, UK used to make essential components for a range of medical devices, including pacemakers, implantable defibrillators, catheters, stents and neuromodulation and Brian Woodward* devices. The properties of platinum which make it Johnson Matthey Medical Products, 12205 World Trade suitable for medical device applications include its bio- Drive, San Diego, California 92128, USA; compatibility,inertness within the body,durability,elec- *E-mail: [email protected] trical conductivity and radiopacity.Components can be manufactured in a variety of forms, from rod, wire and ribbon to sheet and foil, plus high-precision micromachined parts. As well as biomedical device components,platinum also finds use in anticancer drugs such as cisplatin and carboplatin.

Introduction According to the United Nations Environment Programme (UNEP), the global population will reach over 9 billion by 2050 with nearly 90% of the world’s people located in developing countries (Figure 1) (1). Since the early 1970s, platinum has been used in a variety of medical devices for people around the world suffering from such ailments as heart disease, stroke, neurological disorders, chronic pain and other life threatening conditions. In 2010, some 175,000 oz of platinum are estimated to have been used in biomedical devices, of which around 80 per cent was for established technologies such as guidewires and cardiac rhythm devices. The remaining 20 per cent was used in newer technologies, such as neuromodulation devices and stents. In addition, over 25,000 oz of platinum are used annually in anticancer drugs (2). With an ageing and increasing world population, there will be an increasing demand for healthcare products and services that use components made from platinum, other platinum group metals (pgms) and their alloys. Increasing access to healthcare and advanced medical treatments in developing countries means that platinum contributes to improving the quality of life of people around the world.

Fig. 1. Trends in population, developed and 8 developing countries, between 1750–2050 (estimates and 6 projections) (1) (Image: Hugo Ahlenius, Nordpil)

4 (billions)

2 Developed countries

Developing countries Global population, estimates and projections 0 1750 1800 1850 1900 1950 2000 2050 Year

The Advantages of Platinum for artery disease such as balloon angioplasty and stent- Biomedical Uses ing where inertness and visibility under X-ray are The chemical, physical and mechanical properties of crucial. In the field of cardiac rhythm disorders, platinum and its alloys make them uniquely suitable platinum’s durability, inertness and electrical conduc- for a variety of medical applications. Agnew et al. (3) tivity make it the ideal electrode material for devices and Brummer et al.(4) carried out studies which con- such as pacemakers, implantable defibrillators and firmed the low corrosivity,high biocompatibility and electrophysiology catheters. More recently, its unique good mechanical resistance of platinum and plat- properties have been exploited in neuromodulation inum alloys that are used for medical applications. devices (including “brain pacemakers”, used to treat Platinum’s biocompatibility makes it ideal for some movement disorders, and cochlear implants, to temporary and permanent implantation in the body, restore hearing), and in coils and catheters for the a quality which is exploited in a variety of treatments. treatment of brain aneurysms. As a metal, it can be fabricated into very tiny, complex shapes and it has some important properties not Platinum in Biomedical Applications shared by base metals. It is inert, so it does not cor- Devices for Cardiac Rhythm Management rode inside the body unlike metals such as nickel Abnormalities of the heart’s rhythm are common, and copper, which can sometimes cause allergic often debilitating, and sometimes fatal. For example, reactions. Modern, minimally-invasive medical tech- bradycardia is a condition in which the heart’s niques often use electricity to diagnose and treat “natural pacemaker” is set too slow, resulting in patients’ illnesses, and platinum’s conductivity makes fatigue, dizziness and fainting. Other patients may it an ideal electrode material. It is also radiopaque, be at risk of sudden cardiac death, a condition in so it is clearly visible in X-ray images, enabling doc- which the heart’s lower chambers (the ventricles) tors to monitor the position of the device during “fibrillate”, or pulse in a rapid and uncoordinated treatment. Some examples of areas where pgms are manner. This prevents the heart from pumping used in medical devices, together with some of the blood and leads rapidly to death unless the victim manufacturers currently active in the medical device receives cardioversion (a strong electric shock to the market, are shown in Table I. heart, which restores normal rhythm). For more than forty years platinum alloys have These and other cardiac rhythm disorders can been employed extensively in treatments for coronary now be managed very successfully using implanted

Table I Markets for Medical Devices and the Major Device Companies

Medical device markets Examples of application areas Major medical device companies

Surgical instrumentation Arthroscopic; ophthalmology; Boston Scientific; Johnson & endo-laparoscopic; electro-surgical Johnson; Stryker; Tyco Electro-medical implants Pacemakers; defibrillators; hearing Boston Scientific; Biotronik; assist devices; heart pumps Medtronic; St. Jude Medical Interventional Stents; angioplasty; catheter Boston Scientific; Abbott Vascular; ablation; distal protection Johnson & Johnson; Medtronic Orthopaedics Spinal fixation; hip implants; Biomet; Johnson & Johnson; knee implants Stryker; Zimmer

devices such as artificial pacemakers (5, 6) and coronary arteries are often treated using a procedure implantable cardioverter defibrillators (ICDs) (7–9). called “percutaneous transluminal coronary angio- These consist of a “pulse generator”, a small box plasty” (PTCA, also known as balloon angioplasty) containing a battery and an electronic control sys- (15,16). This treatment uses a catheter with a tiny bal- tem which is implanted in the chest wall, and one loon attached to its end, which is guided to the treat- or more leads which run through a large vein into ment site then inflated, crushing the fatty deposits the heart itself. The electrodes on these leads deliver and clearing the artery. Afterwards, a small tubular electrical impulses to the heart muscle – in the case device called a stent (Figure 3) is usually inserted in of a pacemaker, these ensure that the heart beats order to keep the newly-cleared artery open. regularly and at an appropriate pace, while in the The advent of the implantable metal stent to prop case of an ICD, a much stronger electrical shock is open the artery after angioplasty reduced the delivered as soon as the device detects a dangerously occurrence of restenosis (re-narrowing of the artery) irregular heartbeat. Each lead typically has two or by more than 25 per cent. In 2003 the US FDA more electrodes made of platinum-iridium alloy, approved the first drug-eluting stent for use within while platinum components are also used to con- the USA (17). This type of stent is aimed at further nect the pulse generator to the lead (Figure 2). lowering the rate of restenosis following angioplasty procedures. Catheters and Stents Platinum’s role in PTCA is to help ensure that the Catheters are flexible tubes which are introduced balloon is correctly located. First, the surgeon uses a into the body to help diagnose or treat illnesses guidewire to direct the balloon to the treatment site. such as heart disease (10–13). The doctor can per- This guidewire is made of base metal for most of its form delicate procedures without requiring the length, but has a coiled platinum-tungsten wire at patient to undergo invasive surgical treatment, its tip, which makes it easier to steer and ensures improving recovery time and minimising the risk of that it is visible under X-ray. Platinum is also used in complications. Many catheters incorporate platinum marker bands, tiny metal rings which are placed components: marker bands and guidewires, which either side of the balloon in order to keep track of help the surgeon guide the catheter to the treatment its position in the body. site, or electrodes, which are used to diagnose and Stents are usually made of base metals (typically treat some cardiac rhythm disorders (arrhythmias). stainless steel or cobalt-chromium). However, in One of the most common coronary complaints in 2009, the American device manufacturer Boston the developed world is atherosclerosis, the “furring Scientific introduced a cardiac stent made of a plat- up” of the artery walls with fatty deposits, which can inum chromium alloy (18–20). This stent has been lead to angina and heart attack (14). Blockages in the approved in Europe, and the company is currently

Pt or Pt-Ir through ® wires for multi-pin Pt-Ir, MP35N or hermetic seal, inside stainless steel the seal housing machined parts for (0.015” terminal connector (0.381 mm) and 0.013” (0.330 mm)) Pt or Pt-Ir wire and ribbon multifilar coils for high- voltage shocking electrodes

Pt-Ir alloy rings for shocking electrodes

TiNi-coated Pt-Ir machined parts for passive fixation leads Porous TiNi-coated Pt-Ir helix and post assembly for active fixation leads

Fig. 2. An implantable cardioverter defibrillator, showing the components that are made from platinum or platinum group metal alloys seeking approval from the US Food & Drugs heart so that the appropriate treatment – such as a Administration (FDA). pacemaker – can be prescribed. Catheters containing platinum components are Other catheters with platinum electrodes are used also used to detect and treat some types of cardiac for a minimally-invasive heart treatment known as arrhythmia (21, 22). Devices called electrophysiology radio-frequency (RF) ablation (24–26). Arrhythmias catheters (23), which contain platinum electrodes, are often caused by abnormalities in the conduction are used to map the electrical pathways of the of electricity within the heart, and it is often possible

Fig. 3. A balloon-mounted stent used in Stent (stainless percutaneous transluminal coronary steel, Co-Cr, Balloon angioplasty (PTCA, or balloon angioplasty) Co-Cr with Pt, supporting Guidewire with procedures (Copyright © Abbott Vascular or nitinol) the stent coiled Pt-W tip Devices)

Marker band (Pt, Pt-Ir or Au)

to cauterise part of the heart muscle in order to to digital information, which is transmitted via the restore normal heart rhythm. For example, ablation coil to the implant. This in turn converts the digital is increasingly used to treat a very common heart signal into electrical impulses which are sent to the problem called atrial fibrillation, in which the upper electrode array in the cochlea, where they stimulate chamber of the heart (the atrium) quivers rapidly and the hearing nerve. These impulses are interpreted by erratically. Using a catheter equipped with platinum- the brain as sound. It is believed that around 200,000 iridium electrodes, the surgeon “ablates” or makes people worldwide have received one or more small burns to the heart tissue, causing scarring, cochlear implants. which in turn blocks the superfluous electrical At present, neuromodulation is expensive and is impulses which trigger the fibrillation. only available in a small number of specialist centres; even in developed countries only a small proportion Neuromodulation Devices of potentially eligible patients receive this treatment. Neuromodulation devices deliver electrical impulses However, neuromodulation can be used to help to nerves and even directly to the brain, treating dis- patients with common and sometimes difficult to orders as varied as deafness, incontinence (27, 28), treat conditions (such as chronic pain, epilepsy and chronic pain (29) and Parkinson’s disease (30).Many migraine). Its use might therefore be expected to of these devices are based on an extension of heart increase significantly in coming years as new indica- pacemaker technology, and they are sometimes tions for these therapies are established. referred to as “brain pacemakers” (31). Like heart pacemakers, they have platinum-iridium electrodes Other Implants and may also incorporate platinum components in Platinum’s biocompatibility makes it ideal for tem- the pulse generator. porary and permanent implantation in the body, There are a number of different types of neurostim- a quality which is exploited in a variety of treatments ulation, depending on the condition that is being in addition to the heart implants already discussed. treated. Spinal cord stimulation (the commonest Irradiated iridium wire sheathed in platinum can be neuromodulation therapy) is used to treat severe implanted into the body to deliver doses of radiation chronic pain, often in patients who have already for cancer therapy (39–41). This treatment takes had spinal surgery. Small platinum electrodes are advantage of platinum’s radiopacity to shield healthy placed in the epidural space (the outer part of the tissues from the radiation, while the exposed iridium spinal canal) and connected to an implanted pulse tip of the wire irradiates the tumour. Although this generator. The patient can turn the stimulation off procedure is gradually being replaced by other forms and on, and adjust its intensity. of radio- and chemotherapy, it remains a useful In deep brain stimulation (DBS) (32–34), the elec- weapon in the battle against cancer. trodes are placed in the brain itself. As well as pain, A more recent development is the use of coils DBS may be used to treat movement disorders such made of platinum wire to treat aneurysms, balloon- as Parkinson’s disease, and it is being investigated as a ings in blood vessels caused by weaknesses in the potential treatment for a wide range of other illnesses, vessel walls (42).If the blood pressure rises, the vessel including epilepsy and depression. Epileptic patients may rupture, causing a haemorrhage. Although this can also be treated using a vagus nerve stimulation can occur anywhere in the body,platinum is mainly device (the vagus nerve is situated in the neck). used to treat aneurysms in the brain,where surgery is A cochlear implant (35–38) is used to restore hear- difficult and fraught with risk. Platinum is used ing to people with moderate to profound hearing because it is inert, easy to shape, and radiopaque. loss (many patients receive two implants, one in each This treatment was first introduced about 20 years ear). A typical device consists of a speech processor ago. In the late 1980s, a doctor and inventor, Guido and coil, which are worn externally behind the ear, Guglielmi (43–45), developed a detachable platinum an implanted device just under the skin behind the coil which could be used to treat brain aneurysms. ear, and a platinum electrode array which is posi- Coils are delivered to the site of the aneurysm by tioned in the cochlea (the sense organ which microcatheter, then detached using an electrolytic converts sound into nerve impulses to the brain). detachment process; once in place, the coils help to The speech processor captures sound and converts it coagulate the blood around the weak vessel wall,

Fig. 4. Detachable (a) (b) (c) platinum coils being used to treat an aneurysm: (a) a microcatheter is used to deliver the platinum coils to the aneurysm; (b) the coils are detached using an electrolytic process; (c) more coils are added to fill the aneurysm and allow blood to coagulate, forming a permanent seal forming a permanent seal (Figure 4). The coils, num- (0.0254 mm). Dimensional consistency is assured by bering between one and around thirty depending on laser measurement. Rod is used as the starting material the size of the aneurysm, are left inside the patient for a variety of machine components, with most of indefinitely. The Guglielmi Detachable Coil (GDC® the pgm parts being used in pacemaker, defibrillator Coil) device was approved in Europe in 1992 and in and other electrical stimulation products. Wire prod- the USA in 1995, and by 2009 this and subsequent ucts are used primarily in three applications: generations of platinum coil technology were being (a) platinum-tungsten and platinum-nickel fine used in an estimated 30–40% of US patients treated wires are used on balloon catheters as guide- for brain aneurysms. wires for positioning the catheter in exactly the right location; The Manufacture of Platinum (b) other pgm wires are used as microcoils for neu- Biomedical Components rovascular devices such as treatments for brain There are many technologies used to produce pgm aneurysms; components for biomedical applications, ranging (c) platinum-iridium wires are also used as feed- from rod, wire, ribbon and tube drawing, to sheet through wires or connector wires used to and foil manufacture and highly precise Swiss-Type connect the pacemaker lead to the pulse screw machining (micromachining) (see Figure 5). generator. Rod and wire are manufactured in diameters Ribbon is manufactured in the form of continuous ranging from 0.125" (3.175 mm) down to 0.001" strips of rolled wire in a variety of platinum alloys. Ribbon is often used in place of round wire to produce coils with minimum outside diameter, and is generally used for guidewire and microcoil applications. Ribbon is sometimes preferred over wire because wire can be harder to coil. It can also be used for markers instead of traditional cut tubing. Table II shows some typical specifications and applications for pgm rod, wire and ribbon. Fine diameter platinum, platinum-iridium and platinum-tungsten tubing (0.125" (3.175 mm) internal diameter and below) cut to specific lengths is used for markers or electrodes on angioplasty, electrophysiology and neurological catheter devices, aneurism tip coils, feed-through wires used to connect the pacing lead to the pulse generator (also known as “the can”) which houses the hybrid micro- electronics and the battery, and pacemakers. Some Fig. 5. Micromachined parts made from precious metal alloys for biomedical device applications, with applications of thin walled precious metal tubing a pencil tip for scale are shown in Table III.

Table II Specifications and Applications of Platinum and Platinum Alloy Rod, Wire and Ribbon Components

Applications Types of component Specifications

Stimulation devices Rod for manufacture of Diameters from 0.001" (0.0254 mm) machine components to 0.125" (3.175 mm); Cut lengths Balloon catheters; stent Guidewires; feed through from 0.02" (0.508 mm) delivery; stimulation leads wires; tip coils

Table III Specifications and Applications of Platinum, Palladium, Gold and Precious Metal Alloy Thin Walled Tube Components

Applications Types of component Specifications

Balloon catheters Radiopaque marker Inside diameter 0.0045" (0.1143 mm) to 0.250" (6.35 mm), bands (tolerance: ± 0.0005" (0.0127 mm)); Wall thickness 0.001" (0.0254 mm) to 0.005" (0.127 mm), (tolerance: Electrophysiology Electrode rings ± 0.0005" (0.0127 mm)); Length 0.015" (0.381 mm) to catheters; 0.200" (5.08 mm), (tolerance: ± 0.003" (0.0762 mm)) stimulation devices

Sheet and foil is mainly made from pure platinum, the necessary quality and dimensional tolerances, platinum-iridium alloys or rhodium. It can be shaped, which can be as low as ± 0.0002" (0.005 mm). Highly formed and rolled to a variety of dimensions. Sheet specialised equipment and techniques must be used, or foil can be cut, formed and placed on a catheter such as computer numerical controlled (CNC) Swiss for marking in a similar way to ribbon. Rhodium foil Screw machines and electrical discharge machining is used exclusively as a filter inside X-ray mammog- (EDM) (Figure 6). The automated high-production raphy equipment to enhance the viewing image. Swiss Screw machines are used to fabricate the main Table IV shows some examples of applications of components and EDM is used to achieve the fine pgm sheet and foil. details required for many platinum parts. Micromachined parts are very complex and very Specialty metal micromachined parts (0.8" (20 mm) small – some are only 0.006" (0.152 mm) in diameter diameter and smaller) are made from a variety of and barely visible with the naked eye (Figure 5). materials including pure platinum, platinum-iridium Fabrication must be extremely precise to maintain alloys and gold plus non-precious metals and

Table IV Specifications and Applications of Platinum, Platinum Alloy and Rhodium Sheet and Foil Components

Applications Types of component Specifications

Stimulation devices Electrodes; machine components; Thickness from 0.0007" (0.018 mm); tip coils Width from 1.0" (25.4 mm) to 3.75" (95.3 mm) X-Ray equipment Imaging filters (rhodium foils)

Fig. 6. The production floor at Johnson Matthey’s Medical Products micromachining facility in San Diego, California, USA alloys such as stainless steel, titanium, MP35N® stents, pacemaker and defibrillator pulse generator cobalt-nickel-chromium-molybdenum alloy, Elgiloy® and lead components, heart valve splices, endoscop- cobalt-chromium-nickel alloy, Kovar® iron-nickel- ic catheters, blood gas analysers, kidney dialysis, and cobalt alloy,and materials such as Vespel®, Delrin® other medical device and related equipment. and Teflon® (see Table V for examples). These prod- Parts made from pgms are often complemented ucts serve device applications such as coronary with a coating technology. Precious metal powders,

Table V Applications and Materials for Precision Micromachined Components

Applications Precious metals* Other materials, metals and alloys

Stimulation Platinum; platinum alloys; Nitinol; stainless steel; MP35N®; palladium; palladium alloys Haynes® alloy 25 (L605); polymers Manufacturing fixtures Platinum; platinum alloys Stainless steel 303/304/316; polymers Orthopaedic Platinum; platinum alloys Titanium; titanium alloys; stainless steel; ceramics Cardiac implants Platinum; platinum alloys; Elgiloy®; Nitinol karat golds Hypotubes Platinum; platinum alloys Stainless steel; Nitinol Precision pins, tips and Platinum; platinum alloys; silver – rollers Bushings, shafts, shims Platinum; platinum alloys Aluminium and spacers Precision fixtures and Platinum; platinum alloys; BiomedTM Brass; copper; Kovar® assembly tools series palladium-rhenium alloys

