Platinum Metals Review

UK ISSN 0032-1400

PLATINUM METALS REVIEW

A quarterly survey of research on the platinum metals and of developments in their application in industry www.matthey.com and www.turpin-distribution.com

VOL. 43 JULY 1999 NO. 3 Contents

The Oxidation of Alcohols to Aldehydes or Ketones 94 By Holger B. Friedrich Ruthenium in Living Radical Polymerisation 102 Developments in Cisplatin Research 103 By Simon P. Fricker Thin-Film Light-Emitting Ruthenium(I1) Devices 104 Organometallic Chemistry and Applied Catalysis 105 By Berth-Jan Deelman Sonochemical Platinum Reduction 108 Catalyst Enhanced Oxidation of VOCs and Methane in Cold-Plasma Reactors 109 By Muhammad ArifMalik and Salman Akbar Malik Encapsulation of Platinum in Dendrimers 113 Combined Homogeneous and Heterogeneous Catalysts 114 By David T. Thompson The Effects of Hydrogen on the Physical Properties of Palladium 116 By V. A. Goltsov “Platinum 1999” 118 Aftertreatment for Low Emission Vehicles 119 ByM. V. Twigg Johann Wolfgang Dobereiner’s Feuerzeug 122 By Professor George B. Kaufian Noble and Rare Metals: NRM-2000 128 Abstracts 129 New Patents 134

Communications should be addressed to The Editor, Susan V.Ashton, PIatinum Metals Review, [email protected] Johnson Matthey Public Limited Company, Hatton Garden, London ECI N 8EE The Oxidation of Alcohols to Aldehydes or Ketones HIGH OXIDATION STATE RUTHENIUM COMPOUNDS AS CATALYSTS By Holger B. Friedrich School of Pure &- Applied Chemistry, University of Natal, South Africa

The oxidations of alcohols to aldehydes and ketones are vital reurliuns in synthetic organic chemistry, and high selectivity and mild conditions are important prerequisites for ease of product work-up and lower cost. Currentl-y, many of the best oxidants for these conversions contain high valent ruthenium, with ruthenium acting as a catalyst for these reactions. It is important to have detailed knowledge and understanding of the mechanisms of the oxidation reactions and the factors that injluence them, as only by completely understanding how these proresses work will it be possible to design better or optimal catalysts. In this paper, the more viable oxidants currently available are reported and some investigations into the mechanisms of the reartions and factors affecting them are discussed.

As the catalytic conversions of primary alco- remove by-products, are difficult to separate hols into aldehydes and of secondary alcohols from the product after the reaction is over, into ketones are essential for the preparation require acidic conditions which limit the choice of many key synthetic intermediates in organic of substrate, or, they do not give complete con- chemistry, there is currently much activity being versions in all applications. Thus, there is clearly undertaken in the search for catalytic systems a need to prepare milder and more selective oxi- which can perform these operations. dants with higher rates of conversion. Several oxidative systems which at least partially fit oxidant RCHiOH A RCHO (0 the above criteria have recently been reported, oxidant and many of these contain or are based on RCH(0H)R’A RC(0)R’ (ii) ruthenium. In particular, the reaction shown in Equation The chemistry of high-oxidation-state ruthe- (i) does not usually stop at the formation of nium is less well developed than that of, for the aldehyde and over-oxidation to the carboxylic example, osmium (4) or rhenium (5). acid often occurs. Specifically, reaction mechanisms and the fac- H30 tors which influence the performance of vari- RCHO ,RCOOH (iii) ous oxidants are poorly understood. It is clear, Historically, various oxidative systems have however, that several of the high valent 0x0 been available for these reactions, including ruthenium compounds made so far are active chromium(V1) 0x0 compounds, copper in transforming both primary alcohols into alde- chromites (often used industrially for bulk prepa- hydes and secondary alcohols into ketones. rations), vanadium pentoxide, PtO,, While many compounds will cause these trans- RuCl,/Cu(II) (1, 2) and the Swern oxidation formations, few do so catalytically and this may (3).However, there are various drawbacks to be ruthenium’s strength. Many of the known using these reagents; for instance, they are either ruthenium-containing oxidants are also toler- rather aggressive, need relatively high or low ant of other sensitive hctional groups in organic temperatures, give unwanted and difficult to molecules. It would be desirable to have a very

l’latinuwi Metals Rev., 1999, 43, (3), 94-102 94 selective catalytic oxidant, which would not (10). The acetic acid derivative was shown to attack other potentially reactive groups, such as be a good catalytic oxidant with MNO as co-oxi- double bonds, halides, epoxides, esters, amides, dant. No effects were observed on varying the or protecting groups, such as silyl or benzoate, length of the alkyl chain (R). It was felt that this amongst many others. Ideally, this catalytic oxi- system was worth further investigation and high dant would also operate at room temperature yield routes to the compounds, where R = Me, in an environmentally friendly solvent system CF,, C,,H,, C,F, and GH,,,were developed, (such as water) and use “green” co-oxidants which avoided the need to use RuO, gas. The such as oxygen (OJ or hydrogen peroxide compounds were found to be stable and cat- (H202).This ideal catalytic oxidant should also alytically active with a wide range of co-oxidants be easy to recycle. Designing such systems (H20,, NaOCI, ‘BuOOH {tertiary-butyl remains a challenge, although significant hydroperoxide)) with MNO and tetrabutylam- progress is being made. Other factors which monium periodate being the best, amongst oth- influence the acceptance of new catalysts include ers. Fluorinated compounds often display very the ease of operation and the ease of (synthet- different properties to their protonated ana- ically or commercially) producing the catalyst. logues, probably because fluorine and hydrogen, although being of similar size, have very Ruthenium Oxide Catalyst Systems different electronegativities. However, we found The only known well-defined stable ruthe- that apart from significantly affecting the syn- nium(VII1) compound is ruthenium tetroxide, thetic yields of the oxidants, no effect on the RuO,, which is frequently far too vigorous an oxidations was observed. oxidant, as it attacks many functional groups, The most well-known ruthenium oxide cata- such as double bonds, and often forms car- lyst, tetrapropylammonium perruthenate boxylic acids. Consequently, research has (TPAP) and its sister tetrabutylammonium per- focused on ruthenium compounds in slightly ruthenate (TBAP) are effective in many selec- lower oxidation states. tive organic transformations of the type sum- “Catalytic” systems reported in the literature marised in Equations (i) and (ii) using MNO with reasonably high selectivities, conversions as the co-oxidant. A comprehensive review has (depending on substrates) and turnovers (mea- recently been published (1 1). TPAP is also sured as moles of product per mole of catalyst), almost the only ruthenium oxidation catalyst to are [Ru,0,(py),].3.5HI0 (py = pyridine), have been studied kinetically. The reaction of truns-[4-‘Bu-Hpy] [RuOlC1,(4-‘Bu-py)] (Hpy is TPAP with propan-2-01 was found to be auto- a protonated pyridine), [LPh,] [RuO,Cl,] (L = catalytic, possibly due to the formation of col- P, As) and truns-[Ru02(py),] [BF,]>, all having loidal RuOzwhich may form RuO,mRuO, (12). 4-methylmorpholine N-oxide, MNO, as co-oxi- TPAP is a three-electron oxidant overall, but dant (6-8). These compounds are obtained in it is believed that the alcohol oxidation step is moderate yield, and the first two are made by of the two-electron type. The fact that TPAP utilising RuO, as a gas, and require appropriate will oxidise cyclobutanol to cyclobutanone sug- manipulative and experimental skills. The di- gests that a one-electron oxidation process is nuclear compound also appears to have a lim- not involved, since a one-electron oxidant would ited “shelf-life”. cleave cyclobutanol to acyclic products (1 3). A series of compounds, which appear to have Other reported ruthenium(V1) oxidants will considerable potential as viable catalytic usually convert primary alcohols into acids, oxidants are the compounds cis-[PPh,]- although internal alcohols will still be converted [RuO,Cl,(OCOR)] (R = Me, Et, Pr, CHF,), into ketones. Compounds reported to effect (9). The cis-0x0 arrangement is unusual because these transformations are K[RuO,] and [RuO,]’ of the considerable electronic stabilisation asso- (really tr~ns-[RuO,(OH)~]’) (7, 14, 15). The ciated with the trans-dioxo, d’, configuration yields range from moderate to good, depending

Platinum Metals Rev., 1999, 43, (3) 95 0 Fig. 1 The proposed ester intermediate in ruthcuiuni oxide catalysed n ‘c=o/ 1 reactions

on the substrate. Conversions are carried out in primary alcohols), but the conversions are basic aqueous media, as ruthenate and per- generally low. ruthenate are unstable at lower pH. This lim- Alcohol oxidations with transition metal 0x0 its the reagents to substrates which are stable at reagents probably mainly involve the same basic high pH. The reactions are rendered catalytic transformation as shown in Figure 1, involv- by using K&OR (persulfate) or BrO; (bromate) ing an ester intermediate. For all of the catalytic as the co-oxidant. Similar results are attained oxidants mentioned above, primary alcohols in the same media using tr~ns-[RuO,(HI0,)~]~ react more rapidly than secondary alcohols, as catalyst, with NaIO, as the co-oxidant (16). probably due to steric hindrance of secondary Even ruthenium tetroxide, RuO,, has been alcohols. It is generally thought that the reagents, reported as oxidising secondary alcohols to reported above, which effectively catalyse the ketones (1, 17). However, both RuO, and reaction in Equation (i), do so because of the sodium ruthenate are known to attack double presence of molecular sieves in the reaction bonds, although sodium ruthenate will do so medium. The molecular sieves efficiently remove only if high temperatures or longer reaction times water (formed in the reaction and present as are employed ( 18, 19). Since RuO, is unstable water of crystallisation of MNO). It is known at pH > 8, the active species in those reactions that an aldehyde hydrate is necessary for the reported to involve RuO, and NaOCl is prob- reaction in Equation (iii) to occur. The mech- ably RuO,-, see Equation (iv) (20). anism for the oxidation by chromic acid of an aldehyde is shown in Figure 2 (22) and 4Ru0, + 40H + 4Ru0, + 2H,O + O2 (iv) ruthenium oxide oxidations are presumed to At high pH (> 12) though, ruthenate is the be similar. Some preliminary results from our dominant species:

4Ru0, + 40H + 4“RuO,”’+ 2H20+ 0, (v) The compound [Ru02(tetramesitylporphyri- nato)] has been reported to oxidise alkyl alcohols to ketones, although its primary application is as an alkane oxidant (2 1). Strictly speaking, few of the above mentioned PH ruthenium catalysts are true catalysts, since if the “catalytic” reactions are carried out with too little co-oxidant, the ruthenium compound remains in a reduced state. A catalyst should be unchanged after a reaction. Instead, the ruthenium 0x0 compounds are really primary oxidants, that is, they directly oxidise the substrate. RCOiH I Cr(lV) The co-oxidant is the secondary oxidant - which regenerates the primary oxidant. A few of the Fig. 2 The mechanism for the chromic acid catalysed oxidation of an aldehyde. This is commonly used secondary oxidants do react similar to oxidations using ruthenium oxide directly with alcohols (for example, MNO with

Plarinunt Metals Rev., 1999, 43, (3) 96 OH OH I I H-CRz

0 =Ru0;-

RzC=O + HzO Fig. 3 Proposed mechanism for the oxidation of propan-2-01by ruthenate and perruthenate

laboratory, however, imply that the presence of ruthenium salts add to an a-C-Hbond of the water in the reaction medium does not neces- alcohol. The proposed mechanism is shown in sarily mean that the reaction in Equation (iii) Figure 3. Since HRu0,'- is very reactive, it is will proceed. believed that a single electron transfer would The stoichiometric oxidations of propan-2-01 occur very rapidly, before the radical could dif- with the sodium salts of ruthenate and per- fuse out of the solvent cage. For the stoichio- ruthenate have been investigated kinetically and metric oxidation of propan-2-01 with per- mechanistically (23). Both reactions are believed ruthenate, as shown in Figure 3, it is thought to proceed via free radical-like transition states, likely that because the HRuO, ion is less reac- although the subsequent steps differ. For both tive, the product would move out of the solvent ruthenate and perruthenate, an ester interme- cage before further reaction. These proposed diate, as shown in Figure 1, is thought to mechanisms fit theoretical predictions (24). be unlikely and instead it is assumed that the The reactions of [RuOJ and [Ru04]' with

fast doH. RuOc - &iz~~z~~z~~~RUO:- fast CH~CH~CH~CHO. RUO~ - CHz=CHCHzCHO f RU0:-

2- CH~=CHCH~CHO . R~O,, - CH~=CHCH~~-+ RuOZ

doH- RuO:- do + RuOz

Fig. 4 Proposed mechanism for the one- and two-electron oxidation of eyclobutanol

Platinum Metals Rev., 1999, 43, (3) 97 Na MeC6H4S02N ’ . HzO 5 MeCgHLSO2N/H + NaOH CI ‘Cl

slow 11 RuOJ

0 II ,H MeCgHL- 5 - N, / ’., 2- propanol .c I MelCO MeC6H4SOZNH2 R””’ * o., ,

Fig. 5 Proposed mechanism for the activation of rutlienate 11y chloraniine-T, prior to the I oxidation of propan-2-01 cyclobutanol suggest that the latter is a nvo-elec- tract. Apart from this, even the best known tron and the former, unlike TPAP, is a one- catalysts do not give quantitative or almost-quan- electron oxidant, see Figure 4 (25). titative transformations in all apparently suit- The mechanisms of the catalytic oxidations of able systems and, as such, there is a great need propan-2-01 using [RuO,]’ with a variety of to develop more effective and more selective co-oxidants have also been investigated. For the catalysts with higher turnovers. co-oxidants hexacyanoferrate(III), diperioda- In general, the activity of catalysts is affected tocuprate(II1) and periodate, the data imply that by the steric bulk (for instance, cone angles) a complex is formed, as for the stoichiometric of the attached groups and the electron density oxidation, Figure 3. The role of the co-oxidant on the metal. The significant effect of the groups is only to regenerate Ru(V1). The exception is attached to the Ru(V1) centre is demonstrated when the co-oxidant is chloramine-T. In this by the examples of Ru(VI)O, moieties bonded case, the co-oxidant appears to react directly to porphyrins or to other bulky tetradentate lig- with the Ru(V1) ion, see Figure 5. This active ands: many of these compounds are effective complex then reacts rapidly with propan-2-01 catalysts for the epoxidation of olefins (27). to form acetone (26). It seems very likely, how- None of the other ruthenium(V1) 0x0 catalysts, ever, that these mechanisms are only valid in referred to above, can perform this reaction. aqueous base and the mechanisms are proba- However, even Ru(VI)02 compounds, with bly different in non-aqueous media, as shown, bulky bidentate ligands, can catalyse epoxida- for example, by the different reaction prod- tion reactions (28). ucts obtained in the oxidation of cyclobutanol with TPAP and basic perruthenate. Towards Commercial Catalysts The disadvantages of many of the catalysts As part of a project to develop commercially that catalyse the reaction in Equation (i) and viable catalysts for the oxidation of alcohols, we also of several which efficiently catalyse the reac- are interested in determining how various sub- tion in Equation (ii) are that they require CHZC12 stituents affect the chemistry of ruthenium(V1) or CHCN as solvents (which are not “green”) 0x0 compounds. One potential route would and that they require MNO as co-oxidant. involve the synthesis of organometallic ruthe- However, the MNO co-oxidant is expensive, an nium(V1) 0x0 compounds. The possibility of irritant to the eyes, the respiratory system and being able to vary and fine-tune a wide range of the skin, and its final product, 4-methyl mor- alkyl or aryl substituents should offer much infor- pholine, is corrosive and causes burns to the mation on these systems and facilitate the design skin, the eyes and mucous layers in the nasal of highly specific catalysts. However, only a few

Platinum Metah Rev., 1999, 43, (3) 98 (a) (b)

arb- Br6-

"c6'06- 6;TBr6-

6- -"6

*CF Ob- 6.

(C 1 (d)

Fig. 6 Loealised relative charges on (a) 3-Br-pyridine and (b) 4-Br-pyridine and the resulting relative charge distribution in the complexes they constitute (c) and (d), respectively

mono-oxo ruthenium(V1) organometallic com- hence on the ruthenium centre. These effects pounds are known (29) and ruthenium(V1) should be revealed by changes in the Ru=O organometallic di-oxo compounds have so far stretching vibrations. This is confirmed by exam- proved to be totally elusive. ining the IR spectra of these compounds. Alternatively, one can study the effects of substituents in inorganic ruthenium 0x0 compounds. This latter approach has the advantage that routes to discreet, fully characterisable com- 3-COOH pounds of this type are already available. The first system to be considered consisted of compounds of the type [RuO,Clz(Y-py),] (Y = 850 H, 4-'Bu, 3-CN, 4-CN, 2-Br, 3-Br, 4-Br, 4-C1, 6 848 4-Me, 4-C(0)C,H5, 3-COOH, 4-COOH). This 6 II 846- series was chosen because we thought that sub- -z stituents on a flat aromatic ring, for which 3 844 - Hammett substituent constants were available, 842 - should show easily quantifiable electronic effects on the ruthenium centre. The first examples 840 - of compounds in this series Cy = H, 4-'Bu, 4-C1) 838 - were prepared by Griffith and co-workers (6) -2 -1 0 1 2 3 and the rest by us (30). As can be seen from o*

Figure 6, substitution at either the 3- or 4-posi- Fig. 7 A plot of v(Ku=O) values against O* for tion of the pyridine ring should have a signifi- the compounds [RuO,CI,(Y-~~)~];O* is a cant effect on the charge on the pyridine nitro- descriptionof the substituents. The magnitude gen and consequently on the net charge on the of O* gives the relative strength of the electron- withdrawing or electrotdonating properties ruthenium centre. of the substituents. The value of O* is positive Similarly, the nature of the substituent Y (either if the substituent is electron-withdrawingand electron pushing or electron withdrawing) should negative if it is electron-donating affect the charge on the pyridine nitrogen and

I'(atinum Metals Rev., 1999, 43, (3) 99 Stoichiometric and *Catalytic Oxiclatioiis of I-Hexaiiol to Hexaiial by (Y)O,CI,Ru with a Range of Co-catalysts, over a 24-hour period

Substituted ;toichiometric Co-catalvsts. O/O conversion Characteristic pyridine (Y) oxidations v(Ru-0). cm *H20, “NaOCI “‘BuOOH “MNO

39 15 13 12 22 842.4(vs) 34 8 9 9 14 842.7( m) 38 10 11 10 16 840(vs); 831(s) 84 15 47 39 54 826(s) 63 45 85 55 97 848(vs); 817.7(s) 59 36 64 51 99 841 .I(vs) 50 - 65 - 96 840.5(vs) - 45 - 65 849.3m)

50 - ~ ~ ~ 837.5(vs) 63 13 17 15 23 839(vs) 7 6 6 5 16 845.5ivs)

~ - - - 843.7(vs); 830.9(s)

31 - ~ ~ ~ 840.8(s)

~ ~ ~ ~ 853(s)

- - ~ ~ 841.5(m)

All runs wero icpeated at ledst three ;lines and are reprodiicihie ni ~ niediurn. s ~ strong, vs = vcry strong

