Full Text for Volume 48 Number 3 (July 2004)

This issue contains the following:

Magnus’ Green Salt — a Quasi-One-Dimensional Compound
Magnus’ green salt, discovered in the 1830s, is a quasi-one-dimensional compound [Pt(NH₃)₄] [PtCl₄] with Pt(II) ions linked in a linear array. Although it is insoluble in water and organic solvents, some soluble and therefore processible derivatives have recently been synthesised. Walter Caseri from ETH Zentrum, Zürich, Switzerland, describes the complex [Pt(NH₂dmoc)₄][PtCl₄], dmoc = (S)-3,7-dimethyloctyl, which is green and has electrical conductivity similar to that of Magnus’ green salt. Films of this compound can function as an active semiconducting layer in field effect transistors (FETs). Such devices have better stability in air and water than unprotected FETs made from typical organic polymers. Magnus’ salt derivatives may thus find use in components of mass-produced "plastic electronics ".

Sonochemical Asymmetric Hydrogenation with Palladium
Ultrasonic cleaning of a palladium (Pd) catalyst that has an attached chemical modifier both cleans the Pd surface and enhances the adsorption of the modifier and the enantioselectivity of an asymmetric hydrogenation reaction. Researchers at Michigan Technological University, Houghton, U.S.A., used sonication during the asymmetric hydrogenation of isophorone in the presence of a proline-modified Pd/alumina catalyst. The proline modifier was responsible for the high enantiomeric excess attained, and it is suggested that catalysts modified by proline could become important for C=C hydrogenation of a,b-unsaturated carbonyl compounds.

Ethanol Reactions on Precious Metal/Ceria Catalysts
The complexity of ethanol reactions on the surfaces of Pt, Pd, rhodium (Rh) and gold (Au)/ceria catalysts is outlined by Hicham Idriss from the University of Auckland, New Zealand. Hydrogen production from ethanol is directly related to two main steps. The first involves breaking the carbon-carbon bond, and Rh appears to be the most suitable catalyst for this reaction at reasonable operating temperatures. The second involves CO oxidation to CO₂. While finely dispersed Au is a very active catalyst for CO oxidation during TPD, the high temperature requirement for good hydrogen yield in steady state conditions may favour other metals, such as Pt.

Colour Changes in Palladium Complexes due to Pressure
Colour changes in solids or solutions induced by external pressures (piezochromism) occur by pressure perturbations in the energy levels of the molecular orbitals, and these affect related electronic transitions. Hideo D. Takagi and his team from Nagoya University, Japan, review the effects of pressure perturbations on the absorption and emission spectra responsible for colour change in solid palladium complexes. The data may help towards applications for these metal complexes, in in situ pressure sensors or as conductors in extreme environments.

Treatment of Platinum Flotation Concentrates
A flowsheet for treating flotation concentrates produced from low-sulfide platinum-containing ores, from South Africa, has been developed by Ya. M. Shneerson and his colleagues from Gipronickel Institute JS, St. Petersburg, and the All-Russian R & D Institute of Chemical Technology, Moscow, Russia. The processes described provide low consumption of cheap reagents, complete water circulation, and high recovery of platinum group metals and non-ferrous metals into rich concentrates.

Review of Volume 9 of "Comprehensive Coordination Chemistry II"
Volume 9 of "Comprehensive Coordination Chemistry II. From Biology to Nanotechnology ", on "Applications of Coordination Chemistry ", edited by M. D. Ward et al. is reviewed by Janet Fisher, Rob Potter and Chris Barnard of the Johnson Matthey Technology Centre, Sonning Common, U.K. This book, in a ten volume set, gives a comprehensive overview of the applications of coordination chemistry, for example, on platinum group metals in catalysis, for optical applications, and in medicinal and biomedical applications.

The Minting of Platinum Roubles in Russia (Part III)
Four Russian rouble coins that Johnson Matthey owns have been examined by scientists at the Johnson Matthey Technology Centre, Sonning Common, U.K. David Willey, Allin Pratt and colleagues establish which of the four coins are forgeries.

Production of Fine Iridium Fibres
Furuya Kinzoku KK of Japan have produced fine iridium (Ir) and Ir oxide fibre from linear Ir compounds with Ir—Ir bonds as the chains in a fibre-like shape. The Ir fibre displays high melting point, chemical stability and excellent catalyst characteristics.

Platinum Catalysts in PEMFCs
The use of carbon multiwalled nanotubes (MWNTs) as the support for Pt in PEMFCs has been investigated by a team from the University of California, Riverside, U.S.A. By reducing the Pt particle size to ~ 2.5 nm, improving MWNT yield and reducing the tube diameter, fuel cells with C nanotube-based platinum catalysts could achieve superior performance.

Optical Hydrogen Detection Using Palladium-Coated Silicon
Scientists at the University of California, San Diego, U.S.A., have designed a hydrogen sensor that uses Pd-coated porous silicon and optical interferometry. The sensor reliably detects hydrogen concentrations well below the explosive limit. The sensor is safe, sensitive, selective, reproducible and can operate at room temperature.

Final Analysis: Safeguarding Thermocouple Performance
Roger Wilkinson (Johnson Matthey Noble Metals, U.K.) continues his advice on thermocouple maintenance. Here he examines minimising the drift in thermocouples due to rhodium.

The issue ends with a selection of abstracts based on recently published patent and scientific literature.

Susan V. Ashton
Editor

Contact
The Editor, Platinum Metals Review, Johnson Matthey PLC, Orchard Road, Royston, Hertfordshire SG8 5HE, United Kingdom; Fax +44 (0) 1763 256359; Email jmpmr@matthey.com

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