*Platinum alloys used include platinum-iridium, platinum-10% nickel and platinum-8% tungsten

titanium nitride or iridium oxide are applied to cancer patients. Medical device manufacturers and create a more porous surface structure. The creation pharmaceutical companies continue to invest in new of a porous coating reduces the electrical impedance technologies to satisfy the need for advanced med- from the lead to the battery and allows for a good ical treatments in both the developed world and, electrical connection, while reducing the energy increasingly, the developing world. Platinum, the needed to run the battery. This helps the battery to other pgms and their alloys will inevitably play a vital last longer. Most pacing lead systems manufactured part in these developments. today have some form of porous surface. The end use applications for coated pgm parts are the same as Acknowledgements described above for uncoated parts. The assistance of Richard Seymour and Neil Edwards, Technology Forecasting and Information, Johnson Anticancer Drugs Matthey Technology Centre, Sonning Common, UK, As well as its use in biomedical device components, in the preparation of this manuscript is gratefully perhaps platinum’s most remarkable and unexpected acknowledged. quality is its ability, in certain chemical forms, to inhibit the division of living cells (46). The discovery References of this property led to the development of platinum- 1 UNEP/GRID-Arendal, ‘Trends in population, developed based drugs (47), which are now used to treat a wide and developing countries, 1750–2050 (estimates and range of cancers. projections)’, UNEP/GRID-Arendal Maps and Graphics Library, 2009: http://maps.grida.no/go/graphic/trends- Although cancer remains one of the most feared in-population-developed-and-developing-countries- diseases, its treatment has advanced rapidly since the 1750-2050-estimates-and-projections (Accessed on 9th late 1960s. Many types of cancer can now be treated February 2011) very effectively using surgery, radiation and drug- 2 J. Butler, “Platinum 2010 Interim Review”, Johnson based (chemo-) therapies. Chemotherapy drugs work Matthey, Royston, UK, 2010, pp. 21–22 by killing cells. They are designed to target cancer 3 W. F. Agnew, T. G. H. Yuen, D. B. McCreery and cells as specifically as possible, but inevitably cause L. A. Bullara, Exp. Neurol., 1986, 92, (1), 162 damage to healthy cells as well, causing the side 4 S. B. Brummer and M. J. Turner, IEEE Trans. Biomed. Eng., effects for which chemotherapy is well known. 1977, BME-24, (5), 440 One of the most remarkable advances in the last 5 Acta Med. Scand., 1969, 186, (S502), 10–13 few decades has been the improvement in the sur- 6 C. Walton, S. Gergely and A. P. Economides, Pacing Clin. vival rate of patients with testicular cancer – it is esti- Electrophysiol., 1987, 10, (1), 87 mated that 98% of men with testicular cancer will be 7 R. A. Winkle, S. M. Bach, Jr., R. H. Mead, V. A. Gaudiani, E. B. Stinson, E. S. Fain and P. Schmidt, J. Am. Coll. alive 10 years after their diagnosis. The platinum anti- Cardiol., 1988, 11, (2), 365 cancer drug cisplatin (47) has played a vital role in 8 M. M. Morris, B. H. KenKnight, J. A. Warren and D. J. making testicular cancer one of the most survivable Lang, Am. J. Cardiol., 1999, 83, (5), Suppl. 2, 48 cancers. This drug, along with its successor drug, 9 D. S. Cannom, Am. J. Cardiol., 2000, 86, (9), Suppl. 1, K58 carboplatin (48), is also widely used in the treatment 10 A. M. Rudolph, Am. J. Surgery, 1964, 107, (3), 463 of other common tumours, including ovarian, breast 11 J. E. Lock, J. F. Keane and K. E. Fellows, J. Am. Coll. and lung cancer. Cardiol., 1986, 7, (6), 1420 12 J. J. Rome and J. F. Keane, Prog. Pediatric Cardiol., 1992, Summary 1, (2), 1 For over forty years, platinum and its alloys have been 13 J. D. Moore and T. P. Doyle, Prog. Pediatric Cardiol., used in a wide range of medical treatments, includ- 2003, 17, (1), 61 ing devices such as coronary and peripheral 14 C. A. McMahan, S. S. Gidding and H. C. McGill, Jr., catheters, heart pacemakers and defibrillators. Newer J. Clin. Lipidol., 2008, 2, (3), 118 technologies such as neuromodulation devices and 15 A. S. Jacob, T. S. Goldbaum, A. D. Richard and J. Lindsay, Jr., stents also rely on the biocompatibility, durability, Catheterization Cardiovascular Diagnos., 1986, 12, (1), 64 conductivity and radiopacity of platinum to make key 16 N. H. Singh and P. A. Schneider, ‘Balloon Angioplasty Catheters’, in “Endovascular Surgery”, 4th Edn., eds. components in a variety of forms. Platinum is used in W. S. More and S. S. Ahn, Elsevier Saunders, pharmaceutical compounds that extend the lives of Philadelphia, PA, USA, 2011, Chapter 8, pp. 71–80

17 US FDA, Recently-Approved Devices, CYPHERTM Sirolimus- 40 N. J. Daly, B. De Lafontan and P. F. Combes, Int. J. eluting Coronary Stent – P020026, Approval date: Radiation Oncol. Biol. Phys., 1984, 10, (4), 455 24th April, 2003: http://www.fda.gov/MedicalDevices/ 41 J. L. Habrand, A. Gerbaulet, M. H. Pejovic, G. Contesso, ProductsandMedicalProcedures/DeviceApprovalsandClea S. Durand, C. Haie, J. Genin, G. Schwaab, F. Flamant, rances/Recently-ApprovedDevices/ucm082499.htm M. Albano, D. Sarrazin, M. Spielmann and D. Chassagne, (Accessed on 10th February 2011) Int. J. Radiat. Oncol. Biol. Phys., 1991, 20, (3), 405 18 ‘Platinum-Stainless Steel Alloy and Radiopaque Stents’, 42 R. T. Higashida, V. V. Halbach, C. F. Dowd, S. L. Barnwell C. H. Craig, H. R. Radisch, Jr., T. A. Trozera D. M. and G. B. Hieshima, Surg. Neurol., 1991, 35, (1), 64 Knapp, T. S. Girton and J. S. Stinson, SciMed Life Systems, 43 G. Guglielmi, F. Viñuela, I. Sepetka and V. Macellari, Inc, World Appl. 2002/078,764 J. Neurosurg., 1991, 75, (1), 1 19 B. J. O’Brien, J. S. Stinson, S. R. Larsen, M. J. Eppihimer 44 G. Guglielmi, F. Viñuela, J. Dion and G. Duckwiler, and W. M. Carroll, Biomaterials, 2010, 31, (14), 3755 J. Neurosurg., 1991, 75, (1), 8 20 I. B. A. Menown, R. Noad, E. J. Garcia and I. Meredith, 45 G. Guglielmi, Oper. Tech. Neurosurg., 2000, 3, (3), 191 Adv. Ther., 2010, 27, (3), 129 46 B. Rosenberg, L. Van Camp and T. Krigas, Nature, 1965, 21 G. V. Irons, Jr., W. M. Ginn, Jr., and E. S. Orgain, 205, (4972), 698 Am. J. Cardiol., 1968, 21, (6), 894 47 E. Wiltshaw, Platinum Metals Rev., 1979, 23, (3), 90 22 W. H. Barry, E. L. Alderman, P. O. Daily and D. C. Harrison, Am. Heart J., 1972, 84, (2), 235 48 C. F. J. Barnard, Platinum Metals Rev., 1989, 33, (4), 162 23 J. G. Panos, J. L. Cincunegui and E. K. Chong, Heart Lung Circ., 2007, 16, Suppl. 2, S117 Further Reading 24 J. F. Swartz, C. M. Tracy and R. D. Fletcher, Circulation, “Biomaterials Science: An Introduction to Materials in 1993, 87, (2), 487 Medicine”, 2nd Edn., eds. B. Ratner, A. Hoffman, F. Schoen 25 H. Calkins, Med. Clin. North Am., 2001, 85, (2), 473 and J. Lemons, Elsevier Academic Press, San Diego, CA, USA, 2004 26 ‘Ablation Catheter Assembly Having a Virtual Electrode Comprising Portholes’, G. P. Vanney, J. D. Dando and “Materials and Coatings for Medical Devices: Cardio- J. L. Dudney, St. Jude Medical, Daig Division, Inc, US Patent vascular”, ASM International, Materials Park, Ohio, 6,984,232; 2006 USA, 2009 27 R. D. Mayer and F. M. Howard, Neurotherapeutics, Granta: Materials for Medical Devices Database, Cardio- 2008, 5, (1), 107 vascular Materials and Orthopaedic Materials: http://www. grantadesign.com/products/data/MMD.htm (Accessed on 28 P. M. Braun, C. Seif, C. van der Horst and K.-P. 10th February 2011) Jünemann, EAU Update Series, 2004, 2, (4), 187 29 P. L. Gildenberg, Pain Med., 2006, 7, Suppl. s1, S7 30 W. Hamel, U. Fietzek, A. Morsnowski, B. Schrader, The Authors J. Herzog, D. Weinert, G. Pfister, D. Müller, J. Volkmann, G. Deuschl and H. M. Mehdorn, J. Neurol. Neurosurg. Alison Cowley has worked in Johnson Matthey’s Market Research Psychiatry, 2003, 74, (8), 1036 department since 1990 and currently 31 M. L. Kringelbach and T. Z. Aziz, Scientific American holds the post of Principal Analyst. Mind, December 2008/January 2009 She is Johnson Matthey’s specialist on mining and supplies of the platinum 32 D. Tarsy, Epilepsy Behav., 2001, 2, (3), Suppl. 0, S45 group metals (pgms). She also conducts research into demand for 33 J. Gimsa, B. Habel, U. Schreiber, U. van Rienen, U. Strauss pgms in a number of industrial and U. Gimsa, J. Neurosci. Meth., 2005, 142, (2), 251 markets, including the biomedical 34 P. Limousin and I. Martinez-Torres, Neurotherapeutics, and aerospace sectors. 2008, 5, (2), 309

35 G. Clark, “Cochlear Implants”, Springer-Verlag, New Brian Woodward has been involved in York, USA, 2003 the electronic materials and platinum fabrication business for more than 36 J. T. Roland, Jr., Oper. Tech. Otolaryngol. Head Neck 25 years and is currently the General Surg., 2005, 16, (2), 86 Manager of Johnson Matthey’s Medical 37 E. G. Eter and T. J. Balkany, Oper. Tech. Otolaryngol. Products business based in San Diego, CA, USA. He holds BS and MBA Head Neck Surg., 2009, 20, (3), 202 degrees in Business and Management 38 M. Cosetti and J. T. Roland, Jr., Oper. Tech. Otolaryngol. and has been focused on value-added Head Neck Surg., 2010, 21, (4), 223 component supply to the global medical device industry. 39 J. G. Stella, S. Kramer, C. M. Mansfield and N. Suntharalingam, Cancer, 1973, 32, (3), 665

Fuel Cells Science and Technology 2010 Scientific advances in fuel cell systems highlighted at the semi-annual event

doi:10.1595/147106711X554503 http://www.platinummetalsreview.com/

Reviewed by Donald S. Cameron This was the fifth conference in the Fuel Cells The Interact Consultancy, 11 Tredegar Road, Science and Technology series following meetings Reading RG4 8QE, UK; in Amsterdam, Munich, Turin and Copenhagen (1–4). E-mail: [email protected] It was held on 6th and 7th October 2010 at the World Trade Center in Zaragoza, Spain, with the theme ‘Scientific Advances in Fuel Cell Systems’. This conference series alternates with the Grove Fuel Cell Symposium (5), placing more emphasis on the latest technical developments. The two-day programme was compiled by the Grove Symposium Steering Committee from oral papers and posters submitted from around the world, and the conference was organised by Elsevier (6). The meeting was attended by delegates from universities, research organisations and the fuel cell industry,and as before, many of the papers will be subjected to peer review and published in full in a special edition of Journal of Power Sources (7). There were over 200 delegates from 37 countries, including Spain, Germany and the UK. Although the majority were from Europe, the significant numbers from Japan, Iran and South Korea reflected the high level of interest in fuel cells from those countries, as well as others from the Middle East, Asia, Africa and South America. The Science and Technology conferences present the latest advances in research and development on fuel cells and their applications. There were three plenary papers, together with eight keynote speakers and 40 oral papers, together with 210 high-quality poster presentations divided into seven categories. Topics for the oral sessions included Fuels, Infra- structure and Fuel Processing; Modelling and Control; Materials for Fuel Cells; Fuel Cell Systems and Applications; Fuel Cell Electrochemistry; and finally Cell and Stack Technology. For this review, only papers involving the use of the platinum group metals (pgms) are discussed. An exhibition accompanying the conference included displays of demonstration fuel cell systems designed for education and training use (Figures 1 and 2). Delegates were welcomed to Zaragoza by Pilar Molinero, Director General of Energy and Mining for the Aragon regional government, who formally

Fig. 2. One of a series of platinum-catalysed fuel cell and solar hydrogen systems for educational purposes designed and built by Heliocentris. This company develops systems and turnkey solutions for training in industry and science, and specialises in hybrid energy storage comprising fuel cells, batteries and energy management devices

high temperature fuel cells at the US Department of Fig. 1. A 1 kWe polymer electrolyte fuel cell and Energy’s Argonne National Laboratory and Lawrence control equipment designed for teaching purposes, Berkeley National Laboratory,and at the IIT. exhibited at the Fuel Cells Science and Technology Professor Selman presented a talk on his expe- 2010 conference. Operating on pure hydrogen, it riences and advances made during this period. One can be used to simulate a wide variety of fuel cell and CHP applications. It is built by HELION, an major development is the advent of computer model- AREVA subsidiary, and developed in collaboration ling which has led to improved structures and per- with teachers from Institut Universitaire de formance of fuel cells and their systems, although Technologie (IUT) of Marseille, France there is still a need to experimentally verify the pre- dictions obtained at each stage. Other exciting and opened the conference and briefly described activi- relatively new areas include the possibility of direct ties in Aragon to encourage hydrogen and fuel cell carbon oxidation fuel cells, and miniaturisation technologies. The large number of wind farms in the including biofuel systems and bioelectrochemistry. region have created an interest in energy storage One of his particular interests is the use of phase using water electrolysis to generate hydrogen during change materials to maintain the uniform tempera- periods of power surplus. A total of 30 hydrogen and tures in batteries by absorbing or evolving heat. fuel cell projects are being supported, including a hydrogen highway from Zaragoza to Huesca to sup- Fuels, Infrastructure and Fuel Processing port the introduction of fuel cell vehicles. Fuel cell technology has moved on from the largely research phase to commercial exploitation. A major Plenary Presentation market is being developed for combined heat and Pilar Molinero presented the 2010 Grove Medal to power (CHP) systems for residential domestic appli- Professor J. Robert Selman (Illinois Institute of cations operating on natural gas. In a keynote pres- Technology (IIT), USA), a leading academic who has entation, Sascha T. Schröder (National Laboratory for devoted more than 30 years to battery and fuel cell Sustainable Energy,Technical University of Denmark) research and development, and to global commer- outlined the policy context for micro combined heat cialisation of these technologies. This has included and power (mCHP) systems based on fuel cells. the electrochemical engineering of batteries and Systems of up to 50 kW have been considered,

although 3–5 kW units are preferred for domestic installations. Low- and high-temperature polymer electrolyte membrane (PEM) fuel cells are the most advanced, although there is still a need for less expensive reformers to make the systems economi- cally viable. Incentives in the form of a regulatory framework and ownership structures are of crucial importance to achieve widespread use of such devices in residential applications. A regulatory review has been conducted as part of the first Work Package of the EU-sponsored ‘FC4Home’ project, focused on Denmark, France and Portugal. Schröder outlined several types of possible support schemes, such as investment support in the form of capital Fig. 3. Steam reformer with superheater for grants and tax exemptions versus operating support supplying hydrogen to a PEM fuel cell in the form of feed-in tariffs, fiscal incentives and (Reprinted from M. Grote et al., (7), with other payments for energy generated, and how this permission from Elsevier) impacts on investment certainty. Also, the way in which incentives are offered is critical, for example heat transfer and chemical reactions were consid- via energy service companies, electrical network ered on both sides of the heat exchanger. The model operators, natural gas suppliers or network operators was successfully validated with experimental data or to individual house owners. Schröder reported that from reformer tests with 4 kW, 6 kW and 10 kW ther- in Denmark, there are 65 fuel cell mCHP installations, mal inputs of low sulfur light fuel oil and diesel fuel. and in France there are 832, mainly in industry. In further simulations the model was used to investi- Most fuel cells oxidise hydrogen gas using atmos- gate co-flow, counter-flow and cross-flow conditions pheric air to produce electric power and water. along with inlet geometry variations for the reformer. Hydrogen is generally obtained either by reforming The experimental results show that the reformer natural gas or liquid hydrocarbons, or by electrolysis design used for the validation allows inlet tempera- of water using surplus electrical energy. In recent tures lower than 500ºC because of its internal super- years there has been great interest in reforming diesel heating capability. The simulation results indicate fuel both for military and commercial purposes, that another two co-flow configurations provide fast since it uses an existing supply infrastructure. The superheating and high fuel conversion rates. The pgms are often used in reforming reactions and also temperature increase inside the reactor is influenced in downstream hydrogen purification. by the inlet geometry on the combustion side. In In a talk entitled ‘Experimental and Computational current investigations the optimised geometry con- Investigations of a Compact Steam Reformer for figurations are being tested in downscaled reformer Fuel Oil and Diesel Fuel’, Melanie Grote (OWI Oel- prototypes in order to verify the simulation results. Waerme-Institut GmbH, Germany) described the opti- Because of the great detail of their model, the effect misation of a compact steam reformer for light fuel of mass transfer limitations on reactor performance oil and diesel fuel, providing hydrogen for PEM fuel can now be investigated. Hydrogen of 73% concen- cells in stationary or mobile auxiliary applications. tration is typically produced. Their reformer is based on a catalytically-coated Successful extraction of hydrogen from heavy micro heat exchanger which thermally couples the hydrocarbons largely depends on the development reforming reaction with catalytic combustion, and of new catalysts with high thermal stability and also generates superheated steam for the reaction improved resistance to coke formation and sulfur (see Figure 3). Since the reforming process is sen- poisoning. A new range of ruthenium-containing sitive to reaction temperatures and internal flow perovskite oxide catalysts is being examined for patterns, the reformer was modelled using a commer- diesel fuel reforming. In a talk entitled ‘Hydrogen Pro- cial computational fluid dynamics (CFD) modelling duction by Oxidative Reforming of Diesel Fuel over code in order to optimise its geometry. Fluid flow, Catalysts Derived from LaCo1−xRuxO3 (x = 0.01–0.4)’,

Noelia Mota (Instituto de Catálisis y Petroleoquímica back-up power, power quality disturbance compen- del Consejo Superior de Investigaciones Científicas sation and peak shaving. In his talk ‘PEM Fuel Cells (CSIC), Spain) explained how under reforming con- Analysis for Grid Connected Applications’, Francesco ditions these LaCo oxides form well-dispersed cobalt Sergi (Consiglio Nazionale delle Ricerche, Italy) out- metallic particles over a matrix of lanthana. This lined their investigation of PEM fuel cell systems as increases hydrogen formation and prevents deactiva- components of power networks. The paper high- tion by coke and sulfur. To improve the activity and lighted the performances of PEM fuel cells using MEAs stability of LaCoO3-derived catalysts, structural and supplied by ETEK containing 30% Pt on Vulcan XC, electronic modifications can be introduced by and their behaviour during grid connected opera- partial substitution of Co by other transition metals, tion, particularly the phenomena of materials degra- and among these, ruthenium is a highly effective cat- dation that can appear in these applications. Several alyst. This work studied the influence of the partial tests were conducted both on fuel cell systems and substitution of Co over the physicochemical proper- single cells to compare the performances obtained ties of LaCo1−xRuxO3 perovskite where x = 0, 0.01, with DC and AC loads. Power drawn by single phase 0.05, 0.1, 0.2 or 0.4 and the effect on the structure grids contains low frequency fluctuations which and activity of the derived catalysts in the reforming cause a large ripple on the stack output current. of diesel fuel to produce hydrogen. There was an During tests on single cells, degradation of the MEA increase in the rate of hydrogen production associ- catalysts has been observed due to these dynamic ated with the higher ruthenium content. loads. A dedicated inverter designed to minimise the ripple current effect on the fuel cell stack has Fuel Cell Systems and Applications enabled durability tests to be performed on a 5 kW The fourteen member countries of the International Nuvera PowerFlowTM PEM fuel cell system which Energy Agency Hydrogen Implementing Agreement showed no decay in the ohmic region of operation of (IEA–HIA) have been instrumental in summarising the cell after 200 hours, even with the fuel cell sys- and disseminating information on integrated fuel cell tems operating on the utility grid. and electrolyser systems. In a keynote presentation Materials handling using forklift vehicles is proving entitled ‘Evaluation of Some Hydrogen Demonstra- to be one of the most exciting early markets for fuel tion Projects by IEA Task 18’, Maria Pilar Argumosa cells, with over 70 publicly reported demonstration (Instituto Nacional de Técnica Aeroespacial (INTA) programmes since 2005 (8). In this application, life- Spain) summarised some of their findings since the time and reliability are key parameters. A typical programme was established in 2003. In addition to forklift work cycle is characterised by heavy and fast establishing a database of demonstration projects variations in power demand, for example additional worldwide, the programme has reported in detail on power is required during lifting and acceleration. lessons learned from several demonstrations of This is not ideal for a fuel cell and hence it is pre- hydrogen distribution systems. The project concen- ferred to form a hybrid with an energy store. In his trated on fuel cells in the power range 2–15 kW and talk ‘Integrated Fuel Cell Hybrid Test Platform in exceptionally up to 150 kW. PEM and alkaline elec- Electric Forklift’, Henri Karimäki (VTT Technical trolysers were studied as hydrogen generators. No Research Centre of Finland) described how a hybrid safety incidents occurred during the project, power source has been developed for a large coun- although the fuel cells tested showed relatively high terweight forklift consisting of a pgm-catalysed PEM performance degradation in field operation. Capital fuel cell, ultracapacitors and lead-acid batteries. The costs of electrolysers are still high, and maintenance project was carried out in two phases, firstly in the costs for some systems have ranged up to €15,000 per laboratory with an 8 kW PEM fuel cell,a lead-acid bat- year although the warranty protocol was stipu- tery and ultracapacitor to validate the system, then a lated to be less than €3000 per year for the first second generation 16 kW hybrid system was built into three years. Electrolysers ranged from 50% to 65% a forklift truck (Figure 4). The latter power source efficiency based on the higher heating value of consisted of two 8 kW NedStack platinum-catalysed the fuel. PEM fuel cells with two 300 ampere-hour (Ah) lead- Future electrical networks will need active distrib- acid batteries and two Maxwell BOOSTCAP® 165F uted units able to ensure services like load following, 48V ultracapacitors, providing 72 kW of power.

