Mercury: 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
Bebout, D. C. 2011. Mercury: Inorganic & Coordination Chemistry . Encyclopedia of Inorganic and Bioinorganic Chemistry. .
- Published Online: 15 DEC 2011
Mercury is one of the oldest known elements. The element exhibits surprisingly different chemistry from its congeners zinc and cadmium, and it is the only group 12 member without a known beneficial biological role. Unique properties associated with the element and its compounds have led to diverse applications. However, many of these are being phased out to minimize further increases in the environmental and atmospheric burden with this toxic heavy metal. Motivations to study the compounds and complexes of mercury include potential for discovery of novel properties such as high-temperature superconductivity and improved understanding of its interactions in physiological systems. Valuable characterization of mercury-containing compounds is possible with 199Hg NMR techniques.
Mercury is the only group 12 member to have a stable monovalent state. Observed primarily in the oldest known and most common of all metal polycations, Hg22+, this metal–metal bonded species readily disproportionates into Hg2+ and Hg0. Mercury(I) compounds, typically, have a linear structure of type XHgHgX. Halides, oxy salts, oxides, and coordination compounds with oxygen and weakly basic nitrogen-donor ligands are best known for Hg22+.
The most prevalent ionization state of mercury, Hg2+, is a d10 metal ion, which lacks strong coordination number and geometry preferences. As a result, structural characterization of its compounds by X-ray crystallography is particularly critical. A wide range of halides, pseudohalides, and chalcogenides of Hg2+ are known. The softness of Hg2+ has led to an investigation of coordination, with a wide variety of sulfur ligands and physiological sulfur donors being assumed to be the most important. Mercury(II) typically has a stronger affinity for S-, N-, and P-donors than any other divalent metal ion. However, Hg2+ also has a tendency to undergo incredibly rapid ligand exchange. Recent studies have shown that sterically demanding multidentate ligand systems can suppress ligand exchange processes.
- metal–metal bonds;
- relativistic effects;
- metal toxicity