PLATINUM METALS REVIEW a Quarterly Survey of Research on the Platinum Metals and of Developments in Their Application in Industry

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PLATINUM METALS REVIEW A Quarterly Survey of Research on the Platinum Metals and of Developments in their Application in Industry www.platinummetalsreview.com

VOL. 48 OCTOBER 2004 NO. 4 Contents

Ruthenium Vinylidene Complexes 148 By Valerian Dragutan and Ileana Dragutan 13th International Congress on Catalysis 154 A conference review by Alvaro Amieiro-Fonseca, Janet M. Fisher and Sonia Garcia Oxidation States of Ruthenium and Osmium 157 A book review by C. F. J. Barnard and S. C. Bennett Iridium-Based Hexacyanometallate Thin Films 159 in Aqueous Electrolytes By Kasem K. Kasem and Leslie Huddleston Increased Luminescent Lifetimes of Ru(II) Complexes 168 Carbon Nanotube Particulates in Electron Emitters 168 Palladium-Iron Dispersed in Carbon 168 Catalysis by Gold/Platinum Group Metals 169 By David T. Thompson The Discoverers of the Osmium Isotopes 173 By J. W. Arblaster Fundamentals of Kinetics and Catalysis 180 A book review by Tim Watling Bicentenary of Four Platinum Group Metals 182 By W. P. Griffith Abstracts 190 New Patents 193 Indexes to Volume 48 195

Communications should be addressed to: The Editor, Susan V. Ashton, Platinum Metals Review, [email protected] Johnson Matthey Public Limited Company, Hatton Garden, London EC1N 8EE DOI: 10.1595/147106704X4835 Ruthenium Vinylidene Complexes SYNTHESES AND APPLICATIONS IN METATHESIS CATALYSIS

By Valerian Dragutan* and Ileana Dragutan Institute of Organic Chemistry, Romanian Academy, 202B Spl. Independentei, PO Box 15-254, 060023 Bucharest, Romania; *E-mail: [email protected]

This paper surveys an attractive family of ruthenium complexes with great potential for applications in organic and polymer synthesis. When compared with traditional ruthenium alkylidene pre-catalysts, these alternative ruthenium vinylidene complexes are easily accessible from commercial starting materials. In addition, they display moderate to high metathesis activity and stability, and exhibit good tolerance towards an array of functional groups, air and moisture. Their synthesis, physical-chemical properties and catalytic attributes indicate they are quite promising initiators of efficient applications in ring-closing metathesis, cross metathesis and ring-opening metathesis polymerisation.

Previous papers recently published in this These ruthenium complexes enjoyed consider- Journal have highlighted the role and scope of plat- able popularity within the organic synthesis inum group metals in the development of community, especially the neutral 16-electron metathesis catalysts (1, 2). Following the seminal ruthenium bisphosphane benzylidene complex 3, discovery of the highly active and stereoselective which combines good activity with high tolerance tungsten and molybdenum imido alkylidene towards many organic functionalities, air and mois- metathesis catalysts, for example, 1 and 2 (R = ture. Many improvements in the preparation of classical Grubbs’ catalysts have subsequently been performed (7, 8) and different variations of the lig- and sphere of complex 3 have been created. These Me HC Me HC 2 CHMe2 2 CHMe2 N N include: Schiff base ligated complexes 5 (9–11), N- heterocyclic carbene complexes 6 and 7 (12–14), RO W Me Mo Me Me RO Me and isopropoxy tethered benzylidene complexes 8 RO RO Ph Ph (15). However, their synthesis via hazardous dia- 12 R' N N N Mes Mes alkyl groups) by Schrock and coworkers (3, 4), an Cl ORu Ru important class of ruthenium bisphosphane alkyli- Cl Ph Cl Ph PCy3 dene catalysts, for example, 3 and 4, have been PR3 56 PR Cl 3 Ph PR3 R' Cl PR Ru Ru R' Cl 3 Cl Cl N N H Mes Mes Ru PR3 PR3 Cl Cl Ru Ph 34 Cl O PCy3 R = phenyl (Ph), isopropyl (iPr) or cyclohexyl (Cy) R' = phenyl (Ph) or tert-butyl (tBu) groups 78 R = phenyl (Ph), isopropyl (iPr) or cyclohexyl (Cy) disclosed and successfully applied in metathesis R' = phenyl (Ph) or tert-butyl (tBu) groups reactions by Grubbs and coworkers (5, 6). Mes = mesityl

Platinum Metals Rev., 2004, 48, (4), 148–153 148 22 eq.eq PR 3 PR3 H R' Cl H 1/2 Ru _ Ru C C (i) - p-cymene Cl Cl Cl 2 R' PR3 910

zoalkane derivatives remains of considerable con- cymene)]2, see Equation (i). Unfortunately, these cern. complexes showed only moderate metathesis In order to circumvent this important drawback activity in processes such as RCM of unsubstituted of ruthenium benzylidene complexes, research has α,ω-dienes and ROMP of highly strained nor- been directed to produce alternative metathesis ini- bornenes (19). tiators of comparable performance but easier New cationic 18-electron ruthenium vinylidene accessibility from commercial ruthenium sources complexes, for example, 11, 12 and 13, were (16, 17). The present paper reviews the class of designed, prepared and screened for their metathe- ruthenium vinylidene complexes applied as effi- sis activity by Grubbs and coworkers (20) but their cient pre-catalysts in olefin metathesis reactions, applicability remained limited to a small range of such as cross metathesis (CM), ring-closing olefinic substrates. metathesis (RCM) and ring-opening metathesis More effective neutral and cationic 16- and 18- polymerisation (ROMP). electron ruthenium tridentate complexes, for example, 14, 15 and 16, were easily synthesised by Ruthenium Vinylidene Complexes: van Koten and coworkers (21) by treating the

Syntheses and Catalytic Properties ruthenium complex [RuCl2(NN'N )(PPh3)] (where A first set of neutral 16-electron ruthenium NN'N is 2,6-bis[(dimethylamino)methyl]pyridine vinylidene complexes 10 was easily prepared by ligand) with 2 equivalents of Ag[BF4], in CH2Cl2, in Katayama and Ozawa (18) from common terminal the presence of an excess of phenylacetylene (iso- alkynes and the arene ruthenium dimer 9, [RuCl2(p- lated yield 95%), see Equation (ii).

N N N Ph N N N Ph Ph Ru C C PF6 Ru C C PF6 Ru C C PF6 Cl PCy3 Cl PCy 3 Cl PCy3 11 12 13

Ph H Ph H Ph H C C C C NMe C C N 2 NMe NMe Ru N 2 PF6 N 2 PF6 Ru Ru N Cl Me Cl N PPh3 N PPh3 2 Me2 Cl Me2 OTf 14 15 16

Platinum Metals Rev., 2004, 48, (4) 149 2 Ph H C Ph N NMe N C 2 NMe2 2 BF Ru 4 (ii) Cl 2 eq.eq Ag[BF ] Ru Me N 4 2 PPh Me2 N PPh3 Cl 3 CH2Cl2,, 95% 16a

Significantly, a highly active and selective, coor- dene complexes coordinated with an imidazolyli- dinatively unsaturated, ruthenium 16-electron dene ligand (22). This class of ruthenium dicationic complex, 16a, was found to quantitative- complexes, including complexes with formula 17 ly promote ROMP of norbornene to [IMes = 1,3-(2',4',6'-trimethylphenyl)imidazol-2- polynorbornene under mild conditions, in the ylidene, R = Cy, R' = tBu] and 18 (iPrIM = absence of any cocatalyst (Scheme I). The IR, 1H 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, R' and 13C{1H} NMR spectra of the polynorbornene = Ph) has been prepared directly from the bispho- obtained under the above conditions indicated sphane ruthenium complex 10 (R = Cy) and free 90–95% trans C=C, in accordance with similar imidazoline carbenes or their salts (Scheme II). results reported previously (12). Of these two complexes, 17 and 18, the ruthe- Substantial progress was made by Louie and nium compound 17, possessing a mixed ligand Grubbs through the synthesis of ruthenium vinyli- system, displayed a substantial metathesis activity

CC22HH4Cl4Cl2,2 80ºC,,80°C,1h 1h YieldYield 100% 100% 2n n Ph H 2 C C N NMe2 Ru Me2 N PPh3 16a Scheme I

IMes Cl H IMes Ru C C Cl R' PR3 PR3 Cl H 17 17 Ru C C Cl R' PR3 iPrIM 22 eq eq. iPrIM 10 Cl H 9 Ru C C Cl R' iPrIM 18 18 Scheme II

Platinum Metals Rev., 2004, 48, (4) 150 EtO2C CO Et 2 17 CO2Et (iii) Yield 86% CO2Et

IMes IMes H tBu Cl H 1/2 Cl Ru Ru C C (iv) Cl - p-cymene Ru Cl IMes Cl tBu Cl 2 92019

IMes IMes Cl H H Cl H H Ru C C H2C C Ru CH2 C CC (v) Cl tBu R Cl R tBu 19 21

EtO2C CO Et 2 19 CO2Et (vi)

Yield 95-96% CO2Et

19 2 (vii) Yield 93%

19 n/2 (viii) Yield 95% n in RCM of diethyl diallylmalonate to substituted proved to be superior to that of the ruthenium cycloolefin (Equation (iii)), although the reaction complex 17, supporting the concept of a higher rate was slower than that with the parent bisimida- degree of unsaturation in the coordination sphere zolylidene ruthenium carbene complex. of the metal promoting catalysis. The pathway for Detailed mechanistic investigations of the generation of the true catalyst 21 from the catalyst ruthenium-catalysed metathesis chemistry strongly precursor 19, by reaction with an olefin substrate, indicated that increased ligand dissociation (that is can be seen in Equation (v). of phosphane) is necessary to accelerate initiation The particular catalytic behaviour of the pre- and thereby enhance catalytic activity in this type catalyst 19 in the RCM of diethyl diallylmalonate, of reaction. Thus, a phosphane-free coordinatively metathesis homodimerisation CM of allyl benzene unsaturated ruthenium vinylidene complex 19 can and ROMP of 1,5-cyclooctadiene is compared in be formed directly in situ from the commercial Equations (vi), (vii) and (viii). It is worth noting ruthenium dimer 9, N-heterocyclic carbene (IMes) that the solvent (hexane or tetrahydrofuran) plays as such or as its salts, and a terminal alkyne an important role in the in situ generation of the (Equation (iv)). ruthenium catalyst from these starting materials. Indeed, the catalytic activity of complex 19 Another interesting array of ruthenium vinyli-

Platinum Metals Rev., 2004, 48, (4) 151 Me Br Me Br 1. TlOEt, THF/RT R R N N Me PCy3 H Me 2. Cl O Ru CC H R' OH Ru C C Cl Cl R' PCy3 PCy3 10 22 Scheme III dene complexes, 22, containing Schiff bases as complexes displayed considerably high RCM chelating ligands, was prepared by Verpoort and activity. Combining vinylidene ligands with other coworkers (23–26) from ruthenium vinylidene specific ligands (such as imidazolylidene, Schiff complex 10 and various aromatic salicylaldimines, bases, etc.), in the coordination sphere of the see Scheme III in which R = H or NO2 and R' = ruthenium core, allows further access to highly

Ph, tBu or Me3Si. This class of ruthenium com- efficient ruthenium metathesis pre-catalysts. plexes, easily accessible from [RuCl2(p-cymene)]2, 9, terminal akynes and salicylaldimine salts, References showed good activity in olefin metathesis and enol 1 V. Dragutan, I. Dragutan and A. T. Balaban, ester synthesis due to the “one-arm” de-coordina- Platinum Metals Rev., 2001, 45, (4), 155 tion ability of the bidentate Schiff base ligand 2 (a) V. Dragutan, I. Dragutan and A. T. Balaban, Platinum Metals Rev., 2000, 44, (2), 58; (b) V. creating unsaturation in the coordination sphere of Dragutan, I. Dragutan and A. T. Balaban, Platinum the metal. These complexes, 22, have also been Metals Rev., 2000, 44, (3), 112; (c) V. Dragutan, I. found to serve as excellent pre-catalysts in the Dragutan and A. T. Balaban, Platinum Metals Rev., 2000, 44, (4), 168 RCM of α,ω-dienes and the ROMP of nor- 3 (a) R. R. Schrock and A. H. Hoveyda, Angew. Chem. bornene, substituted norbornene, cyclooctene and Int. Ed., 2003, 42, 4592; (b) C. J. Schaverien, R. R. polycyclic olefins. Moreover, the related rutheni- Schrock and J. C. Dewan, J. Am. Chem. Soc., 1986, 108, 2771; (c) R. R. Schrock, D. T. DePue, J. um vinylidene complexes that contain Feldman, C. J. Schaverien, J. C. Dewan and A. H. imidazolin-2-ylidene ligands displayed consider- Liu, J. Am. Chem. Soc., 1987, 109, 1423 able stability, even for several days at high 4 (a) R. O’Dell, D. H. McConville, G. H. Hofmeister temperature (24). and R. R. Schrock, J. Am. Chem. Soc., 1994, 116, 3414; (b) D. H. McConville, J. R. Wolf and R. R. Schrock, J. Am. Chem. Soc., 1993, 115, 4413 Conclusions 5 (a) R. H. Grubbs (ed.), “Handbook of Metathesis”, Applying ruthenium vinylidene complexes in Wiley-VCH, Weinheim, 2003; (b) P. Schwab, R. H. olefin metathesis reactions (RCM, CM, ROMP) Grubbs and J. W. Ziller, J. Am. Chem. Soc., 1996, 118, 100; (c) B. M. Novak and R. H. Grubbs, J. Am. seems to be a convenient alternative to the classi- Chem. Soc., 1988, 110, 7542 cal ruthenium bisphosphane catalysts largely 6 (a) S. T. Nguyen, L. K. Johnson, R. H. Grubbs and employed in organic synthesis and polymer chem- J. W. Ziller, J. Am. Chem. Soc., 1992, 114, 3974; (b) S. T. Nguyen, R. H. Grubbs and J. W. Ziller, J. Am. istry. Due to the particular steric and electronic Chem. Soc., 1993, 115, 9858 environment provided by the ligands, some of the 7 (a) T. R. Belderrain and R. H. Grubbs, vinylidene ruthenium complexes exhibit remark- Organometallics, 1997, 16, 4001; (b) T. E. Wilhelm, T. able activity and selectivity. They are readily R. Belderrain, S. N. Brown and R. H. Grubbs, Organometallics, 1997, 16, 3867 accessible, only requiring commercially available 8 J. Wolf, W. Stuer, C. Grunwald, H. Werner, P. starting materials for their synthesis. Importantly, Schwab and M. Schulz, Angew. Chem. Int. Ed., 1998, when generated in situ, coordinatively unsaturated 37, 1124

Platinum Metals Rev., 2004, 48, (4) 152 9 S. Chang, L. R. Jones, C. Wang, L. M. Henling and The Authors R. H. Grubbs, Organometallics, 1998, 17, 3460 Valerian Dragutan is a Senior 10 (a) B. De Clercq and F. Verpoort, Tetrahedron Lett., Researcher at the Institute of 2001, 42, 8959; (b) B. De Clercq and F. Verpoort, Organic Chemistry of the Romanian Academy. His Adv. Synth. Catal., 2002, 344, 639 research interests are 11 (a) B. De Clercq and F. Verpoort, J. Mol. Catal. A: homogeneous catalysis by Chem., 2002, 180, 67; (b) T. Opstal and F. Verpoort, transition metals and Lewis Angew. Chem. Int. Ed., 2003, 42, 2876 acids; olefin metathesis and ROMP of cycloolefins; 12 T. Weskamp, W. C. Schattenmann, M. Spiegler and bioactive organometallic W. A. Herrmann, Angew. Chem. Int. Ed., 1998, 37, compounds; and mechanisms 2490 and stereochemistry of 13 J. K. Huang, E. D. Stevens, S. P. Nolan and J. L. reactions in organic and Petersen, J. Am. Chem. Soc., 1999, 121, 2674 polymer chemistry. 14 (a) M. Scholl, T. M. Trnka, J. P. Morgan and R. H. Grubbs, Tetrahedron Lett., 1999, 40, 2247; (b) M. Scholl, S. Ding, C. W. Lee and R. H. Grubbs, Org. Ileana Dragutan is a Senior Lett., 1999, 1, 953 Researcher at the Institute of 15 (a) J. P. A. Harrity, D. S. La, M. S. Visser and A. H. Organic Chemistry of the Hoveyda, J. Am. Chem. Soc., 1998, 120, 2343; (b) J. S. Romanian Academy. Her Kingsbury, J. P. A. Harrity, P. J. Bonetatebus and A. interests are in sterically H. Hoveyda, J. Am. Chem. Soc., 1999, 121, 791 hindered amines, syntheses of olefinic monomers via 16 (a) A. Demonceau, A. W. Stumpf, E. Saive and A. F. olefin metathesis, stable Noels, Macromolecules, 1997, 30, 3127; (b) A. W. organic free radicals as spin Stumpf, E. Saive, A. Demonceau and A. F. Noels, J. probes for ESR of organised Chem. Soc., Chem. Commun., 1995, 1127 systems and membrane bioenergetics. She is also 17 (a) A. Hafner, A. Muhlebach and P. A. Van der interested in transition metal Schaaf, Angew. Chem. Int. Ed., 1997, 36, 2121; (b) A. complexes with free radical Furstner and L. Ackermann, Chem. Commun., 1999, ligands. (1), 95; (c) M. Picquet, C. Bruneau and P. H. Dixneuf, Chem. Commun., 1998, (20), 2249 18 (a) H. Katayama and F. Ozawa, Organometallics, 1998, 17, 5190; (b) H. Katayama and F. Ozawa, Chem. Lett., 1998, 27, (1), 67 19 C. Bruneau and P. H. Dixneuf, Acc. Chem. Res., 1999, 32, 311 20 M. S. Sanford, L. M. Henling and R. H. Grubbs, Organometallics, 1998, 17, 5384 21 I. del Río and G. van Koten, Tetrahedron Lett., 1999, 40, 1401 22 J. Louie and R. H. Grubbs, Angew. Chem. Int. Ed., 2001, 40, 247 23 T. Opstal and F. Verpoort, J. Mol. Catal. A: Chem., 2003, 200, 49 24 T. Opstal and F. Verpoort, Synlett, 2002, 935 25 T. Opstal and F. Verpoort, Tetrahedron Lett., 2002, 43, 9259 26 T. Opstal and F. Verpoort, Synlett, 2003, 314

Platinum Metals Rev., 2004, 48, (4) 153 DOI: 10.1595/147106704X5708 13th International Congress on Catalysis

Reviewed by Alvaro Amieiro-Fonseca, Janet M. Fisher* and Sonia Garcia Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.; *E-mail: [email protected]

The 13th ICC was held in Paris from 11th to the surface are key for the nucleation of metal 16th July 2004 and attracted more than 1800 dele- hydroxides. Platinum (Pt) and Ru catalysts (up to 5 gates representing 62 different countries (1). There wt.%) with 1 nm sized metal particles have been were 169 oral communications and well over 1000 obtained on such supports using deposition pre- posters. The programme of the congress was cipitation procedures. divided into 6 topical sessions: Professor G. Somorjai (University of California, [1] Catalyst preparation and characterisation U.S.A.) presented an interesting talk showing a [2] Catalytic reaction mechanisms new method to produce Pt nanoparticles. These [3] Catalytic reaction engineering: multi-scale particles were produced via size reduction pho- approach tolithography. The Pt nanoparticles were prepared [4] Fuels and energy for the future in aqueous solution using polymer templates and [5] Synthesis of chemicals and polymers: towards then encapsulated with silica to form mesoporous cleaner processes and atom economy, and silicate structures. Both reactions occur in the same [6] Pollution, prevention and remediation. solution, giving catalysts with high surface area and It is impossible to review adequately even a part offering a certain degree of control over particle of the conference because of the sheer scale and size. The formation of Pt nanowires inside zeolite number of parallel sessions, but we hope that what channels using various Pt salts and UV radiation follows will provide a snapshot of a few of the top- was reported by Professor A. Fukuoka (Hokkaido ics covered. University, Sapporo, Japan). The size and shape of the wires could be altered by use of various ligands Plenary Lecture by Noyori and different zeolites. The zeolite was removed by Chemistry Nobel Laureate Professor Ryoji leaching in HF and samples of the wires were Noyori (RIKEN, Saitama, Japan) gave a plenary shown to have good selectivity for the preferential lecture entitled ‘Molecular catalysis, today and oxidation of CO in H2 streams (PROX). tomorrow’. He drew particular attention to the Attila Wootsch (University of Poitiers, France) need to carry out reactions with high atom effi- talked about the PROX reaction over Pt/alumina ciency and a low E-factor (kg waste generated/kg and Pt/ceria-zirconia catalysts. The benefit of product produced). He described a new cleaner using a reducible oxide such as ceria was ratio- route to adipic acid starting with cyclohexene and nalised. The role of Cl– poisoning was discussed; hydrogen peroxide but avoiding the production of Cl– slows oxygen mobility over Pt surfaces and nitrous oxide (N2O). Asymmetric hydrogenation inhibits the water gas shift reaction. of carbon-carbon double bonds with ruthenium S. Shaikhutdinov (Fritz-Haber Institute, Berlin, (Ru) and rhodium (Rh) BINAP catalysts was also Germany) compared Pd(111) single crystals and discussed. Pd nanoparticles on ordered alumina films for reactions with alkenes. Hydrogenation of alkenes Highlights: Nano Work and Ruthenium occurred with nanoparticles but not with single Professor K. P. de Jong (University of Utrecht, crystals. This observation was rationalised in terms The Netherlands) reviewed the physico-chemical of hydrogen storage on the Pd. The accessibility of aspects of the preparation of supported catalysts. subsurface hydrogen was enhanced on the parti- Elegant work using carbon nanofibre materials as cles rather than on the single crystal due to the supports was discussed. Carboxylic acid groups on nanoscale dimensions.

Platinum Metals Rev., 2004, 48, (4), 154–156 154 Ru catalysts supported on multiwalled carbon tion spectroscopy (PM-IRAS) and thermal desorp- nanotubes (MWNTs) for the catalytic wet air oxi- tion spectroscopy. A nice example of how surface dation of aniline were discussed by Professor J. L. science studies on model catalysts relate to real cat- Faria (University of Porto, Portugal). Ru was intro- alyst behaviour using the most sophisticated UHV duced into MWNTs by oxidation with nitric acid, (ultra high vacuum) techniques. which yielded carboxylic groups used to anchor the metallic Ru. The catalysts obtained showed Catalysis Involving Biomass high activities due to the high external surface area The production of H2 from biomass offers of the MWNTs that offered an efficient surface some attractions since it is a CO2 neutral energy contact between the aniline and the Ru. supply. Professor K. Seshan (University of An interesting talk by K. Tominaga (National Twente, The Netherlands) described the steam

Institute of Advanced Industrial Science and reforming of acetic acid over a Pt/ZrO4 catalyst. Technology, Ibaraki, Japan) covered the hydro- Acetic acid is one of the major components of bio- formylation of alkenes with carbon dioxide using oil, which can be obtained from biomass by flash chloride salts and ruthenium carbonyl complexes. pyrolysis. The deactivation of the catalyst was Professor Graham J. Hutchings (Cardiff found to parallel acetone formation, indicating that University, U.K.) reported on the direct synthesis the surface species (coke) formed from the acetic of hydrogen peroxide. Pd catalysts are more active acid decomposition blocks the reforming reaction than Au catalysts for this reaction but Au-Pd sup- and acts as a surface intermediate for the acetone ported on titania is even more reactive giving 56 formation. –1 –1 mol kg cat h of H2O2. This theme was continued by A. Efstathiou There were many other papers focused on gold (University of Cyprus, Nicosia) who discussed a catalysis, and the majority were concerned with process using a CO2 absorption step during bio- reactivity or modelling of low temperature CO oxi- mass reforming to shift the equilibrium towards dation. Other gold papers covered propene greater hydrogen production. This led to the use of epoxidation and various other organic oxidation Fe-MgO technology combined with platinum reactions (2). group metal/CeO2 standard materials. A Rh-MgO catalyst exhibited very high activity. Plenary Lecture by Iglesia Professor L. Schmidt (University of Minnesota, Using examples of alkane activation Professor U.S.A.) described the partial oxidation of highly E. Iglesia (University of California, Berkeley, volatile ethanol and biodiesel using an original air U.S.A.) in a plenary lecture, emphasised the impor- and fuel injection system. The set-up allows high tance of isotopic labelling exchange and in situ temperature mixing without pre-reaction pyrolysis. spectroscopy to elucidate mechanism and charac- The hydrogen yields were good for a range of C to terise intermediates. On Ni, Rh, Pt and Ru O ratios. catalysts, kinetic and isotopic methods confirmed The plenary and award lectures from the 13th the relevance of the C-H bond activation step. ICC will be published in a special issue of Catalysis Turnover frequency studies showed that the con- Reviews (3). The 14th ICC is to be held in Seoul, centration of coreactants, such as CO2 or H2O, Korea, in July 2008 (4). was not important in the process. Turnover fre- quencies were similar to those seen for the References decomposition of methane to C and H2. 1 13th Int. Congress on Catalysis, Paris, France, G. Rupprechter (Fritz-Haber Institute, Berlin, 11-16 July 2004; http://www.13icc.jussieu.fr/ 2 D. T. Thompson, Platinum Metals Rev., 2004, 48, (4), Germany) compared CO and C2H4 hydrogenation 169 over a model catalyst comprising Pd- 3 Catalysis Reviews; http://www.dekker.com/ Al2O3/NiAl(110) and a single Pd (111) crystal 4 14th Int. Congress on Catalysis, Seoul, Korea, July using polarised modulation IR reflection absorp- 2005; http://www.icc2008korea.com/

Platinum Metals Rev., 2004, 48, (4) 155 The Reviewers Janet Fisher is a Alvaro Amieiro-Fonseca is a research Principal Scientist at scientist at the Johnson Matthey the Johnson Matthey Technology Centre, Sonning Technology Centre, Common, U.K. He is interested in Sonning Common, developing new materials and U.K. Her primary applications in heterogeneous interests are in catalysis and understanding surface catalyst preparation mechanism. and characterisation.

Sonia Garcia is a Marie Curie Fellow at the Johnson Matthey Technology Centre, Sonning Common. She is interested in the synthesis of noble metal nanoparticles for catalytic applications.