Fig. 4. Hybrid forklift power source with 2 PEM fuel cell stacks (total fuel cell peak power 16 kW); 2 lead-acid battery packs (total battery capacity 24 kWh); 2 ultracapacitor modules (capacity ~72 kWs assuming 20% utilisation). Hybrid system peak power in the forklift is ~50 kWe (Reprinted from ‘Integrated PEMFC Hybrid Test Platform for Industrial Vehicles’, Fuel Cell Seminar 2010, 18th–21st October PEM fuel cells Lead-acid Ultra- Brake 2010, San Antonio, Texas, batteries capacitors resistor USA, by courtesy of T. Keränen, VTT Technical Research Centre of Finland)

Hydrogen for the PEM fuel cell is stored on board in firing cruise missiles while submerged. The system is metal hydride canisters connected in common with based on an on-board reformer supplying hydrogen the liquid cooling circuit. The energy stores were to a fuel cell power module. Their system will operate connected directly in parallel without intermediate as a submarine battery charger, generating regulated power electronics to achieve a simple structure and electrical power to allow long submerged periods. avoid conversion losses. Drawbacks of this arrange- This application imposes the strictest safety con- ment include limited ultracapacitor utilisation and straints while performing under the most demanding lack of direct control over the load profile seen by naval requirements including shock, vibration and a the PEM fuel cell. The fuel cell voltage varied from marine environment. It is also intended to combine 96 V to 75 V during operation. Control system hard- high reliability with a minimum acoustic signature to ware and software were developed in-house and are provide a stealthy performance. available as open source. The 16 kW system was Fuel cell/electrolyser systems are being actively tested both in the laboratory with an artificial load developed as a means to support astronauts on the and outdoors installed in a real forklift (Kalmar surface of the moon, as explained by Yoshitsugu Sone ECF556) utilising regenerative braking. After start-up (Japan Aerospace Exploration Agency (JAXA)). JAXA from warm indoor conditions, outdoor driving tests is developing a regenerative fuel cell system that were performed in typical southern Finnish winter can be applied to aerospace missions (Figure 5). For weather (−5ºC to −15ºC). The experimental results lunar survival, a large energy store is essential to allow direct comparison of system performance to allow for the 14 day-14 night lunar cycle. The limited the original lead-acid battery installation. energy density of the lithium-ion secondary cells Many submarines currently under construction are (currently 160–180 Wh kg−1, and likely to be less than being fitted with fuel cell power plants and existing 300 Wh kg−1 even in the future) means that over a boats are being retrofitted, following pioneering work tonne of batteries would be needed to last the lunar by Siemens in Germany and United Technologies night, even for modest power demands. Corporation in the USA. A contract has been awarded Initially,PEM fuel cell systems that can be operated by the Spanish Ministry of Defence to design, develop under isolated low-gravity and closed environments and validate an air-independent propulsion (AIP) have been studied. Subsystems and operating meth- system as part of the new S-80 submarine. This pro- ods such as closed gas circulation, with the working gramme was described by A. F.Mellinas (Navantia SA, gases in a counter-flow configuration, and a dehydra- Spain). It is intended that S-80 submarines will exhibit tor were developed to simplify assembly of the fuel many performance features currently only available cell system. Fuel cells were combined with electroly- in nuclear-powered attack boats, including three- sers and water separators to form regenerative fuel week underwater endurance and the possibility of cell systems, and the concept has been demonstrated

Charge Discharge Discharge O2 O2 Charge

Charge Discharge Discharge

ElectrolyserH2O Fuel cell H2O Unitised regenerative fuel cell Charge

Charge H2 H2 Charge Discharge Discharge

Separated type regenerative fuel cell Unitised regenerative fuel cell

Fig. 5. Schematic of the concept for a 100 W regenerative fuel cell system for use in lunar and planetary missions (Reprinted from Y. Sone, (7), with permission from Elsevier) for 1000 hours in an isolated, closed environment. possible to optimise the electrical, chemical and mass Practical performance has also been demonstrated, transfer properties of the electrodes and also reduce initially using a thermal vacuum chamber,and also in the platinum content. a stratospheric balloon in August 2008. For automotive applications of PEM fuel cells, the In addition to separate fuel cell stacks and elec- US Department of Energy has published a target trolysers, JAXA has developed a regenerative fuel platinum loading of less than 0.2 mg cm−2 for com- cell, where the polymer electrolyte fuel cell is combined anode and cathode by 2015, with performance bined with the electrolyser to fulfil both functions. characteristics equating to a platinum content of A 100 W-class regenerative fuel cell has been built 0.125 g kW−1 by this date (Figure 6). This is most and demonstrated as a breadboard model for over likely to be achieved by optimising a combination 1000 hours. A 17 cell stack of 27 cm2 electrodes pro- of parameters including catalyst, electrode and mem- vides an output of 100 W at 12 V, while in the electrol- brane structures as well as operating conditions. Ben ysis mode,‘charging’ is at 28 V. Millington (University of Birmingham, UK) described their efforts in a talk entitled ‘The Effect of Fabrication Fuel Cell Electrochemistry Methods and Materials on MEA Performance’. Various One of the main challenges facing PEM fuel cells is to methods and materials have been used in the fabri- increase the three-phase interface between catalysts, cation of catalyst coated substrates (CCSs) for mem- electrolyte and gases, in order to thrift the amount brane electrode assemblies (MEAs). Different solvents of pgm catalyst required. These catalysts are typically (ethylene glycol, glycerol, propan-2-ol, tetrahydrofu- platinum nanoparticles uniformly dispersed on porous ran and water), Nafion® polymer loadings (up to carbon support materials also of nanometre scale. In 1 mg cm−2) and anode/cathode Pt loadings have her talk entitled ‘Synthesis of New Catalyst Design for been used in the preparation of catalyst inks Proton Exchange Membrane Fuel Cell’, Anne-Claire deposited onto various gas diffusion layers (GDLs) Ferrandez (Commissariat à l’énergie atomique (CEA) sourced from E-TEK, Toray and Freudenberg, and the Le Ripault, France) described grafting polymeric syn- performance of the resulting MEAs were reported. thon to the surfaces of the platinum nanoparticles, Several methods of CCS fabrication such as painting, allowing creation of new architectures of catalyst screen printing, decal and ultrasonic spraying were layers that promote both ionic conduction between investigated. All MEAs produced were compared to the solid electrolyte and electronic conduction to the both commercial MEAs and gas diffusion electrodes carbon support. The resulting materials appear to be (GDEs). They found that MEA performance was dra- oxidation resistant and stable to voltage cycling up matically affected by the solvent type, the deposi- to +1.0 V. By adjusting synthesis parameters, it is tion method of the catalyst ink on the GDE, the GDE

Fig. 6. Status of estimated total pgm content in fuel cell stacks from 2005 to 2009 compared to DOE targets (J. Spendelow, K. Epping Martin and D. Papageorgopoulos, ‘Platinum Group Metal Loading’, DOE Hydrogen Program Record No. 9018, US Department of Energy, Washington, DC, USA, 23rd March, 2010)

type (woven or nonwoven), the drying process and Materials for Fuel Cells the amount of Nafion® added to the GDE during The pgms are also finding applications in hydrogen fabrication. Currently, the university is able to pro- generation by water electrolysis as a means of reduc- duce MEAs with similar performance to commercial ing electrode overvoltage and thereby improving products. operating efficiency. This represents not only a clean More widespread commercial development of fuel method of hydrogen production, but also an efficient cells has identified new challenges such as the effects and convenient way of storing surplus energy from of impurities in fuel supplies and the atmospheres in renewable sources such as solar,wind and hydroelec- which the devices have to operate. One of these has tric power. In his talk ‘An Investigation of Iridium been studied in detail at the Technical University of Stabilized Ruthenium Oxide Nanometer Anode Denmark, and the results were presented in a paper Catalysts for PEMWE’, Xu Wu (Newcastle University, by Syed Talat Ali entitled ‘Effect of Chloride Impurities UK) described the synthesis and characterisation on the Performance and Durability of PBI of these catalysts. The electrochemical activity of

(Polybenzimidazole)-Based High Temperature RuxIr1−xO2 materials in the range 0.6 < x < 0.8 was PEMFC’. Chlorides derived from sea salt are present in investigated. A nanocrystalline rutile structure solid the atmosphere as an aerosol in coastal areas and salt solution of iridium oxide in ruthenium oxide was is also used for deicing roads in many countries dur- identified. When x was 0.8, 0.75, and 0.7, RuxIr1−xO2 ing winter. Small traces of chlorides may originate exhibited remarkable catalytic activity,while increas- from phosphoric acid in the PBI membrane and from ing the amount of iridium resulted in improved stabil- platinum chloride precursors used to prepare some ity. A PEM water electrolysis (PEMWE) single cell platinum catalysts, while substrate carbons such as achieved a current density of 1 A cm−2 at 1.608 V with ® Cabot Vulcan XC72R carbon black contain trace Ru0.7Ir0.3O2 on the anode, a Pt/C catalyst on the impurities. The possible effect of halogen ions on cathode and Nafion® 117 as the membrane. platinum catalysts are unknown, since they may promote dissolution as complex ions, thereby enhancing Cell and Stack Technology metal oxidation and re-deposition processes. The Considerable progress has been made in develop- group’s present work is devoted to a systematic study ing high-temperature solid polymer electrolyte at temperatures from 25ºC to 180ºC. Firstly, determi- fuel cells, with particular advances in membrane nation of the chloride content of Pt-based catalysts technology. was carried out using ion chromatography. Secondly, In a keynote presentation entitled ‘High Tempera- the effect of chloride on the dissolution of a smooth ture Operation of a Solid Polymer Electrolyte Fuel Cell Pt electrode was studied in 85% phosphoric acid at Stack Based on a New Ionomer Membrane’, Antonino 70ºC using cyclic voltammetry. It was found that the S.Aricó (Consiglio Nazionale delle Ricerche – Istituto presence of chlorides is likely to be very harmful to di Tecnologie Avanzate per l’Energia (CNR-ITAE), the long-term durability of acid doped PBI-based Italy) gave details of tests on PEM fuel cell stacks as high-temperature PEM fuel cells. part of the European Commission’s Sixth Framework

Programme ‘Autobrane’ project. These were assem- fuel processing, fuel cell catalysis and sensors. There bled with Johnson Matthey Fuel Cells and SolviCore were a considerable number of posters featuring the MEAs based on the AquivionTM E79-03S short-side preparation and uses of pgm fuel cell catalysts, which chain (SSC) ionomer membrane, a chemically sta- were too numerous to mention in detail. bilised perfluorosulfonic acid membrane developed Several posters featured preparation of Pt and PtRu by Solvay Solexis (Figure 7). An in-house prepared catalysts supported on carbon nanofibres. It is evi- catalyst consisting of 50% Pt on Ketjen black was used dent that while materials such as graphitised carbon for both anode and cathode, applied at 67 wt% cata- nanofibres can be highly stable and oxidation resist- lyst with a Pt loading of 0.3 mg cm–2. Electrochemical ant, with existing catalyst preparation techniques it is experiments with fuel cell short stacks were performed difficult to make high surface area, uniform platinum under practical automotive operating conditions at dispersions which can compete with catalysts on more absolute pressures of 1–1.5 bar and temperatures conventional carbon supports such as Vulcan® XC72. ranging up to 130ºC, with relative humidity varying One poster which highlighted this difficulty was down to 18%. The stacks using large area (360 cm2) ‘Durability of Carbon Nanofiber Supported Electro- MEAs showed elevated performance in the tempera- catalysts for Fuel Cells’, by David Sebastián et al. ture range from ambient to 100ºC, with a cell power (Instituto de Carboquímica, CSIC, Spain). density in the range of 600–700 mW cm−2, with a mod- Other posters featured studies of the effects of erate decrease above 100ºC. The performances and carbon monoxide on high-temperature PEM fuel electrical efficiencies achieved at 110ºC (cell power cells, and the effects of low molecular weight density of about 400 mW cm−2 at an average cell contaminants on direct methanol fuel cell (DMFC) voltage of about 0.5–0.6 V) are promising for automo- performance. Studies are also in progress on more tive applications. Duty-cycle and steady-state galvano- fundamental aspects such as catalyst/support interac- static experiments showed excellent stack stability tions, for example ‘Investigation of Pt Catalyst/Oxide for operation at high temperature. Support Interactions’, by Isotta Cerri et al. (Toyota Motor Europe, Belgium). Poster Exhibits The poster session was combined with an evening Summary reception to maximise the time available for oral Conclusions from the Fuel Cells Science and Technol- papers and over 200 posters were offered. These ogy 2010 conference were summed up by José Luis included a wide range of applications of the pgms in García Fierro (Instituto de Catálisis y Petroleoquímica, CSIC, Spain). He remarked that the high level of interest in the conference partly reflects more strict environmental laws combined with the high prices of gas and oil (oil was US$75 per barrel at the time of the conference), emphasising the need for the best possible efficiency in utilising fuels. Biofuels appear to be making a more limited market penetration than orig- inally expected.He also mentioned that of the posters exhibited at the conference, no fewer than 45 involved PEM fuel cell catalysts and components, direct methanol and direct ethanol fuel cells. One potentially large market for fuel cells is in shipping, where marine diesel engines currently produce 4.5% of the nitrogen oxides (NOx) and 1% of particulates from all mobile sources. This becomes a sensitive issue, especially when vessels are in port. The marine market consists of some 87,000 vessels, the majority of which Fig. 7. Polymer structure of long side-chain Nafion® and short side chain AquivionTM perfluorosulfonic have propulsion units of less than 2 MWe. Among the ionomer membranes (Reprinted from A. Stassi actions currently in progress to promote exploitation et al., (7), with permission from Elsevier) of hydrogen technology and fuel cells are hydrogen

refuelling stations for vehicles together with codes 7 J. Power Sources, 2011, articles in press and standards for the retail sales of hydrogen fuel, 8 V. P. McConnell, Fuel Cells Bull., 2010, (10), 12 with support for early market opportunities. The Reviewer References Donald Cameron is an independent 1 D. S. Cameron, Platinum Metals Rev., 2003, 47, (1), 28 consultant on fuel cells and electrolysers, 2 D. S. Cameron, Platinum Metals Rev., 2005, 49, (1), 16 specialising in electrocatalysis. 3 D. S. Cameron, Platinum Metals Rev., 2007, 51, (1), 27 4 D. S. Cameron, Platinum Metals Rev., 2009, 53, (3), 147 5 The Grove Fuel Cell Symposium: http://www.grovefuelcell. com/ (Accessed on 5th January 2011) 6 Fuel Cells Science and Technology: http://www. fuelcelladvances.com/ (Accessed on 5th January 2011)

11th International Platinum Symposium

“PGE in the 21st Century: Innovations in Understanding Their Origin and Applications to Mineral Exploration and Beneficiation”

doi:10.1595/147106711X554512 http://www.platinummetalsreview.com/

Reviewed by Judith Kinnaird Every few years an International Platinum Symposium School of Geosciences, University of the Witwatersrand, is organised to provide a forum for discussion of Private Bag 3, 2050 Wits, South Africa; the geology, geochemistry, mineralogy and benefici- E-mail: [email protected] ation of major and minor platinum group element (PGE) deposits worldwide. The theme of the 11th International Platinum Symposium, which took place in Sudbury, Canada, from 21st–24th June 2010 (1), was “PGE in the 21st Century: Innovations in Understanding Their Origin and Applications to Mineral Exploration and Beneficiation”. Participants from mining and exploration companies, geological surveys, consulting companies and universities on all continents attended to listen to 85 papers and read 54 posters. Such meetings nor- mally take place every four years although it is five years since the previous meeting in Oulu, Finland in 2005, with a smaller interim meeting held in India. The organisation was impeccable throughout, for field trips, poster sessions, the social programme and the main conference. The committee was led by Professor C. Michael Lesher (Laurentian University, Canada), Edward Debicki (Geoscience Laboratories, Canada), Pedro Jugo (Laurentian University), James Mungall (University of Toronto, Canada) and Heather Brown (Ontario Geological Survey,Canada). Sudbury proved an excellent venue, a mining town that has developed into a pleasant tree-rich area that has overcome all the earlier issues of environmental degradation. Delegates were told in an overview of the global pgm industry that the Bushveld Complex in South Africa and the Norilsk deposit in Russia together account for roughly 90% of newly mined platinum and 85% of newly mined palladium supply. The Stillwater Complex in the USA is a significant source of palladium but not platinum, while the Great Dyke in Zimbabwe offers the possibility of significant expansion (Figure 1).Russian stockpiles of palladium are thought to be nearly exhausted, but recycling is growing rapidly to become another dominant source of supply. Demand for platinum, palladium and the

16ºS Fig. 1. Large-scale map of Zambesi Mobile Belt the Great Dyke in Zimbabwe, showing major lithological subdivisions Zimbabwe Snake’s Head Musengezi and areas of current craton Subchamber exploitation. The Great Dyke is the largest resource Harare 17ºS of platinum outside the Bushveld Complex of Bulawayo South Africa. Its size has encouraged active exploration and mining, Darwendale r 200 km Subchamber East Dyke e and in 2010 there were b

m three major mines in Harare a h operation and several Hartley Platinum C 18ºS Selous intensive exploration h t r initiatives (Courtesy of Mhondoro and Zinca o N A. H. Wilson and A. J. du Toit, from ‘Great Ngezi Dyke Platinum in the Region of Ngezi Mine, Zimbabwe: Characteristics of the Main Sebakwe 19ºS Sulphide Zone and Subchamber Variations that Affect Mining’, 11th International Platinum Symposium, Unki Sudbury, Ontario, Canada, 21st–24th June, 2010) r e Selukwe Mafic sequence b Ultramafic sequence Subchamber m a

h Satellite dykes

C Craton & cover rocks h Mimosa t Mobile belts u o Major faults & fractures S Wedza

East Dyke Subchamber

0 50 100

Southern satellites North Marginal Zone km 29ºEof the Limpopo Belt 31ºE other pgms is expected to grow strongly,however,and measurements, analytical techniques and results, new deposits of PGEs are of interest as possible new geochemical criteria for the identification of sources of future supply.It is therefore interesting that PGE-enriched deposits, characterisation of platinum the PGEs attract just 2% of overall global exploration group mineral assemblages and the processes that spending, which is focused on Africa, Canada and extract platinum from ore. Russia. Papers of particular interest have been collated It was therefore not surprising that several recent and summarised below, according to geographical discoveries of deposits of PGEs around the world region. All abstracts are available on the conference were discussed at this meeting, with much progress website (1). It is important to note that there are six made towards understanding their geological origins platinum group elements (PGEs): platinum, palla- and their potential for exploitation as future ore dium, rhodium, iridium, osmium and ruthenium. bodies. Existing deposits were also discussed, but data Geologists use the term ‘PGM’ to mean platinum on grades were sometimes lacking, and data were group minerals as the PGEs occur in minerals rather presented as tenors (i.e. the grade calculated in 100% than metallic form in natural deposits, whereas metal- sulfide only). Other studies focused on experimental lurgists use ‘pgm’to mean platinum group metals.

