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Platinum Metals Rev., 2000, 44, (1), 40

Abstracts of current literature on the platinum metals and their alloys

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PROPERTIES

Grain Growth in Ultrathin Films of CoPt and FePt

r. a. ristac, k. barmak, k. r. coffey and j. k. howard, J. Mater. Res ., 1999, 14, (8), 3263-3270

Thin films (10 nm) of CoPt and FePt sputter deposited on oxidised Si wafers have been characterised using TEM. A rapid growth stage concurrent with the formation of a [111] fibre texture was observed to occur within 5–10 minutes of annealing, followed by a much slower growth stage after the fibre texturing was well advanced. Differences in grain growth rate and ultimate grain size were observed to be dependent on heating rate.

The Effect of Platinum Additions on the Oxidation of Directionally-Solidified Ni-Cr-AI-Y-Cr3C2 Alloys at 1,100 and 1,200°C

f. h. stott, b. gleeson and p. castello, Mater. High Temp ., 1999, 16, (1), 15-26

The effects of 2 wt.% Pt additions on the oxidation of the title alloys were investigated under isothermal and thermal cycling conditions. At 1100°C, the addition of Pt favoured the formation of a continuous Al2O3 scale over primary carbides intersecting the alloy surface. The scale remained substantially adherent after isothermal oxidation, but lifted and cracked on thermal cycling. At 1200°C, an external Al2O3 scale formed initially, but spalled extensively after short times under both isothermal and thermal cycling conditions.

Novel Hydrogen Sensors Using Evanescent Microwave Probes

m. tabid-azar and b. sutapun, Rev. Sci. Iustrum ., 1999, 70, (9), 3707-3713

Evanescent microwave probes (EMP) were used to detect deflections in a Pd-coated cantilever and to quantify the amount of stress and the resistivity change in the Pd film as a function of H2 concentration. The stress was 5.26-8.59 x 10 Pa for 0.5-1.4% H2 concentration at room temperature, which is about 3 times larger than that found in bulk Pd for the same H2 concentrations. The resistivity of the Pd films changed by 13.5% at 3.0% H2 giving 18% change in the EMP signal. H2 concentrations of 0.01-4% could be detected by the EMP.

Magnetic Properties of RPd3S4 (R = Ce, Gd)

m. wakeshima and v. hinatsu, J. Solid State Chem ., 1999, 146, (1), 226-229

GdPd3S4 shows antiferromagnetic behaviour below 5.8 K. Above 10 K, the magnetic susceptibility follows the Curie law, and the effective magnetic moment is 7.36 μB. CePd3S4 shows ferromagnetism below 5.8 K. The residual magnetisation is 0.39 μB and the magnetic moment at 5 T is 0.83 μB at 2 K. From the magnetic transition temperature of RPd3S4, the superexchange interaction is thought to be dominant in the magnetic interaction.

Alloying Elements Partitioning in TiAI-Ru Intermetallic Alloys

s. kim, d.j. larson and g. d. w. smith, Intermetallics, 1999, 7, (11), 1283-1290

The solute partitioning behaviour in two phase α2 + γ Ti-48 at.% Al-0.5 at.% Ru alloys was investigated using atom-probe field-ion microscopy. Ru was depleted in α2 and interstitial elements were localised in the α2 phase. The degree of localisation for interstitials is much more significant than for substitutional elements.

Infrared Spectra and Density Functional Calculations of RuCO+ OsCO+ Ru(CO)x Os(CO)x Ru(CO)x- and Os(CO)x- (x = 1-4) in Solid Neon

m. zhou and l. andrews, J. Phys. Chem. A, 1999, 103, (35), 6956-6968

Laser ablated Ru and Os atoms were co-deposited with CO (0.05–0.2%) during condensation in excess Ne.M(CO)x (M = Os, Ru; x = 1-5) were formed during deposition or on annealing, while M(CO)x (x = 1–4) were formed by electron capture. MCO+ were produced by metal cation reactions. IR characterisations were recorded. Density functional calculations predicted these frequencies within 1% and the isotopic shifts for different C-O stretching modes within averages of 1–2 cm-1.

