Although homogeneous gold catalysis was known previously, an exponential growth was only induced 12 years ago. The key findings which induce that rise of the field are discussed. This includes early reactions of allenes and furanynes and intermediates of these conversions as well as hydroarylation reactions. Other substrate types addressed are alkynyl epoxides and N-propargyl carboxamides. Important vinylgold intermediates, the transmetalation from gold to other transition metals, the development of new ligands for gold catalysis, and significant contributions from computational chemistry are other crucial points for the field highlighted here.

Gold-Catalyzed Organic Reactions

The surface and materials science of tin oxide

Thanks to its unusual stability, metallic gold has been used for thousands of years in jewelry, currency, chinaware, and so forth. However, gold had not become the chemists’ “precious metal” until very recently. In the past few years, reports on gold-catalyzed organic transformations have increased substantially. Thanks to gold-based catalysts, various organic transformations have been accessible under facile conditions with both high yields and chemoselectivity.

Gold-catalyzed organic transformations.

Despite occasional references in the older literature to the ability of gold to catalyze certain reactions, the metal has until recently had the reputation of being one of the least catalytically useful. The recent discovery that some supported gold catalysts can affect the oxidation of carbon monoxide at or below ambient temperature has, however, focused attention on the metal's ability in this respect. For oxidation of carbon monoxide at low temperature, catalysts comprising small (<5 nm) gold particles supported preferably on an oxide of the first transition series (e.g., TiO2, α-Fe2O3) are needed. Deposition–precipitation and coprecipitation are better methods than impregnation for this purpose and provide the desired intimacy of contact between metal and support. High activity may well originate at sites at the gold–support interface, with the support making a vital contribution. Stable activity can result by optimizing aging in solution during the preparation, and low calcination temperatures are ge...

Catalysis By Gold

Hydrogen Spillover. Facts and Fiction

Recently, interest in catalytic gasification of carbon has expanded rapidly. In consequence of the volume and diversity of this interest, there is a need to collate, summarize, and interpret the available information on the mechanism of gasification catalyst action.

The Mechanism of the Catalytic Gasification of Coal Char: A Critical Review

The statement is often made that free radicals will be produced during the violent collapse of transient cavities in liquids, that may result from the passage of ultrasonic waves in the low megahertz frequency range. Evidence for such free radicals is mostly indirect. We have insonated some argon-saturated aqueous solutions of biological molecules (trypsin, Dulbecco's Minimum Essential Medium, fetal bovine serum, and human blood plasma) and whole human blood, all containing a spin trapping compound, at 1 MHz, continuous wave, 6.6 W/cm2 (SPTA) for 15 min at 4-8 degrees C. Electron spin resonance spectra of the samples were recorded 10 and 30 min. after cessation of insonation. The spectra included those of spin adducts formed with .OH and .H radicals, which were absent in the cases of the sham treated controls. Thus, we have demonstrated the formation of the highly reactive .OH and .H radicals in the insonated media, even in the presence of natural radical scavengers in the mammalian derived products.

Evidence for free radical production by ultrasonic cavitation in biological media

A carbonaceous material, such as crushed coal, is admixed or impregnated with an inexpensive alkali metal compound, such as sodium chloride, and then pretreated with a stream containing steam at a temperature of 350° to 650° C. to enhance the catalytic activity of the mixture in a subsequent gasification of the mixture. The treatment may result in the transformation of the alkali metal compound into another, more catalytically active, form.

Kenneth M. Sancier

Papers

The Mechanism of the Catalytic Gasification of Coal Char: A Critical Review

Evidence for free radical production by ultrasonic cavitation in biological media

In situ formation of coal gasification catalysts from low cost alkali metal salts

Hydrogen migration on Alumina/Palladium catalysts for benzene hydrogenation

ESR spectra of metal oxide catalysts during propylene oxidation