Platinum Metals Rev., 2004, 48, (4) 156 DOI: 10.1595/147106704X10801 Oxidation States of Ruthenium and Osmium COMPREHENSIVE COORDINATION CHEMISTRY II. FROM BIOLOGY TO NANOTECHNOLOGY

Volume 5 TRANSITION METAL GROUPS 7 AND 8 EDITED BY E. C. CONSTABLE AND J. R. DILWORTH; EDITORS-IN-CHIEF, JON A. McCLEVERTY AND THOMAS J. MEYER, Elsevier, Amsterdam, 2003, 876 pages, ISBN 0-08-0443273 (Volume 5); ISBN 0-08-0437486 (Set), U.S.$ 5975, €6274 per Set

Reviewed by C. F. J. Barnard* and S. C. Bennett Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.; *E-mail: [email protected]

Volume 5 in the book set “Comprehensive nated by the chemistry of complexes containing Coordination Chemistry II” (CCCII) presents a the bipyridine (bpy) ligand. survey of important developments in the chemistry Many complex ligands designed to extend the of the transition metals of Groups 7 and 8: man- conjugation of the aromatic system or otherwise ganese, technetium, rhenium, iron, ruthenium (Ru) modify the electronic properties of the complex, and osmium (Os), published from 1982 to 2002. have been prepared. The complexes can be simple 2+ Volumes 6 and 9 in this 10 book set, covering mononuclear species, such as [Ru(bpy)3] , dinu- n+ work on the other platinum group metals have clear [(bpy)2Ru(µ-L)Ru(bpy)2] or polynuclear. been previously reviewed (1, 2). In Volume 5, the material for each element is organised by oxidation High Oxidation States state of the metal and also by the nature of the lig- The high oxidation states of ruthenium and ands involved, with additional sections covering osmium are areas that are generally only very light- special features of the coordination chemistry and ly covered by most chemistry reference books, applications of the complexes. However, only the even those that are dedicated to the chemistry of oxidation states of ruthenium and osmium are platinum group metals and catalysis. Happily in reviewed here. this 2nd edition of “Comprehensive Coordination Chemistry” this matter is very much set right. In Low Oxidation States Chapter 5.6 on ‘Rutheniun and osmium: high oxi- In Chapter 5.5 entitled ‘Ruthenium and osmi- dation states’ by Chi-Ming Che and Tai-Chu Lau, um: low oxidation states’ by Catherine E. the VIII to IV oxidation states receive over 100 Housecroft, the low oxidation states of ruthenium pages and more than 600 references detailing all and osmium are covered. Relatively little work has the work that has been published in this area from been done for the 0 and +III oxidation states since 1982 to 2002. the earlier volume, published in 1987, in contrast The structure of the review is clear and concise to the large amount of work on the +II oxidation with separate sections for all the five high oxida- state. The chemistry of the 0 oxidation state is tion states covered. Inside each of these sections largely organometallic, and this is dealt with in the complexes are classified according to the ligands companion series: “Comprehensive Organometallic involved, covered so that one finds nitrogen-ligat- Chemistry”. ed complexes first, then oxo complexes, followed Much of the work on the +II state is due to the by sulfur, halide, hydride and finally any miscella- interesting photochemical properties of, in partic- neous ligands not already covered. This enables the ular, ruthenium bearing heterocyclic nitrogen reader to use the review as a quick and powerful ligands. Such complexes have been studied for the reference tool to find out about a specific area of photoreduction of water and used as sensitising interest. dyes in photochemical cells with similar levels of Sensibly the authors begin their review of the performance to silicon cells. The section is domi- literature in this area by looking at Ru(VIII) and

Platinum Metals Rev., 2004, 48, (4), 157–158 157 Os(VIII) as it is from here that many of the VII to synthetic, spectroscopic and electrochemical infor- IV complexes are prepared. Although not very mation it contains make this an absolutely vital much new material is covered for ruthenium, the reference for anyone working with Ru or Os in catalytic properties of osmium tetroxide are cov- their VIII to IV oxidation states, or for those ered in some depth particularly the dihydroxylation working with their low oxidation states. of and aminohydroxylation of alkenes. Several new osmium oxo halo complexes are also included and References references are given for their synthesis routes and 1 A. K. Keep, Platinum Metals Rev., 2004, 48, (2), 64 X-ray structures. 2 J. M. Fisher, R. J. Potter and C. F. J. Barnard, Platinum Metals Rev., 2004, 48, (3), 101 The main area covered in the VII oxidation state is the use of perruthenate as a selective oxidant for the conversion of alcohols to aldehydes or The Reviewers – ketones with a variety of co-oxidants, but [OsO4] is also mentioned even though relatively little work has been published on this system. By the time we reach the Ru(VI) and Os(VI) section the amount of material covered becomes too great to be covered in this short review. Not surprisingly the majority of the chemistry here involves multiple metal-ligand bonds particularly the nitrodo complexes, and a wealth of spectroscopic and X-ray data and references are supplied to support the earlier literature. The Ru(VI) and Os(VI) polypyridyl and oxo complexes almost deserve a book in their own right, but all the key areas are covered in this sub- Chris Barnard, who reviewed Chapter 5.5, is a Scientific Consultant section including the electrochemistry of these in the Liquid Phase Catalysis Group at the Johnson Matthey complexes, their IR spectra and X-ray structures, Technology Centre, U.K., with interests in homogeneous catalysis employing the platinum group metals. He is also interested in the not forgetting their use as oxidants of both organ- application of platinum compounds for cancer therapy. ic and inorganic substrates – complete with kinetic data! Compared to the (VI) oxidation state section, the (V) oxidation state section at first appears to be rather frugal, but it soon becomes clear that this is as a result of the instability of many of these systems. Despite this there is still plenty of structural, spectroscopic and electrochemical data for these complexes. Finally we come to the large (IV) oxidation state section where once again the nitrogen- and oxygen-based ligands dominate. As expected by now, the chemistry, spectroscopy and structures of these complexes are all covered in detail and sufficient references are supplied so that anyone starting to Steve Bennett, who reviewed Chapter 5.6, is a Senior Scientist at work in this area would rapidly become proficient. the Johnson Matthey Technology Centre. His main interests are the parallel screening of both homogeneous and heterogeneous Overall the authors are to be congratulated on platinum group metal catalysts in selective oxidation and their review of this specialist area. The wealth of hydrogenation reactions.

Platinum Metals Rev., 2004, 48, (4) 158 DOI: 10.1595/147106704X5942 Iridium-Based Hexacyanometallate Thin Films in Aqueous Electrolytes SOME OF THEIR ELECTROCHEMICAL AND CATALYTIC BEHAVIOURS

By Kasem K. Kasem* and Leslie Huddleston Department of Natural, Mathematical and Information Sciences, Indiana University Kokomo, Kokomo, IN 46904-9003, U.S.A. *E-mail: [email protected]

Thin films of metal-hexacyanoiridium(III) (MHCI), KxMy[Ir(CN)6]z, where M = Ru, Fe were electrochemically prepared and used as surface modifiers for glassy carbon electrodes. The redox behaviour of the counter/central ions of these films was investigated in aqueous electrolytes using cyclic voltammetry, chronocoulometry and electrochemical impedance spectroscopy.

An electrochemical synthesis of zeolite-like films of KxMy[Ir(CN)6]z and KxFey[Fe(CN)6]z (Prussian blue) was also undertaken using the cyclic voltammetric technique. Porous multifilm assemblies of Prussian blue and MHCI were formed either by the direct electrodeposition of Prussian blue over MHCI or Prussian blue over MHCI during repetitive potential cycling, or by electrochemically-driven insertion-substitution methods. In acidic aqueous KCl, iron o hexacyano iridate (FeHCI) displays two redox waves with formal potential E f ≈ 0.35 and 0.6 V vs. Ag/AgCl. The electrochemical behaviour of FeHCI was compared with that of related

hexacyanometallate compounds, such as KRux[Ru(CN)6]y, KRux[Fe(CN)6]y and KFex[Fe(CN)6]y. In addition, evidence for the catalytic behaviour of MHCI films towards the reduction of iodate, – IO3 , is reported.

Immobilised mixed-valence hexacyanometal- films can proceed without dissolution of the solid lates (HCM) or hexahalometallates, for example compound as the film maintains its neutrality by an –y KFex[Fe(CN)6]y or M X6 , respectively, (where X ion diffusion process, and = Cl, Br, M = iron (Fe), iridium (Ir), ruthenium • second, the formation of a bi- or multilayered (Ru), etc. and y is the charge) and related com- structure is possible using an insertion-substitution pounds are an important class of polynuclear mechanism. compounds. Their ability to form a conducting Hexacyanometallates also possess these charac- polymer that resembles zeolitic or intercalation teristic features of redox active solid films. The material, as well as redox organic polymers, has composition, thickness and structure of HCM thin attracted the attention of many investigators films can also be manipulated to serve a desired (1–15). Prussian blue is an excellent example of an use and to expand some features that can be used HCM compound. Earlier studies of Prussian blue in industrial applications. Multilayered (8–10) were carried out more than two decades ago (2, 4) insoluble films of HCM have important applica- and substantiate the interest in further research of tions in membrane chemistry. Some of the studies related compounds. As transition metals with dif- cited here focus on the preparation of multilayered ferent formal oxidation states occupy the counter films, carried out either by electrodeposition of one ion and the central ion sites, different redox cen- film over the other, or by mechanical mixing of tres are created within host thin films. two insoluble HCMs. Two major characteristics of this class of inor- In addition, several studies have been carried ganic redox film promote its usefulness for out on HCMs in which the central atoms were Ru possible applications: (16–19), cobalt (1), nickel (12), vanadium (20) or • first, the oxidation or reduction of these solid chromium (21). A limited number of studies

Platinum Metals Rev., 2004, 48, (4), 159–167 159 (22–25) have been performed on Kx[Ir(CN)6]y, but electrochemical experiments were carried out by with no mention of the redox behaviour of this deoxygenation in a nitrogen (N2 99.99%) atmos- compound. Like most of the platinum metals, irid- phere at room temperature (25.1ºC). ium oxide shows great electrocatalytic activity. Electrode Modification: Thin solid films of

This indicates that iridium compounds possess KFex[Ir(CN)6]y were electrodeposited via oxidative promising features as electron acceptors/donors electropolymerisation on the glassy carbon elec- or depolarisers in biological membranes, and more trode surfaces by repetitive potential cycling of a investigations are needed to understand the redox GCE between –0.30 and +1.2 V vs. Ag/AgCl, in behaviour of Ir-based HCMs. freshly prepared aqueous solutions containing an

This paper reports new studies into the electro- equiv. 0.5 mM of K3[Ir(CN)6].2H2O, either FeCl3 chemical behaviour of multilayered film assemblies or RuCl3, and 40 mM KCl (pH 2). Scans were car- where iron and iridium are the redox centres in ried out at a sweep rate of 100 mV s–1. The

KMx[Ir(CN)6]y. Furthermore, as ruthenium hexa- electrodes were then rinsed thoroughly and trans- cyanoferrate has a zeolite-like structure (26), ferred to reactant-free electrolyte where their

KFex[Ir(CN)6]y deposits are expected to have sim- electrochemical response was examined. The elec- ilar structure. An alternate method for the trode surface coverage (Γ) of this thin film was preparation of zeolite-like multifilm assemblies of determined by integrating the areas under the iridium-based HCMs with bi-, or trivalent cations voltammetric i-E curves. substituted as counter ions is discussed. Evidence A sheathing (overlaying) procedure was used to for the catalytic activities of these assemblies on form a multifilm assembly. This included depositing the electrode surfaces is presented. KxFey[Ir(CN)6]z on the electrode surface to form the

inner layer followed by deposition of KxFey[Fe(CN)6]z Instrumentation and Methods over the modified electrode using a similar method Experiments were carried out using a conven- to that used to deposit the inner layer. tional three-electrode type electrochemical cell. The reference electrode was a Ag/AgCl (saturated Results and Discussion III III KCl) half-cell of potential –45 mV vs. SCE. The Electrodeposition of KFex [Ir (CN)6]y III III counter (auxiliary) electrode was a platinum (Pt) Evidence of formation of KFex [Ir (CN)6]y wire, and the working electrode was a glassy car- can be detected from the cyclic voltammograms bon disk electrode (GCE) of surface area 0.071 shown in Figure 1 for the GCE in aqueous solu- cm2. The working electrode was cleaned by polish- tions containing equiv. 0.5 mM of ing with 1 µm α-alumina paste and rinsed with K3[Ir(CN)6].2H2O, and FeCl3 and 40 mM of KCl water and acetone prior to use. An electrochemical (pH 2). The growth of the redox wave as succes- analyser was used to perform the electrochemical sive scanning took place is indicative of the studies and X-ray photoelectron spectra (XPS) build-up of redox potential film. Notice that the with typical depth analysis of 5–50 Å were record- anodic current is always greater than the cathodic ed. The deposited films on the electrode surfaces current. Such behaviour can be attributed to the were examined by scanning electron microscopy. difference in the kinetics of the oxidation and Impedance Measurement: Electrochemical reduction processes in the film. impedance spectroscopy (EIS) studies were carried + II III out. Faradic impedance measurements were per- Rate of K Fex [Ir (CN)6]y Deposition formed within a frequency range of 0.1 mHz to 1 The slope of the plot of ipa (anodic peak cur- kHz. The current response was monitored and the rent) vs. the number of cycles as a function of time data were analysed by a Fourier transformation (Figure 1A) averages 1.04 × 10–6 µC/cycle. algorithm. Considering the effective time of deposition per Chronocoulometry: Experiments were per- cycle is 2 seconds, the rate of film build up is 0.52 formed with pulses of width 50 ms. All the µC s–1. This rate is equivalent to a surface coverage

Platinum Metals Rev., 2004, 48, (4) 160 –1 Fig. 1 Repetitive cyclic voltammetry at 0.1V s of a glassy carbon electrode (GCE) in equivalent 1 mM of K3[Ir(CN)6] and FeCl3 in 50 mM KCl/HCl (pH = 2). Scan started at –0.20 V vs. Ag/AgCl 1A Plot of anodic peak current (ipa) vs. number of cycles 1B Anodic peak potential (Epa) vs. number of cycles of 7.7 × 10–11 mol cm–2/cycle. Figure 1A also shows an irregular-linear relationship between the shows that ipa reached a maximum after 17 cycles recorded anodic peak potential and the number of and then became steady. This suggests that 20 cycles up to 25 cycles, after which it maintains cycles are enough to make a stable film with better constant value. Such behaviour indicates that the mechanical properties than thicker films. electrode/electrolyte interface was in steady change and reached constant structure after 25 III III Structure of KFex [Ir (CN)6]y cycles. This causes multi-interface systems, con- 3– Because of the small difference in radius among sisting of native GCE/[Ir(CN)6] and immobilised 3– 3– transition metal ions, calculation of the unit cell [Ir(CN)6] /free [Ir(CN)6] , to coexist. However, dimensions was performed as previously described after the first 14 cycles the surface coverage of 3– in the literature (9). The calculated unit cell dimen- immobilised [Ir(CN)6] was sufficient to create sions suggest that the monolayer thickness is ≈ one monolayer structure of immobilised 3– 10.4 Å. This corresponds to a molar volume of [Ir(CN)6] . This monolayer was insufficient to cre- 677.16 cm3 mol–1. The calculated monolayer equiv- ate an interface that would give steady current and alence based on the dimension of 10.4 Å is 10.75 potential (Figures 1B and 1A) as both the current × 10–10 mol cm–2. Accordingly, this means that and potentials kept changing. approximately 14 cycles are needed to cover the The steady rise in the current, see Figure 1A, electrode surface with the first layer. could be evidence for film porosity, as a one The effect of this structure on the interfacial monolayer film allowed redox ions through its net- potential between the modified electrode and the work structure to be in contact with the active sites solution is demonstrated in Figure 1B which on the native electrode surface.

Platinum Metals Rev., 2004, 48, (4) 161 Fig. 2 Scanning electron micrograph of polynuclear hexacyanoiridium(III) films on a GCE surface. The accelerating voltage is 0.8 kV

between 300 and 500 eV. In particular, the signals at 495 eV support the Ir-O bonding that can be attributed to Ir(III) being surrounded by 6 O atoms. However, signals appearing between 705 and 725 eV indicate mixed valence Fe atoms coordinated with oxygen (Fe-O). This is evidence for the coexistence of Fe(II)-O and Fe(III)-O. The peak Spectroscopic Characterisation at 290 eV corresponds to C in the CN group, while Figure 2 is a scanning electron micrograph of the N peak is at 400 eV. It has been previously the film formed on the GCE substrate. Figure 2 reported that multivalent oxides of transition met- shows a highly crystalline deposit of cubic shape als can be codeposited from cyanometallate with dimensions of ~ 200 nm. The discontinuity of solutions at pH 2 (1, 27). this crystalline structure as well as its disordered III III packing makes film porosity highly likely. The XPS Redox Behaviour of KFex [Ir (CN)6]y Films spectrum of the film formed (Figure 2) is shown in The general formula of hexacyanometallates X Y Figure 3. In Figure 3, the peaks corresponding to (HCMs) can be written as MMA [MB (CN)6]Z; M X Y the trivalent iridium are identifiable by several represents main group metals, while MA and MB peaks between 60 and 66 eV, at 105 eV, and are generally transition metals. The reduction of

Fig. 3 X-ray photoelectron spectra (XPS) showing the binding energies and intensities of peaks of the aggregates shown in Figure 2

Platinum Metals Rev., 2004, 48, (4) 162 Fig. 4A Cyclic voltammogram of a GCE modified with KxFey[Ir(CN)6]z in 50 mM KCl/HCl at scan rates: 0.05 V s–1 (----); 0.50 V s–1 (----); 0. 200 V s–1 (—) 4B Nyquist plot at 0.7 V; 4C Nyquist plot at 0.5 V Units: (1E+5 ohm) = 1 × 105 ohm; (1E+4 ohm) = 1 × 104 ohm the fixed counter cations of these compounds can (lower part) at 0.520 and 0.80 V are shown in the take place via electron/cation addition according anodic scan. Such behaviour depends on the scan to the Equation: rate. The dotted and dashed cyclic voltammogram

X Y + X–1 Y in Figure 4 indicates that by decreasing the scan MA [MB (CN) ]Z + 1e + M → MMA [MB (CN) ]Z (i) 6 6 rate both the reduction and oxidation peaks while oxidation of the central atom can take place become well defined. Notice that the reduction of by electron loss followed by the anion addition Fe(III) as a counter ion becomes more identifiable needed for charge balance without affecting the at a lower scan rate. Unlike the formal redox wave coordination number/sphere (2): reported for immobilised iron hexacyanoruthen-

X Y – X Y+1 ate, KxFey[Ru(CN)6]z (7), the formal redox wave of MA [MB (CN)6]Z – 1e + X → MA [MB (CN) X]Z (ii) 6 iron counter ions appears at a more positive As the deposited redox centres are totally potential (~ 0.375 V) and at a very low scan rate. immobilised, the charge transfer process is con- Furthermore, the formal potential of the central Ir 3– trolled by the mobility of the K or Cl ions (from atom in the [Ir(CN)6] redox wave was at ~ 0.680 the supporting electrolyte) and by electron hop- V which is 100 mV less positive than that report- 3– ping. ed for IrCl6 (28). Scanning the potential of a GCE, modified The phenomena of such ill-defined redox III III –1 III III with KFex [Ir (CN)6]y at 200 mV s between waves in KFex [Ir (CN)6]y at scan rates faster –0.40 and 1.20 V in 0.1M KCl, produced the solid than 10 mV s–1 distinguish it from other studied line cyclic voltammogram shown in Figure 4. The HCM. Figure 4 shows at scan rates faster than 10 cathodic scan (upper part) shows a broader reduc- mV s–1, that total overlapped waves having a for- tion peak at 0.520 V, while two anodic peaks mal redox centre closer to that of the central Ir ion

Platinum Metals Rev., 2004, 48, (4) 163 interstitial sites of octahedral [Ir(CN)6]3, the charge balance to these sites requires the removal of K+ ions and the diffusion of Cl– ions. The kinetics of this process may affect the magnitude of the impedance measured at this potential. The equivalent circuit for the film assembly can be pictured as an ohmic resistance (RΩ) in series with a paralleled

double layer capacitor (Cdl) with charge transfer

resistance (Rct), see inset in Figure 4. At 0.7 V, when both the Ir and Fe cations involved in the network structure of this assembly are in their highest oxidation states, the number of K+ ions needed for charge balance in the film assembly is reduced. This will hinder self diffusion in the film. Calculations from the impedance measurement

showed that the diffusion coefficent (Dct) was 2.2 Fig. 5A Cyclic voltammogram at 0.05 V s–1 of a GCE × 10–9 cm2 s–1. This quantity is in agreement with modified with KxFey[Ir(CN)6]z in 50 mM KCl/HCl 2– 3– 5B Cyclic voltammogram after the GCE was immersed Dct determined for IrCl6 or [Fe(CN)6] immo- 2+ 2+ in Cu for 120 minutes bilised in poly Ru(vbpy)3 at the saturation level

where the ratio of surface coverage of M (ΓM) to occur. This indicates there is slow charge transfer that of the polymer (ΓPoly) is (ΓM/ΓPoly ≥ 0.3) (29). in the counter Fe ion centre. Obtaining a well- defined Fe redox wave at (~ 0.375 V) at a slow Stability of KFex[Ir(CN)6]y Film 2+ scan rate confirms this conclusion. The fact that Cu -Substituted KFex[Ir(CN)6]y the compact (3d ) orbital in Fe has less metal- GCEs modified with a thin film of donor atom bonding than the more expanded (5d ) KFex[Ir(CN)6]y undergo structural alteration by orbital in the Ir ion makes Ir ions soft acids. Unlike substitution of the counter Fe3+ ion by Cu2+ (d 9). the Ru in KxFey[Ru(CN)6]z no Ir oxides are being This is achieved by cycling the potential of the formed. The fact that KxFey[Ru(CN)6]z shows sim- GCE modified with KFex[Ir(CN)6]y thin film in the ilar electrochemical behaviour to KxFey[Fe(CN)6]z, desired metal ion acidic solution. The results, see III III 2+ but different to that of KFex [Ir (CN)6]y may Figures 5A and 5B, indicate that Cu partially sub- indicate the effect of expanded (5d ) orbitals in the stituted the Fe counter ions in the film. Ir ions. Figures 5A and 5B show the redox wave of the The Nyquist plots, which predict the stability film after 2 hours of Cu substitution (Figure 5B). and performance of a closed-loop system by This has not only affected the Fe redox wave, but observing its open-loop behaviour, see Figures 4B has also decreased the total amount of redox active and 4C for a 1.49 nm film, show combined diffu- materials by ~ 25% of the initial amount. Unlike sional behaviour (mass transfer is the significant Prussian blue, which is fully substituted in under 2 factor) with no sign of charge saturation, and a hours, KFex[Ir(CN)6]y is less susceptible to substi- kinetically controlled charge transfer process. The tution. greater Z in Figure 4C (at 0.5 V) compared to that in Figure 4B (at 0.7 V) reflects the importance of Formation of Zeolite-Like Bilayer Cl– ions in charge balance when both iron and irid- Film Assembly ium are in their highest stable oxidation states. Formation of Multi-Film Assemblies However, when impedance measurements are car- The sheathing method previously described was ried out at 0.5 V, only the counter ion Fe is performed and the results are shown in Figure 6. oxidised (d 5 Fe3+). As the counter ion occupies the Figure 6A shows the cyclic voltammogram

Platinum Metals Rev., 2004, 48, (4) 164 Fig. 6A Cyclic voltammogram of a GCE modified with Prussian blue under KxFey[Ir(CN)6]z in KCl/HCl 6B Cyclic voltammogram of a GCE modified with KxFey[Ir(CN)6]z under Prussian blue in KCl/HCl. Scan rates: (----) at 0.005 V s–1, (—) at 0.01V s–1 obtained for a modified GCE with an assembly of in the formal potentials of these redox waves, as

KxFey[Fe(CN)6]z (Prussian blue) as the inner layers observed when comparing the cyclic voltammo- and KxFey[Ir(CN)6]z as the outer/upper layers in a grams in Figures 6A and 6B. The fact that the 1:1 ratio (equal surface coverage of 1.97 × 10–9 mol redox wave at ~ 0.75 V is much larger in Figure 6B cm–2). The redox waves of the Ir-related centres than in Figure 6A may indicate that the upper overlap with that of the central Fe atom in KxFey[Ir(CN)6]z layer is more porous than Prussian Prussian blue at 0.75 V. The redox wave at 0.20 V blue. This will allow more transport of ions need- is due to the counter Fe atom in the Prussian blue ed for electrical neutrality when both the central inner layer, while the redox wave of the counter Fe ions in Prussian blue and KxFey[Ir(CN)6]z are oxi- atom in the upper layer has an ill-developed anod- dised or reduced. The cyclic voltammogram for ic peak at 0.4 V. The fact that this redox wave the film assembly created indicates perfect surface exists suggests that the counter Fe ions in this waves with smaller double layer capacitive current. assembly have two different redox potentials depending upon the central ion with which they Evidence of Catalytic Activity associate. Due to the structure of the bi-film The catalytic activity of KxFey[Ir(CN)6]z was – (which includes both Ir and Fe as central ions) two tested using the IO3 as a soft base with +7 oxida- redox potentials of central Fe and Ir ions coexist tion state iodine atom. There was no technological and overlap. Figure 6B shows the cyclic voltam- significance behind the choice of that anion in this mogram obtained for a modified GCE with an study. Modified GCEs with thin films of assembly of KxFey[Ir(CN)6]z as the inner layers and KxFey[Ir(CN)6]z exhibited electrocatalytic activities – KxFey[Fe(CN)6]z (Prussian blue) as the towards the reduction/oxidation of IO3 . outer/upper layers in a 1:1 ratio. Evidence for such catalytic behaviour can be seen The order in which the layers are placed or in the cyclic voltammograms obtained in an acidic o formed affects the magnitude of the capacitive solution of KIO3 (E f = 0.4 V vs. Ag/AgCl), see current. It also affects the shape of the collective Figure 7A. A carbon paste electrode of the same redox waves in the assembly with very little change apparent geometrical area was used to confirm

Platinum Metals Rev., 2004, 48, (4) 165 – –1 Fig. 7 Electrolytic catalytic activities towards the reduction of IO3 in aqueous KCl (pH = 1); scan rate 0.01 V s 7A 1 Naturally occurring/Native GCE in 0.05 M KIO3 (KCl/HCl) 2 GCE modified with KxFey[Ir(CN)6]z in KCl/HCl 3 GCE modified with KxFey[Ir(CN)6]z in 0.05 M KIO3 7B 2 GCE modified with Kx–1RhyFe[Ir(CN)6]z in KCl/HCl 3 GCE modified with Kx–1RhyFe[Ir(CN)6]z in 0.5 M KIO3 that the reduction peaks shown in Figure 6 were behaviour of thin films of iridium-based HCMs not due to an increase in electrode surface area. differs from those of (3d ) and (4d ) metals-based Native GCE shows a reduction peak at 0.430 V HCM. The formation of higher oxidation state (Figure 7A, line 1) whereas modified GCE with oxides in proximity to cyanide complexes was