CHEMICAL COMPOUNDS

Luminescence and Aggregation Studies of Hexanuclear Platinum-Copper Acetylide Complexes. Crystal Structure of the Luminescent Metal-Metal Bonded Dimer [Pt2Cu4(C≡CPh)8]2

v. w.-w. yam, k.-i. yu and k.-k. cueung, J. Chem. Soi., Dalton Trans ., 1999, (17), 2913-2915

[Pt2Cu4(C≡CPh)8]2 (1) was synthesised by the reaction of [NBu4]2[Pt(C≡CPh)4] (2) with [Cu(MeCN)4][PF6] in acetone. (1) was shown to exist in the dimeric form only in concentrated solution through a Pt-Pt bonding interaction. The shift in the v(C≡C) absorption to a lower wavenumber in (1) than in (2) was indicative of a π-bonding mode of the alkynyl ligands.

Palladium and Platinum Dithiocarbamato Complexes Containing Mono- and Diamines

v. scarcia, a. furlani, d. fregona, g. faraglia and s. sitran, Polyhedron, 1999, 18, (22), 2827-2837

[M(DMDT)X]n (M = Pd, Pt; DMDT = Me2NCS2-; X = CI, Br) were reacted with amines (Am) (Py, pyridine; Pra, n -propylamine; Cba, cyclobutylamine; Dap, 1,3-diaminopropane; En, ethylenediamine) to give M(DMDT)(L)X (L = Py, Pra, Cba), [MpMDT)(L2)]X, [M(DMDT)(En)]X and [M(DMDT)(Dap)]X. TGA data suggest a particular behaviour for Pd-Pra and Pd-Cba, with the formation of low stoichiometry intermediates Pd2(DMDT)2AmX2.

Design of Novel Hexametallic Cartwheel Molecules from Persubstituted Benzene Compounds

h. p. dijkstra, p. steenwinkel, d. m. grove, m. lutz, a. l. spek and g. van koten, Angew. Chem. Int. Ed ., 1999, 38, (15), 2186-2188

Nanosized hexametallic PdII species with persubstituted benzenes C6[3,5-(CH2Y)2C6H3]6 (Y = NMe2, P(O)Ph2, PPh2, SPh) were synthesised. The molecular structure of [C6{3,5-(CH2SPh)2C6H2(PdCl)}6] showed C3 symmetry with adjacent radial Pd-Pd separations of 7.339(2) and 8.006(2) Å and a diametrically opposed Pd-Pd separation of 15.340(2) Å. These cartwheel structures are potential homogeneous catalysts which can be recovered by nanomembrane filtration techniques.

Dicarbonylcyclopentadienyliridium,(η-C5H5)lr(CO)2, as a Ligand

f. jiang, k. biradha, w. k. leong, r. k. pomkroy and m. j. zaworotko, Can. J. Chem ., 1999, 77, (8), 1327-1335

Using CpIr(CO)2 as a 2e donor ligand, the metal complexes Cp(OC)2IrW(CO)5 (1), Cp(OC)2IrRu(CO)3(SiCl3)2, Cp(OC)2IrOs(CO)3(GeCl3)(Cl) (2) and Cp(OC)2IrOs(CO)3(X)2 (X = CI, Br (3), I) were prepared and characterised. The crystal structures of (1), (2) and (3) all contain an unbridged metal-metal bond. With the exception of (2), all the complexes dissociate in solution at room temperature, some of them rapidly. CpIr(CO)2 is a weak ligand, comparable in ligating ability to Os(CO)5.

Synthesis and Characterization of a Metal Coordination Polymer Consisting of Ruthenium(III) β-Diketone Units Linked by Butadiyne Bridges

y. hoshino and y. hagihara, Inorg. Cbim. Acta, 1999, 292, (1), 64-72

[Ru(mESima)3] (mESima- = 3-(trimethylsilyl)ethenyl-2,4-pentanedionate) and [Ru(mEma)3] (mEma- = 3-ethynyl-2,4-pentanedionate), were prepared as precursors for polymerisation to give the title Ru(III) polymer (1). The number-average molecular weight of (1), 5400, corresponding to ∼ 11 monomer units, was obtained from the FT-NMR integrated intensities for the protons on the ethynyl group of the mEma ligand end-group relative to the CH3-protons of the entire chain. NMR showed that (1) has a chain-like structure.