Excluding the compound where Y = H, the observed for the “catalytic” oxidations, using v(Ru=O) stretches correlate linearly with the H,O,, hypochlorite (OC1) or t-butyl hydroper- Hammett, o,,and Taft, o*,values, see Figure oxide ((CH,)COOH) as the co-oxidants. 7, and Pauling type electronegativity (X) values Although the Y substituents clearly affect the of the Y substituents. Since these values are due v(Ru=O) values and hence the strength of the to an inductive effect, one would expect the Ru=O bond and the electron density on the inductive effect to increase with decreasing dis- metal, no correlation between oxidising ability tance between the substituent, Y, and the ruthe- and substituent constants for Y is observed. This nium centre. This is observed, with the slope implies that electron density on the metal of the graph for the 3-substituted compounds has no significant effect on these compounds as being much steeper than for the 4-substituted oxidants. compounds. In addition, electronic effects do not appear Thus, these complexes are stoichiometric and to play a role in the performance of the Ru(V1) “catalytic” oxidants for the conversion of alco- salts, [PPh,] [Ru02C12(0COR)],as reported hols to aldehydes, with the substituents, Y, clearly above. While most of the above compounds are affecting the performance of the compounds. mediocre oxidants, the performance of The Table shows values for stoichiometric oxi- [RuOZC1,(4-Br-py),]is exceptional and so is that dations of 1-hexanol to hexanal by (Y)0,Cl2Ru of [RuOzC12(3-Br-py)J,to a lesser extent. Both with a range of co-catalysts. of these are far superior oxidants to any of the A sequence was observed of the oxidising abil- other compounds in this series. The 4-Br-pyri- ity for the stoichiometric oxidations: phen < dine derivative gives especially high rates of con- 4-Me-py < benzoyl-py < 3-CN-py < 4-CN-py version with reasonable turnovers. We are at < 4-IBu-p~< 4-C1-pyz py -= 3-Br-py= 4-Br-py present investigating this clear ligand effect. < bipy. An almost identical sequence was A study of the compounds [Ru02C1,L] (L =

Plutiirrmr Metals Rev., 1999, 43, (3) 100 bipyridyl, 1,lO-phenanthroline) indicates that to a +6 oxidation state within the Brucite, the rigidity of the ligands may also play a role, Mg(OH)?, layer. as the bipyridyl compound is a reasonable oxi- The use of oxygen as co-oxidant, as in the sys- dant, whereas the phenanthroline compound is tem mentioned above, is very advantageous kom a very poor oxidant, as shown in the Table. an environmental point of view. We have car- One of the great disadvantages of many homo- ried out extensive studies on various co-oxidants geneous catalytic systems is the problem of sep- for the catalysts [RUO~C~~(Y-~~)~],[PPh,]- arating the product from the catalyst. For this [RuO,Cl,(OCOR)] and polymer or zeolite “sup- reason heterogeneous catalysts remain very pop- ported” ruthenate. While these systems are active ular, as the catalyst can simply be filtered off for a wide range of co-oxidants, consistently, and reused. highest conversions for these systems and many One way of attempting to combine the advan- of those reported above, are usually obtained tages of homogeneous and heterogeneous cat- using MNO, although tetrabutyl-ammonium alysts is by bonding soluble catalysts to insolu- periodate appears to be an excellent co-oxidant ble supports, although these have yet to attain for the immobilised systems and also for the oxi- a large scale industrial breakthrough (31). We dation of primary alcohols with the salts have supported ruthenate on poly-(4-vinylpyri- [PPh,] [RuO?Cl2(0COR)](R = CF1, C,H, and dine) and on zeolite-Y. Both these supported C,F,). catalysts appear to be very selective in the oxidations referred to in Equations (i) and (ii), with Concluding Remarks a wide range of co-oxidants at room tempera- Thus, it would seem that high oxidation state ture (32). The catalysts can be filtered off and ruthenium catalysts are amongst the best mild reused. We are currently investigating both the oxidants for the oxidation of alcohols, with little structures and the versatility of these catalysts. or no over-oxidation products being obtained. We believe that the ruthenate may be bonded Our information remains limited on the mech- to the polymer, as is the OsO4/poly-(4-vinylppi- anism of the reactions and on which factors, dine) system for oxidising alkenes to diols, rather besides having ruthenium in a high oxidation than just being supported (33). state, influence the efficiency of these compounds. A ruthenium hydrotalcite heterogeneous com- Our best hope of discovering what influences the petitor has recently been reported (34). This oxidation chemistry of ruthenium will come kom catalyst is reported to oxidise primary and sec- using homogeneous catalytic systems, although ondary alcohols into aldehydes and ketones, environmental and economic concerns may respectively, in high yields with high selectivity. ultimately favour supported, heterogeneous or This catalyst appears to be easily prepared and genuinely two-phase catalytic systems. the oxidations take place at 60°C in toluene, using molecular oxygen as co-oxidant. It would Acknowledgement appear that a heteronuclear interaction between Thanks to the Alexander von Humboldt Foundation, NMT Electrodes, Western Platinum Refineries, the ruthenium and cobalt is responsible for the high University of Natal and the Foundation for Research activity, with ruthenium probably being oxidised Development for their support; also to Vikash Gokul.

References 1 R. A. Sheldon and J. K. Kochi, “Metal Catalysed 5 A. Gansauer, Angew. Chem. Inr. Ed., 1997, 36, Oxidations of Organic Comoounds”. Academic 259 1 and references therein Press, New York,l981 2 K, Bowden, 1. M. Heilbron, E, R. H. Jones and A. c. A. M. E1-Hendawy, w. Grifith, C. A. O’Mahoney and D. J. Williams, Chem. B. C. L. Weedon,J. Chem. SOC.,1946, 39 3. SOC.,Dalton Trans., 1990, 737 3 A. J. Mancuso and D. Swern, Synthesis, 1981, 165 4 T. Gobel and K. B. Sharpless, Angew. Chem. Int. 7 A. M. El-Hendawy, W. P. Grifith, F. I. Taha and Ed., 1997, 36, 2591 and references therein; M. M. N. Moussa,J Chem. SOC.,Dalton Trans., 1989, Schroder, Chem. Rev., 1980, 80, 187 90 1

Platinum Metals Rev., 1999, 43, (3) 101 8 G. Green, W. P. Griffith, D. M. Hollinshead, S. 2 1 H. Ohtake, T. Higuchi and M. Hirobe, J. Ani. V. Ley and M. Schroedcr, J. Cliein. Sor., I’erkirr Chztrl. Soc., 1992, 114, 10660 Ems. I, 1984, 681; A. C. Dengel, W. P. Griffith, 22 J. RocekandC.-S.Ng,J Or$. Chern., 1973,38,3348 A. M. El-Hendawy and J. M. Jolliffe, l’iily/~edri~ii, 23 D. G. Ixe and I.. N. Congson, Chi. J. Cheni., 1990, 9, 1751 1990,68, 1774 9 W. P. Griffith, J. M. Jolliffe, S. V. Ley and I). J. 24 A. K. Rappt and W. A. Goddard III,J. AWLChenl. Williams, .7. Ckenr. Soc., Uteri/. Co~iiir/uir.,1990, SOL-.,1982, 104,448; 3287; K. Behari, N. Narayan, 12 19; W. P. Griffith and J. M. Jolliffe, J. Cheni. R. S. Shukla and I(. C. Gupta, hi. .7. Ch~.ni.Kinet., SUC.,Uulroir Trans., 1992, 3483 1984,16, 195 10 A. Dovletoglou, S. A. Adeyenii, M. H. Lynn, D. 25 D. G. I.ee, I.. N. Congson, U. A. Spitzer and M. J. Hodgson and T. J. Meyer, J. Ani. Chrwr. ISoc., E. Olson, Cuii. J. Cheni., 1984, 62, 1835 1990, 112, 8989 and references therein 26 T. V. L,alitha and B. Sethuram, Mcr. I1 S. V. Ley, J. Norman, W. P. Griffith and S. 1’. Transirion Chori., 1992, 17, 29 Marsden, S~~iirhesis,1994, 639 27 Z. Gross and S. Ini,J. Org. C,’heni., 1997,62, 5514; 12 D. G. Lee, Z. Wang and W. D. Chandler,.y. Org. C.-M. Che, C.-K. I.i, W.-T. Tang and W.-Y. Yu, Chein., 1992, 51, 3276 J. Chi/.SOC., DU/Zaluminium(II1) important technique in precision polymer syn- isopropoxide, Al(0z-Pr) ,, at 80°C (T. Nishikawa, thesis for the construction of new polymers with M. Kaniigaito and M. Sawamoto, Mucronzolecules, tailor-made structural complexities. In order to 1999, 32, (7), 2204-2209). assemble structurally well-defined polymers, in With ruthenium(I1)-initiation, living radical terms of molecular weights and molecular weight suspension polymerisation of MMA proceeded distributions, their polymerisation must be con- to give poly(MMA) with controlled high mol- trolled. However, the control of the reactivity ecular weights @,,) and narrow molecular weight of the propagating chain ends was difficult, until distributions (M>s/M,, = 1.1 to 1.3). In water, the recent discovery of living (controlled) rad- the PhCOCHCl,iKuCl1(PPhi), initiating sys- ical polymerisation. Due to its unique tolerance tem gave poly(MMA) of M,,- 10’ and M\\lmn - to water, radical polymerisation can be per- I. 1, even in the absence of Al(0i-Pr) $. formed as suspension, dispersion and emulsion Polymerisations were faster in water than in processes. organic solvents, such as toluene. The radical Most of these living radical polymerisations mechanism of the polymerisation was confirmed are based on transition metal catalysis (via and the high stabilities of the dormant carbon- reversible activation of a carbon-halogen ter- halogen terminal and of the ruthenium catalyst minal) or nitroxide-mediated processes. in water and alcohols were demonstrated. Recently, workers at Kyoto University, Japan, Ruthenium complexes are known to be weakly have examined the living radical suspension oxophilic and sometimes water tolerant. polymerisation of methyl methacrylate (MMA) This living radical suspension polymerisation in water and alcohols using RuCI,(PPh,) may also be used with other metal complexes catalystiactivator and an organic halide initia- or monomers and be applicable to the precision tor, such as PhCOCHCl, or CCI,Br, in the synthesis of block and random copolymers.

Plutiriurti Meruls RE?., 1999, 43, (3) 102 Developments in Cisplatin Research ~ Cisplatin: Chemistry and Biochemistry of a Leading Anticancer Drug EDITED BY BERNHARD LIPPERT, Wiley-VCH, Weinheim, 1999,563 pages, ISBN 3-906390-20-9, El05

It is 30 years since Barnett Rosenberg and his filings around a bar magnet. It was this unlikely colleagues published their seminal paper in coupling of ideas which gave rise to the exper- Nature entitled "Platinum compounds: a new iments that ultimately led to the discovery of class of potent antitumour agents" (1). This ini- the anticancer activity of platinum compounds. tial paper marked the beginning of what was Part 2, "Cisplatin - How Good is it?" by P. J. to become one of the most exciting uses of plat- O'Dwyer, J. I? Stevenson and S. W. Johnson, inum, and initiated international research efforts reviews the clinical use of platinum drugs. What in scientific fields as diverse as inorganic chem- is apparent &om reading this chapter is not only istry, cell and molecular biology, and oncology. the efficacy of the platinum drugs, but the wide The platinum drugs, cisplatin and carboplatin, range of cancers in which they are a component are still at the forefront of anticancer therapy, of the therapeutic regimen. One disappointing and there are four major new compounds aspect of this chapter is that it ends without a presently in clinical trials: JM2 16 being jointly concluding section and therefore does not developed by Johnson Matthey and Bristol answer the question posed in the title. Meyers Squibb, AnorMED's Ah4D473 being developed in collaboration with Zeneca, Biochemical Mechanisms and BBR3464 which is being developed by Roche- Chemical Interactions Boehringer Mannhein in collaboration with Part 3 consists of 4 chapters describing the its inventor, N. P. Farrell of Virginia efforts that have gone into understanding the Commonwealth University, and Sanofis oxali- biochemical mechanism of cisplatin. D. B. platin. Bernhard Lippert's excellent book reviews Zamble and S. J. Lippard describe the response the achievement, progress, and new develop- of cellular proteins to cisplatin-damaged DNA. ments in cisplatin research over the last thirty A group of proteins that recognise the cisplatin- years. DNA lesion, HMG proteins, appear to be asso- The book is divided into 6 Parts and contains ciated with enhanced sensitivity to cisplatin. 22 chapters, each written by current leaders Another protein of great interest is the prod- in the field. The international aspect of the uct of the p53 tumour suppressor gene. This research is demonstrated by the choice of authors is discussed both in this chapter and the sub- who come from Europe, the U.S.A. and Japan. sequent chapter by A. Eastman. Eastman dis- The length of the book precludes a discussion cusses the mechanism by which cisplatin-DNA of each individual chapter so selected highlights binding leads to cell death by apoptosis will be discussed. The choices are purely sub- (programmed cell death). jective and reflects the reviewer's own interests. Part 4 and Part 5 examine the chemistry of platinum compounds relevant to their anti- Discovery of Cisplatin tumour activity. R. B. Martin describes the rel- It is fitting that Part 1, "The Start", is a very evance of the hydrolysis of platinum complexes personal account of the discovery of cisplatin to their mechanism of action; Y. Chen, Z. Guo by Barnett Rosenberg. The account is one of and P. J. Sadler exploit NMR to examine the basic research and a physicist's fascination with interactions of platinum complexes with bio- the similarities between the physical appearance molecules. J. Reedijk and J. M. Teuben review of chromosomes during cell division and the platinum-sulfur interactions relevant to the bio- magnetic dipole field such as that seen with iron chemical mechanism of cisplatin. The reactions

Platinum Metals REV.,1999, 43, (3), 103-104 103 of platinum drugs with S-donor ligands are coming this mechanism of resistance. K. E. important for two reasons: [a] a mechanism of Sandman and S. J. Lippard address the prob- resistance to the platinum drugs is inactiva- lem of new drug discovery in the light of the tion resulting from the reaction with S-con- recent advances and application of combina- taining biomolecules such as glutatione and torial chemistry in drug discovery. They eval- methionine, and [b] thiol reagents can poten- uate novel screening methodologies for testing tially act as “rescue agents” to prevent some of libraries of platinum compounds. the toxicity of cisplatin. One of the striking aspects of this book is the The chapters in Part 5 illustrate how the dis- way in which personalities come through the covery of the pharmacological properties of cis- description of the science. This is at its best in platin have influenced the direction of co-ordi- the dedication at the end of the chapter by nation chemistry. Lippert takes a personal look Eastman in which he acknowledges the work of at the “platinum blues“, particularly those the late J. J. Roberts who was responsible for formed by the interaction of cisplatin and pyrim- much of the early fundamental research on the idine nucleobases. This theme is developed in biochemical mechanism of cisplatin. The dis- the following chapters, written by L. Randaccio covery of cisplatin has inspired many scientists and E. Zangrando; G. Natile, F. P. Intini and from diverse backgrounds and this is demon- C. Pacifico; and K. Matsumoto. strated throughout the many excellent reviews. Bernhard Lippert is to be congratulated on pro- New Developments ducing a book consisting not only of numerous The book ends with a description of new devel- scientific articles of high quality describing cur- opments. The first two chapters of Part 6 focus rent research, but also a book that conveys the on compounds in clinical trials. N. Farrell, Y. essence of scientific research. This book is rec- Qu, U. Bierbach, M. Valsecchi and E. Menta ommended to all those with an interest in plat- review the structure-activity relationships of di- inum chemistry, bioinorganic chemistry, bio- and trinuclear platinum compounds undergo- chemistry, and the clinical development of ing Phase I clinical trials. L. R. Kelland reviews platinum anticancer drugs, and is a good illus- the development of orally active platinum drugs tration of their significance. including JM216 and AMD473. The develop- SIMON I’. FRICKER ment of AMD473 takes up the theme of thiol Reference reactivity as this compound was designed to 1 B. Rosenberg, L. VanCamp, J. E. Trosko and have reduced reactivity with thiols, thereby over- V. H. Mansour, Nature, 1969, 222, 385 T hin-Film Light -Emitting Ruthenium( 11) Devices Solid-state light-emitting devices, based on brightness at low voltage, and no need of “charg- ruthenium(I1) complexes and operating at low ing” or reactive cathode materials (E. S. Handy, voltages, do not have the high brightness and effi- A. J. Pal and M. F. Rubner,J. Am. Chem. SOC., ciency of electrogenerated chemiluminescence 1999, 121, (14), 3525-3528). cells, also based on Ru(I1) complexes. This is due Thin films (- 1000 A) of the Ru(I1) complex to a slow electrochemical “charging” mechanism, were spin-cast onto an indium tin oxide (anode) which redistributes the counterions to create patterned glass &om pyridine solutions. An alu- redox states for charge transport and light emis- minium cathode completed the devices. All sion, and delays the device response after an devices had luminance levels of 1000 cd rn-’ at applied potential bias. If solid-state devices are 5 V and 200 cd m-’ at 3 V and external quan- to be used in flat-panel displays, clearly shorter tum efficiencies of 1 per cent at low voltage. The “charging” times (to brightness) are required. emitted red light could be shifted to a more use- Now, a team from Massachusetts Institute ful red with increased device stability on replac- of Technology has produced single-layer, spin- ing ligands in (1) by esterified bpy ligands. Device cast films of small-molecule Ru(bpy),(PF,), (1) response times can be shortened by using short, complexes (bpy = 2,2’-bipyridine) with high- high-voltage pulses, and low voltage operation.