KxFey[Ir(CN)6]z (Figure 7A, line 3) shows reduc- noticed with (3d ) or (4d ) metals. This was not the tion peaks with greater cathodic currents at 0.6 and case for Ir-based HCM. The expanded valence 0.45 V. The larger cathodic current is due to the shell of the Ir ion in which its (5d ) electrons are 14 catalytic effect of KxFey[Ir(CN)6]z. Furthermore, preceded by 4f create a soft acid nature for Ir (II doping the film with an element from the same or III) ions as a central atom. The reactivity of its group as Ir (Rh) did not improve the catalytic 6-π acceptor ligand (CN–) with Ir ions may be con- activity. This can be concluded from Figure 7B sidered when comparing the redox behaviour of (line 3), which represents the behaviour of GCEs (5d ) metal-based HCM with those of (3d ) or (4d ) modified with Kx–1RhyFe[Ir(CN)6]z under the same metal-based HCMs. The catalytic activity of Ir- experimental conditions. It can be noted that less based HCM agrees with that of most of the studied catalytic current is generated from doped film than HCM and can be explained on the basis of an elec- from undoped film. The observed catalytic current tron/proton transfer process. in Figure 7 is due to the reduction of iodate to iodide according to the Equation: References – + – IO3 + 6H + 6e → I + 3H2O (iii) 1 Z. Gao, G. Wang, P. Li and Z. Zhao, Electrochim. Acta, 1991, 36, 147 2 K. Itaya, H. Akahoshi, and S. Toshima, J. Electrochem. Conclusions Soc., 1985, 128, (7), 1498 This study shows evidence of the efficient 3 L. M. Siperko and T. Kuwana, J. Electrochem. Soc., manipulation of Ir-HCM film structures to a 1983, 130, 396 desired composition and porosity. The redox 4 V. D. Neff, J. Electrochem. Soc., 1978, 125, 886

Platinum Metals Rev., 2004, 48, (4) 166 5 K. K. Kasem, J. Appl. Electrochem., 1999, 29, 1473 6 T. R. Cataldi, C. E. de Benedetto and C. Campa, J. Electroanal. Chem., 1997, 437, 93 7 K. K. Kasem, Mater. Sci. Eng., 2001, B83, 97 8 A. Dostal, M. Hermes and F. Scholtz, J. Electroanal. Chem., 1996, 415, 133 9 S. J. Reddy, A. Dostal and F. Scholtz, J. Electroanal. Chem., 1996, 403, 209 10 K. Kasem, R. Hazen and R. M. Spaulding, Interface Sci., 2002, 10, 261 11 D. Olaf, L. Sabine, H. Frank and B. Michael. J. Exp. The Authors Bot., 1990, 41, (230), 1055 12 L. Hartwig and B. Michael, Plant Physiol., 1988, 86, Kasem K. Kasem is a Professor of Chemistry at Indiana University Kokomo, U.S.A. He is interested in developments in the field of (4), 1044 applied electrochemistry, especially in physical and analytical 13 K. K. Kasem, J. Appl. Electrochem., 2001, 31, 1125 applications of chemically-modified electrodes. He also has 14 S. Ohkoski, A. Fujishima and K. Hashimoto, J. Am. interests in semiconductor electrochemistry, the electrochemical Chem. Soc., 1998, 120, 5349 behaviour of polymeric thin films, activation and metallisation of polymers, and the electrodeposition of metals and alloys. 15 J. A. Cox and R. K. Kulkarni, Talanta, 1986, 33, (11), 911 Leslie Huddleston was an undergraduate at Indiana University 16 J. A. Cox. and P. J. Kulesza, Anal. Chem., 1988, 5, Kokomo, U.S.A. when she worked on this project. She obtained (16), 1021 her BS in chemistry at Kokomo and is currectly working in industry. 17 J. A. Cox, J. Electroanal. Chem., 1987, 233, (1–2), 87 18 P. J. Kulesza, J. Electroanal. Chem., 1987, 220, (2), 295 19 T. R. Cataldi, C. E. De Benedetto and C. Campa, J. Electroanal. Chem., 1998, 458, 149 20 Y. Wang, G. Zhu and E. Wang, J. Electroanal. Chem., 1997, 430, 127 21 J. P. Eaton and D. Nicholls, Transition Met. Chem., 1981, 6, 203 22 N. M. Pinhal and N. V. Vugman, Hyperfine Interactions, 1989, 52, (1), 89 23 N. V. Vugman and N. M. Pinhal, Inst. Fis., Rio de Janeiro Univ., Brazil, Report, 1983, (UFRJ-IF- 10/83), AN (1984) 166787 24 N. V. Vugman and N. M. Pinhal, Mol. Phys., 1983, 49, (6), 1315 25 N. V. Vugman, R. P. A. Muniz and J. J. Danon, J. Chem. Phys., 1972, 57, (3), 1297 26 K. Kasem, F. R. Steldt, T. J. Miller, and A. N. Zimmerman, Microporous Mesoporous Mater., 2003, 66, 133 27 W. Gorski and J. A. Cox, Anal. Chem., 1994, 66, 736 28 W. Sun, H. Liu, J. Kong, G. Xie and J. Deng, J. Electroanal Chem., 1997, 437, 67 29 K. Kasem and F. A. Schultz, J. Inorg. Organomet. Polym., 1994, 4, (4), 377

Platinum Metals Rev., 2004, 48, (4) 167 DOI: 10.1595/147106704X13411 Increased Luminescent Lifetimes of Ru(II) Complexes Photovoltaic systems for solar light harvesting (the energy reservoir) is in the tpy moiety not offer a potential route to low power electricity. involved in the 3MLCT emitting level, while the 2- Ruthenium (Ru) complexes with a bpy (2,2'-bipyri- pyrimidyl-tpy subunit is involved in extended dine) ligand have traditionally been used in this electron delocalisation. research and in Grätzel cells, as they have excellent In their method, the 9-anthryl chromophore is 2+ photophysical properties. Ru(tpy)2 (2,2':6',2''-ter- inserted into the 4'-position of the tpy moiety, giv- pyridine) is a chromophore that has been used in ing a 4'-(9-anthryl)-2,2':6',2''-tpy Ru(II) complex. multinuclear structures, but its room temperature This started bichromophoric behaviour by lower- 3 2+ excited-state lifetime is < 250 ps. Longer lifetimes ing the MLCT state of Ru(tpy)2 via the have been obtained for Ru(II) terpyridine complex- 2-pyrimidyl-tpy subunit, and increased the lumines- es where one tpy ligand is attached to a coplanar cence lifetimes because of the excited-state pyrimidine while the other tpy moiety has a 9- equilibrium. The luminescence lifetimes are long 2+ anthryl organic chromophore. The longer lifetimes compared to those for Ru(tpy)2 . are due to a bichromophoric effect (the triplet This method gives separated chromophores on states of the metal-to-ligand charge-transfer different ligands with long-lived excited states. It (3MLCT) and of the anthracene are in equilibrium). may allow special design of the Ru tpy moiety and In this case the Ru and anthryl chromophores are the organic chromophore, and could result in com- on the same ligand and synthesis is not easy. pounds with specific photophysical properties. Now, researchers from the Université de Montréal, Canada, and Università di Messina, Italy, References have synthesised a new series of luminescent 1 M. Grätzel, Platinum Metals Rev., 1994, 38, (4), 151 2+ Ru(tpy)2 species where the chromophores are 2 J. Wang, G. S. Hanan, F. Loiseau and S. Campagna, separated by > 1 nm. The 9-anthryl chromophore Chem. Commun., 2004, (18), 2068 Carbon Nanotube Particulates in Electron Emitters Scientists at Carbon Nanotechnologies, Inc., The C nanotubes can be activated by etching, Houston, Texas, U.S.A., have produced carbon (C) and were blended with a matrix material of ther- nanotubes with one or more walls and outer wall moplastic or thermoset polymer, metal or ceramic. diameters 0.5 to 3 nm (World Patent 2004/048,263). The C nanotube particulates could be well dis- Using a gaseous C-containing feedstock, preferably, persed in the polymers and had high conductivity at methane, but other hydrocarbons, alcohols and/or low loadings. CO are permitted, they contacted a catalyst of Fe, Such pastes of polymers and C nanotubes find Mo, Ru, Rh, Pd, Os, Ir or Pt, on a particulate sup- use in a range of electron emission devices. For port (magnesia of cross-section < 1000 µm) at example, entangled C nanotubes with one or more 500–1500ºC. The C nanotube particulates pro- walls can be used to produce cathode components duced were then annealed and the support material in field emission devices, such as electron discharge was removed. The resulting particulates (enmeshed tubes, amplifiers, and oscillators. As electrical emit- C nanotubes of ropes of cross-section 10–50 nm) ters, the C nanotube particulates exhibit a low ‘turn retained the support’s approximate shape and size. on’ emission field. DOI: 10.1595/147106704X15149 Palladium-Iron Dispersed in Carbon Fine metal or alloy particles dispersed in carbon ments coin-shaped Pd metal particles of ~ 50 nm (C) can be used in catalysis or in magnetic materials. were formed within the carbon layers. Metal is dispersed in C either by the pyrolysis of FeCl3 was then intercalated using the convention- organometallics or by reduction of metal chlorides al two-bulb method. Reduction resulted in Pd and Fe intercalated in graphite. However the method of plac- coexisting within the graphite. To create an alloy the ing alloys in C by intercalation has not yet been sample was further heat treated in high purity argon. successfully achieved. XRD indicated lines of crystallised Pd-Fe alloy. This Now, scientists in Japan (1) have developed a alloy was found to contain 6 wt.% Pd and 15 wt.% Fe. method to disperse fine particles of Pd-Fe alloy in a C matrix. This was achieved first by reduction of PdCl2 Reference with natural graphite flake. After heat and other treat- 1 H. Shioyama and X. Min, Carbon, 2004, 42, (10), 2127

DOI: 10.1595/147106704X15158

Platinum Metals Rev., 2004, 48, (4), 168 168 DOI: 10.1595/147106704X5717 Catalysis by Gold/Platinum Group Metals MIXED METAL SYSTEMS DISPLAYING INCREASED ACTIVITY

By David T. Thompson ‘Newlands’, The Village, Whitchurch Hill, Reading RG8 7PN, U.K.; E-mail: [email protected]

The recent surge of new interest in catalysis by gold (1–3) has led researchers to investigate the effects of adding other metals to the gold. As a result, there are a number of reactions with potential for industrial application where combinations of gold with a platinum group metal (pgm) have been shown to have advantages over either gold or the pgm alone. These findings are expected to lead to applications in chemical processing, pollution control and fuel cell applications. Here, a number of catalytic processes that have benefited from the synergy between a pgm and gold are described, and some interesting reports from recent conferences are highlighted.

One of the major uses of gold/platinum group and use fixed bed processes (5). However, the first metals catalysis is for vinyl acetate monomer fluidised bed process for VAM has now been com- (VAM) production. It is interesting to reflect that missioned by BP, for a new plant in Hull, U.K. (5). VAM has been produced industrially for some The fluidised bed process has been developed by time from acetic acid, ethene and oxygen using pal- BP Chemicals as a more cost effective route, and ladium-gold (Pd-Au) catalysts in fixed bed allows process simplification and intensification. processes. The reaction proceeds with selectivities Compared with the two reactors usually needed in as high as 95% (4): the fixed bed process, the fluidised process requires only a single reactor. A new catalyst was C H + CH COOH + ½O → C H OOCCH + H O 2 4 3 2 2 3 3 2 required for the fluidised operation, and the VAM Work at DuPont by Provine et al. (4) utilising catalyst that was selected is a Au/Pd mix devel- Pd-Au silica-supported catalysts promoted with oped in collaboration with Johnson Matthey in the potassium acetate showed that the addition of gold form of spheres so fine that they almost appear to to palladium can significantly improve the rate of flow as a liquid. Thus, a Au/pgm catalyst is finding production for VAM, see Table I. Around 80% of use on an industrial scale in this process. VAM plants worldwide are more than 20 years old Hydrogen Peroxide Production About 1.9 × 106 tonnes of the oxidising agent Table I hydrogen peroxide (H2O2) are manufactured each year – a very large market (6). There is a need for Yields of Vinyl Acetate Monomer as Reported by DuPont (4) the hydrogen peroxide to be synthesised where it is to be used to avoid the heavy transport costs of Catalyst Space time yield Selectivity, this hazardous material. It is currently only eco- g/l-h % 4 nomic to produce H2O2 on a large scale (4–6 × 10 Au/Pd/KOAc 764 93.6 tonnes/annum) using the sequential hydrogena- Pd/KOAc 100 95.4 tion and oxidation of alkyl anthraquinone, but

Au/Pd 594 91.6 H2O2 is often required on a much smaller scale (6). Pd 124 94.7 Both theoretical calculations (7) and experimental

results (6) have shown that the formation of H2O2 Fixed bed performance of Au/Pd/KOAc catalysts after 40 h on from hydrogen and oxygen is favoured over gold stream. Test conditions: 165ºC, 115 psig, with feed consisting of ethene, acetic acid, oxygen and nitrogen catalysts. Hutchings et al. (6) have shown that H2O2

Platinum Metals Rev., 2004, 48, (4), 169–172 169 Table II Formation of Hydrogen Peroxide from the Reaction between Hydrogen and Oxygen over Au and Pd Catalysts in Methanol under 3.7 MPa Pressure (6)

a Catalyst Temperature, O2/H2 mol ratio H2O2 , K mmol g cat–1 h–1

Au/Al2O3 275 1.2 1530

Au:Pd (1:1)/Al2O3 275 1.2 4460

Pd/Al2O3 275 1.2 370 a Rate of H2O2 formation averaged over 30 min experiments

can be formed at a high rate using a supported gold Au/Pd/Al2O3 catalyst had a higher activity than catalyst at 275 K, with selectivity for H2O2 over a Pd/Al2O3 and the bimetallic catalyst was more

Au/Al2O3 catalyst of 53%. This supported Au cat- resistant to sulfur poisoning. alyst produced more H2O2 than the supported Pd Mixed metal Au/Pt catalysts were reported by catalyst used to-date in industry. However, more Amiridis, Chandler et al. (University of South interestingly, a supported Au/Pd (1:1 by wt.) cata- Carolina, U.S.A.) at the North American Catalysis lyst produces even more H2O2 than the pure Au Society Meeting in Cancun in 2003 (11, 12). Their catalyst. This indicates there is a synergistic effect catalysts were prepared using polyamidoamine with Pd acting as a promoter for the Au catalyst, (PAMAM) dendrimers. Using these as nanoparti- see Table II. Furthermore, they showed that the cle templates and stabilisers, the stabilised metal nanoparticles are in fact Au-Pd alloys. nanoparticles were then adsorbed onto oxide sup-

ports (such as SiO2 or TiO2) and thermally Further Synergistic PGM-Au activated to give supported mixed-metal catalysts. Reactions They were investigated for activity in CO oxida- The addition of gold to palladium by simultane- tion, toluene hydrogenation, and the reduction of ous deposition-precipitation on cerium oxide has NO by propene. Removal of the organic den- been reported to increase the catalytic activity for drimer by heating at 300ºC under an oxygen methanol decomposition to carbon monoxide and stream, followed by treatment at 300ºC under hydrogen at 180ºC (8). No significant promotional flowing hydrogen gave intimately mixed Au/Pt effect was observed by the addition of rhodium or catalysts with metal particle sizes of < 4 nm. The iridium to palladium. resulting Au16Pt16/SiO2 catalyst has a light-off tem-

Venezia and colleagues (ISMN-CNR, Palermo, perature of ~ 30ºC, whereas the equivalent Au32

Italy) have found that bimetallic Au/Pd/SiO2 cat- catalyst lights off at ~ 130ºC and the equivalent alysts with a range of Au:Pd ratios are Pt32 catalyst at ~ 80ºC. advantageous for the hydrodesulfurisation of dibenzothiophene (9). The Au/Pd alloy particles Fuel Cells are resistant to sulfur poisoning compared with a However, it is perhaps in the area of fuel cells pure palladium catalyst. At 553 K, their 1:1 Au:Pd that the biggest potential for using Au/pgms cata- catalyst produced the highest dibenzothiophene lysts may lie. C.-J. Zhong et al. (13) have prepared conversion. Results consistent with these have Au/Pt/C nanoparticle electrocatalysts using a two- been reported by Pawelec et al. (CSIC, Madrid, phase protocol and evaluated them for the oxygen Spain) (10). They have found that, for the simulta- reduction reaction at the fuel cell cathode. Their neous hydrogenation of naphthalene and toluene electrochemical results obtained to-date indicate in the presence of dibenzothiophene, a that the bimetallic Au/Pt catalysts have significant-

Platinum Metals Rev., 2004, 48, (4) 170 ly different electrocatalytic properties to either Au using a Pt/Ru catalyst was also described (22). The or Pt alone. The catalytic activity of Au/Pt is high- gold catalyst increased overall catalyst activity and ly dependent on composition and calcination reduced the tendency to CO poisoning. This could history. Work is continuing on optimising the find application in fuel cells. However, these were properties of these catalysts for use in both acid preliminary results based only on a cyclic voltam- and alkaline fuel cells. mogram screening test. The 13th ICC website The electrooxidation of hydrogen, carbon http://www.13icc.jussieu.fr/ carries two-page monoxide and hydrogen/carbon monoxide abstracts of these noted papers.

(H2/CO) mixtures over well-characterised Au(111)/Pd and Au(100)/Pd surface alloys has Other Literature been studied by Ross and colleagues (14). With the The surface science of Au/pgm catalysts has Au(111)/Pd surface, the oxidation of 1000 ppm been discussed in a recent review paper (23), while

CO in H2 at potentials below 0.2 V is governed by Scurrell et al. (University of Witwatersrand, South the slow H2 oxidation kinetics, but at potentials Africa) (24) have studied bimetallic Au/Ru cata- above 0.2 V the steady state activity of high sur- lysts supported on α-Fe2O3 for the water gas shift face area Au/Pd catalysts can be reached. The reaction. Using atmospheric pressure, the activity investigators claim their results demonstrate that a of the bimetallic system was found to be higher

Pd/Au alloy could be used in principle as a hydro- than for Au/Fe2O3 or Ru/Fe2O3 catalysts over all gen electrode catalyst without any loss of the reaction temperatures studied (373 to 513 K): performance compared with platinum. CO + H2O ↔ H2 + CO2 13th ICC These results have relevance to the supply of Most of the investigations using Au/pgm alloys hydrogen for fuel cells. are still at a very early stage of development, but at the recent 13th International Congress on Conclusions Catalysis (15) there were other interesting reports Thus, from these highlights, it is apparent that on their catalytic properties. For instance, nano- synergism between a pgm and gold, along with sized Pd/Au on carbon has been shown to have other effects, are providing significant potential increased activity over Pd for the selective oxida- for further commercial applications for Au/pgm tion of glyoxal to glyoxalic acid, a key intermediate mixed metal catalysts and alloys. in the synthesis of vanillin (16), and Au/Pd on titania, prepared using a microemulsion technique, References was more active for CO oxidation than the com- 1 M. Haruta, Keynote Talk at the Int. Conf. on the ponent single metal catalysts (17). Alloying gold to Science, Technology and Industrial Applications of Gold, Vancouver, Canada, Sept.–Oct. 2003, Gold palladium has been shown to significantly increase Bull., 2004, 37, (1–2), 27 resistance to sulfur poisoning during benzaldehyde 2 M. Cortie, R. Holliday, A. Laguna, B. Nieuwenhuys hydrogenation (18). Au/Pd was also studied for and D. Thompson, Gold Bull., 2003, 36, (4), 144 the selective hydrogenation of buta-1,3-diene (19); 3 S. A. C. Carabineiro and D. T. Thompson, ‘Catalytic Applications for Gold Nanotechnology’ in and for the formation of H2O2 from hydrogen and “Nanocatalysis: Principles, Methods, Case Studies”, oxygen (see above), investigators from Kyushu Springer Verlag, to be published in 2005 and Oita Universities in Japan reported an opti- 4 W. D. Provine, P. L. Mills and J. J. Lerou, Stud. Surf. Sci. Catal., 1996, 101, 191 mum Au/Pd ratio of 10:7 (20). 5 M. Johnson, ‘Leaps of innovation’, Frontiers, August Pt/Au nanoparticles on HY zeolite have been 2002, Issue 4, pp. 12–15; see found to have a higher activity for hydrocarbon http://www.bp.com/liveassets/bp_internet/glob- albp/STAGING/global_assets/downloads/F/Fro isomerisation reactions than pure Pt (21). ntiers_magazine_issue_4_Leaps_of_innovation.pdf A possible beneficial effect from the presence 6 P. Landon, P. J. Collier, A. J. Papworth, C. J. Kiely of Au/TiO2 on the electrooxidation of methanol and G. J. Hutchings, Chem. Commun., 2002, (18), 2058

Platinum Metals Rev., 2004, 48, (4) 171 The Author 7 P. Paredes Olivera, E. M. Patrito and H. Sellers, Surf. David Thompson is a consultant to Sci., 1994, 313, 25 the World Gold Council and has a 8 M. P. Kapoor, Y. Ichihashi, T. Nakamori and Y. keen interest in the recent upsurge in research in catalysis by gold and its Matsumara, J. Mol. Catal. A: Chem., 2004, 213, 251 use for commercial applications. He 9 A. M. Venezia, V. La Parola, B. Pawelec, J. L. G. is a co-author of a forthcoming book Fierro, Proc. Int. Conf. on the Science, Technol. on this topic. Ind. Applications of Gold, Vancouver, Canada, Sept.–Oct. 2003; see http://gold.dev.cfp.co.uk/discover/sci_indu/gold2003/index.html 10 B. Pawelec, E. Cano-Serrano, J. M. Campos-Martin, R. M. Navarro, S. Thomas and J. L. G. Fierro, Appl. Catal. A: Gen., 2004, 275, 127 11 H. Lang, R. A. May, B. L. Iversen, B. D. Chandler, D. S. Deutsch, L. Sotto and M. D. Amiridis, Proc. 18th North American Catalysis Society Meeting, Cancun, Mexico, June 2003, p. 33 12 B. D. Chandler and H. Lang, Proc. Int. Conf. on the Science, Technology and Industrial Applications of Gold, Vancouver, Canada, Sept.–Oct. 2003; see http://gold.dev.cfp.co.uk/discover/sci_indu/gold2 003/index.html 13 M. M. Maye, N. N. Kariuki, J. Luo, L. Han, P. Njoki, L. Wang, Y. Lin, H. R. Naslund and C.-J. Zhong, Gold Bull., 2004, 37, in press; see also M. M. Maye, J. Luo, L. Han, N. N. Kariuki and C.-J. Zhong, Gold. Bull., 2003, 36, (3), 75 14 T. J. Schmidt, V. Stamenkovic, N. M. Markovic and P. N. Ross, Electrochim. Acta, 2003, 48, 3823 15 Alvaro Amieiro-Fonseca, Janet M. Fisher and Sonia Garcia, Platinum Metals Rev., 2004, 48, (4), 154 16 S. Hermans, S. Vanderheyden and M. Devillers, 13th ICC, Paris, July 2004, 01-030 17 A. Beck, G. Stefler, Zs. Koppány, A. Horváth, I. Sájo, S. Rojas, M. Boutonnet and L. Guczi, 13th ICC, Paris, July 2004, P1-324 18 P. Canton, M. Ferroni, C. Meneghini, F. Pinna, F. Menegazzo, N. Pernicone and A. Benedetti, 13th ICC, Paris, July 2004, 01-052 19 H. Remita, T. Redjala, M. Mostafavi and D. Uzio, 13th ICC, Paris, July 2004, P1-345 20 Y. Hata, S. Yoshida, H. Nishiguchi, Y. Takita and T. Ishihara, 13th ICC, Paris, July 2004, P2-079 21 G. Riahi, M. Gasior, B. Grzybowska, J. Haber, M. Polisset-Thfoin and J. Fraissard, 13th ICC, Paris, July 2004, P1-330 22 D. Y. Kim, J. E. Ahn, H. J. Kim, Y. G. Shul and H. S. Han, 13th ICC, Paris, July 2004, P4-135 23 R. Meyer, C. Lemire, Sh. K. Shaikhutdinov and H.- J. Freund, Gold Bull., 2004, 37, (1–2), 72 24 A. Venugopal, J. Aluha, D. Mogano and M. S. Scurrell, Appl. Catal. A: Gen., 2003, 245, 149

Platinum Metals Rev., 2004, 48, (4) 172 DOI: 10.1595/147106704X4826 The Discoverers of the Osmium Isotopes THE THIRTY-FOUR KNOWN OSMIUM ISOTOPES FOUND BETWEEN 1931 AND 1989

By J. W. Arblaster Coleshill Laboratories, Gorsey Lane, Coleshill, West Midlands B46 1JU, U.K.; E-mail: [email protected]

This is the third in a series of reviews of circumstances surrounding the discoveries of the isotopes of the six platinum group elements; it concerns the discovery of the thirty-four isotopes of osmium. The first review on platinum isotopes was published in this Journal in October 2000, and the second review on iridium isotopes was published in October 2003 (1).

Of the thirty-four isotopes of osmium that we and this remains the presently accepted value (8). know today, seven occur naturally with the follow- Mattauch’s Rule (9) states that if two adjacent ele- ing authorised isotopic abundances (2) (Table I): ments have nuclides of the same mass then at least one of them must be radioactive. In the case of the naturally occurring pair 187Re-187Os, the 187Re is Table I radioactive with a half-life of 4.12 × 1010 years (8). The Naturally Occurring Isotopes of Osmium Since 187Re undergoes beta decay to 187Os, then in Mass number Isotopic abundance, % a mixture of rhenium-platinum element ores, the over-abundance of 187Os with respect to that 184Os 0.02 186 expected for the primordial abundance (the actual Os 1.59 187 186 187 186 187Os 1.96 measurements are Re/ Os and Os/ Os) 188Os 13.24 leads to an estimate of the excess 187Os, and from 189Os 16.15 this is obtained a direct assessment of the age of 190 Os 26.26 the ores. The half-life of 186Os is so long that it can 192Os 40.78 be considered to be “stable” for these measurements. The discovery of the six major isotopes of The use of this cosmochronometer was first osmium was reported by F. W. Aston (Figure 1) in suggested by Clayton in 1963 (10). 1931 (3) after being detected mass spectrographi- cally at the Cavendish Laboratory, Cambridge Artificial Osmium Isotopes University, England. The rare isotope, 184Os, was Prior to 1940 there appears to have been men- discovered by A. O. C. Nier (Figure 2) in 1937 (4) tion of only one radioactive osmium isotope: by using a new type of high resolution mass spec- Kurchatov et al. in 1935 (11) with a half-life of 40 trometer at Harvard University, in Cambridge, hours. This now seems likely to have been 193Os. Massachusetts, U.S.A., where he was carrying out a In 1940 Zingg (12) correctly identified both redetermination of the isotopic abundances of 191Os with a 10 day half-life (modern value 15.4 osmium. Nier’s abundance measurements became days) and 193Os with a 30 hour half-life (the the definitive values for osmium for over half a presently accepted value is 30.11 hours). However, century, only being superseded in 1990 by the mea- immediately afterwards Seaborg and Friedlander surements of Völkening, Walczyk and Heumann (13) switched these around and there then fol- (5). These latter results were immediately incorpo- lowed a bizarre period of seven years in which all rated into the 1991 atomic weight table (6). of the property measurements on 191Os were Of the naturally occurring isotopes, Viola, ascribed to 193Os, and vice versa, until the mistake Roche and Minor suggested in 1974 (7) that 186Os was finally corrected in the 1948 edition of the was radioactive with a half-life of 2.0 × 1015 years, “Table of Isotopes” (14).