ELECTROCHEMISTRY

Nickel Electrowinning Using a Pt Catalysed Hydrogen-Diffusion Anode. Part II: Batch Tank with a Sulphate Bath

j. rambla, e. brillas and j. casado, J. Appi. Electrochem ., 1999, 29, (10), 1211-1216

A Pt catalysed H2-diffusion anode was used for Ni electrowinning from a NiSO4 bath with a stainless steel/Ni cathode. The anode comprised a C cloth coated with ∼ 5 mg cm-2 of C black + PTFE with 10 wt.% Pt. For Ni2+ contents of 50-125 g l-1, current efficiencies > 93% were found. Energy costs increased linearly as current density increased from 10–50 mA cm-2, but at values much lower than those from a conventional Pb anode.

Development of Carbon-Metal Oxide Supercapacitors from Sol-Gel Derived Carbon-Ruthenium Xerogels

c. lin, j. a. ritter and b. n. popov, J. Electrochem. Soc, 1999, 146, (9), 3155-3160

Sol-gel high surface area C-Ru xerogel composites (1) were prepared from carbonised resorcinol-formaldehyde resins containing RuO2. x H2O. A very high specific capacitance of 256 F g-1 (single electrode) was obtained from (1) with 14 wt.% Ru, which corresponds to > 50% utilisation of the Ru. (1) also showed no change in electrochemical capacitance after 2000 charge/discharge cycles, indicating that (1) was very stable and the redox reactions associated with the RuO2 were completely reversible.

PHOTOCONVERSION

Hydrogen Evolution Photoinduced by Using Platinum-Loaded Langmuir-Blodgett Films of Viologen-Linked Porphyrin

h.hosono, J. Photochem. Photobiol. A: Chem ., 1999, 126, (1-3), 91-97

Viologen-linked porphyrin (1) and viologen-free porphyrin (2) were synthesised and their Pt-loaded Langmuir-Blodgett (LB) films (3) prepared. Steady photoinduced H2 evolution was observed using (3) under steady-state irradiation in the presence of EDTA as a sacrificial electron donor. The rate of H2 production using (1) was larger than for (2). H2 evolution continued for longer using (1). In LB film with (1), the degradation via the reduced form of porphyrin is repressed.

Photoluminescence of Trimeric Palladium(II) Acetate in Solution

h. kunkely and a. vogler, Chem. Phys. Lett ., 1999, 308, (3, 4), 169-172

Pd3(acetate)6 (1) shows photoluminescence in benzene at λmax = 475 nm (fluorescence) and 595 nm (phosphorescence). The longer wavelength emission is quenched in the presence of air while the shorter wavelength luminescence is hardly affected by O2. The emission of (1) is related to its trimeric structure and disappears when K(acetate) is added. The luminescence originates from the dσ* → pσ excited state, involving metal-metal interaction in the triangular (PdII)3 moiety.

Iridium(III) Bis-terpyridine Complexes Displaying Long-Lived pH Sensitive Luminescence

m. licini and j. a. g. williams, Chem. Commun ., 1999, (19), 1943-1944

The title Ir(III) complexes in which the terpyridine ligands bear pendent protonatable (pyridyl) (1) or deprotonatable (phenolic) (2) groups have been prepared. Complexes with (1) display long-lived emission at pH 7 in air-equilibrated aqueous solution, but both the lifetime and intensity are reduced by a factor of > 8 upon protonation of the pyridyl nitrogen; the structurally similar complexes with (2) are only weakly emissive and their ground-state absorption spectra exhibit a new, low energy band (λ = 468 nm) upon deprotonation. These complexes constitute potential new pH sensory systems.

Luminescent Nation Membranes Dyed with Ruthenium(II) Complexes as Sensing Materials for Dissolved Oxygen

d. garcÍa-fresnadillo, m. d. marazuela, m. c. moreno-bondi and g. orellana, Langmuir, 1999, 15, (19), 6451-6459

Indicator layers for luminescence optosensing of O2, showing no dye leaching and avoiding the use of adsorbing materials, were developed by using [RuL3]2+ complexes (L = 2,2’-bipyridine, 1,10-phenanthroline, 5-octadecanamide-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline (dip)) immobilised in Nafion. The O2 sensitivity of [Ru(dip)3]2+ dipped in MeOH was independent of the Ru(II) loading and Nafion counterion. Highly O2-sensitive luminescent membrane, for monitoring in organic solvents, H2O and the gas phase, was prepared on immobilising [Ru(dip)3]2+ in 178 μm thick Nafion.

