Platinum Metals Review

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

VOL. 45 JANUARY 2001 NO. 1 Contents Molecular Design for Long-Range Electronic Communication 2 between Metals By Yoshimasa Hoshino Rapid Synthesis of Colloidal Clusters 11 New ProCat2 Process Catalyst Plant 12 By B. Harrison Organometallic Chemistry and Applied Catalysis 13 By Simon Duckett Chemical Fluid Deposition of Conformal Palladium Films 14 The Rutheniutn/TEMPO-Catalysed Aerobic Oxidation of Alcohols 15 By Arne Dijksman, Isabel W. C. E. Arends and Roger A. Sheldon Techniques for Catalyst Manufacture 20 By P. J. Collier, M. R. Feaviourand M. J. Hayes Heterogenised Rhodium Catalyst 21 Ferrocenyl Phosphine Complexes of the Platinum Metals 22 in Non-Chiral Catalysis By Thomas J. Colacot The 2000 MacRobert Award for the Platinum CRY 30 By R. J. D. Evans 21st Century Emissions Technology 31 By J. P. Warren Palladium Cross-Coupling Reaction for Brain Tracers 33 Improved Start-Up for the Ammonia Oxidation Reaction 34 By K 1. Chernyshev and S. V. Zjuzin Ammonia Reactions on Ruthenium 40 Glass Conference in Vehky Novgorod 40 Abstracts 41 New Patents 45

Communications should be addressed to: The Editor, Susan V. Ashton, Platinum Metals Review, [email protected] Johnson Matthey Public Limited Company, Hatton Garden, London ECIN 8EE Molecular Design for Long-Range Electronic Communication between Metals POLYYNE AND ETHYNYLATED AROMATIC SYSTEMS AS MOLECULAR WIRES IN BINUCLEAR RUTHENIUM P-DIKETONE COMPLEXES By Yoshimasa Hoshino

Department of Chemistry. Faculty of Education, Nagasaki University, 1-14 Bunkyo-rnachi, Nagasaki 852-8521, Japan

To construct molecular devices it is necessary to use mixed-valence metal complexes which have a large metal-metal separation distance and which exhibit strong coupling between the metals, so that errors which might arise from electrostatic interaction between the metal ions are prevented. Bridges, or spacers, are needed between two metal terminal sites to operate as effective molecular wires when one metal terminal site is in the excited state, and/or when both the terminal components are in the ground state. Binuclear ruthenium complexes, consisting of tris(P-diketonato)rutheniurn(III) units, which are suitable as the terminal redox sites, can be used to evaluate how well the bridges function as molecular wires in the ground state. This is because their Ru(III)-Ru(II)and Ru(IV)-Ru(III)mixed-valence states are accessible for experimental use. In this article, a polyyne system and an ethynylated aromatic system are evaluated as molecular wires, using the binuclear (P-diketonato)ruthenium(llI) complexes containing these systems as the bridges. In the Ru(IV)-Ru(III)mixed-valence state, the ruthenium complexes show relatively strong electronic interactions between the metul centres. This is interpreted by a superexchange (through-bond) hole transfer mechanism via the highest occupied molecular orbitals of the bridge. Molecular orbital calculations provide a guide to the molecular design of bridging ligands for long-range electronic coupling.

Mixed-valence binuclear complexes have been remains ‘valence trapped‘ or charge localised. In actively studied since 1969 when Creutz and Taube the Class I11 system, the coupling is so large that reported the fascinating mixed-valence ion, the properties of the isolated mononuclear com- [~H3)5Ru~-pz)Ru(NH3)5]5+@z = pyrazine), the plexes are absent and only new properties are so called ‘Creutz-Taube ion’ (1). Studies on mixed- discerned. This is the delocalised case. valence complexes are closely related to the We can estimate the extent of the metal-metal kinetics of electron transfer reactions, and provide interactions by the stability of the binudear com- valuable information on the degree of interaction plex formed in a ‘comproportionation’ (reverse of between two metal sites. In such studies, three disproportionation) reaction, in which the oxida- dasses of symmetrical binudear systems may be tion numbers of the metals mix. The com- distinguished, depend.tng on the degree of the elec- proportionation reaction for the Class I1 system is: tronic coupling between the two metal ions (2,3). M(Z+l)-M(Z+l) + M(Z)-M(2) In the Class I system, the electronic coupling is

KC so weak that the mixed-valence complex exhibits 2 v- N(Z+l)-M(z) (i) only the properties of the isolated mononudear complexes. The Class I1 system has electronic cou- where M represents the metal and Z the oxidation pling to some extent, so the mixed-valence number. The comproportionation constant (equi- complex exhibits slightly perturbed mononudear librium constant of Equation (i)), K,, and the free characteristics but also has obvious properties not energy change for the comproportionation, AGc, associated with the isolated units. This system are calculated from the difference in the reversible

Phtinwn Metah Rev., 2001,45, (l), 2-11 2 c. 1-2 nm

bridging ligands connecting connecting spacers

P-diketonate molecular wire terminal redox site electrons terminal* redox site I < holes

I Fig. I Scheniatic diagram of the moleculur wire system showing its structure; the ruthenium centres, which are terminal redox sites, are connected via the Pdiketonate moieties with eihynyluted aromatic/polyyne groups as the spacers. In this svstem electrons move to ihe right and holes to the lefi half-wave potentials between the two reduction metal-metal distances which show strong metal- potentials AEw = (EI/z(~)- E~42)). metal couplmg is needed to gather information about electron transfer in inorganic and biological M(Z+l)-M(Z+l) + e- = M(Z+l)-M(2) Ellz(1) (ii) systems and to aid construction of molecular M(Z+l)-M(Z) + e- = M(2)-M(2) E1/2(2) (G) devices. In constructing molecular devices the K, = exp(A&/Z FIRT) 09 through-space distance between the donor and AGc = -AEi/2 F (4 acceptor should be big (not the through-bond dis- The fiee energy change of the comproportiona- tance) in order to prevent errors arising from any tion, AG,, is expressed by the Equation: electrostaticinteraction. Mixed-valence ruthenium complexes have been reported, which despite hav- AG, = AG, + AG, + AGi + AG, ing a metal-metal distance d(M-hl) > 1.0 nm, have where AG, is an entropy factor, AGe is an electro- relatively strong metal-metal couplmg, that is, large static factor arising from the repulsion of the two comproportionation constants (Kc > lo3) (4b, 5). similarly charged metal centres, AG is an inductive However, to the author’s knowledge, large K, val- factor dealulg with the competitive coordination ues have never been reported for any binuclear by metal ions for the bridgmg Itgand, and AGr is complex (not an organometallic compound) with a the free energy of resonance exchange which rep- metal-metal distance d(k-M) > 2.0 nm. resents the actual metal-metal couplmg (3,4). One of the aims of our research, therefore, is to For a strongly coupled system with a large produce a guide that can be used in the design of metal-metal distance (d(M-w > - 1.5 nm), the molecular bridgmg Wdswhich will be able to resonance exchange term (AGJ dominates AG,, achieve good metal-to-metal communications because the electrostatic factor (AGJ exponential- over a long metal-metal distance. ly decreases with the increasing charge separation, the entropy factor (AG,) has a constant value of Spacers between the Metal -RTln4, and the contribution of the inductive fac- Terminal Sites tor (AG,) is generally small. In such a system the The polyyne system is one of the most effective degree of the metal-metal coupling can be estimat- spacers for potential long-range electronic com- ed by the K, value. munication between two redox centres. In fact, Thus the value of the comproportionation con- butadiyne (C, spacer)- and octatetrayne (C, spac- stant K, is important for the design of bridgmg er)-bridged diiron organometallic compounds, Wds.Studying mixed-valence systems with large where the polyynes directly connect to the metal

Phmm Met& Rm,2001,45, (1) 3 (CHzCO)2NI HCECSiMe3 L2R?$ Pd(PPh3),,or - ‘0 -Cul, Et3N Me M~ PdC12(PPh3)2 1

Me Me

Me Me 3

HC=CSiMel L2R/{C=C-CZCSiMq n-BuqNF/THF

CUCI-TMED, O2 ‘0 Me

L =[Me3CCOCHCOCMe3]- LzR[$ CEC-C=CH 0 TMED- N, N, N: N’-tetramethylethylenediamine Me

Scheme I Introducing an ethynyl group into a Pdiketonate chelate and oxidative coupling of ethynyl compounds showing how ethynyl links can be used for elongation for wires

centre, exhibit quite large K, values: 1.60 X 10” for polyyne system P-diketonate was chosen as the the C4 spacer and 2 x lo7 for the Cg spacer (6). connecting moiety because the P-diketonate Furthermore, the Clz and Cj6 ppolyynediyl dirhe- chelate has aromaticity and apn conjugated sys- nium complexes exhibit two one-electron tem, which can interact with the dn orbitals of a oxidation steps in their cyclic voltammograms: for metal centre. The distance between a metal and a the Ctz spacer AEllzis 0.19 V, and for the C16 spac- terminal carbon of the polyyne bridge (at the y- er AEllz is 0.09 V (7). However, ethynyl and position of a P-diketonate ring) is shorter than any butadiynyl bridges actively promote long-range involving pyridine rings used previously (except at electronic couplrng between remote cationic units carbons adjacent to ligating nitrogen atoms). Thus, when illuminated with visible light (8). we chose tris(P-diketonato)ruthenium(III)units as It has not been proved that the polyyne system the redox sites. These can be electrochemicallyoxi- in the ground state of mixed-valence systems, dised and reduced to give ruthenium(W) and where polyynes indirectly connect to the metal rutheniumQI) species (11). Therefore, the degree centre, operate as molecular wires between the of interactions between two redox sites bridged by redox metal sites; the K, values of the diruthenium a polyyne system and an ethynylated aromatic sys- complex bridged by bis(4pyridyl)acetylene (9) and tem in two kinds of mixed-valence states, of the ruthenium and osmium polypyridyl com- Ru(IV-Ru(III) and Ru(III)-Ru(II), can be found. plexes linked by bridging polyynes (10) are very small. Syntheses of Binuclear Ruthenium The functioning of the polyyne system as mol- Complexes ecular wires in the ground state of mixed-valence Because of the quasi-aromatic reactivity of the complexes depends on the characteristics of the ?I-methyne of a P-diketonate chelate ring, it should connecting moiety between the bridges and the be possible to introduce an alkyne group at the ?I- metal centres, see Figure 1. To evaluate the position. No such synthesis has yet been described,

Phhnxm Met& Rev., 2001,45, (1) 4 Me Me

I Me Me n-ZforRuZRu, 3fwRu3Ru, 4 tor Ru4Ru , Me 5

3 Me

L :[MejCCOCHCOCMe3]- RuAnRu TMED = N. N, N', N'- tetrarnethylethylenediamine

Scheme I1 Binuclear linked complexes can be prepared by coupling reactions of the ethynylated ruthenium complex with the analogous complex, halogenated thiophene, or anthracene although a wide variety of y-substitution reactions single crystals of these complexes has often been are known, for example, halogenation, nitration attempted, but insufficient crystals for X-ray struc- and acetylation (12). We have successfdy intro- ture analysis have been obtained. duced an ethynyl group into this y-position, using Sonogashira reaction-type palladium catalysts (13). Electrochemical Properties Ethynyl links can be elongated by oxidative cou- A typical cyclic voltammogram of a binudear pling (14), see Scheme I, (15). Binuclear ruthenium complex (RuAnRu) is shown in Figure complexes, including ethynylated thiophene- 2. The two pairs of peaks on the positive side of bridged (S) and anthracene-bridged (An) the voltammogram correspond to two consea- complexes, can be prepared by similar couplmg tive, Nernstian, one-electron oxidation steps (one reactions, see Scheme 11, (16). These complexes pair of peaks (A and D) corresponds to the Ru"- have been characterised by 'H NMR and IR spec- RU"/RU"-RU'" couple, and the other pair of peaks troscopies and by mass spectrometry (13,16). The (E3 and C) correspond to the RU"-RU"/RU"-RU~ 'H NMR spectra of these binudear complexes couple). The pair of peaks @ and F) on the nega- show paramagnetic shift because of an unpaired tive side can be assigned to two overlapping electron in the Rum metal centre, and do not con- one-electron reduction processes. The reduction tradict the spectra derived from the expected steps of RuAnRu and RuSRu can be assigned to structure. the reduction of the metal centres, while the oxi- The IR spectra show the characteristic CS dation steps correspond to metal-based oxidation stretchmg vibrations in the region from 2100 to and not to llgand-based oxidation (16). Values for 2200 cm-'. In their FAB mass spectra, the the reversible half-wave potentials (Ellz), K, and observed parent peaks correspond to the molecu- for the estimated metal-metal distances in the lar weight of these binudear complexes. Preparing complexes are given in Table I (13, 15, 16).

PMmmMetulr h.,2001, 45, (1) 5 Fig. 2 The cvclic r.oltanimogrum for .-U RuAnRu IN 0.1 mol U e dni ' oj (CdHu),NBF,- CH2C12011 a platinirrn disk electrode at 25°C. The sweep rate ~tas 1 0.1 vs' 0

UI 5 g 3

I -1.0 0 10 (E vs. AglO 01 rnol drn-3 AgNOl In CH3CN), V

Five oxidation states, includtng the original oxi- statistical limit (Kc = 4). This indicates that the free dation state of these binuclear complexes, are energy change of the comproportionation, electrochemically accessible as expected: Ru(II)- AGQI, II), which is the stabilisation of the Ru(II), Ru(IIQ-Ru(II), Ru(III)-Ru(III), Rum- Ru(I1I)-RuQI) mixed-valence system, is small, and Ru(I1I) and Ru(lV)-RuO. The bridgmg ligands also that the electron resonance exchange term, containing the polyyne and the ethynylated aro- AG,(III, 11) is only a minor factor contributing to matic groups can now be evaluated as molecular AGJII, 11), see Equation (vi). On the other hand, wires in the two mixed-valence states, Rum- AG,(IV, III) is a major factor contributing to the Ru(III) and Ru(III)-RuQI). AG,(IV, 111) of the Ru(IV)-Ru(I1I) system. Therefore the degree of the electronic coupling K,Values for the (111,II) between the metal centres in the Ru(lV)-Ru(lII) and (IV, 111) States state is much larger than that in the Ru(III)-Ru(II) The KQI, Il) values are significantly smaller state. than the K,(IV, 111) values; K,(III, 11) values of In the present systems, see Figure 3, it is ener- Ru3Ru and Ru4Ru in particular are close to the getically favourable for a hole to move from the

Table I Reversible Half-Wave Potentials ( EIIp),Comproportionation Constants (Kc)and Estimated Metal-Metal Distances (d(M-M)) of Various Binuclear Ruthenium Complexes

Complex Rul"/Ru"l Kc(lV, Ill) Ru"~/Ru" KC(III, II) d(M-M),

612, AEin, €112, Ah nm V mV V mV

RuAnRu 0.280, 0.463 183 1200 -1.344, -1.424 80 22 1.71 RuSRu 0.383, 0.558 175 900 -1.334, -1.41 4 80 22 1.67 RuPRu 0.396, 0.621 225 6360 -1.361, -1.472 111 75 1.31 Ru3Au 0.465, 0.589 124 125 -1.31 9, -1.372 53 8 1.56 Ru4Ru 0.516, 0.602 86 28 -1.260, -1.31 5 55 8 1.82

Phtintn Met& Rev., 2001, 45, (1) 6 (A) Electron transfer via WMOS RU~"RU" System LUMOs (spacer) -l- L c3 #}

Fig. 3 Superexchange mechanisms for the intramolecular transfer of electrons and holes. Electron transfer is shown from the dn6 Ru(l1) site via the lowest unoccupied molecular orbitals (LUMOs) of the bridge to the dx5Ru(ll1) site. Hole transfer is shown from the dn4 Ru(1V) site via the highest occupied molecular orbitals (HOMOs) of the bridge to the ddRu(ll1) site dn orbital of the ruthenium0 site to one of the starting material for the polymerisation (18) and ruthenium(III) sites via the highest occupied mol- (c) their electrochemically reduced products, ecular orbitals (HOMOs) of the bridge in the poly-p~"(mEma)~]-and [Run(mEma)3]-. ground state of the RuO-Ru(TII). On the other To our surprise, spectroelectrochemical mea- hand, in the RuO-Ru(n>system, electron transfer surements showed that the visible spectra for the from the ruthenium(Il) site to the ruthenium(I1I) poly-[Ru"(mEma)3]- (new band at 499 nm) and the site via the lowest unoccupied molecular orbitals pun(mEma)3]- (new band at 497 nm) are approx- (LUMOs) of the bridge is favourable. Such a hole- imately the same. The new band of pu"(mEma)3]- or electron-transfer mechanism is called a is assigned to metal-to-ligand charge transfer 'through-bond' mechanism and often called the - a transition from the metal dx level to 'superexchange' mechanism (17). the ligand &ma- R* orbitals, while the new band The large difference between the AG,(IV, 119 of poly-[Ru"(mEma)3]- comes from the combina- and AGr(III, Il) indicates the large difference tion of two of the MLCT bands; one band between the degree of electronic couplulg for the corresponds to transitions from the dn levels to hole transfer and for the electron transfer. This the terminal mEma- R* orbitals and the other is large difference between hole and electron transfer transitions from the dn levels to the bridging can be interpreted by the difference in character of +d, the tahdf 7c' orbitals (tahdf- = 1,1,6,6- HOMOs and LUMOs of the bridging eds,as tetraacetyl-2,4-hexadiynatedianio;). In spite of the mentioned below. combination, the shape of the absorption bands of Recently, we have prepared the following: poly-~u'(m~rna)~]-are consistent with those of (a) a new metal coordination polymer of rutheni- [Ru"(mEma)3]-: both bands have a shoulder near um(III) p-diketone units linked by a butadiyne 460 nm. With this observation, it is possible to bridge; predict that the energy levels of the tahdf R* @) a mononuclear complex p~"'(mErna)~] orbitals are approximately equal to those of the (&ma- = 3-ethyn$-2,4-pentanedionate ion) as the mEma- n* orbitals.

Pbtinrrn Metah Rev., 2001,45,(1) 7 c-0

c-0 Me’o d

LUMO LUMO -8.21 eV -8.20 eV

Fig. 4 Schematic of the lowest unoccupied molecular orbitals (LUMOs) of [Nrr(mEnin)]md [Nndtuhrl~)]

To conk this prediction, extended Hiickel rate will be fast) and superexchange theory (Sc, 20): molecular orbital (EHMO) calculations were car- -AGr = 2H,b2/h ried out for pa(mEma)] and [Na&~hdy)] as (vii) Hab = (H& exp[-PR/2] (viii) model compounds for [R~(rnEma)~]and poly- Hab = Ca.Cp/8E (k) [Ru(mEma)3], respectively (18). The calculations show that the LUMO energy level of [Naz(tahdy)] Here, AGf depends on the electronic coupling is approximately equal to that of pa(mEma)]. matrix element, &,,where (&)O is the matrix ele- Both of the LUMOs have a node on the 3-position ment when donor and acceptor orbitals are in carbon atom of the P-diketone ring, see Figure 4, contact, and h is the reorganisation parameter; p so that there is no wavefunction on the ethynyl reflects the efficacy of the medium during donor- carbons of [Na(mEma)] or on the butadiynyl car- acceptor coupling and R is the length of the bridge; bons of FJaz(tahdy)]. Therefore, the LUMO of c, is the atomic orbital coefficient for the couphg paz(tahdy)] is essentially the same as that of between the donor and the bridge, and cp is the pa(mEma)]. On the other hand, the 7c-conjugated atomic orbital coefficient for the coupling between system in the second highest occupied molecular bridge and acceptor; 6E represents the energy gap orbital (SHOMO) of paz(tahdy)] is extended between the appropriate orbitals on the through the entire bridging ligand (18). donor(acceptor) and the bridge. Consequently, the atomic orbitals of the ethynyl For the homologous series of RunRu (n = the bridge do not contribute to the LUMO of the number of ethynyl groups = 2,3, and 4), the Kc(IV, tahdq- bridging ligand. The LUMOs of the other 111) values decrease exponentially with the increas- analogous tetraketonate bridging hgands in this ing number of ethynyl bridges; in particular, the study should have a node, so the superexchange Kc(IV, III) value for Ru4Ru is close to the corre- would not operate for electron transfer via sponding Kc(III, 11) value (15). This result is in LUMOs of the bridge in the ground state of the accord with the distance, R, dependence of Hab Ru(III)-RuO systems. (Equation (viii)) (21). Thus, strong electronic coupling is not expected for the RunRu system when Metal-to-Metal Communication n > 4 with polyyne as the bridge and the p-diketo- in the Ru(1V)-Ru(II1) State nate chelate as the connecting moiety. Therefore, Accordmg to the Marcus-Hush theory (19) an increase in the K,W, IIl) value with decreasing (which links the rate of electron transfer of elec- 6E was planned by inserting another conjugated trons &om one molecule to another, or from part moiety with electron-donor ability, that is thio- of a molecule to another, in terms of structural phene and anthracene units, into the ethynyl changes in the molecule. For a large molecular bridges (16). rearrangement the rate of electron transfer will be In fact, although the d(M-M) of RuAnRu (1.71 slow, while for small molecular rearrangements the nm) and RuSRu (1.67 nm) are both longer than

PIatinrrm Mezizh Reu., 2001,45, (1) 8 Table II Values of the SHOMO Energy (Eh), the Sum of Squared Extended Huckel MO Coefficients at the Terminal Carbons (C(1)) of the Triple Bond in Tetraketones, Cc,', and Square Roots of the Natural Logarithms of the Cornproportionation Constants (Kc) of Various Binuclear Ruthenium Complexes

H2BL (X)* Eh, eV XC12 Complex MK,( IV, III) tln

HzAn (CI4He) -10.60 0.1 96 RuAnRu 2.67 HzS (CIHZS) -10.83 0.1 85 RuSRu 2.61 H22 (none) -1 1.22 0.1 98 Ru2Ru 2.96 H23 (Cz) -1 1.22 0.158 Ru3Ru 2.20 H24 (C,) -1 1.22 0.138 Ru4Ru 1 .83

*BL denotes bridging ligand that of RdRu (1.56 nm), the K$V, III)values for the brimllgands in the complexes, are given in RuSRu and RuAnRu are larger than that for Table 11 (22). The n-conjugated system in the Ru3Ru by a factor of about 10. This indicates that SHOMO of H2S is extended through the entire metal-to-metal communication in the RuO- bridgmg llgand, see FigUte 5. The SHOMO energy RU~mixed-valence state, that is, the electronic levels of H& and H2S are lugher than that of coupling, is amplified by inserting other conjugat- H23. From these calculations we can foresee that ed moieties with electron-donor ability into the the energy gap between the dn orbitals of the metal two ethynyl groups. This amplification seems to be centres and thepHOMO of the brim+ds caused by decreased SE,due to the presence of the in RuAnRu arid RuSRu becomes smaller com- electron-donor groups in the bridge. This can be pared with that in Ru3Ru. confirmed by EHMO calculations for a series of On the other hand, the SHOMO energies (Eh) tetraketones, HzBL, whose dianions are net bridg- of the HD system, see Table II, are in good agree- ing ligands (BL). The SHOMO energies (Eh), ment with each other (= -11.22 ev) and are which correspond to thepn HOMO energies of constant. This result predicts that the energy gap

SHOMO -10.83 eV

Fig. 5 Schematic of the second highest occupied molecular orbital (SHOMO) of H2S. The n-conjugated system in the SHOMO of HzS is extended through the entire bridging ligand

Pkdnnm Me&? REX, 2001,45, (1) 9 carbons (C(1)) of the mple bond in the tetraketones. This relationship can thus be used as a guide RuPRu . / for the molecular design of mixed-valence (tetra- ketonato)diruthenium complexes with long-range hole transfer.

