Chromium: Inorganic & Coordination Chemistry
Published Online: 15 DEC 2011
Copyright © 2011 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Inorganic and Bioinorganic Chemistry
How to Cite
Theopold, K. H. 2011. Chromium: Inorganic & Coordination Chemistry. Encyclopedia of Inorganic and Bioinorganic Chemistry. .
- Published Online: 15 DEC 2011
The element chromium (Cr, atomic number 24) belongs to the first row of the transition metals, the properties of which are marked by partial occupation of their 3d orbitals. Together with molybdenum (Mo), tungsten (W), and unstable seaborgium (Sg), it makes up group 6 of the periodic table. Chromium is relatively abundant, occurring naturally in various oxide minerals (notably chromite, FeCr2O4). Because of its resistance to reaction with air and water, thin coatings of chromium are used to protect other metals against corrosion. Chromium features a great variety of accessible oxidation states; among these the +VI, +III, and +II states are of prime importance. Octahedral coordination compounds of Cr(III) are very stable and numerous; they have played a prominent role in the development of coordination chemistry. Hexavalent chromium is a very strong oxidant. It has traditionally been used in organic synthesis, but the inevitable metal wastes have discouraged its use as a stoichiometric oxidant. Cr(VI) is a known carcinogen, but there are no indications of adverse health effects of Cr(III); the latter is indeed an essential trace mineral implicated in glucose metabolism. Heterogeneous chromium catalysts play an important role in the catalysis of ethylene polymerization.
- transition metals;
- coordination compounds;
- metal toxicity;
- glucose tolerance factor;
- metal–metal bonds;
- polymerization catalysis