ELECTRODEPOSITION AND SURFACE COATINGS

Excimer Lamp-Induced Decomposition of Platinum Acetylacetonate Films for Electroless Copper Plating

j.-y. zhang and i. w. boyd, Solid State Electron ., 1999, 43, (6), 1107-1111

Photo-induced decomposition of Pt acetylacetonate films (1) was achieved using an excimer VUV source of 172 nm radiation. VUV irradiation of non-catalytic substrates coated with (1) formed Pt metal, which is an activator for an electroless Cu plating process. The photodecomposition rate of Pt acetylacetonate was found to be strongly dependent upon the UV dose, the chamber pressure during irradiation and exposure time.

X-Ray Photoelectron Spectroscopy Study of Pt-Oxide Thin Films Deposited by Reactive Sputtering Using (VAr Gas Mixtures

m.-c. jung, h.-d. kim, m. han, w. jo and d. c. kim, Jpn. J. Appi. Phys ., 1999, 38, (8), 4872-4875

Pt-oxide thin films (1) were obtained by reactive r.f. magnetron sputtering of Pt at a relatively high partial pressure of O2. XRD indicated that (1) have an amorphous structure. From XPS, it was found that chemical shifts of the Pt 4f peaks occur, and the amount of energy shifts are 1.0 and 2.1 eV. After comparison with known data, it was concluded that (1) are composed of PtO grains and intermediate mixtures of PtO and PtO2.

Electroless Plating of Metals onto Carbon Nanotubes Activated by a Single-Step Activation Method

i.-m. ang, t. s. a. hor, g.-q. xu, c.-h. tung, s. zhao and j. l. s. wang, Chem. Mater ., 1999, 11, (8), 2115-2118

Oxidised C nanotubes were activated with Pd-Sn catalytic nuclei. A HCl accelerator was used to preferentially dissolve the protective layer, exposing more surface area of the Pd-Sn nuclei. These activated nanotubes were used as precursors for Ni- and Pd-coated nanotubes via electroless plating. Metal deposition occurs at the catalytic sites. The deposited clusters of metal atoms then catalyse further metal deposition on the tube surface.

Effect of the Deposition Temperature on the Properties of Iridium Thin Films Grown by Means of Pulsed Laser Deposition

m. a. el khakani, b. le drogoff and m. chaker, J. Mater. Res ., 1999, 14, (8), 3241-3246

Pulsed laser deposited Ir thin films (1) were obtained by ablating an Ir target with a KrF excimer laser. At the deposition temperatures of 20–600°C, (1) are polycrystalline with a preferred (111) orientation, especially at 200–500”C. The average grain size of (1) continuously increased from ∼ 10 to 30 nm and the stress changed drastically from highly compressive to tensile, as the deposition temperature was raised. The room temperature resistivity of (1) gradually decreases in the range 20–400°C and stabilises for higher temperatures. (1) with the lowest resistivity and a nearly zero stress level can be grown at 400°C.

APPARATUS AND TECHNIQUE

The Use of Polymers Coupled with Metallised Electrodes to Allow H2O2 Detection in the Presence of Electrochemical Interferences

d.j. daly, c. k. o’sullivan and g. g. guilbault, Talanta, 1999, 49, (3), 667-678

The co-deposition of Ru, Rh and Pt as well as Pt on Ru-Rh electrodes was investigated to provide an electrode surface which is highly catalytic and selective towards H2O2. All transducers were coupled with polymers for enhanced response, due to elimination of interferences. A Ru-Rh metallised electrode polymerised with poly(1,3-diaminobenzene) gave the best results. At an applied potential of +100 mV the response to H2O2 was 200 times larger than the response of any interferences.

An Electrochemical Alcohol Sensor Based on a Co-electrodeposited Pt ∣ WO3 Electrode

y. chen, k. y. chen and a. c. c. tseung, J. Eledroanal. Chem ., 1999, 471, (2), 151-155

A Pt∣WO3 electrode (1) was used for the rapid determination of EtOH in beer and wine. (1) was prepared by co-electrodeposition from a solution containing chloroplatinic acid and W onto a Au substrate of 0.5 cm2 at −0.25 V for 30 min. The W solution was prepared by dissolving W powders in H2O2 followed by decomposing the excess H2O2 with a Pt foil coated with Pt black.