Platinum Metals Rev., 2004, 48, (4), 173–179 173 Fig. 1 Francis William Aston 1875–1945 F. W. Aston was born in Harbourne, Birmingham, England, and educated at Birmingham University. In 1909 he joined J. J. Thompson at the Cavendish Laboratory, Cambridge, as his assistant. At that time Thompson was working with positive rays from which he could determine the atomic weights of elements. Thompson noted that for the element neon, in addition to the mass 20, there was always a ghost at mass 22. This suggested the extremely controversial idea that naturally occurring stable elements also had isotopes in addition to those being found for the heavy radioactive elements. After serving in World War I, Aston eventually returned to the Cavendish Laboratory and in 1919 built the first mass spectrograph. He was immediately able to prove that neon contained at least two isotopes of masses 20 and 22 in the ratio 9:1, and thus explained the odd atomic weight of 20.2. In 1920 Aston analysed chlorine and found that it contained two isotopes of masses 35 and 37 in the ratio 3:1. This explained the unusual atomic weight of chlorine which is 35.5. Between 1919 and 1935, and through three generations of mass spectrographs, Aston personally discovered 212 of the 287 naturally occurring nuclides of primordial origin. His determination of nuclide masses showed that they were all very close to whole numbers, and usual differed by a small amount known as the “packing fraction”. By direct measurement or interpolation of the packing fraction it was possible to obtain atomic weights, especially for mononuclidic elements, and these were vastly superior to those being determined by chemical methods. Aston was awarded the 1922 Nobel Prize for Chemistry for the invention of the mass spectrograph

Photo by courtesy of AIP Emilio Sergè Visual Archives, W. F. Meggers Gallery of Nobel Laureates

Fig. 2 Alfred Otto Carl Nier 1911–1994 A. O. C. Nier was born in Saint Paul, Minnesota, U.S.A. and studied at the University of Minnesota where he remained for most of his academic career. After graduating, Nier’s first important contribution was the development of the double focusing mass spectrograph in which, by accelerating a beam of ions through an electrical field at an angle of ninety degrees and then through a magnetic field at an angle of sixty degrees, he was able to increase considerably the resolution of ions of similar atomic mass. This instrument allowed him, in 1935, to discover the rare potassium isotope 40K. From 1936 to 1938 he was at Harvard University, and between 1937 and 1938, he discovered five more rare naturally occurring nuclides: 36S, 46Ca, 48Ca, 184Os and 234U. His accurate measurements of the ratio of uranium isotopes: 235U to 238U in many minerals led to the development of the uranium/lead cosmochronometer. In 1940 he separated 235U from 238U: the first isotope separation, and experiments on 235U proved that it was the fission isotope of uranium, and not the more abundant 238U. This research led to the Manhattan Project, on which he worked from 1943 to 1945. Mass spectrographs, designed by Nier, were used extensively during this time for monitoring 235U to 238U separations. In the early 1950s Nier developed the mass spectrometer which differs from the mass spectrograph in that ion detection is electrical rather than by photographic plate. Between 1956 and 1979 Nier spectrometers were used to measure the masses of nearly all the stable nuclides, while his isotopic abundance measurements for nitrogen, oxygen, the heavy inert gases and the alkaline earth elements became the definitive values for a long time. Nier also developed the miniature mass spectrometers which were used on the Viking Landers sent to Mars to sample the atmosphere

Photo by University of Minnesota, courtesy AIP Emilio Sergè Visual Archives

Platinum Metals Rev., 2004, 48, (4) 174 Table II The Discoverers of the Osmium Isotopes

Mass number Half-life Decay modes Year of Discoverers Ref. Notes discovery*

162 1.87 ms α 1989 Hofmann et al. 17 163 5.5 ms α, EC + β+? 1981 Hofmann et al. 18, 19 A 164 21 ms α, EC + β+ 1981 Hofmann et al. 18, 19 165 71 ms α, EC + β+ 1978 Cabot et al.16B 166 216 ms α, EC + β+ 1977 Cabot et al.15 167 810 ms α, EC + β+ 1977 Cabot et al. 15 168 2.06 s EC + β+, α 1977 Cabot et al. 15 169 3.46 s EC + β+, α 1972 Toth et al. 21 170 7.46 s EC + β+, α 1972 Toth et al. 22 171 8.3 s EC + β+, α 1972 Toth et al. 22 172 19.2 s EC + β+, α 1970 Borgreen and Hyde 23 173 22.4 s EC + β+, α 1970 Borgreen and Hyde 23 174 44 s EC + β+, α 1970 Borgreen and Hyde 23 175 1.4 min EC + β+ 1972 Berlovich et al. 24 176 3.6 min EC + β+ 1970 1: Arlt et al.25 2: de Boer et al. 26 177 3.0 min EC + β+ 1970 Arlt 25 178 5.0 min EC + β+ 1968 Belyaev et al.27 179 6.5 min EC + β+ 1968 Belyaev et al.27 180 21.5 min EC + β+ 1965 1: Belyaev et al. 28, 29 C 2: Hofstetter and Daly 30, 31 181 1.75 h EC + β+ 1966 Hofstetter and Daly 30 D 181m 2.7 min EC + β+ 1966 Hofstetter and Daly 30 E 182 22.10 h EC 1950 Stover 37 183 13.0 h EC + β+ 1950 Stover 37 183m 9.9 h EC + β+, IT 1957 Foster, Hilborn and Yaffe 32 184 Stable – 1937 Nier 4 185 93.6 d EC 1946 Goodman and Pool 38 186 2.0 × 1015 y α 1931 Aston 3 F 187 Stable – 1931 Aston 3 G 188 Stable – 1931 Aston 3 H 189 Stable – 1931 Aston 3 189m 5.8 h IT 1958 Scharff-Goldhaber et al.43I 190 Stable – 1931 Aston 3 190m 9.9 min IT 1955 Aten et al.44 191 15.4 d β– 1940 Zingg 12 191m 13.10 h IT 1952 Swan and Hill 45 192 Stable – 1931 Aston 3 J 192m 5.9 s IT, β– 1973 Pakkenen and Heikkinen 48 K 193 30.11 h β–? 1940 Zingg 12 L 194 6.0 y β– 1951 Lindner 52 195 – β–?M 196 34.9 min β– 1976 Katcoff et al. 58, 59

* The year of discovery is taken as available manuscript and conference dates. Where these are not available then the year of discovery is the publishing date

Platinum Metals Rev., 2004, 48, (4) 175 Table III Notes to Table II

A 163Os Alpha energy only. The half-life was determined by Page et al. in 1995 (20). B 165Os Alpha energy only. The half-life was determined by Hofmann et al. (18, 19). C 180Os In 1957 Foster, Holborn and Yaffe (32) assigned a 23 min half-life activity to 181Os but according to Hofstetter and Daly (30) this now appears to have more likely been 180Os. In 1965 Bedrosyan et al. (33) identified a 23 min half-life activity but did not assign a mass number. D 181Os A 2.7 h half-life activity described by Surkov et al. in 1960 (34) and apparently associated with 181Os was not observed by Hofstetter and Daly (30). Balyaev et al. (29) observed a 2.5 h half-life activity which appeared to confirm the observations of Surkov et al. E 181mOs Hofstetter and Daly’s claim to have identified this isomeric state was only tentative but was confirmed by Goudsmit in 1967 (35). Shortly before the observations of Hofstetter and Daly, Aten and Kapteyn (36) also identified a 2.8 min half-life activity but gave no mass assignment. F 186Os The half-life was measured by Viola, Roche and Minor in 1974 (7). G 187Os Chu in 1950 (39) and Greenlees and Kuo in 1956 (40) observed activities with half-lifes of 35 h and 39 h, respectively, which they suggested could be an isomer of 187Os. However such an activity was not observed by either Newton (41) or Merz (42). H 188Os A 26 d half-life activity suggested by Greenlees and Kuo (40) as being an isomer of 188Os was not observed by Merz (42). I 189mOs A 6 h half-life activity observed by Chu in 1950 (39) and a 7.2 h half-life activity observed by Greenlees and Kuo in 1950 (40) were both likely to have been 189mOs. J 192Os Fremlin and Walters (46) suggested that the isotope, although described as being “stable”, could be radioactive with a half-life exceeding 2.3 × 1014 y. Tretyak and Zdesenko (47) reassessed the data and suggested a revised value of greater than 9.8 × 1012 y which indicates that the suggestion of radioactivity is inconclusive. K 192mOs A 6 s half-life activity assigned to 192Re by Blachot, Monnand and Moussa in 1965 (49) was reassigned to 192mOs by Pakkenen and Heikkinen (48). Hermann et al. (50) almost certainly discovered 192mOs in 1970 but could not decide as to whether it was 192Re or 192mOs. L 193Os A 40 h half-life activity described by Kurchatov et al. in 1935 (11) was assigned to 193Os by the “Table of Isotopes” (51). M 195Os In 1957 Baró and Rey (53) and Rey and Baró (54) identified a 6.5 min half-life activity which they assigned to 195Os, but in 1974 Colle et al. (55) showed that this was the rubidium isotope 81Rb, so 195Os remains undiscovered. Takahashi, Yamada and Kondoh (57) estimated the half-life to be about 9 min.

The most prolific period for the discovery of atomic number, osmium nuclides are likely to be radioactive osmium isotopes was the 1970s with more tightly bound than those for iridium, which fourteen ground states and one isomeric state has an odd atomic number, so it is not surprising being identified. The most discovered by any one that proton decay has not yet been seen from person or group was four by Cabot et al. in 1977 osmium isotopes. (15) and 1978 (16). In Table II, the same criteria for discovery are The lightest osmium isotope, 162Os, still only used as in the prior reviews on platinum and iridi- appears to be an alpha emitter with no evidence of um (1). Notes to Table II, Some of the terms used proton decay, so the drip line for osmium has not for this review, and the decay modes are given in been reached, in contrast to 167Ir for iridium. The Tables III, IV and V. The half-lifes given in the most likely reason for this is that with an even tables are from the revised NUBASE database (8).

Platinum Metals Rev., 2004, 48, (4) 176 Table IV 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 characterised by the 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. Half-life the time taken for the activity of a radioactive nuclide to fall to half 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.

Table V Decay Modes

α Alpha decay is the emittance of alpha particles which are 4He nuclei. Thus the atomic number of the daughter nuclide is lower by two and the mass number is lower by four. β– Beta or electron decay for neutron-rich nuclides is the emittance of an electron (and an anti-neutrino) as a neutron decays to a proton. The mass number of the daughter nucleus remains the same but the atomic number increases by one. β+ Beta or positron decay for neutron-deficient nuclides is the emittance of a positron (and a neutrino) as a proton decays to a neutron. The mass number of the daughter nucleus 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. 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 nucleus 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. However, certain low level states may also decay independently to other nuclides.

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S. Foster, J. W. Hilborn and L. Yaffe, Can. J. Phys., 59 P. E. Haustein, E. M. Franz, R. F. Petry and J. C. 1958, 36, 555 Hill, Phys. Rev., 1977, C16, 1559

Platinum Metals Rev., 2004, 48, (4) 178 The Author John W. Arblaster is Chief Chemist working in metallurgical analysis at Coleshill Laboratories, in the West Midlands of England. He is interested in the history of science and in the evaluation of the thermodynamic and crystallographic properties of the elements.

Platinum Metals Rev., 2003, 47, (4) 179 DOI: 10.1595/147106704X4853 Fundamentals of Kinetics and Catalysis CONCEPTS OF MODERN CATALYSIS AND KINETICS BY I. CHORKENDORFF AND J. W. NIEMANTSVERDRIET, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2003, 469 pages, ISBN 3-527-30574-2; £50; €69

Reviewed by Tim Watling Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.; E-mail: [email protected]

“Concepts of Modern Catalysis and Kinetics” is erogeneous catalysts, but enzyme catalysis is also a comprehensive textbook on heterogeneous catal- mentioned), reaction rate theory (including parti- ysis aimed at students of chemistry, physics or tion functions, collision theory and transition state chemical engineering. While not being specifically theory), characterisation techniques, material prop- about platinum group metals (pgms), much of the erties and catalyst preparation and testing, surface theory, concepts and techniques covered are of rel- reactivity (mostly on electronic aspects) and the evance to pgm catalysts and some of the examples kinetics of surface reactions (mechanism and given are of catalysts containing pgms, although microkinetic modelling). This concludes the chap- equally, many are not. It is thus of some relevance ters on general concepts and theory, which form to readers of this Journal. the bulk of the book. The remaining three chapters As I flicked through the book, my first impres- cover real-world applications of catalysis, for sions were good. The layout is clear with the text example, generation and use of hydrogen (includ- ordered into logical sections. Photographs, figures, ing fuel cells), refining and petrochemistry, and diagrams and tables break up the text. As expected environmental catalysis (including automotive cat- for a book with kinetics in the title, there are many alysts). These three chapters are intended to be an equations. My initial impressions were confirmed overview rather than a comprehensive account, when I began to read the book: the text is well and the reader is referred to more specialist litera- written and easy to follow, with references provid- ture for further information. Finally, as expected ed for the reader who wants to know more. The for a student textbook, there is a section of ques- text is enlivened by snippets of information and tions and exercises. comment. For example, I learned that Arrhenius Important applications of the pgms covered in was studying sucrose hydrolysis when he proposed this book include bifunctional reforming catalysts, his equation, while the breakdown of alcohol in the fuel cells and automotive exhaust catalysts. It is body by alcohol dehydrogenase is described as of particularly pleasing to find a catalysis textbook “some special appeal to students”. which gives automotive exhaust catalysts more This is a book aimed at students, although as so than a token page. The section on three-way cata- often is the case with specialised books, the price lysts covers the principles of operations, how a may put it out of the reach of some potential read- lambda sensor works, monolithic supports, the ers, but a paperback version might remedy this. roles of the various components in the formula- However, I consider that the book goes beyond tion, modes of deactivation and some detail on the the needs of undergraduates as it contains far more mechanism of CO oxidation and CO-NO reac- material than would be covered in a first degree tions. This section would form a useful course. The book would also be suitable for some- introduction to someone new to the field. one entering catalysis research for the first time or If you are looking for a good textbook on het- as a reference for the experienced researcher. erogeneous catalysis, “Concepts of Modern The text starts with an introduction entitled Catalysis and Kinetics” is well worth considering. ‘What is catalysis’. It then continues with chapters It is certainly a book I would have liked to have on kinetics (mostly the reactions of gases in het- read when I started in catalysis research.

Platinum Metals Rev., 2004, 48, (4), 180–181 180 The Reviewer Tim Watling is a Principal Scientist in the Gas Phase Catalysis Department at the Johnson Matthey Technology Centre, U.K. He is interested in kinetics and computer simulation of vehicle emissions aftertreatment systems.

Platinum Metals Rev., 2004, 48, (4) 181 DOI: 10.1595/147106704X4844 Bicentenary of Four Platinum Group Metals PART II: OSMIUM AND IRIDIUM – EVENTS SURROUNDING THEIR DISCOVERIES

By W. P. Griffith Department of Chemistry, Imperial College, London SW7 2AZ; E-mail: [email protected]

This paper follows an earlier one on the discoveries of rhodium and palladium in 1803 by William Hyde Wollaston (1). In 1804, two more of the platinum metals: iridium and osmium were discovered, also in London. This paper concerns the bicentenary of their discovery by Wollaston’s friend and collaborator, Smithson Tennant.

In Part I, the brilliant work of William Hyde name (Smithson) is not clear – possibly it derived Wollaston on the isolation of rhodium and palladi- from the surname of an earlier family member. His um was described (1). Here, the lesser-known father died when he was ten, and his mother died figure of Smithson Tennant and his isolation of the in a horse-riding accident when he was twenty. (In much more intractable elements iridium and osmi- 1815 Tennant was to lose his life in a rather simi- um is considered. This bicentennial work of 1804, lar accident.) He showed an early interest in reported by Tennant two years after Charles chemistry, making gunpowder for fireworks when Hatchett’s discovery of niobium (2), was an he was nine years old (3). In 1781 he studied med- endeavour in which he was pursued by his French icine at Edinburgh University, attending lectures contemporaries H. V. Collet-Descotils, A. F. de by Joseph Black, and in 1782 he joined Christ’s Fourcroy and L. N. Vauquelin. Tennant was a less College, Cambridge, studying chemistry and flamboyant but no less interesting person than his botany. In this year too he received an inheritance friend Wollaston, and undoubtedly he was as origi- of lands in and near Selby and probably some land nal and creative a chemist, but he was lacking in in Wensleydale from his deceased parents, and drive and was nowhere near as productive. these are likely to have provided him with an Although there is no full-scale biography of income for life (9). Tennant, there is an invaluable memoir by his In 1784, aged 23, he travelled to Denmark and friend, the lawyer John Whishaw, written anony- Sweden, where he met Carl Scheele and the miner- mously in the Annals of Philosophy in 1815 (3). This alogist Johann Gahn, and by 1785 he had taken up was published, with very minor changes, as a book- an unfashionable antiphlogistic view of chemistry let in the same year (4). Subsequent nineteenth (3, 4). In 1786 he travelled to France and Holland; century accounts, by Thomas Thomson in 1830 (5) in France he met Berthollet and may well have met and by Sir John Barrow in 1849 (6), rely heavily on Lavoisier (7). In the same year he went to these, as do more modern accounts (7–10). Emmanuel College, Cambridge, and graduated as In 1854 Henry Gunning (‘Senior Esquire Bedell M.D. in 1796, although he seems never to have for Christ’s College, Cambridge’) reported some practised medicine. He met William Wollaston (1) interesting anecdotes (11), and in 1940 A. E. Wales at Cambridge, and after he moved to London they wrote a thesis (unpublished) with a brief but useful became lifelong friends and collaborators. published summary (7). In 1961, this Journal com- memorated the bicentenary of Tennant’s birth (12). Fellow of the Royal Society On 13th January, 1785, at the extraordinarily Smithson Tennant: Early Years young age of 24, he was elected a Fellow of the Tennant, a clergyman’s son, was born on 30th Royal Society¸ despite not yet having scientific November, 1761, at Finkle Street, Selby, publications. Much later, in November 1804, he Yorkshire. The origin of his unusual Christian was awarded the Royal Society’s Copley medal,

Platinum Metals Rev., 2004, 48, (4), 182–189 182 Smithson Tennant became interested in native platinum while still a student at Cambridge. This is an extract from his diary for October 4th 1784, when has was only twenty two, and describes his visit to Lorenz Crell at Helmstädt. It records the details of Count von Sickingen’s method of rendering platinum malleable mainly for the discovery of osmium and iridium. tion of diamond, by heating with saltpetre in a gold Around 1793 Smithson Tennant took up resi- tube, gave only carbon dioxide – this he measured dence at No. 4, Garden Court in the Temple, quite gravimetrically by the amount of calcium carbon- close to Somerset House the then home of the ate formed from lime water. He found that the Royal Society, and here he remained until his amount formed was the same as that shown earli- death. In December 1800 he entered into a formal er by Lavoisier who had oxidised a similar quantity partnership with Wollaston for the purchase of a of charcoal. On one occasion, he was involved in a large quantity of platinum ore (1, 10) with which he combustion of diamond when the time for his ride was to do his osmium and iridium work. In 1812 came, so he abandoned his experiment (and pre- the great Swedish chemist Berzelius visited him at sumably the burning diamond) and rode away (5). his farm in Somerset, and in May 1813 he became Tennant’s other published work includes the eighth Professor of Chemistry at Cambridge in papers on the composition of carbon dioxide in the so-called ‘1702’ chair. There, in April and May 1791, the formation of calcium phosphate, a 1814 he delivered his one and only course of lec- development of the technique of double distilla- tures, on the history and principles of chemistry, to tion, the nature of boric acid, emery, magnesia, a large and enthusiastic audience which included dolomite and marble. Tennant developed a new Charles Babbage and John Herschel (7). method for making potassium metal, worked on Tennant had given up horse riding after his the corrosion of gold and platinum by fusion with mother’s fatal accident in 1781, but some fifteen nitre, and studied the unsatisfactory effects of years later he was advised to take it up again to magnesian limestone as a fertiliser. improve his health, and thereafter rode daily, despite having a serious accident in 1809. On 22nd Personal Accounts of Tennant February, 1815 he rode over a wooden bridge near Unfortunately there is no portrait of Tennant Boulogne, but the bolt securing the bridge was extant and indeed there seems never to have been weak. It snapped and the bridge collapsed. one. Whishaw (3, 4) noted this and wrote that: Tennant was thrown from his horse, which fell on top of him into the deep ditch beneath, and he ‘Mr. Tennant was tall and slender in person, with a died an hour later from a fractured skull. thin face and light complexion. His appearance, notwithstanding some singularity of manners, and Tennant’s Chemical Work great negligence of dress, was on the whole striking Tennant published very few papers, though on and agreeable. The general cast of his features was a variety of topics. The most striking, apart from expressive, and bore strong marks of intelligence; the topic of this paper, was his demonstration in and several persons have been struck with a general 1797 that diamond and graphite are both resemblance in his countenance to the well-known allotropes of carbon. He showed that the combus- portraits of [John] Locke.’

Platinum Metals Rev., 2004, 48, (4) 183 Although Wishaw’s account is largely a pane- gyric it does include some slightly critical comments, specifically his extreme untidiness:

‘His…….rooms exhibited a strange, disorderly appearance of books, papers and implements of chemistry, piled in heaps and thrown in confusion together’ (3, 4). Henry Gunning mentions that:

‘when at a loss for a piece of linen to filter some of his preparations he never scrupled taking a part of a cambric handkerchief for the purpose, or cutting off a piece of shirt’ (11). Thomson, writing some years after Tennant’s death, refers to his

‘uncommon chemical skills.....the powers of his mind...were of the highest order.’ He then goes on to say that:

‘his farming speculations, as might have been antici- During Wollaston’s researches into the purification of platinum by dissolution of native platinum ore in aqua pated from the indolent and careless habits of Mr. regia, a large amount of insoluble black powder Tennant, were not very successful’ (5). remained as a byproduct of this operation. While Wollaston concentrated on the soluble portion, Tennant The word indolent appears in a number of examined the insoluble residue. In the summer of 1803, Tennant identified two new elements, iridium and accounts of Tennant (3–5, 7, 10), and even in Sir osmium. This was documented in the paper he read to the Joseph Banks’ speech at the Royal Society congrat- Royal Society in 1804 (31) ulating him in 1804 on the award of the Copley medal (an event at which Tennant surprisingly – have had. It seems that Wollaston worked rather but perhaps typically – was not present) he exhort- harder than Tennant on some of their joint plat- ed Tennant to greater efforts in his chemistry (10). inum research, but the latter carried out all the Nevertheless, all attested to his passion for music, osmium and iridium work, possibly with theatre, literature (and civil liberties). He remained, Wollaston’s constant urging. He was fortunate, or like Wollaston, a bachelor throughout his life. well-advised enough (perhaps by Wollaston), to publish his work speedily – because the French Tennant’s Work on Osmium rivals were hotly in pursuit; indeed, he privately and Iridium communicated his results to Sir Joseph Banks, his It was described in Part I (1) how Wollaston and Wollaston’s mutual friend and at that time and Tennant divided the work of isolating the ele- President of the Royal Society, prior to its publica- ments osmium and iridium from crude alluvial tion. His paper was read to the Royal Society on platinum ore. Wollaston worked on the portions June 21st, 1804 (13). soluble in aqua regia while Tennant had the less enviable task of investigating the insoluble Discovery of Osmium residues. However he had considerable quantities Tennant first showed that the black residue of material with which to work – some 100 ounces obtained after heating crude platina in aqua regia Troy of the black powder (10) – a luxuriously large had a density of 10.7, far too great for the earlier quantity which his French rivals certainly could not (14) suggestion that it was plumbago (graphite).

Platinum Metals Rev., 2004, 48, (4) 184 Tennant heated the black powder remaining from Parallel Work on Osmium and the aqua regia treatment of crude alluvial platina Iridium by French Chemists with sodium hydroxide to red heat, cooled the In 1801 Proust had studied the dissolution of melt and dissolved the resulting mass in water. The crude platina in aqua regia and attributed the small yellow solution thus obtained, which probably amount of black residue remaining to ‘nothing else 2– contained cis-[Os(OH)2O4] as well as OsO4, had a but graphite or plumbago’ (14), a claim dismissed very pungent smell. On acidification the solution by Tennant, as already noted. Antoine François de gave a white volatile oxide, undoubtedly osmium Fourcroy (1755–1809), a chemist of profound tetroxide, OsO4, which was distilled off and stud- knowledge and insight (16), was working with ied (he subsequently made it more directly by Nicolas Louis Vauquelin (1763–1829), a very gift- fusing the black powder with nitre, KNO3). ed experimentalist (17), on the problem of this Of this oxide he wrote: black residue. Vauquelin’s interest in this topic may well have been aroused by the examination he ‘it stains the skin of a dark colour which can not be had made of the palladium sent to him for analy- effaced...... (it has) a pungent and penetrating sis by Wollaston (1, 18). smell....from the extrication of a very volatile metal In September and October 1803 Fourcroy and oxide....this smell is one of its most distinguishing Vauquelin read a paper to the Institut Nationale de characters, I should on that account incline to call the France in Paris, published in 1804, in which they metal Osmium’. described their study of this black solid. They The name is derived from the Greek οσµη – fused it with potash, extracted the cooled melt osme, smell. He reduced an aqueous solution of with water (to give a solution which they believed the oxide to black osmium metal by treatment contained chromium but which may also have with copper, silver or zinc (13). contained rhodium – later to be isolated by Sowerby, in his ‘Exotic Mineralogy’ of 1811, Wollaston in 1804 (19)) and treated the residue illustrated some samples collected by Wollaston of with more aqua regia. Addition of ammonium chlo- Iridium Osmiferrum, which we would now call ride to the latter gave, depending on conditions, osmiridium, collected from ‘Peruvian Platina’ (15). red or yellow crystals. They thought that the red crystals contained a compound of a new metal, in Discovery of Iridium addition to compounds of titanium, chromium, As with his osmium work Tennant heated the iron and copper. black powder he obtained from treating crude These crystals could well have been, or could platina with aqua regia in a silver crucible. This was have contained, iridium as (NH4)2[IrCl6], but cru- followed by fusion with caustic soda at red heat. cially they did not name their “new element” (20). The resulting cooled mass was then dissolved in It is interesting to note that the references (18, water, and the black residue remaining was treated 20 and 22) are to Cit. (citoyens) Fourcroy and in “marine acid” (hydrochloric acid). The residue Vauquelin, with no initials: this was common prac- was again fused with caustic soda and extracted tice in French journals in early Revolutionary with HCl, giving dark red crystals, probably of times.