Nariwuiit Mdcds Rev., 1999, 43, (3) 104 Organometallic Chemistry and Applied Catalysis A REVIEW OF THE THIRD ANGLO-DUTCH SYMPOSIUM By Berth-Jan Deelman Elf Atochem Vlissingen B.V., Vlissingen, The Netherlands

The latest Anglo-Dutch Symposium on libraries, containing over 10,000 members, there organometallic chemistry and applied cataly- is a practical problem with identifymg and keep- sis was held at the University of Shefield from ing track of the many individual ligands or 29th to 30th March 1999. It was the third sym- catalysts that are synthesised. posium of these highly successful meetings This problem does not occur in parallel syn- between the Dutch and British communities theses, but the technique appears to be best involved in organometallic chemistry and catal- suited for smaller libraries, typically with less ysis. Previous meetings have been held in than 1000 members, although equipment Amsterdam (1997) and in Sheffield (1996) fol- for the generation of larger libraries is being lowing an initiative by P. M. Maitlis, K. Vrieze developed. and G. van Koten (Universities of Sheffield, Current applications and developments in Amsterdam and Utrecht, respectively). “combinatorial catalysis” are therefore mainly A total of 120 participants attended this sym- carried out using the parallel approach. It is clear posium which covered a wide range of subjects that another very relevant issue, although not in catalysis. In addition to lectures by a large addressed by Turner, concerns how a ligandi number of well-known researchers, a poster ses- metal complex library with sufficient diversity sion displaying more preliminary results also of ligands should be constructed, and how the formed part of the programme. Below, high- feedback from the screening results should be lights relevant to catalysis using platinum group incorporated into the library, so as to help focus metals are described, as well as some generally the screening process. interesting developments in catalysis which were Platinum group metal based homogeneous discussed during this meeting. catalysts and the use of rapid screening techniques for finding catalysts for specific catalytic General Developments in Catalysis reactions is also of interest to Johnson Matthey, A promising new development using micro- as reported by A. K. Keep. Often, each specific reactors in catalysis was presented by R.W. K. combination of substrate and desired catalytic Allen (University of Sheffield). The favourable reaction requires a particular catalyst and con- heat and mass transfer properties in these reac- sequently a dedicated screening process. This tors can lead, in some cases, to better selectiv- observation explains the intense current inter- ity (reactor control). These reactors appear to est in rapid parallel screening techniques for be especially promising for fuel cells but may be catalysis. even more so for rapid parallel screening of Workers at the University of Liverpool have catalyst libraries. developed a new high pressure gas flow cell for An overview on recent developments in com- NMR spectroscopy. This has been developed binatorial synthesis, especially in the area of for in situ spectroscopy and B. T. Heaton catalysis, was given by M. L. Turner (University described the cell and its uses. It can, for exam- of Sheffield). Although the so-called “split and ple, be used to study intermediates in rhodium mix technique” is very effective for creating large catalysed hydroformylation. The technique

Platinum Metals Rev., 1999, 43, (3), 105-108 105 allows NMR measurements to be made under rhodium-based process. For instance, it has been catalytic conditions while gas is bubbling through found that deactivation of the catalyst takes place the sample. by the build-up of HI which enters the water- gas shift reaction to form inactive [Ir(CO)J,]-. New and Improved Catalysis This can now be successfully suppressed using R. A. van Santen (Technical University of ruthenium carbonyls (such as [Ru(CO),12]) and Eindhoven, The Netherlands) described the oxi- other Lewis acidic I- acceptors (such as InI, or dation of ammonia to dinitrogen and water, GaI,) as promoters. It was demonstrated by achieved using alumina-supported platinum, model reactions that the role of the promoters iridium or copper catalysts. The catalysts devel- is to abstract I- from the electronically unsatu- oped have a high tolerance to water and use rated F(CO)(Me)I,] intermediate, which accel- oxygen as the promoter. erates the migratory insertion of CO to form Interestingly, the detailed thermodynamics of the iridium acyl complex, by - 800 times. every step of the catalytic cycle as well as those The selective hydroformylation of internal of deactivation pathways and side reactions olefins to linear aldehydes was described by P. ((NO), formation) are well understood, based C. J. Kamer (University of Amsterdam). This on high level molecular orbital (MO) calcula- was achieved using rhodium-xantphos and tions on low molecular weight model com- closely related complexes as catalysts under low pounds. Pt(NH,), supported on HZSM-5 zeo- carbon monoxide pressures. The catalyst first lite also proved to be an active ammonia isomerises the alkene to the terminal olefin and reduction catalyst at low temperatures (473 K), then starts to hydroformylate it. with increased activity and selectivity when water An elegant 3-component coupling of two is present in the feed. The group at Eindhoven equivalents of an electron-poor alkene, an alkyl is now developing catalysts for the electro- halide and an alkyltin compound, using a Pdo chemical oxidation of ammonia. complex of the BIAN ligand (BIAN = Detailed accounts of recent improvements and bis(imino)acenaphthene), was described by C. better understanding of the BP/Amoco Ir/T catal- J. Elsevier (University of Amsterdam), see ysed methanol carbonylation process were given Scheme I. by R. Watt (BP/Amoco) and A. Haynes The selective partial hydrogenation of inter- (University of Sheffield). From a technical and nal alkynes was also accomplished using process economics viewpoint, the iridium sys- (BIAN)Pd"(cis-E-CH=CH-E) (E = CF,, tem has some major advantages over the older C(0)OMe) (87 per cent selectivity for stilbene).

Platinum Metals Rev., 1999, 43, (3) 106 Compared to the well-known Lindlar catalyst, geneous catalysis is largely an undiscovered ter- less E-alkene was synthesised, but sometimes ritory. Deactivation is understood for only a few more alkane is formed. well-known catalysts. The question remains why this is so. It may be that deactivation is not usu- Asymmetric Homogeneous Catalysis ally investigated because of the higher ratio of In an enthusiastic presentation, V. K. Agganval product:catalyst value, compared with hetero- (University of Sheffield) explained that his group geneous catalysts which are often used in bulk has developed a catalytic process for the direct applications. If this is the case, then homoge- synthesis of chiral epoxides from aldehyde and neous catalyst recycling may be less economi- diazoalkane derivatives, see Scheme 11. The cat- cally interesting. Nevertheless, there may be alytic process is believed to consist of two cycles, other reasons (environmental issues or opti- one involving a rhodium alkylidene and one mising the use of noble metals) to explain the involving a chiral sulfur ylide. In some cases, efforts going into developing methods for recy- [Cu(a~ac)~]was found to be more beneficial cling homogeneous catalysts. than [Rh,(OAc),], although it is not clear which One such approach is the development of flu- copper species are formed. Enantiomeric orous catalysts (fluorous refers to being soluble excesses (ee) were generally better than 90 per in a fluorinated solvent) which can be recovered cent. Using a similar approach, chiral aziridines by selective extraction with fluorous solvents. were also accessible, starting from a function- Some methods for rendering conventional noble alised imine as reactant instead of the usual metal catalysts fluorous, by the use of 4- aldehyde. C,H,C,F,,+, units to prepare triaryl phosphines Chiral cyclopentadienyl ligands with pendant and bis(diary1phophino)ethane ligands, were -C6H,-2-C'(H)MeNMe, arms were reported by presented by E. G. Hope, University of C. White (University of Sheffield) to be rea- Leicester. In most cases the fluorous domain of sonably effective (ee > 71 per cent, using the catalyst has a negative effect on catalytic [C,Me,-C,H,-2-C*(H)MeNMe2RhC1,]as cat- activity, but at the same time preferential fluo- alyst and a 10-fold excess of free ligand) for the rous phase affinity requires the catalyst to have asymmetric hydrogenation of non-functionalised substantial fluorous character (> 60 weight per 1-alkenes, a reaction which is known to be cent F). The "trick" in this branch of catalysis notoriously difficult. appears to be to design an ideal electronically insulating spacer to separate the large fluorous Supported Catalysts and domain from the active metal centre. While bet- Catalyst Recycling ter results were obtained using P(O-C,,H4-4- A number of presentations dealt with cata- C,F,,,+,),(for rhodium catalysed hydroformyla- lyst deactivation and methods for recycling. tion) and P(C6H,-4-OC,F,,+,) (for rhodium As explained by the symposium host, Professor catalysed hydrogenation), the retention of the P. M. Maitlis, catalyst deactivation in homo- fluor phase by the catalysts and ligands, and

Platinum Metals Rev., 1999, 43, (3) 107 CHzCC(0)M,CHIPPh,

Ph,PCH,CH~(O)COH~C CH$C(O)CH$W2PPh2

PhiPCH~CH2(O)COHzC CH20C(0)CH2CYPPh2

Ph,PCHzCH2(O)COH2 CH,CC(0)CH1CH2PPh,

CH~OC(O)CH~CH~PP~Z

Fig. 1 A palladated derivative of a phosphine functionalised denclrirner.This has been successfully used as the catalyst in the codirnerisatiori of styrene and ethylene

consequently their efficient recycling, remain at the Symposium, but are not reviewed here. to be investigated. In conclusion, the quality of the work under- Another approach to catalyst recovery is to taken in the U.K. and in The Netherlands and anchor the catalyst to a well defined macro- described at the Symposium should ensure that molecular support, which will keep the catalyst these Symposia will play an increasing role in on one side of the microporous membrane in the exchange of ideas on catalysis. a membrane reactor. If the large support is sol- The fourth Anglo-Dutch Symposium is uble and indeed well defined, then fast single expected to take place in The Netherlands in site homogeneous catalysis can take place. the autumn of 2000, probably at the University Professor G. van Koten, Utrecht University, of Utrecht. described this technique and noted that car- bosilane dendrimers may be the ideal support Sonochemical Platiiiiiiii Reduction for this. In his group nickel- and palladium- Platinum nanoparticle, of interest because of their high catalytic activity, were prepared in an functionalised dendrimers have already been aqueous system using high density ultrasound prepared. The palladated derivative of a phos- (200 kHz and 6 W cm '). The nanoparticles phine functionalised dendrimer has been suc- were found by researchers fi-om Osaka Prefecture cessfully used as the catalyst in the codimeri- University (y. Mizukoshi, R. Oshima, Y. Maeda and Y. Nagata, Langnzuir, 1999, 15, sation of styrene and ethylene, see Figure 1. (8), 2733-2737) to be smaller and more regular than Catalyst retention in a membrane reactor is those made radiochemically. Stable, homoge- already rather good for relatively low molecular neously spherical, monodispersed Pt nanopar- weight dendrimers but catalyst deactivation is ticles, of average diameter 2.6 nm, were formed still a problem. Investigations into the origin at the rate of 26.7 pM min ' in a Pt(I1)-sodium of this deactivation, whether membrane or den- dodecyl sulfate system. Three kinds of reducing species are proposed to be formed in drimer-related, are now being performed. the sonicated system, near and/or in the hot Other interesting contributions, not concerned bubbles, and these then react with the PtCI,' with the platinum group metals, were presented complexes to form the platinum nanoparticles.

Pluriiiuwi Metals Rev., 1999, 43, (3) 108 Catalyst Enhanced Oxidation of VOCs and Methane in Cold-Plasma Reactors By Muhammad Arif Malik Applied Chemistry Division, PINSTECH, PO Nilore, Islamabad. Pakistan and Salman Akbar Malik Department of Biological Sciences, Quaid-i-Azani University, Islamabad, Pakistan

Volatile organic compounds, VOCs, are used in a number of industrial processes in a variety of roles, for instance as solvents, cleaners and liquid fuels. During theseprocesses, some of the VOCs, which are known to be air toxins, inevitably esrape into the surrounding air. It is the release of this VOC-laden air into the atmosphere that is partly responsible for stratosphrric ozone depletion, tropospheric ozone increase, global warming (the Greenhouse Effect) and some health problems. Here, we brieJly review some applications of platinum metals catalysts in the abatement of VOCs and in the conversion of methane using cold-plasma techniques. Some iitformarion on the abatement of acidgases, the generation and application of non-thermal plasmas is also presented.

Volatile organic compounds, VOCs, which are Heavier ions and the bulk of the neutral mole- toxic by nature and which are used in industrial cules remain close to room temperature (6, 7). processes as solvents, cleaners, thinners, The high-energy electrons undergo inelastic col- degreasers, monomers and liquid fuels, can be lisions with the ambient gas molecules to pro- converted into water and less harmful carbon duce reactive species, such as '0, 'OH, 'H02, dioxide by thermal incineration at high tem- 'H, 'N, 02',N2', 0,,03*, 0 , Oz, OH, N?+,N, peratures (> 700°C) (1). However, thermal 02+and 0' (6-8, 14, 24, 25). These free radi- incineration requires a lot of energy to heat up cals, ions and excited-state molecules in turn the ambient gas molecules. Some of this energy oxidise the targeted VOCs. can be saved by incorporating a suitable cata- Cold-plasma techniques are rapidly being devel- lyst into the incineration system, enabling the oped for the destruction of toxic VOCs in air (3, oxidation reaction to be performed at lower tem- 4, 26-29), soil (30) and water (3 1, 32), as dis- peratures (- 300 to 500°C) (2). Clearly, this still cussed in reviews (15, 33-43). Thev are also involves using elevated temperatures. being developed for the abatement of other air The use of cold plasmas can offer a promis- pollutants, such as sulfur oxides, nitrogen oxides ing alternative to the combustion of VOCs. By and carbon dioxide (7-9, 34, 35, 38,44,45). selectively channelling electrical energy into the desired plasma, chemical reactions occur at Cold Plasmas with Catalysts amhient temperature and pressure to break up Combining cold plasmas with catalysis is an the VOCs into smaller components (3,4). Cold emerging technique which can oxidise VOCs at plasmas are produced by electrical discharge a much faster rate, at a lower temperature and techniques (5-15), and have been utilised in a with lower input energy, when compared with number of industrial applications (5-8, 16-23). cold plasma or thermal catalysis techniques alone In cold-plasma techniques, free electrons are (15, 20, 46-49). accelerated under the influence of the strong For example, when acetone-containing air was electric field produced by electrical discharge. passed at a flow rate of 400 cm' min ' through

Platinum Metals Rev., 1999, 43, (3), 109-1 13 109 a wire-cylinder type pulsed corona discharge efficiency after a very short treatment time when reactor, the acetone concentration was reduced palladium- and platinum-coated y-alumina were from 40 to 30 pmol min I. When the discharge used in a corona discharge reactor (15). gap of this reactor was packed with alumina pellets (3-5 mm diameter), the acetone concen- Partial Oxidation of Methane tration was found to be further reduced from The partial oxidation of methane (a major 40 to 6 pmol mid, the other operating condi- component of natural gas) in cold plasma yields tions being identical (48). The operating con- far more valuable products than its complete ditions were: room temperature, atmospheric oxidation (to carbon dioxide and water). C2 pressure, 9 W power from a DC source (as high products (ethane, ethene and acetylene) (56, voltage pulses of 45 kV (positive polarity), 4 57), hydrogen (58), synthesis gas (59-61), ps width, 0.4 ps rising time and constant fre- methanol (62-66) and formic acid (66, 67) quency) and a reactor volume of 100 cm' (48). are just some of these products. There was, however, almost twice as much of There are two major obstacles to overcome in the by-product ozone produced when alumina methane activation: was present. [l] the tetrahedrally arranged strong C-H When the macroporous alumina was replaced bonds of methane do not allow space for by alumina having primarily meso- and micro- oxidising agents to attack and pores, the ozone was reduced to a negligible [2] the 'CH, produced from methane is likely level, without affecting the efficiency of the VOC to undergo further oxidation, which may destruction (49). Alumina can therefore be used convert it to carbon dioxide and water. as the support for the active metal catalysts. Consequently, conventional thermal activation In a further example, palladium-coated spher- of methane requires high temperatures (> ical pellets of porous y-alumina were shown to lOOO"C), gives low yields and is costly. The addi- decompose methane in corona discharges (15, tion of suitable catalysts, particularly supported 50). The nitrogen oxides formed were signifi- noble metal catalysts, such as platinum, palla- cantly reduced when this palladium coated y- dium, rhodium and ruthenium, can activate alumina catalyst was employed. methane at relatively lower temperatures, at By comparison with conventional catalytic faster rates and with better selectivity to the reactors, excellent results have also been achieved desired products (68, 69). using platinum, palladium and rhodium, for example, as catalysts in cold-plasma catalytic Effects of Microwave Irradiation reactors (51), to convert Freon and methane Microwave irradiation of suitable catalysts, into simpler molecules. such as proton conductive catalysts, oxygen ion Electrode surfaces can also catalytically conductive catalysts, activated carbon or char- enhance the oxidation of VOCs, if a catalytically coal, can convert methane at lower tempera- active material is incorporated into the electrode tures and give higher yields of the desired prod- structure. When stainless steel electrodes were ucts than conventional heating (70-75). Under replaced by electrodes having catalytically active certain conditions, microwave irradiation can noble metal or noble metal alloy surfaces, the generate cold plasma which selectively converts destruction of methane in cold plasma was methane to acetylene (72). Methane conversion improved (52). in plasma takes place faster, at lower tempera- The decomposition of air pollutants other than tures (- 500°C) and needs lower input energy VOCs (sulfur oxides, nitrogen oxides and car- (about one half) than the thermally driven bon dioxide) has also been improved by the process (76, 77). addition of suitable catalysts in the cold-plasma Indeed, combining the cold plasma with catal- environment (15, 53-55). As an example, sul- ysis can further improve the energy efficiency fur dioxide could be removed with high as well as the selectivity of the desired products

I'Iatinutir Metals Rev., 1999, 43, (3) 110 (20,78-8 1). In general, methane conversion in (56-67). The addition of a suitable catalyst in different reactors follows the order (80): the discharge gap of corona discharge reactors has achieved faster rates of methane conversion Plasma-catalytic > plasma > catalytic > thermal and better selectivity to the desired products, High-energy electrons and oxidising species, while requiring less input energy than when such as '0,O- and 02, present in the cold plasma catalyst is absent (20, 84-86). environment, can produce 'CH, radicals from Replacing the stainless steel electrodes in the methane by hydrogen abstraction (56,82,83). cold plasma reactor with ones containing some The catalyst adsorbs the free radicals and their catalytically active metal can enhance methane target molecules, allows the desired chemical conversion. Almost the same methane conver- reaction to take place on a solid surface and sion (- 6 per cent) and selectivity for C, prod- finally releases the products (79, 80). ucts (- 80 per cent) were achieved with about When catalytic materials, such as platinum, half the input power (35 kV, 4.6 W) by using nickel, iron, manganese dioxide and molybde- copper instead of stainless steel electrodes (45 num trioxide, were placed next to the microwave kV, 9 W) in a DC pulsed corona discharge reac- plasma cavity (79, 81), platinum was found to tor at a flow rate of 30 cm3 min-' for a give the highest methane conversion of 55 per methane:oxygen feed of 95:5 (87). cent. Product selectivities of 54 per cent for Noble metal electrodes have the best results ethane, 27 per cent for ethylene, 7 per cent for for the conversion of methane to CLhydrocar- C, hydrocarbons, and 6 per cent for formalde- bons in a pulsed corona discharge. Results for hyde/methanol were achieved with platinum the electrodes were in the following order (88): as the catalyst. Platinum > palladium > copper The application of an electric field inductance (EFI),used to evolve a high density of microwave Conclusion plasma to the cold-plasma-catalytic reactor, From the above discussion, it may be inferred results in further increases in the methane con- that using catalysts, particularly catalytically version (80). The highest methane conversion active platinum group metals, in cold-plasma to C2 hydrocarbons, of 63.7 per cent, was reactors has become an active area of research achieved by employing a palladium-nickel in the last few years. The growing demand for bimetal catalyst in the cold-plasma-catalytic controlling VOC emissions, for better utilisa- reactor in the presence of EFI. tion of natural gas reserves, together with the rapid pace of development in this area, suggests Effects of Corona Discharges that there may well be future applications for A disadvantage of microwave plasma is that it such catalysts on an industrial scale in cold- usually operates at pressures below atmospheric, plasma reactors. which makes it less suitable for large-scale applications. Cold plasmas established at ambient Acknowledgment Financial support from the Ministry of Science and conditions, such as by corona discharges, have Technology, Government of Pakistan, is gratefully proved successful for methane conversion acknowledged (Ref. No. HRD~~/CH(~)~~~-ASA(TI~)).

