Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
For full article and contact information, see Angew. Chem. Int. Ed. 1999, 38 (20), 3026 - 3028
Perfect use of atmospheric oxygen
A compound containing the metal Osmium may
reduce waste in chemical reactions with oxygen
Oxygen gas doesn't just keep us alive; it is also crucial to chemical industry. Many important basic chemicals are produced when chemists allow oxygen to react with other simple substances. The problem with this is that many reactions are not successful at transferring both atoms of the oxygen molecule to the desired product - often, only one reacts in the desired manner, while the other generally forms troublesome by-products. Even nature cannot always "fully" employ oxygen; in the body, many reactions with this gas form water as a by-product.
At the Institute for Organic Catalysis Research in Rostock, Matthias Beller, Christian Döbler and Gerald Mehltretter have now been able to do what was thought to be nearly impossible: to produce diols - "double alcohols" that contain two oxygen atoms - in a single step from ordinary oxygen and olefins such as ethylene or propylene. The chemists get help in this reaction from osmium metal, which decomposes the oxygen in air down to separate atoms and then transfers both of these to the olefins - without "oxygen waste".
Diols are used in large quantities as antifreeze, as well as serving as basic building blocks for a large variety of plastics. Many pharmaceuticals are also derived from these simple molecules. Currently, diols are awkwardly synthesized in two steps. Indeed, it has been known for some time that diols could be synthesized from olefins in one step when osmium compounds are used as a catalyst. Industry could not make use of these one-step processes, however, because they required large quantities of expensive, oxygen-containing, specialty chemicals, whose synthesis generated large amounts of waste. In contrast, oxygen gas is available in practically unlimited amounts in air, and is highly economical. The basic building blocks of many important chemical products could thus be produced more cheaply and in a more environmentally friendly fashion with the help of the Rostock discovery.
Beller's team is not the first to experiment with oxygen and osmium. Earlier attempts, carried out by other chemists decades ago, under aggressive conditions, led to the destruction of the newly formed diols by the metal - the idea was abandoned. Beller says, "Sometimes we achieve more, if we simply tame our reactions a little."