Na2[IrCl6].nH2O. On heating these an unknown On the same day as their first memoir was read element was obtained as a white powder which to the Institut in September 1803, Hippolyte Victor Collet-Descotils (1773–1815), who had ‘appeared of a white colour, and was not capable of been a student of Vauquelin, reported essentially being melted, by any degree of heat I could similar results, and published a more concise paper apply...... I should incline to call this metal in 1803 (21). Like the cautious Fourcroy and Iridium, from the striking variety of colours which it Vauquelin he did not name the new metal which gives, while dissolving in marine acid...... ’ (13). he believed to be present, but said that he would Iridium is named after the Latin iris, a rainbow. assign it a name after further research. In February

Platinum Metals Rev., 2004, 48, (4) 185 and Vauquelin in 1814 attributes the discovery of iridium and osmium to Tennant, suggesting that the black powder also contains titanium, iron, silicon and aluminium (24).

Osmium and Iridium in the Nineteenth Century There are references in the literature (8, 25, 26) to ptene or ptène (from the Greek πτηοζ ptenos, winged) as a name for osmium; indeed, Tennant is said to have proposed this name for it (8, 25), whereas Partington (26) says that Fourcroy and Vauquelin proposed it (20, 21). The author can find no trace of this ungainly name either in Tennant’s paper (13) or in those of the French authors. The symbol proposed by Berzelius was the familiar Os, and for iridium he proposed first I, later changing it to Ir (27). In his penultimate paper, read as the Bakerian Lecture to the Royal Society on 20th November 1828, a month before his death, Wollaston described the preparation of malleable platinum and palladium and also described his method of making pure osmium tetroxide. He fused osmirid- The opening page of the first memoir on the analysis of crude platinum by Fourcroy and Vanquelin (Anales de ium in alkali to red heat, extracted the cooled melt Chimie, 1804, 49, p. 188) (17) with water and treated the filtrate with sulfuric acid, distilling out pure osmium tetroxide (28). 1804 Fourcroy and Vauquelin announced further In 1828 Berzelius studied the compounds of experiments on the black residue (this work is osmium and tried to determine its atomic weight unlikely, in view of the dates, to have been known (29). He then studied iridium similarly (30). to Tennant). They found that fusion with potash and extraction with water lead to a solution which Initial Uses of the Metals had a strong smell affecting the eyes and throat Some industrial uses for the metals were found (une action très-fort sur les yeux et sur le gosier); on distil- in the nineteenth century. The manufacture of two lation the vapour blackened skin and cloth. They rhodium-iridium-silver-steel razors, which were mistakenly thought this to be a volatile oxide of the presented to Michael Faraday, was mentioned in un-named metal they had observed earlier, but it is Part I (1). The use of osmium tetroxide for biolog- clear in retrospect that they had made osmium ical tissue fixation (that is the preservation of tissue tetroxide (22). and its delineation for optical and electron Although it is clear from Tennant’s paper (13) microscopy) dates back to the middle of the nine- that he knew of the early work of Fourcroy and teenth century and continues to this day. Vauquelin (probably at least some of that In 1874 massive amounts of platinum-iridium described in (20)), he would not have known of alloy were used as standard metre lengths but it their later experiments and does not mention the transpired that these contained some iron and work of Collet-Descotils. In 1806 Fourcroy and ruthenium impurities. These problems were over- Vauquelin magnanimously admitted that come and for many years standard metres and Tennant’s work had been superior to theirs (23), standard kilogrammes made of Pt-Ir alloy were

Platinum Metals Rev., 2004, 48, (4) 186 In 1873, the President of France, Louis Adolphe Thiers, together with a number of his ministers, observed the melting of ten kilograms of iridium-platinum for the production of the new standard metre, in Deville’s laboratory in the École Normale. Deville is standing in front of the door looking thoughtful, and the President is holding a protective glass in front of his eyes kept in Paris (31). Platinum-iridium alloys were with the latter two metals Crookes does not also used in 1862 as boiling vessels for the con- record, but he found iridium to be “as hard as steel centration of sulfuric acid. In 1879 Thomas and….unaffected by any mechanical treatment that can rea- Edison experimented with platinum, iridium-plat- sonably be applied to it”. He found it to be resistant inum and pure iridium filaments for incandescent to attack by any chemical except caustic potash at light bulbs, and Carl von Welsbach used osmium red heat, and even in these conditions it had filaments in 1897. greater resistance than platinum (33). The use of In the late nineteenth century work was carried iridium or iridium-platinum crucibles continues to out on the use of iridium and of iridium-platinum this day and constitutes a valuable application for alloys for thermocouple and temperature measure- the metal. ment purposes (31). Fritz Haber initially used osmium just after the turn of the century as a cata- The Densities of the Metals lyst for the production of ammonia from nitrogen For many years it has been known that osmium and hydrogen, but later used a much cheaper iron- and iridium have the highest densities of any iron oxide catalyst; and in 1918 he received the known metals, but which is the heavier of the two Nobel Prize in Chemistry for this work (32). has been a hotly contested issue. Sir William Crookes persuaded Johnson, It is now clear that osmium (density 22.587 ± Matthey to “fashion” crucibles of rhodium, iridi- 0.009 g cm–3) is very slightly denser than iridium um, ruthenium and osmium; if they succeeded (22.562 ± 0.009 g cm–3) (34).

Platinum Metals Rev., 2004, 48, (4) 187 Conclusions tions, as Longbotton Farm. In his birth place, Selby, a These two papers have celebrated the bicente- residential road on the outskirts of the town is named naries of the discovery in London of four of the six Tennant Street in commemoration of him. platinum group metals, by William Hyde Tennant is buried in the public cemetery in Boulogne, Wollaston and Smithson Tennant. All four ele- with a Latin inscription on the headstone. He left no will ments have important industrial and in particular (9). No pictures or sketches of Tennant survive, indeed catalytic uses. (In 2001, rhodium and osmium were it is believed that none was ever made (3, 4). cited in the Nobel Prize awarded to Knowles, Noyori and Sharpless (35)). They possess rich and Bibliographies varied chemistry, are extensively used in scientific The very comprehensive bibliographies by J. L. research, and constitute and provide fertile ground Howe covering the period 1748 to 1950 are indis- for new discoveries and technologies. pensable for the early work (37). The author wrote a survey of the chemistry of iridium and osmium, Appendix: Residences and covering the literature up to 1967 (38) and on the Memorials of Tennant non-organometallic chemistry of osmium (39), Tennant was born in Finkle Street, in the centre of osmium tetroxide (40) and iridium (41). More up- Selby, near the Abbey church where he was baptised. to-date, though less comprehensive, is a book on The building (probably No. 12, now a public house) still the six platinum group metals by Cotton (42). The stands. “Encyclopedia of Inorganic Chemistry” has useful After Cambridge Tennant moved to London and articles on the coordination and organometallic stayed at No. 4, Garden Court, Temple (adjacent to the chemistry of iridium (43) and osmium (44). Middle Temple on its south-west side) where he carried out his osmium and iridium work. Buildings on the site Acknowledgements are still there, renumbered 1 and 2 Garden Court; No. 4 Mel Usselman, University of Western Ontario, is thanked for a preprint of Ref. (10), Jim and Jenny Marshall (University of was demolished in 1884 but the present Nos. 1 and 2 North Texas, Denton), Richard Moody and Dr John Wales probably occupy the same site (36). Tennant may have (York, U.K.) for information on Tennant’s residences, and had rooms there. Andrew Mussell, archivist of the Geological Society. The ground floor was occupied by the collections of the Geological Society, which was formed in 1807 and References moved at least some of its mineralogical collections to 4 1 W. P. Griffith, Platinum Metals Rev., 2003, 47, (4), 175 Garden Court. Tennant was a Vice-President and 2 W. P. Griffith and P. J. T. Morris, Notes Rec. Roy. Soc. London, 2003, 57, 299 Council member of the Geological Society from 1813 to 3 Anon. (probably J. Wishaw), Ann. Phil., 1815, 6, 1, 81 1815 (36). There was a pub close by, the Crown and 4 Anon. (probably J. Wishaw), “Some Account of the Anchor Tavern in Arundel Street near the Strand: sadly Late Smithson Tennant FRS”, C. Baldwin, London, it has been demolished, but was the site of an informal 1815 5 T. Thomson, “History of Chemistry”, Colburn and dining and conversation club for some members of the Bentley, London, 1930, Vol. 2, p. 232 Royal Society called the King of Clubs. This was fre- 6 Sir John Barrow, “Sketches of the Royal Society and quented by Davy, Wollaston and, during his trips to the Royal Society Club”, John Murray, London, 1849, p. 156 London, Dalton and others. It seems highly likely that 7 A. E. Wales, Nature, 1961, 192, 1224; Thesis (Dipl. Tennant, a sociable person who lived close by, also Ed.), University of Leeds, 1940 attended. He purchased seven acres of farmland near 8 K. R. Webb, J. Roy. Inst. Chem., 1961, 85, 432 Epworth, Lincolnshire, in 1799, and in the same year 9 D. McDonald, Notes Rec. Roy. Soc. London, 1962, 17, 77 bought some five hundred acres at Shipham, in 10 M. C. Usselman, ‘Smithson Tennant: the innovative Somerset. The land was principally used for his experi- and eccentric eighth Professor of Chemistry’ in ments on fertilisers rather than for agriculture. He built a “The 1702 Chair of Chemistry at Cambridge: Transformation and Change”, eds. M. D. Archer house on the Shipham land and used this as a summer and C. D. Haley, Cambridge University Press, 2005, residence (7, 10). This still stands, albeit with some addi- p. 113

Platinum Metals Rev., 2004, 48, (4) 188 11 H. Gunning, ‘Reminiscences of the University, 38 W. P. Griffith, “The Chemistry of the Rarer Town and County of Cambridge from the year Platinum Metals (Os, Ru, Ir and Rh)”, Wiley 1780’, George Bell, London 1854, 2, p. 59 Interscience, London, 1968 12 D. McDonald, Platinum Metals Rev., 1961, 5, (4), 146 39 W. P. Griffith and Ch. J. Raub, ‘Osmium’, in the 13 Smithson Tennant, Phil. Trans., 1804, 94, 411; J. Nat. “Gmelin Handbook of Inorganic Chemistry”, ed. Philos., Chem. Arts, 1805, 10, 24; ibid., 1804, 8, 220 K. Swars, Springer-Verlag, Berlin, 1978, Vol. 68, Suppl. Vol. 1 14 D. L. Proust, Ann. Chim., 1801, 38, 1436, 160 40 W. P. Griffith, Platinum Metals Rev., 1974, 18, (3), 94 15 J. Sowerby, “Exotic Mineralogy or, Coloured 41 W. P. Griffith and Ch. J. Raub, ‘Iridium’, in the Figures of Foreign Minerals, as a Supplement to “Gmelin Handbook of Inorganic Chemistry”, ed. British Mineralogy”, Benjamin Meredith, London, K. Swars, Springer-Verlag, Berlin, 1978, Vol. 67, 1811, p. 75 and facing p. 75 Suppl. Vol. 2 16 W. A. Smeaton, “Fourcroy, Chemist and 42 S. A. Cotton, “Chemistry of the Precious Metals”, Revolutionary”, Heffer, Cambridge, 1962 Blackie Academic, London, 1997 17 W. A. Smeaton, Platinum Metals Rev., 1963, 7, (3), 106 43 M. Schröder, in “Encyclopedia of Inorganic 18 Cit. Vauquelin, Ann. Chim., 1803, 46, 333 Chemistry”, ed. R. B. King, Wiley, London, 1994, 19 W. H. Wollaston, Phil. Trans., 1804, 94, 419; J. Nat. Vol. 5, p. 2328; P. A. Shapley, ibid., p. 2846 Philos., 1805, 10, 3 44 C. E. Housecroft, in “Encyclopedia of Inorganic 20 Cit. Fourcroy et Vauquelin, Ann. Chim., 1803, 48, Chemistry”, ed. R. B. King, 1994, Vol. 3, p. 1606; 177; 1804, 49, 188, 219, summarised in Phil. Mag., J. S. Merola, ibid., 1994, Vol. 6, p. 1620 1804, 19, 117 21 H. V. Collet-Descotils, Ann. Chim., 1803, 48, 153; J. Nat. Philos., Chem. Arts, 1804, 8, 118 22 Cit. Fourcroy et Vauquelin, Ann. Chim., 1804, 50, 5 23 A. F. Fourcroy and N. L. Vauquelin, Ann. du Mus. Hist. Naturelle, 1806, 7, 401; Vauquelin, ibid., 1806, 8, 248 24 M. Vauquelin, Ann. Chim., 1814, 89, 150, 225 25 J. N. Friend, “Man and the Chemical Elements”, Griffin, London, 1951, p. 303 26 J. R. Partington, “A History of Chemistry”, Macmillan, London, 1962, Vol. 3, p. 105 27 J. J. Berzelius, Pogg. Annalen, 1834, 32, 232 28 W. Wollaston, Phil. Trans. Roy. Soc., 1829, 119, 1 29 J. J. Berzelius, Pogg. Annalen, 1828, 13, 527 30 J. J. Berzelius, Pogg. Annalen, 1828, 13, 435, 463 The Author 31 D. McDonald and L. B. Hunt, “A History of Bill Griffith is Professor of Inorganic Chemistry at Imperial College, London. He has considerable experience with the platinum group Platinum and its Allied Metals”, Johnson Matthey, metals, particularly ruthenium and osmium. He has published over London, 1982 260 research papers, many describing complexes of these metals 32 F. Haber, Z. Elektrochem., 1910, 16, 244; P. as catalysts for specific organic oxidations. He has written seven Charlesworth, Platinum Metals Rev., 1981, 25, (3), 106 books on the platinum metals, and is the Secretary of the Historical Group of the Royal Society of Chemistry. 33 W. Crookes, Proc. Roy. Soc., 1908, 80A, 535; J. C. Chaston, Platinum Metals Rev., 1969, 13, (2), 68 34 J. W. Arblaster, Platinum Metals Rev., 1995, 39, (4), 164; ibid., 1989, 33, (1), 14 35 T. A. Colacot, Platinum Metals Rev., 2002, 46, (2), 82; http://www.nobel.se/chemistry/laureates/2001/in dex.html 36 H. B. Woodward, “The History of the Geological Society of London”, Geological Soc., London 1907 37 J. L. Howe and H. C. Holtz, “Bibliography of the Metals of the Platinum Group, 1748–1917”, U.S. Geol. Survey Bull. 694, Government Printing Office, Washington 1919; J. L. Howe and staff of Baker & Co., “Bibliography of the Platinum Metals 1918–1930”, Baker Inc., Newark NJ, 1947; ibid. for 1931–1940 (publ. 1949); ibid. for 1941–1950 (publ. 1956). For further details see G. B. Kauffman, Platinum Metals Rev., 1972, 16, (4), 140

Platinum Metals Rev., 2004, 48, (4) 189 DOI: 10.1595/147106704X13097 ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES N-Benzoylimido Complexes of Palladium. Effect of Hydrogen-Sulfide on the Hydrogen Synthesis, Structural Characterisation and Permeance of Palladium–Copper Alloys at Structure–Reactivity Relationship Elevated Temperatures G. BESENYEI, L. PÁRKÁNYI, G. SZALONTAI, S. HOLLY, I. PÁPAI, G. KERESZTURY and A. NAGY, Dalton Trans., 2004, (13), B. D. MORREALE, M. V. CIOCCO, B. H. HOWARD, R. P. KILLMEYER, 2041–2050 A. V. CUGINI and R. M. ENICK, J. Membrane Sci., 2004, 241, (2), Benzoyl azides, ArC(O)N3 (Ar = phenyl or substi- 219–224 tuted phenyl), react with [Pd2Cl2(dppm)2] (1) (dppm = The H permeance of Pd-Cu foils (1) (0.1 mm thick) bis(diphenylphosphino)methane) to give novel ben- was evaluated using transient flux measurements over zoylnitrene complexes, [Pd2Cl2(µ-NC(O)Ar)(dppm)2]. 603–1123 K and pressures ≤ 620 kPa, in the presence The C2P4Pd2 rings are chiral. Crystallographic and and absence of 1000 ppm H2S. S resistance (no sig- solution IR studies of the reaction of a series of para- nificant change in permeance) was correlated with the substituted benzoyl azides with (1) showed that the temperatures associated with f.c.c. (1). The H perme- reaction obeys the Hammett equation. ance of b.c.c. (1) was up to two orders of magnitude lower on exposure to H2S. A smooth transition from S poisoning to S resistance with increasing tempera- Iridium(III) and Rhodium(III) Cyclometalated ture was correlated with the b.c.c. to f.c.c. transition. Complexes Containing Sulfur and Selenium Donor Ligands Magnetism of CaRuO3 Crystal M.-K. LAU, K.-M. CHEUNG, Q.-F. ZHANG, Y. SONG, W.-T. WONG, A. KORIYAMA, M. ISHIZAKI, T. C. OZAWA, T. TANIGUCHI, Y. I. D. WILLIAMS and W.-H. LEUNG, J. Organomet. Chem., 2004, NAGATA, H. SAMATA, Y. KOBAYASHI and Y. NORO, J. Alloys 689, (14), 2401–2410 Compd., 2004, 372, (1–2), 58–64 Reaction of [M(Buppy)2Cl]2 (M = Ir (1), Rh (2); The magnetic properties of polycrystalline (1) and BuppyH = 2-(4'-tert-butylphenyl)pyridine) with single-crystal (2) samples of CaRuO3 were studied. Na(Et2NCS2), K[S2P(OMe)2] and K[N(Ph2PS)2]2 gave ∧ ∧ The M(T) curves of (1) showed irreversible behaviour monomeric [M(Buppy)2S S] (S S = Et2NCS2, and the M(H) curve showed weak ferromagnetic S2P(OMe)2, N(PPh2S)2). Treatment of (1) with behaviour at < 60 K. The M(H) curve of (2) exhibit- Na[N(PPh2Se)2] gave [Ir(Buppy)2{N(PPh2Se)2}]. ed peculiar behaviour at 1.7 and 5 K, showing Reaction of (1) and (2) with AgOTf followed by treat- evidence of magnetic order at very low temperature. ment with KSCN gave [{M(Buppy)2}2(µ-SCN)2].

CHEMICAL COMPOUNDS Mixed Iridium(III) and Ruthenium(II) Polypyridyl Complexes Containing Poly(ε-caprolactone)- Insertion of Phenylacetylene into bipyridine Macroligands [Pt(GeMe3)(SnMe3)(PMe2Ph)2] V. MARIN, E. HOLDER, R. HOOGENBOOM and U. S. SCHUBERT, T. SAGAWA, R. TANAKA and F. OZAWA, Bull. Chem. Soc. Jpn., J. Polym. Sci. A: Polym. Chem., 2004, 42, (17), 4153–4160 2004, 77, (7), 1287–1295 Coordination of a poly(ε-caprolactone)-bipyridine The reaction of Me3GeSnMe3 with a Pt(0) complex, macroligand to Ir(III) and Ru(II) precursor complex- in situ generated from [Pt(cod)2] and PhMe2Ph, gave a es yielded the title complexes. Both photophysical cis-trans mixture of [Pt(GeMe3)(SnMe3)(PMe2Ph)2] (1). and electrochemical properties of the metal-contain- Recrystallisation of crude (1) from CH2Cl2-pentane ing polymers confirmed the formation of the gave cis-(1). (1) underwent competitive insertion of tris-Ir(III) and tris-Ru(II) polypyridyl species. phenylacetylene into the Pt-Sn and Pt-Ge bonds.

The Crystal Structure of [Pt(NH3)4][PtI4]: ELECTROCHEMISTRY Comparison with Magnus’ Green Salt The Electrochemistry of Gold–Platinum Alloys J. S. CASAS, Y. PARAJÓ, Y. ROMERO, A. SÁNCHEZ-GONZÁLEZ, H. MÖLLER and P. C. PISTORIUS, J. Electroanal. Chem., 2004, J. SORDO and E. M. VÁZQUEZ-LÓPEZ, Z. Anorg. Allg. Chem., 570, (2), 243–255 2004, 630, (7), 980–982 Au-Pt electrodes are more active for ethylene glycol The structure of [Pt(NH3)4][PtI4] (1) was found to electrooxidation than either Pt or Au electrodes. The be isotypic with Magnus’ green salt and is unchanged Au-Pt electrodes in the solid solution condition are at low temperature except for a slight contraction of more active than two-phase electrodes. More severe 2+ 2– the unit cell. (1) consisted of [Pt(NH3)4] and [PtI4] ; poisoning occurs during the first few cycles at the Au- the Pt atoms are surrounded by 4 N or 4 I atoms in Pt electrodes than at both the Pt or Au electrodes. square-planar arrangements. At 173 K the intermole- Longer potential pulsing cleaning cycles are needed to cular stacking interaction Pt-Pt was shortened. remove the poisons at the Au-Pt electrodes.

Platinum Metals Rev., 2004, 48, (4), 190–192 190 PHOTOCONVERSION HETEROGENEOUS CATALYSIS Micelle-Mediated UV-Photoactivation Route for Hydroisomerization of n-Heptane and n- the Evolution of Pdcore–Aushell and Pdcore–Agshell Tetradecane over Pt/SAPO-11 Bimetallics from Photogenerated Pd Nanoparticles F. ZHANG, C.-H. GENG, Z.-X. GAO and J.-L. ZHOU, J. Fuel Chem. M. MANDAL, S. KUNDU, S. K. GHOSH and T. PAL, J. Photochem. Technol. (Chin.), 2004, 32, (3), 340–345 Photobiol. A: Chem., 2004, 167, (1), 17–22 Hydroisomerisation of n-heptane and n-tetradecane UV-photoactivation of aqueous PdCl2 gave Pd over Pt/SAPO-11 was carried out in a fixed-bed, down-flow reactor at 200ºC ~ 420ºC, 0.5 MPa and nanoparticles (1) with narrow size distribution (~ 5 –1 nm) in poly(oxyethylene)isooctyl phenyl ether WHSV of 2.0 h . High n-alkane conversion with micelles, TX-100, as reducing agent. The TX-100 also 90% selectivity to isomers was achieved. Paraffin iso- acted as a stabiliser. The bimetallic colloids (10–30 merisation may occur inside the SAP0-11 channels. nm) with varying metal ratios were prepared by suc- cessive ion loading using a seed-mediated method Pd-Catalyzed Heck Arylation of where (1) act as seeds. Cycloalkenes–Studies on Selectivity Comparing Homogeneous and Heterogeneous Catalysts Electronic and Photophysical Properties of a L. DJAKOVITCH, M. WAGNER, C. G. HARTUNG, M. BELLER and Novel Phenol Bound Dinuclear Ruthenium K. KOEHLER, J. Mol. Catal. A: Chem., 2004, 219, (1), 121–130 Complex: Evidence for a Luminescent Mixed Heck reactions of aryl bromides with cyclohexene Valence State and cyclopentene were catalysed by: Pd/C, Pd/SiO2, Pd/MgO, Pd/Al2O3, Pd(0)/Z, Pd(II)/Z and T. E. KEYES, B. EVRARD, J. G. VOS, C. BRADY, J. J. McGARVEY 2+ [Pd(NH3)4] /Z (Z = NaY, HY or ZSM-5 zeolites); and P. JAYAWEERA, Dalton Trans., 2004, (15), 2341–2346 A dinuclear Ru(II) complex (1), bridged by 3-(2- and Pd(OAc)2/PPh3, Pd2(dba)3·dba/PCy3 and the phenol)-5-(pyridin-2-yl)-1,2-4-triazole, was prepared {Pd[P(o-C6H4CH3)2-(o-C6H4CH2)(CH3CO2)]}2 “pal- electrochemically. A weak intervalence charge trans- ladacycle”. Dissolved molecular Pd species are fer transition was observed. Upon oxidation of the involved in the Heck coupling for all of the catalysts. O,N moiety luminescence from (1) is reversibly The dehalogenation mechanism involves the surface switched on at 0.3 V and reversibly switched off by of solid Pd metal particles and radical processes. the application of 1.3 or 0 V. Drastic Increase of Selectivity for H2O2 Formation ELECTRODEPOSITION AND SURFACE in Direct Oxidation of H2 to H2O2 over Supported Pd Catalysts Due to Their Bromination COATINGS V. R. CHOUDHARY, C. SAMANTA and A. G. GAIKWAD, Chem. Microstructure and Mechanical Properties of Commun., 2004, (18), 2054–2055 Ir–Ta Coatings on Nickel-Base Single-Crystal Pd catalysts have high activity for H2O2 decompo- Superalloy TMS-75 sition which limits their use for formation of H2O2 from H2. The incorporation of bromide anions (1.0 P. KUPPUSAMI, H. MURAKAMI and T. OHMURA, J. Vac. Sci. β Technol. A, 2004, 22, (4), 1208–1217 wt.%) into Pd supported on Al2O3, ZrO2, SiO2, H- Ir-Ta coatings (1) with 16.2, 23.9, 40.7 and 65.1 zeolite or Ga2O3 overcomes this. These catalysts were at.% Ta were deposited at 573 K on the Ni-base sin- used for the direct oxidation of H2 to H2O2 by O2 (at gle crystal superalloy, TMS-75, by DC magnetron room temperature) in 0.03 M H3PO4. A large increase sputtering by selecting the ratio of the surface areas in selectivity for H2O2 formation was accompanied of the Ir and Ta targets. (1) had a nanocrystalline by a large decrease in the H2O2 decomposition activ- structure where crystallite size and rms roughness ity. The bromide anions change the electronic decreased with increase in Ta content. Young’s mod- properties of the Pd. ulus and hardness of the coatings generally decreased with the increase in Ta content. However, the hard- Rietveld Refinement and Activity of CO Oxidation ness peaked in the 16.2–23.9 at.% Ta range, possibly over Pd/Ce0.8Zr0.2O2 Catalyst Prepared via a due to Ir3Ta formation. Surfactant-Assisted Route J. A. WANG, L. F. CHEN, M. A. VALENZUELA, A. MONTOYA, J. Cathodic Electrodeposition of RuO2 Thin Films SALMONES and P. DEL ANGEL, Appl. Surf. Sci., 2004, 230, from Ru(III)Cl3 Solution (1–4), 34–43 B.-O. PARK, C. D. LOKHANDE, H.-S. PARK, K.-D. JUNG and Ce0.8Zr0.2O2 nanophases (1) were synthesised using O.-S. JOO, Mater. Chem. Phys., 2004, 87, (1), 59–66 a surfactant-assisted method. Structural refinement RuO2 films (1) of different thicknesses were by the Rietveld method confirmed that many cation- cathodically deposited on Ti substrates under gal- ic lattice defects were formed in the crystals of (1). vanostatic conditions from aqueous acidic Ru(III)Cl3 Pd/Ce0.8Zr0.2O2 calcined at 873–1173 K exhibited a solution. XRD and TEM established that (1) are more stable catalytic activity for CO oxidation, and nanocrystalline. SEM showed that (1) are porous and also performed a lower light-off temperature at cool that surface morphology changes with film thickness. start < 373 K, in comparison with Pd/CeO2.

