Platinum Metals Review - Volume 31, Issue 3, 1987

The crevice corrosion that occurs on titanium in chloride solutions at elevated temperatures can constitute a serious problem. The resistance of three titanium materials to this form of corrosion has been evaluated by immersion and electrochemical tests. The results show that all three possess superior corrosion resistance to that of commercially pure titanium, and that the two which contain palladium are the best. On the basis of these tests, mechanical properties and in-service experience, guide lines for the advantageous use of these materials are proposed.

Ultraviolet irradiation of a wide variety of ketones in aqueous solution containing a low concentration of an alcohol results in the formation of the two corresponding ketyl radicals, which are strong reducing agents. In the presence of colloidal platinum particles, these radicals will reduce water to hydrogen gas with high overall quantum efficiency. This is a general reaction, able to operate in sunlight, for which the mechanism is discussed in detail. The importance of the colloidal catalyst is stressed and, by changing the catalyst, different reaction products are obtainable.

Since the original demonstrations of homogeneous organometallic catalysis under mild conditions in the 1960s there has been much progress. A central focus for development has been asymmetric synthesis, through the use of optically active ligands. Chiral chelating biphosphines have played a key role in these advances, which have led to: asymmetric hydrogenation as a route to amino-acids and Vitamin E precursors, kinetic resolution in directed hydrogenation, asymmetric isomerisation of olefins in a route to citronellol, and asymmetric catalytic C-C bond formation. This review highlights recent developments.