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Platinum Metals Rev., 1999, 43, (3) 113 Combined Homogeneous and Heterogeneous Catalysts SYNERGISTIC NON-LEACHING TETHERED SYSTEMS By David T. Thompson Consulting Chemist, Reading, England

A number of both large- and small-scale homo- that of the tethered complex or of the supported geneous catalytic processes have been in com- metal separately (40°C and 1 atm hydrogen). mercial operation for many years (1 --7), and a Rates and turnover frequencies, TOF, were low significant proportion of these depend on plat- but the results indicated that there was poten- inum group metals catalysts, sometimes involv- tial for more combination reactions of this type. ing more than one metal. The Carha process Two TCSM catalysts were prepared by tethering operated by BP Chemicals for the production one of the rhodium isocyanide complexes, of acetic acid from methanol, has recently been RhCl(C0) [CN(CH,),Si(OEt),], (Rh-CNR?) or using a soluble iridiumiruthenium catalyst sys- RhCl[CN(CH,)Si(OEt).] (Rh-CNR,), to a tem which includes both of these features (4). silica supported palladium metal catalyst In general, homogeneous processes are char- (PdiSiO,) by refluxing in toluene for 4 hours, acterised by both high chemical and high energy see Figure I. utilisation efficiencies but a major deterrent in the further exploitation of this methodology has Hydrogeiiatioii of Areiies been the perceived inability to readily separate In a more recent paper (6) on this topic, the products from the catalysts. Aticnipts to rhodium and platinum isocyanide complexes overcome this difficulty have included ligand RhCl(C0) [CN(CH,),Si(OEt),], (Rh-CNR,), modification, biphasic catalysis and efforts to RhCI[CN(CH,),Si(OEt) .] (Rh-CNR,), and support homogeneous catalysts on polymeric PtCI,[CN(CH,),Si(OEt) ,I, (Pt-CNRJ were and inorganic supports. The use of supports for tethered to the SiO,-supported platinum group the catalysts has in the past been only partially metal heterogeneous catalysts M-SiO, (M = Pd, successful as most of these systems have lost Pt, Ru) to give the TCSM catalysts: Rh- catalytic metal species into solution during the CNRJPd-SiO,, Rh-CNR,/M-SiO, (M = Pd, Pt, reactions. Ku) and Pt-CNRJPd-SiO,, respectively. These The recent results reported by R. J. Angelici TCSM systems were used to catalyse the hydro- and H. Gao of the Iowa State University, U.S.A., genation of arenes (Rh-CNR,/Pd-Si02 and Rh- are therefore of particular interest, because they CNR,/M-SiOl) and cyclohexanone (Pt- result from combining the attributes of a firmly CNR?/Pd-SiO,)under the same mild conditions tethered homogeneous catalyst with synergistic of 40°C and 1 atm hydrogen. They again showed assistance from a silica-supported metal-parti- activities that are higher than those of the homo- cle heterogeneous catalyst (5-7). These effects geneous Rh (or Pt) isocyanide complex by them- were demonstrated in arene hydrogenation, and selves, the Si0,-supported metal heterogeneous such a combination catalyst has been called a catalyst itself, or the Rh (or Pt) complex cata- “tethered complex on a supported metal”, lyst tethered to SiO, itself. The activities of the TCSM. TCSM catalysts were strongly affected by the In the earliest of these three papers (5), the nature and loading of the supported metal in first examples of TCSM catalysts were reported. the catalyst. Of the three Si0,-supported metal Activity for the hydrogenation of toluene to catalysts, M-Si0, (M = Pd, Pt, Ru), the Rh com- methylcyclohexane was substantially higher than plex Rh-CNR, tethered on Pd-SiO, gave the

Plorrnum Metals Rev., 1999, 43, (3), 114 115 111 highest activity for the hydrogenation of toluene (TOF = 5.5 mol H, (mol Rh min) and turnover L’ number, TON = 2420 mol H, (mol Rh) during 8.5 h). The Rh-CNR,/Pd-SiO, catalyst with 10 wt.% I’d is more active than its counterparts particle with higher or lower Pd loadings. Spectral studies using diffuse reflectance infrared Fourier transform (DRIFT) measurements on the TCSM catalysts before and after use for toluene hydrogenation showed that the isocyanide lig- Fig. 1 Representation of a tethered eouiplex ands remained co-ordinated to the Rh (or Pt) on a supported metal (TCSM). The metal complex, M(L‘)JX, is a homogeneous complex centre, even after extended use. Furthermore, catalyst and is supported nu a heterogeneous atomic emission spectroscopic analysis of the metal catalyst, which consists of metal particles hydrogenation solutions indicated that there was on a silica support. The metals of the complex and of the heterogeneous catalyst may he no leaching of Rh (or Pt) into the solutions. combinations of two platinum group metals. One possible mechanism of these reactions, They act synergistically, to give enhanced which may help to explain the high activities results, superior to those of the component catalysts of the TCSM catalysts, involves considering the supported palladium particles as the sites at which hydrogen is dissociated and spills over onto the silica. The tethered homogeneous com- ularly fast reaction time and high TOF of 1.19 plex may bind and activate the arene substrate, min was achieved, together with a high n:iso and this then reacts with the spillover hydrogen, ratio of 12.0. thus producing the synergistic effect. It can be anticipated that further investigations on the effective tethering of organometallic cat- Hydroformylation of 1-Octene alysts to inorganic supports which carry cat- In another paper from the same laboratory, alytic metal particles will lead to more exam- the hydroformylation of 1-octene was studied ples of synergistic effects in TCSM catalysts. under atmospheric pressure using rhodium car- This could result in the emergence of a broad bony1 thiolate complexes tethered to silica (7). range of possible applications in both the spe- It was shown that these catalysts are highly active ciality and large scale chemical processing areas. for 1-octene hydroformylation in the presence of phosphine donor ligands at 60°C and 1 atm. References The high activity resulted from the stabilisation A. W. Parkins in “Insights into Speciality Inorganic Chemicals”, ed. D. T. Thompson, Royal Society of Rh(SR)(CO)J’R, (I) species on the cata- of Chemistry, Cambridge, U.K., 1995, p. 105 lyst surfaces. High selectivity to aldehyde was “Applied Homogeneous Catalysis with produced and the n:iso product ratios could Organometallic Compounds: A Comprehensive Handbook”, in 2 volumes, eds. B. Cornils and W. be widely varied by choosing an appropriate A. Herrmann, VCH, Weinheim, 1996 phosphine (R‘ in (I)). The catalysts were eas- W. A. Herrmann and B. Cornils, Angew. Chenz. ily separated from the reaction mixtures and the Int. Ed., 1997, 36, (lo), 1048 catalyst activity could be maintained through at M. J. Howard, Book of Abstracts, 11th International Symposium on Homogeneous least three cycles over a total period of 69 hours, Catalysis, University of St Andrews, Scotland, during which time there were 1273 (mol alde- Royal Society of Chemistry, July 1998, M2 hyde (mol ph) ’) turnovers. The hydroformy- H. Gao and R. J. Angelici, J. Ani. Chern. SOL., lation rate, conversion, and chemo- and regios- 1997, 119, (29), 6937 H. Gao and R. J. Angelici, Organometallics, 1999, electivity were markedly affected by the 18, (6), 989 phosphine donor and the PR,:Rh mole ratio. H. Gao and R. J. Angelici, Orgunonzerallics, 1998, With the l?(OPh), phosphine ligand, a partic- 17, (14), 3063

Platinuni Metals Rev., 1999, 43, (3) 115 The Effects of Hydrogen on the Physical Properties of Palladium HYDROGEN-PHASE “NAKLEP” PHENOMENON DURING THE HYDROGEN TREATMENT OF PALLADIUM By Y A. Goltsov Donetsk State Technical University, Donetsk, Ukraine

Palladium is not polymorphic, which is why phases and producing defects in the crystalline the physical metallurgy of palladium and its structure. alloys is quite poor in comparison with those Because of the complex nature of this type of polymorphic metals (such as iron, titanium, of physical phenomenon, it has been described and others). In recent years advances in the as “hydrogen-phase naklep” or the “HPN- physical metallurgy of palladium and its treat- phenomenon” (2, 5). ment have been taking place. The changes are based upon the physical effects that hydrogen Strengthening Effects has upon palladium when it is taken into the Annealed palladium has relatively poor metal (1). In Ukraine and Russia this has been mechanical properties, namely: called “hydrogen-phase naklep” and was first Ultimate strength 0” = 180-200 MPa; noted in 1972. This observation has led to Yield limit o,):=50-100 MPa; an improved concept in materials science and Relative elongation 6 = 20-25 per cent. engineering (1-5). When palladium is saturated with hydrogen, An early noted HI”-phenomenon (1) was it becomes a polymorphic material and hydride achieved by thermocycling specimens of pal- transformations may be induced in it by ladium wire in hydrogen (20 t) 250”C), after processes of heating t) cooling and/or satura- which the wire specimens (diameter 0.5 mm) tion t) desaturation. As there are differences were fully degassed. During the hydrogen treat- between the specific volumes of the a-hydrogen ment the strength properties of palladium solid solution and P-hydride phases in the pal- increased by a factor of 24,but the plastic prop- ladium, these hydrogen-induced phase trans- erties of palladium decreased. It was conse- formations cause internal plastic deformation quently surmised that the HI”-treatment (relaxation) and controllable strengthening of could be effectively used for strengthening pal- the palladium. Some basic changes of structure ladium articles, without noticeable charges to their also occur: the density of dislocations grows, dimensions and shape. the size of the ‘mosaic’ blocks decreases while their number increases, the angle of their dis- Superstrength Palladium Alloys: orientation increases, and so on. TRIP Alloys Unlike the internal cold work which occurs Treating palladium alloys with hydrogen with- during the martensitic transformations in iron out immediate degassing can result in the for- alloys, the structure changes mentioned above mation of superstrength palladium-hydrogen in palladium-hydrogen alloys are not only caused alloys having high plasticities - the hydride by internal plastic deformation but also by the TRIP-effect. (TRIP is transformation induced development of some very specific processes of plasticity.) interactions of the solute hydrogen in the The example shown in Figure 1 was achieved palladium, generating hydrogen-containing by a double (combined deformation-hydrogen)

Plutiiium Merals Rro., 1999, 43, (3), 116-1 18 116 treatment (3). First, 90 per cent of the possible plastic deformation of a palladium wire was induced, until it reached a specimen diameter of 0.5 mm. After this initial mechanical treatment, the palladium specimen had very high strength properties (points a and b) and very low plastic properties (point c). Samples were then HPN-treated. Hydride transformations, a + P + a, were effected by a number (n) of pressure cycles (0.2 MPa + 1.33 Pa + 0.2 MPa) in a hydrogen atmosphere at 100°C. After this the specimens were not degassed and a new palladium hydrided material was obtained. From Figure 1 it is clear that this new hydrogen- containing material (n = 1-2) is much stronger 0 1 2 3 4 and has been found to be more plastic than n the pure, annealed palladium. Fig. 1 Strengthening and TRIP-effects seen The nature of HPN-strengthened metals on palladium-hydrogen alloys which are having hydride TRIP-plasticity has been re- produced by “hydrogen-phase naklep” treatment of a barely cold-worked sample of viewed and detailed analysis of the hydrogen palladium wire. At n = 1-2, the material is treatment of metals and metallic materials, based much stronger and more plastic than the pure, on hydrogen phase naklep has been more fully annealed palladium. o0 is the ultimate tensile strength discussed (3, 4). ouris the yield limit 6 is the relative elongatioii Recrystallisation Treatment n is the number of pressure cycles HPN-strengthened palladium material has undergone recrystallisation annealing and its grain structure has been refined. others may be 3-5 times larger. Annealing twins Samples of palladium wire were annealed in have also been observed. Annealing at 400°C vacuum (about lO-’Torr)for 6 hours at 900°C. led to further development of these recrystalli- A metallographic investigation of the samples sation effects, while above 500°C the grain sizes was then undertaken. The samples were found became significantly larger (by about 7-10 to have extremely large grains (generally, only times). two or three grains in the 0.5 mm cross section of the wire). Their size was in the range Conclusion 0.25 to 0.15 mm. HE“ is the experimentally observed phe- The samples were then HPN-treated and met- nomena of the transitions of metals and alloys, allographic investigation showed them to have in particular palladium, into controllable high the same grain size as did the annealed samples. strength states with special physical properties Annealings at 100 and/or 200°C did not sig- during courses of charging with hydrogen and nificantly change the microstructure or the char- transformation of a-phase solid solution t) acter of the high angle boundaries. P-phase hydride. Therefore, HPN-phenomena However, for samples annealed at 300”C, the may form the basis for the hydrogen treatment development of first-stage recrystallisations may of palladium materials aimed at improving their be seen. Small, newly crystallised grains could structure and properties without noticeably be seen near the boundaries of the initially large affecting their dimensions and shape. Based on grains. The dimensionally smallest of these newly this treatment, novel advanced palladium alloys changed grains was of the order of 15 pm; but have now been made (5).

Platirzut,z Metals Rev., 1999, 43, (3) 117 References 1 V. A. Goltsov, Muter. Sci. Eiig., 1981, 49, 109 4 V. A. Goltsov, “Hydrogen Barothermal Treatment 2 v, A, Goltsov,=me phenomenon of Controllable of Metallic Materials -A New Field of Hydrogen Hydrogen Phase Naklep and the Prospects ofIts Use Technolo&’, Proc. 7th World Hydrogen Conf. in Metal Science and Engineering”,ROC. ht. spp. Hydrogen Energy Progress VII, Moscow, 25-29 Metal-Hydrogen Systems, Miami, 1 3-1 5 Apr., 1981, Sept., 1988, Vol. 3, pp. 1721-1740 Pergamon Press, Oxford, 1982, pp. 21 1-223 3 V. A. Goltsov, “Phenomena Induced by Hydrogen 5 Proc. Select. Papers of 1st Int. Conf. “Hydrogen and Hydrogen Induced Phase Transformations”, Treaunent of Materials”, Donetsk, Ukraine, 2C22 in “Interactions ofHydrogenwith Metals”, Science, Sept., 1995, Guest Editor V. A. Goltsov, Int. J. Moscow, 1987, Chap. 9, pp. 264292 (in Russian) Hydrogen Energy, 1997, 22, (213)

Platinum 1999 During 1998 the world supply of plat- demand &om the electrical sector increased inum increased by 9 per cent to reach 5.4 by 15,000 oz to 320,000 oz. million oz, while demand increased by 4 Sales for platinum investment products per cent to 5.35 million oz. Demand was rose by 75,000 oz to 315,000 oz in 1998, higher mainly due to the increased fabri- with higher demand for the platinum cation of jewellery in China and the U.S.A. American Eagle coins in the U.S.A. and However, industrial demand weakened large investment bars in Japan. slightly. Supplies of platinum from South Consumption of platinum by the chem- Africa declined slightly, but supplies from ical industry rose by 30,000 oz to 265,000 Russia, despite a four month suspension of oz, with demand for platinum process cat- exports during the first four months of alysts being strong. Typical of this was the 1998, rose by 400,000 oz to reach a record platinum used for the rising production 1.3 million oz. These are just some of the of silicones for sealants and adhesives for facts contained in the latest Johnson the construction industries of North Matthey annual market survey of the plat- America and Europe. inum group metals, “Platinum 1999”. The Fuel cells accounted for only a small part review covers the supply, mining and explo- of platinum consumption in electrical appli- ration, and demand for the platinum group cations but the prospects for significant metals during 1998, with most emphasis demand in the future is improving. Several being on platinum and palladium. car manufactures have demonstrated fuel The major industrial use of platinum is cell cars, but further work is required. in catalytic converters, and in 1998 this was Demand for palladium rose to 8.19 mil- unchanged at 1.83 million oz, supported lion oz in 1998, while supplies rose to 8.4 by a rising use of platinum for diesel million oz. Greatest demand was from the engines. Demand in Europe rose by 5 per auto industry which reached 4.47 million cent, due to increased sales of diesel cars. oz, an increase of 1.27 million oz compared In North America demand for platinum with 1997. rose by only 1.25 per cent as consumers “Platinum 1999” contains two special fea- showed a preference for larger sized gaso- ture on platinum in hard disks and on devel- line vehicles which carry palladium-based opments in automotive emissions legisla- catalyst systems. The implementation of tion which describes the increasingly strict tighter emissions standards and the selec- controls over vehicle emissions in Europe, tion by U.S. manufacturers of palladium Japan and the U.S.A. to meet hydrocarbon limits caused a 50 per Readers of Platinum Metals Review who cent surge in palladium sales. wish to receive a free copy of “Platinum An increase in the use of platinum for the 1999” are invited to contact Ms Emma hard disks of personal computers, which Johnson at Johnson Matthey PLC, 40-42 incorporate a platinum-cobalt layer to Hatton Garden, London EClN SEE; improve data storage, outweighed a lower e-mail: [email protected]; fax: +44- demand for thermocouples. In total, (0) 20-7269-8389.

Plutiiirriii Metuls Rev., 1999, 43, (3) 118 Aftertreatment for Low Emission Vehicles A SELECTIVE REPORT FROM THE 1999 SAE ANNUAL CONGRESS The 1999 annual congress of the Society of low temperature light-off, and when combined Automotive Engineers (SAE) took place in with effective heat - and mass transfer and low Detroit from 1st to 4th March with 46,309 del- heat capacity, respond quickly. Mounting the egates and l 104 companies exhibiting new prod- catalyst close to the manifold (close-coupled) ucts. Some 1120 papers were scheduled for pre- minimises the time the catalyst takes to reach sentation covering all the automotive technologies, working temperature. although fire curtailed some sessions. Papers In the U.S.A., SWN and MECA (1999-01- on exhaust gas aftertreatment focused on tighter 0774) demonstrated that LEV I1 ULEV levels emissions requirements from conventional gaso- can be obtained by combining advanced cata- line, lean-burn gasoline and diesel engines. Some lysts on high cell-density substrates with insu- new legislation and a selection of papers are lated exhaust components. In examining sys- reviewed here, with SAE numbers being given. tems for Europe - Elasis, Napoli University, Magneti Marelli and Fiat in Italy (1999-01-0775) New Legislation concluded that a close-coupled starter catalyst In 1998 a number of new emissions levels were and a main underfloor catalyst, or a closed-cou- introduced or proposed. In the U.S.A. National, pled main catalyst, are cost-effective solutions. NLEV, standards were adopted in 49 states, and the Environmental Protection Agency (EPA) con- Thin Wall High Cell-Density Catalysts cluded that the more stringent Tier I1 standards These catalysts have high geometric surface area were needed. California adopted a LEV I1 pro- with lower heat capacity and backpressure than gramme, stringent standards for hand-held engines, standard materials. BMW, NGK and Friedrich a three-way catalyst (TWC) based standard for off- Boysen (1999-01-0767) developed a system with road spark ignition (SI) engines less than 25 hp, a relatively thin wall substrate (400 cpd4.3 mil, tight standards for recreational marine engines, cells per square inchhhousandths of an inch) for and higher requirements for some motorcycles. a LEV/Stage 3 V8 engine. This had a close-cou- The EPA announced plans to establish a volun- pled high palladium tri-metal catalyst on each tary heavy-duty diesel engine retrofit programme. air-gap insulated manifold, and an underfloor The revised LEV and ULEV standards involve palladiudrhodium (Pd/Rh) catalyst. Corning, major hydrocarbon (HC) and nitrogen oxides Johnson Matthey and DaimlerChrysler (1999- (NOx) reductions, and the SULEV standard has 0 1-0273) compared physical durability of stan- exceptionally demanding emission levels. dard (400 cpsU6.5 mil) and thin wall substrates In Europe gasoline car emissions have been (600 cpd4.3 mil and 400 cpsU4.5 mil) coated agreed for 2000 (Stage 3) and 2005 (Stage 4). with high temperature stable washcoats. Predicted A range of measures will be developed for on- and measured thermal shock parameters agreed, board diagnostics (OBD), cold start and in- showing that the new catalysts have superior ther- service compliance along with tax incentives mal shock resistance and are suitable for close- allowed for early introduction of Stage 4 stan- coupled positions. dards. Gasoline and diesel fuel sulfur levels will Corning (1999-0 1-0269) confirmed improved also be markedly reduced. thermal shock characteristics are due to a lower coefficient of expansion resulting from improved Conventional Gasoline Engines composition and manufacturing processes. Low emissions demand that aftertreatment Delphi, Corning, SWRI and ASEC (1999-01- systems operate immediately after starting the 027 1) had benefits using 600 cpsU3.5 mil sub- engine. High activity catalyst formulations have strate over standard 400 cpd6.5 mil material;

