Platinum Metals Review - Volume 44, Issue 4, 2000

It may at first sight seem strange that concepts developed by Albert Einstein in the first decade of the 20th century to explain the structure and dynamics of the cosmos should have any relevance to chemistry. However, it is now quite clear that the chemical behaviour of the heavier elements in particular is dominated by what are termed “relativistic effects”. This article explores the implications of this for the coordination and chemisorption of carbon monoxide and unsaturated hydrocarbons, and their reactions in homogeneous and heterogeneous catalysis involving the platinum group metals.

Not long ago structural intermetallics were metallurgical curiosities rather than the focus of a serious campaign to topple the supremacy of nickel-based superalloys. Indeed, a handful of intermetallic compounds, notably the titanium and nickel aluminides, have succeeded in making it to the point of operational testing; but, if anything, they have highlighted the challenges facing a new generation of ultra-high temperature materials. Two constraints in particular have directed developments. First, at the core of the development of intermetallics, is the need to address the dual requirements of low-temperature toughness and high-temperature strength central to structural applications. Second, the operating conditions of interest (temperatures above 1150°C) call for a marked improvement in the environmental resistance of the materials. In these respects, systems based on platinum group metals deserve attention. The potential benefits resulting from using composite microstructures based on platinum, iridium and ruthenium are highlighted here, using collaborative studies being undertaken by Mintek and a number of alloy development centres.

The first two parts of this paper appeared in the April and July issues of this Journal. Part I looked at types of platinum group metals catalysts and metathesis activity and selectivity. Part II examined specific syntheses catalysed by these catalysts, in particular, reactions catalysed by ruthenium carbenes. This resulted in the syntheses of various carbocycles, heterocycles, metallacycles, crown ethers, polycyclic polymers, natural compounds and sub-units of biologically active compounds. The concluding part of this review deals first with acyclic diene metathesis and then with ring-opening metathesis polymerisations, and ranges of products formed by these reactions are given.

The history of the discovery of the isotopes of platinum, made over some 61 years between 1935 and 1996, can be gleaned from the various editions of the monograph “Table of Isotopes” (1–8). However, except for a few cases, in general, little attempt has been made to correlate the circumstances of the discoveries of the isotopes of individual elements. In this article attention is drawn to the work of pioneering scientists who in a comparatively short period of creativity discovered the majority of the isotopes of platinum.