Platinum Metals Review - Volume 48, Issue 4, 2004

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

Thin films of metal-hexacyanoiridium(III) (MHCI), KxMy[Ir(CN)6]z, where M = Ru, Fe were electrochemically prepared and used as surface modifiers for glassy carbon electrodes. The redox behaviour of the counter/central ions of these films was investigated in aqueous electrolytes using cyclic voltammetry, chronocoulometry and electrochemical impedance spectroscopy. An electrochemical synthesis of zeolite-like films of KxMy[Ir(CN)6]z and KxFey[Fe(CN)6]z (Prussian blue) was also undertaken using the cyclic voltammetric technique. Porous multifilm assemblies of Prussian blue and MHCI were formed either by the direct electrodeposition of Prussian blue over MHCI or Prussian blue over MHCI during repetitive potential cycling, or by electrochemically-driven insertion-substitution methods. In acidic aqueous KCl, iron hexacyano iridate (FeHCI) displays two redox waves with formal potential E^of ≈, 0.35 and 0.6 V vs. Ag/AgCl. The electrochemical behaviour of FeHCI was compared with that of related hexacyanometallate compounds, such as KRux[Ru(CN)6]y, KRux[Fe(CN)6]yand KFex[Fe(CN)6]y. In addition, evidence for the catalytic behaviour of MHCIfilms towards the reduction of iodate, IO3^-, is reported.

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

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

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