Conclusions The evaluation of a polyyne system and an ethynylated aromatic system as molecular wires using binuclear ruthenium P-diketone complexes has been discussed. Binuclear species based on / tris(P-diketonato)ruthenium(IIr) units can be used 2 0.14 0.16 om 0.20 , k,’ to evaluate bridges as molecular wires as their RuQII)-RuO and RuQV-RuQIl) states are exper- Fig. 6 The linear relationship between the square root imentally accessible within the potential window of of1nKc(N III) values, for various hinuclear ruthenium complexes, and the sum of the squared extended Huckel common supporting electrolyte solutions. The bin- MO coeflcients Ec,’ in SHOMO at the terminal carbons uclear complexes are also useful for inveswting (C(1))of the triple bond in tetraketones, is clearly seen. This relationship can be used as a guide for designing the superexchange mechanism, as the absence of molecular wires based on this system wavefunctions on the bridge in the LUMOs of the bridging ligands simplifies the mechanism into a (SET) between the dn orbitals of the metal centres single pathway - a hole transfer process. In fact, and the pn HOMO of the bridgmg hgands in the mixed-valent properties of dimeric rutheni- RunRu is almost constant. Therefore the decrease umQII) complexes containing sulfur-substituted in the K,(IV, III) values in the RunRu system bridging P-diketonate rings are currently under (&om 6360 to 28) as the number of ethynl groups investigation by Professor Shimizu’s research (n) increases (2 to 4) cannot be interpreted by group (23). changes in 6E. According to the superexchange Molecular orbital calculations performed on mechanism (Equation (ix)), when the 6E values bridging ligands containing a connecting moiety for a series of binuclear complexes are almost con- between a bridge and a metal centre provide a lin- stant, H& is then directly proportional to the ear relationship between the square root of M,, product of ca and cp (couplmg strength terms). substituted for the electronic coupltng, and the Therefore, it is expected that the square root of sum of the squared extended Huckel MO coeffi-

InK,(IV, 111) bears a linear relationship to the prod- cients, El2, substituted for the product of atomic uct of ca and cp (Equations (iv), (v), (vii) and (ix)): orbital coefficients (caq). Using this relationship, mixed-valence complexes with even longer metal- {InKcW, Iq))”’ 0~ ca.cp (4 metal distances (> 2.0 nm), with strong electronic Here, cu (or cp), which describes the coupling coupling (large K, values) can be designed. between the donor (or acceptor) and the bridge, can be considered as the orbital coefficient at the Acknowledgements terminal atom of the bridge, because the magni- It is a pleasure to express my appreciation to Associate Professor Yasuhiko Yukawa, Niigata University, Japan, for read- tude of the coupling firstly depends on the ing and commenting on the manuscript. probability density of finding the electron at the terminal atom. References Figure 6 shows the linear relationship between 1 C. Creutz and H. Taube,J. Am. Chem. Sac., 1969,91, 3988 values of square roots of InK,(IV, and Zclz, the Irz) 2 M. B. Robin and P. Day, Adv. Inatg. Chem. Radixhem., sum of the squared extended Huckel MO coeffi- 1967,10,247 cients, see Table 11, for SHOMO at the terminal 3 C. Creutz, Pmg. Itiatg. Chem., 1983,30, 1

Pkztiinwm Metah Rev., 2001, 45, (1) 10 4 (a) J. E. Sutton and H. Taube, Inotg. Chem., 1981,20, 21 A distance required by Hush theory is the effective 3125; @) A. R Rezvani, C. Bensimon, B. Cromp, C. donor-acceptor separation distance (4, assumed to Reber, J. E. Greedan, V. V. Kondratiev and R. J. be related to dipole moment expectation values by Ciutchley, Inotg. Cbem., 1997,36, 3322 r = I p, - pr I /en, where p, and p~r are the dipole 5 (a) I. S. Moreira and D. W. Franco, J. Cbem. Soc., moments of the localised initial and final states in a Cbem. Commun., 1992,450; @) I. S. Moreira and D. mixed-valence system, respectively, and where e is W. Franco, Inoig. Cbem., 1994,33, 1607 the electronic charge and n is the number of electrons in the system. On the other hand, R in 6 (a) N. Le Narvor and C. Lapinte, J. Cbem. Sac., Cbem. Equation (viii) dedved by the superexchange mech- Commun., 1993, 357; @) N. Le Narvor, L. Toupet anism may be defined in terms of the actual bond and C. Lapinte, J. Am. Cbem. Soc., 1995, 117, 7129; lengths for the through-bond sequence perdnent to (c) F. Coat and C. Lapinte, Oiganometakcs, 1996, 15, the pathway being modelled (20c). The Ru-Ru sepa- 477 ration (d@-M)) approximately reflects the length of 7 T. Bart&, B. Bart&, M. Brady, R Dembinski and J. the bridge in the present systems. In Class II binu- A. Gladysz, Angew. Cbem., Znt. Ed EngI., 1996, 35, clear metal complexes, when the metal-metal 414 coupling is not very strong (probably K, < 107, the 8 (a) V. Grosshenny, A. Harriman and R Ziessel, metal-metal separation is usually used instead of the Angw. Cbem., Ink Ed EngI., 1995, 34, 2705; (b) A. dipole moment length (24). Harriman and R Ziessel, Cbem. Commnn., 1996, 22 Y. Hoshino, H. Umeda and Y. Kamo, Abstracts of 1707; (c) V. Grosshenny, A. Harriman, M. Hissler papers at the 44th Symp. on Coordination and R Ziessel, Phtinsm Metah Rev., 1996,40,26 and Chemistry of Japan, Yokahama, 1994, p. 178 72 23 T. Hashimoto, A. Endo, N. Nagao, G. P. Sat6, K. 9 J. E. Sutton and H. Taube, Inoig. Cbem., 1981, 20, Natarajan and K Shimizu, Inoig. Cbem., 1998, 37, 3125 521 1 10 V. Grosshenny, A. Harriman, F. M. Romero and R 24 (a) S. S. Isied, A, Vassilian, J. F. Wishart, C. Creutz, Ziessel, J. Pby. Cbem., 1996,100,17472 H. A. Schwarz and N. Sutin,J. Am. Cbem. Soc., 1988, 110, 635; (b) M.-A. Haga, Md. M. Ak, S. Koseki, A. 11 (a) A. Endo, Y. Hoshino, K. Hirakata, Y. Takeuchi, Yoshimura, K. Nozaki and T. Ohno, Inatg. Cbim. K. Shimizu, Y. Furushima, H. Ikeuchi and G. P. A&, 1994,226,17; (c) A.-C. Ribou, J:P. Launay, K. Sat6, Bull. Cbem. SOC.Jpn., 1989, 62, 709; @) Y. Takahashi, T. Nihira, S. Tarutani and C. W. Hoshino, Y. Yukawa, T. Maruyama, A. Endo, IC Spangler, Inotg. Cbem., 1994, 33, 1325; (d) A. R. Shimizu and G. P. Sat6, Inotg. Cbim. Actu, 1988,150, Rezvani, C. Bensimon, B. Cromp, C. Reber, J. E. 25 Greedan, V. V. Kondratiev and R J. Crutchley, Inarg. 12 R. C. Mehrotra, R Bohra and D. P. Gaur, “Metal p- Chm., 1997,36,3322; (e) Y. J. Chen, C.-H. Kao, S. Diketonates and Allied Derivatives”, Academic J. Lin, C.-C. Tai and K. S. Kwan, Inoig. Cbem., 2000, Press, London, 1978, p. 31 39, 189; (9 R C. Rocha, K. Araki and H. E. Toma, Inotg. Cbim. Actu, 1999,285,197; (g) IC D. Demadis, 13 Y. Kasahara, Y. Hoshino, M. Kajitani, K. Shimizu G. A. Neyhart, E. M. Kober, P. S. White and T. J. and G. P. Sat6, Oiganametdkcs, 1992,11, 1968 Meyer, Inaig. Cbem., 1999,38,5948 14 A. S. Hay, J. Oig. Cbem., 1962,27,3320 15 Y. Hoshino. T. Nishikawa. K. Takahashi and K The Author Yoshimasa Hoshino is an Associate Professor in the Department Aoki, Denki.Kgaku Oyoobi I&abutsni Kaguku, 1993, of Chemistry, Faculty of Education, Nagasaki University, Japan. 61,770 His main interests are in the molecular design of binuclear 16 Y. Hoshino, T. Suzuki and H. Umeda, Inotg. Cbim. and polynuclear metal complexes with strong metal-to-metal Ada, 1996,245,87 communication and of rotaxane and polyrotaxane metal complexes for molecular switches. 17 G. L. Closs and J. R Miller, Science, 1988,240,440 18 Y. Hoshino and Y. Hagham, Inoig. Chm. A&, 1999, 292,64 Rapid Synthesis of Colloidal Clusters 19 (a) R A. Marcus, J. Cbem. Pbys., 1956,24,966; @) R Scientists from PCLCC, Institute of Chemistry, A. Marcus, Annu. Rcv. Pbys. Cbem., 1964,15,155; (c) Chinese Academy of Sciences, Beijing, China, have R A. Marcus and N. Sutin, Biocbim. Biqbys. A&, synthesised uniform and stable polymer-stabilised 1985, 811, 265; (d) R A. Marcus and P. Siders, J. colloidal clusters of platinum, iridium, rhodium, pal- P/rv. Cbm., 1982,86,622; (e) R A. Marcus, and N. Sutin, Inoig. Cbm., 1975, 14, 213; (9 N. Sutin, J. ladium, ruthenium and gold by microwave irradiation Photacbem., 1979, 10, 19; (g) N. S. Hush, Pmg. Inaig. (W. Tu and H. Liu, J. Matm Cbem., 2000, 10, (9), Cbem., 1967,8,391; (h) N. S. Hush, Efednwbim.Ada, 2207-2211). As microwave heating has uniform and 1968, 13, 1005; (i) N. S. Hush, Coo& Cbem. Rm, fast heating characteristics a short irradiation 1985,64,135 only time was needed. The colloidal dusters formed have 20 (a) B. E. Bowler, A. L. Raphael and H. B. Gray, Pmg. Inatg. Cbem., 1990,38,259; @) R. Kosloff and M. A. small average diameters and narrow size distributions. Ratner, Iruef J. Cbem., 1990, 30, 45; (c) M. D. Stable colloidal ruthenium clusters without boron Newton, Cbem. Ra., 1991,91,767 were prepared using ethylene glycol as the reductant.

PLdinnm Metub Rm, 2001, 45, (1) 11 New ProCat2 Process Catalyst- Plant On 12th October 2000, Johnson Matthey catalyst, Johnson Matthey was given a BP opened a new plant at its site in Royston, Amoco Chemicals Breakthrough Award in Hertfordshire, to manufacture the latest gener- 1999. ations of supported catalysts, including The second BP Chemicals process is known platinum group metals catalysts, for chemical as AVADAm, and is to be used for the single- processes. The new step manufacture of facility, which uses ethyl acetate. The state-of-the-art pro- ne~AVADA~ pht duction technology, is based on BP has the capacity and Chemicals 'direct flexibility to produce addition' method for several hundred tons the manufacture of of catalyst per year ethyl acetate from for a wide range of ethylene and acetic applications. acid. The process is This Johnson simpler and cleaner Matthey plant has than other routes been designed ini- and is suited to loca- tially to manufacture tions where feed- special catalysts for stocks, such as the two new processes ethanol needed for belonging to BP these cutrent pre Chemicals. The first cesses, are not com- of these, known as petitively available. LEAPm, uses fluid JohnsonMatthey has bed technology to again worked with produce vinyl acetate BP Chemicals to monomer (VAM), The view inside the Procat2 catalysiplant, looking down to develop a manufac- the working area. The building has 3 storeys to facilitate a key intermediate the transport of materials between process stages, largely turing route for the for polymer manu- by graviy. The silver-coloured circular vessel on the catalyst used here. facture. The process, ground floor is one of the catalyst produciion vessels. The While the new red vessel to the Iefrfiliers ihe caialyst from the mother based on a radical liquor: it discharges io the floor below for further ireai- facility is now being new fluid-bed reac- meni. The red columns are vent pipes. Catalysts for BP'S used to produce LEAPrMand AVADArMprocesses are currently made in ihe tor and new catalyst plant, which has been designed as a mulii-purpose unit these two catalysts, design, rather than the plant is khly the traditional fixed-bed system, offers large versatile and is designed to manufacture a wide savings in capital and downstream process range of supported catalysts, includ.tng plat- costs. Johnson Matthey has worked in dose inum group metals catalysts, for the fine and partnership with BP Chemicals to optimise the speuahty chemicals industries. B. HARRISON performance of the catalyst and to scale-up its Brian Harrison is the Technology Director for the Johnson production. LEAPTMis the first fluid-bed Matthey Chemicals Business at Royston. His interests are in process to use a supported precious metal cata- homogeneous and heterogeneous catalyst development and in platinum group metals-based fine chemicals and platinum lyst. For its work in helping to develop the new group metals refining.

Pfdinwrn Me*rlr Reu., 2001,45, (l), 12 12 Organometahc Chemistry and Applied Catalysis A REVIEW OF THE FOURTH ANGLO-DUTCH SYMPOSIUM

By Simon Duckett Department of chemistry, University of York, England

The Anglo-Dutch Symposium on organometal- or naturally, via an initial pre-equilibrium step. lic chemistry and applied catalysis was held at the Both routes, however, involved pd(P-P)(Ar)]+ as University of Utrecht, The Netherlands, on the the key species. 26th and 27th October 2000. The fourth in this Professor J. M. J. Williams (University of Bath) series of meetings (1) attracted over 100 delegates demonstrated how reversible aced or cyanohydrin with 42 posters and 18 talks covering a wide range formation can be used to facilitate what would oth- of projects related to catalysis. In pdcular, a num- erwise be unsuccessful hydrogenation reactions. ber of highhghts relevant to platinum group metals This was explained by reference to the palladium- chemistry were described. catalysed hydrogenation of a vinyl aldehyde via initial conversion to the acetal in acidified Homogeneous Catalysis methanol (MeOH). After hydrogenation, subse- Professor J. M. Brown (University of Oxford) quent MeOH elimination leads to the rapid gave an elegant presentation dealmg with the formation of the required aldehyde. An impressive detection of rhodium-based intermediates during summary by Professor K. Vrieze (university of the hydrogenation of enamide substrates. When Amsterdam) detailed how the successful synthesis the hydrogenation of an enamide by of nitrogen diimine hgands and their subsequent ~(PJ3ANEPH0S)(MeOHJ2]+was examined attachment to palladium allowed CO insertion using parahydrogen-based sensitisation of the reactions to be achieved. NMR experiment, a new intermediate was detected. This intermediate contained both rhodium High Throughput Screening hydride and agostic hydrogen units with the latter Other notable developments reported were interacting strongly with the a-carbon of the based around the session on high throughput enamide substrate. The intermediate corresponds screening and pdel synthesis in catalysis. This to the direct precursor of the essential alkyl hydride started with an overview by Professor G.-J. M. and serves to illustrate the continuing opportun- Gruter (Ehdhoven University of Technology- ties offered by the parahydrogen technique. Avantium Technologies B.V.), before M. L. Several other talks served to illustrate how varying Turner (University of Sheffield) and Professor J. the llgand environment around a metal can control N. H. Reek (University of Amsterdam) illustrated reactivity. For example, G. P. F. van Strijdonck the benefits of rapid screening. Turner described (University of Amsterdam) described how paUadi- how rapid parallel screening using a multi-channel urn-catalysed C-C and C-N bond formations could reactor developed at Sheffield allowed the hetero- be facilitated by bisphosphine hgand systems - in geneous conversion of CO to ethanol to be conjunction with secondary sulfur and oxygen optimised. An elegant dysis based on parent- donors (the xantphos family). Details of the kinet- daughter methods %th crossover and mutation ics associated with the cross-coupling of PhBr and effects was used to rapidly deduce an optimised aminoarenes were shown to vary, dependmg on catalyst composition - without the need to whether halide abstraction from Pd(P-P)(Ar)Br complete runs for all possibilities. Reek focused on was achieved rapidly, via the addition of AgOTf, the solid-phase synthesis and rapid screening of

Phffnwnr M&& Rev., 2001,45, (l), 13-14 13 ruthenium catalysts for asymmetric hydrogen supercritical fluid, have good activity for hydro- transfer reactions, such as the conversion of ace- formylation of alkenes and yield better selectivity tophenone to 1-phenylethanol by IR for the desired straight-chain aldehyde than nor- spectroscopy. A silica-immobilised catalyst was mal organic solvents. Furthermore, the shown to exhibit good selectivity. construction of a flow reactor for supercritical Earlier in the programme Professor D. Vogt fluid catalysis allowed the use of a biphasic Wdhoven University of Technology), in a relat- approach involving ionic liquids in conjunction ed talk, illustrated how the immobilisation of with supercritical COz.While the catalyst remained catalysts via carbosilane dendrimer supports, in firmly dissolved in the ionic liquid, the aldehydes conjunction with ceramic membranes, can remove generated during catalysis were readily soluble in the problem of separating products from a cata- supercritical CO2 and easily separated. lyst. In one example a palladium catalyst had been In summary, the symposium clearly illustrated used to achieve the asymmetric hydrovinylation of the strengths and depth of organometallic chem- styrene. The dendrimer-supported system was istry and catalysis in the United Kingdom and The shown to achieve high local catalyst concentra- Netherlands. It will be interesting to see what new tions with site isolation overcoming deactivation. developments will be reported at the fifth meeting in this series, which is scheduled to take place in Developments in Novel Media the U.K. in Sheffield in early 2002. Details of the Continuing with this theme, B.-J. Deelman next Symposium can be found by contacting Dr (University of Utrecht-ATOFINA Vlissingen Michael Turner or Dr Anthony Haynes at the B.V.) talked about fluorous biphasic catalysis and University of Sheffield. A. J. Carmichael (University of Warwick) detailed opportunities offered by ionic liquids. Both pre- References sentations suggested methods for separating the 1 B.3. Deelman, Phinicm Met& Rev., 1999, 43, (3), 105; A. F. Chiffey, ibid., 1998,42, (l), 25; P. Ellis, catalyst from the products. R. ibid, 1997, 41, (l), 8 In the final presentation, Professor D. J. Cole- Hamilton (University of St Andrews) described The Author work performed in supercritical fluids. Notable Simon Duckett is a Senior Lecturer in Inorganic Chemistry at achievements included the illustration that tri- the University of York. He is interested in the study of catalytic reactions by NMR spectroscopy, applications of the parahydrogen alkylphosphine complexes readily dissolve in the effect, and binuclear catalysis. Chemical Fluid Deposition of Conformal Palladium Films Thin films of palladium (Pd) and Pd alloys have Researchers at The University of Massachusetts, many industrial applications, such as in catalysis, gas U.S.A., have now succeeded in depositing hghly sensors and microelectronics, where Pd film is used pure, conformal Pd films onto silicon wafers and as contacts in integrated circuits and as seed layers for polyimide at low temperature using chemical fluid electroless plating. Pd film is presently prepared by deposition (J. M. Blackbum, D. P. Long and J. J. vacuum sputtering and electroplating, but for com- Watkins, Chem. Muter., 2000,12, (9),2625-2631). This plex topographies consistent coverage is problematic. involves the chemical reduction of soluble organopal- High-purity, contour-following conformal Pd hlm ladium compounds in supercritical carbon dioxide may be prepared by chemical vapour deposition (COS at 40-80°C and 10Cb140 bar pressure. (CVD), but at temperatures > 200°C. A drawback to Deposition by hydrogenolysis of n-2-methylallyl- this is that low deposition temperatures are needed by (cydopentadienyl)palladium(JI)in CO2 was completed microelectronics to suppress mechanical stress during in less than 2 minutes at 60"C, yielding pure, continu- device fabrication and to minimise interdiffusion and ous, 100-200 nm thick, reflective Pd films free from reactions between adjacent layers. The thickness of ligand-derived contamination. Conformal coverage CVD-produced film also varies, giving inconsistent was observed on a patterned silicon wafer with coverage for lugh-aspect ratio features. features as small as 0.1 pm wide x 1 lm deep.

Pbtimm Metals h.,2001,45, (I) 14 The Ruthenium/TEMPO - Catalysed Aerobic Oxidation of Alcohols

By Arne Dijksman, Isabel W. C. E. Arends and Roger A. Sheldon

Laboratory for Organic Chemistry and Catalysis, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands

The combination of RUC~~(PP~~)~and 2,2 <6,6‘-tetramethylpiperidine N-oxyl (TEMPO)affords an efJicient catalytic system for the aerobic oxidation of a variety of primary and secondary alcohols, giving the corresponding aldehydes and ketones, in > 99 per cent selectivity in all cases. This interesting catalytic system is probably based on a hydridometal mechanism, involving a ‘RuH2(PPh~).~’-speciesas the active catalyst. TEMPO acts as a hydrogen transfer mediator and is regenerated by oxygen.

