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Encyclopedia of Physical Science and Technology EN003D-147 June 13, 2001 22:58

Coordination Compounds

R. D. Gillard
University of Wales, Cardiff, Wales

I. Introduction
II. Formation
III. Electronic Configurations
IV. Shape
V. Biological Metal Complexing
VI. Therapeutic Metal Complexes

GLOSSARY SF 6 are isoelectronic with each other, as are [AuCl 2 ] ,
−
HgCl 2 , and [TlCl 2 ] .
+
Br¨onsted base Proton acceptor. Isomerism Existence of more than one distinct substance
Chelation Binding of a single ligand to a single metal ion with the same composition, for example, ammonium
through two (or more) Br¨onsted donor atoms, making cyanate, NH 4 NCO, and urea, (H 2 N) 2 CO, both of which
ring structures. are CH 4 N 2 O in stoichiometry, or potassium fulminate,
Chrysotherapy Treatment of disease with gold com- K(CNO), and potassium cyanate, K(NCO). The dis-
pounds. tinct substances are called isomers.
Complex Species formed by combination between a Labile Attaining equilibrium rapidly.
metal ion and a ligand. Ligand Any moiety bonded to a metal ion in a complex;
Coordination Formation of a link between a metal ion often denoted by L in formulas and equations.
andaligandbythedonationofelectronsfromtheligand Resolution Separation of enantiomers from one another.
to the metal ion. Stability constant Thermodynamic equilibrium constant
Coordination number Number of ligand atoms directly measuring the ease of formation of a complex ion from
attached to a central metal ion in a complex. These its constituents [the metal ion and the ligand(s)].
directly attached ligands make up the first coordination
sphere. CHEMISTRY DEALS WITH changes (reactions) of sub-
Enantiomers Isomers that are related as an object and its stances such as the conversion of organic matter (e.g.,
mirror image. sugar) with dioxygen to carbon dioxide and water:
Isoelectronic Pertaining to species (whether molecules,
C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O
ions, or radicals) that have the same total number of
electrons occupying the same orbitals around the same Metal complexes are formed from Br¨onsted bases (sub-
3−
number of nuclei. For example, AlF , SiF ,PF , and stances with many electrons) and Lewis acids (usually
2−
−
6 6 6
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