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Copyright 2001, The American Chemical Society


NEWS OF THE WEEK
CATALYSIS
March 5,2001
Volume 79, Number 10
CENEAR 79 10 pp.11
ISSN 0009-2347
FAST WORK UNDER MILD CONDITIONS
Soluble gold catalyst uses O2 in air at room temperature to oxidize thioethers

Cosmetics, coatings, and fabrics that catalytically destroy contaminants in the air--for example, a skin cream that protects soldiers against blistering agents--could result from the discovery of a soluble gold complex that uses oxygen in the air to catalyze the selective oxidation of thioethers to sulfoxides under ambient conditions [J. Am. Chem. Soc., 123, 1625 (2001)].

7910notw2.ceThe catalyst was developed at Emory University by chemistry professor Craig L. Hill and coworkers Eric Boring and Yurii V. Geletii. It works several orders of magnitude faster than the best previously known soluble O2-based oxidation catalysts, which are active only at elevated temperatures. Hill believes the new complex is the first homogeneous catalyst that selectively oxidizes organic compounds under ambient conditions in air.

The active complex consists of a gold(III) center having two chloride ligands, one nitrate ligand, and one thioether ligand, which is the reaction substrate. Mechanistic studies indicate that the oxygen atom in the sulfoxide product comes from H2O, which is consumed and subsequently regenerated from O2 during the reaction. Molecular oxygen also serves to regenerate the Au(III) complex, which is reduced to Au(I) during the catalytic cycle.

The Emory chemists got on the trail of the new catalyst after they discovered that several inorganic complexes in a combinatorial library could catalyze the air oxidation of 2-chloroethyl ethyl sulfide. This thioether, which is difficult to convert to the sulfoxide, is used in the lab as a stand-in for mustard gas [bis(2-chloroethyl) sulfide], a chemical warfare agent.

Hill's group also has uncovered much more complex inorganic compounds that display "striking" catalytic properties in air, with or without solvents. The group is collaborating with Nanoscale Materials Inc. of Manhattan, Kan., to develop these catalysts for use against chemical warfare agents and for cleaning the air of polluting sulfur compounds.--RON DAGANI