The catalytic conversion of primary alcohols In addition to metal complexes, stable nitroxyl into aldehydes and of secondary alcohols into radicals, such as 2,2’,6,6’-tetramethylpiperidine N- ketones is essential for the preparation of many oxyl (TEMPO), have been used as catalysts for the key synthetic intermediates in organic chemistry oxidation of alcohols to aldehydes, ketones and (1). Traditional methods for performing such carboxylic acids (9). Typically, these transforma- transformations generally involve the use of stoi- tions employ 1 mol% of the nitroxyl radical and a chiometric quantities of inorganic oxidants, stoichiometric amount of a tenninal oxidant, such notably chromium(VI) reagents (2), and generate as sodium hypochlorite (lo), trichloroisocyanuric copious quantities of inorganic waste. Hence, the acid (ll), m-chloroperbenzoic acid (12), sodium quest for effective catalytic systems that use dean bromite (13), sodium chlorite (14) and Oxone” inexpensive oxidants such as oxygen and hydrogen (15). In these systems, an oxoammonium cation is peroxide - a ‘green method’ - to convert alcohols generated and acts as the active oxidant, see to carbonyl products on an industrial scale remains Reaction (i). an important challenge. Most examples of aerobic oxidation of alcohols, both homogeneous and heterogeneous, involve the use of Group H on R VIII metal complexes as catalysts (3). In 0 particular, ruthenium compounds, which are widely used as catalysts in organic syn- Alternatively, the use of TEMPO in combina- thesis have been thoroughly investigated (4). For tion with copper salts and oxygen as the primary example, tetrapropylammonium perruthenate oxidant was reported by Semrnelhack (16). PAP),either as such (5), or supported on an ion However, this system was effective only with exchange resin (6) or MCM-41 (a mesoporous easily oxidised benzylic and allylic alcohols. molecular sieve) 0,and ruthenium hydrotalcites (8) are capable of aerobically oxidisbg a variety of Ruthenium/TEMPO Catalyst System alcohols to carbonyl compounds. However, all the Based on the catalytic systems described above, reported metal systems require relatively large we reasoned that the combination of ruthenium quantities of catalyst (5-10 mol%) and/or addi- and TEMPO would likely lead to an efficient cat- tives, that is cocatalyst (10-20 mol?h) and drymg alytic system for the aerobic oxidation of alcohols. agent (2 equiv.), to achieve their activity. For our initial experiments, we selected ocm-2-01

Phfiinwm Meralr h.,2001,45, (l),1519 15 RutheniurnTTEMPO-Catalysed Aerobic Oxidation of Various Alcoholsa - Entry Substrate Product Su bstrate/Catalyst Time, :onversion,b - ratio h % 1 octan-2-01 octan-2-one 100 7 98 (90) 2c octan-1-01 octanal 50 7 a5 3 benzylalcohol benzaldehyde 200 2.5 > 99 (90) 4 pnitrobenzylalcohol pnitrobenzaldehyde 200 6 97 5 1-phenylethanol acetophenone 100 4 > 99 (93) 6' geraniol geranial 67 7 91 7c 3-methyl-2-butene-l -ol d-methyl-2-butenal 67 7 96 a cyclooctanol cyclooctanone 100 7 92 gc octan-2-olloctan-1-01 octan-Z-one/octanal 50 7 1o/ao 10 benzylalcohol/l -phenylethanol benzaldehyde/acetophenone 200 3 90/5

'Reaction conditions: 15 mmol substrate. ratio of RuCI2(PPhl),:TEMPO = lt3. 30 ml chlorobenzene. 10 ml min-' 0::N. (8:92; vh).p (total pressure) = 10 bac T = 100°C. Conversions based on GC results (selectivity > 99% in all cases) using n-hexadecane as internal standard. The numbers in parenthesis are isolated yields (21). ' 02 atmosphere as a test substrate and allowed it to react in within 1 hour. The ability to suppress over-oxida- chlorobenzene with catalytic quantities of a ruthe- tion is due to the well known anti-oxidant activity nium complex in the presence of TEMPO and of TEMPO. This stable nitroxyl radical efficiently oxygen. The best results were obtained when using scavenges free radical intermediates during autox- 1.0 moWo of RUC~~(PP~~)~(17) and 3.0 mol% of idation and thereby terminates free radical chains. TEMPO (la), see Reaction (ii). In this case, the Allylic alcohols were selectively converted into the corresponding unsaturated aldehydes in high yields without intramolecular hydrogen transfer (Entries 5 and 6). Some ruthenium(I9 phosphine complexes are known to catalyse intramolecular hydrogen transfer reactions of turnover frequency (TOF) was 14 h-', which is allylic alcohols to saturated ketones (20), which superior to the most active aerobic ruthenium sys- obviously is not occurring in the present system. tem described in the literature, that is "PAP (5), Besides aliphatic and allylic alcohols, cyclic and which in OUT hands gave a TOF of 5.5 h-' for benzylic alcohols were also smoothly oxidised into octanz-01 (19). the corresponding ketones and aldehydes (Entries The use of RuCl@'Ph3)JTELMPO as catalyst 3, 4 and 7). In these cases lower catalyst loadings for the aerobic oxidation of alcohols was then were required (substrate/catalyst > 100). applied to a range of representative alcohols. As A problem in the present aerobic Ru/TEMPO can be seen from the Table, octan-1-01 is oxidised catalysed oxidation of alcohols is the deactivation selectively into octanal (Entry 2). TEMPO not of both ruthenium and TEMF'O during catalysis. only accelerates the oxidation of octan-1-02 but Attempts to use heterogeneous TEMPO systems, also completely suppresses the over-oxidation of such as PIP0 (polymer immobilised TEMPO) octanal to octanoic acid (19). Attempted oxidation (22) or MCM-41 and silica-supported TEMPO of octanal under the same reaction conditions, in (23), lead to inactive systems (24). This is probably the presence of TEMPO, gave no reaction in one due to coordination of ruthenium to the amine week. On the other hand, without TEMPO moiety in PIP0 and absorption of ruthenium on octanal was converted completely to octanoic acid the MCM-41 and silica surfaces, The latter was

P&nm Meta!I h.,2001,45, (1) 16 proven by performing the Ru/TEMPO catalysed aerobic oxidation of ocm-2-01 in the presence of silica. In this case, only minor formation of octan- 2-one was observed as well as a brightening of the reaction mixture from dark brown to shghtly orange. Because of the results with heterogeneous TEMPO systems and the fact that ruthenium is much more expensive than TEMPO, we refocused our aim and are currently workmg on the hetero- genisation of ruthenium. TEMPO, mol *I.

I ~ Mechanistic Aspects Fig. I The conversion of octan-2-01 in chlorobenzene at 100°C afer I hour; using aerobic oxidation catalysed Although in separate experiments secondary by the RuCII(PPhJdTEMP0 system. A range of TEMPO alcohols are oxidised faster than primary ones, in concentrations huve been employed competitive experiments, the Ru/TEMPO system displayed a preference for primary versus secondary We performed this experiment and found octan-2- alcohols (Entries 8 and 9). Since these reactions are one and TEMPH as products in the ratio of 3:2, generally believed to involve the intermediate for- see Reaction (iii). Most likely, TEMPH is formed mation of an akov-ruthenium complex (25), we by a degradation reaction of the extremely unstable interpret this result as an indication that the ruthe- TEMPOH, see Reaction (iv). Attempts to prepare nium preferentially complexes with primary TEMPOH (27) under an inert atmosphere always alcohols, leadmg to selective oxidation of the latter resulted in the formation of TEMPH. On the even though the rate-determiningdehydrogenation other hand, in the presence of oxygen TEMPOH step is faster with secondary alcohols. is very rapidly converted back to TEMPO. These When the effect of the TEMPO concentration results support the mechanism shown in Figure 2 on the oxidation rate was investigated, an almost and indicate that TEMPO acts as a hydrogen linear increase was observed, with respect to the transfer mediator. TEMPO concentrationin the range 0-4 moW, for Most probably, the active ruthenium dihydride the oxidation of octan-2-01, see Figure 1. Above 4 species is RuH2(PPh&, as in the RuCl@Ph$3- mol?h the increase starts to level out, and further catalysed hydrogen-transfer reactions (28). In the addition of TEMPO led to only a minor increase ruthenium/TEMPO-catalysed aerobic oxidation in the yield obtained after 1 hour. The same 'medi- of octar-2-01, RuHz(PPh& was as active as ator' dependency was observed with a ruthenium/ RuCl2(PPh3),, that is, octan-2-01 was quantitatively benzoquinone/MnO2 system, reported by Backvall converted to octan-2-one within 9 hours using 1.5 and coworkers (26), and we propose a similar moWo of either catalyst and 4.5 mol?h of TEMPO. mechanism, see Figure 2. The result can be explai- The stoichiometric reaction of TEMPO with ned in terms of a change in the rate-limiting step. At low concentrations of TEMPO, reoxidation of the 'ruthenium hydride'-species may be the slowest step, whereas at high concentrations of TEMPO, dehydrogenation is probably rate limiting. Under an inert atmosphere, no regen- I eration of TEMPOH should take place 0' and Ruc12(Pph3)3catalyses the stoichi'- Fig. 2 Schematic mechanism of the RuflEMPO-catalysed aerobic metric reaction of TEMPO and octan-2-0L oxidation of alcohols

Phfimm Me:& b.,2001, 45, (1) 17 (iii)

+ H20 I 0“QI I OH 0’

RuHz(PPh3)d in chlorobenzene, under an inert spectrometry) and probably proceeds via complex atmosphere, also resulted in the formation of (a). The formed ruthenium alkoxide species @) TEMPH. undergoes normal p-hydrogen elimination to pro- Based on the results presented above, we produce the ketone/aldehyde and the active pose the following catalytic cycle to explain the ruthenium dihydride species. aerobic RuC12(PPh3)3/TEMPO-catalysed aerobic oxidation of alcohols, see Figure 3. The reaction of Concluding Remarks ‘RUH~(PP~~)~’with TEMPO, followed by the We have discovered that the combination of insertion of an alcohol to form a ruthenium alkox- catalytic amounts of RuClz(PPh3)3 (< 2 mol%) and ide species, is currently under investigation (using TEMPO (< 5 molyo) affords an efficient catalytic in situ IR spectroscopy and electron-spray mass system for the aerobic oxidation of a broad range

Fig. 3 Proposed mechanism for the RwTEMPO-catalysed aerobic oxidation of alcohols

PhtimmMetuLr h.,2001, 45, (1) 18 of primary and secondary alcohols, giving the cor- 15 C. Bolm, A. S. Magnus and J. P. Hildebrand, Org. respondmg aldehydes and ketones, in > 99 per Lett., 2000,2,1173 16 M. F. Semmelhack, C. R Schxnid, D. A. Cortks and cent selectivity in all cases. Most probably, this C. S. Chou, J. Am. Cbem. Sot., 1984,106,3374 interesting catalytic system is based on a 17 RuCIz(F‘Ph& was prepared according to: R. Holm, hydridometal mechanism, involving a Inoq. Syntb., 1970,12,238 ‘RuH@’Ph~)3’-intermediate. TEMPO acts as a 18 Typical procedure for the aerobic oxidation of octan-2-01:octan-2-01 (15.0 mmol; 1.96 g), n-hexa- hydrogen transfer mediator and is easily regenerat- decane (internal standard; 3.0 mmol; 0.69 g), ed by oxygen. We are presently investigating RuClz(TPh3)3(0.225 mmol; 216 mg) and TEMPO methods for heterogenising the ruthenium catalyst. (0.675 mmol; 106 mg) were dissolved in 30 ml of chlorobenzene, heated in a high-pressure reactor (10 bar) to 100°C under a continuous stream (10 ml Acknowledgement mid) of an oxygen-nitrogen mixture (892; v/v) and We gratefully achowledge IOP Catalysis (Innovation- stirred for 7 hours. Octan-2-01 conversion and octan-2-one selectivity were determined Oriented Research Program on Catalysis), Ministry of Economic using GC- Affairs, The Netherlands, for finanaal support and Johnson analysis (50 m x 0.53 mm CP-Wax 52 CB column). Matthey for their donation of RuC13 hydrate. 19 A. Dijksman, I. W. C. E. Arends and R A. Sheldon, Cbem. Commun., 1999,1591 20 J.-E. Bachal and U. Andreasson, Tetrabedtun Left.., References 1993, 34, 5459; B. M. Trost and R J. Kulawiec, 1 R A. Sheldon and J. K. Kochi, “Metal Catalysed Tetrabedrun Lff.,1991,32, 3039 Oxidations of Organic Compounds”, Academic 21 Typical procedure for isolating the product: the reac- Press, New Yo& 1981; S. V. Ley, J. Norman, W. P. tion mixture was diluted with n-hexane (to remove Grifiith and S. P. Marsden, Synthesis, 1994, 639; M. ruthenium) and dtied over MgSO.,. The resulting Hudlicky, “Oxidations in Organic Chemistry”, ACS, mixture was filtered and the solvent removed in Washmgton, DC, 1990 and references cited therein vacuo. The product was separated from chloroben- 2 G. CaineUi and G. Cardillo, “Chromium Oxidations zene using Kugelrohr distillation. in Organic Chemistry”, Springer, Berlin, 1984 22 A. Dijksman, I. W. C. E. Arends and R A. Sheldon, 3 R A. Sheldon, I. W. C. E. Arends and A. Dijksman, Ckm. Comnn., 2000,271 CataL To&, 2000,57,157 23 M. J. Verhoef, J. A, Peters and H. van Bekkum, Stud 4 T. Noata, H. Takaya and S.-I. Murahashi, Cbem. Rey., Sut$ Sci. Catal, 1999,125,465; C. Bolm and T. Fey, 1998,98,2599 Cbm. Commun., 1999,1795; D. Brunel, P. Lentz, P. 5 I. E. Marko, P. R Giles, M. Tsukazaki, I. Chell.5 Sutra, B. Deroide, F. Fajula and J. B. Nagy, S&d Sat$ Regnaut, C. J. Urch and S. M. Brown, J. Am. Ckm. Sci Catal, 1999,125,237 Soc., 1997,119, 12661 24 A. Dijksman, I. W. C. E. Arends and R A. Sheldon, 6 B.hen, R L.enz and S. V. Ley, Synthesis, 1998,977 submitted to Synkft 7 A. Bleloch, B. F. G. Johnson, S. V. Ley, A. J. Price, 25 A. Hanyu, E. Takezawa, S. Sakaguchi and Y. Ishii, D. S. Shephard and A. W. Thomas, Cbem. Commun., Tehhedrun Lett.,1998,39, 5557; K B. Sharpless, K. 1999, 1907 Akashi and K. Oshima, Tetmbedmn Lff.,1976, 29, 8 T. Matsushita, K. Ebitani and K. Kaneda, Cbem. 2503; Y. Sasson and J. Blum, Tetrabedm Lett., 1971, Commun., 1999, 265; K. Kaneda, T. Yarnashita, T. 24, 2167; S.-I. Mumhashi, T. Noata, K. Ito, Y. Matsushita and K. Ebitani,]. Otg Chem., 1998,63,1750 Maeda and H. Taki, J. Otg. Cbem., 1987,52,4319 9 A. E. J. de Nooy, A. C. Besemer and H. van 26 U. Karlson, G.-2. Wang and J.-E. Backvall,]. Og. Bekkum, Sytksis, 1999, 1153 and references cited Cbem., 1994,59,1196 therein; J. M. Bobbitt and M. C. L. Flores, 27 C. M. Paleos and P. Dais, J. Cbem. SOC. Cbem. Hetnoych, 1988,27,509 Commun., 1977,345 10 P. L. An&, C. Biffi, F. Monk and S. Quici, J. Og. 28 A. Atanyos, G. Csjernyk, K. J. Szab6 and J.-E. Cbm.., 1987, 52, 2559; A. Dijksman, I. W. C. E. BackvaU, Cbem. Comun., 1999,351 Arends and R A. Sheldon, Ch. Commun., 2000, 271 The Authors Roger Sheldon is Professor of Organic Chemistry in the Faculty of 11 C:J. Jenny, B. Lohri and M. Schlageter, Eumpcan Applied Sciences at Delft University of Technology. His main AppL 775,684; 1997 interests are in the application of homogeneous, heterogeneous 12 J. A. Cella, J. A. Kelley and E. F. Kenehan, J. 0%. and enzymatic catalytic methods in organic synthesis. Cbem., 1975, 40, 1860; S. D. Rychovsky and R Arne Dijksmam is a Ph.D. student in Professor Sheldon’s group. Vaidyanathan,J. 0%.Cbem., 1999,64,310 His main interests are in the development of ruthenium catalysts 13 T. Inokuchi, S. Matsumoto, T. Nishiyama and S. for the oxidation of alcohols using clean and cheap oxidants. Torii,J 0%.Cbem., 1990,55,462 Isabel Arends is Assistant Professor of Organic Chemistry in the 14 M. Zhao, J. Li, E. Mano, 2. Song, D. M. Tschaen, E. Faculty of Applied Sciences at Delft University of Technology. Her J. J. Grabowski and P. J. Reider, J. 0%.Cbem., 1999, main interests are in the development of (chiral) homogeneous 64,2564 catalysts and zeolites for selective oxidative transformations.

Platinum Metah Rev., 2001,45, (1) 19 Techniques for Catalyst Manufacture REVIEW OF A ROYAL SOCIETY OF CHEMISTRY MEETING ON APPLIED CATALYSIS

The Industrial Affairs Division of the RSC dation (PRO3 unit to provide a hydrogen-rich (Applied Catalysis Group) held a meeting on feed to a proton exchange membrane (PEN fuel "Techniques of Catalyst Manufacture" at the cell. A SOFC-PEM hybrid system of this type with Advantica (formerly BG Technology) Research an electrical output of 500 kW was claimed to be and Technology Centre, in Loughborough, U.K., 61 per cent efficient. on 8th November 2000. Delegates were introduced to Advantica's activities in a diverse range of Metal Precursors and Catalyst Carriers areas, which included the development of natural Very convincing evidence hghlighting the pit- gas powered vehicles, hgh-temperature solid oxide falls associated with deposition of metal precursors fuel cells (SOFCs) and molten carbonate fuel cells on preformed supports was given by Robert as well as catalytic technologies for the functional- Terorde (Fmgelhard, The Netherlands). While his isation of methane through partial oxidation, presentation dealt exclusively with the introduction steam reforming and Fischer-Tropsch synthesis. of iron into a preformed Si02 support, it is clear that the lessons learnt would be applicable to the Industrial Catalyst Preparations deposition of other metals onto other supports This introduction provided the background for and it would be possible to extend this work to the presentation by Andrew Dicks (Advantica, help optimise platinum group metal distributions. Loughborough) on the preparation of industrially He claimed that the final distribution of the metal relevant catalysts by coprecipitation, especially for oxide throughout the support was influenced by the activation of methane. Much effort has been properties of the metal precursor, such as its inter- directed at the preparation of Alz03-supported action with the support surface, its crystallisation nickel catalysts by coprecipitation, for reactions behaviour and the viscosity of the salt solution. such as steam reforming and catalytic partial oxi- The speed of the drymg process was also found to dation (CPO). Latterly, supported platinum group be critical. Egg-shell distributions of the metal salts metals catalysts, such as Alz03-supported palladi- were formed when solutions of strongly crystallis- urn and platinum in addition to Ti02-supported ing salts, which do not become viscous during the rhodium, have found favour for CPO due to their dqmg step, for example K3Fe(CV6, were used in enhanced rates of reaction and resistance to coke the initial impregnation. The microscopic effect of formation. The technique of homogeneous copre- an egg-shell distribution was shown to be the cipitation, where hydrolysis of urea at 120°C growth of large metal particles. results in uniform release of OH- groups through- Addition of a viscosity-increasingagent such as out the catalyst precursor slurry, has been hydroxyethyl cellulose to the iron-containing employed to produce a supported-ruthenium impregnating solution had the effect of generating (Ru/Zn0-&03) Fischer-Tropsch catalyst. The a uniform dismbution of the deposited metal. It BET surface area of the final material was shown was also shown that an iron precursor, such as an to be strongly dependent on the ZnO:&O3 ratio. aqueous solution of NI-L[Fe"'(OH)(citrate)], will The greatest surface area was obtained with the become very viscous when heated, resulting in a highest A1203 content. very uniform dismbution of the metal salt through- These preparation techniques have formed the out the support pore structure. These data are also basis for the catalyst which is used to internally applicable to the deposition of platinum group met- reform CH4 in a SOFC. More recently, the anode als on preformed supports and this work may be of exhaust from a SOFC has been converted by value in catalysis for the petrochemical industry. means of shift reactors and a final preferential oxi- Andrew Holt (Catal International, Sheffield)

Phtimm Metah Rev., 2001,45,(l), 2C21 20 explained the equipment required and process silicalite (Ti-1) and the Condea process for the variables associated with producing catalyst carri- manufacture of hgh purity A1203 from aluminium ers in hgh volume by the cost-effective technique alkoxides. Sol-gel preparations are not restricted to of extrusion. Extruder designs and therefore the stoichiometric compositions and can result in bet- shape of the extrudates depend on the material to ter control of the porosity of the final material. be extruded. Catalyst supports used for reactions Professor Schmidt also suggested that use of such as hydrotreating are produced using a twin supercritical COZ has the potential to greatly sim- contra-rotating screw. The wet metal oxide pastes, plify solvent removal. used to make the supports, are normally very abra- The conference organiser Barry Nay (BP sive and possess poor flow characteristics. Chemicals, Sunbury-on-Thames) thanked all the However, in the extrusion process the precursor participants at the well-attended meeting and sug- paste (‘dough’) needs to possess sufficient plastic- gested that the next meeting of the RSC Applied ity, lubricity and particulate cohesion to pass Catalysis Group may take place outside Britain. through a small orifice. In order to achieve this the Further information on events organised by the support powder, for example &03, is normally RSC Industrial Affairs Division, Applied Catalysis treated with dilute HNo3 to help peptisation. The Group are obtainable from [email protected]. pH of this peptisation step has a large influence on P. J. COLLIER, M. R. FEAVIOUR and M. J. HAYES the pore size distribution of the final material. At The Authors low pH (< 2) microporous materials could be pro- Paul Collier is a Research Scientist in the Process Catalysis Group duced. The plasticity and particulate cohesion of at the Johnson Matthey Technology Centre (JMTC), Sonning Common. He is interested in the preparation of catalysts and the ‘dough‘ can be controlled by the introduction testing, with particular regard to bulk chemical processes. of one or more of a range of organic modifiers Mark Feaviour is a Research Scientist at the JMTC, Sonning from wood flour to methyl cellulose. Addition of Common, where he works in catalyst preparation for the Reformer Group. His current projects include liquid hydrocarbon reforming, wood flour has the effect producing large voids in platinum group metals catalysts and water gas shift catalysts. the extrudate upon calcination. This can lead to Martin Hayes is a Research Scientist in the Reformer Group at improved gas flow characteristics. Lubricity addi- JMTC. Sonning Common. He is interested in the preparation and scale-up of a variety of supported platinum group metals catalysts tives, such as graphite or stearates, can also be for the generation of high purity hydrogen from hydrocarbons. introduced. The resultant hydrogen streams are used in fuel cells.