Platinum Metals Rev., 2004, 48, (4) 191 Drastic Enhancement of SCR of NO over Ir Microwave Promoted Heck Reactions Using an Catalyst through Formation of Metallic Iridium on Oligo(ethylene glycol)-Bound SCS Palladacycle Na-Zeolite under Thermomorphic Conditions J. SHIBATA, H. YOSHIDA, A. SATSUMA and T. HATTORI, Chem. D. E. BERGBREITER and S. FURYK, Green Chem., 2004, 6, (6), Lett., 2004, 33, (7), 800–801 280–285 Ir/Na-zeolite catalysts (1) have excellent activity at Pd catalysed Heck couplings using an air-stable, 500 K for the SCR of NO in a He atmosphere also H2O-soluble oligo(ethylene glycol)-bound SCS pal- containing CO/H2. Low loaded (1) (0.5 wt.% Ir) ladacycle catalyst (1) and microwave irradiation gave could be used. Ir LIII-edge XANES and CO2-H2 titra- cinnamic acid derivatives in < 1 h. Recycling of (1) tion were carried out. The Ir forms a highly active was achieved using a 10% aqueous dimethylac- metallic species with low oxidation; this Ir species is etamide-heptane thermomorphic system that was highly dispersed. Ir/Na-MOR mordenite zeolite has biphasic during the catalyst recovery step. the highest activity.

The RuO4-Catalysed Dihydroxylation, Local Barrier Height of Ir/TiO2 Model Catalysts Ketohydroxylation and Mono Oxidation–Novel Y. MAEDA, T. AKITA, M. OKUMURA and M. KOHYAMA, Jpn. J. Appl. Phys., 2004, 43, (7B), 4595–4598 Oxidation Reactions for the Synthesis of Diols α Ir was deposited on TiO2 (110)-(1×2) surfaces by and -Hydroxy Ketones vacuum evaporation to form Ir/TiO2 model catalysts B. PLIETKER and M. NIGGEMANN, Org. Biomol. Chem., 2004, (1). The local barrier height (LBH) of (1) was mea- 2, (17), 2403–2407 sured using scanning tunnelling microscopy and A study of RuO4-catalysed oxidations of alkenes compared with that of Au/TiO2 catalyst. The Ir was resulted in the development of the first RuO4-catal- oxidised to IrO2 by annealing at 1073 K. The LBH of ysed ketohydroxylation of olefins. Mechanistic IrO2 particles was almost the same as that of the TiO2 studies of both dihydroxylation and ketohydroxyla- support, while the LBH of Au particles was 0.3 eV tion gave rise to the first regioselective catalytic larger. The charge transfer between IrO2 and TiO2 is monooxidation of vic-diols. When applied in a two- small. Electrons are transferred from TiO2 to Au. step sequence of asymmetric dihydroxylation and regioselective monooxidation, enantiopure α- hydroxy ketones were obtained. HOMOGENEOUS CATALYSIS Synthetic Applications of Oxime-Derived FUEL CELLS Palladacycles as Versatile Catalysts in Cross- CO Tolerance of Commercial Pt and PtRu Gas Coupling Reactions D. A. ALONSO, L. BOTELLA, C. NÁJERA and M. C. PACHECO, Diffusion Electrodes in Polymer Electrolyte Fuel Synthesis, 2004, (10), 1713–1718 Cells Palladacycles derived from 4,4'-dichlorobenzophe- F. HAJBOLOURI, B. ANDREAUS, G. G. SCHERER and A. WOKAUN, none and 4-hydroxyacetophenone oximes are Fuel Cells, 2004, 4, (3), 160–168 efficient and versatile pre-catalysts for C-C bond cou- The CO tolerance of Pt and PtRu anodes from E- pling reactions. These coupling reactions include Tek and Tanaka were examined in PEFCs using AC Mizoroki-Heck, Suzuki-Miyaura, Stille, Ullmann- impedance spectroscopy along steady-state current- type, Sonogashira, sila-Sonogashira, Glaser and voltage curves. The Tanaka PtRu (40:60) anode is acylation of alkynes under very low loading condi- reported to have better CO tolerance under the tions. The high yielding reactions can be carried out selected operating conditions. The impedance spectra in air using either organic or aqueous solvents. of the Tanaka PtRu anode did not show any induc- tive behaviour and its CO surface coverage was low. Dioxygen-Promoted Regioselective Oxidative Heck Arylations of Electron-Rich Olefins with Synthesis and Characterization of Methanol Arylboronic Acids Tolerant Pt/TiOx/C Nanocomposites for Oxygen M. M. S. ANDAPPAN, P. NILSSON, H. VON SCHENCK and M. Reduction in Direct Methanol Fuel Cells LARHED, J. Org. Chem., 2004, 69, (16), 5212–5218 L. XIONG and A. MANTHIRAM, Electrochim. Acta, 2004, 49, Heck arylations of electron-rich heteroatom-substi- (24), 4163–4170 tuted olefins with arylboronic acids to give acyclic The title nanocomposites (1) were prepared by: enamides were carried out using Pd(OAc)2 with 2,9- depositing hydrated TiO2 on Pt/C; reducing H2PtCl6 dimethyl-1,10-phenanthroline (dmphen) as the with Na formate on C-supported hydrated TiO2 catalyst system. The reactions were carried out under (TiO2/C); and simultaneously depositing hydrated O2. The dmphen ligand controls the internal regiose- TiO2 and reducing H2PtCl6 with Na formate on C lectivity and mediates a reoxidation of Pd(0) with O2, support. (1) underwent heat treatment at 500 and thus allowing a low catalyst loading. Controlled 900ºC in 90% Ar/10% H2. Some of (1) had higher microwave heating and increased O pressure were catalytic activity than Pt/C. (1) also exhibited better used to reduce the reaction time to 1 h. MeOH tolerance than Pt/C.

Platinum Metals Rev., 2004, 48, (4) 192 DOI: 10.1595/147106704X13088 NEW PATENTS PHOTOCONVERSION Potentiometric Sensors for NOx Sensing OHIO STATE UNIV. U.S. Patent 6,764,591 Photosensitive Dispersion with Adjustable Viscosity Total NOx concentration can be determined in SEMIKA SA World Appl. 2004/061,157 harsh environments without CO interference using a A photosensitive dispersion (1) has adjustable vis- gas conduit with a catalytic filter of Pt and zeolite, cosity for metal deposition on an insulating substrate. maintained at < 700ºC. The gas interacts with the fil- (1) combines: a pigment providing oxidation-reduc- ter and forms an equilibrium mixture of NO and NO2 tion properties under light irradiation; a Pt, Pd, Ru, from NOx. The measuring system also contains an Rh, Cu, Ni, Co, Ag, etc., metallic salts (2), such as Pd electrolyte substrate on which are a sensing potentio- chloride; a complex-forming agent for (2), such as metric electrode, to contact the NO/NO2 equilibrium carboxylic acid; a liquid film-forming polymer, such as mixture, and a reference potentiometric electrode. alkyl, acrylic, etc.; KOH; and an organic solvent. Light-Emitting Device ELECTRODEPOSITION AND SURFACE SANYO ELECTRIC CO LTD Japanese Appl. 2004-119,996 COATINGS A light-emitting device (1) includes a transparent Plating of Multilayer Insulator/Conductor Structures substrate, a semiconductor layer, a p-side electrode (2), and an n-side electrode. The semiconductor layer UNIV. COLLEGE CORK World Appl. 2004/057,055 A photoresist insulator and a Pd chloride catalyst is formed on the transparent substrate and includes are provided in a bath for electrophoretic deposition an n-type GaN laminated contact layer, and an onto a substrate. The layer formed is heated by UV InGaN light-emitting layer and a p-type GaN contact and then plasma etched to expose more of the Pd layer. (2) includes a contact Pd electrode and a reflect- chloride, which acts as a catalyst for electroless plating Al electrode. (1) can achieve uniform light ing of the conductive seed layer. A thicker conductive emission intensity over the entire device. layer is then electroplated onto the seed layer. HETEROGENEOUS CATALYSIS CVD Platinum Metal Deposition Preferential Oxidation of Carbon Monoxide (PROX) MICRON TECHNOL. INC U.S. Patent 6,750,110 A non-reactive gas of He, Ar and N (1), is bubbled DELPHI TECHNOL. INC European Appl. 1,426,330 over an organic Pt-based metal precursor, such as A catalyst for preferentially oxidising CO in a H2 methylcyclopentadienyltrimethyl Pt, until (1) is satu- stream contains a hexaaluminate (1), an alkaline metal rated. CVD of the Pt-based metal film (1) onto a hydroxide, and Ir, Ru and/or Pt. (1) allows inclusion of the metal hydroxides that flux the active Pt group substrate then occurs in O2 and N2O at 200–600ºC under 10–50 torr. The film is consistently smooth and metal (pgm) surface at higher temperatures than can has good step coverage. be obtained with Al oxide-based catalysts (2). This enhances resistance of the catalyst and monolithic support and increases the durability and thermal APPARATUS AND TECHNIQUE range of the PROX catalyst. Smaller amounts of pgm Electrodes for High-Performance Spark Plugs oxides are needed to achieve similar activity to (2). FRANCESCONI TECHNOL. GmbH World Appl. 2004/054,055 Extremely Low Acidity Ultrastable Y Zeolite Catalyst Electrodes for high-performance spark plugs, espe- CHEVRON U.S.A. INC World Appl. 2004/044,100 cially for stationary ICEs, are produced from Pt group A hydrocracking catalyst (1) used for converting metal alloy, containing Ir, with one other metal being hydrocarbonaceous oils has a very low acidity, highly rhodium. The metal layers, containing 2.2–2.8 mass% dealuminated ultrastable Y zeolite having an α value Rh, are fused across the whole surface, by laser or of ≤ 5 and Brönsted acidity of ~ 1–20 µmol g–1.. The electron radiation at 400–1500°C, to form a planar hydrogenation component of (1) is a metal or mix- weld or soldered bond. A compact fused alloy body. tures thereof selected from Group VI (Mo and/or W) is formed via a strip shape. and Group VIII (Ni, Co, Pt and Pd).

Flow-Sensing Device and Method for Fabrication Reforming Catalyst FORD GLOBAL TECHNOL. LLC U.S. Patent 6,763,712 JOHNSON MATTHEY PLC World Appl. 2004/047,985 A gas flow sensor for use in ICE contains sensing A reforming catalyst (1) comprising 0.5–1 wt.% of elements of Ru oxide in a glassy matrix containing Pb, Rh or Ru particles on a support material of CeO2 and Si and/or Bi. The sensor also contains a reference ZrO2 dispersed on the surface of SnO2-Al2O3. The resistor at ambient temperature and a heated flow- loading of CeO2 and ZrO2 is 10–60 wt.% based on sensing resistor (1), both on an insulating substrate. the weight of the support material. (1) has excellent S An electrical circuit feeds a current into (1) to keep tolerance. Catalysed components, fuel processing sys- them at the same temperature. tems and reforming processes using (1) are disclosed.

Platinum Metals Rev., 2004, 48, (4), 193–194 193 Production of High Octane Gasoline Fuel Cell for Portable Radio-Electronic Equipment COUNCIL SCI. IND. RES. World Appl. 2004/058,400 TARASEVICH, M. R. et al. World Appl. 2004/077,596 High-octane gasoline is produced from straight run Alcohol-air fuel cells (1) comprise a housing with a light naphtha on 0.1–2.0 wt.% Pt/HZSM-5 molecu- liquid catalytically active anode catalyst (such as lar sieve catalyst (1), prepared by impregnating Ni/Ru nanoparticles on high surface area C) and an tetramine Pt chloride on the HZSM-5 zeolite. This is air catalytically active hydrophobic gas-diffusion cath- then dried for 10–12 h at 110ºC and calcined at ode (of Ru, Ni, Co or Fe) tolerant to alcohol. A liquid 400–600ºC. The Pt impregnated zeolite is loaded in a alcohol-alkaline mixture fills the interior cavity of the high pressure reactor and reduced for 2–5 h by H2. (1) housing and separates the anode and cathode. The is prepared without any prior steaming and acid leach- hydrophobic surface of the cathode faces air, while ing, so no hazardous mineral acids are involved. the surface facing the alcohol-alkaline mixture is coated with a layer of polybenzimidazole. (1) are designed Catalytic Dehydrogenation for use in portable radio-electronic equipment, such HALDOR TOPSOE A/S U.S. Appl. 2004/0,110,630 as cellular phones, etc. Catalytic dehydrogenation of a hydrocarbon process stream (1) to the corresponding olefin(s) is Electrocatalytic Cathode Device of Palladium performed by contacting the stream with a meso- U.S. NAVY U.S. Patent 6,740,220 porous zeotype catalyst that is intra-crystalline and An electrocatalytic cathode for use in an electro- non-crystallographic with mesopore volume of the chemical cell system, such as a fuel cell, is produced crystals > 0.25 ml g–1. The catalyst comprises Rh, Pd, from high density or porous C substrate. Pd and Ir Pt, Cr, Mo, Sn, etc., and at least one element is Pt. (1) are simultaneously deposited onto the C by cyclic contains a mono-cyclic aromatic compound, such as voltammetry, etc. The simultaneous deposition of the ethyl benzene or para-ethyl methyl benzene. Pd and Ir is preferably carried out using a solution of 1.0 mM Pd chloride, 2.0 mM Na hexachloroiridate, 0.2 M KCl, and 0.1 M HCl. HOMOGENEOUS CATALYSIS Preparation of Polyamide by Carbonylation RHODIA POLYAMIDE INTERMED. CHEMICAL TECHNOLOGY World Appl. 2004/048,441 Recovery of Platinum Metals from Spent Catalysts Polyamide (in particular the type obtained by con- INST. NEORG. KHIM. SO RAN Russian Patent 2,221,060 densation polymerisation from lactams and/or amino Pt and Pd are recovered from spent porous base acids) is prepared by carbonylation in the presence of catalysts by leaching with oxidising acidic solutions, a Pd based catalyst, such as Pd diacetate or Pd triph- such as HCl-HNO3, to transfer them into a H2O-sol- enylphosphine. An organic compound with an amine uble state. The Pt and Pd complex ions are than function, such as 4-pentene amine, is reacted with CO reduced to the lowest oxidation state with Na oxalate in the presence of the catalyst. or FeSO4, and separated from the residue. High Pt and Pd contents are obtained in solution. Producing L-Phenylephrine IWAKI CO LTD Japanese Appl. 2004-115,437 ELECTRIC AND ELECTRONIC Optically active L-phenylephrine (1) is produced with ease by subjecting an acid salt of 1-(3-oxyphenyl)-2- ENGINEERING (N-methyl)-ethan-1-one to catalytic asymmetric Magnetic Recording Media with Adjustable Coercivity reduction in the presence of a secondary or tertiary MAXTOR CORP U.S. Patent 6,753,100 amine in an organometallic complex catalyst system A magnetic recording medium (1) comprises a sub- (1). (1) is, for example, Rh-1,5-cyclooctadiene chlo- strate upon which is an underlayer that carries at least ride and contains an optically active two magnetic layers. Each magnetic layer is a Co pyrrolidinebisphosphine ligand. One reduction took alloy, such as Co-20Cr-10Pt-8B, of different compo- place at 60ºC for 30 h and gave 85% (1) with 98% ee. sition, intrinsic magnetic properties and thickness (2–50 nm). The coercivity of (1), which may be a magnetic disk, can be modified without changing sub- FUEL CELLS strate temperature, underlayer thickness or substrate Metal-Coated Carbon Surfaces for Fuel Cells biasing during manufacture. NORTHERN ILLINOIS UNIV. World Appl. 2004/061,163 A C article (1) is coated with a metal selected from Manufacture of Ferroelectric Capacitor the group of Pt, Pd, Ru, Rh, Ir, Au and Ag by cyclic ROHM CO LTD U.S. Patent 6,794,243 voltammetric electrodeposition. (1) can be C paper, C A ferroelectric capacitor (1) is claimed which main- rod and/or C electrodes, such as a fuel cell electrode. tains high ferroelectricity. It comprises a Si oxide A Pt-coated C electrode is produced by the elec- layer, a lower electrode (Ir-Pt alloy), a ferroelectric trodeposition of < 0.1 mg cm–2 of Pt on the exterior layer, and an upper electrode, all formed upon a Si surface of (1) by varying the electrical potential from substrate. The structure prevents oxygen vacancies in ~ 0 to –1.0 V at a rate of ~1000 mV s–1. the ferroelectric layer.

Platinum Metals Rev., 2004, 48, (4) 194 NAME INDEX TO VOLUME 48

Page Page Page Page Agnew, G. 37 Besson, M. 142 Chantson, J. T. 140 De Fourcroy, A. F. 182 Agostinelli, E. 83 Beyer, A. 39 Che, C.-M. 157 de Jong, K. P. 154 Aika, K. 81 Biallozor, S. 40 Cheary, R. W. 39 de Oliveira, O. N. 140 Ajiki, K. 82 Binder, M. 36 Chen, I.-C. 12 De Wael, K. 38 Akita, T. 192 Black, J. 182 Chen, J. H. 39 Debono, N. 142 Albertini, V. R. 83 Bochegov, A. 47 Chen, L. F. 191 Del Angel, P. 191 Alonso, D. A. 192 Bock, C. 82 Chen, P. 82 del Rio, I. 149 Aluha, J. 171 Bondarenko, V. A. 79 Chen, Y. 83 Della Negra, S. 176 Amieiro-Fonseca, A. 154 Bönnemann, H. 38 Chen, Y.-L. 12 Deluga, G. A. 81 Amiridis, M. D. 170 Borglum, B. 37 Cheprakov, A. V. 102 Deng, L. 142 Anandan, S. 141 Bosco, J. W. J. 141 Cheung, K.-M. 190 Deprun, C. 176 Andappan, M. M. S. 192 Botella, L. 192 Chi, Y. 12 Deronzier, A. 102 Andreaus, B. 192 Bowles, J. F. W. 139 Chiang, C. L. 39 Désilets, S. 40 Antonucci, P. L. 83 Bozzolo, G. 38 Chizek, P. D. 60 Deutsch, D. S. 170 Antonucci, V. 83 Brady, C. 191 Choplin, A. 102 Deville, H. S.-C. 187 Arakawa, H. 81 Brandon, N. 37 Chorkendorff, I. 180 Dey, S. 16 Araki, K. 80 Brasil, M. J. S. P. 140 Chou, P.-T. 12 Dhanalakshmi, K. 82 Arblaster, J. W. 173 Breit, B. 82 Choudhary, V. R. 191 Di Blasi, A. 83 Aricò, A. S. 83 Brennan, P. E. 15 Choudhury, N. A. 83 Diallo, O. 142 Artamkina, G. A. 39 Brewer, K. J. 80 Chu, J. P. 39 Dietzel, A. 15 Ashton, S. V. 2, 46, 65, Bricout, H. 38 Chu, N. C. 142 Dilworth, J. R. 157 90, 132 Bridgeman, A. J. 80 Chung, Y.-M. 140 DiMichele, L. 40 Aston, F. W. 173 Bridle, A. 139 Churilov, G. N. 81 Djakovitch, L. 142, 191 Aymard, L. 39 Brijoux, W. 38 Ciocco, M. V. 190 Dodelet, J. P. 40 Brill, J. W. 79 Clark, C. R. N. 46 Dohrmann, J. K. 38 Babbage, C. 183 Browning, R. G. 82 Claver, C. 101 Douglas, A. W. 40 Bachilo, S. M. 81 Bruenger, W. H. 15 Clayton, D. D. 173 Dragutan, I. 148 Badarinarayana, V. 82 Brunet, J.-J. 142 Cleghorn, L. A. T. 40 Dragutan, V. 148 Baglin, J. E. E. 38 Buchanan, D. 139 Cleghorn, S. 35 Baglio, V. 83 Bucsi, I. 104 Coe, B. J. 103 Echigo, M. 40 Bailey, R. T. 81 Bulina, N. V. 81 Collet-Descotils, Edison, T. 187 Balch, A. L. 140 Burch, R. 70 H. V. 182 Efstathiou, 70, Banks, J. 184 Collier, P. J. 169 A. M. 155 Barkschat, A. 38 Cabot, C. 176 Constable, E. C. 157 Einaga, H. 81 Barnard, 101, Cadena, M. 142 Cooper, I. R. 40 Emura, S. 83 C. F. J. 157 Cameron, D. S. 32 Coussmaker, A. B. 134 Engelmann, F. M. 80 Barrow, J. 182 Campagna, S. 168 Coutanceau, C. 83 Enick, R. M. 190 Beck, P. A. 83 Campos-Martin, Couto, O. D. D. 140 Ermolina, M. V. 39 Beletskaya, 39, J. M. 170 Crell, L. 183 Evrard, B. 191 I. P. 102, 142 Canipelle, M. 38 Crilly, P. J. 81 Beller, M. 191 Cano-Serrano, E. 170 Crookes, W. 187 Fairlamb, I. J. S. 142 Bennett, S. C. 157 Cao, G. 79 Cugini, A. V. 190 Fantini, J. 132 Bergamini, P. 140 Caron, L. 38 Cui, J. 79 Faraday, M. 186 Bergbreiter, D. E. 192 Carson, N. A. P. 90 Curtin, D. 35 Faria, J. L. 155 Berger, R. 15 Casas, J. S. 190 Cutler, C. S. 104 Farrell, N. 103 Berthollet, C. L. 182 Caseri, W. 91 Faulkner, S. 104 Bertolasi, V. 140 Cerdeira, F. 140 Dai, H. 83 Fenton, D. E. 64 Berzelius, J. J. 183 Chandler, B. D. 170 Daniel, S. 29 Fierro, J. L. G. 170 Besenyei, G. 190 Chang, P. W. 80 De Clerck, K. 38 Fiorani, D. 83

Platinum Metals Rev., 2004, 48, (4), 195–198 195 Page Page Page Page

Fisher, J. M. 101, 154 Hanan, G. S. 168 Johnston, R. L. 140 Kurchatov, L. V. 173 Formiga, A. L. B. 80 Haneda, M. 39 Jollie, D. M. 33 Fraser Stoddart, J. 83 Hara, K. 81 Jones, J. 32 La Parola, V. 170 Friedlander, G. 173 Harada, H. 79 Jones, T. 59 Lamy, C. 83 Friedrich, H. B. 40 Hartmann, R. 82 Joo, O.-S. 191 Landon, P. 169 Fuchs, E. 82 Hartung, C. G. 191 Joseph, Y. 141 Lang, H. 170 Fukuoka, A. 154 Hartwig, J. F. 102 Jung, K.-D. 191 Lapin, A. Yu. 125 Fullerton, E. E. 38 Hattori, T. 192 Jurisson, S. S. 104 Larhed, M. 192 Furyk, S. 192 Helm, L. 103 Latyshev, G. D. 173 Futamura, S. 81 Henling, L. M. 149 Kariuki, N. N. 170 Lau, M.-K. 190 Herschel, J. 183 Karuna, M. S. L. 81 Lau, T.-C. 157 Gaffo, L. 140 Heumann, J. G. 173 Kasem, K. K. 39, 159 Laughlin, D. 38 Gahn, J. 182 Higashiguchi, S. 40 Kashin, A. N. 142 Lavoisier, A.-L. 182 Gaikwad, A. G. 191 Hirai, K. 40 Katayama, H. 149 Le Beyec, Y. 176 Gair, S. 61 Hoggard, P. E. 80 Katsuki, T. 101 Lee, A. F. 142 Galvão, D. S. 140 Holder, E. 190 Keep, A. K. 64 Lee, E. J. H. 142 Gao, T. 132 Holladay, J. D. 36 Kellock, A. J. 38 Léger, J.-M. 83 Gao, Z.-X. 191 Holly, S. 190 Kendall, T. 13 Lehmann, T. E. 82 Garcia, S. 154 Hoogenboom, R. 190 Keresztury, G. 190 Leite, E. R. 142 Garnier, E. 83 Hotchandani, S. 80 Keyes, T. E. 191 Lerou, J. J. 169 Gasana, E. 38 Housecroft, C. E. 157 Kiekens, P. 38 Letzkus, F. 15 Gauvin, H. 176 Howard, B. H. 190 Kiely, C. J. 169 Leung, W.-H. 190 Generosi, A. 83 Hu, X. 168 Killmeyer, R. P. 190 Lever, S. Z. 104 Geng, C.-H. 191 Huang, C. 79 Kim, B.-O. 140 Ley, S. V. 15 Ghosh, S. K. 191 Huddleston, L. 159 Kim, J. H. 140 Li, H. 83, 142 Gillanders, R. N. 81 Hunt, L. B. 134 Kim, S. M. 140 Li, H.-L. 142 Giro, R. 140 Huo, C. 141 Kim, Y. K. 140 Li, J. 80 Gladis, J. M. 29 Hutchings, G. J. 155, 169 Kim, Y. S. 140 Li, R. 40 Glushenko, G. A. 81 King, S. A. 40 Li, W. 83 Gnann, M. 37 Ibusuki, T. 81 Kintaichi, Y. 39 Li, X. 142 Goncharov, P. M. 125 Idriss, H. 105 Klemmer, T. J. 38 Li, Z. 80 Gordon, C. L. 39 Iglesia, E. 155 Knowles, W. S. 188 Liang, C. 83 Gourd, J. E. 15, 63 Ikegami, S. 141 Kobayashi, S. 102 Liang, P. Y. 80 Govender, M. 40 Ishizaki, M. 190 Kobayashi, Y. 190 Lima, A. 83 Grätzel, M. 103, 168 Ito, S. 79 Koehler, K. 191 Lin, H. 132 Gregory, P. 103 Itoh, S. 117 Kohyama, M. 192 Lin, X. N. 79 Griffith, W. P. 182 Iversen, B. L. 170 Koide, Y. 140 Lin, Y. 170 Grigg, R. 40 Iwatsuki, S. 117 Kondratenko, E. V. 81 Liu, C. 38 Grot, S. 35 Kong, J. 83 Liu, H. 141 Grubbs, R. H. 148 Jacob, K. 142 Koriyama, A. 190 Liu, K.-L. 12 Guldi, D. M. 80 Jain, V. K. 16, 116 Kotani, M. 140 Liu, P. 40 Gunning, H. 182 James, R. D. 79 Krüger, J. 82 Liu, X. M. 80 Guse, B. 141 Janot, R. 39 Kucernak, A. 141 Liu, Y. 80 Jasulaitene, V. 40 Kuhn, O. 82 Lloyd, L. D. 140 Ha, Y. 140 Javey, A. 83 Kumano, T. 71 Lobban, L. L. 39 Haber, F. 187 Jayaweera, P. 191 Kumashiro, R. 83 Loeschner, H. 15 Haddon, R. C. 132 Jeppesen, J. O. 83 Kundu, S. 191 Logadottir, A. 40 Hajbolouri, F. 192 Jiang, J. 141 Kuninobu, Y. 79 Loiseau, F. 168 Hamada, H. 39 Jiang, L. 83 Kunkely, H. 80 Lokhande, C. D. 191 Han, L. 170 Johnson, D. R. 79 Kupniewska, A. 40 Longo, E. 142 Han, W. 141 Johnson, L. K. 148 Kuppusami, P. 191 Lotz, S. 140