Platinum Metals Rev., 1999, 43, (3), 119-121 119 but 600 cpsii4.3 mil had more backpressure, tages of Electrically Heated Catalysts in SULEV restricting acceleration, which was not the case systems. Increasing the gas temperature by elec- with the 600 cpsY3.5 mil substrate. trical heating can offset thermal mass effects DaimlerChrysler, Degussa and NGK (1999- and shorten the catalyst light-off time. 01-0272) reported a similar study for V6 and V8 engines for Stages 3 and 4. Their system Platinum Group Metals in Catalysts used close-coupled (600 cpsii3.5 mil) and two Originally TWCs were predominately plat- underfloor catalysts (400 cpd4.3 mil). inum/rhodium (Pt/Rh) formulations. Legislation, Contributions from the washcoat thickness to particularly in the U.S.A., emphasised attaining the backpressure of high cell-density catalysts low HC emissions, and Pd-containing catalysts were noted. Mazda (1999-01-0307) varied the can achieve high HC conversions. Using these amount and ratio of platinum group metals catalysts resulted in a wider use of I'd at increas- (pgm), catalyst promoters, catalyst layering and ingly higher loadings. Three types of Pd-con- cell-density. Both 600 cpsi/4 mil and 900 cpsii2 taining TWCs are available: Pd-only, Pd/Rh, mil substrates were examined, the latter giving and tri-metal (PdiRhlPt). The amount of Pd 35 per cent lower tail-pipe HC emissions. Honda used in autocatalysts now exceeds that of Pt and and NGK (1 999-0 1-0268) compared 600 cpsi/ Rh, and greater flexibility in the metals used 4.3 mil and 1200 cpsi/2 mil catalysts. High con- might help future supply/demand considerations. version was obtained with the high cell-density Johnson Matthey examined (1 999-0 1-0309) catalyst, but mechanical strength was a concern. conditions favouring PdRh compared with Pd- Honda's (1 999-01-0772) ZLEV system (one- only catalysts for NOx control. At low tem- tenth of the ULEV limits) had reduced engine perature both perform similarly, but high tem- emissions due to high swirl with variable valve peratures accentuated differences which give timing and lift, and improved spark plugs with advantages to PdiRh catalysts in NOx conver- durable small-diameter iridium centre elec- sions. This is because sulfide poisoning becomes trodes. They maintained high temperature and more significant at high temperature when the prevented quenching. Fuel control was opti- exhaust is rich (reducing), so actual catalyst mised during start-up, and precise air:hel con- choice depends on the vehicle. Johnson Matthey trol was maintained by controlling the air:fuel (1999-0 1-0308) showed that increasing the ratio in each cylinder. Retardation of the igni- Rh:Pd ratio in a standard lower loaded PdiRh tion gave fast heating of a close-coupled high catalyst maintained acceptable performance, cell-density Pd-only starter catalyst (1200 cpsi/2 but new improved formulations have lower Pd mil), followed by TWCs and a two layered cat- content. The activity of a new low-loaded PdRh alyst comprising a HC-trap with a top layer catalyst is better than the standard with twice TWC. At low temperature HC is trapped, but the amount of pgm. This will allow Pd load is released as the system warms to I OOOC, when reductions or improved performance at stan- the TWC layer converts part of the released HC. dard loadings. PdRh catalysts with higher activities than standard Pd/Rh formulations have Electrically Heated Catalysts also been developed, thus giving options for Trapping HCs when cold then releasing them managing pgm demand. onto a working catalyst has several variations. Other methods of treating HCs include Exhaust Lean-Burn Gasoline Engines Gas Ignition (EGI) when air-diluted rich exhaust Direct injection (DI) gasoline engines capa- gas is combusted ahead of a TWC, and the ble of lean operation offer reduced fuel con- use of a special catalyst which oxidises carbon sumption, but their NOx control is a challenge. monoxide (CO) at low temperature. Electrical One method is to store NOx and release it for pre-heating has been widely researched and reduction over a TWC. A NOx-trap combines Emitec (1999-01-0770) reviewed the advan- these. Ricardo (1999-01-1281) had a fast

Plariiiiim Metals Rev., 1999, 43, (3) 120 light-off close-coupled catalyst and underfloor such approaches will be insufficient in many NOx-trap on a car with a stratified charge DI situations, and methods able to provide high engine. With significant engine management NOx conversions are needed, Selective Catalytic modifications low tail-pipe emissions can be Reduction (SCR) being one. Ammonia, or a achieved, and effective NOx-traps allow engine derivative such as urea, is injected into the calibration for fuel economy. exhaust before a SCR catalyst.This can give Control of operating parameters is critical for NOx conversions of 75 per cent, but there is no optimum performance and Ford (1 999-01- infrastructure for urea distribution and the 1283) measured stored NOx from the quantity weight and volume of an additional tank for of fuel used in regeneration. Bosch (1999-01- refuelling must be considered. Another emerging 1284) described a management system for DI technology is NOx-trap technology, similar to gasoline engines, aftertreatment assumed a fast that for DI gasoline engines and operating at heated catalyst for early HC conversion, a NOx- the lower temperatures of diesel exhaust. Sulfur trap with low oxygen storage (OSC) and a TWC tolerance, low temperature operation and with significant OSC. Temperature and oxygen obtaining regenerating conditions are concerns. sensors provided control inputs. Toyota (1999- Soot (or PM) removal from diesel exhaust is 0 1- 1279) analysed NOx-trap sulfur poison- necessary to meet future legislation. Major ing, and suggested a hexagonal cell substrate of engine-based improvements have been suc- uniform washcoat thickness containing com- cessful, but more are needed. Hino (1999-01- ponents which form hydrogen via steam reform- 047 1) stated that with low sulfur fuel, high ing. While progress has been made, NOx-traps loaded Pt oxidation catalysts can remove some need low sulfur fuel, which should become PM, but with high sulfur fuel sulfate forms over increasingly available. the catalyst and thus increases the PM. The Continuously Regenerating Trap (CRF') uses Diesel Aftertreatment a Pt catalyst to provide nitrogen dioxide which Diesel engines run lean with excellent fuel oxidises filtered PM at low temperature and pre- economy, but reduction of their NOx and par- vents soot build-up in the filter and possible ticulate matter (PM) is difficult to achieve. uncontrolled burning which can destroy filters. Michael Walsh (1999-01-0107) reviewed diesel FEV described (1999-0 1-0 108) a light truck fit- legislation and the tremendous progress in diesel ted with a CRTT", cooled and filtered recycled combustion engineering, fuelling, and oxida- exhaust gas, and fuelled by low sulfur fuel. The tion catalysts. A few modern diesel cars already exhaust temperature of 200-500°C was suited meet Stage 3 emissions levels and a few small to a CRT''" and is likely to be used more in cars may meet Stage 4 requirements before future. FORTH/CPERI from Greece and 2005, but most vehicles will require effective Johnson Matthey (1999-01-0468) described NOx aftertreatment. design and selection criteria for sizing CRT""' filters. This employed a filter flow model that NOx Reduction and Soot Removal was validated by experimental measurement. Methods to remove NOx were discussed by the German FEV (1 999-0 1-0 108). Diesel Conclusions exhaust contains only a small concentration of The Detroit SAE Congress has again been a reducing species, limiting lean-NOx catalysts focus for reviewing developments in emissions to about 15 per cent conversion. Injecting fuel, control technology; catalyst systems containing via the engine or directly into the exhaust, pgms clearly will still play a most crucial role in increases the available reductant and can increase exhaust aftertreatment of low emission vehicles. NOx conversion to about 30 per cent. Degussa SAE papers may be obtained kom http://w.sae. and ICT (1 999-0 1-0 109) showed how two Pt org/products/sae99pap.htmor 400 Commonwealth catalysts could be optimised. Unfortunately, Drive, Warrendale, PA 15096. M. V. TWIGG

Platiriuni Metab Rev., 1999, 43, (3) 121 Johann Wolfgang Dobereiner’s Feuerzeug ON THE SESQUICENTENNIALANNIVERSARY OF HIS DEATH By Professor George B. Kauffman Department of Chemistry. California State University, Fremo

Johann WolJkang Dhreiner, born in 1780, was the Professor of Chemistry and Technology at the University of Jena, from 1810 to 1849. During this time he observed the action of platinum black on hydrogen, which led to his invention of thepneumaticgas lighter (Feueneug) and to Berzelius’concept of mtdysk, b~ides making other contributions to pure and applied chemistry. On the one hundred andfiftieth anniversary of his death in 1849 a Festkolloquium was held to commemorate his work at the Friedrich-Schiller-University of Jena. Here we describe some aspects of his Zqe and work.

On 7th May 1999, a Festkolloquium, in hon- Dobereiner, Professor of Chemistry and our of Johann Wolfgang Dobereiner, was held Technology at Universitat Jena. at the Friedrich-Schiller-University Jena About 300 persons gathered in the Dobereiner- (Friedrich-Schiller-Universitat Jena) .The event Hiirsaal of the Chemistry Institute, where “Das was organised by the Chemisch-Geowissen- L6kalkoinitee” presented a musical prelude begin- schaftliche Fakultat, Institut fur Anorganische ning with a poem written specially for und Analytische Chemie of the University, which Dobereiner’s 36th birthday (1 3th December was founded in 1558 and which has numbered 18 16) by his friend, the poet and dramatist, among its faculty the illustrious philosophers Johann Wolfgang von Goethe. The poem, ‘‘Den2 Johann Gottlieb Fichte, Georg Wilhelm Professor Dobereiner in2 Nanien seiner Kinder, zuni Friedrich Hegel and Friedrich Wilhelm Joseph Geburtsrag” (To Professor Diibereiner, in the von Schelling; the writer and critic Friedrich Name of His Children for His Birthday), sung von Schlegel; and the dramatist and poet Uohann to the melody of Ludwig van Beethoven’s musi- Christoph) Friedrich Schiller. The colloquium cal setting of Schiller’s “Aiz die Freude” (Ode commemorated the 150th anniversary of the to Joy) from his Symphony No. 9, in D Minor, death, on 24th March 1849, of Johann Wolfgang Op. 125, is as follows:

Wenn wir dich, o Vater sehen Whenever we see you, oh father, In der Werkstatt der Natur In Nature’s laboratory Stoffe sammeln. losen, binden, CoUecting, dissolving, combining substances, Als seist du der Schopfer nur, As if you alone are the Creator,

Denken wir: Der solche Sachen We think: Should whoever has Hat so weislich ausgedacht. So wisely invented such things. SoUte der nicht hlittel finden Not find the means Und die Kunst, die frohlich macht? And the art that makes us joyful?

llnd dam, schauen auf nach oben, And then, we behold on high, Wiinschen. bester Vater, wir, Best father, wishes, Was die Menschen alle loben, Which aU people praise, Gluck und Lbensfreuden dir... Gocd luck and joy in living to you ...

Pluriirirni Metals Rev., 1999, 43, (3), 122-128 122 Johann Wolfgang Dobereiner 1780-1849 After early struggles with solvency, Dobereher was appointed in 1810 to be. the Extraordinary (ausseronlentlich) Professor of Chemistry and Technology at the University of Jena. In 1823, he observed the ignition, by finely divided platinum powder, of a stream of hydrogen directed at it, the platinum becoming white-hot. News of this work, later to be called catalysis, was quickly published and led to other scientists repeating his work

The participants were greeted by Professor to element 112. The history of chemistry part Christian Robl, Dean of the Chemisch- of the programme consisted of the lectures, Geowissenschaftliche Fakultat, and Professor “Johann Wolfgang Dobereiner - a Pioneer for Klaus Manger, Speaker of the special research Modern Chemistry” by Professor Dietmar Linke programme “Ereignis Weimar-Jena, Kultur um of the Brandenburgische Technische Universitat 1800”. Cottbus and “Dobereiner’s Contemporaries - The scientific part of the programme consisted Chemists, Natural Scientists, Philosophers” by of two lectures by leading authorities in those Professor Egon Uhlig of the Friedrich-Schiller- fields of chemistry whose foundations were laid Universitat Jena. by Dobereiner - catalysis and the periodic system of the elements - “Heterocyclencarbenes: “The Most Brilliant Discovery” New Controlling Ligands in Catalysis” by As early as the 1820s, because of close rela- Professor Wolfgang Anton Herrmann, President tions between chemists across national bound- of the Technische Universitat Munchen, and aries and multiple publication of articles and “On the Nuclear Physical Limitation of the abstracts in different languages, scientific infor- Number of Elements - The 100-Year Journey mation could be transferred with a speed and from Polonium to Element 112” by Professor efficiency that is astonishing even to us in our Peter Armbruster of the Gesellschaft fur Internet era. As an example par excellence of Schwerionenforschung mbH Darmstadt. this phenomenon, Bill Brock cites Dobereiner’s Armbruster headed the team that discovered discovery in 1823, which the great Swedish the last seven elements of the Periodic Table up chemist, Jons Jacob Berzelius, later called

Platinum Metals Rev., 1999, 43, (3) 123 “catalysis” (1). On 27th July 1823, Dobereiner Thenard reported it on 26th August to the exposed hydrogen to powdered platinum pre- Academie des Sciences in Paris. On 13th pared by igniting ammonium hexachloroplati- September, Dobereiner demonstrated his dis- nate(IV), (NH,),PtCl,, and observed that on covery at the meeting of the Gesellschaft admission of air, at room temperature or even Deutscher Naturforscher und Arzte at Halle. at -1O”C, “after ten minutes all the admitted air Additional experiments by Thenard and Pierre had condensed with the hydrogen to form water” Louis Dulong (1785-1838), who described (2-4). them to the Academie on 15th September (13), When Dobereiner substituted pure oxygen for prompted Jean Nicolas Pierre Hachette air, the reaction intensified to the extent that (1769-1834) of the Ecole Polytechnique to write the filter paper holding the platinum charred. on 16th September 1823 to Michael Faraday That same week he reported his discovery to his (1791-1867) in London. Faraday began exper- patron, close friend and most famous student, iments of his own and related them in the Royal Germany’s greatest poet and playwright Johann Institution’s Journal of Science and Arts in Wolfgang von Goethe (1749-1832), who also October, the month in which Dobereiner pub- served in Grand Duke Carl August’s court as lished his own monograph on the subject (14). Qualified Minister (zustiindige Minister) for the That same month English translations of Universitat Jena. At the same time, he also Dobereiner’s and Dulong and Thenard’s arti- reported it to the editors of several scientific cles appeared in the Philosophical Magazine. journals. Thus, within three short months Dobereiner’s On 3rd August, Dobereiner observed that ifa discovery had been reported in a monograph jet of hydrogen was directed at the spongy plat- and in about a dozen European scientific jour- inum fiom a distance of 4 cm so that it was pre- nals. Berzelius, then the supreme authority on mixed with air, the platinum became red-hot, matters chemical, in his Jahres-Bericht, a series then white-hot and the jet ignited spontaneously. of annual reports that he had begun in 1821 This was the basis for what was to be called in order to review advances in physical science the Diibereinersche Feuerzeug (lighter) (5-10). during the previous year, wrote for 1823: “From This discovery, in which fire was produced with- any point of view the most important and, if I out flint and tinder, quickly created an inter- may use the expression, the most brilliant dis- national sensation and was immediately tested covery oflast year is, without doubt, that ...made and confirmed by many chemists and physicists. by Dobereiner” (1 5). This appraisal is even more remarkable in view of the fact that Berzelius had Rapid Publication of his Results previously held Dobereiner in the lowest esteem: By August, Dobereiner’s account had appeared “I do not know whether ...[ Thomas Thomson] in theJournalfir Chemie und Physik (2), Ann& or Dobereiner... is the worst chemist in existence der Physik (3), Annales de Chimie (9), Neues at the moment” ( 16). Journal der Pharmacie, Isis, and Bibliothbque UniverseUe (1 1). That same month Karl Wilhelm Dobereiner’s Life and Career Gottlieb Kastner (1783-1857), Professor of Who was this man who was suddenly thrust Chemistry and Physics at the Universitat into the limelight by his unexpected discov- Erlangen, wrote about it to Justus von Liebig ery? Born on 13th December 1780 in Hof an (1803-1873), who was then in Paris (12). der Saale in Bavaria, Dobereiner - a self-made At the suggestion of the German naturalist man in every sense of the word -was the son of and explorer Alexander von Humboldt a coachman who was not hnancially able to pro- (1769-1859), Liebig showed Kastner’s letter to vide the bright boy with any but the barest essen- Louis Jacques Thenard (1777-1857), who had tials of schooling ( 17-24). However, his mother also seen a brief report of Dobereiner’s work encouraged him, and, after three years of an in the Journal des Dibats of 24th August. apprenticeship with an apothecary, he began,

Platinum Metals Rev., 1999, 43, (3) 124 The great German poet, Johann Wolfgang von Goethe, who was a Minister for Grand Duke Carl August of Sachse-We--Eisenaeh, and the Duke in the court- yard of the castle at Jena. Goethe was a friend of Dobereiner. The Grand Duke appointed Dobereiner to be Professor of Chemistry and Technology at the University of Jena

at the age of seventeen, five precarious be Extraordinary (uusserordentlich)Professor of Wunderjuhre,eventually reaching Karlsruhe and Chemistry and Technology. Grand Duke Strasbourg, where he attended lectures on the (Grossherzog) Carl August (1757-1828) of sciences. He returned home and at the age of Sachse-Weimar-Eisenach, an enlightened and twenty-three married Clara Knab, a childhood liberal ruler and patron of the arts and sciences, friend. had asked Gehlen to recommend a successor to Although he was now an apothecary, Professor Johann Friedrich August Gottling Dobereiner had neither the money nor licence (1753-1809) who had died the previous year. to buy a pharmacy. He opened an agricultural Gehlen, who knew that Dobereiner was out of produce business and began to produce phar- work, proposed his name with little hope of suc- maceutical-chemical preparations. By 1803 he cess for he did not have a high school was reporting his experiments with white lead, (Gymnasium) certificate, nor any higher edu- sugar of lead, magnesium sulfate and other com- cation. Only after Dobereiner arrived in Jena mercially valuable products in the Neues uUge- did he learn that he needed a doctorate to occupy meines Journal der Chemie, edited by Adolph the position. He was granted a doctorate on 10th Ferdinand Gehlen (1775-1 8 19,which brought November 1810 at halfthe usual fee and because him to the attention of other chemists. of his poverty was allowed to pay this debt in When Dobereiner lost his licence and his busi- installments. Dobereiner was so grateful for the ness, his relatives gave him a position in charge position that, despite more remunerative offers of bleaching and dyeing in their textile mill, but from five other universities, he remained at Jena the Napoleonic war forced the plant to close. until his death on 24th March 1849. He then began to supervise agricultural estates, but these were discontinued in 18 10, and once Research on Platinum again, the twenty-nine year old father of a fam- Dobereiner’s most significant discovery was ily found himself unemployed and unable to pay an extension of his interest in platinum, which his debts. was necessary for laboratory vessels resistant to At this lowest point in his life, Dobereiner was chemical reagents. As early as 18 12 he began to surprised to learn from the Senate of the extract and isolate platinum metals from two Universitat Jena that he had been nominated to pounds of American platinum ore (5, 6).