Progress in Techniques for Heterogenised Rhodium Catalyst Catalyst Manufacture The search for a clean benign replacement for the Professor Friedrich Schmidt (Sud-Chemie, industrial synthesis of amines (N-phenyl-N‘-iso- propyl-pphenylendiamine and N,”-di(l,4dimethyl- Germany) reviewed recent progress in techniques penty1)-pphenylendiamine) used as antioxidants in for catalyst manufacture. Large scale catalyst vulcanising rubber, additives in biomimetic sensors preparation is strongly driven by cost. It is, there- and anticorrosive agents, has resulted in a one-pot fore, necessary to demonstrate a very sigtuficant synthesis using a platinum/carbon-based catalyst. performance benefit before it is viable for industry However, this synthesis is not reproducible. to make the investment to adopt a new technique Now researchers at the UniVeisitat Rovira i Vkgjli, for manufacture of a particular catalyst. Spain, have developed a reproducible one-pot syn- If organic solvents or organometallic precur- thesis to convert a primary amine into a secondary sors are to be used in precipitation or sol-gel amine by imine intermediate formation (R. Margalef- Cadi, C. Claver, P. Salagre and E. Femindez, preparations, significant plant modifications will Teirahedmn Letc., 2000, 41, (34), 6583-6588). The cat- be required. Such modifications, dictated by safe- alyst was prepared by immobilising preformed ty, environmental and engineering considerations, w(COD)(PPh3)2]BF4 and its iridium analogue on have prevented large-scale adaptation of these montmorillonite K10. The rhodium catalyst had the techniques for industrial catalyst manufacture. higher activity. The reaction is mild and solvent-free Exceptions include the manufacture of titanium and the catalyst can be easily recovered and reused.

P(atinxm Metah Rm, 2001, 45, (1) 21 Ferrocenyl Phosphme Complexes of the Platinum Metals in Non-Chral Catalysis THEIR APPLICATIONS IN CARBON-CARBON AND CARBON-HETEROATOM COUPLING REACTIONS

By Thomas J. Colacot Organometallic Chemicals & Catalysts Development, Johnson Matthey, 2001 Nolte Drive, West Deptford, NJ 08066, U.S.A.

The Czsymmetric ligand, 1,l‘-bis(diphenylphosphino)ferrocene, discovered about three decades ago, has opened up a new area of chiral and non-chiral ligands. This ligand is a relatively air- and moisture-stable solid and has a large phosphorus-metal-phosphorus bite angle in its metal complexes. These types of ligands have demonstrated numemus applications in metal- catalysed organic transforrnutions, such as coupling reactions, asymmetric hydrogenation, hydrogen transfer, hydrosilation and allylic alkylation. In this brief review, some recent applications, particularly using platinum metals, will be discussed.

Ferrocenyl phosphines, such as the C2 symmet- aryl (12) substituted phosphines are known in the ric 1,l’-bis(dipheny1phosphino) ferrocene, dppf, literature, and their applications in difficult cou- have emerged as a new class of ligands, with a wide pling reactions are currently being explored. A few range of unique applications, since their first dis- examples of unsymmetrical ferrocenyl phosphines covery and use in 1965 (1). The literature describq have also been reported (13), although their cat- this includes, for example, the first two chapters of alytic applications have not been investigated in the book, “Ferrocenes”, edited by Togni and detail. Different research groups have utilised the Hayashi. In this book they give a detailed account planar chirality of the ferrocene molecule in of the syntheses and catalytic applications of dppf designing novel chiral phosphines - because of (2) and chiral ferrocenyl phosphines (3) up to the their inherent resistance to racemisation. As a year 1995. Recently, Hartwig has emphasised the result the area of chiral ferrocenyl phosphines has applications of dppf and related ligands in carbon- outgrown that of non-chiral ferrocenyl phosphines heteroatom coupling reactions (4). Hayashi (5), (3, 510). Richards (6), Togni 0,Knochel (8), Kagan (9) and It0 (10) have also reviewed the syntheses of chiral Synthesis of 1,l’-Bis(diphenylphosphin0)- ferrocenyl phosphine ligands which have applica- ferrocene and Related Ligands tions in asymmetric syntheses. The first example of a ferrocene-based phos- Aspects of this work, related to the platinum phine ligand, 1,l’-bis(dipheny1phosphino)ferro- group metals, is updated here. In particular this cene, dppf, was synthesised in 1965 by reacting the review covers some recent applications of non-chi- dilithium salt of ferrocene with PhzPC1 (1). ral ferrocenyl phosphines, coordinated to platinum Subsequent process improvements from academic group metals, in homogeneous catalysis. Emphasis (12) and industrial laboratories (14) led to the com- is placed on Kumada-Hayashi, Suzuki, Heck and mercialisation of dppf in multi kilogram quantities. Buchwald-Hdg coupling reactions. Examples of Cp2Fe(PR2)2, where R is an aliphatic group such as t-Bu or i-Pr are also known (12-14). Types of Ligands Seyferth (1 1) and Cullen (1 3) demonstrated an ele- Ferrocenyl ligands are classified into two types: gant way to make a few examples of unsymmetrical chiral and non-chiral. The best known example of ferrocenyl phosphine hgands, where the dilithium a non-chiral phosphine is dppf which has CZsym- salt of ferrocene is reacted initially with RPClz to metry (2). Monodentate (11) and bidentate akyl or produce a C-P-C bridged species. This bridge is

PhhntmMetdr h.,2001,45, (l),22-30 22 2BuLi r-TMEDA

Fe R*PCI -Fe c

RPCI2

Scheme I General routes for the synthesis of various non-chiral ferrocenyl phosphines later opened with RLi, followed by the subsequent pling reactions. The special advantages of using coupling reaction with R'2PC1 to produce ferrocenyl phosphhes in such couphg reactions (CaH,-PR2)Fe(C&-PR'*). There are also reports are reported here. of the synthesis of monosubstituted ferrocenyl phosphines (1 1). Although monosubstituted elec- Carbon-Carbon Coupling tron-rich ferrocenyl hgands are useful for aryl KnmaakHqubi Co@ing chloride coupling reactions, thek syntheses are Kumada and Hayashi were the first group to tricky, tedious and the products are very often demonstrate the extraordinary ability of contaminated with &substituted byproducts - as PdClzdppf, in difficult C-C couplmg reactions the mono lithium salt is not easy to isolate in pure form (1 5). General routes for the syntheses of vat- ious non-chiral ferrocenyl phosphines are summarised in Scheme I.

'Bite angle Applications of Ferrocenyl Phosphines PdClzdppt Numerous patents and publications have appeared during the past decade describing the involving Gngnard reagents and organic bro- applications of ferrocenyl phosphhes in metal- mides. In 1984 Hayashi, Kumada, +chi and catalysed organic reactions. Recently, increasing their coworkers (16) studied the reaction of organ- numbers of pharmaceutical and chemical compa- ic bromides with alkyl magnesium or zinc reagents nies have become interested in palladium- in the presence of various catalysts, such as catalysed carbon-carbon and carbon-nitrogen cou- PdC12(PPh&, Pd(PPh&, PdCbdppe, PdCLdppp

PkzfinumMetah Rm, 2001,45, (1) 23 Scheme I1 Kumada-Hayashi coupling reaction

I X Isolated yield 86-97’!. p-COMe, p-CO?Me, Scheme 111 />-CH:CH:COCHI Suzuki coupling of aryl mesyls using the Ni(0)dppf complex

and PdCl,dppb, where dppe = 1,2-bis(diphenyl- seems to suggest that the smaller Cl-Pd-Cl angle phosphino)ethane, dppp = 1,3-bis(diphenylphos- more strongly influences the reactivity than does phino)propane and dppb = 1,4bis(diphenylphos- the larger P-Pd-P bite angle, see the Table, (17). phino)butane, respectively. In particular see Further work is needed to correlate the reactivi- Scheme I1 for PdClzdppf. ty/selectivity with the X-P-X bond angles (X = The PdClZdppf catalyst gave excellent selectivi- halogen or leaving group). ty with nearly quantitative yield of the desired, coupled product, see the Table. They attributed the SupG CoKpling remarkable success of this catalyst to its larger bite Another interesting application of dppf in C-C angle and a flexible bite size. Gan and Horr called coupling was demonstrated by Suzuki and cowork- PdC1,dppf a ‘magic catalyst’ as its behaviour was ers on reacting aryl boronic acids with more far superior to that of the classical monodentate challenging aryl and vinyl triflates in the presence PPh3-based catalysts or even to that of the of PdC1,dppf (18). The coupling becomes more conventional diphenylphosphinoalkane-based difficult with inherently less reactive and less bidentate hgands (2). Until recently it was believed expensive aryl mesylates and sulfonates. By chang- that the larger P-Pd-P angle and longer P-Pd bond ing from PdClzdppf to NiClzdppf/Zn, Percec distance promoted the facile reductive elimination obtained 81 per cent yield of Cmethoxybiphenyl (that is, coupling), thereby minimising the p- by the Suzuki coupling reaction of phenyl mesylate hydride elimination. However Hayashi’s recent with 4-methoxyboronic acid (19). Miyaura later work with bis(diphenylphosphino)biphenyl, dpbp, extended this work to other examples of aryl

Comparison of Catalytic Activities in the Room Temperature Reaction of Bromobenzene with sec-BuMgCI Catalyst I Reacti; time, Bite angle, Angle sec-BuPh. n- Bu Ph , I P-Pd-P, I CI-Pd-CI,’ YO % (PPh3)zPdClz 24 n/a 5 6 PdChdppe 48 85.8 94.2 0 0 PdClzdPPP 24 90.6 90.8 43 19 PdClzdppb 8 94.51 89.78 51 25 PdClzdpbp 1 92.24 88.21 93 1 PdCIzdppf 1 99.07 87.8 95 2

Phbinwm Met& Rm, 2001,45, (1) 24 [Rh(acac) Ln] -7 --Ln Yield, % RB(OH)z + R’CHO DME-H20 or dioxane-H20 PPhl 0 [TOH PCy, 5 R = aryl, 1 -alkenyl; R’ = alkyl, aryl: DME = dimethyl ether dPPP 82 Scheme IV dppb 17 Rhodium catalysed C-C coupling involving u Suzuki reagent dppf 99

mesylates and even more challenging aryl chlo- gave only modest to moderate conversions. rides, and achieved yields of over 90 per cent by Although the results generaJly correlate with the P- using Ni(0)-dppf catalysts, see Scheme 111, (20). In Rh-P bite angles, dppb stands out as an exception: all these cases dppf as ligand is far superior to giving only 17 per cent conversion despite its rela- other biphosphines, such as dppp, dppe and dppb tively large bite angle. This seems to suggest that or monophosphines, such as PCy, and PPhs. Hayashi’s recent observation has to be taken seri- Interestmgly, it was observed by Pndgen that ously (17, and there may be factors other than the there was no couplug reaction between chiral flu- bite angle which decide the reactivity in the cou- orosulfonates and aryl boronic acids in the phg reactions. presence of NiClzdppf,while PdC12dppf gave over 98 per cent yield of the coupled product, 1,fdiaryl Heck Coupling: indene, without any racemisation (21). These com- Only a small number of reports are available on pounds are precursors to SmithIUine Beecham’s: applications of ferrocenyl phosphines in Heck SB 209670 and SB 217242 (code numbers of couplmg, although the importance of dppf in such future drug candidates). Water soluble Ph,P(m- chemistry is documented with several examples NaOS-CaH4)PdClz and [P(o-tolyl)3],PdCl2 are (23). equally effective, but they are either more expen- Butler (24), one of the early workers in this area sive or not readily available. with Cullen (13), recently demonstrated that reac- A C-C coupling of aldehydes with a ‘Suzuki tions using P(i-P+ substituted ferrocenyl reagent’ (organic boronic acid) in the presence of phosphine provided very high yields of coupled rhodium catalysts was also successfully demon- #run$ products (Scheme V) (lb: R, R’ = i-Pr). strated recently by Miyaura, see Scheme IV, (22). The monosubstituted derivative (2a: R = i-Pi) also In this case, with dppf as hgand, 99 per cent con- gave very htgh yields, whereas dppf (la: R, R’ = version was obtained. The other bidentate llgands Ph) and its alkyl-aiyl mixed derivative,

ArI + [PdCIzL/LZ],NEtj. MeCN CuI- Ar-cooM,

-L- Yield, % la 7

Fe Fe lb 100 2a 96 3a 53

I R=Ph, R’=Ph la R = i-Pr 2a R = i-Pr, R‘ = i-Pr lb Scheme V R=Ph, R’=i-Pr 3a Heck coupling using electron-rich ferrocenyl phosphines

Pbtinwnr Metah Rm, 2001,45, (1) 25 + WZdbP1 lBlNAP R"Hz - I Naaf-Bu), 80'C -R --R' Yield, % p-NC Hex 97 Scheme VI p-Me Hex 86 Buchwald coupling involving a primar)?amine

Fe($C5H4PPh2)q5-CgH4P(i-Pr)2 (3a: R = Ph, R' = was the only one which gave consistently higher &Pi) gave only modest and moderate yields, yields of the Stille coupled products when aryl tri- respectively, indicating the importance of aliphatic flates were coupled with organostannanes (27). phosphine moieties in Heck chemistry. Subsequently Hartwig's high throughput Carbon-Heteroatom Coupling screening studies (25) using 45 structurally differ- C-N Coz@ng Using +pf ent phosphines indicated that P(t-Bu)j and The most prominent reaction in this area is car- di(t-butylphosphino)ferrocene, lc, are the two bon-nitrogen bond formation, commonly referred most active systems to date for the Heck olefina- to as Buchwald-Hartwig coupling (4, 28). tion of unactivated aryl bromides, and that Buchwald's work (29) in this area indicated that the di(t-buty1phosphino)ferrocene is the most efficient ligand BINAP (BINAP = 2,2'-bis(dipheny1phos- hgand for olefination of aryl chlorides. phino)-l ,l'-binaphthyl, existing in racemic and Fu's successful work on palladium-catalysed chiral forms) in combination with Pdzdba, Heck, as well as Suzuki and Stille couplings, using (tris(dibenzylideneacetone)dipalladium(O)) is capa- P(f-Bu)3, needs to be mentioned here (26), as it has ble of catalysing the aryl amination process rekindled the interest in these difficult arylchloride involving a primary amine (Scheme Vl). Use of the coupling reactions. However pharmaceutical com- conventional bidentate ligand, dppe or monoden- panies tend to avoid using P(~-BU)~as it is tate P(o-tolyl)j gave unsatisfactory results. extremely air-sensitive and undergoes oxidation if Concurrently, Hartwig (30) identified palladium proper care is not taken. complexes of dppf (that is PdClzdppf, Pd(OAc)z/dppf or Pd(dba)z/dppf) as second gen- SMe Corzplg eration catalysts for similar couplings. These StiUe also observed that PdClzdppf behaves in a complexes are capable of producing high yields of unique way in C-C coupling reactions. Of several coupled products with aryl halides and various ani- palladium phosphine catalysts tried in the study it line derivatives, see Scheme VII. Electron-rich,

WClzdppf/dppf DX+ HzNeR1 NaO(f-BU).- €6-1Oo~C R X = Br, I Yield 80-94.1. R = o-. ni-. p-OMe, Me, Ph Scheme VII R' = p-CI, Ph, H Hartwig coupling

R = OMe, Me, Ph Yield 80-94-1. ArOTf = 2-naphthyl triflate Scheme VIlI R' = H C-N coupling (Buchwald-Hartwig) involving aTl trij7ate

PIarinUmMetuLr Rm,2001,45, (1) 26 Yield ca. 95.1.

Fe PPh2 Scheme IX Highly eficient PPF-OMe (4)assisied C-N coupling e 4 of a secondary amine with t-Bu-CoHaBr electron-poor, hindered or unhindered aryl bro- product (although 43 per cent product could be mides or iodides all performed well in this obtained by using 5 mol% PdClzdppf and 15 molYo chemistry. Hartwig's attempt to use other biden- of dppf (34)). This limitation was overcome by tate ligands, such as bis(diphenylphosphin0)- Buchwald using another ferrocenyl phosphine hg- propane or bis(diphenylphosphino)bemene, in and, (*)-PPF-OMe, 4, which provided a yield of - these types of couplulg reactions were not success- 95 per cent, see Scheme IX, (28,34-35). ful in terms of producing hgh yields of the desired Couplulgs of aryl chlorides with cyclic and couphg products (31). acyclic secondary amines were also difficult with This chemistry has also been extended to the dppf and BINAP. The use of palladacycle 5 in the amination of aryl aiflates with anilines to give Me excellent yields, see Scheme WI, (32). However, electron-poor aryl triflates were susceptible to cleavage under basic conditions. This problem has been overcome by the slow addition of triflates (32) or by the use of the base CszCOs(33). R = ortho - tolyl The unique nature of dppf or BINAP could be associatedwith their steric bulkiness, which may be couplulg of CF3C&Cl with an acyclic amine pro- responsible for the slow rate of P-hydride elimina- ceeded in reasonable yield (60 per cent). When the tion in comparison with the reductive elimination cyclic amine, piperidine, was used the yield process. This would also prevent the formation of increased to 98 per cent (36). Reddy and Tanaka Pd-diamjne complexes. (37) used the electron-rich phosphine, PCy3, to Although there may be a few exceptions where couple chlorobenzene with a secondary cyclic BINAP behaves better than dppf, Hkdg found amine, N-methyl pipemine. Hartwig also per- that dppf is effective in many couplug reactions (4, formed the same type of chemistry very 30). Buchwald in his recent review states "while successfully with several substrates by using optically active BINAP is expensive, the fin- di(t-butylphosphino)ferrocene, lc, (38), while that (*)-BINAP is usually a suitable surrogate has Buchwald followed a similar approach by using the led to its commercial availability" (34). However, bulky PCy2 substituted biphenyl &and, 6, (39). dppf is less expensive than racemic BINAP and is much easier to synthesise and put+.

Limitations of@pf Neither dppf nor BINAP were effective for the amination of aryl bromides, such as Ct-butylbro- Interestingly, &and 6 has been useful even for mobenzene with di-n-butylamine and have couplulg electron-rich aryl chlorides. Subsequently provided only 8 to 9 per cent yield of the desired 2-di(t-buty1phosphino)biphenyl was found to be a

PhhmMet& Rm.,2001,45, (1) 27 Fe PPh, Fe KY2

Nucleophilic corbene, 9

good hgand by the same group. Hartwig has also About five years ago, a group reported a conve- used the ferrocene-based chelating aliphatic phos- nient and efficient synthesis of BINAP by a C-P phines, 7 and 8 originally prepared by Cullen (12a) coupling involving the ditriflate of binaphthol with and Butler (13), to couple an electron-rich aryl PhzPH or PhzP(0)H in the presence of a phos- chloride, MeC&I.&l, with amines, including a pi- phine complex of NiClz (46).Although dppf is a mary amine, n-BuNHz (38). All these studies good hgand for the same reaction, the authors did suggest that bulky electron-rich llgands in combi- not mention any special advantage of dppf over nation with palladium or nickel are extremely other phosphines. A recent non-catalytic study useful for difficult aryl chloride (Arcl) couplmg. In suggests that PdClzdppf, in the presence of this regaxd, Nolan’s original work with the nude- Pd(dba)z, is capable of forming C-P bonds by ophilic carbene ligand 9 is worth mentioning as he reductive elimination (47). However, this is an demonstrated a very efficient coupling of Arc1 area, which needs further exploration. with a wide variety of aliphatic cyclic and acyclic secondary amines, and aliphatic and aromatic Conclusion primary amines (40). The importance of dppf and related ligands in late transition-metal catalysed organic reactions are C-0, C-S and C-P Couphg fairly significant, especially in coupling reactions. Intramolecular C-0 bond formation lea% to The steric bulkiness, large bite angles (for chelating the formation of heterocycles containing 0 atoms ligands) and relative stability of the aliphatic substi- was reported by Buchwald using Tol-BINAP (To1 tuted ferrocenyl phosphines, in comparison to = tolyl) or dppf in the presence of Pd(0Ac)z (41). P(t-B+, are some of the special advantages of Haitwig reported the first intermolecular C-0 cou- these types of ligands which give fade reductive pling of aryl halides, leading to the formation of elimination without any undesired isomerisation ethers, using dppf in the presence of Pd(dba)z (42). (P-hydrogen elimination) leading to byproducts. For the latter reaction, the yields were greater than Many of the ligands such as dppf or its P(i-P+ or 90 per cent. Ni(COD)z, in the presence of dppf or P(t-Bu)* substituted analogs are commercially avail- Tol-BINAP, gave more or less identical yields (68 able, and their air and moisture stabilities increase to 98 per cent) for the formation of t-butyl, methyl further when they are complexed with palladium. and silyl aryl ethers (43). More details on C-0 and Ni(0) complexes also appear to be useful for C-S coupling using dppf ligands have been certain difficult coupling reactions. However, these reviewed recently (4). complexes are fairly difficult to make in large quan- Hartwig’s group (44) has recently identified the tities, and nickel is not a very environmentally in sitr/ formation of an interesting hgand PhSFcP(t- friendly metal for pharmaceutical processes. BU)~,10, by the palladim-catalysed perarylation of The other C-heteroatom coupling reactions are the cyclopentadienylgroup in PFc(t-Bu)z, 2b, (45). also important in the chemical and pharmaceutical This ligand is very useful for room temperature industries. A fuller review, where chiral applica- aromatic C-0 bond formation with yields of up to tions will be discussed in greater detail, is planned 99 per cent (44). for publication during 2001 (48).

