Platinum Metals Review - Volume 51, Issue 2, 2007

Selectivity is a key success factor in the chiral catalyst technologies market. Understanding the fundamental processes that occur when a reagent interacts with a homogeneous single site catalyst, both in its approach and at the active site, is therefore critical to the rational design of new catalysts. Ruthenium-based asymmetric hydrogenation catalysts have been considered as part of a collaborative research project. [(S)-XylBINAP-RuH2-(S,S)-DPEN], first developed by Noyori (1–3), is studied as the parent or prototype model of a series of efficient hydrogenation catalysts, among them the catalysts based on the P-Phos, PhanePhos and ParaPhos ligand families (4).

Although the platinum-gold (Pt-Au) phase diagram shows a wide miscibility gap due to limited mutual solubility of the components, small particles (< 3 nm) form homogeneous alloys because all atoms retain their atomic electronic structure, and rehybridisation due to band formation does not take place. Supported Pt-Au catalysts are often superior to those containing Pt alone for low-temperature selective oxidations.

Heat treatment of platinum-5 wt.% copper (Pt-5% Cu) below 500°C is known to result in an ordering transformation which can significantly increase the hardness of the alloy. Microsample tensile testing of Pt-5% Cu shows that low-temperature heat treatment of previously cold-worked specimens results in an increase in yield strength and tensile strength, with a maximum in strength occurring after heat treatment at 300°C; but ductility is unchanged.

Perovskites are a large class of minerals, both naturally occurring and synthetically produced, with important technological applications. In this article, platinum group metal (pgm) perovskites are introduced as a relatively new catalyst material. Due to their high activity, versatile and stable structure and low pgm content, they can offer advantages over conventional catalysts. Some of the typical applications and preparation methods of pgm perovskites are reviewed, with particular focus on their potential use to address current challenges concerning autocatalysts, and in organic chemistry.