Platinum Metals Review - Volume 50, Issue 2, 2006

Phosphoramidites, and in particular those derived from BINOL, the MonoPhos family of ligands, have proven extremely useful for the asymmetric hydrogenation of carbon–carbon unsaturation using a rhodium catalyst. Many classes of alkenes can be reduced by these catalyst systems. The use of high-throughput experimentation can be applied to the synthesis of MonoPhos ligands and their subsequent screening, in order to find an appropriate candidate for a specific transformation. Suitable mixtures of ligands can also be found by these high-throughput methods.

Thermal conductivity and thermal expansion were measured for the L12 intermetallic compounds Rh3 X (X = Ti, Zr, Hf, V, Nb, Ta) in the temperature range 300–1100 K to evaluate the feasibility of applying the compounds as ultra-high temperature structural materials. The thermal conductivities of Rh3X are widely distributed over the range 32–103 W m^–1 K ^–1 at 300 K, but the differences between the thermal conductivities diminish at higher temperatures. A trend is observed in that the thermal conductivity of Rh3 X is greater if the constituent X belongs to Group 5 rather than to Group 4 in the Periodic Table. The coefficient of thermal expansion (CTE) values of Rh3X increase slightly with increasing temperature; values are concentrated around 10 × 10^–6 K^–1 at 800 K. CTE values of Rh3X decrease as X appears lower in the Periodic Table. It is demonstrated that Rh3Nb and Rh3Ta are suitable for ultra-high temperature structural applications due to their higher thermal conductivities and smaller CTE values.

This paper presents a detailed account of an array of well-defined ruthenium allenylidene complexes as a promising class of metathesis pre-catalysts. This type of ruthenium complex is readily accessible from commercial reagents, induces good to excellent metathesis catalytic activity and selectivity, and shows a great tolerance towards many organic functional groups. By virtue of these beneficial features, ruthenium allenylidene complexes allow synthesis of a wide range of heterocyclic and carbocyclic compounds through ring-closing metathesis (RCM) and enyne metathesis as well as production of specialty polymers by acyclic diene metathesis (ADMET) and ring-opening metathesis polymerisation (ROMP).

This is the fourth in a series of reviews of circumstances surrounding the discoveries of the isotopes of the six platinum group elements. The first review, on platinum isotopes, was published in this Journal in October 2000, the second, on iridium isotopes, was published here in October 2003 and the third, on osmium isotopes, was published in October 2004 (1). The current review looks at the discovery and the discoverers of the thirty-four isotopes of palladium.