PhfiinUmMefuLrRev., 2001, 45, (1) 28 Acknowlegdements 16 T. Hayashi, M.Konishi, Y.Kobori, M. Kumada, T. Thanks are due to Professor J. F. Hartwig (Yale University), Higuchi and K Hirotsu, J. Am. Cbem. Soc., 1984, Professor S. P. Nolan (University of New Orleans) and W. 106,158 Tamblyn (JohnsonMatthey) for valuable suggestions. Professor 17 M. Ogasawara, K. Yoshida and T. Hayashi, S. L. Buchwald @IT) is acknowledged for providing some of Opomet&J, 2000,19, 1567 his recent references at short notice. R Teichman aohnson 18 (a) T. Oh-e, N. Miyaura and A. Suzuki, Synktt, 1990, Matthey) is thanked for support and encouragement in this 221; @) T. Oh-e, N. Miyaura and A. Suzuki,]. Org. work. Cbem., 1993,58,2201 19 V. Percec, J.-Y. Bae and D. H. Hdl, J. 0%.Cbem., References 1995,60,1065 1 (a) G. P. Sollot, J. P. Snead, S. Portnoy, W. R 20 (a) M.Ueda, A. Saitoh, S. Oh-tani and N. Miyaura, Peterson and H. E. Mertoy, Cbem. Absfr., 1965,63, Tetrahedron, 1998,54,13079; (b) S. Saito, S. Oh-tani 18147b; @) J. J. Bishop, A. Davison, M. L. Katcher, and N. Miyaura,J. 0%.Ckm., 1997,62,8024 D. W Lichtenkrg, R E. Mdand J. C. Smart, J. 21 L. N. Pridgm and G. K. Huang, Tetrabedmn Lett., Oganomet. Cbem..,1971,27,241 1998,39,8421 2 R-S. Gan and T. S. Hor, in “Ferrocenes”, eds. A. 22 M.Sakai, M.Ueda and N. Miyaura, Angm Ckm. hit. To$ and T. Hayashi, VCH, New York, 1995, pp. Ed, 1998,37, (23). 3279 1-104 23 (a) K. Olofsson, M. Larhed and A. Hallberg, J. 0%. 3 T. Hayashi, in “Ferrocenes”, eds. A. Togni and T. Ch.,1998, 63, 5076; @) S.-K. Kang, S.-C. Choi, Hayashi, VCH, New York, 1995, pp. 105-142 H.-C. Ryu and T. Yamagu&J. Og. Cbem., 1998, 4 (a) J. F. Hanwig, Angw. Cbem. ht. Ed., 1998, 37, 63, 5748; (c) F. Ujjainwalla and D. Warner, 2046, (b) J. F. Hartwig, Am. Ckm. h.,1998,31,852 Tetrabedtun Lett., 1998, 39, 5355; (a) S. Cerezo, J. 5 T. Hayashi, Acc. Cbem. Res., 2000,33,354 Cortis, M. Moreno-Was, R Plekats and A. 6 C. J. Richards and A. J. Locke, Tetrahedron: Roglans, Tetrabednm, 1998,54,14869 Agmmehy, 1998,9,2377 24 A. L. Boyes, I. R. Butler and S. C. Quayle, 7 (a) A. Togni N. Bieler, U. Burckhardt, C. Kolher, Tertabedron Lett., 1998,39,7763 G. Pioda, R Schneider and A. Schuyder, Pm4p.l 25 K. H. Shaughnessy, P. Kim and J. F. HartwigJ. Am. Cbem., 1999, 71, (8), 1531; @) A. Togni, in Cbem. SOC.,1999,121,2123 “Metallocenes”, eds. A. Togni and R L. Halterman, 26 (a) A. F. Littke and G. C. Fu, Angew. Cbem. Int. Ed., Wiley, New York, 1998, pp. 686721;(c) A. Togni, 1998,37, (24), 3387; (b) A. F. Littke and G. C. Fu, R Dorta, C. Kolher and G. Pioda, PmAppL Ch., Anp.Cbcm. Int. Ed, 1999,38, (16), 2411; (c) A. F. 1998, 70, (8). 1477; (a) A. Togni, Ap.Cbem. Int. Littke and G. C. Fu, J. 0%.Cbem., 1999,64,10; (d) Ed En& 1996, 35, 1475; (e) A. To& Chimica, A. F. Littke, C. Dai and G. C. Fu,J. Am. Cbem. Soc., 1996, 50, (3), 86 2000,122,4020 8 L. Schwink and P. Knochel, Cbem. EM J., 1998, 4, 27 A. M.Echavarren and J. K Stille,J. Am. Ckm.SOL, (5), 950 1988,110,1557 9 H. B. Kagan and 0. Riant, in “Advances in 28 (a) B. H. Yang and S. L. Buchwald, ]. Organometal. Asymmetric Synthesis”, ed. A. Hassner, JAI Press Cbem., 1999, 576, 125; @) S. L. Buchwald and A. Inc., 1997, Vol. 2, pp. 189-235 Guram, US.Patent 5,576,460;1996 10 M. Sawamura and Y. Ito, CbemRsv., 1992,92,857 29 J. P. Wolfe, S. Wagaw and S. L. Buchwald, J. Am. 11 D. Seyferth and H. P. Withers, O~anome~,1982, Cbem. Soc., 1996,118,7215 1,1275 30 M. S. Driver and J. F. HWJ.Am. Gem. Soc., 12 (a) W. R Cden, T.-J. Kim, F. W. B. Einstein and T. 1996,118,7217. Jones, Organometahs, 1985, 4, 346; @) T. Hayashi, 31 J. F. Harewig, Syktt, 1997,329 M. Konishi, M. Fukushima, M. Mise, T. mtani, 32 J. Louie, M. S. Driver, B. C. Ham- and J. F. M. Tajika and M. Kumada, J. Am. Cbem. Soc., 1982, H-J. 0%.Cbem., 1997,62,1268 104, 4962; (c) A. Davidson and J. J. Bishop, 1nor.g. Cbcm., (d) A. Davidson and J. J. 33 (a) J. P. Wolfe and S. L. Buchwald, Tetrabedmn Lett., 1971, 10, 826; @) J. P. Wolfe, H. Tomori, J. Yin, J. Bishop, Inez. Cbem., 1971,10,832; (e) A. W. Rudie, 1997,38,6539; D. W. Lichtenberg, M. L Katcher and A. Davidson, Sadighi and S. L. Buchwald,J. 0%.Cbem., 2000,65, Inotg. Cbem., 1978,17,2859 1158 Butler, W. R Cullen, T.-J. Kim, S. J. Retiing 34 J. P. Wolfe, S. Wagaw, J.-F. Marcoux and S. L. 13 I. R Buchwald, An. Cbem. Res., and J. Trotter, OtganomehIkcs, 1985,4,972 1998,31,805 J.-F. Marcoux, Wagaw and S. L. Buchwald,J. 0%. 14 (a) T. J. Colacot, R A Teichman, ,R Cea-Olivareas, 35 S. J.-G. Alvatado-Rodriguez, R A. TOSC~~Oand W. J. Cbem., 1997,62,1568 Boyko, J. Oxanomed. Cbem., 1998,557,169;@) T.J. 36 M.Beller, T. H. Riermeir, C.-P. Resinger and W. A. Colacot, R J. Fair and W. J. Boyko, Pbo~pboms,St@r Hermann, TefrabedmnLett, 1997,38,2073 SihRe&. Ekm., 1999,114116,49 37 N.P. Reddy and M. Tanaka, Tetrabedmn Lett., 1997, 15 B. Bildstein, M.Malaun, H. Kopacka, K. Wurst, M. 38,4807 MitterbGdr. K-H. Ongania, G. Opromolla and P. 38 B. C. Hamann and J. F. H-J. Am. Cbem. Soc., Zanello, Otganometa&ics, 1999,18,4325 1998,120,7369

PhhmMetah Rm, 2001, 45, (1) 29 39 D. W. Old, J. P. Wolfe and S. L. Buchwald, J. h. 46 (a) D. Cai, J. F. Payack, D. R. Bender, D. L. Hughes, Cbem. Sot., 1998, 120, 9722 T. R. Verhoeven and P. J. Reider, J. 0~.Cbem., 1994, 40 J. Huang, G. Grasa and S. P. Nolan, 0%.Lett., 1999, 59, 7180; @) D. Cai, J. F. Payack and T. R. 1,1307 Verhoeven, U.S.Patent 5,399,771; 1995 41 M. Palucki, J. P. Wolfe and S. L. Buchwald,]. Am. 47 M. A. Zhuravel, J. R Moncarz, D. S. Glue&, IC-C. Cbem. Sot., 1996,118, 10333 Lam and A. L. Rheingold, Otgmome&, 2000,19,3447 42 G. Mann and J. F. Hartwig,]. Am. Cbem. Sot., 1996, 48 T. J. Colacot, ‘A Concise Update on the 118,13109 Applications of Ferrocenyl Phosphines in Homogenous Catalysis’, Cbem. Rev., to be published 43 G. Mann and J. F. Hartwig,J. Otg. Cbem., 1997, 62, 5413 The Author 44 Q. Shelby, N. Kataoka, G. Mann and J. F. Hartwig, Thomas Colacot is a Development Scientist at Johnson Matthey in West Deptford, U.S.A. His interests include /. Am. Cbem. SOL,2000,122, (43), 10718 organometallic catalysts for chiral and non-chiral applications 45 M. Miura, S. Pivsa-Art, G. Dyker, J. Heiermann, T. and the evaluation of catalysts for organic transformations Satoh and M. Nomura, Gem. Commun., 1998,1889 using high throughput screening.

The 2000 MacRobert Award for the Platinum CRTm The MacRobert Award is the premier prize in the diesel exhaust into less harmful carbon for engineering innovation in the U.K. and is dioxide and water. awarded anndy by the Royal Academy of While the CRFconcept was patented in Engineering to a team responsible for a world- 1989, it could not be commercialised because the lea- engineering development demonstrating diesel fuel then available had a high sulfur con- technological achievement, successful commer- tent which inhibited the generation of nitrogen cial exploitation and benefit to the community. dioxide. The breakthrough occurred in the early In 2000 the MacRobert Award was won for the 1990s when Sweden introduced low-sulfur fuel second time by Johnson Matthey, this time for in response to environmental concerns. Low sul- the diesel emission control system known as the fur fuel and the CRTW are now sold across Continuously Regenerating Trap (CRT*). This Europe, in the U.S.A. and in Japan. revolutionary system has enabled trucks and The MacRobert Award coincided with the buses to control the pollution emitted by their fifth anniversary of the commercial launch of diesel-powered engines, especially the particulate CRY, first described in this Journal in a paper matter (soot), the health impacts of which are by Pelham Hawker (2). Hawker is a member of causing increasirig concern. the winning team, along with Piir Jones and the The MacRobert Award was first presented in co-inventors of CRF, Barry Cooper and Jim 1969, when it was shared between Rolls-Royce, Thoss. Barry Cooper was also in the team which for the Pegasus engine used in the Harrier jump- won the MacRobert Award in 1980 and so jet, and Freeman, Fox and Partners for the Sevem becomes the first person to win the Award twice. Bridge near Bristol. Johnson Matthey won the To celebrate the Award, Johnson Matthey Award in 1980 with its catalytic converter tech- has produced a special commemorative report, nology for passenger cars (1). Other winners “CRT5: Fifth Anniversary Publication”. Copies have included BP, British Gas and ICI. of this may be requested fiom: Ms Vanessa The modular CRFcomprises a filter down- Bystry, Johnson Matthey CSD, Orchard Road, stream of a specially-formulated platinum catalyst. Royston, Herts SG8 5HE, U.K; Fax: +44 1763 The CRY udlises the discovery that nitrogen 253 475 or E-mail: [email protected]. dioxide bums soot at temperatures typical of R. J. D. EVANS diesel exhaust, 2 275°C. The innovative design References of separating catalyst and filter sees the platinum 1 Phtjmm Metub Rev., 1981,25, (l),22 catalyst convert nitric oxide normally present in 2 P. N. Hawker, Plarnum Metuh Rev., 1995, 39, (l), 2 diesel exhaust into nitrogen dioxide. This is then used to bum the diesel soot trapped on the filter. The Author Robert Evans is the Marketing Manager for the Johnson Matthey The platinum catalyst also converts over 85 per Catalytic Systems Division. His interests lie in vehicle emissions cent of the hydrocarbons and carbon monoxide control systems, particularly retrofit applications.

Pbtinum Metub h.,2001, 45, (1) 30 21 st Century Emissions Technology REVIEW OF AN INSTITUTION OF MECHANICAL ENGINEERS CONFERENCE ON EMISSION CONTROL

The Combustion Engines Group of the (SCR) of NOx for use in the aftertreatment of Institution of Mechanical Engineers (IMechE) heavy-duty diesel emissions. Searles also sun- held a conference on ‘21st Century Emissions marised work on hydrocarbon-absorbers, electrically Technology‘ at their London headquarters on the heated catalysts, and on active and passive NOx. 4th and 5th December 2000. Nearly 100 partici- The technologies currently available for passen- pants from the U.S.A., Japan and most European ger cars and larger vehicles were reviewed by countries gathered to hear 23 excellent talks and to Timothy Johnson (Corning, U.S.A.). He discussed discuss engine and aftertreatment technologies. developments in various catalyst supports (made The major theme of the conference was the of cordierite) and trends, such as: need for ongoing research in emissions reduction advanced integration of catalyst and engine strategies and technologies for both on-hghway management transport and off-road mobile machinery. The lower ammonia emissions from gasoline vehicles conference was thus a forum for the lea- better cold start response experts fkom motor manufacturers, oil companies, hybrid (or layered) catalysts and vehicle testing houses and universities to discuss PGM flexibility. the reduction of particulate matter and nitrogen Johnson noted that flexibility in using the PGMs is oxides, NOx, in order to meet the forthcoming an important new concept for major automobile stringent European and U.S. federal emissions leg- manufacturers. This will help to ease cost volatility islation. Vehicle emissions can form a large part of by substitution of one metal for an equally active the measured pollutant levels in ambient air, thus, one, where possible. This might lead to a need for this review examines the role that catalyst systems, certification of multiple catalyst systems at the in- based on platinum group metals (PGMs) play in tial design phase and production testing of ensuring the continual global lowering of vehicle vehicles, and would ultimately result in cost sav- emissions. ings for most parties. The costs of various SCR systems were assessed Emissions Control Technology for by James Warren (The Open University, U.K.) for 2000-2010 Euro 5 heavy-duty diesel trucks. It was shown that Robert Searles (AECC, Bebum) addressed the most long-haul transportation trucks can ‘pay challenges to and opportunities for catalyst tech- back’ the complete cost of the catalyst system nology in the 21 st century. He hlghlrghted the need within one to two years if fuel savings of 3 to 5 per for cleaner fuels, with lowered sulfur levels, which cent are achieved, by tuning the engine for higher, enhance and make possible the use of more raw (precatalyst) NOx emissions, and then choos- sophisticated catalyst systems, such as NOx traps ing an appropriate catalyst and control system. and particulate filters. He mentioned the launch of A possible way of reducing NOx via engine the new Peugeot 607 diesel passenger car, which is method alone was presented by Patrick Hynn an industry lirst for a European diesel passenger (Cummins Engines, U.S.A.). He described work car to have a particulate filter system. There was on exhaust gas recyclmg (EGR) which clearly indi- speculation about whether a strategy of using non- cates that combustion chemistry is the limiting continuous regeneration with a fuel-borne catalyst, factor in determining the minimum NOx pro- and an appropriate conventional platinum-based duced in both gasoline and diesel engines (heavy catalytic converter would be a realistic way forward duty, cylinders > 1 litre). The minimum levels of for all classes of passenger cars. He reported grow- NOx achievable are listed in the Table, along with ing interest in the selective catalytic reduction the proposed European and U.S. fedeia limits. His

Pbrinwm Metah h.,2001,45, (l),31-33 31 of oxidation catalysts and filters, showed that SourcelStandard NOx, g (kW h)” I SourcelStandard I NOx, g (kW h)” I vehicles fitted with these devices were capable of Lowest possible by Lowest possible by achieving very low particulate mass emissions. I engine design (SI) I - 0.56 I Under all conditions tested, the CRTm consistent- Lowest for diesel 1.12 ly reduces particulate mass. However, futther work I Lowest for diesel I - 1.12 I - on the characterisation and measurement of par- Europe 2008 (proposed EU 5) Europe 2008 (proposed EU 5) 2.0 ticulate is required both to establish the origin of U.S.A. 2007 (proposed) any particulate observed after filtration, and to find U.S.A. 2007 (proposed) 0.15 11 11 a standard set of measurement conditions on talk clearly demonstrated that there is a vital need which all test houses can agree, for possible future for all types of aftertreatment, especially to comply legislation and correlation. with the very low U.S. limits. He concluded that The post-catalyst exhaust gases from gasoline- even with the best possible engines using EGR, powered vehicles (aiming at SULEV (super ultra aftertreatment will still be required to meet the 0.1 5 low emission vehicle) emissions) are so clean as to g (kW h)-’ NOx limit proposed for the US. in be almost immeasurable with some of today’s 2007. devices. Indeed, in some instances the exhaust gas Another route to lowered NOx levels is offered has been cleaner than the intake ambient air. This by the non-thermal plasma (NTP) technique. illustrates the need for more advanced quantitative Hermann Breitbach (Delphi, Luxembourg) methods for measuring evaporative hydrocarbons, showed that a potential NTP system, coupled with particulates and other pollutants. a zeolite-based catalyst, can reduce emissions from passenger cars. Currently, when running the NTP Future Trends in Engines system on a car, - 300 W (- 1 kW at peak condi- Compressed natural gas (CNG) and controlled tion) is required to generate good dielectric auto-ignition (CAI> were among other engine/fuel behaviour. This results in a fuel penalty of - 3 per powertrains described. Both promise potentially cent. However, with the future 42 V electrical sys- lower NOx emissions. while gaseous fuels are cur- tems, coupled with integrated starter motors, NTP rently relatively inexpensive, the potential emission in cars will be much easier to integrate and to of methane from such engines will need to be supply with power. addressed catalytically. CAI gives NOx values as low as 10 ppm, but system control is extremely dif- Diesel Particulate ficult, and CAI has not yet been fully demonstrated Diesel particulate and its measurement - down in a running vehicle. to aerodynamic particle diameters of - 7 nm - Paul Kapus (AVL, Austria) reviewed work on remains of strong interest to engine manufacturers the ‘G90’ vehicle. The ‘G90’ is a modified GM/ and, indeed, to the public at large. The use of Vauxhall/Opel Corsa with a typical fuel consump- CRTm (Continuously Regenerating Trap) systems, tion of 5.7 litres/lOO km (as purchased). After containing a platinum-based catalyst and particu- modifications to body shape (for superior aerody- late fiter, is well established for particulate namic drag) and transmission, and the addition of reductions. variable valve actuation, along with partial down- The characterisation of particles from heavy- sizing, the fuel consumption was reduced to 3.9 duty diesel (HDD) and hght-duty diesel (passenger litres/lOO km and COz emissions were lowered cars) was examined by Barbara Wedekind (Ricardo from 137 to 90 g km?. This shows that the way Consulting Engineers, U.K.). She also discussed forward to enable engines to meet COZlimits will the effects of a CRPon a Euro 2 HDD, as well be a smart combination of technologies. as the effects of diesel particulate filters on a selec- The views of Toyota on hybrid powertrains, tion of passenger cars. Work on the Peugeot 607, were presented by Tokuta Inoue (Toyota and VW Golf and Peugeot 406, all fitted with a variety Genesis Research Institute, Japan). He described

Phtinnm Metah Rm, 2001,45, (1) 32 the Prius, Toyota's hybrid elecaic vehicle (HEV). cles will remain for trucks/transport of goods). In Currently, the Prius (second generation coupled to other areas multiple solutions are possible, with a gasoline internal combustion engine) contains a fuel cells and hydrogen-based fuels expected to new rectangular battery module (21 kWj coupled eventually gain a large part of the market share. to a 33 kW gasoline engine. This delivers 3.4 Hybridisation and hybrid vehicles will begin to litres/lOO km under the Japanese driving test. play a prominent part in powertrains, with elec- When compared to a pure electric vehicle, this mc/fuel combinations being prominent. Cleatly, HEV has a longer driving range, good fuel econo- the variety of powerttain combinations will have my and good drivability without the need for an effect on the catalyst systems they use. Future recharging. The year. 2001 Prius meets the developments will need to take all component into Japanese and U.S. SULEV emissions, as well as consideration (filters, catalysts, monitors, sensors, the Euro 4 regulations. The Prius is the first fuels, etc.) and to maximise any synergistic effects Toyota vehicle, and perhaps one of the first-ever to achieve the lowest overall emissions, and the production vehicles, to use a catalyst support of lowest possible CO2 levels for their class. Vehicle 900 cells inch-', wall thickness 0.5 mm, carrying a designers and component suppliers will probably palladium and rhodium catalyst. The increase in work together closely to achieve cost-effective hghly active geometric surface area has been opti- solutions. In general, consumers will increasingly mised together with an - 19 per cent lower total demand comfort, safety, cost reductions, good dri- catalyst volume than prior systems. It contains a ving performance, enhanced durability, reliability hydrocarbon absorbing component to assist and low emissions. However, the catalytic con- hydrocarbon capture at low temperatures with verter will clearly remain the main pollution- subsequent oxidation after hght-off is complete. control device for the next generation of vehicles, although, 15 years from now, it may not be recog- Future Vehicles and Technologies nisable in its present form. It is expected that future vehicles will include The papers presented at this conference will be more models with direct injection (gasoline and published in Spring 2001 in the IMechE Seminar CNG) with advanced variable valve timing. publication series. Information can be found at: Powertrains will be based more on combinations http://www.imeche.org.uk. J. P. WARREN of technologies, such as turbo-charged CNG, CAI with direct injection, and CNG with direct injec- James Warren is a Staff Tutor/Lecturer in the Faculty of Technology at the Open University, based in Cambridge. His tion. The market will become segmented with interests are in automotive supply chain systems, sustainable some sectors finding unique solutions WDvehi- transport and vehicle exhaust gas purification. Palladurn Cross-Coupling Reaction for Brain Tracers Brain imaging via positron emission tomography 826S8273). The Sde methylation involves a palb (PET) using the short-lived "C positron emitter dim-promoted cross-coupling reaction of methyl (half-life - 20 minutes) requires a fast chemical reac- iodide and aibutyltin derivatives of tolylisocarbacy- tion to incorporate the smd amounts of "C into a clins (TICS); the TIC binds to the IpZ receptors. In carrier (tracer) which delivers it to the tissue under one methylation, which is a novel stepwise opera- examination. tion, an initial methylpalladim complex is produced Researchers in Japan and Sweden have now and is then mixed with other materials for the cross- developed a new rapid, efficient Stille methylation of coupling. The Pd promoter is a Pd(0) complex arylstannanes which produces a structure system generated from Pd~(dba)~and P(cKH~C~~)~in the that can deliver sufficient quantities of "C to presence of CuCl and KzCOS.The synthesis is high- prostaglandin receptors (IPS in the brain (M. Suzuki, ly reproducible, and with "C incorporated, results in H. Doi, K. Kato, M. Bjorkman, B. Lhgstrom, Y. a ["q-labelled PET tracer with radioactivity of sev- Watanabe and R Noyori, Teinzhedrnn, 2000,56, (42), eral GBq, which can be injected intravenously.