Platinum Metals Rev., 2004, 48, (4) 196 Page Page Page Page

Louie, J. 150 Min, X. 168 Noro, Y. 190 Proust, D. L. 185 Lovely, C. J. 82 Minor, M. M. 173 Nørskov, J. K. 40 Provine, W. D. 169 Lu, T.-H. 12 Mitin, A. V. 142 Novak, B. M. 148 Puzir, A. P. 81 Luo, J. 170 Mitra, P. 65 Noyori, R. 154, 188 Lupton, D. F. 72 Mizuno, N. 40 Qin, D.-H. 142 Lvovich, V. F. 58 Modica, E. 83 O'Hair, R. A. J. 79 Qui, J. 83 Lydon, J. D. 104 Mogano, D. 171 Ohlberg, D. A. A. 83 Quignard, F. 102 Möller, H. 190 Ohmura, T. 191 Maat, S. 38 Monflier, E. 38 Okumura, M. 192 Raghukumar, V. 141 MacDougall, B. 82 Montoya, A. 191 Onani, M. O. 40 Rakotondrainibé, MacLachlan, W. S. 40 Morandi, S. 70 Opstal, T. 152 A. F. 83 Madhavan, J. 141 Mori, K. 56, 138 Ould-Ely, T. 38 Ramakrishnan, Maeda, Y. 192 Mori, Y. 102 Ozawa, F. 149, 190 V. T. 141 Maggini, M. 80 Morley, C. P. 116 Ozawa, T. C. 190 Raman, R. K. 83 Magnani, R. 142 Morreale, B. D. 190 Ramarao, C. 15 Mahalingam, T. 39 Mortimer, R. J. 103 Pacheco, M. C. 192 Raub, C. J. 66 Mahlendorf, F. 35 Mothes, E. 142 Paci, B. 83 Reetz, M. T. 102 Mahmud, H. 82 Moutet, J.-C. 102 Pal, M. 82 Reeve, R. W. 36 Maiti, H. S. 65 Muegge, B. D. 80 Pal, T. 191 Reichert, K.-H. 39 Makhoba, X. 40 Murakami, H. 191 Panfilov, P. 47 Reynolds, T. D. 79 Mallinson, R. G. 39 Panik, F. 32 Rhee, H.-K. 140 Mandal, M. 191 Nagata, Y. 190 Paolucci, F. 80 Richter, M. M. 80 Manfredotti, C. 71 Nagy, A. 190 Pápai, I. 190 Roche, C. T. 173 Mann, D. 83 Nájera, C. 192 Papworth, A. J. 169 Romero, Y. 190 Manthiram, A. 192 Nakamura, E. 79 Parajó, Y. 190 Ross, P. N. 171 Marchetti, F. 101 Nakamura, M. 80 Parasuraman, K. 82 Rougier, A. 39 Marin, V. 190 Nam, E. J. 140 Park, B.-O. 191 Rowley, N. M. 103 Markovic, N. M. 171 Narasimha Rao, Park, H.-S. 191 Rupprechter, G. 155 Martin, A. 36 K. 81 Park, J. 82 Rushforth, R. 30 Martini, D. 101 Naslund, H. R. 170 Park, N. G. 140 Maruthamuthu, P. 141 Nasr, C. 80 Párkányi, L. 190 Sagawa, T. 190 Masui, D. 71 Navarro, R. M. 170 Partington, J. R. 186 Saikia, A. K. 141 Matsuo, Y. 79 Nazeeruddin, Pawelec, B. 170 Sailor, M. J. 132 Matthews, J. L. 104 Md. K. 103 Pérez-Ramírez, J. 81 Saiprasad, P. S. 81 May, R. A. 170 Nazri, G. A. 39 Pettinari, C. 101 Salge, J. R. 81 Maye, M. M. 170 Nemenov, L. M. 173 Pinel, C. 142 Salhi, S. 140 McCleverty, 64, 101, Ngcobo, T. D. 40 Pistorius, P. C. 190 Salmones, J. 191 J. A. 157 Nguyen, S. T. 148 Pizani, P. S. 142 Samanta, C. 191 McCredie, G. M. 39 Nielsen, K. A. 83 Plamper, F. 79 Samata, H. 190 McElrath, K. O. 168 Niemantsverdriet, Plant, J. 139 Sánchez-González, McFadyen, W. D. 79 J. W. 180 Platzgummer, E. 15 A. 190 McGarvey, J. J. 191 Niemelä, E. H. 142 Plietker, B. 192 Sanford, M. S. 149 Merbach, A. E. 103 Nier, A. O. C. 173 Pontes, F. M. 142 Sarode, P. R. 83 Meyer, 64, Niggemann, M. 192 Potter, R. J. 101 Sato, H. 140 T. J. 101, 157 Nilsson, P. 79, 192 Prabhavathi Devi, Sato, K. 39 Mhadgut, S. C. 104 Nishihata, Y. 15 B. L. A. 81 Satsuma, A. 192 Micheli, A. L. 141 Nishikawa, T. 81 Prasad, R. B. N. 81 Sayama, K. 81 Mikolajczyk, M. 116 Njoki, P. 170 Prasada Rao, T. 29 Scheele, C. 182 Milani, F. 140 Noda, K. 117 Pratt, A. S. 59, 134 Scherer, G. G. 192 Miller, T. J. 39 Noebe, R. D. 38 Priolkar, K. R. 83 Schmidt, L. D. 81, 155 Mills, P. L. 169 Nogueira, A. F. 80 Pronier, S. 83 Schmidt, T. J. 171

Platinum Metals Rev., 2004, 48, (4) 197 Page Page Page Page

Schomäcker, R. 39 Tabata, T. 40 Verykios, X. E. 81 Williams, I. D. 190 Schubert, U. S. 190 Takagi, H. D. 117 Villa, R. 71 Wilson, N. T. 140 Schwab, P. 148 Takahashi, H. 141 Villers, D. 40 Winkler, K. 140 Scurrell, M. S. 171 Takami, S. 40 Viola, V. E. 173 Winnischofer, H. 80 Seaborg, G. T. 173 Takao, Y. 79 Vnukova, N. G. 81 Wohnrath, K. 140 Selenov, I. P. 173 Takeda, K. 141 Vogler, A. 80 Wokaun, A. 192 Seshan, K. 155 Takeda, T. 79 Völkening, J. 173 Wollaston, W. H. 182 Setsune, J. 79 Tanaka, K. 82 Volkov, A. Yu. 3, 78 Wong, W.-T. 190 Shaikhutdinov, S. 154 Tanaka, R. 190 von Schenck, H. 192 Wood, A. I. 90 Shan, Zh. Q. 142 Tanase, M. 38 von Welsbach, C. 187 Wootsch, A. 154 Sharpless, K. B. 188 Tang, J. M. 132 Vos, J. G. 191 Wu, M.-C. 141 Shibata, J. 192 Taniguchi, T. 190 Vossmeyer, T. 141 Wu, X. 38, 142 Shibutani, T. 38 Tarascon, J. M. 39 Wysocka, M. 140 Shield, T. W. 79 Tatarnikov, A. V. 125 Wagner, M. 191 Shinke, N. 40 Tedford, M. C. 81 Wagner, S. 36 Xin, Q. 83 Shioyama, H. 168 Temmerman, E. 38 Waje, M. 132 Xiong, L. 192 Shneerson, Ya. M. 125 Tennant, S. 182 Walczyk, T. 173 Xu, M. 142 Shukla, A. K. 83 Thiébaut, B. 62 Wales, A. E. 182 Shukla, N. 38 Thiers, L. A. 187 Walworth, J. 80 Silver, J. 103 Thomas, J. M. 70 Wang, C. 132 Yamabe-Mitarai, Y. 79 Simpson, P. R. 139 Thomas, S. 170 Wang, C. M. 80 Yamada, Y. M. A. 141 Singh, A. K. 116 Thompson, D. T. 169 Wang, F. B. 142 Yamagishi, T. 71 Singh, H. B. 116 Thompson, S. J. 139 Wang, G. 83 Yamaguchi, K. 40 Sinha, C. 12 Thomson, T. 182 Wang, J. 168 Yamaguchi, M. 71 Smiechowski, M. F. 58 Tian, J. H. 142 Wang, J. A. 191 Yamashita, Y. 102 Smith, K. A. 168 Tilloy, S. 38 Wang, L. 170 Yan, Y. 132 Smith, M. D. 15 Toma, H. E. 80 Wang, M. 81 Yanagi, H. 38 Sokolskaya, I. 125 Tominaga, K. 155 Wang, Q. 83 Yang, L. X. 82 Solina, D. M. 39 Torbati, R. 70 Wang, R. J. 142 Yang, Y. 168 Solovyov, L. A. 81 Török, B. 104 Wang, S. 83 Yao, S. 81 Somorjai, G. 154 Török, M. 104 Wang, S. F. 39 Yasuda, A. 141 Song, Y. 190 Tóth, É. 103 Wang, X. 132 Yeleswarapu, K. R. 82 Sordo, J. 190 Tributsch, H. 38 Ward, M. D. 101 Yermakov, A. 47 Soto, G. 141 Tsyboulski, D. A. 81 Watling, T. 180 Yoshida, H. 192 Sotto, L. 170 Wee, S. 79 Yoshinari, T. 39 Sowerby, J. 185 Uemura, S. 116 Weidenthaler, C. 38 Yu, J.-K. 12 Spliethoff, B. 38 Weisman, R. B. 81 Sridharan, V. 40 Vacha, M. 140 Weller, D. 38 Zhang, F. 191 Stamenkovic, V. 171 Valenzuela, M. A. 191 Wendt, O. F. 79 Zhang, H.-L. 142 Stanley Williams, R. 83 van Koten, G. 149 Westbroek, P. 38 Zhang, J. Y. 142 Steel, M. C. F. 34 van Leeuwen, Whishaw, J. 182 Zhang, Q.-F. 190 Steldt, F. R. 39 P. W. N. M. 101 White, J. M. 79 Zhang, X. G. 80 Stengl, G. 15 Varela, J. A. 142 White, 12, 58, Zhang, Y. 142 Stepan, A. F. 15 Varvaro, G. 83 K. W. P. 104, 168 Zhao, B. 141 Stewart, D. R. 83 Vaultier, M. 82 White, 15, 29, 71, 132, Zhong, C.-J. 170 Su, Y.-K. 142 Vauquelin, L. N. 182 P. 133, 138, 168 Zhou, J.-L. 191 Subramanian, V 82 Vázquez-López, Whittlesey, K. 101 Zhou, W. 83 Sun, G. 83 E. M. 190 Wilkins, A. J. J. 44, 58 Zhou, Z. 83 Sun, X. 40 Venezia, A. M. 170 Wilkinson, R. 88, 145 Ziller, J. W. 148 Swift, P. D. 39 Venugopal, A. 171 Willeke, A. 34 Zimmerman, A. N. 39 Szalontai, G. 190 Verpoort, F. 152 Willey, D. B. 134 Zingg, E. 173

Platinum Metals Rev., 2004, 48, (4) 198 SUBJECT INDEX TO VOLUME 48 Page Page a = abstract Carbanions, arylation, a 142 Acetophenone, asymmetric hydrogenation, a 82 Carbon, nanotubes 83, 168 Acetoxylation, 1,3-cyclopentadiene 16 Carbon Oxides, CO, adsorption, on CeO2 105 Acetylation, alcohols, primary, secondary, a 141 CO2:CO ratio, EtOH TPD 105 Acetylenes, insertion, [Pt(GeMe3)(SnMe3)(PMe2Ph)2], a 190 copolymerisation, with alkenes 101 Acylation, alkynes, a 192 effect on, H2 sensor 132 Alcohols, ethyl, electrooxidation, a 40 electrooxidation 40, 169 H2 production 105 hydrogenation 16, 154 + H2O, reforming, a 81 oxidation 40, 141, 154, 169, 191 interaction, with CeO2, M/CeO2 105 PROX 154 oxidation 105, 154 reaction with hot O2, a 81 reforming, a 81 for reduction of NO, a 39 in fuel cells 32 tolerance, of anodes, for PEFCs, a 192 homoallylic, by class 1 cascade reaction, a 40 CO2, CO2:CO ratio, EtOH TPD 105 methyl, carbonylation 101 from CO + hot O2, a 81 decomposition 169 from EtOH oxidation 105 electrooxidation 40, 82, 83, 169 Carbonylation, MeOH 101 from hydrogenation of CO 16 Catalysis, asymmetric 82, 101, 104, 142, 154 oxidation, aerobic, a 40 biphasic, a 141 to aldehydes, ketones 157 book reviews 101, 180 in preparation, of Pd colloids, Ru colloids 62 conferences 70, 154, 169 primary, secondary, acetylation, a 141 heterogeneous, a 39–40, 81, 141, 191–192 Aldehydes, in class 1 cascade reaction, a 40 homogeneous, a 40, 82, 142, 192 hydrogenation 169 Catalysts, bifunctional reforming 180 Alkanes, activation 155 pgm/CeO2 + Fe-MgO, reforming of biomass 154 hydroisomerisation, a 191 recycling 15, 141, 192 oxidation 71 Catalysts, Iridium, fibre, Ir , Ir oxide 138 Alkanethiols, dehydrogenation, a 82 Ir, in synthesis of fullerenes, a 81 Alkenes, aminohydroxylation, dihydroxylation 157 Ir/Al2O3, preparation, a 39 copolymerisation, with CO 101 Ir/magnesia, for C nanotubes, peparation 168 cyclic, ROMP 101 Ir/Na-MOR, Ir/Na-zeolite, SCR of NO, a 192 hydroformylation 82, 154 Ir/SiO2, SCR of NO with CO, + O2 and SO2, a 39 hydrogenation 154 Ir/TiO2, local barrier height, a 192 hydroxylation, a 40 Catalysts, Iridium Complexes, bis(oxazoline) Ir(I), a 142 isomerisation 16 CativaTM process 101 Alkylation, reductive, anilines 16 hydroamination 101 Alkynes, acylation, a 192 Ir(I), Ir(III), book review 64 Allene, in class 1 cascade reaction, a 40 Ir phosphines, hydroamination of 1,3-dienes 101 Alloys, dental, porcelain 30 Ir sulfide, hydrodenitrogenation, of amines, quinolines 16 Allylation, Barbier type, a 40 Ir2S3, hydrodesulfurisation of thiophenes 16 Amides, N-arylation, solvent-free, a 39 reduction of nitrobenzene 16 – Amines, alkylation, reductive 16 KxFey[Ir(CN)6]z, reduction of IO3 159 N-arylation, solvent-free, a 39 Catalysts, Osmium, Os/Cu-Al-hydrotalcite, a 40 coordination of, to Pd(II) porphyrins, a 79 Os/magnesia, for C nanotubes, preparation 168 hydrodenitrogenation 16 Catalysts, Osmium Complexes, dihydroxylation 101 in Magnus’ green salt derivatives 91 Os clusters, hydrogenation 101 oxidation, aerobic, a 40 OsO4, amino-, di-, hydroxylation, of alkenes 157 – Ammonia, sensor, a 141 [OsO4] 157 synthesis, a 141 OsS2, reduction of nitrobenzene 16 Anilines, in hydroaminations, a 142 Catalysts, Palladium, Ag–Pd–Y-zeolite, for ethylene, a 39 wet air oxidation 154 with Au, Au/Pd, Au-Pd/Al2O3, hydrogenation 169 Aryl Halides, in reactions 15, 39, 40, 82, 141, 191 Au/Pd, Au-Pd/Al2O3, H2O2 synthesis 169 Arylation, a 39, 142, 191, 192 Au/Pd/SiO2, dibenzothiophene hydrodesulfurisation 169 Arylboronic Acids, for Heck arylations, a 192 Au/Pd/TiO2, CO oxidation 169 Autocatalysts, book review 180 Au-Pd/TiO2, H2O2 synthesis 154 effects of oil additives 44 Au(100)/, Au(111)/Pd, electrooxidation, of CO, H2 169 EtOH reactions 105 Pd-Au, Pd-Au/SiO2 + KOAC, VAM production 169 Aziridination, Ru salens, as catalysts 101 Pd/Au, H electrode catalyst 169 Pd/Au/C, selective oxidation of glyoxal 169 Benzene, photooxidation, a 81 Pd/Au/CeO2, MeOH decomposition 169 Biodiesel, partial oxidation 154 Pd-Al2O3/NiAl(110), hydrogenation, of C2H4, CO 154 Biomass, reforming, for H2 production 154 Pd/Al2O3, /C, /MgO, /SiO2, Heck reactions, a 191 – Book Reviews, “Comprehensive Coordination Pd/Al2O3, /Ga2O3 , /SiO2, /zeolite, /ZrO2,+Br , H2O2, a 191 Chemistry II” 64, 101, 157 Pd/Al2O3 + proline, asymmetric hydrogenation 104 “Concepts of Modern Catalysis and Kinetics” 180 Pd nanoparticles/ordered Al2O3 films, hydrogenation 154 “Electrodeposition of the Precious Metals” 59 Pd/C, transfer hydrogenation of safflower oil, a 81 Boronic Acids, Suzuki couplings 15 Pd/CeO2, Pd/Ce0.8Zr0.2O2, CO oxidation, a 191 Buchwald-Hartwig Couplings, in synthesis, a 82 Pd/magnesia, for C nanotubes, preparation 168 Pd perovskites, LaFe0.57Co0.38Pd0.05O3, Suzuki couplings 15 Cancer, anti-, Pt complexes 101 Pd-polyacrylic acid membranes, a 39 Capacitors, Au/BaTiO3/Pt, thin films, a 142 Pd/Se/SiO2, isomerisation of alkenes 16 NiO/RuO2 electrode, a 80 Pd/SiO2, preparation, a 39

Platinum Metals Rev., 2004, 48, (4), 199–204 199 Page Page Catalysts, Palladium, (cont.) Catalysts, Platinum Complexes, hydrosilylation 101 Pd/Te/C, 1,4-butanediol production 16 Pt(0), models, for hydrosilylation 64 Pd/Te/SiO2, isomerisation of alkenes 16 PtBr2, in n-Bu4PBr, hydroamination of ethylene, a 142 PdCl2-CuCl2, acetylation of alcohols, a 141 Pt selenides/tellurides, reductive alkylation of anilines 16 II PdO/Al2O3, PdO/ZrO2, CH4 combustion 70 Pt SnCl2/phosphines, hydroformylation 101 PdS/aluminosilicate, hydrogenation of thiophenes 16 PtS, polycondensation, hydrodesulfurisation 16 Pd sulfide/Al2O3, /C, /SiO2, hydrogenation 16 Pt telluride, reduction of nitrobenzene 16 Pd sulfide/C, hydrodenitrogenation 16 Catalysts, Rhodium, alkane activation 154 2+ Pd(0)/, Pd(II)/, [Pd(NH3)4] /zeolites, Heck reactions, a 191 Pt-Rh, gauze, N2O decomposition, a 81 Pd–Y-zeolite, ethylene production, a 39 Pt-Rh/, Rh-Au/, Rh-Pd/CeO2, EtOH reactions 105 Pt-Pd/CeO2, Rh-Pd/CeO2, EtOH reactions 105 Rh/CeO2, reforming of EtOH, a 81 single crystals, Pd(111), hydrogenation, of alkenes, CO154 Rh/magnesia, for C nanotubes, preparation 168 Catalysts, Palladium Complexes, ArPdL2CHXY 142 Rh-MgO, reforming of biomass 154 4-CF3C6H4 Pd(PPh3)2Br, reaction with carbanions, a 142 Rh/SiO2, preparation, a 39 cross-couplings, C-C, C-N, C-O, C-P, C-S, C-Se 101 Rh/TiO2, benzene photooxidation, a 81 hydroboration, hydroformylation 101 Rh-Te, production of unsaturated glycol diesters 16 hydroxycarbonylation, methoxycarbonylation 101 Rh2Te/activated C, 1,3-cyclopentadiene acetoxylation 16 (NH4)2PdCl4 + phosphine polymer, Heck reactions, a 141 Catalysts, Rhodium Complexes, bis(oxazoline) Rh(I), palladacycles, coupling reactions, a 191, 192 asymmetric hydrogenation, a 142 Pd + chelating bidentate phosphines, alkene + CO 101 cyclopropanation, intermolecular, intramolecular 101 Pd 1,2-diimine, ethylene polymerisation 101 hydroamination, hydrosilylation 101 Pd ferrocenyl phosphines, hydrosilylation of styrene 101 phosphabarrelene-Rh, hydroformylation, alkenes, a 82 Pd/In, + additives, Barbier type allylations, a 40 Rh BINAP, asymmetric hydrogenation 154 Pd0/L, + graphite, solvent-free N-arylation, a 39 Rh + P-containing ligands, hydride transfer; reduction 101 t Pd2dba3/3PPh3, /3P Bu3, arylation of carbanions, a 142 Rh phosphines, hydroamination of 1,3-dienes; Pd2dba3/Xantphos, Buchwald-Hartwig couplings, a 82 hydroboration; hydroformylation 101 Pd2(dba)3.dba/PCy3, Pd(OAc)2/PPh3, Heck reactions, a 191 Rh phosphites, hydroformylation 101 Pd(OAc)2 +dimethylphenanthroline, Heck arylations, a 192 Rh selenides/tellurides, reductive alkylation of anilines 16 Pd(PPh3)4 (from Pd(OAc)2 + PPh3), + rac-BINAP, a 82 Rh sulfide, hydrodenitrogenation, amines, quinolines 16 (Ph3P)2PdCl2, + inhibitor, in Sonogashira coupling, a 142 RhS2, dehydrogenative polycondensation 16 (PPh3)2PdCl2 + CuI, with (S)-prolinol, for flavones, a 82 Rh2S3, hydrodesulfurisation of thiophenes 16 Pd phosphines 64, 101 Rh telluride, reduction of nitrobenzene 16 Pd selenides/tellurides, reductive alkylation of anilines 16 [RhCl(COD)]2/TPPMS, myrcene + ethyl acetoacetate, a 82 Pd sulfide, hydrogenation, of CO, thiophenes 16 [Rh(cod)2]BF4/PPh3, dehydrogenation of alkanethiols, a 82 PdS, polycondensation, hydrodesulfurisation 16 Catalysts, Ruthenium, alkane activation 154 PdS2, reduction of nitrobenzene 16 Au/Ru/α-Fe2O3, WGSR 169 Pd telluride, reduction of nitrobenzene 16 electrocatalysts, PtRu, for fuel cells, a 40, 82, 83,192 Catalysts, Platinum, alkane activation 154 PtRuWOx/C, a 82 with Au, Au/Pt/oxide support, reactions 169 Ru, anodes, for PEMFCs, a 40 Au/Pt/SiO2, Au/Pt/TiO2, preparation 169 Pt/Ru + Au/TiO2, MeOH electrooxidation 169 Au16Pt16/SiO2, light off 169 Ru/activated C, NH3 synthesis, a 141 Pt/Au/HY zeolite, hydrocarbon isomerisation 169 Ru/Al2O3, aerobic oxidations, alcohols, amines, diols, a 40 electrocatalysts, Au/Pt/C, for fuel cells 169 for CO oxidation, in reformed gas, a 40 Pt, for fuel cells, a 40, 192 Ru/C MWNTs, wet air oxidation of aniline 154 Pt-Co/C, for PEMFCs, a 142 Ru/C nanofibre, preparation 154 Pt-Fe/C, for DMFCs, a 83 Ru/α-Fe2O3, WGSR 169 Pt/C, a 82, 83, 142, 192 Ru/magnesia, for C nanotubes, preparation 168 Pt/C MWNTs 40, 83, 132 Ru sulfide/alumina, /Y-zeolite, pyridine hydrogenation 16 Pt/PEDT, Pt + Pb/PEDT, Pt + Sn/PEDT, a 40 RuS2/dealuminated KY zeolite, hydrogenation 16 Pt/TiOx/C, for DMFCs, a 192 RuS2/SiO2, /zeolites, decomposition of H2O16 PtRu, for fuel cells, a 40, 82, 83, 192 Ru2Se3, reductive alkylation of anilines 16 PtRuWOx/C, PtWOx/C, a 82 Catalysts, Ruthenium Complexes, bis(oxazoline) Ru(II), Pt3Sn, anodes, for PEMFCs, a 40 asymmetric hydrogenation, a 142 Pb-modified Pt, CO oxidation, a 141 chloro(Me2SO)Ru(II), light-driven alkane oxygenation 71 Pt, for hydrocarbons sensor, a 141 cyclopropanation, intermolecular, intramolecular 101 in synthesis of fullerenes, a 81 Grubbs’ catalyst 148 Pt/, Pt-Cu/hydrotalcites, NOx storage-reduction 70 Noyori’s catalyst 82, 101 Pt nanoparticles/SiO2 154 perruthenate, selective oxidant, alcohols 157 Pt nanowires, Pt/alumina, /ceria-zirconia, PROX 154 Ru BINAP, asymmetric hydrogenation 154 Pt sulfide/C, hydrodenitrogenation, hydrogenation 16 Ru(II)–BINAP, preparation, structure, a 40 Pt-BaO/Al2O3, NOx storage-reduction 70 Ru carbonyls, hydroformylation of alkenes 154 Pt-Pd/, Pt-Rh/CeO2, EtOH reactions 105 Ru clusters, hydrogenation 101 Pt-Rh, gauze, N2O decomposition, a 81 Ru metalloporphyrins, metallosalenes, epoxidation 101 Pt/Al2O3, NO reduction 70 Ru phosphines, hydroamination of 1,3-dienes 101 Pt/C nanofibre, preparation 154 RuII salens, aziridination 101 Pt/Ce0.6Zr0.4O2/Al2O3, NOx storage-reduction 70 Ru selenides/tellurides, reductive alkylation of anilines 16 Pt/CeO2, CO + H2O, a 81 Ru vinylidenes, metathesis: CM, RCM, ROMP 148 Pt/p-InP, H2 evolution, a 38 RuCl2[(S)-binap][(S,S)-dpen], hydrogenation, a 82 Pt/magnesia, for C nanotubes, preparation 168 RuCl2(diphosphine)(1,2-diamine), synthesis 101 Pt/Mg-Ce-O, NO reduction 70 RuO4, di-, keto-hydroxylation, monooxidation, a 192 Pt/Ru + Au/TiO2, MeOH electrooxidation 169 RuS, dehydrogenative polycondensation 16 Pt/SAPO-11, hydroisomerisation of n-alkanes, a 191 RuS2, dehydrogenation, hydrodesulfurisation 16 Pt/SiO2, preparation, a 39 Ru2Se3, reduction of nitrobenzene 16 TM Pt/Te/SiO2, isomerisation of alkenes 16 Cativa Process, MeOH carbonylation 101 Pt/ZrO4, steam reforming of acetic acid 154 Cerium, CeO2, catalyst support: M/CeO2 105