Platinum Metals Rev., 1999, 43, (3) 125 by Justus von Liebig and Platinmohr by Dobereiner - both meaning platinum black) prepared by reducing platinum sulfate with boil- ing ethanol, reacted with ethanol vapour and remained white-hot until all the ethanol was consumed (26). In 182 1, after reading Edmund Davy’s article in a German translation which appeared in that year, Dobereiner repeated this experiment and found that the ethanol was oxidised to acetic acid. Because the platinum was not consumed, he suggested that the reaction could be used “for the large-scale preparation of acetic acid” (Essigsuure) (27), and he even designed a vine- gar lamp (Essiglampe), in which ethanol was sup- plied by a cotton wick to a small funnel containing platinum black. He spent the Christmas vacation of 1822 in Weimar with Goethe, who was not only a patron of the natural sciences but also made a number of original scientific contributions (28), and demonstrated these experiments to him. Dobereiner continued to work with platinum black and the finely divided metal Dobereiner’s Feuerseug,the gas lighter in which hydrogen gas, produced by the action of sulfuric acid prepared by ignition of ammonium hexa- on zinc, ignites after passing over platinum sponge chloroplatinate(IV) and extended this work to hanging from a platinum wire. The Feuerzeug was include other vapours and gases, particularly used to light candles hydrogen, which led him to “the most brilliant discovery” discussed above (2-4). In 1823 platinum ores were discovered in the Dobereiner first suggested that the reaction Ural Mountains of Russia, and this new source was “an electrical one, whereby hydrogen forms greatly facilitated his work. Carl August’s court an electrical chain with the platinum”, but he in Weimar had close family connections with later considered it to be “probably of a quite the Czar’s court, and the Grand Duke’s daugh- special nature, i.e., neither mechanical nor elec- ter-in-law, wealthy Russian Grand Duchess trical nor magnetic” (14). In 1835 Berzelius Maria Pavlovna (1786-1859), was a patroness named the phenomenon “catalysis” (29). of Dobereiner and made generous donations of ore to his laboratory (7). Dobereiner’s Platinfeuerzeug In 1816 Humphry Davy (1779-1829) Following this discovery, Dobereiner quickly observed that flammable gases, such as methane applied it to construct the pneumatic gas lighter (‘‘fire damp”), burned without producing a (Diibereinersche Feueneug) that bears his name flame in the presence of platinum, when mixed (30), In this ingenious device hydrogen gas, gen- with air. This was the basis for his invention of erated from zinc and sulfuric acid, streams the miners’ safety lamp, which brought him in through a narrow opening toward a holder in 18 17 the Royal Society’s coveted Rumford which platinum sponge is suspended on a thin Medal for work in the applications of modern platinum wire, whereupon it ignites. The flame science (25). In 1820 Sir Humphry’s younger can then be used to light a candle. If the plat- cousin, Edmund Davy (1785-1 857), found that inum becomes inactive, it can be activated by finely divided platinum (later called platinschwan heating. By 1828 about 20,000 of these lighters,

Platinum Metals Rev., 1999,43, (3) 126 some elaborately ornamented by decorative other families of elements such as sulfur-sele- artists, were in use in Germany and England, nium-tellurium, lithium-sodium-potassium and and they soon became typical objects in many chlorine-bromine-iodine (32, 33). These rela- Biedermeier-style households. However, tionships can also be observed with atomic num- Dobereiner refused to patent his invention, bers as well as atomic weights (34). declaring “I love science more than money, and Dobereiner also discovered the catalytic action the knowledge that with it I have been useful to of manganese dioxide (pyrolusite, Bruunstein) many mechanical artists makes me happy” (4, on the thermal decomposition of potassium 6). chlorate, the basis for the preparation of oxygen Various types of phosphorus matches were sold known to every introductory chemistry student during the 1820s. Those with Ups composed of (35). His discovery that hydrogen escaped from a “percussion powder” of potassium chlorate and a cracked flask (36) led Thomas Graham antimony sulfide and called “friction lights” by (1805-1869) to his law of diffusion (37). In their inventor John Walker (1781-1857) had been Graham’s words, “The original observation of marketed in England since 7th April 1827. By Dobereiner ...will always hold its place in sci- the middle of the nineteenth century these, and entific history as the starting-point of the exper- so-called “safety matches” (Sicherheits- or imental study of gaseous diffusion” (38). schwedische Ziindholzer), which were invented Among his numerous organic experiments, in 1848 by Rudolph Christian Bottger Dobereiner prepared carbon monoxide by heat- (1806-188 l), one of Dobereiner’s students, ing formic acid with sulfuric acid (39) and a began to replace Dobereiner’s lighter. Bottger mixture of carbon monoxide and carbon diox- was originally a candidate of theology, who ide by heating oxalic acid with sulfuric acid (40). became so enthusiastic about Dobereiner’s He also used copper(I1) oxide in organic com- lighter that he turned to chemistry, dedicating bustion analysis (41). He was one of the first to himself to the improvement of the lighter. He observe the fermentative conversion of starch eventually became Professor of Chemistry and paste into fermentable sugar, and he gave a cor- Physics at the Physikalische Verein at Frankfurt rect explanation of alcoholic fermentation (42). amMain (1835-1875) (5,6). In 1831 he found These are only a few of the numerous contri- that the ignition power of platinum sponge is butions that Dobereiner made to the pure and destroyed by ammonia or ammonium sulfide applied science that he loved so much. vapours but that it can be restored by heating. Dobereiner called this property of ammonia Acknowledgements “depotentiating action” (depotenzierende I am indebted to Professor Ernst-Gottfried Jager, Chairman of the Dobereiner Festkolloquium Wirkung). Dobereiner’s lighter was still in use Preparation Committee, Friedrich-Schiller-Universitat at the beginning of World War I (4). Jena, and Diane Majors and Randy Vaughn-Dotta of California State University, Fresno, for assistance in Other Research the preparation of this article. Almost equal in importance to his work on the References catalytic action of platinum was Dobereiner’s 1 W. H. Brock, “The Norton History of Chemistry”, recognition of the relationship between atomic W. W. Norton, New York, London, 1992, pp. 438-439 weights and chemical properties, making him 2 J. W.Dobereiner,J Chi.(Schweiga), 1823,38,321 the first of the many predecessors of Dmitrii 3 J. W. Dobereiner, Ann. Phys. (Gilbert), 1823, 74, Ivanovich Mendeleev and his periodic classifi- 269 cation of the elements. As early as 1817 he 4 P. M. D. Collins, Platinum Metals Rev., 1986, demonstrated that the equivalent of strontium 30, (3), 141 5 W. Prandtl, Chem. Educ., 1950, 21, 176 (42.5) is the arithmetic mean of those of cal- J. 6 W. Prandtl, “Deutsche Chemiker in der ersten cium (20) and barium (65) (31). In 1829 he Halfte des neunzehnten Jahrhunderts”, Verlag extended this so-called “law of triads” to many Chemie GmbH, Weinheim, 1956, pp. 57-77

Platinum Metals Rev., 1999, 43, (3) 127 7 0. Kratz, “Goethe und die Natunvissenschaften”, 26 E. Davy, Phil. Trans. Roy. Soc., 1820, 110, 108 Callwey, Munich, 1992, pp. 146-151 27 J. W. Dobereiner, Ann. Phy. (Gilbert), 1822, 72, 8 0. Kratz, “Faszination Chemie: 7000 Jahre 193 Kulturgeschichte der Stoffe und Prozesse”, 28 K. J. Fink, “Goethe’s History of Science”, Callwey, Munich, 1990, pp. 69, 64, 226-229 Cambridge University Press, New York, 1991; J. 9 J. W. Dobereiner, Ann. Chinz., 1823, 24, 91 Schiff, “Briefwechsel zwischen Goethe und Johann 10 F. von Gizycki, Archiv Ges. Med. (Leipzig), 1957, Wolfgang Dobereiner (1810-1830)”, Weimar, 41,88 1914 11 J. W. Dobereiner, Bibl. Univ. (Genive), 1823, 29 J. J. Berzelius, Juhres-Berichr, 1835, 14, 237 85,54 30 J. W. Dobereiner, “Zur Chemie des Planns in wis- 12 A. Mittasch and E. Theis, “Von Davy und senschaftlicher und technischer Beziehung. Fur Dobereiner bis Deacon. Ein halbes Jahrhundert Chemiker, Medurgen, Platinarbeiter, Pharmaceuten, grenzflachen Katalyse”, Berlin, 1932, pp. 68-76. Fabrikanten und die Besitzer der Dobereinischer Platinfeuelzeuge”, Stuttgart, 1836 13 P. L. Dulong and L. J. Thenard, Ann. Chinz., 1823, 23, 440; ibid.,1823, 24, 380 31 J. W. Dobereiner, Ann. Phys. (Gilberr), 1817,26, 14 J. W. Dobereiner, “Ueber neu entdeckte hochst 332 merkwurdige Eigenschaften des Platins und die 32 J. W. Dobereiner, Ann. Phy. Chenr. (PoggetrdorfJ), pneumatisch-capillare Thatigkeit gesprungener 1829, 15, 301; reprinted in “J. W. Dobereiner und Glaser. Ein Beitrag zur corpuscular Philosophie”, Max Pettenkofer, Die Anfange des naturlichen Jena, 1823 Systems der che,mischen Elemente, nebst einer 15 J. J. Berzelius, Juhres-Bericht, 182311825, 4, 60 geschichtlichen Ubersicht der Weiterentwickelung der Lehre von der Triaden der Elemente. 16 J. J. Berzelius, letter to Gaspard de la Rive, July 23, Herausgegeben von Lothar Meyer”, Ostwald’s 182 1, in “Jac. Benelius Bref‘, ed. H. G. Soderbaum, Klassiker der exakten Wissenschaften No. 66, Kungliga Svenska Vetenskapsakademien,Uppsala, Wilhelm Engelmann, Leipzig, 1895; for an English 1912-1935, Vol. 3 translation see H. M. Leicester and H. S. 17 Anonymous, An/.3. Sci., 1849, [2], 8, 450 Klickstein, “A Source Book in Chemistry 18 F. Henrich, Z. angew. Chem., 1923, 36, 482 1400-1900”, Harvard University Press, Cambridge, MA, 1963, pp. 268-272 19 H. Harries, Apoth. Ztg., 1936, 51, 581 33 M. E. Weeks and H. M. Leicester, “Discovery 20 E. Theis, Z. angew. Chem., 1937, 46 50, of the Elements”, 7th Edn., Journal of Chemical 21 J. R. Partington, “A History of Chemistry”, Education, Easton, PA, 1968, pp. 625-626 Macmillan, London, St. Martin’s Press, New York, 1964, Vol. 4, pp. 178-180 34 J. P. Montgomery, 3. Chenz. Educ., 193 1, 8, 162 22 G. Fuchs, in “Biographien bedeutender Chemiker: 35 J. W. Dobereiner, J. Chenr. Phys., 1820, 28, 247; Eine Sammlung von Biographien”, ed. K. Heinig, Anir., 1832, 1, 236 Volk und Wissen, Volkseigener Verlag, Berlin, 36 J. W. Dobereiner, Ann. Chinz., 1823, 24, 332 1964, pp. 79-83 37 T. Graham, J. Sci. Arts, 1829, 2, 88 23 E. Farber, in “Dictionary of Scientific Biography”, 38 T. Graham, Phil. Trans., 1863, 153, 385 ed. C. C. Gillispie, Charles Scribner’s Sons, New 39 J. W. Dobereiner,J. Chetn., 1821, 32, 345; Ann. York, 1974, Vol. 4, pp. 133-135 Chinz., 1822, 20, 329 24 G. B. Kauffman, in “Academic American 40 J. W. Dobereiner,Ann. Phys., 1817, 26, 331;Atrn. Encyclopedia”, Areth Publishing Co., Princeton, Chim., 1822, 19, 83 N. J., 1980, Vol. 3, p. 227 41 J. W. Dobereiner,J. Chenr., 1816, 17, 369 25 D. Knight, “Humphry Davy: Science & Power”, Blackwell Publishers, Cambridge, MA, 1992, 42 J. W. Dobereiner, 3. Chenr., 1816, 20, 21 3; ibid., Chap. 8 1828,54,412

Noble and Rare Metals: NRM-2000 THIRD INTERNATIONAL CONFERENCE The third in these broad ranging conferences, group metals and their alloys and a broad spec- which take place every three years, is being held trum of their industrial uses and engineering from 19th-22nd September, 2000, at the applications. Donetsk State Technical University, Ukraine. The First Circular and further details on the The conference, which is entitled “Current conference may be obtained from the organis- Status and Strategy of Development in the ing committee, Chairman: Professor Victor A. XXI-st Century” is aiming to cover such topics Goltsov, Donetsk State Technical University, 58 as the geology and refining of the noble and rare Artem Street, Donetsk 340000, Ukraine; e-mail: earth metals; metal recovery, assaying and analy- [email protected]; tel: +380- sis; the science and technology of the platinum (0)622-910-314; fax: +380-(0)622-921-278.

Platinum Metals Rev., 1999, 43, (3) 128 ABS TRA CTS of current literature on the platinum metals and their alloys

PROPERTIES CHEMICAL COMPOUNDS Enhancement of Surface Self-Diffusion of The First Experimental Evidence for the cis- Platinum Atoms by Adsorbed Hydrogen trans Isomerism of Metal Chelates with S. HORCH, H. T. LORENSEN, S. HELVEG, E. EGSGAARD, Oxyazo Ligands I. STENSGAARD, K. W. JACOBSEN, J. K. N0RSKOV and V. A. KOGAN, S. G. KOCHIN, A. S. ANTSYSHKINA, G. G F. BESENBACHER, Nature, 1999,398, (6723), 134-136 SADIKOV and A. D. GARNOVSKII, Mendeleev Commun., STM of H2-promoted self-diffusion of Pt on the 1999, (Z), 82-83 Pt(1 10)-(1 x2) surface has been carried out. An acti- The cis- and mans-isomers of bis(2-hydroxy-4'-methyl- vated intermediate Pt-H complex (1) with diffusiv- azobenzenato)Pt(II) have been isolated and identi- ity enhanced by a factor of 500 at room temperature, fied for the first time. A special feature of the sepa- relative to the other Pt adatoms was observed. Density- ration of the isomers is that the cis form needs to be functional calculations indicated that (1) consists of rapidly removed from solutions because it sponta- a H atom trapped on top of a Pt atom, and that the neously converts into the trans form. The existence bound H atom decreases the diffusion barrier. of the cis structure was proved by XRD analysis. Polymerization and Decomposition of C, on Synthesis, Structure, Chemical Bonding, and Pt(ll1) Surfaces Properties of CaTIn, (T = Pd, Pt, Au) N. SWAMI, H. HE and B. E. KOEL, Phys. Rev. B, 1999,59, R.-D. HOFFMANN, R. POTTGEN, G. A. LANDRUM, (12), 8283-8291 R. DRONSKOWSKI, B. KWENand G. KOTZYBA, Z. Anorg. The interaction of C,, with Pt(ll1) was studied by Allg. Chenz., 1999, 625, (9,789-798 AES, XPS, UPS, HREELS and LEED. At submono- CaTIni (T = Pd, Pt, Au) (1) were prepared by react- layer coverages, C,, is polymerised on Pt(ll1) at 2 300 ing the elements in glassy C crucibles under Ar. (1) K. Annealing multilayer C, flms on Pt(ll1) to t 600 crystallise with the MgCuAl, structure type (space K leads to a C,,, adlayer that is quite different from 1 group Cmcm). Magnetic susceptibility measurements monolayer C,,/Pt(lll). On annealing C," films on of compact polycrystallinesamples of (1) indicate weak Pt(ll1) to 900 K, graphite domains appear on the Pauli paramagnetism. (1) are metallic conductors. surface, and total fragmentation occurs at 1050 K. Synthesis and Characterization of Allyl( p- Temperature-Dependent Segregation on ketoiminato)palladium(11) Complexes: New Pt,:Jth,,(lll) and (100) Precursors for Chemical Vapor Deposition E. PLATZGUMMER,M. SPORN, R. KOLLIR, S. FORSTHUBER, of Palladium Thin Films M. SCHMID, W. HOFER and P. VARGA, SUl$ SCi, 1999, Y.-L. TUNG, W.-C. TSENG, C.-Y. LEE, P.-F. HSU, Y. CHI, 419, (2-3), 236-248 s.-M. PENG and G.-H. LEE, Organometallics, 1999, 18, Surface segregation was studied on Pt,,Fh(lll) (1) (5), 864-869 and PtrjRh,i(lOO) (2) by LEED and LEIS. The Pt Treatment of P-ketoiminates with [(allyl)Pd(p-Cl)], concentration grew continuously on (1) until lOOO"C, afforded volatile, air-stable allyl(P-ketoiminato)Pd(II) whereas it reached a maximum enrichment at - 500°C complexes, which are excellent precursors for the on (2) and decreased thereafter. This contrasting CVD of Pd thin films. In solution 'H NMR analyses behaviour resulted solely from the kinetic limita- indicate either a direct rotation of a planar ally1 lig- tions in the low temperature regime. and about the allyl-Pd axis or a solvent-assisted exchange process involving the transient formation of Superconductivity Mediated by Spin a monodentate ketoiminato ligand. Fluctuations in the Heavy-Fermion Compound UPd2Al, Synthesis of Poly(oxyethy1ene)-Grafted M. JOURDAN, M. HUTH and H. ADRIAN, Nature, 1999, Palladium Clusters 398, (6722), 4749 K NAKA, M. YAGUCHI and Y. CHUJO, Chem. Muter., 1999, Tunnelling spectroscopy has been used to investigate 11, (4), 849-85 1 the superconducting order parameter of a heavy- A polymer-grafted Pd cluster (3-5 nm) was prepared ferniion superconductor: epitaxial thin lilms of UFd2Al,. by stirring an acetic acid solution of Pd(I1) acetate A strong-coupling feature in the tunnelling conduc- and bipyridyl-terminated poly(oxyethy1ene) (bpy- tivity was observed, and when combined with inelas- POE,,& under 1 atm H, at room temperature. The tic neutron scattering data suggested a pairing inter- cluster was soluble in CH2C1,, CHCl,, MeOH, ace- action mediated by anuferromagnetic spin fluctuations. tone and H20. 'H NMR spectra indicated the termi- These induce a presumably d-wave order parameter nal bpy ligand is fixed at the surface of the Pd cluster. without any unconventional symmetry reduction. The calculated formula is Pd,,~,,(bpy-POE,,,,,),~~O-~,,,.