Plnlinwn, Met,& Rcv., 2001,45, (1) 33 Improved Start-up for the Ammonia Oxidation Reaction ELECTRICAL HEATING DEVICE FOR PLATINUM-RHODIUM GAUZE CATALYSTS AND NEW PROCEDURE REDUCES EXPLOSIVE HAZARDS AND PLATINUM LOSSES AT START-UP

By V. I. Chernyshev and S. V. Zjuzin JSC GIAP, Moscow, Russia

The start-up operation in a nitric acid plant is one of the most important stages, from the viewpoint of safety and platinum loss, in the entire ammonia oxidation process. Usually,flame burners using hydrogen or hydrogen-containing gas preheat the platinum alloy gauze catalyst to the operating temperature. However; there are disadvantages and peculiarities in this method of initiating the start-up reaction. These are discussed here and a new electrical heating device and a new technique are described for preheating the platinum alloy gauze catalyst. The device and technique are free of these disadvantages, and together they reduce the explosive hazard and platinum losses during start-up. Results from their commercial utilisation over a 12-year period at various nitric acid plants are described.

The ammonia oxidation process has been used fed into the reactor, as it has been preheated by the in nitric acid production since the start of the combustion gases. When the temperature reaches twentieth century. As early as 1902, it was shown 600°C (visible red glow) ammonia is mixed with that the most promising catalysts for this process the technological air (4). Hydrogen combustion is were platinum alloys (1) and the optimal form for continued until the ammonia oxidation process is the catalyst was found to be gauze, fabricated from observed to start. This apparently simple start-up wires of diameter 0.06-0.09 mm, and placed in operation will be looked at in detail. stacks (2). Today, knitted or woven phtinum alloy gauze is used as the catalyst for the production of Hydrogen Oxidation by Oxygen nitric acid and prussic acid, and also to produce Using Burners hydroxylamine sulfate. The homogeneous oxidation of hydrogen using The initial stage of the ammonia oxidation oxygen which takes place during start-up in an process for nitric acid production begins when an ammonia oxidation reactor has been studied for a ammonia:air mixture (AAM) at a temperature of long time (5) and can be described by a number of 80-200°C is input into a reactor in which platinum chain reactions which take place in the free space alloy gauzes are installed. The catalyst must be pre- above the gauzes in the reactor, as well as on the heated to 250°C prior to the start of the ammonia catalyst surface. The main reactions can be oxidation in order to change this process into a described as follows: high-temperature diffusional regime (3). Various 'H + O2-+ 'OH + '0 techniques are used to preheat the catalyst. In (0 '0 + H2 + 'OH + 'H commercial nitric acid plants one of the most (fi) 'OH + H2 + HzO + 'H applied techniques is to use the heat from burning (iii) hydrogen or hydrogen-containing gases. The burn- The outcome of reactions (i), (ii) and (iii) is an ers used are in the form of perforated tubes increase in the concentration of free hydrogen mounted in the reactors near to the gauzes. These atoms which occurs as a geomeaic progression. burners can either be fixed or rotating. Only 'tech- The free atoms 'H, '0 and the 'OH radicals are nological air' (air pumped from a compressor) is active intermediate products of the chain reactions

Phinnm Met& Rm,2001,45, (I), 3440 34 and easily recombine either in the volume or at the activity to the desired reaction (vii). This phe- surface of the catalyst to eventually become the nomenon bears testimony to an idea that the stable molecules: H20, 02and HzO2. However, recombination reactions of atoms and radicals for the hydrogen oxidation process the recombi- produced by the hydrogen flame on the catalyst nation reactions of 'H atoms are of main interest: surface (Equations (iv) - (vi)) are the dominant reactions in preheating the catalyst. However, 'H 02 M + 'HOz M + + + (iv) these reactions also disable the active centres of where M is an arbitrary partide. It follows from the catalyst which are common and not dependent Equation (iv) that chain breakage of reactions (i) on the chemical character of the combustible gas and (ii) in the volume does not result in the for- (in this case hydrogen or ammonia). mation of a stable molecule. A new type of Even though Equation (vii) is a promotor reac- peroxide radical is formed which contains exces- tion with respect to Equation (viii) (7) and sive chemical energy and is a long-lived although during preheating the surface of the plat- intermediate product. This 'HOz radical undergoes inum alloy catalyst has a uniform glow, dark spots recombination reactions: are often observed on the catalyst surface after the hydrogen to the bumers is switched off. Such 'HOz + HzO + HzOz + 'OH (v) spots are due to side reactions (Equations (iv) - 'HOz + H202 + H20 + 02+ 'OH (4 (vi)) when atoms and radicals from the hydrogen Reactions (v) and (vii describe processes which flame recombine. This well-known negative effect occur at the surface of the gauze and produce con- increases considerably if the catalyst contains siderable amounts of heat. impurities and poisons. At the same time as the above processes are During the start-up period, which sometimes occurring, the heterogeneous oxidation of the lasts for 10 or more minutes, ammonia passes hydrogen - which did not react accordtng to through unactivated areas of the catalyst surface Equations (ii) and (ii) - is taking place on the plat- without being oxidised, while at the active surface inum alloy gauze surface: areas of the catalyst it is oxidised into nitrogen oxides in the usual manner. On the downflow side 2H2 + 02 2H20 + (vii> of the catalyst this unreacted ammonia reacts with When the temperature of the platinum alloy the nitrogen oxides to form nitrite-nitrate com- gauze exceeds 25OoC, ammonia oxidation begins pounds of ammonia which tend to collect in (6): stagnant areas of the equipment and can form a hazardous explosive situation. Such explosions 4NH3 + 502 + 4NO + 6H20 (viii) have caused breakdowns in nitric acid plants 4NH3 + 30, + 2N2 + 6H20 C=) resulting in prolonged downtime. Fatal accidents 4NH3+ 402 + 2N20+ 6H20 (4 are also known to have occurred. Using hydrogen These reactions have different thermal effects as the combustion gas to start-up the ammonia which eventually define the temperature of the oxidation is also an explosive hazard and this too platinum alloy gauze catalyst. has caused accidents and breakdown in equipment. Drawbacks of Flame Burners for Another considerable disadvantage of flame Start-up of Ammonia Conversion burners is the so-called 'heat wear' of the platinum Some conclusions can be drawn from the alloy catalyst which can result in a bum-out of above simplified analysis. During the start-up peri- local areas of platinum alloy gauze during the start- od in a commercial ammonia oxidation reactor. up period. This causes additional platinum losses. when the activity of the platinum alloy catalyst is Such heat wear of the platinum alloy catalyst, espe- not high enough, the use of flame burners masks cially in the upper gauze, is induced mainly by local the progress of the process towards increased overheating to temperatures above the boiling

Phtinnm Metah Rev., 2001, 45, (1) 35 Fig. I An assembled pack of platinum-rhodium gauzes, 1.9 m diametec showing the heating elements of the electrical ignition device mounted radially on the puck surface. This EID is installed in a Sumitorno concentrated nitric acid plant owned by Nitrogenmuvek Rt. in Varpalota. Hungary points of the platinum materials, due to recombi- requires a source of pressurised hydrogen, if the nation reactions of atoms and radicals in the ammonia synthesis plant does not provide hydro- hydrogen flame, which have a hgh thermal effect gen-containing gas from one of its intermediate equations (iv), (v) and (vi)). Overheating in stages. localised areas of the platinum alloy catalyst is probably also due to the non-uniform distribution New Procedure and Electrical Device of the hydrogen flame over the gauze catalyst sur- for Start-up of Ammonia Conversion face, for example, because of imperfect burners All the above circumstances defined the and the design of the AAM flow distributors. research that was devised, directed and participat- An analysis of 50 Russian nimc acid plants has ed in at GIAP (8). The main aim of the research lay shown that unrecoverable platinum losses occur in fin- new engineering solutions.which could only during the star-up, due to using hydrogen help towards avoiding the use of hydrogen he flame burners. The platinum losses total 0.001 to burners in commercial ammonia conversion reac- 0.0015 per cent by weight or, with respect to the tors. The investigations enabled us to create a productivity of all the plants in Russia, 10 to 12 kg unique method and devices for electrically heating annually (the average daily expected output of each isolated areas of platinum alloy gauzes, stacked in plant analysed is 355 tonnes of nitric acid). packs, to initiate the ammonia conversion reaction There are other disadvantages when using over the whole surface of the catalyst in the short- flame burners for initiating the ammonia oxidation est possible time (9, 10). reaction. One is the possibility of ammonia pre- This new electrical ignition device (ED)uses catalysis which can take place on the exterior linear heating elements arranged in a unique man- surfaces of the burners, which receive additional ner on the surface of the platinum alloy catalyst heat as radiation from the hot platinum alloy which needs to be ignited. The positioning of the gauzes. Last, but not least, the start-up reaction heating elements on the surface depends on the

Phtinum Met& Rm, 2001,45, (1) 36 I I also achieves safe electrical insulation and prevents Reactor Performance Data fri a Reactor at AAM leakage during reactor operation. the JSC Kirovo-Chepetsky CF iical Company Commercial implementation of EID then AAM consumption (STP) 66,000 m3 h-’ began simultaneously at three UKL-7-type nitric AAM temperature at start-up 130T acid plants: at JSC ‘Dorogobouzh‘, Dorogobouzh, AAM temperature during Smolenskaya obl., Russia; JSC ‘Achema’, Jonava, stationary periods of operation 2OOOC Lithuania and at Nitrogenmuvek Rt., Varpalota, Ammonia concentration 11 vol.% Hungary. Number of gauzes in pack 12 During a 6-year period the Hungarian enterprise Total weight of gauzes in pack 24 kg successfully used EIDs, specially designed for a Gauze pack operating diameter 1650 mm Sumitomodesignedconcentrated nitric acid reactor I I I (0.8 MPa pressure), see Figure 3. The operating diameter of the gauze pack was 1.I) m. Even though plant are given in the Table. The ammonia conver- the catalyst surface in this Sumitomo reactor is 40 sion reaction was started up with values for the current and voltage of 31 A and 180 V, respectively. The time taken for the spread of the reaction from the initial local areas to all the catalyst surface was about 1 minute which was somewhat longer than the calculated 25 seconds. This emphasised the point that effective work using EIDs requires very pure platinum alloy catalyst. Hence, subsequent start-up operations were preceeded by special activation of the platinum alloy gauzes, using a technique devised by the authors (11). After such activation the time taken for the initiat- ed Iocalised reaction areas to spread over all the catalyst surface was 20 to 25 seconds. This technique was also successfully applied to activate the fouled gauzes. Over a two year period, 15 starts-up were performed using the ED. The state of the electrical insulation of the EID and the state of the catalyst surface were inspected each time the plant was shut down. The experience gained was used as the basis for designing commercial EIDs which have two ways of inputting electrical power to the heating elements: through either the upper or lower parts of the reactor, see Figures 3 and 4, respectively. Fig. 3 Schematic of an ammonia oxidation reactorfor For the UKL-7-type nitric acid plant, inputting concentrated nitric acid production. The plant is a power via the lower part of the reactor is more Sumitomo design belonging to Nitrogenmuvek Rt. in convenient both for assembly and operation, as Vurpulolu, Hungury. The electrical input is through the upper part of the shell. there is no need to assemble and dismantle the I - lowerflange of the shell ofthe reactor electric power input device (assembly 2 in Figuies 2 - electric input device 3 - heuting wire 3 and 4) when opening the reactor to replace spent 4 - insulating tubes platinum alloy gauzes. This method of assembly 5 - Pi-Rh gauze pack

Phtinum Met& Rey., 2001,45, (1) 38 Fig. 2 A view of the four parallel heating elements of an electrical ignition device installed in a UKL-7 ammonia oxidation reactor: The elements are - 500 mm apart. The UKL-7 is a Russian-designed non-concentrated nitric acid plant and this particular one belongs to JSC 'Achema' in Jonava. Lithuania performance characteristics of the reactor and on passing through the gauzes. This reduction is the design of the catalyst pack, see Figuies 1 and 2. achieved by decreasing the initiation period and The heating elements are made from hgh elecm- preventing the undesirable recombination reac- cal resistance metal alloy, in wt.%: C < 0.12, Cr = tions of the 'H and '0 atoms and the 'OH and 27, Al = 5, Ti < 1, Fe remainder. They are catalyt- 'HOz radicals, as well as HZoxidation. These block ically inactive and encased in porcelain tubes for the active centres of the catalyst which are meant electrical insulation. The external diameter of an to be converting ammonia to NO. element is less than 5 mm. An increase in the yield of NO, due to pre- The elements are heated electrically (for exam- venting ammonia precatalysis @recatalysis usually ple, 220 V at 50 Hz) and monitored throughout. takes place on the exterior surfaces of the When in use, the EID starts up reactions (viii), (ix). burners); and (x) only on the catalyst surface. The technique an increase in the service life of the catalyst we devised for initiating the ammonia conversion gauzes by preventing damage caused by heat and reaction, incorporates the following by preventing the gauze being fouled by oil and a value for the electric power which evolves per ferrous oxides in the hydrogen-containing gases unit length of the electric heating element used in the burners, and a number of EID switches in the electric circuit freedom from using hydrogen-containing gas periods of time when the switches are on, and as a method of stariing up the reactor. local areas of the catalyst surface which can be served by a single heating element of the ED. Results of Commercial Operations The values of these intervals are determined by The first test of commercial EIDs was carried the parameters of the actual process of ammonia out in 1987 at JSC Kirovo-Chepetsky Chemical conversion, catalyst compositiqn and gauze Company's mineral ferdliser works (ii Russia) design. Using this new technique gives: using a single-pressure (0.716 MPa) nitric acid a reduction to 10 to 60 seconds in the initiation plant with a daily output of 355 tomes of nitric period for the ammonia conversion reaction over acid. EIDs were installed into a reactor. the whole catalyst surface, the upper value being The electrical heating components included for large reactors using platinum alloy gauze cata- four linear heating elements atranged at intervals lysts with diameters exceeding 2.5 m, and of 400 mm on the catalyst surface. For the first a reduction in the risk of explosions - by cut- test an autotransformer was provided in the mon- ting down the amount of non-reacted ammonia itoring system to control the power. Data from the

PLztitwmMetuLr Rm., 2001,45, (1) 37 2.7 m. The EDfor this reactor consisted of four linear parallel heating elements spaced 500 mm apart, as is also shown in Figure 2. Start-up was performed under the following conditions:

AAM temperature: 170°C Ammonia concentration: 5 vol.% The time for initiating the reaction did not exceed 60 seconds. The methods and devices described here have been used successfully at nitric acid plants in Russia, Lithuania, Hungary and Greece for over 12 years. Figures 5 and 6 show some results from industrial tests performed at the Russian UKL-7

i I

-'E 15w.1000. xA Pz- 500 .x/--y 2 Fig. 4 Schematic of an ammonia oxidation reactor with electrical input through the lower part of its shell. The plant is a 0.716 MPa (UKL-7) single-pressure nitric acid 123 i 5 6 7 e 9 10 11 i2 plant being operated in Russia. NUMBER OF GAUZES IN CATALYST PACK I - lowerflange of the shell of the reactor 2 - electric input device Fig. 5 The dependence of the power evolved per unit 3 - heating wire length of heating element on the number of gauzes in the 4 - insulating tubes catalyst pack for various reactors: 5 - Pt-Rh gauze pack Grande Paroisse, gauze operating diameter 2.7 m Sumitomo, gauze operating diameter 1.9 m rn UKL-7, gauze operating diameter 1.65 m per centlaiger than the catalyst surfacein the Russian x pilot unit, gauze operating diameter 0.05 m -7 reactor, the initiation period for both reactors is almost the same. The start-up operation for the Sumitomo plant occurs under following conditions: AAM consumption: 56,000 m3 h-' AAM temperature: 200°C Ammonia concentration: 8 vol.% Commercial EID implementation was found to give more advantages to woven gauze than to knitted gauze. A new commercial EID design has been used I VELOCITY OF AMM0NIA:AIR MIXTURE, mi' in an ammonia conversion reactor at the Grande Fig. 6 The dependence of the power evolved per unit Paroisse nitric acid plant belonging to Chemical length uf heating element on the ammonia:air mixture Industries of Northern Greece, in Thessaloniki. velocity, for various reactors: Grande Paroisse, gauze operating diameter 2.7 m This smgle-pressure plant (0.4 Mpa pressure) uses Sumitomo, gauze operating diameter 1.9 m platinum aUoy gauze catalyst of operating diameter UKL-7, gauze operating diameter 1.65 m

Pkdnwm Metuls h.,2001, 45, (1) 39 nitric acid plant. The power evolved per unit The Authors length of heating element versus the number of V. I. Chernyshev is the General Deputy Director of JSC GlAP in Moscow. His interests are nitric acid manufacture, nitrogen-based gauzes in the catalyst pack is shown in Figure 5, fertilisers and reactors for heterogeneous chemical processes. while the power versus linear velocity of the AAM S V Zjuzin is a Leading Scientist at JSC-GIAP in Moscow. He is interested in ammonia oxidation reactors and nitric acid production. is shown in Figure 6.

Conclusions Ammonia Reactions on Ruthenium Studying ammonia (NH3) decomposition helps in The experience gained from implementing understanding the kinetics of NHl synthesis and con- commercial EID has produced data which have mbutes towards cleaning up NH, emissions from been used for the design of devices for ammonia sewage and activated sludge. For nearly a century iron conversion reactors working under a wide range of catalysts have been used to synthesise NHI from technical parameters. The structure of the catalyst hydrogen (Hz) and nitrogen (I%).However, rutheni- gauze, its size and geometric design are now taken um (Ru) materials are now replacing them. The major drawback of Ru catalysts is H2 poisoning, as Hz into consideration when simulating an ammonia retards the dissociative adsorption of Nz, which is the oxidation reaction spreadmg over the whole SUT- rate determining step in NH3 synthesis. As cerium face. Technical characteristics of the ammonia oxide (CeOz) can stabilise noble metal dispersion and oxidation process, gauze composition and geomet- improve Hz poisoning, it has been used as a catalytic ric characteristics of the platinum alloy gauze are support to promote NZactivation or NH3 synthesis. also taken into account. Scientists from Osaka Municipal Technical As a result of this research, it may be expected Research Institute, Japan, have now used Ru and CeOz to prepare a catalyst which decomposes NH, that this new, simple, explosion-free technique for with high activity (K. Hashimoto and N. Toukai, 1. starting-up ammonia oxidation reactors to produce Morl Cuta! A: Cbem., 2000,161, (1-2), 171-178). The nimc acid, prussic acid and hydroxylamine sulfate catalyst consists of Ru-CeOz highly dispersed in Y- will find wide application in the near future. form zeolite (YZ). Ru-CeOJYZ works at conditions where YZ and CeOz are inactive. References The catalyst contained (in wt.Yo): 64.0 SOz, 19.5 1 W. Ostwald, British Patent 698; 1902 &03, 10.2 CeOz and 1.9 Ru. The decomposition 2 K. Kaiser, French Patent 419,782; 1909; A. R. Frank rate was fist order in NH3. The Ru particles and N. Caro, GmunPatent 303,824; 1914 loaded on Ce02/YZ reduce inhibition of the 3 V. Barelko and U. Volodin, Knet. CutuL, 1976, 4, decomposition rate by H1. (1% 683 IR‘ spectra for the catalyst showed that NH3 4 G. W. C. Kaye and T. H. Laby, ‘Tables of Physical decomposition at 300°C proceeded via formation and Chemical Constants and Some Mathematical of intermediate species, such as Ru-NH3, Functions”, 9th Edn., Longmans, Green & Co., Ru-NHz, Ru-N2 and Ru-H on the Ru surface. London, 1941 5 D. Frank-Kamenetsekiy,“DDiffusion and Heat Transfer Glass Conference in Veliky Novgorod in Chemical Kinetics”, Science, Moscow, 1967, p. 275 On 4th to 8th June 2001, the first international 6 V. Aaoshchenko and C. Kargin, “Technology of Nimc Acid”, Chemistry, Moscow, 1970, p. 496 conference on ‘Markets of Glass Fiber Materials, High-Quality Glasses, Monocrystals and Precious- 7 U. Volodin and V. Bareiko, ‘The Investigation of Non-stability Phenomenon in Oxidation Process of Metal Equipment for Their Production’ is to be HZand Hz + NH] Mixtures on Platinum Catalyst”, held in Vehky Novgorod, Russia. Other topics Preprint, Chemogolovka, Academy of Science of likely to be discussed include the science and tech- USSR, Chemical Physics Institute, 1979, p. 14 nology of glass and glass fibre, production and 8 V. Chemyshev and I. Kid, Phtinwm Metah Rev., applications, manufacture of silicate products and 1993, 37, (3), 136 the use of platinum metals equipment. The work- 9 S. Zjuzin, V. Barelko, V. Chemyshev eta!, hian Patent 1,476,677; 1995 ing languages will be Russian and English. Further information may be obtained from NPK 10 S. Zjuzin, V. Chemyshev, I. Gall et a!, Rmiun Patent 2,054,961; 1996 ‘Supermetal‘, Ozerkovskaya nab., d. 22/24, korp. 2, 11 S. Zjuzin, V. Barelko, V. Chernyshev et a!, him Moscow, 113184, Russia; Fax: +007 (095) 5334453; Patent 1,573,594; 1995 E-mail: [email protected].