Electropolymerised Platinum Porphyrin Polymers for Dissolved Oxygen Sensing

a. s. holmes-smith, a. hamill, m. cambpell and m. uttamlal, Analyst, 1999, 124, (10), 1463-1466

Sensitivities of poly-Pt tetraphenylporphyrin (1) and poly-Pt octaethylporphyrin (2) to dissolved O2, given by Stern-Volmer quenching coefficients, were obtained from luminescence lifetime measurements as 1.12 (mg 1-1)-1 and 2.07 (mg 1-1)-1, respectively. The response time for (2), determined from luminescence intensity measurements, to a step change in O2 concentration of 4.3–38.6 mg 1-1 was 8 ms. The limit of detection obtained for an O2 sensor based on (2) was 0.06 mg 1-1.

Fabrication of Defect-Free Pd/α-Al2O3 Composite Membranes for Hydrogen Separation

a. li, w. liang and r. hughes, Thin Solid Films, 1999, 350, (1, 2), 106-112

A thin film Pd/α-Al2O3 composite membrane (1), where Pd thickness is 10.3 μm, was fabricated by electroless plating combined with osmosis. The H2 permeation performance of (1) was investigated using pure H2 at various temperatures from 320-577°C. H2 effects on the surface of (1) had an influence on H2 permeation, so that the H2 permeation performance diverged slightly from Sievert’s law. The apparent activation energy for (1) was 12.3 kJ mol-1 at 320-577°C. Both a sweep gas of N2 and a higher total feed flow rate improved H2 permeation through (1).

Composition Control and Hydrogen Permeation Characteristics of Sputter Deposited Palladium-Silver Membranes

b. mccool, g. xomeritakis and y. s. lin, J. Membrane Sci ., 1999, 161, (1-2), 67-76

Submicron thick continuous Pd-Ag films (1) were deposited by sputtering on mesoporous γ-Al2O3 from a target composed of 75% Pd and 25% Ag. (1) were tested in a multigas permeation system for H2 permeance and H2 selectivity over He. H2 permeance for (1) was found to be 3 x 10-8 to 1 x 10-7 mol m-2s-1 Pa and H2:He selectivities were in the range 4-4000, depending mainly on the Ag concentration and microstructure of (1).

HETEROGENEOUS CATALYSIS

Extraordinarily Effective Promotion by Sodium in Emission Control Catalysis: NO Reduction by Propene over Na-Promoted Pt/γ-Al2O3

i. v. yentekakis, m. konsolakis, r. m. lambert, n. macleod and l. nalbantian, Appi. Catai. B: Environ ., 1999, 22, (2), 123-133

The catalytic activity and selectivity of Pt/γ-Al2O3, for the reduction of NO by propene, was found to be promoted extremely strongly by Na at 470-770 K. Rate increases of two-orders of magnitude were achievable, while the selectivity towards N2 was improved from ∼ 15% over Na-free unpromoted Pt to > 95% over 4.18 wt.% Na-promoted Pt.

Treatment of Combined Bleach Plant Effluents via Wet Oxidation over a Pd-Pt-Ce/Alumina Catalyst

q. zhang and k. t. chuang, Environ. Sci. Technol ., 1999, 33, (20), 3641-3644

Pd-Pt-Ce/Al2O3 (1) shows promising activity over traditional Fe2O3, ZnO-type, oxidation catalysts for the treatment of bleach plant effluents. At 443 K and 1.5 MPa in a slurry reactor, 65% total organic carbon (TOC) and 99% colour were removed after a 3 h treatment, while only 10% TOC and 79% colour reduction were achieved without catalyst under the same experimental conditions. Cheap ferrous-based alloy may be used as the construction material for the process equipment. (1) may also be applied to the treatment of other organic wastes.

Dowex® 1-Supported PtCl4 Ion Pair as a Recycle Hydrogenation Catalyst

m. setty-fichman, k. kupferman, v. batz, c. rottman, y. sasson and j. blum, J. Mol. Catal. A: Chem ., 1999, 144, (1), 159-163

Polystyrene-supported ion pairs formed from PtCl4 and Dowex® 1 anion exchangers in EtOH, were found to be sufficiently stable under H2 to function as efficient and recyclable catalysts for the hydrogenation of various alkenes and other unsaturated compounds at < 35°C. In the hydrogenation of 1-decene, the intraparticle diffusion of the substrate contributed to the overall rate of the reaction. XPS identified Pt(II) and Pt(IV) species in the reaction mixture. No Pt(0) was traced.