Southern Africa net-textured sulfide deposit. Disseminated Cu-Ni- The opening day of the symposium focused on South Pt-Pd sulfide mineralisation is hosted within a Africa’s Bushveld Complex and Zimbabwe’s Great tubular to tabular magma conduit with local high Dyke, as is fitting for the largest producers of platinum. grade zones (4.5 ppm Pt, 4.3 ppm Pd, 1.0% Cu For the Bushveld, chromitite layers were described and 0.6% Ni) and 14 m of higher-grade net- from at least six cyclic units of ultramafic Lower Zone textured and massive sulfide near the base of the in the northeastern limb, that have previously been intrusion which averages 16.2 ppm Pt, 13.9 ppm regarded as Marginal Zone but no platinum grades Pd, 3.5% Cu and 1.2% Ni; were given. Profiles of PGEs through chromitites in • The Eagle deposit in Michigan: a high-grade mas- the layered mafic-ultramafic suite showed that plat- sive to net-textured ore body with a reported inum per unit metre through the complex was highest resource estimated at 4.05 megatonnes (Mt) at in the north west.The atypical stratigraphic sequence an average grade of 0.73 ppm Pt, 0.47 ppm Pd, of the ‘contact-type’basal nickel-copper-PGE mineral- 2.9% Cu and 3.57% Ni; isation of the satellite Sheba’s Ridge at the western • The Tamarack deposit in Minnesota: similarly a extremity of the eastern limb is unique with discontin- high-grade massive to net-textured ore body. uous UG2 Reef and Merensky Reef analogues above All these deposits have higher Pt:Pd ratios (com- a basal ‘Platreef’-style sulfide-rich ore body with monly ≥1:1) than the ‘typical’ Duluth Complex dis- grades of <2 parts per million (ppm) Pt and <2.5 ppm seminated deposits (where ratios are typically ≤1:2). Pd and a Pt:Pd ratio typically ∼0.5, in contrast to the Such discoveries, which are regarded as analogous to UG2 and Merensky Reefs of the western and eastern Norilsk in Russia, have led to significant exploration limbs where platinum exceeds palladium.This ratio is in the region for similar conduit-style ores. similar to that for the composite Platreef of the north- In ancient Archaean rocks of northern Ontario, the ern limb, which is up to 500 m thick. The Platreef also recently discovered Eagle’s Nest Ni-Cu-PGE minerali- does not correlate closely with the Merensky Reef sation is interpreted as a feeder conduit beneath an although the Platreef was shown to be the same age. extensive complex of sills and related volcanic rocks In the Great Dyke of Zimbabwe, PGEs are con- with pools of massive sulfide at or near the lower contained in the stratiform Main Sulphide Zone near the tact. The Archaean Blackbird chromite-bearing sill top of the ultramafic succession. In this zone there is found in the James Bay Lowlands in 2008 is a sill- a consistent pattern of a lower Pd-enriched subzone hosted chromite deposit analogous to the Kemi (Pt:Pd ratio of 0.7:1) with Pd <2 ppm and an upper deposit in Finland. The chromitites have no sulfides, Pt-enriched subzone (Pt:Pd ratio of 2.5:1) with values and PGE grades are low. of Pt up to 4 ppm, which are separated by a narrow Canada’s East Bull Lake intrusive suite hosts sever- transition zone. al contact-style Cu-Ni-PGE occurrences within several of the larger intrusions, most notably in the River North America and Canada Valley area. Grades of up to 25 parts per billion (ppb) The Midcontinent Rift in North America, which has Pt and 33 ppb Pd were described for some of the been known for its undeveloped low-grade dissemi- intrusions. nated deposits, may become the next major Cu-Ni- The West Raglan Ni-Cu-PGE project, in the early PGE mining district as several new,higher-grade dis- Proterozoic Cape Smith Fold Belt of northern coveries have been made which together have in situ Quebec, hosts several economic Ni-Cu-PGE sulfide metal values over US$325 billion. The bulk of these deposits (such as Xstrata’s Raglan deposits) and sev- resources have been discovered in or near the eral more recent discoveries (Goldbrook Ventures’ Duluth Complex in northeastern Minnesota, USA, Mystery prospect and Canadian Royalties’ Mesamax and include the following: deposit, for example). Nickel sulfide deposits are • The Nokomis deposit: a large, PGE-rich dissemi- spatially associated with mafic-ultramafic sills and nated sulfide deposit with a reported estimate of intrusive complexes. Since 2003, drilling of the 5 million ounces of Pt and nearly 10 million Raglan trend has identified several discrete miner- ounces of Pd; alised lenses at West Raglan which include a 36.43 m • The Current Lake Complex near Thunder Bay interval at a grade of 2.54 ppm PGEs, 1.1% Cu and in Ontario, Canada: a Pt-rich disseminated to 2.66% Ni.

The PGE deposits of the Lac des Iles Complex in New information on the geology and PGE mineral- Canada (the Roby, Twilight and High-Grade Zones) isation of two other intrusions of the Kola region was differ from most other PGE deposits as they occur in presented. The Volchetundra layered mafic intrusion a small, concentrically-zoned mafic intrusion rather is 40 km long and 2–4 km wide, with marginal and than in a large layered intrusion and the ore zone is irregular sulfide-rich lenses in the steeply-dipping ∼900 m by 700 m in size and open at depth rather eastern contact zone. These are up to 30 m thick with than thin and tabular. Pentlandite controls 30% of PGE grades ranging from 0.1–3.7 ppm (typically whole-rock palladium, the rest is present as PGMs. 0.1–0.3 ppm) and Pd:Pt ratios from 2–5, although In spite of more than a century of mining in the sulfide-rich pods with higher-grade (up to 5 ppm) Sudbury district of Canada, new discoveries are still PGEs have been delineated. In addition, reef-type being made. The principal styles of Cu-Ni sulfide mineralisation in layered gabbro-gabbronorite of the mineralisation that have been mined are: Main Zone is 1–18 m thick, with low to no sulfides, (a) in the Sublayer at the lower contact of the PGE grades from 2–20 ppm and Pd:Pt ratios of 0.4–1. Sudbury Igneous Complex; The lenticular shaped Monchatundra layered intru- (b) in quartz diorite Offset Dykes (with grades of <10 sion extends over almost 500 km2 and ranges in com- ppm Pt and <10 ppm Pd); and position from dunite to anorthosite. The ‘Frequently (c) the Frood-Stobie Breccia Belt. Interlayered Zone’ within the mafic-ultramafic part However, in the past 20 years, there has been a pro- of the intrusion has disseminated sulfides (usually gressive shift towards mining footwall deposits that 0.5–2%, but locally up to 30%) and PGE mineralisa- are enriched in Cu, Ni and PGEs. The recently recog- tion. The zone varies up to 130 m in thickness but nised ‘low-sulfide’ Cu-Ni-PGE systems represent the the ore-bearing interval ranges from 0.3 m to 42 m, most Pt- and Pd-enriched mineralisation type within typically between 3 m and 18 m. The PGE grade the footwall in the North and East Ranges of the 1.85 varies between 1.5–3.5 ppm with Pd:Pt ratios of 1.5–3. Ga complex (Figure 2(a)).When present, mineralisa- Several papers reviewed aspects of the world class tion is generally peripheral to footwall deposits and Cu-Ni-PGE deposits of the Norilsk mafic-ultramafic can also occur in the footwall immediately adjacent intrusions in Siberia. All important resources are to Cu-rich portions of the offset ore bodies. The concentrated in three intrusions: the Talnakh, newly-discovered Capre 3000 mineralised zone in the Kharaelakh, and Norilsk 1 (Krivolutskaya) massifs. East Range has PGE abundances similar to other The newly-discovered Cu-Ni-PGE Maslovskoe deposit North Range footwall vein-style systems. These are in the north of the Norilsk Trough comprises a associated with sulfides at a brecciated contact Northern intrusion which is very similar to the between granite and gneiss. In the South Range, the Norilsk 1 massif and may be a southwest branch, and 109 FW Zone low-sulfide deposit is a new discovery a separate Southern Maslovsky intrusion.Both massifs in the footwall of the Crean Hill Mine adjacent to a contain disseminated ores and veins and belong to previously exploited contact sulfide deposit (Figure the Norilsk Intrusive Complex.The veinlet-disseminat- 2(b)). ed ores of the Northern Maslovskoe deposit are enriched in up to 25 ppm PGEs. Russia and Northern Finland The Kemi intrusion in northern Finland hosts the China largest economic chrome deposits outside the The Jinchuan nickel-copper deposit is the third largest Bushveld Complex but PGEs are low in abundance, magmatic sulfide deposit in the world. It occurs in a with a maximum combined Pt and Pd grade of <50 small, dyke-like ultramafic intrusion (6500 m × 400 m × ppb and typical grades ranging between about 20–30 1100 m) in the western margin of the Northern China ppb in the lower half and <10 ppb in the upper half Craton. Mineralisation is disseminated, net textured of the intrusion. By contrast, the Kievey ore body in or massive according to sulfide content. PGE abun- the Fedorovo-Pansky layered mafic intrusion of the dances are given in Table I. Kola Peninsula in Russia has a combined Pt, Pd and Au grade varying from 0.8 ppm to 18.2 ppm Brazil (Pd:Pt = 6.7) with an average Cu grade of 0.15% and Several favourable settings for Ni-Cu-PGE deposits Ni grade of 0.13%. in Brazil include numerous large layered intrusions

(a) Surface

D A Contact B Footwall type A C Low sulfide D Capre footwall New discovery

C Massive sulfide Low sulfide PGE-Au Disseminated Ni sulfide Undifferentiated gneiss B Granite breccia Sudbury breccia Sudbury igneous complex Diabase 0 250 Granite Fault m

(b) Surface

A A Contact C B Footwall type C Breccia belt type D 109 FW B New discovery

0 100

Inclusion massive/ Low sulfide, high PGE breccia sulfide mineralisation Sudbury breccia Norite Siliceous zone Metasediments Granite Trap dyke Disseminated Ni-Cu sulfide Metavolcanic Quartz diorite Shear zone

Fig. 2. Composite cross-sections of typical geological settings for Footwall Deposits of PGEs and sulfide in the Sudbury Igneous Complex, Canada, in (a) the North and East Range and (b) the South Range (Courtesy of P. C. Lightfoot and M. C. Stewart, from ‘Diversity in Platinum Group Element (PGE) Mineralization at Sudbury: New Discoveries and Process Controls’, 11th International Platinum Symposium, Sudbury, Ontario, Canada, 21st–24th June, 2010)

Table I Platinum Group Element Abundances of the Jinchuan Deposit in China

Ore type Platinum Palladium Rhodium Iridium Ruthenium grade, ppb grade, ppb grade, ppb grade, ppb grade, ppb

Disseminated 35.8–853 74.8–213 2.5–19.5 5.1–38.5 4.2–33.1 Net-textured 12.7–1757a 171–560 0.7–5.1 0.4–4.0 1.5–3.5 Massive 11.6–102 218–1215 78.1–201 211–644 91–553 aOne exceptional occurrence of 3343 ppb in cratonic areas, several clusters or lineaments New Discoveries of mafic and mafic-ultramafic intrusions where New Cu-Au-PGE mineralisation was reported from the feeder dykes and the lowermost parts of layered Togeda macrodyke in the Kangerlussuaq region of intrusions are exposed, a continental-scale province East Greenland. A metasediment-hosted deposit from of flood basalts,and several areas of extensive komati- Craignure, Inverary,in Scotland hosts sulfide mineral- itic magmatism in Precambrian greenstone belts. isation with PGE concentrations locally exceeding The Fortaleza de Minas komatiite-hosted Ni-Cu 3 ppm and, although small, this raises the possibility deposit is quoted as an estimated resource of 6 Mt at of other metasediment-hosted Ni-Cu-PGE mineralisa- grades of 0.7 ppm combined Pt, Pd and Au, 0.4% Cu tion in Scotland. Amphibolites and their weathered and 2.5% Ni. The layered mafic-ultramafic lithologies equivalents on the northwest border of the Congo of the Tróia Unit of the Cruzeta Complex in north- Craton in South Cameroon have a PGEs plus Au con- eastern Brazil have been the focus of platinum explo- tent of 53 ppb to 121 ppb. The Pd:Pt ratios are ∼ 3. ration for more than 30 years. Local chromitite Ni-Cu-PGE mineralisation was described from the horizons, 0.3 m to 3 m thick, contain up to 8 ppm Pt Gondpipri area of central India but Ni and Cu domi- and 21 ppm Pd. nate and PGE content is low.

Other Occurrences Process Mineralogy in the Platinum Komatiite-hosted Ni-Cu deposits with PGEs from Industry and Future Trends Australia and Canada were discussed. PGE-bearing This was perhaps a new topic for these events. chromitites from eastern Cuba and elsewhere were Laser ablation inductively coupled plasma mass described. Data from the Al’Ays ophiolite complex in spectrometry (LA-ICP-MS) mapping provides critical Saudi Arabia have shown that podiform chromitites information on the distribution of the PGEs in and with high PGE concentrations (above 1.4 ppm) also around magmatic sulfides and is useful in charac- have distinctive minor element concentrations that terising PGE deposits. As an example of the insights provide an improved fingerprint for further explo- that can be gained with this technique, new data ration. The Ambae chromites of the Vanuatu Arc in for samples from the Merensky Reef and Norilsk- the south-west Pacific have grades of 75.8 ppb Rh, Talnakh show that the behaviour of Pt is very differ- 52.1 ppb Ir, 36.8 ppb Os and 92.6 ppb Ru, whereas ent from that of Pd and Rh, which are generally Pd, Pt and Au are below the detection limit. These hosted by pentlandite. Pt often forms a plethora of values account for 56% of the Ir, over 90% of the discrete phases in association with the trace and Ru and 22% of the Rh present in the Ambae lavas. semi-metals. The variable distribution of these phases Reconnaissance studies of the PGEs potential of four has implications for geometallurgical models and chromite mining districts in southern Iran showed PGE recoveries. that chromites have concentrations of 6 PGEs (com- While the PGEs are most often concentrated in bined Pt, Pd, Rh, Ir, Os and Ru) from 57 ppb to sulfide minerals such as pyrrhotite, pentlandite and 5183 ppb with an average of 456 ppb. chalcopyrite, there were several reports at the

symposium of pyrite hosting appreciable amounts of process behind the formation of PGE deposits is Rh and Pt. Pyrite from the McCreedy and Creighton gained. deposits of Sudbury has a similar Os, Ir, Ru, Re (rhenium) and Se (selenium) content to that of coex- isting pyrrhotite and pentlandite, whereas Rh (at up Reference to 130 ppm), arsenic (up to 30 ppm), Pt and Au show 1 The 11th International Platinum Symposium at Laurentian a stronger preference for pyrite than for pyrrhotite or University: http://11ips.laurentian.ca/Laurentian/Home/ Departments/Earth+Sciences/NewsEvents/11IPS/ (Accessed pentlandite. In the Canadian Cordilleran porphyry on 7th January 2011) copper systems, up to 90% of the Pd and Pt in mineralised samples occurs in pyrite. The Reviewer Judith Kinnaird is a Professor of Concluding Remarks Economic Geology at the School of With reports of a number of new discoveries along- Geosciences at the University of the Witwatersrand, South Africa, and side much new information on existing resources, Deputy Director of the University’s the 11th International Platinum Symposium pro- Economic Geology Research Institute (EGRI). Her research interests include vided the industry with the most comprehensive Bushveld Complex magmatism and overview yet of platinum group element deposits mineralisation especially of the Platreef in the northern limb, while worldwide. While many of these deposits have rela- her research team is currently tively low grades of PGEs, they may still prove to be conducting studies on chromitite geochemistry, mineralogy and PGE viable and valuable sources of pgms in the future. grade distribution; tenor variations; Exploration efforts are also expected to become more zircon age-dating; Lower Zone mineralogy and geochemistry of the efficient as a greater understanding of the geological Bushveld Complex in South Africa.

The Discoverers of the Rhodium Isotopes The thirty-eight known rhodium isotopes found between 1934 and 2010

doi:10.1595/147106711X555656 http://www.platinummetalsreview.com/

By John W. Arblaster This is the fifth in a series of reviews on the circum- stances surrounding the discoveries of the isotopes Wombourne, West Midlands, UK; of the six platinum group elements. The first review E-mmail: [email protected] on platinum isotopes was published in this Journal in October 2000 (1), the second on iridium isotopes in October 2003 (2), the third on osmium isotopes in October 2004 (3) and the fourth on palladium isotopes in April 2006 (4).

Naturally Occurring Rhodium In 1934, at the University of Cambridge’s Cavendish Laboratory,Aston (5) showed by using a mass spectrograph that rhodium appeared to consist of a single nuclide of mass 103 (103Rh). Two years later Sampson and Bleakney (6) at Princeton University,New Jersey, using a similar instrument, suggested the presence of a further isotope of mass 101 (101Rh) with an abundance of 0.08%. Since this isotope had not been discovered at that time, its existence in nature could not be discounted. Then in 1943 Cohen (7) at the University of Minnesota used an improved mass spectrograph to show that the abundance of 101Rh must be less than 0.001%. Finally in 1963 Leipziger (8) at the Sperry Rand Research Center, Sudbury, Massachusetts, used an extremely sensitive double-focusing mass spectrograph to reduce any possible abundance to less than 0.0001%. However by that time 101Rh had been discovered (see Table I) and although shown to be radioactive, no evidence was obtained for a long- lived isomer. This demonstrated conclusively that rhodium does in fact exist in nature as a single nuclide: 103Rh.