PIatnum Metuh Rev., 2001, 45, (1) 40 ABSTRACTS of current literature on the platinum metals and their alloys PROPERTIES CHEMICAL COMPOUNDS A New Approach for Atomistic Modeling of A Novel N-Heterocyclic Carbene of Platinum(l1): Pd/Cu(llO) Surface Alloy Formation Synthesis in Ionic Liquids and Crystal Structure J. E. GARCES, G.H. BOZZOLO, P. ABEL and H. 0.MOSCA, AppL M. HASAN, I. V. KOZHEVNIKOV, M. R H. SIDDIQU1,A.SEINER Swj Sci, 2000,167, (1-2), 1S33 and N. WINTERTONJ. Ch.Rar. (S), 2000, (B), 392-393 The formation of PdjCu(ll0) surface alloys was ci.-(C~)(1-Ethyl-3-methy~dazol-2-ylidene)PtCl~ investigated using the Bozzolo-Ferrante-Smith was obtained by reacting a mixture of PtCL and PtCL method for alloys. A straightforward modelling with CZ& (50 am) in the basic @5mCl/AlCl3 approach was introduced, ranging from the deposi- (1:31) ionic liquid (@5-+ = 1-ethyl-3-methylim- tion of one smgle-Pd atom to the formation of dazolium) at 200°C. PtCh assists the reaction by Pd/Cu surface alloy. The approach gave information enhancing the formation of PtCt+=. on the exchange mechanism between adatoms and substrate atoms, the formation of Pd-Cu chains and Cationic Unsymmetrical 1,GDiazabutadiene the formation of Cu islands. Complexes of Platinum(l1) P.J. ALBIETZ, K YANG, R J. LA CHIC^ and R EISENBERG, Deuterium Solubility and Electrical Resistance of OrgunomckdkcJ, 2000,19, (18), 354>3555 Palladium-Rhodium Alloys Glyoxal-bis((2-~-topropylsilo~ethyl)-6-methyl- A. K M. FAZLE KIBRIA, ht.J. Hydrogen Enw,2000,25, (1 o), pheny1)diimine (TPS-6-MPD) (1) and glyoxal-bis((2- 997-1003 a-triisopropylsiloxymethyl)-4-methylphenyl)diimine Pd-5.0 and 10.0 at.% Rh alloys were investigated at (TIPS-4-MPD) (2) were reacted with frans- different temperatures by a gas phase method. A Pt(SMe&(Me)Cl to give (TIPS-6-MPD)Pt(Me)Cl (3) decrease in low pressure D solubilities and increase in and (TIPS-4-MPD)Pt(Me)Cl (4), respectively. plateau pressures with increasing Rh content were Cationic complexes [(N,N-chelate)Pt(Me)(L)]BF4 (L observed. The miscibility gap decreased with increas- = solvent/olefin; Nfl-chelate = (1) and (2)) were ing Rh content. Higher D solubility was attained for generated by reaction of (3) and (4) with AgBF4 in L. lower Rh content alloy at the maximum exerting pressure. The a,- resistance values gradually decreased Hydrogen Bonding in Transition Metal Complexes: with increasing Rh content and increased with Synthesis, Dynamics, and Reactivity of Platinum increasing temperature. Hydride Bifluoride Complexes N. A. JASIM and R N. PERUTZ,J Am. Cbtm. SOC.,2000,122, Preparation of Pd ClusterPolymer Composites (36), 8685-8693 Using Bis(acetylacetonato)paIladium(ll) Vapor tran~-pt(PR~)~H(FHq](R = Cy, 'Pi) (FHF = biflu- Y. NAKAO, chm. Lett. Jpn., 2000,o. 766767 oride) complexes (1) were synthesised by the reaction Pd cluster/polymer composites (1) were prepared of the corresponding trans-dihydride complex (2) with using bis(acetylacetonato)Pd(II)vapour. (1) with Pd NEty3(HF) in THF. (1) were also formed in C-F concentrations > 20% or in which the Pd clusters are activation reactions of (2) with CPG in the presence of locally distributed were achievable. Nylon 6 and [MeaF. The NMR and IR spectra show that the poly(ethy1ene terephthalate) were applicable to the bifluoride ligand (3) involves a H bond Pt-F-H-F. preparation of (1). Composites containing Pt clusters (3) is easily replaced by anionic ligands such as OTf- were also obtained using the Pt acetylacetonate. or neutral ligands such as PPh3 or py.

Low Temperature Specific Heat of CeRu2Si2at the The Preparation of the First Examples of Field Induced Metamagnetic Instability Sulfimide Complexes of Platinum; the X-Ray K. HEUSER, E.-W. SCHEIDT. T. SCHREINER, z. FISK and G. R Crystal Structure of [R(Ph2SNH),ICl2 STEWART, J. Lw.Tq. P&., 2000,118, (3/4), 235239 P. F. KELLY,A.C.MACKLIN,A.M. Z. SLAWIN andK W. WARING, Specific heat measurements are reported at 0.0620 Po&bedtun, 2000,19, (18-19), 2077-2081 K on CeRu2Siz in magnetic fields applied parallel to Solutions of PhzSNH (1) and ptClz(PMe~Ph)~] the c-direction around the critical field BM,where the exhibited an equilibrium between the starting materi- metamagnetic transition from the itinerant to the als and ~-~~CI(P~ZSNH)(PM~ZP~)Z]CI.The addition localised state takes place. In the critical field BM11 c = of pa]@W] gave ~-[P~C~(P~ZSNH)(PM~ZP~)Z]pF4]. 7.8 T a distinct deviation from the usual Fermi-liquid Four equiv. of (1) reacted with pPh&@'tCh] over a behaviour was found down to the lowest tempeia- week to give crystalline [Pt(PhzSNH)]Ch which has ture. Below 1.8 K C/T= (1 - uT),while for 1.8 K < square planar geometry with significant H-bonding T c 20 K a power law I"'-' with h = 0.66 was found. interactions between the cation and the chlorides.

l%tinrrm Metah b.,2001, 45, (I), 414 41 PHOTOCONVERSION APPARATUS AND TECHNIQUE Characterization by Resonance Raman Organoplatinum Crystals for Gas-Triggered Switches Spectroscopy of Sol-Gel TiOl Films Sensitized by M. ALBRECHT, M. LUTZ,A. L SPEKand G. VAN KOTEN, ivafnft?, 2000,406, (6799), 970-974 the Ru(PPh&(dcbipy)CI2 Complex for Solar Cells Non-porous crystalline materials consisting of Application [PtCl(NCN-OH)] (NCN-OH = C~HZ(CHZNM~~)~- P. FALARAS,A. HLJGOT-LEGOFF, M c.BERNARD and A. XAGAS, 2,6-0H-4) (1) undergo a controlled and fully Sol EnergV Mafm Sol. Ceh, 2000,64, (2), 167-1 84 reversible crystalline-state reaction with gaseous SO?. R~(F'Ph~)~(dcbipy)Cl~(1) (dcbipy = 2,2'-bipyridyl- (1) dramatically changes colour from colourless to 4,4'-dicarboxylate) was tested as a TiOz sensitiser in a deep orange due to the formation of the correspond- wet regenerative photoelectrochemical cell. Very ing adduct [PtCl(NCN-OH)(SOZ)]. Similarly, the intense Raman bands due to PPh, and dcbipy were reverse reaction in a SO2-free environment leads to observed for (1) on Ti02, when characterised by the complete regeneration of (1). (1) has potential for Raman spectroscopy.Altering the potential applied to gas storage devices and optoelectronic switches. the TiO, electrode for a given laser excitation energy can selectively enhance the PPh3vibrationalmodes. A A Fiber-optic Evanescent-Wave Hydrogen Gas reversible of dcbipy Raman lines was observed. shift Sensor Using Palladium-Supported Tungsten Oxide S. SEKIMOTO, H. NAICAGAWA, S. OKAZAKI, K. FUKUDA, Efficient Solar Water Splitting, Exemplified by s. ASAKUR~T.SHIGEMOIU and s. TAKAHASHI, Sm. Act~af~n RuOz-Catalyzed AIGaAsEi Photoelectrolysis B, Cbem., 2000,66, (1-3), 142-145 s. LICHT, B. WANG. s. MUKERJI, T. SOGA, M. UMENO and Pt or Pd supported on W03 were used as H2 sens- H. TRIBUTSCH,]. Pbs. Cbem. B, 2000,104, (38), 8920-8924 ing media in an optical-fibreH2 sensor (1). Two types A solar photovoltaic-electrolysis cell containing illu- of clad fibre were fabricated: (a) Pd/WO3 containing minated AlGaAs/Si RuOz/Ptbhc~evolves HZand 02 silicone resin as the clad and (b) a sol-gel Pt/WO3 or at a record soh-driven HzO electrolysis efficiency Pd/WO3 thin clad. In the presence of H2, strong (18.3% conversion). With the RUOZand Pbhk elec- evanescent-wave absorption was observed as a result trocatalysts, efficient electrolysis may be achievable by of W bronze formation. (1) formed from (b) gave using large areas of the electrolysis electrode, com- improved response time compared to (a). The prop- pared to the illuminated area. erties of (1) are controlled by the amount of catalyst. ELECTRODEPOSITIONAND SURFACE Lifetime-Based pH Sensor System Based on a COATINGS Polymer-Supported Ruthenium(l1) Complex Y. CLARKE,W. XU,J. N. DEMAS andB. A. DEGRAFF,b ch., Catalytic Activity of Sputtered Palladium Films for 2000,72, (1 5), 346~475 Electroless Nickel Plating Studied Using a Quartz A luminescence pH sensor system is based on Crystal Microbalance P~(Ph2phen)zDCbpy]~+dye (DCbpy = 4,4'-dicar- K. KOBAYAKAWA, M. MORITA, K. MIYAUCHI. Y. SATO and boxy-2,2-bipyridine)immobilised in a mixed domain E. FUJIMOTO, Pht. su$ Finish, 2000,87, (9),77-79 network copolymer utilising hydrophobic regions in a The catalytic activity of Pd film (1) sputtered on a hydrophilic, HzO-swellable, poly(ethy1ene oxide) quartz resonator was studied using a Ni plating bath (PEO) matrix. The Ru dye binds irreversibly to the and a quartz crystal microbalance. The adhesive inter- hydrophobic domains leaving pH-sensing COOH face between (1) and the quartz surface influenced groups projecting into a HzO-rich PEO region. The activiq. A Cr underlayer (2) suppressed the catalytic lifetime of the immobilised Ru dye has increased 3-4 activity of (l), but a Au underlayer (3) did not. (1) fold. The sensor provides a usable pH range of - 3-5. sputtered on (3) is usable as an active anode for mon- itoring electtoless plating. The catalytic activiq of (1) Sol-Gel lmmobilised Ruthenium(l1) Polypyridyl on (2) was enhanced by cathodic treatment in HC1. Complexes as Chemical Transducers for Optical pH Sensing Electrosynthesis and Characterisation of C. MALINS. H. G. GLEnR,T. E. KEYES, J. G. VOS. W. J. DRESSICK Nanostructured Palladium-Polypyrrole Composites and B. D. MacCRAITH, Sens. Actuators B, Chem., 2000,61, N. CIOFFI, L. TORSI,L. SABBATINI, P. G. ZAMBONIN and T. (1-2), 89-95 BIEW-ZACHEO,J. EhdCh., 2000,488, (l),4247 Protonable Rum polypyridyl complexes (1) have Electroactive Pd-polypyrrole composite thin films been evaluated for use as the chemical transducer were obtained using three different bottom-up proce- component in optical pH sensor devices. The immo- dures. The procedures all comprised electrochemical bilisation of (1) in a microporous sol-gel glass matrix synthesis of Pd moparticles which are subsequently resulted in a similar modulation of fluorescence emis- potentiostatically deposited or embedded into elec- sion with changing pH as is shown by (1) in solution. trochemically produced polypyrrole thin film. The The matrix provided a highly stable support that metallic Pd inclusions have a mean diameter of - 5 widened the working pH sensitive range to pH 3-9 nm with a homogeneous size dismbution. with only minimal sensitivity to 02.

P&n#m Metals Rev., 2001,45, (1) 42 HETEROGENEOUS CATALYSIS H 0 M0 GENE 0 US CATALYSIS Effects of the Radial Distribution of Platinum in New Highly Active Chiral Phosphapalladacycle Spherical Alumina Catalysts on the Oxidation of Catalysts. First Isolation and Characterization of a CO in Air Pd(lV) Intermediate A. DREWSEN, A LJUNGQVIST. M. SKOGLUNDH and J. M. BRUNEL, M.-H. HIRLEMANN, A. HEUMANN and c.BUONO, B. ANDERSSON, Cbem. Eng. Sci, 2000,55, (21), 49394951 Cbem. Commun., 2000, (19), 1869-1870 Pt/A1,0, catalysts with a shell (1) and a homoge- A new active P*-chiralphosphapalladacycle (1) was neous distribution (2) of Pt were prepared. Co- synthesised from the chid o-tolyldiazaphospholiidine impregnation of chloroplatinic acid (3) and citric acid ligand and Pd(0Ac)z in refluxing toluene. (1) was was used to prepare (2), resulting in a lower Pt dis- successfully used in the asymmetric hydroarylation of persion than the traditional impregnation method norbornene at 120°C in DMSO, with turnover num- with (3) which was used to prepare (1). Compared to bers 5 10". An intermediate PdO complex was (l), the conversion of CO started at lower tempera- fully characterised by X-ray structure analysis. tures when using (2), but higher temperatures were needed for total conversion. Wacker Reaction in Supercritical Carbon Dioxide H.JIANG,L.JIAandJ.L1,GreenChem,2000,2,(4),161-164 The Role of Pt/Si02 in the Catalytic Denitration by The Wacker reaction of alkenes such as oct-1-ene, HC02H of HNOa Concentrated Media styrene and cyclohexene was catded out smoothly in S. CUENAIS-LANGMIS, C. BOUYER, J.-C. BROUDICand B. COQ, sc-COz or ROH/sc-COZ (R = Me, Et). PdClz and AppL Cud. B:Envimn., 2000,27, (3). 199-204 CuClz were the catalysts with 02as oxidant. Both sc- Pt/SiOZ catalysts (1) are used together with COz and co-solvent affect the selectivity towards HC02H in chemical denitration to reduce nuclear methyl ketone and the presence of ROH accelerates fuel reprocessing waste. Two types of (1) were pre- the reaction. The presence of a small amount of Hz0 pared from H2PtC4, Pt(NH3)&12 and SiOz. (1) reduces the reaction rate although selectivity is suppress the induction period of the chemical deni- retained. It is suggested that the reaction is homoge- tration by the fast initial catalytic generation of HNOZ neous since Pd and substrates may form organo-Pd from HN03. These then become the active species in complexes in the oxidative process. the homogeneous phase. Leaching of Pt from (1) for large Pt aggregates (1 10 nm) is limited, but is very Novel Carbon-Carbon Bond Formation through significant for nanosized particles (1-2 nm). Mizoroki-Heck Type Reaction of Silanols and Organotin Compounds Solid-Solid Palladium-Catalysed Water Reduction K. HIRABAYASHI, J.-I. ANDO, J. KAWASHLMA, Y. NISHIHARA, with Zinc: Mechanisms of Hydrogen Generation A. MOW and T. HNAMA, BuU. Cbem. SOC.Jpn., 2000,73, (6), and Direct Hydrogen Transfer Reactions 1409-1417 s. MUKHOPADHYAY, c. ROTHENBERC, H. WIENER and Aryl- or alkenylsilanols and aryl-Sn compounds Y. SASSON, NmJ. Chem., 2000,24,(5), 305-308 react with various olefins in the presence of a stoi- HZgeneration from H20 occurred under moderate chiomemc amount of Pd(OAc)zor by a combination conditions in the presence of 1 equiv. of untreated of 0.1 molar amount of Pd(OAc)2 and CU(OAC)~/ Zn powder and 0.005 equiv. of 5% Pd/C. Pd-H and LiOAc (molar ratio 32) to give aryl- or akenyl-sub- Zn-0 interactions are important in this system. In the stituted olehns. Aryl-Sn compounds show reactivity presence of an organic H acceptor, such as benzalde- superior to silanols, although the Sn reagents some- hyde, direct H transfer from "Zn-activated" H20 to times induce undesirable homocoupling. Arylsilanols the substrate, without the participation of Pd-H inter- and aryl-Sn compounds react with Cz& to give mediates takes place. Hydrogenation of benzaldehyde styrene derivatives without formation of stilbenes. to benzyl alcohol, and of aromatic nitro compounds to the corresponding amines, was achieved. Palladium-Catalyzed C-C Coupling under Thermomorphic Conditions Heck Reaction Using Palladium Complexed to D.E. BERGBREITER, P. L. OSBURN, A. WILSON and E. M. SINK, Dendrimers on Silica J. h.Ch. SOC., 2000,122, (38), 905%906( H. ALPER, P. ARYA, s. c. BOURQUE, G. R. JEFFERSON and Poly(N-isopropylacrylamide) (€'NIPAM)-bound L. E. MANZER, Cun. J. Ckm., 2000,78, (6),920-924 phosphine ligands with a Pd(0) catalyst are shown to Pd-PPhZPAMAM-Si02 (PAMAM = polyamino- be efficient catalysts in Heck, Suzuki, and spsp' amido) (1) are hhly active catalysts for the Heck cross-coupling reactions under thermomorphic con- reaction of aryl bromides with styrene and butyl acry- ditions. Akstable tridentate s-C-S-Pdo catalysts late, affording para substituted stilbenes and bound to soluble polymer supports of PNIPAM or chamate esters in good yields. PAMAM den- poly(ethy1ene glycol) are also described. The use of a hers, on the surface of SiOz,were phosphonated thermomorphic solvent system in conjunction with using diphenyphosphinomethanol (prepared in J~H) the selectively soluble polymer support, allowed for and complexed to give (1). (1) can be recycled. facile product isolation and catalyst recyding.

Plarinum Metub Rev., 2001, 45, (1) 43 Rhodium-Catalyzed Copolymerization of PdGe-Based Ohmic Contact on n-GaAs with Norbornadienes and Norbornenes with Carbon Highly and Poorly Doped Layers Monoxide J.-W. LIM, J.-K MUN,s.-J. AN,s. NAM, M.-H. KWA~H. KIM and s.-w.ZHANG, T. KANEKO and s. TAKAHASHI,Mmmokmks, J.-J.LEE,]p.]. &I! P&., Pad 1,2000,39, (SA), 25462549 2000,33, (19). 69304936 The ohmic contact formation mechanism for a low Alternate copolymerisation of norbomadienes and contact resistance PdGe-based system on GaAs con- norbomenes with CO is catalysed by %(CO)I' taining highly and poorly doped layers annealed at under water gas shift reaction conditions selectively 38@450"C is reported. The lowest average specific to give the corresponding polyketones in high yields. contact resistance of the Pd/Ge/Ti/Pt ohmic con- A possible mechanism based on the structure of the tact was 2.4 X lo4 R cmz after annealing at 400°C. ohgomeric products is discussed. Investigation of the Electrical Properties of Practical Synthesis of (S)-l-(3-Trifluoromethyl- Tantalum-Ruthenium Dioxide as a Diffusion pheny1)ethanol via Ruthenium(l1)-Catalyzed Barrier for High Dielectric Capacitors Asymmetric Transfer Hydrogenation D.-S.YOON, s.-M. LEE and H. K. BAIK, J. Ekctrucbem. Soc, ZOOO, M MIYAGI, J. TAKEHAM, S. COLLET and K OKANO, %. hS 147, (9), 3477-3481 Res. Dw., 2000,4, (5), 346348 The effects of RuOz addition on the electrical prop- (.5-l-(3-Trifluoromethylphenyl)ethanol was pre- erties of the Ta-RuOz diffusion barriers of capacitor pared from the corresponding acetophenone by bottom electrodes as a function of the Ta:RuOz ratio Noyori's Ru(IQ-catalysed asymmetric transfer hydro- and contact size, at 65WOO"C in air, were studied. genation. This route gives high ee, low catalyst cost, For both the Ta + RuO2/n"-poly-SiSiOz/Si and the and safe operation. When set-alcohols were used as Pt/Ta + RuOz/n"-poly-SiSiO2/Si contact systems, a the H source, the catalyst was prepared in itti from conductive Ru02 crystalline phase was formed after [RuClz(arene)lZ and (lS,2J)-N-(arylsulfonyl)-l,2- anneahg. Surface oxidation of the diffusion barrier diphenylethylenediamine. With formic acid as the H was prevented and the bottom electrode structure source, the chid catalyst (S,J)-N-ptosyl-l,2-&- was retained at < 800°C. phenylethylene-l,2-diamine-Ruwas used. MEDICAL USES FUEL CELLS New Antitumor-Active Azole-Bridged Dinuclear Platinum-Tin Alloy Electrodes for Direct Methanol Platinum(ll) Complexes: Synthesis, Characterization, Fuel Cells Crystal Structures, and Cytotoxic Studies M.A. ABDEL RAHIM, M. W. KHALIL and H. B. HASSAN,]. &pL S. KOMEDA, M. LUTZ, A. L. SPEK, M.CHIKUMA mdJ.REEDIJK, Ekdmchem., 2000,30, (lo), 1151-1155 hog. Chem., 2000,39, (19), 423M236 Pt electrodes, modified by pdal galvanostatic or The antitumour properties of [{k-Pt(NH3)z}d,u- potentiostatic Sn electrodeposition, were used as OH)@-1,2,3-ta)]WO~]Z (I), [{Pt(R,R-dach)}@-OH)- anodes for the catalytic electrooxidationof MeOH in @-pz){Pt(S,S-dach) }]WO~]Z (2) and [{Pt(RR- acid medium. Cyclic voltammetry was used to study dach)} @-1,2,3-ta)2{Pt(S,S-dach)}] FJ03]2 (3) (1,2,3-ta MeOH electrooxidation. From the MeOH peak cur- = 1,2,3-mazolate, dach = 1,2-diaminocyclohexane, rent densities, Pt-Sn electrodes are claimed to be pz = pyrazolate) were tested after preparation. (1) superior to pure Pt electrodes. Sn also improved the and the parent compound [{~-P~(NH~)z}z@-OH)@- performance of anode stability over repeated cycles. p~)]wO3]~showed higher cytotoxicity than dsplatin, while (2) was shown to be moderatively active and (3) ELECTRICAL AND ELECTRONIC was only marginally cytotoxic. ENGINEERING Synthesis, Spectroscopic, Electrochemical and X-Ray Study of Co/Ni and Co/Pt/Ni/Pt Multilayers Antibacterial Studies of New Ru(ll) 1,lO- D. RAFAJA, J. VAC~NOVAand v. VALVODA, Thin Sokd Fib, 2000,374, (l),1620 Phenanthroline Complexes Containing Ultrathin Co/Ni magnetic multilayers, deposited by Aryldiazopentane-2,4-dione as Co-ligand dual electron beam evaporation, grow with poor L. MISHRA, A. K YADAW, S. SWASTAVA and A. B. PATEL., New. interface quality, which destroys the superlattice J. Chon..,2000,24,(7), 505-510 structure after a few bilayers. However, the quality of Mono- and dinuclear RuQQ complexes of 1,lO- the superlatticein Co/Pt/Ni/Pt magnetic multilayers phenanthroline containing aryldiazopentane-2,4- (1) was substantially better, mostly due to the lower diones as co-ligands were prepared. Complexes hav- mutual diffusion of Pt and Co, and Pt and Ni. For (I), ing 1,lO-phenanthroline as terminal ligand showed X-ray reflectivity measurements yielded information better bacterial inhibition than those bearing 2,2'- on thickness and interface roughness of individual bipyridine as terminal ligand. The 1,lO-phenanthro- layers. These were compared with thickness and line system already bound with DNA showed poorer interface roughness obtained from XRD. activity than the unbound system.