Water-Soluble Colloidal Adams Catalyst: Preparation and Use in Catalysis

m.t. reetz and m.g.koch, J. Am. Chem. Soc, 1999, 121, (34), 7933-7934

The hydrolysis/condensation of PtCl4 or H2PtCl6 under basic conditions in the presence of carbo- or sulfobetaine stabilisers was shown to be a simple route to preparing H2O-soluble, stable, nanosized colloidal PtO2. The nanoparticles can be immobilised on neutral Al2O3 with the formation of highly active heterogeneous (pre)catalysts. This route was extended to the fabrication of bimetallic PtRuOx systems. Such H2O-soluble mixed metal oxides have potential as chemical (pre)catalysts in organic transformations and electrocatalysts in fuel cells.

Pd-Cu Supported on Anionic Polymers - Promising Catalysts for Removal of Nitrates from Drinking Water

d. gaŠparovlcovÁ, m. krÁlik and m. hronec, Collect. Czech. Chem. Commun ., 1999, 64, (3), 502-514

Bimetallic catalyst (1) with 2 wt.% Pd and 0.5 wt.% Cu, deposited on microporous anionic resin Dowex 50 W X 4, was able to reduce the NO3- content in H2O from 100 to 47 mg l-1 after a 4 h treatment (1 mmol Pd per litre of H2O) at ambient temperature and atmospheric pressure with vigorous stirring of the reaction mixture. (1) kept its activity for 2 further cycles. The catalyst, regenerated with a dilute mineral acid, had only slightly lower activity and selectivity for N2 formation than the original catalyst.

Methane Combustion on Sol-Gel Rh/ZrO2-SiO2 Catalysts

g. pecchi, p. reyes, f. orellana, t. lÓpez, r. gÓmez and j. l. g. fierro, J. Chem. Technol. Biotechnol ., 1999, 74, (9), 897-903

Studies of Rh/ZrO2-SiO2 catalysts (1) prepared by the impregnation of mixed ZrO2-SiO2 (by the sol-gel method) showed that the specific area and porosity depended strongly on the pH of the gelation. When Zr(acac)4 is used as a precursor, no significant changes in surface area occurred, but important changes in pore size distribution were detected. With Zr alkoxide, both the surface area and the porosity changed significantly. The catalytic activity for CH4 combustion depends mainly on the porosity of (1) and the presence of Cl, which induce an inhibitory effect on the combustion.

HOMOGENEOUS CATALYSIS

Copolymerization of Carbon Monoxide with Ethene Catalyzed by Bis-Chelated Palladium(ll) Complexes Containing Diphosphine and Dinitrogen Ligands

c. bianchini, h. m. lee, p. barbaro, a. meli, s. moneti and f. vizza, New J. Chem ., 1999, 23, (9), 929-938

[Pd(P-P)(N-N)x](PF6)2 (P-P = 1, 3-bis(diphenylphosphino)propane, meso -2,4-bis(diphenylphosphino)pentane (meso -bdpp), rac -2,4-bis(diphenylphosphino)pentane, 2,2’-bis(diphenylphosphinoethyl)pentane; N-N = 2,2’-bipyridine (bipy; x = 1), 1,8-naphthyridine (x = 2)) were tested as catalyst precursors for the copotymerisation of CO and C2H4 in MeOH in either autoclaves or high pressure sapphire NMR tubes. [Pd(meso -bdpp) (N,N’-bipy)]-(PF6)2 with both 1,4-benzoquinone and p -toluenesulfonic acid showed the best catalytic performance.

Catalytic Hydrogenation and Deuteration of Phospholipid Model Membranes with a Water-Soluble Chlorotris(1,3,5-triaza-7-phosphaadamantane)-rhodium(l) Complex Catalyst

l. nÁdasdi and f. joÓ, Inorg. Chim. Acta, 1999, 293, (2), 218-222

The title Rh complex was an active catalyst for the hydrogenation of phospholipid liposomes in H2O under mild conditions. The highest conversion was achieved at pH 4.70. Formation of asymmetrically dideuterated lipids, together with isomerisation and kinetic results demonstrated the important role of the reversible formation of an alkyl-Rh intermediate in the mechanism.