Platinuni Metals Rev., 1999, 43, (3), 129-133 129 PHOTOCONVERSION On-Site Characterization of Electroeryst;lllizecll Platinum Nanuparticles on Carbon and Sol- Self-Assembly of Predesigned Trimetallic Gel Thin Film Modified Carbon Surfaces Macrocycles Based on Benzimidazole as Y. (;uo and A K (iur\D.-\I.UPE, Laiiginuir, 1999, IS, (3), Nonlinear Bridging Motifs: Crystal Structure 759-762 of a Luminescent Platinum(I1) Cyclic Trimer Pt nanoparticles were elcctrocrystallised on amor- s.-w L.AI, M. c.-w. CHAN, S.-M PENG and c.-51. CHE, phous C film and on sol-gel modified C film deposited Aiigew. Chewi. Inr. Ed., 1999, 38, (5), 669-671 on Au mesh grids. These Pt-modified surfaces were Nonlinear N-deprotonated benzimidazole on reac- characterised by TEM and energy dispersive spec- tion with square-planar cyclometalated Pt(I1) pre- troscopy. The particles deposited on bare C surfaces cursors gave cyclic trimers with metal vertices, related exhibited polytetrahedral crystallographic morphol- to calixarenes. [Pt(thpy)(bzim)], (1) was formed from ogy. Subsequently, laterally dendritic growth of Pt [Pt(thpy)(Hthpy)CI] (Hthpy = 2-(2-thienyl)pyridine) formed by aggregation of primary particles (3 to 5 on treatment with Na benzimidazolate. (1) photo- nm) was found on the sol-gel modified C surfaces. luminesces in solution at room temperature. This was reported to be a new type of morphology for electrodeposited Pt with a high surface area. Phosphate Anion Binding and Luminescent Sensing in Aqueous Solution by Fabrication of Poly(diphenylsilylenemetliylene) Ruthenium(I1) Bipyridyl Polyaza Receptors and Poly(dip1ienylsiloxane)Thin Films Using P D. REER~~~I. CADMAN, NcruJ. Chem., 1999,23, (4), Fine Metal Particles 347-349 F KOSSIGNOI., Y. NAKATA, H. NAGi\I, '1'. (IKUTANI. A new class of anion luminescent sensor consisting of M. SUZUKI, N KUSHIBlKl and 51. ,\lUR;\tir\XlI, Cht!iii. a series of new Ru(I1) bipyridyl polyaza receptors was Mare,:, 1999, 11, (2), 358-366 prepared and can bind and detect phosphate and ATP A new technique for the ring-opening polymerisation anions in aqueous solution via MLCT luminescent emis- of I, 1,3,3-tetraphcnyl- 1,3-disilacyclobutane (I) has sion quenching. The receptors were prepared by reflux- been developed. (1) was first evaporated on Si sub- ing bipyidyl substituted amine compounds with (bipy)?- strates and then exposed to metal particle deposi- RuC1,.2HI0 in aqueous EtOH then by HCI addition. tion by sputtering prior to heat treatment. Catalytic activities of Pt, Pt/Pd, Au, Cu and Ag particles were Electronic and Light-Emitting Properties of examined; the metal had no effect on the chemical Some Polyiniides Based on Bis(2,2':6',2''- structure of the film; but the polymerisation efficiency terpyridine) Ruthenium(I1) Complex and film crystallinity depended greatly on the kind of w. Y.NG. x. C;ONG and K'. K. CHAN, Cheni. Muter., 1999, metal, for identical sputtering and heating conditions. 11, (4), 1165-1 I70 Chemical Fluid Deposition: Reactive Novel polyimides that contain the bis(2,2':6',2"-ter- Deposition of Platinum Metal from Carbon pyridine) Ru(I1) complex were synthesised, and their Dioxide Solution optoelectronic properties were studied. The absorp- tion of the polymers at 500 nm was strongly enhanced J. J WATKIXS, J. &I. BLA(:KIIURS and T J. AlCCARTHY, by the Ru complex. The polyimides exhibited elec- Chwr Muter., 1999, 11, (2), 213-215 troluminescent behaviour when the polymer films Chemical fluid deposition was validated for the depo- were fabricated into single-layered LEDs. The exter- sition of CVD-quality Pt metal films on Si wafers and nal quantum efficiency and maximum luminance of polymer substrates via hydrogenolysis of the complex the devices were 0.1 '% and 120 cd m ', respectively. dimethyl(cyclooctadiene)Pt(II) in supercritical CO- at 80°C. This reduction yields continuous metal films on solid substrates and discreet metal clusters within ELECTRODEPOSTION AND the 200 nm pores of an A120,membrane. SURFACE COATINGS The Electrotlepositioii tk Material Properties Structure and Electrochemical Properties of of Palladium-Cobalt PtlC Catalytic Electrodes Manufactured by J. A. ABYS. G. F. HRECK, H K.STRASCHIL, I. BOGUSUVSKY Ion Beam Sputtering and G. HOI.MHOM, Plat. Siri$ Fitid., 1999, 86, (I), B. YANG, s. xu, Y. ZHANG, Y. ZHAO and Y YU, Preciorrs 108-115 Met. (Chbi.), 1999, 20, (I), 14-19 Mechanically stable, mirror-like Pd-Co films with PtiC catalytic electrodes (I) have been prepared by 10-30'%, Co were produced at current densities of < ion beam sputtering. The consumption of Pt in (I) 50 to > 700 mA cm '. In addition, any desired com- was reduced to 0.19 mg cm '. It was established that position can be maintained within k 5% over a wide the Pt films in (I) have f.c.c. structure, and that the range of operating conditions and plating bath age- catalytic activities of Pt coatings on graphite cloths ing. The material properties of the Pd-Co deposits is better than that on C papers. Application of high compared well with Hard-Gold and Pd-Ni finishes, beam voltages and high beam current during ion beam but the Pd-Co alloy was harder and had superior dura- sputtering further improved the catalytic activity of bility. Thus, it proved to be an excellent material for (I) with no degradation after 1000 h working. contact finish applications.

Pluriirrrtir Metals Reu., 1999, 43, (3) 130 Reactive Pulsed Laser Deposition of Iridium Electrochemical Detection of Single-Stranded Oxide Thin Films DNA Using Polymer-Modified Electrodes M. A. EL KHAKANI and M. CHAKER, Thin Solid Films, A. C. ONTKO, P. M. ARMISTEAD, S. R. KlRCUS and H. H. 1998, 335, (1, 2), 6-12 THORP, horg. Chem., 1999,38, (8), 1842-1846 Highly conductive IrOz thin films have been deposited Glassy C electrodes modified by reductive elec- on Si( 100) substrates by reactive pulsed laser abla- tropolymerisation of a thin film of poly[Ru(vbpy),"] tion from an Ir target in an O2atmosphere. At 200 or poly[Ru(vbpy),'+/vba] (vbpy = 4-vinyl-4'-methyl- mTorr of 0, ambient pressure, IrO, films deposited 2,2 '-bipyridine; vba = p-vinylbenzoic acid) were pre- at substrate temperatures in the 400-550°C range are pared. The modified electrodes were active towards polycrystalline and exhibit a granular morphology the oxidation of guanine in solution in both a mono- with average feature size increasing (from - 90 to 170 nucleotide and a polymer. nm) with the substrate temperature. The room temperature resistivities, 39 k 4 @2cm, of these IrO, films compare well with those of bulk single-crystal IrO!. HETEROGENEOUS CATALYSIS Properties and Application Feasibility of an High-Throughput Synthesis and Screening of Osmium-Oxygen Thin Film Prepared by DC- Combinatorial Heterogeneous Catalyst Glow-Discharge Deposition from Osmium Libraries Tetraoxide R. CONG, R D. DOOLEN, Q. FAN, D. M. GIAQUNA, S. GUAN, E. W. MCFARLAND, D. M. POOJARY, K. SELF, H. TURNER H. INOUE and K. SATOH, Bull. Chern. SOC. JPtl., 1999, W. 72, (l), 121-126 and W. H. WEINBERG, Angew. Chem. Int. Ed., 1999,38, (4), 484-488 An 0s-0 thin film (OsOr 1) was deposited by d.c.- glow-discharge from OsO,. The prepared films had a The catalytic activity and selectivity of 120 catalysts homogeneous amorphous structure and 10 ' C2 cm were measured, in < 1 minute, in combinatorial tri- order of resistivity. Since the transparency of a 20 nm angular libraries of Rh-Pt-Cu and Rh-Pd-Cu alloys, thick film was - 80% for visible light, a transparent via the catalytic oxidation of CO and the reduction of conductive film could be obtained on glass or plas- NO, by scanning mass spectrometry. The elements tic substrates. Fundamental properties are reported. of the libraries (- 2 to 4 pg of material) were sputter- deposited in an array, annealed, then heated for test. APPARATUS AND TECHNIQUE Ethyl Acetate Production from Water- Gas Sensor Materials Based on Containing Ethanol Catalyzed by Supported Metallodendrimers Pd Catalysts: Advantages and Disadvantages of Hydrophobic Supports M. ALBRECHT and G. VAN KOTEN, Adv. Mater., 1999, 11, (2), 171-174 T.-B. LIN, D.-L. CHUNG and J.-R. CHANG, Ind. Eng. Cheni. Pt complexes (1) containing a terdentate "pincer" lig- Res., 1999, 38, (4), 1271-1276 and [C,H,(CH,NMe,),-2,6] were synthesised. When Hydrophilic and hydrophobic Pd catalysts were inves- coupled to a dendrimer core consisting of a benzene tigated for the selective oxidation of H?O-containing centre substituted with acid chloride functionalities EtOH in the presence of excess EtOH, a one-step as rigid linkage units, trimetallic macromolecules with preparation of ethyl acetate, in a continuous fixed- 3 diagnostic Pt centres were obtained. Alternatively, bed reactor. The conversion of EtOH catalysed by coupling of (1) to an appropriate AB,branching point Pd/styrene-divinylbenzene copolymer was found to containing a protected phenol and 2 acid chloride be 20 times more than that by Pd/y-AliOl. However, groups prior to the attachment to the core unit yielded it may have been caused by weak metal-support inter- a periphery-functionalised metallodendrimer con- actions and the formation of Pd(I1) acetate. taining 6-adsorption-active metal sites. These metallodendrimers had selectivity towards SO,. Characterization of Model Automotive Exhaust Catalysts: Pd on Ceria and Ceria- Probing Organometallic Structure and Zirconia Supports Reactivity by Transition Metal NMR H.-W. JEN, G. W. GRAHAM, W. CHUN, R. W. MCCABE, J:P. Spectroscopy CUIF, S. E. DEUTSCH and 0.TOURET, card. Today, 1999, W VON PHILIPSBORN, Chenz. soc. Rev., 1999, 28, (2), 50, (2), 309-728 95-105 Pure CeO,, Si0,-CeO,, Ce02-Zr0, solid solutions, Transition metal NMR chemical shifts are readily and Ce0,-ZrO, solid solutions with partial incorpo- measured and serve as a probe into electronic and ration of Pr were prepared and used as supports in steric effects of ligands and substituents in complexes. model Pd automotive three-way catalysts. After age- Quantitative correlations of metal chemical activities, ing, catalysts prepared on the solid solution materi- both experimental and as a result of quantum chem- als provided much more oxygen storage capacity ical calculations, are reported to give new mecha- (OSC) than those based on pure CeO, or SiO,-CeO,. nistic insights and permit reactivity predictions and a Addition of 5 wt.% Pr as a substitute for CeO? screening of homogeneous catalysts. Examples involv- improved the thermal stability of the CeO:-ZrO,, but ing the spin-112 nuclei ""Rh and '"'0s are discussed. did not increase the OSC of the model catalysts.

Platinum Metals Rev., 1999, 43, (3) 131 Combustion of a Trace Amount of CH, in the Supported Ammonia Synthesis Catalysts Presence of Water Vapor over Zr0,-Supported Based on Potassium Derivatives of Anionic Pd Catalysts Ruthenium, Osmium and Iron Carbonyl K. NOMURA, K. NORO, Y. NAKAMURA, H. YOSHIDA, Clusters. The First Catalysts on Carbon A. SATSUMA and T. HATTORI, Catal. Lett., 1999, 58, Support Exhibiting Activity in Ammonia (2, 3), 127-1 30 Synthesis in the Absence of a Specially Added Combustion of a trace amount of CHI over Pd/Zr02 Electron Promoter catalyst was studied under nearly exhaust gas condi- S. hl. YUNUSOV. E. S. KALYUZHNAYA, H. MAHAPATRA, tions (at temperatures 523-773 K) where H,O vapour v. K. PURI, v. A. LIKHOLOROV and v. B. SHUR, 7. Mol. coexists. High catalytic activity was obtained with a Catal. A: Chem., 1999, 139, (2-3), 219-225 ZrO, support calcined at 1073 and 1273 K. Durability K,[Ru,(CO),,], K,[Os,(CO),,] and K2[Fe2(CO)Jcat- tests at 673 K for 100 h revealed that the activities alysts were deposited from THF on graphite-like active of these catalysts hardly decreased, while those of C “Sibunit” followed by drying at 20°C in vacuum. The Pd/calcined A1,0, were much decreased. highest efficiency in NH, synthesis was displayed by In Situ FT-IR Study of Rh-AI-MCM-41 K,[Ru,(CO),,] at 2 250°C (lam). Replacing “Sibunit” Catalyst for the Selective Catalytic Reduction by commercially active C SKT sharply decreases the activity and stability of the catalysts, whereas NH, of Nitric Oxide with Propylene in the Presence synthesis is greatly accelerated on adding metallic K. of Excess Oxygen R. Q. LONG and R. T. YANG,~Phys. Chevn. B, 1999,103, Novel Supported Catalyst for (12), 2232-2238 HydrodesulfurizationReaction Rh/Al-MCM-41(1) was studied for the selective cat- M. WOJCIECHOWSKA, M.PIETROWSKI and s. LOMNICKI, alytic reduction of NO by C,H, in the presence of Chein. Comnzun., 1999, (5), 463-464 excess 0,.(1) showed a high activity in converting RulMgF, (1) was highly active in the hydrodesulfu- NO to N, and N,O at low temperatures. In situ FTIR risation (HDS) reaction. (1) was prepared by con- indicated that a Rh-NO’ species is formed on (1) in ventional impregnation with Ru,(CO),~.The specific flowing NO/He, NO + 0JHe and NO + C,H,, + properties of MgF2 of hardness, resistance to calci- OJHe at 100-350°C. This species is quite active in nation in Oi and well-developed porous structure, con- reacting with propylene and/or propylene adspecies tribute to its use as an active support. (1) is more selec- at 250°C in the presence or absence of 02,leading tive for HDS and much less hydrogenation occurs to the formation of isocyanate species, CO and COr. simultaneously with HDS than when using RulALO,. Study on Sol-Gel Derived Rh-Based Catalysts for Synthesis of C, Oxygenated Compounds HOMOGENEOUS CATALYSIS Through CO Hydrogenation Cross-Coupling Reactions of Hypervalent Y. WANG, Chin. Catal., 1999, 20, (2), 103-108 3 Siloxane Derivatives: An Alternative to Stille Rh/CeOdSiO, catalysts prepared by a sol-gel process and Suzuki Couplings were characterised and studied in CO hydrogenation at 2.0 MPa for the synthesis of C, oxygenated com- M. E. MOWERY and P. DeSHONG, 3 Org. Chem., 1999, pounds. In CO hydrogenation, 2% Rh/SiO, mainly 64, (5), 1684-1688 catalysed the formation of acetaldehyde. Addition Bis(dibenzy1ideneacetone)Pd-catalysed cross-cou- of CeO, increased the selectivity for both EtOH and pling of phenyl, vinyl and ally1 siloxane derivatives was acetaldehyde. CeO, decreased the catalytic activity, found to proceed in good to excellent yield with aryl but increased appreciably the selectivity for MeOH. iodides, electron-deficient aryl bromides, and allylic benzoates. Methyl and 2,2,2-trifluoroethyl siloxanes Hydrodenitrogenation of Pyridine over could be employed in the coupling reaction. Electron- Alumina-Supported Iridium Catalysts donating and -withdrawing groups were tolerated J. CINIRULK~~~Z.vtr, Appl. Catal. A: Gen., 1999, 180, on the aryl halide without affecting the coupling. (1-2), 15-23 Use of Fluorinated Palladium Sources for Ir/AI2O3catalysts obtained from various Ir precur- Efficient Pd-Catalysed Coupling Reactions in sors (Ir(AcAc),, Ir,(CO) ,2, HJrC1, and (NHJJrCL,) were studied in the hydrodenitrogenation (HDN) of Supercritical Carbon Dioxide pyridine at 320°C and 20 bar of pressure in the absence N. SHEZAD, R. s.OAKES, A. A. CLIFFORD and C. M. RAYNER, and presence of a parallel hydrodesulfurisation (HDS) Tetrahedron Lett., 1999, 40, (1 l), 2221-2224 of thiophene. Ir,(CO),, gave the most active catalyst, Pd sources, Pd(OCOCF,), and Pd(F,-acac), with due to fewer contaminants in the stardng Ir compounds fluorinated ligands were shown to be superior to non- rather than to better Ir dispersion. Ir dispersion was fluorinated sources, Pd(OCOCH,), and Pd(dba),, for decreased by sintering in air, substantially decreas- Pd catalysed coupling reactions in supercritical C02. ing the rate of C-N bond hydrogenolysis but with neg- Significantly reduced temperatures and catalyst load- ligible change in the rate of pyridine hydrogenation. ings were possible. The range of phosphine ligands Ir/Al,O? catalysts had much higher HDN activity and used was increased to include PCy, and PBu,, often HDNiHDS selectivity than NiMo catalysts. considered to be poor ligands for coupling reactions.