Ph'inzm Met& Rm, 2001,45, (1) 44 NEW PATENTS ELECTROCHEMISTRY APPARATUS AND TECHNIQUE Manufacturing Active-Hydrogen Water Tunable Optic Filter for Filtering light SUN ENG. KK J@anese AppL 2000/ 192,272 MCNC Wd&L 00/45,202 A method to manufacture active-hydrop (AH) A tunable optic filter (l), for filtering UV hght in HzO uses Pd or a Pd alloy as the cathode for HzO windows, comprises sets of alternating layers of electrolysis. Hz (as AH) is occluded into the cathode. dielectric material with different refractive indexes The cathode is then put into H20 containing an alka- separated by an intermediate layer (2), of PLZT, li electrolyte. This releases the AH in the Pd which PZT, BaTiO3, etc., the refractive index of which attaches to the alltali ions. The AH-alkali-ion HzO changes with the intensity of an applied electric field. obtained is stable and can be preserved for long peri- Two further electrically conductive layers: of ITO, ods by freezing. As the AH has hgh reactivity it may SnO,, Inz03, ZnO and RuOz, provide an electric field be used as a H source in liquid phase hydrogenation. across (2). (1) has faster reaction time, requires no motor-driven mechanism to tune it, and is adaptable Cathode for Electrolysis to different shapes without any energy increase. PERMELEC ELECTRODELTD. Gman&L 1/00/06,449 A cathode (1) for electrolysis of a H-containing Detection of Methyl Methacrylate material consists of a hist layer of Pd or Pd alloy (2) OPI PROD. INC. U.S.Patent 6,100,097 deposited on the reaction chamber side of a mem- Methyl methacrylate (1) is identified quickly from brane and a second layer of Pt black or Pt-Au porous other methacrylates in a liquid monomer by the for- catalyst deposited on (2). An electrolysis cell is divid- mation of a blue coloured methacrylate-Pd ed by (1) into a reaction chamber and an electrolysis molybdate complex after Pd molybdate is added to chamber, and is used for reduction or hydration of a the monomer, followed by other treatment. (1) is reactant in the reaction chamber. (1) also contains an detected in the liquid part of liquid/powder systems ion exchange membrane or a porous membrane. used for forming artificial nails.

Limiting-Current Type Oxygen Sensor ELECTRODEPOSITION AND SURFACE HITACHI CHEM. co. LTD. J@anueAppL 2000/146,904 COATINGS A limiting-current type 02sensor (1) comprises a Improving Performance of Electroplating Bath solid electrolyte adhered to an inner wall of a ceram- SPECIALTYCHEM. SYSTEMS mc. Wd&L 00/56,952 ic columnar body by heat resistant material. The The plating performance of aqueous sulfate (l), sul- surface is permeable to air. Electrodes are formed on fonic acid, fluoroborate and halide electroplating either side of the electrolyte. A Pt wire is iixed to the baths is improved by the addition of an alkyl and/or electrolyte. (1) is used in gas supply apparatus. It has alkanol sulfonic salt. (1) comprises: a source of sulfate excellent heat resistance, is dependable and can with- ions; soluble Rh, Ru, Sn, Ni, Cu, Cr, Cd, Fe, Zn, Pb stand heat shock It can also be mass produced. and/or In metal salts; and a salt of an alkyl and/or alkanol sulfonic acid. The additives give a wider range Filter for Removal of Tobacco Odour of useful current densities and improved appearance. KOBE STEEL LTD. Jqknese AppL 2000/210,373 A deodorant placed in a deodorising filter, for effi- Metal Component for Turbine Blade cient removal of tobacco odour, has a porous ISHIKAWAJIMA HARIMA HEAVY IND. support containing 0.1-10 wt.% Pd and C1 with J@anese&L 2000/178,763 Pd:Cl molar ratio 2 2.5. The deodorant can also effi- A metal component for a turbine blade used in a ciently remove chemical agents such as alkali and acid gas turbine engine of an aircraft, has an antioxidant and other odorous components. fdm (1) comprising an upper Al coating layer, an intermediate It layer and a lower Pt layer formed on Spin Valve Magnetoresistive Sensor the surface of a base material. (1) has improved RIDOWTO SMI KK J+nese&h. 2000/251,225-256 strength and oxidation resistant ability. A spin valve type magnetoresistive sensor (1) for a magnetic recording device, includes an antiferromag Electroless Rhodium Plating of Ceramics and Metals netic alloy layer containing either (ii at%): 45-55 Cr, ROBERT BOSCH G.m.b.H. Gman&L 1/99/09,678 2-10 Mn and remainder Pt; or (ii =Yo): 2.-10 Pd, A Rh plating bath comprises HzO and a readily 45-55 Mn, 2&35 Cr and remainder Pt. The alloy HzO-soluble Rh compound selected from ammoni- layer is heat treated at 250-300°C. (1) suppresses um RhUII) di@yridine-2,6-dicarboxylate), Rh amine rotation of the thin magnetic layer by the bias mag- complexes: RhClX(NH3)~,where x = 0-3, Rh acetate netic field of the magnetic head, hence improving the and Rh chloride methylenetetramine or diethylenem- thermal magnetic stability. A high magnetoresistive amine complexes. Rh precipitation is minimal, so variation rate and hgh linear response result in a high plating efficiencies of 2 90% can be obtained. recordtng density and a reliable magnetic head.

Platinrcm Metah h.,2001,45, (l), 45-48 45 HETEROGENEOUS CATALYSIS Removal of Methanol from Off-Gases Hydrogenation of Epoxidised Cyclohydrocarbons GENERAL ELECTRIC CO. WorklAppl. 00/47,309 MeOH impurities in off-gases generated during iso- UBE IND. LTD. Eumpean Appl. 1,018,498 Epoxidised 6C-12C cyclohydrocarbons are effi- propylbenzene oxidation are oxidised to CO, and ciently hydrogenated in a single-step process by HzO at low temperature by contacting the off-gases contacting the hydrocarbons with Hz at a pressure of with a Pt/zeolite catalyst. Granulated HZSM-5 zeo- 0.1-5.4 MPa and a temperature of 100-280°C in the lite is impregnated with HZPtCI, solution, followed by presence of Ru, Rh, Pd, Os, Ir and/or Pt catalysts drylng and calcining to decompose the acid to give supported on activated C, &03, SiOz, SiO2-AI2O3, 2 0.1% Pt content. The resulting discharge stream TiO,, zeolites and spinel. Total yields of cycloalka- contains MeOH at concentrations of I20 ppm. none and cycloallranol of I 93% were obtained. These are intermediates for the production of lac- Manufacture of Acetic Acid tams, lactones, etc., for use in synthetic resins and SHOWA DENKO KK WorMAppl.00/51,725 fibres. A catalyst for the manufacture of acetic acid by reacting ethylene and 0, in the gas phase, comprises Hydrodesulfurisation-Isomerisation Catalyst Pd metal, Au metal and heteropoly acids and/or their COSMO OIL CO. LTD. WorklAppl. 00/35,581 salts on a support. The Pd:Au weight ratio is A catalyst for simultaneous hydrodesulfurisation 1:O.l-5.0. The manufacture of the catalyst is daimed. and isomerisation of hght hydrocarbons comprises a Space-time yield, compared to prior art is high, and support of Zr oxide or Zr hydroxide and a sulfate selectivity to COZ is low. Catalyst deterioration is low radical, impregnated with (in massYo) either: 0.0510 while acetic acid production is high. Pd; 0.05-10 Pd and 0.0510 Pt; or 0.0510 Ni. After heat stabilisation at 550-800"C the specific surface Purification of Gas for High Purity Uses area is 50-150 mz g-'. Manufacture of the catalyst is AIR PROD. & CHEM. INC. US.Patent 6,093,379 also claimed. The catalyst has high activity, high S Purified gas is produced by removal of COZ, HzO, resistance, and reduced running costs. CO and Hz from a gas stream by adsorbing H20and COZ on a solid adsorbent, such as AlzO, or zeolite, Production of Alkylhydrogenohalosilanes and oxidising CO to COz over a Pt group metal cat- RHODIA CHIM. WorklA@L 00/39,132 alyst on a support which has zpc (zero point charge) Akylhydrogenohalosies (1) are produced by the of > 8.0. The COZformed is adsorbed, and any Hz is catalytic hydrogenation of alkylhalosilanes (2) using a chemisorbed on the catalyst, such as Pd/Al,O3. This bimetallic Ru-Sn catalyst. The process is especially method can purify air by removing CO and HZbefore useful for vaporising excess (2), especially MeSiCl3, or after cryogenic distillation for generation of NZ formed as byproduct during the Rochow-Miiller syn- and/or 0, for electronic and high purity applications. thesis (direct reaction of metallic Si with CHKI). This Enhanced efficiency, simple energy-efficient regener- reaction gives monomers used to produce silicone ation for continuous use and reduction of costs are resins. Under indusmal conditions in the presence of obtained. the Ru-Sn catalyst, (2) can be easily converted into (1) with a high degree of specificity. Fischer-Tropsch Synthesis ENERGY INT. COW. U.S. Potent 6,100,304 Steam Reforming Hydrocarbons Pd-promoted Co/y-Al,03 catalysts provide signifi- IMPERIAL CHEM. IND. PLC WorklAppl 00/43,121 cantly enhanced activity for Fischer-Tropsch A catalyst to steam reform hydrocarbons, such as synthesis in a continuous reaction system, particular- Ch, naphtha, LPG, etc., and to treat coal gasification ly in a slurry bubble column reactor. The catalyst gases comprises 0.1-2.5 wt% Ru and/or Ru oxide, contains (parts by weight): 10-65 Co and 0.257 Pd impregnated on a preformed porous carrier with per 100 of ')-AlzO, support. The catalyst is formed by oxides of Ni, La and Al. Hydrocarbon feedstock and total aqueous co-impregnation so that the Co and Pd steam are passed over the cylindrical catalyst heated form a dispersed catalytic phase and are in intimate at 6OCL850"C. Ru and/or Ru oxide improve resis- contact. The process is rate and cost efficient, has tance to C deposition and give high catalytic activity. higher selectivity, and is environmentally friendly. Catalyst for Vinyl Acetate Synthesis Treating Diesel Engine Exhaust Gases CELANESE CHEM. EURO. G.m.b.H. WOrklAPp,! 00/44,496 FORD GLOBAL TECHNOL. INC. U.S. Pafent 6,103,207 A catalyst for gas-phase production of vinyl acetate A catalyst for treating diesel engine exhaust gases from ethylene, acetic acid and 02, contains Pd, Cd contains a mixture of 25-65 wt.% particles of a Mn and/or their compounds and alkali metal(s) on a and Zr bimetallic oxide and a supported Pt group moulded porous support. The support is based on metal, for example 0.25 wt.% Pt/AlzO,. The atomic pyrogenic SiO, and contains Mg. It has a hollow ratio of Mn:Zr is 31-1:3. The catalyst reduces NOx cylindrical configuration with facet edges. Activity in an oxidising atmosphere during diesel engine oper- and selectivity are increased by using this support, ation. A wider NOx conversion window in the low which gives a totaUy impregnated or shell catalyst. temperature region is obtained.

PhhmMetoh Rev., 2001,45, (1) 46 Manufacture of Polyalkylene Glycol 1-Alkenyl Ethers Production of Aldehydes SHOWA DENKO K.K. J@anese&l 2000/143,567 MITSUBISHI CHEM. cow. J@neseAppr! 2000/159,719 Highly pure polyallsylene glycol 1-alkenyl ethers are An aldehyde is produced by reacting an olefinic manufactured at a high selection rate and in lugh yield compound, such as propylene or 1-butene, with Hz by inhibiting the formation of byproduct. The reac- and CO in a solution containing a Rh complex cata- tion comprises isomerisation at 30-200°C of a lyst which has an organophosphite ligand, such as polyalkylene glycol 2-alkenyl ether using at least one diphenyl(2,4-ditertiary butylphenyl)phosphite, at type of a catalyst carrying 0.05-10 wt.% of a noble 15-150°C and ressures of atmospheric to 200 kg metal(s), such as Pd/carrier. The product ethers are ad.Ni (1-10 F ppm) is added to the solution to useful as resin materials and reaction diluents. reduce catalyst decomposition and inhibit deactivation, so that the catalyst can be circulated and reused. Production of High Purity Sugar Alcohols ROQUElTE FRERES SA. Fmcb APpA 2,789,683 Biphenyl Tetracarboxylic Acid Ester Production of sugar alcohols comprises hydro- UBE IND. LTD. Jqaneseml. 2000/186,063 genating the corresponding sugar in a series of Manufacture of 3,3’,4,4’-biphenyl tetracarboxylic trickle-flow reactors comprising a first reactor con- acid ester involves the dimerisation of o-phthalic acid taining a fixed bed of a Ru catalyst and a second diester in the presence of sequentially added catalyst reactor containing a fixed bed of a promoted Ru cat- (ppwdered Pd salt of specific surface area 2 0.5 m2 alyst The process can convert D-glUCOSe into high g- ) and a basic bidentate ligand. The adherence of Pd purity sorbitol ( 2 98.5% for sorbitol) at hgh conver- metal precipitate to the reaction vessel is inhibited. sions (2 99.85%) and with lugh selectivities (2 99./0). Preparation of Benzoic Amides Epoxidised Olefin Production CENTRAL GLASS co. LTD. /@me AppA 2000/191,612 BAYER A.G. GmanA@L 1/98/57,137 Benzoic amides (1) are prepared in a single step by Epoxidised olefins (1) are produced by reacting reacting aromatic compounds, Ar-X (Ar = optionally olefins with H202 solution in the presence of a syr- substituted aromatic group, X = halogen, trifluo- thetic Ti-containing zeolite, followed by separation of romethanesdfonate, 14alkylsulfonate, etc.), CO (1) and recycling the H202 solution. The HZ02 solu- and NH3 in the presence of a catalyst of Pd and phos- tion, which is dilute alcoholic or aqueous-alcoholic, phines. Benzoic acid is produced which is separated optionally contains a stabdiser and is prepared by from the reaction system. The recovered Pd-phos- continuous reaction of H2 and 02on a Group WI phine complex is then used as a catalyst. (1) are useful metal catalyst The process gives high selectivities (> intermediates for pharmaceuticals and agrochemicals. 85% for propylene oxide) despite using the dilute HZ02 solution directly, without any intermediate Production of Alkyl3-Alkenoates purification. BASF A.G. Geman Appr 1/99/04,200 Akyl3-alkenoates are produced by adding formates to dienes in the presence of CO (at a partial pressure HOMOGENEOUS CATALYSIS 2 1 MPa) and a catalyst containing a Pd compound Production of Oligocarbonates and metal chloride(s) MCl, (M is an alkaline earth BAYER A.G. European AppA 1,013,634 metal when n = 2, or a metal ion of sub-Group lV Oligocarbonates are produced by reacting an am- when n = 4, or a metal ion of sub-Group VI when n matic dihydroxy compound with CO and O2in the = 3, 5 or 6). Organic base containing P or N is not presence of a Pt metal catalyst, a cocatalyst, a base, an present. The process is more selective and operates at inert organic solvent and, optionally, a quaternary lower pressures than existing processes. It can be car- salt. The solvent forms an azeotrope with the HzO ried out without solvent or with the educts as solvent, byproduct and is removed from the reaction mixture. so HC1 acid need not be added. The catalytic system has increased activity. The oligocarbonates have low residual H20 content. FUEL CELLS Preparation of Mono- and Di-arylphosphines Electrode Structure for Fuel Cells CYTEC TECHNOLOGY cow. WdAppl 00/32,613 JOHNSON MATIHEY PLC WdAppl.00/35,037 Mono- (1) and di-arylphosphines (2) are prepared A piston-tolerant anode structure, for use in mem- by reacting an aryl compound with phosphine in the brane electrode assemblies and PEMFCs, has two presence of a Group VIII metal catalyst, for example, catalytic components. The fust is Pt-Y, where Y is a an adduct of a Pdo compound and a aiaiyl phos- bronze forming element, (Ti, V, Nb, Ta, etc.) with an phine. The aryl compound has a leaving group optional third metal X (X = Ru, Rh, Ti, Cr, Mn, Fe, attached to a C atom of the aromatic ring. The Co, Ni, Cu, Ga, Zr, Hf or Sn, especially Ru, Rh, Mn, process avoids or alleviates corrosion and can be Co and Ni). The second catalyst is Pt-M (M = one of carried out on a large scale. (1) and (2) are obtained the above metals, especially Ru or Rh). The anode has in good yield along with relatively small amounts of improved tolerance to CO and CO2 poisons while tertiary phosphine. maintaining lugh activity.

Platinxm Metah Rev., 2001, 45, (1) 47 Catalyst Ink and MEAs for Fuel Cells Horizontal Magnetic Recording Medium CALIFORNIA INST. OF TECHNOLOGY INT. BUSINESS MACHINES COW. U.S. Patent 6,086,974 WorMApl.00/45,448 A horizontal magnetic recording medium (1) has a A catalyst ink for DMFCs comprises catalytic mate- magnetic layer of granular film with grains of chemi- rial, such as Pt or Pt and Ru, and poly(vinylidene cally ordered FePt or FePtX alloy (or Copt or CoPtX) fluoride). The catalyst ink improves interfacial bond- (X = Cr, Cu, Ag, Ta, etc.). It also has an etched seed ing characteristics between deposited electrocatalytic layer of nonmagnetic Pt, Pd, Cr, CrV, etc., on a sub- layers and the proton conducting moieties of MEA strate. The magnetic properties are controlled by structures. Electrical performance is improved and pinsize and distribution, degree of chemical order- impedance reduced. MeOH crossover in a fuel cell mg, and the nonmagnetic materials. (1) has low-noise, stack is reduced. high density and the high magnetic stability.

Fuel Cell Catalyst for PAFC and DMFC Ferroelectric-Based Capacitor SYMYX TECHNOLOGIES INC. WorMaAppA 00/54,346 RADIANT TECHNOLOGIES INC. US.Patent 6,117,688 A ternary Pt-Ru-Pd catalyst for use in electrochem- A ferroelectric-basedcapacitor used in memory sys- ical reactor devices, especially as fuel cell electrodes, tems has: a bottom electrode consisting of a Pt layer comprises (ii at.%): 20-60 Pt, 20-60 Ru and -5 in contact with a layer of ohmic materid, a dielectric Pd. The atomic ratio of Pt:Ru is 0.61.8. The fuel of Pb-Zr titanate doped with an element having an cells, for instance PAFCs or DMFCs, electrochemi- oxidation state > +4; and a top electrode consisting cally convert a hydrocarbon-based fuel and 02to of a second ohmic material layer in contact with a H20, COZ and electricity. The catalysts give second Pt layer. The capacitor exhibits low fatigue, improved fuel cell efficiency while allowing a low imprint and is used in memory systems. decrease in the size of the cell and the costs. Production of Printed Circuit Hydrogen Refiner for Fuel Batteries SHINETSU CHEM. IND.CO. LTD. MATSUSHITA DENKI SANGYO KK Japanese &pl. 2000/138,442 Jqanese Appr 2000/178,007 Cicuit board is produced by forming a thin film of A Hz refiner which produces Hf as a fuel for fuel a polysilane (l),containing a C functional she,on a batteries, comprises a feedzone for a modified gas substrate and contacting it with a Pd salt to form a and a reaction chamber downstream of the feedzone. colloidal Pd layer. A photosensitive resin layer is The reaction chamber contains a catalyst which placed on (1) and is then selectively irradiated with removes CO from the gas. The CO transforming cat- light to form a patterned groove. An electroless plat- alyst is Pt, Ru, Rh and/or Pd. The gas may also ing solution is applied to form a conductive metal contain HZ and HzO. The refiner has a shorter start- layer in the groove. The circuit substrate has superior up time and problems caused by 02are prevented. heat resistance and fineness of pattern. The refiner operates stably for longer times. Semiconductor Devices such as FRAM FUJITSU LTD. Japanese Appl. 2000/156,471 ELECTRICAL AND ELECTRONIC A reliable semiconductor device, such as FRAM, ENGINEERING with good fatigue resistant characteristics contains an Conductive Barrier Layers in Electronic Capacitors electrode which carries a metal oxide (Pt,Ir, Ru, Ni, SHARF’ KK Eumpean Appr. 1,035,588-89 Ti, Zr and Ce) film on which a metal film is formed. A temperature stable conductive barrier layer, for A ferroelectricfilm (1) is formed on the electrode and IC ferroelectric capacitors used in PRAMS, compris- on this is formed an electrode containing a per- es a first barrier layer containing Ta on a substrate, ovskite. By repeated polarisation inversion, 0 with a film of Ir or Ir-Ta-0. The film of Ir-Ta-0 vacancies in (1) are supplemented by 0 from the per- remains conductive’after anneahg at high tempera- ovskite film. Capacitors which operate at low voltage ture in an 02 ambient atmosphere. Adhesion, can use the material. conductance, hillock and peeling problems are &- imised, as the Ir does not interact with the substrate. Circuit Electrode of laminate Structure OCEAN K.K. Jqanese AppL 2000/160,348 Integrated Circuits A laminated electrode structure for use on a print- SYMETRM COW. Wo&&L 00/49,660 ed circuit board has a Pd corrosion-resistant film An integrated circuit for non-ferroelectric or ferro- over a Ni plated film formed on the circuit pattern of electric devices with hgh dielectric constant has a the substrate. A Au film is formed on the Pd film SIX- diffusion barrier layer of Ir oxide which is located face. Contact adherence strength between each film between a thin hLn of layered superlamcematerial (1) layer in the laminate is improved as is surface htness. and a local interconnect. The Ir oxide inhibits diffu- Bonding and ball shear strength are also increased. sion of chemical species from the local interconnect to (1) and is thus effective for preventing diffusion of The New Patents abstracts have been prepared from metals, Si, and other chemical species. material published by Derwent Information Limited.

Phtinum Metah Rm, 2001,45, (1) 48