Artificial Rhodium Isotopes In 1934, using slow neutron bombardment, Fermi et al. (9) identified two rhodium activities with half- lives of 50 seconds and 5 minutes. A year later the same group (10) refined these half-lives to 44 seconds and 3.9 minutes. These discoveries were said to be ‘non-specific’ since the mass numbers were not

determined, although later measurements identified were identified are considered as satisfying the dis- these activities to be the ground state and isomeric covery criteria. state of 104Rh, respectively. In 1940 Nishina et al. (11, 12), using fast neutron bombardment, identified Discovery Dates a 34 hour non-specific activity which was later identi- The actual year of discovery is generally considered fied as 105Rh. In 1949 Eggen and Pool (13) confirmed to be that when the details of the discovery were the already known nuclide 101Pd and identified the placed in the public domain, such as manuscript existence of a 4.7 day half-life rhodium daughter dates or conference report dates. However, complica- product. They did not comment on its mass although tions arise with internal reports which may not be the half-life is consistent with the isomeric state of placed in the public domain until several years after 101Rh. Eggen and Pool also identified a 5 hour half-life the discovery,and in these cases it is considered that activity which was never subsequently confirmed. the historical date takes precedence over the public Activities with half-lives of 4 minutes and 1.1 hours, domain date. Certain rhodium isotopes were discov- obtained by fast neutron bombardment, were identi- ered during the highly secretive Plutonium Project of fied by Pool, Cork and Thornton (14) in 1937 but the Second World War, the results of which were not these also were never confirmed. actually published until 1951 (16) although much of Although some of these measured activities repre- the information was made available in 1946 by Siegel sent the first observations of specific nuclides, the (17, 18) and in the 1948 “Table of Isotopes”(19). exact nuclide mass numbers were not determined and therefore they are not considered to represent Half-Lives actual discoveries. They are however included in Selected half-lives used in Table I are generally those the notes to Table I. The first unambiguous identifi- accepted in the revised NUBASE evaluation of cation of a radioactive rhodium isotope was by nuclear and decay properties in 2003 (20) although Crittenden in 1939 (15) who correctly identified literature values are used when the NUBASE data are both 104Rh and its principal isomer. Nuclides where not available or where they have been superseded by only the atomic number and atomic mass number later determinations.

Table I The Discoverers of the Rhodium Isotopes

Mass numbera Half-llife Decay Year of Discoverers References Notes modes discovery

89 psb EC + β+ ? 1994 Rykaczewski et al. 21, 22 90 15 ms EC + β+ 1994 Hencheck et al.23A 90m 1.1 s EC + β+ 2000 Stolz et al.24A 91 1.5 s EC + β+ 1994 Hencheck et al.23B 91m 1.5 s IT 2004 Dean et al.25B 92 4.7 s EC + β+ 1994 Hencheck et al.23C 92m 0.5 s IT? 2004 Dean et al.25C 93 11.9 s EC + β+ 1994 Hencheck et al.23D 94 70.6 s EC + β+ 1973 Weiffenbach, Gujrathi and Lee 26 94m 25.8 s EC + β+ 1973 Weiffenbach, Gujrathi and Lee 26 95 5.02 min EC + β+ 1966 Aten and Kapteyn 27 95m 1.96 min IT, EC + β+ 1974 Weiffenbach, Gujrathi and Lee 28 Continued

Table I The Discoverers of the Rhodium Isotopes (Continued)

Mass numbera Half-llife Decay Year of Discoverers References Notes modes discovery

96 9.90 min EC + β+ 1966 Aten and Kapteyn 27 96m 1.51 min IT, EC + β+ 1966 Aten and Kapteyn 27 97 30.7 min EC + β+ 1955 Aten and de Vries-Hamerling 29 97m 46.2 min EC + β+, IT 1971 Lopez, Prestwich and Arad 30 98 8.7 min EC + β+ 1955 Aten and de Vries-Hamerling 29 E 98m 3.6 min EC + β+ 1966 Aten and Kapteyn 31 99 16.1 d EC + β+ 1956 Hisatake, Jones and Kurbatov 32 F 99m 4.7 h EC + β+ 1952 Scoville, Fultz and Pool 33 100 20.8 h EC + β+ 1944 Sullivan, Sleight and Gladrow 34, 35 G 100m 4.6 min IT, EC + β+ 1973 Sieniawski 36 101 3.3 y EC 1956 Hisatake, Jones and Kurbatov 32 F 101m 4.34 d EC, IT 1944 Sullivan, Sleight and Gladrow 34, 37 G 102 207.0 d EC + β+, β− 1941 Minakawa 38 102m 3.742 y EC + β+, IT 1962 Born et al.39 103 Stable – 1934 Aston 5 103m 56.114 min IT 1943 (a) Glendenin and Steinberg (a) 40, 41 H (b) Flammersfeld (b) 42 104 42.3 s β− 1939 Crittenden 15 I 104m 4.34 min IT, β− 1939 Crittenden 15 I 105 35.36 h β− 1944 (a) Sullivan, Sleight and Gladrow (a) 34, 43 J (b) Bohr and Hole (b) 44 105m 42.9 s IT 1950 Duffield and Langer 45 106 30.1 s β− 1943 (a) Glendenin and Steinberg (a) 40, 41 K (b) Grummitt and Wilkinson (b) 46 (c) Seelmann-Eggebert (c) 47 106m 2.18 h β− 1955 Baró, Seelmann-Eggebert 48 L and Zabala 107 21.7 min β− 1954 (a) Nervik and Seaborg (a) 49 M (b) Baró, Rey and (b) 50 Seelmann-Eggebert 108 16.8 s β− 1955 Baró, Rey and 50 N Seelmann-Eggebert 108m 6.0 min β− 1969 Pinston, Schussler and Moussa 51

Continued

Table I The Discoverers of the Rhodium Isotopes (Continued)

Mass numbera Half-llife Decay Year of Discoverers References Notes modes discovery

109 1.33 min β− 1969 Wilhelmy et al. 52, 53 110 28.5 s β− 1969 (a) Pinston and Schussler (a) 54 (b) Ward et al. (b) 55 110m 3.2 s β− 1963 Karras and Kantele 56 111 11 s β− 1975 Franz and Herrmann 57 112 3.4 s β− 1969 Wilhelmy et al. 52, 53 112m 6.73 s β− 1987 Äystö et al.58 113 2.80 s β− 1988 Penttilä et al.59 114 1.85 s β− 1969 Wilhelmy et al. 52, 53 114m 1.85 s β− 1987 Äystö et al.58 115 990 ms β− 1987 Äystö et al. 60, 61 116 680 ms β− 1987 Äystö et al. 58, 60, 61 116m 570 ms β− 1987 Äystö et al. 58, 60, 61 117 394 ms β− 1991 Penttilä et al.62 118 266 ms β− 1994 Bernas et al.63O 119 171 ms β− 1994 Bernas et al.63P 120 136 ms β− 1994 Bernas et al.63Q 121 151 ms β− 1994 Bernas et al.63P 122 psb β− ? 1997 Bernas et al.64 123 psb β− ? 2010 Ohnishi et al. 65 See Figures 1 and 2 124 psb β− ? 2010 Ohnishi et al. 65 See Figures 1 and 2 125 psb β− ? 2010 Ohnishi et al. 65 See Figures 1 and 2 126 psb β− ? 2010 Ohnishi et al. 65 See Figures 1 and 2 am = isomeric state bps = particle stable (resistant to proton and neutron decay)

Fig. 1. The superconducting ring cyclotron (SRC) in the Radioactive Isotope Beam Factory (RIBF) at the RIKEN Nishina Center for Accelerator-Based Science where the newest isotopes of palladium, rhodium and ruthenium were discovered (65) (Copyright 2010 RIKEN)

Dr Toshiyuki Kubo Toshiyuki Kubo is the team leader of the Research Group at RIKEN. He was born in Tochigi, Japan, in 1956. He received his BS degree in Physics from The University of Tokyo in 1978, and his PhD degree from the Tokyo Institute of Technology in 1985. He joined RIKEN as an Assistant Research Scientist in 1980, and was promoted to Research Scientist in 1985 and to Senior Research Scientist in 1992. He spent time at the National Superconducting Cyclotron Laboratory of Michigan State University in the USA as a visiting physicist from 1992 to 1994. In 2001, he became the team leader for the in-flight separator, dubbed ‘BigRIPS’, which analyses the frag- ments produced in the RIBF.He was promoted to Group Director of the Research Instruments Group at the RIKEN Nishina Center in 2007. He is in charge of the design, construction, development and operation of major research instruments, as well as related infrastructure and equipment, at the RIKEN Nishina Center. His current Fig. 2. Dr Toshiyuki Kubo research focuses on the production of rare isotope beams, in-flight (Copyright 2010 RIKEN) separator issues, and the structure and reactions of exotic nuclei.

Notes to Table I

A 90Rh and 90mRh Hencheck et al. (23) only proved that the isotope was particle stable. Stolz et al. (24) in 2000 identified both the ground state and an isomer. The half-life determined by Wefers et al. in 1999 (66) appears to be consistent with the ground state. The discovery by Hencheck et al. is nominally assigned to the ground state. B 91Rh and 91mRh Hencheck et al. (23) only proved that the isotope was particle stable. Wefers et al. (66) first determined a half-life in 1999 but Dean et al. (25) remeasured the half- life in 2004 and identified both a ground state and an isomer having identical half-lives within experimental limits. The discovery by Hencheck et al. is nominally assigned to the ground state. C 92Rh and 92mRh Hencheck et al. (23) only proved that the isotope was particle stable. Wefers et al. (66) incorrectly determined the half-life in 1999 with more accurate values being determined by both Górska et al. (67) and Stolz et al. (24) in 2000. Dean et al. (25) showed that these determinations were for the ground state and not for the isomeric state which they also identified. The discovery by Hencheck et al. is nominally assigned to the ground state. D 93Rh Hencheck et al. (23) only proved that the isotope was particle stable. Wefers et al. in (66) incorrectly measured the half-life in 1999 with more accurate values being obtained by both Górska et al. (67) and Stolz et al. (24) in 2000. E 98Rh Aten et al. (68) observed this isotope in 1952 but could not decide if it was 96Rh or 98Rh. F 99Rh and 101Rh Farmer (69) identified both of these isotopes in 1955 but could not assign mass numbers. G 100Rh and 101mRh For these isotopes the 1944 discovery by Sullivan, Sleight and Gladrow (34) was not made public until its inclusion in the 1948 “Table of Isotopes” (19). H 103mRh Although both Glendenin and Steinberg (40) and Flammersfeld (42) discovered the isomer in 1943 the results of Glendenin and Steinberg were not made public until their inclusion in the 1946 table compiled by Siegel (17, 18). I 104Rh and 104mRh Both the ground state and isomer were first observed by Fermi et al. (9) in 1934 and by Amaldi et al. (10) in 1935 as non-specific activities. Pontecorvo (70, 71) discussed these activities in detail but assigned them to 105Rh. EC + β+ was also detected as a rare decay mode (0.45% of all decays) in 104Rh by Frevert, Schöneberg and Flammersfeld (72) in 1965. J 105Rh For this isotope the 1944 discovery by Sullivan, Sleight and Gladrow (34) was not made public until its inclusion in the 1946 table of Siegel (17, 18). The isotope was first identified by Nishina et al. (11, 12) in 1940 as a non-specific activity. K 106Rh The discovery by Glendenin and Steinberg (40) in 1943 was not made public until

Continued

Notes to Table I (Continued)

its inclusion in the 1946 table of Siegel (17, 18) and therefore the discovery of this isotope by both Grummitt and Wilkinson (46) and Seelmann-Eggebert (47) in 1946 are considered to be independent. L 106mRh Nervik and Seaborg (49) also observed this isotope in 1955 but tentatively assigned it to 107Rh. M 107Rh First observed by Born and Seelmann-Eggebert (73) in 1943 as a non-specific activity and also tentatively identified by Glendenin (74, 75) in 1944. N 108Rh Although credited with the discovery, the claim by Baró, Rey and Seelmann- Eggebert (50) is considered to be tentative and a more definite claim to the discovery was made by Baumgärtner, Plata Bedmar and Kindermann (76) in 1957. O 118Rh Bernas et al. (63) only confirmed that the isotope was particle stable. The half-life was first determined by Jokinen et al. (77) in 2000. P 119Rh and 121Rh Bernas et al. (63) only confirmed that the isotopes were particle stable. The half- lives were first determined by Montes et al. (78) in 2005. Q 120Rh Bernas et al. (63) only confirmed that the isotope was particle stable. The half-life was first determined by Walters et al. (79) in 2004.

Some of the Terms Used for This Review

Atomic number The number of protons in the nucleus. Mass number The combined number of protons and neutrons in the nucleus. Nuclide and isotope A nuclide is an entity containing a unique number of protons and neutrons in the nucleus. For nuclides of the same element the number of protons remains the same but the number of neutrons may vary. Such nuclides are known collectively as the isotopes of the element. Although the term isotope implies plurality it is sometimes used loosely in place of nuclide. Isomer/isomeric state An isomer or isomeric state is a high energy state of a nuclide which may decay by isomeric transition (IT) as described in the list of decay modes below, although certain low-lying states may decay independently to other nuclides rather than the ground state. Half-life The time taken for the activity of a radioactive nuclide to fall to half of its previous value. Electron volt (eV) The energy acquired by any charged particle carrying a unit (electronic) charge when it falls through a potential of one volt, equivalent to 1.602 × 10–19 J. The more useful unit is the mega (million) electron volt (MeV).

Decay Modes

α Alpha decay is the emission of alpha particles which are 4He nuclei. Thus the atomic number of the daughter nuclide is two lower and the mass number is four lower. β– Beta or electron decay for neutron-rich nuclides is the emission of an electron (and an anti-neutrino) as a neutron in the nucleus decays to a proton. The mass number of the daughter nuclide remains the same but the atomic number increases by one. β+ Beta or positron decay for neutron-deficient nuclides is the emission of a positron (and a neutrino) as a proton in the nucleus decays to a neutron. The mass number of the daughter nuclide remains the same but the atomic number decreases by one. However this decay mode cannot occur unless the decay energy exceeds 1.022 MeV (twice the electron mass in energy units). Positron decay is always associated with orbital electron capture (EC). EC Orbital electron capture in which the nucleus captures an extranuclear (orbital) electron which reacts with a proton to form a neutron and a neutrino, so that, as with positron decay, the mass number of the daughter nuclide remains the same but the atomic number decreases by one. IT Isomeric transition in which a high energy state of a nuclide (isomeric state or isomer) usually decays by cascade emission of γ (gamma) rays (the highest energy form of electromagnetic radiation) to lower energy levels until the ground state is reached. p Proton decay in which a proton is emitted from the nucleus so both the atomic number and mass number decrease by one. Such a nuclide is said to be ‘particle unstable’. n Neutron decay in which a neutron is emitted from the nucleus so the atomic number remains the same but the atomic mass is decreased by one. Such a nuclide is said to be ‘particle unstable’.

Erratum: In the previous reviews (1–4) the alpha and beta decay modes were described in terms of ‘emittance’. This should read ‘emission’.

References F. Rasetti and E. Segrè, Proc. R. Soc. Lond. A, 1935, 149, 1 J. W. Arblaster, Platinum Metals Rev., 2000, 44, (4), 173 522 2 J. W. Arblaster, Platinum Metals Rev., 2003, 47, (4), 167 11 Y. Nishina, T. Yasaki, K. Kimura and M. Ikawa, Phys. Rev., 3 J. W. Arblaster, Platinum Metals Rev., 2004, 48, (4), 173 1941, 59, (3), 323 4 J. W. Arblaster, Platinum Metals Rev., 2006, 50, (2), 97 12 Y. Nishina, T. Yasaki, K. Kimura and M. Ikawa, Phys. Rev., 1941, 59, (8), 677 5 F. W. Aston, Nature, 1934, 133, (3366), 684 13 D. T. Eggen and M. L. Pool, Phys. Rev., 1949, 75, (9), 6 M. B. Sampson and W. Bleakney, Phys. Rev., 1936, 50, 1465 (8), 732 14 M. L. Pool, J. M. Cork and R. L. Thornton, Phys. Rev., 7 A. A. Cohen, Phys. Rev., 1943, 63, (5–6), 219 1937, 52, (3), 239 8 F. D. Leipziger, Appl. Spectrosc., 1963, 17, (6), 158 15 E. C. Crittenden, Jr., Phys. Rev., 1939, 56, (8), 709 9 E. Fermi, E. Amaldi, O. D’Agostino, F. Rasetti and 16 “Radiochemical Studies: The Fission Products”, eds. C. D. E. Segrè, Proc. R. Soc. Lond. A, 1934, 146, 483 Coryell and N. Sugarman, National Nuclear Energy 10 E. Amaldi, O. D’Agostino, E. Fermi, B. Pontecorvo, Series, Plutonium Project Record, Division IV, Vol. 9,