Platinum Metals Rev., 1999, 43, (3) 132 Biphasic Synthesis of Hydrogen Peroxide from Homogeneous Dehydrosulfurisation under Carbon Monoxide, Water. and Oxygen Ambient Conditions. Harnessing the Facile Catalyzed by Palladium Complexes Zth Polyhedral Rearrangement in thLRuthenium Bidentate Nitrogen Ligands Carbonyl Cluster Ru,C(CO),; D. BIANCHI, R. BORTOLO, R. D'ALOISIO and M. RICCI, A. J. BAILEY, s.BASRA and P. J. DYSON, Green Chem., 1999, Angew. Chem. Int. Ed., 1999, 38, (5), 706-708 1, (l), 31-32 Effective and stable Pd catalysts for the biphasic syn- Reactions of Ru,C(CO),, (1) with H,S affords the thesis of H,O, from CO, 0,and H20are obtained bridged butterfly species (p-H)RujC(CO),,(p-SH) in by using a suitable bidentate nitrogen ligand. The best which H and SH co-ordinate with simultaneous cleav- turnover number (578) for this reaction was achieved age of one Ru-Ru bond and displacement of CO. with a Pd complex with a 2,9-dimethyl-4,7-diphenyl- Subsequent reaction with CO regenerates (1) and 1,lO-phenanthroline ligand. The reaction was carried eliminates Sa and Hi. These reactions take place at out in a biphasic system in which the catalyst is sol- ambient temperatures and pressures. The Ru-S-Ru uble in the organic phase and the produced H,02 is bond rupture is quite facile. The CO in the system soluble in the aqueous phase. The biphasic system is not consumed and can be recycled indefinitely. minimises the ligand oxidation. Room Temperature Operating Allenylidene Unprecedented Efficient Hydrogenation of Precatalyst [L.Ru=C=C=CR,]'X- for Olefin Arenes in Biphasic Liquid-Liquid Catalysis by Metathesis: Dramatic Influence of the Counter Re-usable Aqueous Colloidal Suspensions of Anion X- Rhodium M. PICQUET, D. TOUCHARD, c. BRUNEAU and P. H. J. SCHULZ, A. ROUCOUX and H.PATIN, Chem. Commun., DIXNEUF, New3 Chem., 1999,23, (2), 141-143 1999, (6), 535-536 Ru(I1) [p-cymene(PCy,)CIRu=C=C=CPh2]'X~(X A reduced aqueous colloidal suspension of Rh showed = CF,SO,) (1) was produced from commercial efficient activity for the catalyuc hydrogenation of ben- [RuCl,(p-cymene)] (1) catalyses the ring-closing zene derivatives under biphasic conditions at room metathesis (RCM) of N,N-diallyltosylamide at room temperature and atmospheric H,pressure. The aque- temperatures whereas (X = BF4) (2) favours the cycli- ous phase containing the Rh(0) particles can be reused. sation of the 1,6-diene into a 5-membered hetero- The Rh nanoparticles are protected by hydroxyalkyl- cycle without loss of atoms. The addition of BF,.OEt, ammonium salts containing at least 16C atoms lead- to (2) restores its selectivity in the RCM reaction. (1) ing to electrosteric stabilisation. also promotes the metathesis of an ene-yne to produce the 3-vinyl-2,5-dihydrofuran. Homogeneous Hydrogenation of Maleic Anhydride to Succinic Anhydride Catalyzed FUEL CELLS by Rh Complex Catalyst L. PU, L. YE and Y. YUANQI, 3. Mol. Catal. A: Chem., In Situ and Model EXAFS Studies of 1999, 138, (2-3), 129-133 Electrocatalysts for Methanol Oxidation Hydrogenation of maleic anhydride using various R. A. LAMPITT, L. P. L. CARRETTE, M. P. HOGARTH and homogeneous transition metal complex catalyst sys- A.E. RUSSELL,~Electroanal. Chem., 1999,460, (1-2), tems was investigated. Typical experimental condi- 80-87 tions were: 353-383 K; H, pressure 0.5-2.5 MPa; EXAFS of as prepared Pt/C electrocatalysts for the PPh,:RhCl(PPh,), = 0-16; 0.03 mmol RhCl(PPh,),; DMFC indicated that the preparation of the dispersed 20 mmol maleic anhydride; 8 ml of liquid; and 30-360 Pt by the oxidation of Pt(SO,)," forms dispersed PtO, min reaction time. RhCI(PPh,), was the most active species. After reduction by flowing H, in the gas treat- catalyst precursor for the hydrogenation of maleic ment cell or potentiostatically in the electrochemical anhydride to succinic anhydride. The optimum lig- cell, small Pt particles are formed, shown by the pres- and and solvent were PPh, and ethylene glycol ence of Pt neighbours in the first co-ordination shell. dimethylether, respectively. Immovement in the Diffusion Characteristics RuC12(PPh3)3Catalyzed Isomerization of the of tow Pt-Loaded Electrodes for PEFCs Baylis-Hillman Adducts F. LUFRANO, E. PASSALACQUA, G. SQUADRITO, A. PATTI D. BASAVAIAH and K. MUTHUKUMARAN,S'th. Commun., and L. GIORGI, J. Appl. Electrochem., 1999, 29, (4), 1999, 29, (4), 713-719 445448 The RuCl,(PPh,), catalysed isomerisation of Baylis- Low Pt loading electrodes were obtained by the direct Hillman adducts was investigated. The Baylis-Hillman mixing of electrocatalyst and ionomer (for the cata- reaction typically produces functionalised ally1 alco- lyst layer) and by the introduction of an intermediate hols. Methyl 3-aryl-3-hydroxy-2-methylenepropan- hydrophobic C layer to optimise gas distribution. oates in the presence of RuC1,(PPhJl catalysts were An optimum content of 20 wt.% PTFE in the C layer converted to methyl 3-aryl-2-methy-3-oxopropanoates at a Pt loading of 0.1 mg cm gave, for air operation (- 50% yield) by further reaction. This methodol- at 5 bar absolute pressure and 95"C, a maximum in ogy is a new direction for Baylis-Hillman chemistry. the power density of - 450 mW cm-'.

Platinum Metals Rev., 1999, 43, (3) 133 NEW PATENTS ELECTROCHEMISTRY Powdered Solid Electrolyte MITSUEISHI ELECTRIC CORP. Cathode for Electrolysis Japanese Appl. 101328,286 CSIR COUNCILSCI. IND. RES. us.Patent 5,855,751 Powdered solid electrolyte used in an 0,supply appa- A cathode for the electrolysis of an aqueous alkali ratus is mixed with specific catalysts to form an anodic chloride solution comprises a conductive steel sub- catalyst layer attached to Pt-plated Ti metal and a strate with a three component coating wherein: the cathode catalyst layer of 10-50% PdC. The current first component is Ni oxide, the second is one or more density of the film adhered between the anode and of Rh, Ir, Pd and 0s or their oxides, and the third is cathode is set to 5 0.1 A. The amount of 0, sup- Au and/or Pt oxides, to reduce the Hz overpotential. plied is adjustable and its generation is controlled. The electrode is used for non-mercury chloride cells, Deterioration of the film is prevented. which currently use mild steel cathodes. The coating has catalytic activity and long term stability. HETEROGENEOUS CATALYSIS ELECTRODEPOSITION AND Automobile Diesel Engine Catalyst SURFACE COATINGS MAZDA MOTOR CORP. European Appl. 895,81 OA An exhaust gas purifying catalyst for diesel engines Platinum Plating Bath comprises metal oxide particles containing Ce sup- NIPPON ELECTROPLATING ENGINEERS K.K. porting dispersed Pd oxide particles. A Ce-contain- Japanese Appl. 101330,986 ing coating layer covers the Pd oxide particles. Noble The Pt plating bath contains a Pt compound con- metals are fixed to the oxide by heat treatment. The sisting of a divalent H,O soluble Pt salt of organic catalyst gives enhanced purification and captures acids chosen from saturated mono- or dicarboxylic hydrocarbons in exhaust gas to crack and modfy them acids, hydrocarboxylic acid or urea. The bath improves to higher active hydrocarbons suitable as a reduc- plating velocity and gives high current efficiency. tant for NOx. Stability is enhanced by maintaining neutral pH. Reduction of NOx GENERAL MOTORS CORP. European Appl. 899,002A APPARATUS AND TECHNIQUE A catalyst for promoting the reduction of NOx in Gas Sensor for Automotive Applications the exhaust of a fuel lean operating, hydrocarbon fuelled engine, comprises particles of a mixture of an ARhllNES ASSOC. RECH. DEV. METHODES alkali metal or alkaline earth metal ion exchanged European Appl. 899,563A ZSM-5 zeolite (SiO,:AI,O, t 50) and Pt-Rh/AI20, A gas sensor for use in automotive applications, espe- three-way catalyst. NOx is reduced by cyclically and cially for measurements of CO, NOx and hydrocar- alternately directing the exhaust stream between and bons, comprises a solid electrolyte of P-A1,OI upon through the above two catalyst beds, while cyclically which two electrodes, one made of Au and the other of and alternately injecting hydrocarbon into the beds. Pt, are arranged to be exposed to the gas, a measurement device and a thermo-regulation system. The Rhodium-Tellerium Catalysts response of the sensor to the pollutants can be changed MITSURISHI CHEM. COW. European Appl. 904,836A as a function of temperature, giving improved accuracy. Production of unsaturated glycol diesters, such as 1,4- Platinum Electrode Manufacture diacetoxy-2-butene and butenediol diesters, comprises reacting a conjugated diene with a carboxylic acid and GENERAL MOTORS CORP. us. Patent 5,887,240 0: in the presence of a solid Rh-Te (1) catalyst hav- A Pt electrode for use in a vehicle exhaust gas sen- ing the co-ordination number ratio (Rh-Te:Rh-Rh) sor is made by mixing Pt-, ceramic- and C-powders in the EXAFS at the Rh-K edge of 50-99: 1. (I) has to form an ink which is applied to a green body. The high stability, activity and selectivity. green body is then sintered to form the electrode. The electrode has high porosity and high current Production of Shell Catalyst density, even when sintered at > 1500°C. DEGUSSA A.G. Eirropean Appl. 904,838A A shell catalyst, used for selective hydrogenation of Air Purifier C,H, in gas streams, has a non-porous inorganic sup- A. W AISIN CO. LTD Japanese Appl. 101296,082 port (BET surface area < 80 m' g~')and is prepared A catalyst used as a filter for air purifiers consists of an by drying a suspension of H,O-soluble Ru, Rh, Pd, optically active catalyst carrying 0.01-2.0 wt. parts Os, Ir, Pt, Ag and/or Au compound(s) and a coating of Pd as a photocatalyst for difficult-to-decompose compound on the support and then activating the shell- volatile organic compounds (VOC). The VOC are coated support in a reducing gas stream. Simultaneous quickly decomposed in the gaseous phase under opti- application of active and coating material is simple, cal irradiation at normal temperature. Energy con- giving a shell catalyst with an effective surface, suit- sumption is reduced and catalytic activity is maintained. able for use at high gas spatial velocities of > 3000 h '.

Plarinirwr Metals Rev., 1999, 43, (3), 134-136 134 Production of 1,1,2,2,3-Pentafluoropropane HOMOGENEOUS CATALYSIS ALLIED-SIGNAL INC. US. Patent 5,856,594 Synthesis of Phenol Production of 1,1,2,2,3-pentafluoropropane (1) comprises contacting H, and 1,3-dichloro-l,l,2,2,3-penta- ENICHEM S.P.A. European Appl. 894,783A fluoropropane over a catalyst supported on Al,O,. The Phenol is produced by the catalytic oxidation of ben- catalyst is Pd, Pt, Ru, Rh andlor Ir, preferably Pd. zene and H20zusing Ti silicalite, with H,O, being pre- The reaction is performed in the vapour phase at pared in situ by the reaction of O,, CO and H,O in 185-260°C with a contact time of 10-25 s. (1) is used the presence of: a Pd salt, a nitrogenated ligand and as a refi-igerant, solvent, foam blowing agent or aerosol a non-co-ordinating organic acid. The process is sim- propellant. Very little reduction of the F atoms occurs. ple and has sufficient activity and productivity to be used industrially. Phenol is used to prepare anti- Hydrogenation of Hydroxyaldehyde oxidants, synthetic resins and insecticides. ARC0 CHEM. TECHNOLOGY LP Us. Patent 5,874,652 An aqueous mixture of 4-hydroxybutanal and 3- Production of Unsaturated Alcohols hydroxy-2-methylpropanal is hydrogenated in the MITSUBISHI CHEM. COW. Japanese Appl. 101298,124 presence of Pt-Ru/y-Al,O, catalyst to produce 1,4- Unsaturated alcohols are produced with high yields butanediol, 2-methyl-l,3-propanediol,< 0.01 moles and selectivities by reacting conjugated alkadiene and of tetrahydrofuran per mole of 1,4-butanediol and H,O using a catalyst of a Pd compound and a phos- < 0.1 moles of isobutyl alcohol per mole of 2-methyl- phine. The skeleton of the unsaturated alcohol is 1,3-propanediol. The catalyst is used in a fixed bed obtained by the polymerisation. Of the unsaturated process and has high activity and selectivity. alcohols, octa-2,7-diene-l-ol and other octadienols are used as intermediates for n-octanol or its esters. Bimetallic Catalyst FORD GLOBAL TECHNOLOGIES INC. Preparation of Aromatic Aldehydes US. Patent 5,876,680 TOSOH CORP. Japanese Appl. 101330,307 A bimetallic catalyst used for converting exhaust gases Preparation of aromatic aldehydes (1) comprises react- from a lean-burn engine, especially automotive engines, ing halogenated aromatic compounds with CO and consists ofa porous y-Al,O, support, and 0.1-0.5 wt.% H, in the presence of a catalyst comprising a Pd com- W oxide and 0.5-4 wt.% Pt deposited on the support; pound and tri-terc-butylphosphine and a base. (1) are the amount of metals being based on the weight of the prepared under milder conditions than previously. support. The catalyst has excellent ability to reduce exhaust gases at lower temperatures than prior catalysts. Production of DMUDO Catalyst for Exhaust Gas Purification DEGUSSA A.G. German Appl. 1197130,546 Production of 6,lO- and 6,9-dimethyl-5,1 O-undeca- NE CHEMCAT K.K. Japanese Appl. 11128,359 dien-2-ones (DMUDO) comprises the telomerisa- The base structure of a catalyst for exhaust gas purifi- tion of isoprene with alkyl acetoacetates in the pres- cation consists of a ferritic stainless steel containing ence of a Pd compound, and a P component as the in wt. % 5 0.2 C, 0.4-3.0 Si, _< 2.0 Mn, 13.0-20.0 catalyst system (optionally in the presence of a protic Cr, 0.3-3.0 Mo, remainder Fe and impurities. The additive). The resulting P-keto esters are then saponi- catalyst contains active ingredients chosen from Pt, fied and decarboxylated to produce DMUDO, with Pd and Rh and a y-Al,O, carrier. A CeO, stabilised good, controlled selectivity, for Vitamin E synthesis. ZrOLis supported on the base. The catalyst has excellent corrosion resistance with high adhesion between Rhodium-Based Hydroformylation Catalyst the base and the catalyst. HOECHST A.G. German Appl. 1197140,672 Decomposition of Nitrous Oxide A Rh-based hydroformylation catalyst contains Rh in elemental or bound form, polyethylene glycol, a P- KYOCERA CORP. Japanese Appl. 11/33,401 containing ligand and H,O. The catalyst enables a A catalyst for decomposition of nitrous oxide in exhaust high yield production of aldehydes by reacting 9-18C gases of I.C.E. comprises a spinel crystalline multi- olefins with H, and CO. The organic phase and the ple oxide of 0.5-20.0 wt.% Pd, and Ga and Ni. About aqueous catalyst phase can be rapidly separated, with 5-75 wt.% CeO, is added to the multiple oxide. NO no significant loss of Rh or ligands in the organic phase. is decomposed into N2and 0, without using a reducing agent, thus saving energy. FUEL CELLS Cyclohexanone Compounds BAYER A.G. German AppL 1/97/27,7 12 Platinum Alloy for Fuel Cell Electrodes Cyclohexanone compounds (1) are prepared in con- EXXON RES. & ENG. CO. European Appl. 899,348A sistent high yield by the catalytic hydrogenation of A C-supported, Pt-dispersed Zn alloy for fuel cell phenol compounds using PdlC catalyst pre-mixed electrodes has 10-40 wt.% Pt particles, 20-30 A in with a base component and H,O, at 100-250°C and size, on a C support of surface area 100-500 m' g I. 1-20 bar H2 pressure. (1) include intermediates for A soluble Zn source is deposited on the PdC, and is pharmaceuticals and plant protectants and is obtained calcinated and reduced to Zn. The alloy has good CO with high selectivity and in good reproducible yields. tolerance and can oxidise CO at low potentials.

Platinum Metals Rev., 1999, 43, (3) 135 Phosphoric Acid Type Battery Thick Film Conductor TOSHIBA K.K. Japanese Appl. 101334,928 SANKEN DENKI K.K. Japaiiese Appl. 11131,872 The anode plate of a PAFC has a transition noble A Ag-Pd thick film conducting paste for hybrid IC metal alloy catalyst layer and a Pt catalyst layer on is printed and baked on a circuit board forming a thick corresponding sides of the oxidation-gas outflow and conductor layer of 93.4-99.5 wt.% Ag and 0.5-6.6 the inflow side of the reservoir. The PAFC reduces wt.% Pd. A Ni layer is formed on the conductor layer. the current density distribution gap, the amount of by non-electrolytic plating and an Al wire is bonded phosphoric acid used and the phosphoric acid vapour to the Ni layer using ultrasonic oscillation. The con- on the oxidation-gas outflow side. nection strength is improved and embrittlement of the conductor layer is prevented. Solid Polyelectrolyte in DMFC JAPAN STORAGE BATTERY CO. LTD Perovskite Structured La-Sr-Ru Oxide Japanese Appl. 11116,588 FUJITSU LTD. Japanese Appl. 1 1153,935 A polyelectrolyte used in DMFC consists of a dou- A thin film electrode of perovskite crystal structure, ble layered negative electrode catalysed layer. A Pt La& ,RuOi, x = Gl, is formed on a Si board by sput- layer is formed on the inner side of the polymer elec- tering a target of SrRuO, and La. It is used as an electrolyte film. Another layer containing Pt and Ru is trode of a ferroelectric random access memory. The formed on its outer side. The amount of waste cata- film may be deposited on a Pt coated substrate. lyst not participating in the reaction is reduccd. Sputtering Target Manufacture Double-Layer Capacitor TANAKA KIKINZOKU KOGYO K.K. SIEMENS A.G. Gerniaii Appl. 1197124,712 Japanese Appl. 11161,392 An electrochemical double-layer capacitor (1) has a Ru for sputtering targets for the formation of Ru thin porous double-layer electrode made of C containing film is manufactured by melting Ru powder on a plate an electrolyte of poly(pefluoroa1kyl)sulfone acid, and several times. A highly pure Ru ingot of > 99.9% purity a porous H electrode made of Pt or a Pt alloy. The is formed by cutting the plate. The Ru thin films are contact layers are C paper. (1) is used in combination use in the manufacture of semiconductor devices. with PEMFC for electrotraction. It has a high capac- Bubbles of H, and O2 gas formed on the film are ity in relation to volume and weight. removed together with impurities. Thin Film Magnetic Head ELECTRICAL AND ELECTRONIC YAMAHA COW. Japaviese Appl. 1 1166,514 ENGINEERING A thin film magnetic head for a magnetic recording Piezoelectric Actuator disk has a Pt spacer layer interposed in the multilay- ered magnetic core along the width direction of the 'I'OYOTA CHUO KENKYUSHO K.K. magnetic layer. Magnetic field response occurs to high Japanese Appl. 101273,361 frequency, thus stratification becomes simple and A composition for a piezoelectric (PZT) actuator complicated manufacture is avoided. includes PZT ceramic with added precipitated Pt, Pd, Rh, Ru, Os, Ir or Au. Precipitation from solution Ruthenium-Doped Seniiconcliictor occurs on the ceramic by heating and baking. Excellent D. BIMRERG El' AL Gernian Appl. 1197147,996 displacement characteristics are obtained at lower Epitaxial production of Ru-doped semi-insulating III- cost, due to lower amounts of metal being used. V compound semiconductors is achieved using a Optical Recording Medium Group V precursor having < 3 H bonded directly to the Group V element. The Ru layer is highly ohmic KAO COW. Japanese Appl. 11125,515 on both electron and hole injection and has low capac- An optical recording medium, such as for optical disks, itance to avoid degradation of h.f. properties. has an optical reflex layer of Ag-Ru alloy, containing 0.5-20 at.% Ru laminated with a protective layer on a substrate. About 0.1-10 at.% of Rh, Pd, Ir or Pt MEDICAL USES are included in the alloy layer. The medium has a Ceramic Material Composition high reflecting rate and improved service life. The chemical stability of the optical layer is improved. NIPPON HASHII'OKUIIYOKU K K Japanese Appl. 1111,738 Structure of a Semiconductor Electrode Ceramic material for artificial teeth contains in wt.%l: FURL'KAWA EIECTRIC CO. LTD. 19-20 Au, 19-30 Pd, 9-20 Cu, 0.02-0.03 Ir, 0.44.5 Japatiese Appl. 11126,396 Sn, 0.5-4.5 Ga, 33-48 Ag, and impurities; the total amount of Sn and Ga is 2-5 wt.O/. The alloy has excel- A p-type compound semiconductor electrode has lent heat conductivity and improved chemical an laver partially formed on an insulating layer cov- Al stability, and wear- and corrosion-resistance. ering a Pt layer, and a Ti or Cr layer which are on the exposed surface of the semiconductor. Peeling of the electrode boundary surfaces and the insulating The New Patents abstracts have been prepared from layer is prevented during wire or die bonding. material published by Denvent Information Limited.

Plariiiziiri Metals Reu., 1999, 43, (3) 136