The First Efficient Hydroaminomethylation with Ammonia: With Dual Metal Catalysts and Two-Phase Catalysis to Primary Amines

b. zimmrrmann, j. herwig and m. beller, Angew. Chem. Int. Ed ., 1999, 38, (16), 2372-2375

The highly selective hydroaminomethylation of olefins with NH3 to form linear primary and secondary aliphatic amines with a new Rh/Ir/TPPTS catalyst (1) has been demonstrated. Aminomethylation of 1-pentene with synthesis gas (CO:H2 = 1:5) in the presence of (1) under standard hydroformylation conditions (130°C; 120 bar) in an aqueous two-phase system gave amines in 75% yield.

Highly Regio- and Enantio-Selective Rhodium-Catalysed Asymmetric Hydroformylation without Organic Solvents

g. franciÒ and w. leitner, Chem. Commun ., 1999, (17), 1663-1664

The use of a Rh catalyst with a new perfluoroalkyl-substituted (R,S)-H2F6-BINAPHOS ligand (1) has allowed the efficient and highly regio- and enantioselective hydroformylation of vinyl arenes in compressed CO2. Similar catalytic activity and the same level of enantio-control. as (R,S)-BINAPHOS ligand in benzene, an ecologically and toxicologically hazardous organic solvent, are achieved. The substitution pattern of (1) is crucial for the unprecedented high regioselectivity.

Asymmetric Hydroformylation of Vinyl Acetate with BINAP-Rhodium(I) Complexes

d. hoegaerts and p. a. jacobs, Tetrahedron: Asymmetry, 1999, 10, (15), 3039-3043

(R)-BINAP-Rh(I) complexes derived from Rh(acac)(CO), and [Rh(μ-OMe)(cod)]2 were used for the asymmetric hydroformylation of vinyl acetate. Enantiomeric excesses of ≤ 60% were achieved with regioselectivities of ≤ 99%. Applying 10 bar of a 1:1 mixture of CO:H2 gave good activities and selectivities. The reaction rate is inversely dependent on the CO partial pressure. Increasing the H2 partial pressure leads to hydrogenation of the substrate.

Catalytic Water Oxidation Using Chemically Generated Ru(bpy)33+ Oxidant

t. abe, y. tamada, h. shiroishi, m. nukaga and m. kaneko, J. Mol. Catal, A: Chem ., 1999, 144, (3), 389-395

In a catalytic H2O oxidation system composed of Ru(bpy)33+ and RuO2 adsorbing Ru-red, a much higher amount of O2 evolved than in a homogeneous Ru(bpy)33+/Ru-red system. The amount of O2 evolved increased with the amount of Ru-red adsorbed in RuO2, but higher amounts of absorbed Ru-red resulted in a decrease in O2 evolution. This is ascribed to bimolecular decomposition of Ru-red in the RuO2 at higher concentrations.

FUEL CELLS

Temperature and Pressure Dependence of O2 Reduction at Pt | Nation® 117 and Pt | BAM® 407 Interfaces

p. d. beattie, v. i. basura and s. holdcroft, J. Electroanal Chem ., 1999, 468, (2), 180-192

Kinetic and mass transport parameters have been determined for the O2 reduction reaction at the interface between a Pt disk electrode (50 μm) and two solid polymer electrode membranes: Nation® 117 (1) and a BAM® 407 membrane (2) (for PEMFC). These materials were investigated at 303-343 K and O2 pressures of 2-5 atm absolute, at 100% relative humidity. The membranes have similar permeabilities, but the diffusion coefficients and solubilities of O2 are very different, being related to the H2O content of the respective material.

ELECTRICAL AND ELECTRONIC ENGINEERING

Optimizing Pd-Ge Ohmic Contact to GaAs Through Microstructure Control

f. radulescu and j. m. mccarthy, J. Vac. Sci. Technol. B, 1999, 17, (5), 2294-2299

DSC together with TEM was used to study the microstructure evolution and the corresponding solid state reactions that take place during the formation of Pd-Ge ohmic contacts on GaAs. Four solid state reactions were identified: Pd-Ge interdiffusion, hexagonal Pd2Ge formation, transformation into PdGe and excess Ge crystallisation. For good ohmic contact, Ge transport to the interface with GaAs is the key.

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