McGraw-Hill, New York, USA, 1951, in 3 volumes 32 K. Hisatake, J. T. Jones and J. D. Kurbatov, Bull. Am. Phys. 17 J. M. Siegel, Rev. Mod. Phys., 1946, 18, (4), 513 Soc., 1956, 1, (5), 271 18 J. M. Siegel, J. Am. Chem. Soc., 1946, 68, (11), 2411 33 C. L. Scoville, S. C. Fultz and M. L. Pool, Phys. Rev., 1952, 85, (6), 1046 19 G. T. Seaborg and I. Perlman, Rev. Mod. Phys., 1948, 20, (4), 585 34 W. H. Sullivan, N. R. Sleight and E. M. Gladrow, National Nuclear Energy Series, Division IV, Plutonium Project 20 G. Audi, O. Bersillon, J. Blachot and A. H. Wapstra, Nucl. Report CC-1493, March 1944 Phys. A, 2003, 729, (1), 3 35 W. H. Sullivan, N. R. Sleight and E. M. Gladrow, Paper 21 K. Rykaczewski, R. Anne, G. Auger, D. Bazin, C. Borcea, 332: ‘Discovery and Characterization of 21h Rh(100) in V. Borrel, J. M. Corre, T. Dörfler, A. Fomichov, R. Grzywacz, Deuteron-Bombarded Ruthenium’, in “Radiochemical D. Guillemaud-Mueller, R. Hue, M. Huyse, Z. Janas, Studies: The Fission Products”, eds. C. D. Coryell and H. Keller, M. Lewitowicz, S. Lukyanov, A. C. Mueller, Yu. N. Sugarman, Vol. 3, National Nuclear Energy Series, Penionzhkevich, M. Pfützner, F. Pougheon, M. G. Saint- Plutonium Project Record, Division IV, Vol. 9, McGraw-Hill, Laurent, K. Schmidt, W. D. Schmidt-Ott, O. Sorlin, New York, 1951, pp. 1953–1957 J. Szerypo, O. Tarasov, J. Wauters and J. Zylicz, Phys. Rev. C, 1995, 52, (5), R2310 36 J. Sieniawski, Acta Phys. Pol. B, 1974, 5, (4), 549 37 W. H. Sullivan, N. R. Sleight and E. M. Gladrow, Paper 22 M. Lewitowicz, R. Anne, G. Auger, D. Bazin, C. Borcea, (101) V. Borrel, J. M. Corre, T. Dörfler, A. Fomichov, R. Grzywacz, 331: ‘Discovery of 5.9d Rh in Deuteron-Bombarded D. Guillemaud-Mueller, R. Hue, M. Huyse, Z. Janas, H. Keller, Ruthenium’, in “Radiochemical Studies: The Fission S. Lukyanov, A. C. Mueller, Yu. Penionzhkevich, M. Pfützner, Products”, eds. C. D. Coryell and N. Sugarman, Vol. 3, F. Pougheon, K. Rykaczewski, M. G. Saint-Laurent, National Nuclear Energy Series, Plutonium Project K. Schmidt, W. D. Schmidt-Ott, O. Sorlin, J. Szerypo, Record, Division IV, Vol. 9, McGraw-Hill, New York, O. Tarasov, J. Wauters and J. Zylicz, Nucl. Phys. A, 1995, 1951, pp. 1949–1952 588, (1), c197 38 O. Minakawa, Phys. Rev., 1941, 60, (9), 689 23 M. Hencheck, R. N. Boyd, M. Hellström, D. J. Morrisey, 39 P. Born, A. Veefkind, W. H. Elsenaar and J. Blok, Physica, M. J. Balbes, F. R. Chloupek, M. Fauerbach, C. A. 1963, 29, 535 Mitchell, R. Pfaff, C. F. Powell, G. Raimann, B. M. Sherrill, 40 L. E. Glendenin and E. P. Steinberg, National Nuclear M. Steiner, J. Vandegriff and S. J. Yennello, Phys. Rev. C, Energy Series, Division IV, in Plutonium Project Report 1994, 50, (4), 2219 CC-579, April 1943, p. 11 and in Plutonium Project 24 A. Stolz, E. Wefers, T. Faestermann, R. Schniedner, Report CC-680, May 1943, p. 9 K. Sümmerer, J. Friese, H. Geissel, M. Hellström, P. Kienle, 41 L. E. Glendenin and E. P. Steinberg, Paper 103: ‘Long- H.-J. Körner, M. Münch, G. Münzenberg, Ch. Schlegel, Lived Ruthenium-Rhodium Chains in Fission’, in P. Thirolf and H. Weick, ‘Decay Studies of N ≈ Z Nuclei “Radiochemical Studies: The Fission Products”, eds. 77 100 From Y to Sn’, in “Proceedings PINGST2000”, eds. C. D. Coryell and N. Sugarman, Vol. 2, National Nuclear D. Rudolf and M. Hellström, Proceedings of the Energy Series, Plutonium Project Record, Division IV, International Workshop PINGST2000: Selected Topics on Vol. 9, McGraw-Hill, New York, 1951, pp. 793–804 N = Z Nuclei, Lund, Sweden, 6th–10th June, 2000, 42 A. Flammersfeld, Naturwissenschaften, 1944, 32, (1–4), 36 Nuclear Structure Group Lund University, Sweden, 2000, pp. 113–117: http://pingst2000.nuclear.lu.se/proceedings. 43 W. H. Sullivan, N. R. Sleight and E. M. Gladrow, Paper asp (Accessed on 13th January 2011) 107: ‘Identification and Mass Assignment of 4.5h Ru105–36.5h Rh105 Decay Chain in Neutron- and 25 S. Dean, M. Górska, F. Aksouh, H. de Witte, M. Facina, Deuteron-Bombarded Ruthenium’, in “Radiochemical M. Huyse, O. Ivanov, K. Krouglov, Yu. Kudryavtsev, I. Mukha, Studies: The Fission Products”, eds. C. D. Coryell and D. Smirnov, J.-C. Thomas, K. Van de Vel, J. Van de Walle, N. Sugarman, Vol. 2, National Nuclear Energy Series, P. Van Duppen and J. Van Roosbroeck, Eur. Phys. J. A, Plutonium Project Record, Division IV, Vol. 9, McGraw-Hill, 2004, 21, (2), 243 New York, 1951, pp. 817–819 26 C. Weiffenbach, S. C. Gujrathi and J. K. P. Lee, Bull. Am. 44 E. Bohr and N. Hole, Ark. Mat. Astron. Fys. A, 1945, Phys. Soc., 1973, 18, (4), 702 32, (15), 1 27 A. H. W. Aten, Jr. and J. C. Kapteyn, Physica, 1967, 33, 45 R. B. Duffield and L. M. Langer, Phys. Rev., 1951, 81, (2), (3), 705 203 28 C. Weiffenbach, S. C. Gujrathi and J. K. P. Lee, Can. 46 W. E. Grummitt and G. Wilkinson, Nature, 1946, 158, J. Phys., 1975, 53, (2), 101 (4005), 163 29 A. H. W. Aten, Jr. and T. de Vries-Hamerling, Physica, 47 W. Seelmann-Eggebert, Naturwissenschaften, 1946, 33, 1955, 21, (6–10), 597 (9), 279 30 A. M. Lopez, W. V. Prestwich and B. Arad, Can. J. Phys., 48 G. B. Baró, W. Seelmann-Eggebert and I. E. Zabala, 1971, 49, (13), 1828 Z. Naturforsch., 1955, 10a, 80 31 A. H. W. Aten Jr. and J. C. Kapteyn, Physica, 1966, 32, 49 W. E. Nervik and G. T. Seaborg, Phys. Rev., 1955, 97, (4), (5), 989

1092 1997, 415, (2), 111 50 G. B. Baró, P. Rey and W. Seelmann-Eggebert, 65 T. Ohnishi, T. Kubo, K. Kusaka, A. Yoshida, K. Yoshida, Z. Naturforsch., 1955, 10a, 81 M. Ohtake, N. Fukuda, H. Takeda, D. Kameda, K. Tanaka, 51 J. A. Pinston, F. Schussler and A. Moussa, Nucl. Phys. A, N. Inabe, Y. Yanagisawa, Y. Gono, H. Watanabe, H. Otsu, 1969, 133, (1), 124 H. Baba, T. Ichihara, Y. Yamaguchi, M. Takechi, S. Nishimura, H. Ueno, A. Yoshimi, H. Sakurai, T. Motobayashi, T. Nakao, 52 J. B. Wilhelmy, ‘High-Resolution Gamma and X-Ray Y. Mizoi, M. Matsushita, K. Ieki, N. Kobayashi, K. Tanaka, Spectroscopy on Unseparated Fission Products’, Report Y. Kawada, N. Tanaka, S. Deguchi, Y. Satou, Y. Kondo, No. UCRL-18978, Lawrence Radiation Laboratory, T. Nakamura, K. Yoshinaga, C. Ishii, H. Yoshii, Y. Miyashita, University of California, Berkeley, USA, 1969 N. Uematsu, Y. Shiraki, T. Sumikama, J. Chiba, E. Ideguchi, 53 J. B. Wilhelmy, S. G. Thompson, J. O. Rasmussen, J. T. A. Saito, T. Yamaguchi, I. Hachiuma, T. Suzuki, Routti and J. E. Phillips, in “Nuclear Chemistry Division T. Moriguchi, A. Ozawa, T. Ohtsubo, M. A. Famiano, Annual Report, 1969”, eds. N. Edelstein, D. Hendrie and H. Geissel, A. S. Nettleton, O. B. Tarasov, D. P. Bazin, M. Michel, Report No. UCRL-19530, Lawrence Radiation B. M. Sherrill, S. L. Manikonda and J. A. Nolen, J. Phys. Laboratory, University of California, Berkeley, USA, 1970, Soc. Jpn., 2010, 79, (7), 073201 p. 178 66 E. Wefers, T. Faestermann, M. Münch, R. Schneider, 54 J. A. Pinston and F. Schussler, Nucl. Phys. A, 1970, 144, A. Stolz, K. Sümmerer, J. Friese, H. Geissel, M. Hellström, (1), 42 P. Kienle, H.-J. Körner, G. Münzenberg, C. Schlegel, 55 T. E. Ward, K. Takahashi, P. H. Pile and P. K. Kuroda, Nucl. P. Thirolf, H. Weick and K. Zeitelhack, ‘Halflives of RP- Phys. A, 1970, 154, (3), 665 Process Waiting Point Nuclei’, Experimental Nuclear Physics in Europe: ENPE 99: Facing the Next Millennium, 56 M. Karras and J. Kantele, Phys. Lett., 1963, 6, (1), 98 Seville, Spain, 21st–26th June, 1999, in “AIP Conference 57 G. Franz and G. Herrmann, Inorg. Nucl. Chem. Lett., Proceedings”, eds. B. Rubio, W. Gelletly and M. Lozano, 1975, 11, (12), 857 American Institute of Physics, New York, USA, 1999, 58 J. Äystö, C. N. Davids, J. Hattula, J. Honkanen, Vol. 495, pp. 375–376 K. Honkanen, P. Jauho, R. Julin, S. Juutinen, J. Kumpulainen, 67 M. Górska, S. Dean, V. Prasad N. V. S., A. Andreyev, T. Lönnroth, A. Pakkanen, A. Passoja, H. Penttilä, P. Taskinen, B. Bruyneel, S. Franchoo, M. Huyse, K. Krouglov, R. Raabe, E. Verho, A. Virtanen and M. Yoshii, Nucl. Phys. A, 1988, K. Van de Vel, P. Van Duppen and J. Van Roosbroeck, 480, (1), 104 ‘Beta Decay of Neutron-Deficient Ru and Rh Isotopes’, in 59 H. Penttilä, P. Taskinen, P. Jauho, V. Koponen, C. N. Davids “Proceedings PINGST2000”, eds. D. Rudolf and and J. Äystö, Phys. Rev. C, 1988, 38, (2), 931 M. Hellström, Proceedings of the International Workshop 60 J. Äystö, P. Taskinen, M. Yoshii, J. Honkanen, P. Jauho, PINGST2000: Selected Topics on N = Z Nuclei, Lund, H. Penttilä and C. N. Davids, Phys. Lett. B, 1988, 201, Sweden, 6th–10th June, 2000, Nuclear Structure Group (2), 211 Lund University, Sweden, 2000, pp. 108–112: http:// pingst2000.nuclear.lu.se/proceedings.asp (Accessed on 61 J. Äystö, J. Honkanen, P. Jauho, V. Koponen, H. Penttilä, 13th January 2011) P. Taskinen, M. Yoshii, C. N. Davids and J. Zylicz, ‘Nuclear Spectroscopy of On-Line Mass Separated Fission 68 A. H. W. Aten, Jr., H. Cerfontain, W. Dzcubas and Products with Mass Numbers from A = 110 to 120’, 5th T. Hamerling, Physica, 1952, 18, 972 International Conference on Nuclei Far from Stability, 69 D. J. Farmer, Phys. Rev., 1955, 99, (2), 659 Rosseau Lake, Ontario, Canada, 14th–19th September, 70 B. Pontecorvo, Nature, 1938, 141, (3574), 785 1987, in “AIP Conference Proceedings”, ed. I. S. Towner, 71 B. Pontecorvo, Phys. Rev., 1938, 54, (7), 542 American Institute of Physics, New York, 1988, Vol. 164, Part 1, p. 411 72 L. Frevert, R. Schöneberg and A. Flammersfeld, Z. Phys., 1965, 185, (3), 217 62 H. Penttilä, P. P. Jauho, J. Äystö, P. Decrock. P. Dendooven, M. Huyse, G. Reusen, P. Van Duppen and 73 H. J. Born and W. Seelmann-Eggebert, J. Wauters, Phys. Rev. C, 1991, 44, (3), R935 Naturwissenschaften, 1943, 31, (35–36), 420 63 M. Bernas, S. Czajkowski, P. Armbruster, H. Geissel, Ph. 74 L. E. Glendenin, National Nuclear Energy Series, Division Dessagne, C. Donzaud, H.-R. Faust, E. Hanelt, A. Heinz, IV, Plutonium Project Report M-CN-2184, September M. Hesse, C. Kozhuharov, Ch. Miehe, G. Münzenberg, 1944, p. 11 M. Pfützner, C. Röhl, K.-H. Schmidt, W. Schwab, 75 L. E. Glendenin, Paper 115: ‘Short-Lived Ruthenium- C. Stéphan, K. Sümmerer, L. Tassan-Got and B. Voss, Rhodium Decay Chains’, in “Radiochemical Studies: The Phys. Lett. B, 1994, 331, (1–2), 19 Fission Products”, eds. C. D. Coryell and N. Sugarman, 64 M. Bernas, C. Engelmann, P. Armbruster, S. Czajkowski, Vol. 2, National Nuclear Energy Series, Plutonium Project F. Ameil, C. Böckstiegel, Ph. Dessagne, C. Donzaud, Record, Division IV, Vol. 9, McGraw-Hill, New York, H. Geissel, A. Heinz, Z. Janas, C. Kozhuharov, Ch. Miehé, 1951, pp. 849–852 G. Münzenberg, M. Pfützner, W. Schwab, C. Stéphan, 76 F. Baumgärtner, A. Plata Bedmar and L. Kindermann, K. Sümmerer, L. Tassan-Got and B. Voss, Phys. Lett. B, Z. Naturforsch., 1958, 13a, 53

77 A. Jokinen, J. C. Wang, J. Äystö, P. Dendooven, The Author S. Nummela, J. Huikari, V. Kolhinen, A. Nieminen, John W. Arblaster is interested in K. Peräjärvi and S. Rinta-Antila, Eur. Phys. J. A, 2000, the history of science and the 9, (1), 9 evaluation of the thermodynamic and crystallographic properties of the 78 F. Montes, A. Estrade, P. T. Hosmer, S. N. Liddick, P. F. elements. Now retired, he previously Mantica, A. C. Morton, W. F. Mueller, M. Ouellette, worked as a metallurgical chemist in a E. Pellegrini, P. Santi, H. Schatz, A. Stolz, B. E. Tomlin, number of commercial laboratories O. Arndt, K.-L. Kratz, B. Pfeiffer, P. Reeder, W. B. Walters, and was involved in the analysis of a wide range of ferrous and non-fer- A. Aprahamian and A. Wöhr, Phys. Rev. C, 2006, 73, (3), rous alloys. 035801 79 W. B. Walters, B. E. Tomlin, P. F. Mantica, B. A. Brown, J. Rikovska Stone, A. D. Davies, A. Estrade, P. T. Hosmer, N. Hoteling, S. N. Liddick, T. J. Mertzimekis, F. Montes, A. C. Morton, W. F. Mueller, M. Ouellette, E. Pellegrini, P. Santi, D. Seweryniak, H. Schatz, J. Shergur and A. Stolz, Phys. Rev. C, 2004, 70, (3), 034314

“Asymmetric Catalysis on Industrial Scale”, 2nd Edition Edited by Hans-Ulrich Blaser (Solvias AG, Switzerland) and Hans-Jürgen Federsel (AstraZeneca, Sweden), Wiley-VCH, Weinheim, Germany, 2010, 580 pages, ISBN: 978-3-527-32489-7, £140, €168, US$360 (Print version); e-ISBN: 9783527630639, doi:10.1002/9783527630639 (Online version)

doi:10.1595/147106711X558310 http://www.platinummetalsreview.com/

Reviewed by Stewart Brown Introduction Johnson Matthey Precious Metals Marketing, “Asymmetric Catalysis on Industrial Scale:Challenges, Orchard Road, Royston, Hertfordshire SG8 5HE, UK; Approaches and Solutions”, edited by Hans-Ulrich E-mmail: [email protected] Blaser and Hans-Jürgen Federsel, builds and expands upon its first edition, which was published in 2004 (1). The second edition provides the reader with a comprehensive examination of the industrially important aspects of asymmetric catalysis, an area of organic chemistry that introduces chirality (a molecule that is non-superimposable upon its mirror image) to a molecule.This is especially important for pharmaceuticals, as biologically active compounds are often chiral molecules. One of the book’s co-editors, Hans-Ulrich Blaser, is currently Chief Technology Officer at Solvias in Basel, Switzerland, having previously spent twenty years at Ciba and three years at Novartis.The other co- editor,Hans-Jürgen Federsel, is Director of Science for Pharmaceutical Development at AstraZeneca in Sweden. He is recognised as a specialist in process research and development where he has worked for over 30 years. The monograph is divided into 28 chapters, each containing stand-alone case studies of a particular chemical or biocatalytic process. This makes the text very easy to dip in and out of, or alternatively to look for specific examples of interest. The book highlights real world processing issues, showing how each has been tackled and solved by the authors. The main aim of this book is to show that asymmetric catalysis is not merely the preserve of academic research; rather, it is a large-scale production tool for industrial manufacturing. However, just as importantly it provides support and ideas for those suffering with similar issues in optimising industrial syntheses. The reader of this book is required to have a relatively advanced knowledge of organic chemistry in order to fully appreciate the complexities of the vast range of reactions covered. It is aimed primarily at

postgraduate level and particularly at those involved Throughout this book the importance of process in the pharmaceutical and process chemistry indus- development and scale-up, taking laboratory-scale tries.The book combines both organic chemistry and products to pilot plant and subsequently full-scale biochemistry in almost equal measure and so a good production of active, pure products is impressed understanding of biological compounds and reac- upon the readers. tions is also required. The range of enantioselective catalysis shown in this book highlights the growing importance of Asymmetric Catalysis by the developing more selective, active and ultimately Platinum Group Metals more cost-effective processes for the production of The chapters are written by a grand total of 87 dif- specific biologically active compounds. ferent authors from a plethora of pharmaceutical companies around the world, as well as a few chemi- New Processes for Existing Active Compounds cals companies and universities. The lengths of the The first section of the book contains five chapters, chapters are such that a solid overview is provided, each of which examines either new catalysts or new without overloading the reader with information. All routes to produce existing compounds for such prod- reaction schemes are well drawn and are generally ucts as cholesterol-lowering, cough-relieving or anti- complemented with graphs and spectra of the synthe- obesity drugs, as well as vitamins and indigestion sised compounds, as well as some photographs and remedies. Asymmetric hydrogenations catalysed by process flow sheets to demonstrate some very elegant Ru, Ir or Rh feature heavily,especially in Chapter 2 in engineering solutions. Furthermore, the chapters are which Kurt Püntener and Michelangelo Scalone well referenced, allowing easy access to further infor- (F.Hoffmann-La Roche Ltd, Switzerland) present five mation and literature should the reader so require. example syntheses showing how the hydrogenation Due to the broad scope of this book, in terms of of different functional groups has led to significant the variety of reactions and processes covered, this improvements in the production of active pharma- review will only focus on those involving platinum ceutical intermediates (APIs). group metal (pgm) catalysts. It will not cover non- Chapter 3 takes a detailed look at the use of asym- pgm catalytic processes or those involving biologi- metric hydrogenation in the production of (+)–biotin cal catalysis, of which there are many interesting (vitamin H). This compound has three stereocentres examples. that need to be controlled to produce the pure, In terms of coverage, as expected in this particular active compound that can produce full biological field, the pgms feature heavily throughout, with one activity in the body. The reader is led through the or more of the metals being referred to in 17 of the history of biotin production (today a 100 tonne per 28 chapters. In fact, Chapter 20, which examines year industry) from the original eleven-step Goldberg- asymmetric hydrogenation for the design of drug Sternbach concept involving a palladium-catalysed substances, features all five of the pgms that are hydrogenation step, through to the much shorter and most widely used for catalytic applications: platinum, more elegant Lonza process, utilising a rhodium- palladium, rhodium, iridium and ruthenium. catalysed asymmetric hydrogenation step (Scheme I). Interestingly,the book is arranged by process rather The often lengthy reaction schemes are very well than perhaps a more orthodox method of segmenting drawn out and highlight the complexities associated by catalyst type or chemical transformation. The rea- with this particular synthesis. soning behind this is that it enables readers to find Chapter 5 covers the important reaction of asym- out how particular issues have been solved on a metric ketone reduction, which despite being aca- process level, which should prove useful to the indus- demically well understood poses significant issues trial practitioner. in complex biological molecules on an industrial The chapters are grouped into three sections: scale. This chapter highlights the groundbreaking • Part I:‘New Processes for Existing Active work by Ryoji Noyori, who won the 2001 Nobel Prize Compounds (APIs)’; in Chemistry with William S. Knowles for their work • Part II:‘Processes for Important Building Blocks’; on chiral hydrogenation reactions catalysed by Rh • Part III:‘Processes for New Chemical Entities and Ru complexes (2). This has influenced the work (NCEs)’. in this chapter and much of the rest of the book.