Platinum Metals Rev., 2004, 48, (4) 200 Page Page Chalcogenides, pgm, synthesis, uses 16, 116 Electrolytes, Ir, Os, Pt-Ir, Rh, Ru, book review 59 Chemiluminescence, see Luminescence Electronic Devices, Pt/organic monolayer/Ti, a 83 Chlorination, pgms concentrate 125 Emission Control, motor vehicles 44, 180 Chlorine, exposure, Rh phthalocyanine films, a 140 Epoxidation, chiral 101 Chloroalkali, anodes 63 Ethylene, hydroamination, a 141 Circular Dichroism, Magnus’ green salt, derivatives 91 polymerisation 101 Clusters, Pt-Pd nanoalloy, a 140 production, in a DC plasma reactor, a 39 CM, allyl benzene 148 Extraction, Pd ions, using Pd ion imprinted polymer 29 Coatings, Ir-Ta, by DC magnetron sputtering, a 191 pgms 101 Pd, on Mg2Ni–C, for H2 sorption, a 39 Coins, roubles 66, 72, 134 Fabric, Pt, manufacture, uses 56 2+ Colloids, clay, with Ru(bpy)3 , a 80 Fibres, Ir, Ir oxide, production, use 138 Pd, Ru, stabilised in polymer 62 Pt, manufacture, uses 56 Pdcore–Agshell, Pdcore–Aushell, preparation, a 191 [Pt(NH2R4)][PtCl4]91 Combustion, CH4 70 Films, C60Pd, by electropolymerisation, a 140 Composites, PdS with polymers 16 FePt3, ferromagnetism, a 38 Pt-Al2O3, mechanical properties 47 oxide, on Ir wire 58, 81 Conferences, 8th Grove Fuel Cell Symp., London, 2003 32 PdS polymer composites 16 13th Int. Congress on Catal., Paris, 2004 154, 169 Pt-nanoparticles/nonanedithiol, a 141 EuropaCat-VI, Innsbruck, Austria, 2003 70 PtNx, by reactive laser ablation, a 141 3 IOM Materials Congress 2004, London, 2004 139 [Pt(NH2R)4][PtCl4]91 IX Int. Conf. Chem. Se and Te, Mumbai, 2004 116 Rh phthalocyanine, Cl2 exposure, a 140 Coupling Reactions 82, 101, 192 Ru-based hexacyanometallates, a 39 Creep, Pt, from Pt-Al2O3 crucibles 47 SnO2, with tris(2,2′-bipyridine)Ru(II)-fullerene dyad, a 80 Crucibles, Pt-Al2O3 47 TiO2, with porphyrin and Ru(II) polypyridyls, a 80 Crystals, CaRuO3, magnetism, a 190 see also Thin Films CVD, PdS thin films 16 ‘Final Analysis’ 44, 88, 145 Cycloalkenes, Heck arylation, a 191 Flavones, 3-alkynyl, synthesis, a 82 Cyclodextrins, + Rh complexes, a 38 Flotation, pgms concentrate 125 Cyclopropanation, inter- and intramolecular 101 Fracture, Pt-Al2O3 composite 47 Fuel Cells, a 40, 82–83, 142, 192 Decomposition, MeOH 169 AFC, in transportation, onboard H storage systems 61 Dehydrogenation 16, 82 conference, Eighth Grove Fuel Cell Symposium 32 Dendrimers, for nanoparticles 140, 169 DMFC, electrocatalysts, a 83, 192 Dental, porcelain alloys 30 electrocatalysts 40, 82, 83, 132, 142, 169, 192 Deposition, pgm chalcogenides 16 electroreduction 101 Detectors, see Sensors fuel, alcohols 32 Diesel, particulate filters 44 H2 32, 60, 61, 81, 180 Diffusion Couples, Pt/CdTe 16 MCFC 32 Dihydroxylation 101, 157, 192 membrane electrode assemblies 32, 132 Diols 16, 40, 190, 192 micro 32 Disulfides, from alkanethiols, a 82 motor vehicles 32, 60, 61, 132 PAFC 32 E-Journal 2, 46, 90 PEFC, anodes, Pt, PtRu, CO tolerance, a 192 Electrical Conductivity, Magnus’ green salt, derivatives 91 CO preferential oxidation removal reactor, a 40 Electrical Contacts, ohmic, Pd with C SWNTs, a 83 PEMFC, Airgen portable generators 32 on p-type (001) ZnTe, ZnSe 16 electrocatalysts 40, 132, 142 Electrical Resistivity, Pd-Cu-Ag 3 electrodes, a 142 Electrocatalysis, of pyrocatechol, a 80 MEAs 32 Electrochemistry, a 38, 80, 140, 190 miniature, as battery replacements 32 Au-Pt, Pt, electrodes, a 190 as power sources, for small portable electronics 132 co-reduction of H2PtCl6 and RuCl3, a 141 in transportation, using onboard H storage systems 61 Ir(III) polypyridyl + poly(ε-caprolactone)-bipyridine, a 190 Pt availability 32 III III KFex [Ir (CN)6]y 159 SOFC 32 preparation, dinuclear Ru(II) complex, a 191 stationary power generation 32 Ru(II) polypyridyl + poly(ε-caprolactone)-bipyridine, a 190 transportation 32, 60, 61 synthesis, Ru-based hexacyanometallates, films, a 39 Fuels, additive, EtOH 105 Electrodeposition, CoPt/Pt, nanowire arrays, a 142 Fullerenes, synthesis, a 81 Ir, Os, Pt-Ir, Rh, Ru, book review 59 III III KFex [Ir (CN)6]y thin films 159 Gauzes, Pt-Rh, N2O decomposition, a 81 RuO2 thin films, on Ti, a 191 Geology, PGEs, Africa, South Africa, U.K. 139 Electrodeposition and Surface Coatings, a 39, 141, 191 Glaser Couplings, palladacycle catalysts, a 192 Electrodes, Au-Pt, Pt, electrochemistry, a 190 Glucose, sensor, a 80 electrode/C60Pd/polypyrrole, properties, a 140 Glyoxalic Acid, from glyoxal 169 electrode/polypyrrole/C60Pd, properties, a 140 Gold, Au/pgms, in catalysis 169 in fuel cells, see Fuel Cells Grove Fuel Cell Symposium, Eighth 32 glassy C, modified with Ir-based hexacyanometallates 159 H, Pd/Au catalysts 169 Heck Reactions, a 141, 191, 192 Ir coatings, anodes, for chloroalkali 63 Hexacyanometallates, KxFey[Ir(CN)6]z 159 Ir wire, with oxide film, in sensors 58, 81 Kx–1RhyFe[Ir(CN)6]z 159 IrO2/SnO2, electrocatalysis of pyrocatechol, a 80 KRux[Fe(CN)6]y, KxRuy[Ir(CN)6]z, KRux[Ru(CN)6]y 159 NiO/RuO2, for electrochemical capacitors, a 80 History, Ir discovery, Smithson Tennant, initial uses 182 Pt, oxidation of Na dithionite, a 38 Os discovery, Smithson Tennant, initial uses 182 in Pt/organic monolayer/Ti devices, a 83 Os isotopes, discoverers, A. O. C. Nier, F. W. Aston 173 Ru coatings, anodes, for chloroalkali 63 roubles 66, 72, 134

Platinum Metals Rev., 2004, 48, (4) 201 Page Page

Hydroamination 101, 141 Lasers, reactive ablation, of PtNx films, a 141 Hydroboration, Pd catalysts, Rh phosphine catalysts 101 Leaching, autoclave oxidative, Pt flotation concentrate 125 Hydrocarbons, isomerisation 16, 169 Lithography, films, plates, Pd sulfide 16 reforming 32 London Platinum and Palladium Market 13 sensor, a 141 LPG, sensor 65 Hydrochlorination, pgms concentrate 125 Lubricants, sensors 58 photo-, of PtCl4, a 80 Luminescence, electrochemi-, (btp)2Ir(acac), F(Ir)pic, a 80 2+ Hydrodenitrogenation, amines, quinolines 16 Os(phen)2(dppene) , a 80 2+ Hydrodesulfurisation 16, 169 Ru(bpy)3 -modified clay colloids, a 80 Hydroformylation 82, 101, 154 Ir(ppz)3, blue, a 140 Hydrogen, by photoreactions 16, 38 [Os(CO)3X(dbm)] 12 by reforming, EtOH, EtOH-H2O, a 81 Pd complexes, Pt complexes, pressure effects 117 electrooxidation 40, 169 Ru(II) dinuclear complex, phenol bound, a 191 2+ from EtOH 105 Ru(tpy)2 complexes 168 fuel, for fuel cells 32, 60, 61, 81, 180 oxidation, a 191 Magnetism, CaRuO3 crystal, a 190 permeance, Pd-Cu foils, a 190 Co, with Pt, multilayers 15, 142 production 105, 154, 180 ferro-, Fe7Pd3, a 79 sensors 132 FePt3, a 38 sorption, by Mg2Ni–C, with Pd coating, a 39 Pt coins, Pt nuggets, Pt-Fe 66 Hydrogen Peroxide, synthesis 154, 169, 191 Sr4Ru3O10, a 79 Hydrogen Sulphide, effect, on H permeance, Pd-Cu, a 190 Magnus’ Green Salt, + derivatives, synthesis, structure 91 Hydrogenation, aldehydes 169 MEAs 32, 132 alkenes 154 Mechanical Properties, Pd-Cu-Ag 3 asymmetric 82, 104, 142 154 Pt-Al2O3 composite 47 CO 16, 154 Ru-Al-Mo, a 79 gasoline pyrolysis residue 16 Medical Uses, isotopes, Rh 101 low pressure, low temperature, a 40 photodynamic therapy, Pd, Pt, Ru complexes 101 microwave-assisted, safflower oil, a 81 Membranes, Pd nanoparticles-polyacrylic acid, a 39 naphthalene, nitrobenzene, pyridine 16 Metathesis, Ru vinylidene catalysts 148 selective, buta-1,3-diene 169 Methane, combustion 70 simultaneous, naphthalene + toluene 169 Methoxycarbonylation, Pd complexes, as catalysts 101 thiophenes 16 Microspheres, mesoporous, PtRu, a 141 toluene 169 Microwaves, in organic reactions, a 81, 192 Hydroisomerisation, n-alkanes, a 191 Mizoroki-Heck Reactions, palladacycle catalysts, a 192 Hydrometallurgy, Pd(II), Pt(II), Pt(IV) 101 MOCVD, low pressure, thin films, PdS, PtS, RuS2 16 Hydrosilylation, pgm complexes, as catalysts 64, 101 Hydrotalcites, catalyst support, a 40 Nanoalloys, Pt-Pd clusters, a 140 Hydroxycarbonylation, Pd complexes, as catalysts 101 Nanoclusters, PtS2 16 Hydroxylation, alkenes, a 40 Nanocomposites, Pt/TiOx/C, in DMFCs, a 192 amino-, alkenes 157 Nanocrystals, PdS, PtS 16 keto-, olefins, a 192 Pt tetraphenylporphyrin, a 38 Nanoparticles, Ag-Pd, a 140 Iodate, reduction 159 Au, Au-Pd 169 Ion Exchange, of pgm hydrochlorination solution 125 FePt, a 38 Ionic Liquids, solvent, a 82 Pd 39, 64, 191 Iridium, discovery, history 182 Pt 141, 154, 169 electrodeposition, book review 59 Nanostructures, magnetic recording pattern, Co/Pt 15 electrodes 58, 63 Nanotubes, C 83, 168 fibre, production 138 Nanowires, arrays, multilayed, CoPt/Pt, a 142 Ir-Ta, coatings, by DC magnetron sputtering, a 191 Naphthalenes, hydrogenation 16 wire, oxidation 58, 81 Nitrogen, from NO/H2/O2 70 Iridium Alloys, Pt–Al–Ir–Nb, a 79 Nitrogen Oxides, NO, reduction 39, 70, 169 Pt-Ir, electrodeposition, book review 59 selective catalytic reduction, in He + CO/H2, a 192 Iridium Complexes, electrochemiluminescence, a 80 NOx, -traps 44 Ir-based hexacyanometallates, see Hexacyanometallates storage-reduction 70 Ir(III) cyclometallates, S and Se donor ligands, a 190 N2O, decomposition, Pt-Rh gauze, a 81 Ir(III) polypyridyl+poly(ε-caprolactone)-bipyridine, a 190 Norbornenes, ROMP 148 Ir(ppy)3, phosphorescence, a 140 Ir(ppz)3, OLEDs, a 140 Ohmic Contacts, see Electrical Contacts Iridium Compounds, electrodes 58, 80, 81 Oils, engine, additives, effects on, autocatalysts 44 electrolytes, book review 59 sensors 58 Ir chalcogenides, synthesis, applications 16 safflower, hydrogenation, a 81 Ir oxide, fibre, production 138 OLEDs 12, 101, 140 Isomerisation, hydrocarbons 16, 169 Olefins, in reactions 148, 192 Isophorone, asymmetric hydrogenation 104 Optical Properties, pgm complexes 101 Isotopes, Os, discoveries 173 Ores, chrome, Pt-containing 125 Rh, in medicine 101 Osmium, discovery, history 182 electrodeposition, book review 59 Johnson Matthey, + BP Chemicals, catalyst for VAM 169 isotopes, history of the discoveries 173 “Platinum 2004” 133 Osmium Complexes, oxidation states, high, low 157 roubles 66, 134 luminescence 12, 80 Os(VI) oxo, Os(VI) polypyridyls 157 Ketones, hydrogenation, asymmetric transfer, a 142 phosphorescence 12 α-hydroxy, synthesis, a 192 solar cells 101

Platinum Metals Rev., 2004, 48, (4) 202 Page Page Osmium Compounds, electrolytes, book review 59 pH, sensor, a 81 Os chalcogenides, synthesis, applications 16 Phases, PtAl, Pt5Al3, a 38 OsO4, in electron microscopy 63 Pt3Al, L12 structure, a 79 Oxidation, aerobic, alcohols, amines, diols, a 40 transformation, in Fe-Pd, a 79 alkanes 71 Phosphorescence, Ir(ppy)3, a 140 autoclave, for leaching, of Pt flotation concentrate 125 [Os(CO)3X(dbm)] 12 CO 40, 141, 154, 169, 191 Pt porphyrins, a 38, 81 electro-, alcohols 40, 82, 83, 169, 190 Phosphorus, in engine oils 44 CO, H2 40, 169 Photocatalysis 16, 38 EtOH 105 Photoconversion, a 38, 80–81, 140–141, 191 H2, a 191 PdCl2, UV, a 191 Ir wire 58, 81 Rh phthalocyanine, Cl2 exposure, a 140 mono-, vic-diols, a 192 Photodynamic Therapy, Pd, Pt, Ru complexes 101 Na dithionite, a 38 Photoelectrochemistry, Ru(II) complexes, a 80 nanoparticles, FePt, a 38 Photography, films, PdS 16 partial, biodiesel, EtOH 154 Photooxidation, benzene, a 81 PROX, CO 154 Photoproperties, Ir(III), Ru(II), polypyridyls, a 190 selective, alcohols 157 Magnus’ green salt, derivatives 91 glyoxal 169 Pd, Pt complexes 117 wet air, of aniline 154 pgm chalcogenides 16 Oxygen, by photocatalytic decomposition, of H2O16pgm complexes 101 2+ dissolved, sensor, a 81 Ru(tpy)2 complexes 168 reduction, in DMFCs, a 192 Photoreactions, in alkane oxidation 71 PtCl4, in CHCl3, a 80 Palladium, coating, on Mg2Ni–C, for H2 sorption, a 39 Photoreduction, H2O 157 colloids 62, 191 Photosensitisers, Ru complexes 80, 81, 157 membranes, based upon polyacrylic acid, a 39 Photovoltaic Cells 12, 168 nanoparticles 39, 64, 191 Piezochromism, Pd, Pt complexes 117 ohmic contacts 16, 83 Plating, with Ir, Os, Pt-Ir, Rh, Ru 59 Pd + SnO2, Pd + ZnO, gas sensing 65 Platinum, capacitors, a 142 Pd/porous Si, in H2 detection 132 Co/Pt multilayer, magnetic nanostructures 15 Pd/ZnSe 16 CoPt/Pt multilayer nanowire arrays, a 142 thin films 64 dispersion strengthened, -Al2O3, wire 47 Palladium Alloys, dental, porcelain 30 electrodes, see Electrodes nanoparticles 140, 169 fabric, fibre, manufacture, uses 56 Ni-Pd, surface and bulk, a 38 ferromagnetism, in coins, nuggets 66 Pd-Cu foils, H permeance, a 190 nanoparticles 141, 154, 169 Pd-Cu-Ag, electrical, mechanical properties 3, 78 Pt + SnO2, Pt + ZnO, gas sensing 65 Pd-Cu-Au, Cu-Pd, Cu-Pd-Ni 3 Pt-Al2O3 composite, mechanical properties 47 Pd-Fe, dispersed in C, method 168 Pt-Al2O3 crucibles 47 Pt-Pd, nanoalloy clusters, a 140 Pt/CdTe, Pt/ZnSe 16 shape memory effect, Fe7Pd3, stabilisation, a 79 roubles 66, 72, 134 Palladium Complexes, C60Pd films, a 140 thermocouples 88, 145 with P-N ligands, P-O ligands, a 140 thin films, a 39, 83 Pd acetylacetonate, for Pd thin film deposition 64 Platinum Alloys, Au-Pt electrodes, a 190 Pd dendrimers 64 CoPt/Pt, multilayer nanowire arrays, a 142 Pd N,N-dimethylaminoalkyl chalcogenolates 116 Fe100–xPtx thin films, by magnetron sputtering, a 39 Pd ions, extraction, using Pd ion imprinted polymer 29 FePt3 films, ferromagnetism, a 38 [Pd2Cl2(dppm)2], reaction with benzoyl azides, a 190 nanoparticles, FePt, a 38 [Pd2Cl2(µ-NC(O)Ar)(dppm)2], synthesis, a 190 Pt–Al–Ir–Nb, Pt–Al–Nb, a 79 [PdCl(ECH2CH2NMe2)(PR3)], E = S, Se, Te 116 Pt-Fe, magnetism 66 Pd(II)–dimethylglyoxime–4-vinylpyridine 29 Pt-Ir, electrodeposition, book review 59 PdII diphenyldiphosphinites, preparation, a 140 Pt-Pd, nanoalloy clusters, a 140 Pd(II) diselenolenes containing tertiary phosphines 116 Pt3Al phase, L12 structure, a 79 Pd(II) porphyrins, reaction with amines 79 PtAl, Pt5Al3, a 38 for peptide hydrolysis 64 PtRu, mesoporous microspheres, a 141 photodynamic therapy 101 thermocouples 88, 145 piezochromism, [Pd(dmg)2], [Pd(NH3)2Br3], Platinum Complexes, anticancer drugs 101 2– 2– [Pd(niox)2], [Pd(SCN)4] , [Pd(SeCN)4] 117 arylfluoro, synthesis, a 79 precursors, for Pd chalcogenides 16 mononuclear, dinuclear, trinuclear, DNA interaction 101 with Se ligands, Te ligands 116 phosphorescence, a 38, 81 Palladium Compounds, Pd(II), hydrometallurgy 101 photodynamic therapy 101 2– 2– Pd chloride, for plating 63 piezochromism, [Pt(dmg)2], [Pt(SCN)4] , [Pt(SeCN)4] 117 reduction 168 with P-N ligands, P-O ligands, a 140 UV-photoactivation, a 191 Pt N,N-dimethylaminoalkyl chalcogenolates 116 Pd oxide (from PdCl2), sensitiser layer, on ZnO 65 Pt selenaketocarbenes 116 Pd sulfide, in light image receiving 16 [PtCl(ECH2CH2NMe2)(PR3)], E = S, Se, Te 116 + + lithographic films, plates; photographic films 16 [Pt(dien)N] , gas phase; [Pt(dien)3] , crystal structure, a 79 nanocrystals; particles, aqueous dispersions 16 [Pt(GeMe3)(SnMe3)(PMe2Ph)2], synthesis, a 190 in polymers, for semiconductors, solar cells 16 trans-[PtH(1-azolyl)(PEt3)2], trans-[PtH(R)(PEt3)2], a 140 II Pd4S, PdS2, Pd4Se, Pd17Se15, PdTe, synthesis 16 Pt diphenyldiphosphinites, preparation, a 140 precursors, for Pd colloids 62 Pt(II) diselenolenes containing tertiary phosphines 116 Patents 41–43, 84–87, 143–144, 193–194 Pt(IV), ligand reactions; reduction 64 Peptides, hydrolysis, using Pd(II) complexes 64 [Pt{S2CNMe(c-Hex)}2], precursor for MOCVD 16 Petrochemistry, by catalysis 180 with Se ligands, Te ligands 116

Platinum Metals Rev., 2004, 48, (4) 203 Page Page

n+ Platinum Compounds, chloroplatinic acid, for catalysts 63 Ruthenium Complexes, [(bpy)2Ru(µ-L)Ru(bpy)2] 157 H2PtCl4, H2PtCl6, by photohydrochlorination, a 80 [Cp*RuCl(µ-YMe)]2, preparation 116 H2PtCl6 + RuCl3, electrochemical co-reduction, a 141 H2O photoreduction 157 Magnus’ green salt, derivatives, synthesis, structure 91 KRux[Fe(CN)6]y, KxRuy[Ir(CN)6]z, KRux[Ru(CN)6]y 159 circular dichroism 91 luminescence 80, 168, 191 fibres, films, for “plastic electronics” 91 oxidation states, high, low 157 Magnus’ pink salt, synthesis 91 photosensitisers 80, 81, 157 Pt(II), Pt(IV), hydrometallurgy 101 precursors, for Ru colloids 62 PtCl4, photohydrochlorination, a 80 Ru-based hexacyanometallates, films, a 39 2+ PtNx films, by reactive laser ablation, a 141 [Ru(bpy)3] 157 5 [Pt(NH2dmoc)4][PtCl4], in field effect transistors 91 Ru(η -C60Me5)Cl(CO)2+CpNa, metathetical coupling, a 79 5 5 [Pt(NH2R4)][PtCl4], [Pt(NH3)4][PtCl4]91Ru(η -C60Me5)(η -C5H5), synthesis, reactivity, a 79 [Pt(NH3)4][PtI4], crystal structure, a 190 Ru(II), bridged, preparation, a 191 PtS, in light image receiving; nanocrystals 16 Ru(II) + heterocyclic N ligands 157 PtS2, nanoclusters 16 Ru-N ligand complexes, optical properties 101 Platinum Group Elements, Africa, South Africa, U.K. 139 Ru(II) polypyridyl+poly(ε-caprolactone)-bipyridine, a 190 Platinum Group Metals, chemicals, selling prices 15 ruthenocene, precursor for MOCVD 16 recovery, from sulfide ores, flotation concentrate 125 Ru(VI) oxo, Ru(VI) polypyridyls 157 salts, commercial uses 63 with Se ligands, Te ligands 116 Pollution Control, by catalysis 180 solar cells 81, 101, 141, 168 Polymerisation, co-, alkenes + CO 101 Ruthenium Compounds, CaRuO3 crystal, magnetism, a 190 electro-, C60Pd films, a 140 electrodes, a 80 ethylene 101 electrolytes, book review 59 Polymers, for encapsulation, of Pt octaethylporphyrin, a 81 Ru chalcogenides, synthesis, applications 16 imprinted, with Pd ion 29 Ru trichloride, for plating applications 63 with Ir(ppy)3, phosphorescence, a 140 RuCl3, + H2PtCl6, electrochemical co-reduction, a 141 with Pd sulfide 16 Ru(III)Cl3, for electrodeposition of RuO2, a 191 polynorbornene, by ROMP 148 RuO2 thin films, electrodeposition, a 191 polyvinylpyrrolidone, in stabilisation, of Pd colloids 62 Sr4Ru3O10, specific heat, a 79 Precipitation, Ir, Rh, Ru salts, (NH3)2PdCl2, (NH4)2PtCl6 125 Proline, in catalysis 104 Selective Catalytic Reduction, NO, a 192 Prolinol, in catalysis, a 82 Semiconductors, Pd sulfide, in polymers 16 Pyridines, hydrogenation 16 Sensors, glucose, a 80 Pyrocatechol, electrocatalysis, a 80 H2 132 hydrocarbons, a 141 Quinolines, hydrodenitrogenation 16 LPG 65 lubricants 58 α ω RCM, , -dienes, diethyl diallylmalonate 148 NH3, a 141 Reactors, plasma, a 39, 81 O2, dissolved, a 81 fluidised bed, VAM production 169 pH, a 81 Recovery, pgms, from sulfide ores 125 Shape Memory Effect, Fe7Pd3, a 79 Reduction, CeO2, M/CeO2 105 Sila-Sonogashira Couplings, a 192 co-, electrochemical, H2PtCl6 + RuCl3, a 141 Solar Cells 16, 81, 101, 141, 168 – IO3 159 Sonochemistry, in asymmetric hydogenation 104 NO 39, 70, 169 Sonogashira Couplings, addition of an inhibitor, a 142 NOx 70 palladacycle catalysts, a 192 O, in DMFCs, a 192 Spiro[3.5]nonane-6,8-dione, synthesis, a 82 PdCl2 168 Sputtering, DC magnetron, coatings, Ir-Ta, a 191 Pt(IV) 64 Stille Couplings, palladacycle catalysts, a 192 using Rh complexes 101 Sulfur, in engine oils 44 Refining, oil, by catalysis 180 Sulfur Oxides, SO2, NO reduction with CO, a 39 Reforming, autothermal, EtOH, EtOH-H2O, a 81 Suzuki Couplings, Pd perovskites 15 bifunctional catalysts 180 Suzuki-Miyaura Couplings, palladacycle catalysts, a 192 biomass 154 H2 generation, for fuel cells 32 Thermocouples, Pt, RhPt 88, 145 steam, of acetic acid 154 Rh drift 145 Resveratrol, synthesis, a 141 Thin Films, Au/BaTiO3/Pt, capacitors 142 Rhodium, electrodeposition, book review 59 Cr/Pt, by pulse laser deposition, a 83 isotopes, in medicine 101 Fe100–xPtx, by magnetron sputtering, a 39 Rhodium Alloys, thermocouples 88, 145 Ir-based hexacyanometallates 159 Rhodium Complexes, H2O-soluble, + cyclodextrins, a 38 Pd, deposition, using Pd acetylacetonate 64 Kx–1RhyFe[Ir(CN)6]z, modification of GCE 159 PdS, PtS, RuS2, by MOCVD 16 photodynamic therapy 101 RuO2, electrodeposition, a 191 Rh(III) cyclometallates, S and Se donor ligands, a 190 ultra-, Pt, by cathodic-arc deposition, a 39 Rh phthalocyanine, Cl2 exposure, a 140 Three-Way Catalysts, alternatives 70 Rhodium Compounds, electrolytes, book review 59 book review 180 Rh chalcogenides, synthesis, applications 16 Transistors, field effect, [Pt(NH2dmoc)4][PtCl4] layer 91 Rh trichloride, for catalysts, plating applications 63 ROMP 101, 148 Ullmann-Type Couplings, palladacycle catalysts, a 192 Roubles, Pt 66, 72, 134 Ruthenium, colloids, stabilised in polymer 62 Vinyl Acetate, monomer, production 169 electrodeposition, book review 59 electrodes 63 Water, decomposition, by photocatalysis 16 Ruthenium Alloys, PtRu, mesoporous microspheres, a 141 photoreduction 157 Ru-Al-Mo, mechanical properties, microstructure, a 79 Water Gas Shift Reaction, Au/pgm catalysts 169

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