Coordination Compound

Examples, & Facts

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Oct 9, 2023 - 02:04

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Coordination compounds contain a central metal atom surrounded by nonmetal atoms or groups of atoms, called ligands. For example, vitamin B12 is made up of a central metallic cobalt ion bound to multiple nitrogen-containing ligands.

coordination compound, any of a class of substances with chemical structures in which a central metal atom is surrounded by nonmetal atoms or groups of atoms, called ligands, joined to it by chemical bonds. Coordination compounds include such substances as vitamin B₁₂, hemoglobin, and chlorophyll, dyes and pigments, and catalysts used in preparing organic substances.

Organometallic coordination compounds, which include transition metal compounds, may be characterized by “sandwich” structures that contain two unsaturated cyclic hydrocarbons on either side of a metal atom. Organometallic compounds are found in the p-, d-, s-, and f- blocks of the periodic table (the purple-shaded blocks; the transition metals include those elements in the d- and f-blocks).

A major application of coordination compounds is their use as catalysts, which serve to alter the rate of chemical reactions. Certain complex metal catalysts, for example, play a key role in the production of polyethylene and polypropylene. In addition, a very stable class of organometallic coordination compounds has provided impetus to the development of organometallic chemistry. Organometallic coordination compounds are sometimes characterized by “sandwich” structures, in which two molecules of an unsaturated cyclic hydrocarbon, which lacks one or more hydrogen atoms, bond on either side of a metal atom. This results in a highly stable aromatic system.

The following article covers the history, applications, and characteristics (including structure and bonding, principle types of complexes, and reactions and syntheses) of coordination compounds. For more information about specific properties or types of coordination compounds, see the articles isomerism; coordination number; chemical reaction; and organometallic compound.