Scheme I. The Lonza concept: (+)-biotin process using asymmetric hydrogenation catalysed by a rhodium(I) complex

Andreas Marc Palmer (Nycomed GmbH, Germany) The technique of asymmetric transfer hydrogena- and Antonio Zanotti-Gerosa (Johnson Matthey tion is an important method for producing optically Catalysis and Chiral Technologies,UK) tell the story of active alcohols and amines (for example, Scheme II). how selectivity and activity can be tuned by the opti- The authors spend considerable time in this chapter misation of ruthenium phosphine complexes such as discussing the reaction components before moving those shown in Figure 1 for large-scale reactions. on to some case studies to illustrate their use. This is certainly one of the most detailed chapters, and it is Processes for Important Building Blocks well supported by a series of tables, reaction schemes The second section contains fourteen chapters cate- and graphs. gorised as new catalyst and process developments for synthetically important building blocks, nine of Processes for New Chemical Entities which mention pgms. Chapter 16 in particular The final section is the least relevant in terms of demonstrates the effectiveness of pgms with mention pgm use, with five of the remaining nine chapters not given to Pd, Rh, Ir and Ru in a particularly in-depth featuring the metals. However, one of the stand- analysis of asymmetric transfer hydrogenation. out reviews in terms of pgm catalysis is Chapter 20.

Fig. 1. Two examples of ruthenium phosphine complexes used as catalysts for the asymmetric reduction of ketones

Scheme II. Rhodium-catalysed asymmetric transfer hydrogenation reaction investigated for the synthesis of a key intermediate of duloxetine

This chapter, entitled ‘Enabling Asymmetric Conclusions Hydrogenation for the Design of Efficient Synthesis of This book contains a comprehensive examination of Drug Substances’ and written by Yongkui Sun, Shane a wide range of industrially important asymmetric Krska, C. Scott Shultz and David M. Tellers (Merck & reactions. It clearly shows the difficulties and chal- Co, Inc, USA), includes examples of catalysed steps lenges associated with these reactions, and more involving platinum, palladium, rhodium, iridium and importantly how scientists and engineers have man- ruthenium during the course of the text. aged to successfully overcome them. The pgms fea- The chapter begins with an introduction once ture in a large proportion of the syntheses and again paying tribute to the great work by Knowles processes mentioned, with palladium-catalysed and Noyori in the field of asymmetric hydrogenation. hydrogenations and the work of Knowles and Noyori It then talks about the work done by Merck chemists being particularly significant. to increase the use of asymmetric catalysis in drug The book is easy to read and well illustrated and discovery programmes within the company.The chap- referenced throughout. The decision to group the ter drives home the key message that by identifying chapters by the nature of the process works well, and having a concerted effort to utilise and improve with the tables at the front of the book easily a particular reaction, unprecedented progress could directing readers to subjects of interest. The key aim be made. of this book, to show that asymmetric catalysis is not Three detailed case studies born out of Merck’s merely the preserve of academic research, is driven ‘Catalysis Initiative’ are then recounted: laropiprant, home in every chapter. The relevance of each reac- an API in the cholesterol-lowering drug TredaptiveTM; tion and synthesis to the industrial environment is taranabant, an API in the treatment of obesity; and made abundantly clear through a wide array of case sitagliptin, an API in the treatment of type 2 diabetes studies. (Figure 2) (Scheme III). All three demonstrate the Overall, this book will be of interest to both indus- vital importance of high-throughput screening to trial specialists and academics as it contains a good optimise both catalyst and reaction conditions mix of chemistry and engineering. It provides com- within a constrained time-frame.The whole chapter is fort and inspiration to those working in this field a success story for the Merck ‘Catalysis Initiative’ and through the numerous success stories told and is should serve as inspiration to other companies in undoubtedly a useful source of potential contacts the search for new methods for large-scale drug for those struggling with a particular asymmetric production. synthesis issue.

Fig. 2. The structures of laropiprant, taranabant and sitagliptin

Scheme III. First generation route to sitagliptin. BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl; EDC = N-(3-dimethylaminopropyl)-N‘-ethylcarbodiimide hydrochloride; DIAD = di-isopropyl azodicarboxylate; NMM = N-methylmorpholine

“Asymmetric References Catalysis on Industrial 1 “Asymmetric Catalysis on Industrial Scale: Challenges, Scale”, 2nd Approaches and Solutions”, eds. H.-U. Blaser and Edition E. Schmidt, Wiley-VCH, Weinheim, Germany, 2004 2 ‘Advanced Information on the Nobel Prize in Chemistry 2001, Catalytic Asymmetric Synthesis’, The Royal Swedish Academy of Sciences, Stockholm, Sweden, 10th October, 2001

The Reviewer Dr Stewart Brown graduated with an MChem (Hons) and a PhD in Chemistry from the University of Liverpool, UK. He joined Johnson Matthey in 2004 and spent 5 years as a Process Development Chemist, involved in the scale-up of new catalysts and processes for the Emission Control Technologies business unit. In 2009 he transferred to Precious Metals Marketing and is currently a Market Analyst within the Market Research team, focusing on the chemical, electronics, automotive and petroleum refining sectors.

Publications in Brief

BOOKS Recent examples of industrial production of active pharmaceutical ingredients are given. It includes “Healthy, Wealthy, Sustainable World” chapters on ‘Development of Palladium Catalysts for J. Emsley (UK), Royal Society of Chemoselective Hydrogenation’, ‘Silicon-Based Chemistry, Cambridge, UK, 2010, Carbon–Carbon Bond Formation by Transition Metal 248 pages, ISBN 978-1-84755-862-6, Catalysis’ and ‘Direct Reductive Amination with £18.99 Amine Boranes’. The themes of this general reader book relate to the impor- JOURNALS tance of chemistry in everyday life, the benefits chemicals cur- Geoscience Frontiers rently bring, and how the use of Editor-in-Chief: X. X. Mo (China chemicals can continue on a University of Geosciences (Beijing), sustainable basis. Topics cov- China); China University of ered include: health, food (the role of agrochemicals Geosciences (Beijing), Peking University and Elsevier BV; ISSN and food chemists),water (drinking water; the seas as 1674-9871 a source of raw materials),fuels,plastics (can they be Geoscience Frontiers (GSF) is a sustainable?), cities and sport. new quarterly journal under the joint sponsorship of the China “Modern Electroplating”, 5th Edition University of Geosciences Edited by M. Schlesinger (University (Beijing) and Peking University. Co-published with of Windsor, Windsor, Ontario, Canada) and M. Paunovic (USA), Elsevier, GSF publishes original research articles and John Wiley & Sons, Inc, Hoboken, reviews of recent advances in all fields of earth sci- New Jersey, USA, 2010, 736 pages, ences. Technical papers, case histories, reviews and ISBN 978-0-470-16778-6, £100.00, discussions are included. €120.00, US$149.95; e-ISBN: 9780470602638 Greenhouse Gases: Science and Technology This expanded new edition Edited by Mercedes Maroto-Valer places emphasis on electroplat- (Centre for Innovation in Carbon ing and electrochemical plating in nanotechnolo- Capture and Storage (CICCS), Uni- gies, data storage and medical applications. It versity of Nottingham, UK) and includes chapters on ‘Palladium Electroplating’ and Curtis Oldenburg (Geologic Carbon ‘Electroless Deposition of Palladium and Platinum’. Sequestration (GCS) Program, Lawrence Berkeley National Labora- tory, USA); Society of Chemical “Pharmaceutical Process Chemistry” Industry and John Wiley & Sons, Ltd; Edited by T. Shioiri (Japan), K. Izawa e-ISSN 2152-3878 (Ajinomoto Co, Inc, Japan) and Greenhouse Gases: Science and Technology (GHG)is T. Konoike (Shionogi & Co, Ltd, a new quarterly online journal from the Society of Japan), Wiley-VCH Verlag GmbH & Co KGaA, Weinheim, Germany, 2011, Chemical Industry (SCI) and Wiley. GHG is dedicated 526 pages, ISBN 978-3-527-32650-1, to the management of greenhouse gases through cap- £125.00, €150.00, US$210.00; ture, storage, utilisation and other strategies. GHG will e-ISBN 9783527633678 explore subject areas such as: This book covers the basic (a) Carbon capture and storage;

chemistry needed for future (b) Utilisation of carbon dioxide (CO2); developments and key tech- (c) Other greenhouse gases: methane (CH4), nitrous niques in the pharmaceutical industry, as well as oxide (N2O), halocarbons; morphology, engineering and regulatory issues. (d) Other mitigation strategies.

High-Temperature Materials CO2 capture and utilisation,hydrogen production and JOM, 2010, 62, (10) utilisation,and novel functional materials. This ISCRE 21 special issue of Industrial & Engineering Chemistry The theme of this issue of JOM Research consists of Invited Perspectives by the is high-temperature materials plenary speakers, as well as regular, full-length con- which includes the following tributed papers by the other authors. four articles on the topic of nickel-based superalloys: Recent Advances in the in-situ Characterization of The Thermodynamic Modeling of Heterogeneous Catalysts Precious-Metal-Modified Nickel Based Superalloys Chem. Soc. Rev., 2010, 39, (12), 4541–5072 F. Zhang, J. Zhu, W. Cao, C. Zhang and Y. A. Chang, JOM, 2010, 62, (10), 35 The 28 review articles of this themed issue of Chemical Precious-Metal-Modified Nickel-Based Superalloys: Motivation and Potential Industry Applications Society Reviews cover the advantages, limitations, challenges A. Bolcavage and R. C. Helmink, JOM, 2010, 62, (10), 41 and future possibilities of in situ The Use of Precious-Metal-Modified Nickel-Based characterisation techniques for Superalloys for Thin Gage Applications “elucidating the ‘genesis’ and D. L. Ballard and A. L. Pilchak, JOM, 2010, 62, (10), 45 working principles of heterogeneous catalysts”. Bert A Combined Mapping Process for the Development of Weckhuysen (Inorganic Chemistry and Catalysis Platinum-Modified Ni-Based Superalloys Group, Debye Institute for Nanomaterials Science, A. J. Heidloff, Z. Tang, F. Zhang and B. Gleeson, JOM, 2010, Utrecht University, The Netherlands) assembled this 62, (10), 48 issue on in situ characterisation of catalytic solids.

21st International Symposium on Chemical Reaction ON THE WEB Engineering (ISCRE 21) Ind. Eng. Chem. Res., 2010, 49, (21), Global Emissions Management 10153–11120 Latest issue: Volume 3, Issue 01 ISCRE 21 was held in (November 2010) Philadelphia, Pennsylvania, USA, Johnson Matthey Environ- from 13th–16th June 2010. The mental Catalysts and Tech- symposium focused on the role nologies’ Global Emissions of chemical reaction engineer- Management (GEM) publi- ing in addressing resource sus- cation featuring developments in emissions control is tainability, environmental and now online. Free subscription to GEM online allows life science challenges. The topics covered included subscribers to: rational design of catalysts, computational catalysis, (a) Read up-to-date news and features; reaction path analysis, dynamics of chemical reac- (b) Access all previous articles from Global tors, multiphase and reacting flows, environmental Emissions Management; reaction engineering, microreactors, membrane reac- (c) Create a bespoke issue using MyGEM; tors, process intensification, fuel cells, bioderived (d) Print, download and share all articles. chemicals and fuels, clean coal conversion processes, Find this at: http://www.jm-gem.com/

Abstracts

CATALYSIS – APPLIED AND PHYSICAL 2,7-dihydroxynaphthalene under UV irradiation. The ASPECTS NPs’ morphology was tuned by changing the surfac- tant:metal ion molar ratios and altering other param- Controlled Synthesis of Pt Nanoparticles via Seeding eters.The Ir nano-needles were a good catalyst for the Growth and Their Shape-Dependent Catalytic Activity reduction of organic dyes in presence of NaBH4. X. Gong, Y. Yang, L. Zhang, C. Zou, P. Cai, G. Chen and S. Huang, J. Colloid Interface Sci., 2010, 352, (2), 379–385 CATALYSIS – REACTIONS Octahedral,cuboctahedral,branched and ‘rice-like’Pt NPs were synthesised using a seed-mediated growth Selective Oxidation of Glucose Over Carbon- route. Pt NPs (3 nm) were prepared and dispersed in Supported Pd and Pt Catalysts oleyl amine to form a seed solution and then I. V. Delidovich, O. P. Taran, L. G. Matvienko, A. N. Simonov, I. L. Simakova, A. N. Bobrovskaya and V. N. Parmon, Catal. Pt(acac)2 was added. By adjusting the molar ratio of Lett., 2010, 140, (1–2), 14–21 Pt from Pt(acac)2 and seed NPs, the seed diameter and the addition route of Pt(acac)2, the NPs growth Pt/C exhibited lower specific activity and provided could be controlled to fall into in a kinetic or thermo- poor selectivity of glucose oxidation to gluconic acid dynamic growth regime. The obtained NPs were by O2 in comparison with Pd/C.The finely dispersed supported on C black (Vulcan XC-72). The catalysts Pd/C catalysts are prone to deactivation due to oxida- synthesised from branched NPs were found to have tion of their surface, while larger metal particles are higher catalytic activity and stability for the oxidation more tolerant and stable. The activity of Pd nano- of methanol. particles can be maintained when the process is controlled by diffusion of O towards the active com- Pyrophoricity and Stability of Copper and Platinum ponent of the catalyst. Based Water-Gas Shift Catalysts during Oxidative Shut-Down/Start-Up Carbonates: Eco-Friendly Solvents for Palladium- Catalysed Direct Arylation of Heteroaromatics R. Kam, J. Scott, R. Amal and C. Selomulya, Chem. Eng. Sci., 2010, 65, (24), 6461–6470 J. J. Dong, J. Roger, C. Verrier, T. Martin, R. Le Goff, C. Hoarau and H. Doucet, Green Chem., 2010, 12, (11), 2053–2063 In this investigation Cu/ZnO exhibited high levels of pyrophoricity.This manifested as a sharp temperature Direct 2-,4- or 5-arylation of heteroaromatics with aryl rise of the catalyst bed upon air introduction. Severe halides using PdCl(C3H5)(dppb) as catalyst precur- sintering of the bulk and metallic phases of the cata- sor/base was shown to proceed in moderate to good lyst resulted in catalyst deactivation.No pyrophoricity yields using the solvents diethylcarbonate (see the was observed for Pt-based catalysts; however, there Figure) or propylene carbonate.The best yields were obtained using benzoxazole or thiazole derivatives was sintering of the metallic phase in Pt/TiO2 and (130ºC). The arylation of furan, thiophene, pyrrole, Pt/ZrO2. Pt/CeO2 retained its activity, displaying no loss in specific surface area or metal dispersion. imidazole or isoxazole derivatives was found to require a higher reaction temperature (140ºC). Shape-Selective Formation and Characterization of Catalytically Active Iridium Nanoparticles S. Kundu and H. Liang, J. Colloid Interface Sci., 2011, J. J. Dong et al., Green Chem., 2010, 12, (11), 2053–2063 354, (2), 597–606 Sphere, chain, flake and needle shaped Ir NPs were synthesised via reduction of Ir(III) ions in cetyltrimethylammo- nium bromide micellar media containing alkaline

EMISSIONS CONTROL lower ohmic and charge transfer resistance. By using CV with H2 adsorption, it was found that the electro- A Global Description of DOC Kinetics for Catalysts chemically active area of the electrocatalyst prepared with Different Platinum Loadings and Aging Status by CCM-DT was higher than those by CCS and K. Hauff, U. Tuttlies, G. Eigenberger and U. Nieken, Appl. CCM-DS. Under a H2/O2 system at 0.6 V, the cells Catal. B: Environ., 2010, 100, (1–2), 10–18 with an MEA made by CCM-DT provided the highest γ –2 Five Pt/ -Al2O3 DOCs with different Pt loadings and cell performance (~350 mA cm ). ageing steps were characterised with regards to Pt particle diameter,active surface area and conversion METALLURGY AND MATERIALS behaviour for CO, propene and NO oxidation. HR-REM showed that the Pt particles have diameters Shape Memory Effect and Pseudoelasticity of TiPt larger than 8 nm. The catalyst activity was shown to Y. Yamabe-Mitarai, T. Hara, S. Miura and H. Hosoda, Intermetallics, 2010, 18, (12), 2275–2280 be directly proportional to the catalytically active surface area, which was determined by CO chemisorp- Martensitic transformation behaviour and SM prop- tion measurements. In order to model the CO and erties of Ti-50 at%Pt SMA were investigated using propene oxidation kinetics, only the catalytically high-temperature XRD and loading–unloading com- active surface has to be changed in the global pression tests. The structures of the parent and kinetic models. The same was true for NO oxidation martensite phases were identified as B2 and B19, at higher temperatures. respectively. Strain recovery was observed during unloading at RT and at 1123 K, which was below the FUEL CELLS martensite temperature. Shape recovery was investigated for the samples by heating at 1523 K for 1 h. The High Platinum Utilization in Ultra-Low Pt Loaded strain recovery rate was 30–60% for the samples tested PEM Fuel Cell Cathodes Prepared by Electrospraying at RT and ~11% for the samples tested at 1123 K. S. Martin, P. L. Garcia-Ybarra and J. L. Castillo, Int. J. Role of Severe Plastic Deformation on the Cyclic Hydrogen Energy, 2010, 35, (19), 10446–10451 Reversibility of a Ti50.3Ni33.7Pd16 High Temperature The title cathodes with Pt loadings as low as 0.012 mg Shape Memory Alloy Pt cm–2 were prepared by the electrospray method. B. Kockar, K. C. Atli, J. Ma, M. Haouaoui, I. Karaman, M. SEM of these layers showed a high dispersion of the Nagasako and R. Kainuma, Acta Mater., 2010, 58, (19), catalyst powders forming fractal deposits made by 6411–6420 small clusters of Pt/C NPs, with the clusters arranging The effect of microstructural refinement on the ther- in a dendritic growth. Using these cathodes in MEAs, momechanical cyclic stability of the title HTSMA –1 a high Pt utilisation in the range 8–10 kW g was which was severely plastically deformed using equal obtained for a fuel cell operating at 40ºC and atmos- channel angular extrusion (ECAE) was investigated. –1 pheric pressure.Moreover,a Pt utilisation of 20 kW g The grain/subgrain size of the high temperature was attained at 70ºC and 3.4 bar over-pressure. austenite phase was refined down to ~100 nm. The Effect of MEA Fabrication Techniques on the Cell increase in strength differential between the onset of Performance of Pt–Pd/C Electrocatalyst for Oxygen transformation and the macroscopic plastic yielding Reduction in PEM Fuel Cell after ECAE led to enhancement in the cyclic stability S. Thanasilp and M. Hunsom, Fuel, 2010, 89, (12), during isobaric cooling–heating. The reduction in 3847–3852 irrecoverable strain levels is attributed to the increase in critical stress for dislocation slip due to the The effect of three different MEA fabrication tech- microstructural refinement during ECAE. niques: catalyst-coated substrate by direct spray (CCS), catalyst-coated membrane by direct spray CHEMISTRY (CCM-DS) or decal transfer (CCM-DT), on the O2 reduction in a PEMFC was investigated under identi- The Chemistry of Tri- and High-Nuclearity cal Pt-Pd/C loadings. The cells prepared by the CCM Palladium(II) and Platinum(II) Complexes methods, and particularly by CCM-DT,exhibited a sig- V. K. Jain and L. Jain, Coord. Chem. Rev., 2010, 254, nificantly higher open circuit voltage (OCV) but a (23–24), 2848–2903

This review gives an overview of the title complexes S. D. Wolter, B. Brown, C. B. Parker, B. R. Stoner and J. T. and reports developments. Three or more square- Glass, Appl. Surf. Sci., 2010, 257, (5), 1431–1436 planar metal atoms can be assembled in several ways Ambient air oxidation of Au-Pt thin films was carried resulting in complexes with a myriad of geometric out at RT and then the films were characterised by forms.These square planes may be sharing a corner, XPS. The homogeneous films were prepared by RF an edge and two edges or even separated by ligands cosputtering with compositions varying from Au9Pt91 having their donor atoms incapable of forming to Au89Pt11 and compared to pure Pt and Au thin chelates, yielding dendrimers and self-assembled films. The predominant oxidation products were PtO molecules. Synthetic, spectroscopic and structural and PtO2. Variations in Pt oxide phases and/or con- aspects of these complexes together with their appli- centration did not contribute to enhanced electrocat- cations are described. (Contains 554 references.) alytic activity for oxygen reduction observed for the intermediate alloy stoichiometries. ELECTRICAL AND ELECTRONICS A Feasibility Study of the Electro-recycling of Dissolution and Interface Reactions between Greenhouse Gases: Design and Characterization of a (TiO /RuO )/PTFE Gas Diffusion Electrode for the Palladium and Tin (Sn)-Based Solders: 2 2 Electrosynthesis of Methanol from Methane Part I. 95.5Sn-3.9Ag-0.6Cu Alloy R. S. Rocha, L. M. Camargo, M. R. V. Lanza and R. Bertazzoli, P. T. Vianco, J. A. Rejent, G. L. Zender and P. F. Hlava, Metall. Electrocatalysis, 2010, 1, (4), 224–229 Mater. Trans. A, 2010, 41, (12), 3042–3052 The title GDE was designed to be used in the elec- The interface microstructures and dissolution behav- trochemical conversion of CH into MeOH under iour which occur between Pd substrates and molten 4 conditions of simultaneous O evolution. The GDE 95.5Sn-3.9Ag-0.6Cu (wt%) were studied. The solder 2 was prepared by pressing and sintering TiO (0.7)/ bath temperatures were 240–350ºC, and the immer- 2 RuO (0.3) powder and PTFE. CH was inserted into sion times were 5–240 s.As a protective finish in elec- 2 4 the reaction medium by the GDE and electrosynthe- tronic assemblies, Pd would be relatively slow to sis was carried out in 0.1 mol l–1 Na SO . Controlled dissolve into molten Sn-Ag-Cu solder. The Pd-Sn inter- 2 4 potential experiments showed that MeOH concen- metallic compound (IMC) layer would remain suffi- tration increased with applied potential, reaching ciently thin and adherent to a residual Pd layer so as 220 mg l–1 cm2,at 2.2V vs. a calomel reference elec- to pose a minimal reliability concern for Sn-Ag-Cu trode. Current efficiency for MeOH formation was 30%. interconnections.

Dissolution and Interface Reactions between PHOTOCONVERSION Palladium and Tin (Sn)-Based Solders: Part II. 63Sn-37Pb Alloy Cyclometalated Red Iridium(III) Complexes P. T. Vianco, J. A. Rejent, G. L. Zender and P. F. Hlava, Metall. Containing Carbazolyl-Acetylacetonate Ligands: Mater. Trans. A, 2010, 41, (12), 3053–3064 Efficiency Enhancement in Polymer LED Devices The interface microstructures as well as the rate N. Tian, Y. V. Aulin, D. Lenkeit, S. Pelz, O. V. Mikhnenko, P. W. kinetics of dissolution and IMC layer formation were M. Blom, M. A. Loi and E. Holder, Dalton Trans., 2010, 39, investigated for couples formed between molten (37), 8613–8615 63Sn-37Pb (wt%) and Pd sheet.The solder bath tem- New red emitting cyclometalated Ir(III) complexes peratures were 215–320ºC, and the immersion times containing carbazolyl-acetylacetonate ligands (1, 2) were 5, 15, 30, 60, 120 and 240 s. The extents of Pd were prepared and then compared to the commonly dissolution and IMC layer development were signifi- used reference emitter [(btp)2Ir(III)(acac)]. For a cantly greater for molten Sn-Pb than the Pb-free range of concentrations the new complexes Sn-Ag-Cu (Part I, as above) at a given test temperature. revealed better luminous efficiencies than [(btp)2Ir(III)(acac)]. The phosphorescence decay times of the newly designed triplet emitters are ELECTROCHEMISTRY significantly shorter making them attractive The Effect of Gold on Platinum Oxidation in candidates for applications in advanced organic and Homogeneous Au–Pt Electrocatalysts polymer LEDs.

N. Tian et al., Dalton Trans., 2010, 39, (37), 8613–8615

1 2

Patents

CATALYSIS – APPLIED AND PHYSICAL photocatalyst for decomposing H2O to produce H2. ASPECTS The photocatalyst is prepared by cross-coupling a ter- pyridyl Os complex with phenylboronic acid pinacol Palladium(0) Complex Catalyst ester having a phosphinothioyl group in the presence Johnson Matthey Plc, World Appl. 2010/128,316 of a Pd catalyst to obtain the corresponding phos- A Pd(0)Ln complex, where L is a ligand and phine sulfide.This is reacted with Raney Ni to give a 2+ n = 2,3 or 4,is prepared by reacting a Pd(II) complex diphosphine ligand having an Os(tpy)2 moiety. in a solvent with a base and ligand L. Further base, This ligand is mixed with a transition metal complex optionally in a solvent, may be added to form the such as [RhCl(CO)2]2 in a suitable solvent at room Pd(0)Ln complex. The pre-formed Pd(0) complex temperature to obtain the dinuclear metal complex. can be prepared on an industrial scale and used as a catalyst in Pd-catalysed cross-coupling reactions. When n = 2, the Pd(II) complex may not be CATALYSIS – INDUSTRIAL PROCESS

[(o-tol)3P]2PdCl2. The Pd(0)Ln complex may be, for Palladium-Catalysed Preparation of Intermediates t t example, Pd[ Bu2(p-PhMe2N)P]2 or Pd[ Bu2(Np)P]2. Bayer CropScience AG, World Appl. 2011/003,530 Polymer-Supported Ruthenium Catalysts Substituted and unsubstituted (2,4-dimethylbiphenyl- C.-M. Che and K.-W. M. Choi, US Appl. 2011/0,009,617 3-yl)acetic acids and their esters are prepared via a Non-crosslinked soluble polystyrene-supported Ru selective Suzuki cross-coupling reaction using nanoparticles were prepared by reacting homogenous or heterogeneous Pd catalysts. 4-tert- Butyl-2,6-dimethylphenyl acetic acid and 4-tert-butyl- [RuCl2(C6H5CO2Et)]2 with polystyrene in air. The supported Ru nanoparticles can be used to catalyse 2,6-dimethyl mandelic acid, useful as intermediates intra- and intermolecular carbenoid insertion into for pharmaceutical compounds or agricultural chem- C–H and N–H bonds, alkene cyclopropanation and icals, are produced in good yield from inexpensive ammonium ylide/[2,3]-sigmatropic rearrangement starting materials. reactions and can be recovered and reused ten times Fixed-Bed Platinum Catalyst for Hydrosilylation without significant loss of activity. Gelest Technol. Inc, US Appl. 2010/0,280,266 Dinuclear Osmium-Rhodium Photocatalyst A recyclable fixed-bed catalyst complex containing a Toyota Motor Corp, Japanese Appl. 2010-209,044 silica-supported Pt carbene catalyst is claimed for use A dinuclear metal complex,for example 1,containing in a hydrosilylation process between an olefin, sili- 2+ a light-harvesting Os(tpy)2 moiety and a catalytical- cone or alkyne and a silicone to produce an ly active diphosphine Rh moiety can be used as a organofunctional silane and/or a crosslinked silicone which contains <20 ppm residual Pt, preferably <10 ppm. The process can be repeated between 3–100 Japanese Appl. 2010-209,044 times over a period from 1 week to 1 year without new addition of catalyst complex.It may be used in a (PF ) 6 2 continuous reactor system.

N R2 Rhodium Catalysts for Hydroformylation P N N Cl Eastman Chem. Co, US Patent 7,872,156 (2011) Os Rh Novel fluorophosphite compounds active for hydro- N N CO formylation processes for ethylenically unsaturated N P substrates are claimed. Catalyst solutions contain R 2 20–300 mg l–1 Rh with a mole:atom gram ratio of fluo- 1 rophosphite:Rh between 1:1–200:1.The hydroformyla- R =phenyl, isopropyl, ethyl, tert-butyl, cyclohexyl, tion activity increases as the concentration of ligand propyl or naphthyl increases. Linear or branched aldehydes can be

produced under standard hydroformylation reaction size <100 nm, preferably <10 nm. Preferred composi- ≤ ≤ conditions of 75–125ºC and 1–70 bar (15–1000 psig). tions include (Pt3Co)100–yZry, where 0 y 30 at%; ≤ ≤ ≤ ≤ or (Pt100–xCox)100–yZry, where 0 x 80 and 0.5 y EMISSIONS CONTROL 60 at%. Gold-Platinum Electrode Catalyst High Palladium Content Diesel Oxidation Catalysts Toyota Motor Corp, Japanese Appl. 2010-211,946 Umicore AG & Co KG, World Appl. 2010/133,309 A nanoscale catalyst layer for a FC is formed from a Pd-enriched DOCs are claimed for the oxidation of Au core having average particle diameter <10 nm CO and HC emissions from a compression ignition/ with a Pt shell.The Au and Pt may form an alloy.Initial diesel engine. A first washcoat covers 25–95% of the activity is good and dissolution of Pt is suppressed. substrate from the inlet and may contain Pt:Pd in a ratio for example 1:1; a second washcoat is richer in Pd than the first washcoat,with a Pt:Pd ratio for exam- METALLURGY AND MATERIALS ple 1:2, and covers 5–75% of the substrate from the Nickel- and Copper-Free White Gold Alloy inlet.The catalysts are described as having increased Rolex SA, European Appl. 2,251,444 (2010) performance and hydrothermal durability under cold start conditions. A white Au alloy free of Ni and Cu contains (in wt%): >75 Au; 18–24 Pd; 1–6 In, Mn, Hf, Nb, Pt, Sn, Ta, V, Zn Platinum-Palladium Diesel Oxidation Catalyst and/or Zr; optionally >0.5 Si,Ga and/or Ti; and option- BASF Corp, US Patent 7,875,573 (2011) ally >0.2 Ru, Ir and/or Re. The alloy is prepared by An exhaust gas treatment system includes a DOC placing the components in a crucible; melting the containing two washcoat layers coated onto a high components; pouring the molten alloy; allowing to surface area support substantially free of silica. The harden; quenching in water; subjecting to at least one bottom washcoat layer contains Pt:Pd in a ratio cold rolling; and annealing under reducing atmos- between 2:1–1:2 and does not contain a HC storage phere. The alloy is described as having suitable component. The top washcoat layer contains Pt:Pd mechanical properties for watch making and jew- in a ratio between 2:1–10:1 and one or more HC stor- ellery use, and does not require Rh plating. age components. A soot filter is located downstream Iridium and Rhodium Alloys with Increased Strength of the DOC and a NOx conversion catalyst is located W. C. Heraeus GmbH, US Appl. 2010/0,329,922 downstream of the soot filter. Ir and Rh alloys with increased creep rupture strength at high temperature, in particular at ~1800ºC, are FUEL CELLS claimed.0.5–30 ppm B and 0.5–20 ppm Ca are added Platinum and Palladium Alloy Electrodes to Zr- and Hf-free Ir, Rh or alloys thereof. The alloys Danmarks Tekniske Univ., World Appl. 2011/006,511 may also be free of Ti.The strengthened Ir alloys may be used in Ir crucibles for growing single crystals Electrode catalysts formed from Pt or Pd, preferably such as Nd:YAG laser crystals or in components for Pt, alloyed with Sc,Y and/or La on a conductive sup- the glass industry. port material are claimed for use in a PEMFC.The catalysts are described as having increased ORR activity, comparable active site density and lower cost com- APPARATUS AND TECHNIQUE pared to pure Pt. The activity enhancement is stable Palladium Membrane for Hydrogen Separation over extended periods of time. Korea Inst. Energy Res., US Patent 7,875,154 (2011) Binary and Ternary Platinum Alloy Catalysts A Pd alloy composite membrane for hydrogen sepa- California Inst. Technol., US Appl. 2011/0,003,683 ration is prepared by depositing a layer of Pd on a Pt-based alloys containing <50 at% Pt plus one or porous metal or ceramic support, preferably Ni, using more of Zr,Ti,Hf,Nb,Co,Ni,Fe,Pd,Ru,Rh,Re,Os or a dry sputtering deposition process;depositing a layer Ir in a continuous film on a nanoparticle support are of Cu on the Pd layer; and heat treating to form an claimed for use in the cathode of a PEMFC or a alloy. Optionally a first layer of Ag, Ni, Cu, Ru or Mo DMFC. The alloy may be nanocrystalline with a grain may be formed before depositing Pd.

Platinum Apparatus for Producing Glass MEDICAL AND DENTAL Nippon Electric Glass Co Ltd, Japanese Appl. 2010-228,942 Ruthenium Compounds for Treating Cancer Glass manufacturing apparatus which reduces the Univ. Strasbourg, World Appl. 2011/001,109 formation of bubbles in optical or display glass is claimed.A dry coating containing a glass powder and Ru compounds for treating proliferative diseases, in a ceramic powder is formed on the outer surface of a particular cancer, are claimed, together with pharma- Pt container. The coated Pt container is then sur- ceutical compositions containing the same. Preferred rounded by a refractory layer containing >97 wt% compounds include 1 and 2.

Al2O3 and SiO2 and fired.

World Appl. 2011/001,109 ELECTRICAL AND ELECTRONICS + Gas Discharge Lamp with Iridium Electrode Koninklijke Philips Electronics NV, US Appl. 2010/0,301,746 N N A gas discharge lamp includes a gas discharge vessel N – filled with S, Se, Te or a compound thereof and an Ru PF6 electrode assembly in which the electron-emissive N material is 80–100 wt% Ir optionally alloyed with Ru, O N Os, Rh, Pd or Pt. The Ir-based electrode has a high O melting point and resists chemical reaction with the gas filling, providing a long-lived, efficient, compact 1 and high intensity white light source for applications such as general and professional illumination. + Integrated Rhodium Contacts N IBM Corp, US Patent 7,843,067 (2010) N N – A microelectronic structure contains an interconnect Ru PF6 barrier layer of Ta, Ti, W,Mo or their nitrides, between N a Rh contact structure and a Cu interconnect struc- N ture. Interdiffusion between Rh and Cu is prevented and low resistance in microelectronic devices can be achieved. 2

FINAL ANALYSIS Flame Spray Pyrolysis: A Unique Facility for the Production of Nanopowders

Flame spray pyrolysis can be used to produce a How it Works wide array of high purity nanopowders ranging Flame spray pyrolysis is a one step process in which from single metal oxides such as alumina to more a liquid feed – a metal precursor(s) dissolved in a complex mixed oxides, metals and catalysts. The solvent – is sprayed with an oxidising gas into a flame technique was first developed by the research group zone. The spray is combusted and the precursor(s) of Sotiris E. Pratsinis at ETH Zurich, Switzerland (1). are converted into nanosized metal or metal oxide Since then it has been used to create new and particles, depending on the metal and the operating sophisticated materials for catalysis and other conditions. The technique is flexible and allows the applications (2). use of a wide range of precursors, solvents and Johnson Matthey has developed its own Flame process conditions, thus providing control over parti- Spray Pyrolysis Facility (Figure 1) which produces cle size and composition. a range of nanopowders using the flame spray pyrolysis technique. It has the capacity to produce up to Materials Synthesised 100 g h−1 of nanopowder product, depending on the A range of oxide-based materials have been prepared material composition, and a number of process vari- using the technique and some examples are illus- ables enable the preparation of well-defined target trated in Table I. Some of these materials find uses materials. in catalysis, electronics, thin film applications and

Fig. 1. Johnson Matthey’s development-scale Flame Spray Pyrolysis Facility, housed at the Johnson Matthey Technology Centre, Sonning Common, UK. It offers a unique facility for the production for nanopowders

Table I Properties of Selected Metal Oxides Prepared by Flame Spray Pyrolysis

Material Particle sizea, Specific surface Phase identification nm areab, m2g−1

γ δ Al2O3 10–15 ~100 Mixture of - and -Al2O3

CeO2 10–15 80–100 Cubic CeO2

ZnO 8–15 60–90 Mainly tetragonal ZrO2

TiO2 25 80–100 Mainly anatase and trace of rutile

Doped TiO2 30 90–100 Mainly rutile and traces of anatase aDetermined by TEM analysis bDetermined by BET analysis other areas. Additionally the transferable knowledge was fed into the spray at 5 ml min−1 in an oxygen gained can be applied to the synthesis of pgm cata- stream of 5 l min−1. The spray was then combusted lysts and supported pgm catalysts by the flame spray with a pre-ignited flame of methane/oxygen. The method. resulting product (Figure 2) had a specific surface area of 145 m2 g−1 with a Pd dispersion around 30% as Case Study: A Palladium Catalyst for determined by CO chemisorption. Fine Chemicals Synthesis The catalyst was tested in the hydrogenation of

A 2 wt% Pd/Al2O3 catalyst was prepared from an nitrobenzene to produce aniline, using 0.5 g of organometallic palladium compound and an alu- nitrobenzene in 5 ml of ethanol at 3 bar and 50ºC. Its minium alkoxide in a organic solvent. The solution performance was found to be comparable to that of

commercially available Pd/Al2O3 and Pd/C catalysts. This demonstrates that the Pd particles in the flame spray samples are well dispersed throughout the support and give rise to a high metal surface area available for catalysis. Study of the effects of the process parameters including spray conditions and precursor chemistry on catalyst characteristics is ongoing.

Conclusion The flame spray pyrolysis technique allows for the preparation of a vast range of materials, including metastable phases, due to the rapid quenching process. Johnson Matthey has dedicated much effort to the application of the technique to the synthesis of catalysts. Further scale-up will be critical and work is ongoing via an EU funded project aimed at achieving −1 5 nm a production capacity over 10 kg h .To increase our know-how and satisfy other interest areas, more work utilising the technique is also ongoing via other EU Fig. 2. Transmission electron microscopy (TEM) image and UK Technology Strategy Board (TSB) funded of a flame made Pd/Al2O3 catalyst with Pd nanoparticles highlighted by red arrows projects.

Acknowledgement References The creation of the development-scale Flame Spray 1 R. Strobel, A. Baiker and S. E. Pratsinis, Adv. Powder Pyrolysis Facility at JMTC, Sonning Common, was Technol., 2006, 17, (5), 457 partly funded by a grant provided by the UK’s for- 2 R. Strobel and S. E. Pratsinis, Platinum Metals Rev., mer Department of Trade and Industry (DTI) under 2009, 53, (1), 11 its Micro and Nano Technology (“MNT”) Network initiative. The Author DR BÉNÉDICTE THIÉBAUT Dr Bénédicte Thiébaut joined Johnson Matthey twelve years ago and worked on numerous projects specialising in the last seven Johnson Matthey Technology Centre, Blounts Court, years in the nanotechnology area. She initially investigated the Sonning Common, Reading RG4 9NH UK synthesis of nanomaterials by solution routes and turned her interest to other methodologies including the flame spray pyrolysis E-mail: [email protected] (FSP) technique.

Jonathan Butler Publications Manager Sara Coles Assistant Editor Margery Ryan Editorial Assistant Keith White Principal Information Scientist

E-mail: [email protected]

Platinum Metals Review is the quarterly E-journal supporting research on the science and technology of the platinum group metals and developments in their application in industry http://www.platinummetalsreview.com/ Platinum Metals Review Johnson Matthey Plc, Precious Metals Marketing, Orchard Road, Royston, Hertfordshire SG8 5HE, UK E-mail: [email protected] http://www.platinummetalsreview.com/