Metal Ions in a Coordination Environment

The description of some basic aspects regarding the coordination chemistry of metal ions is especially important for understanding their behavior in biological media. In the predominantly aqueous environment found in biological systems, the metal ions 

1 Coordinating Capacity of Metal Ions HSAB Theory 

A metal complex is formed by two main components a metal ion, called the generator of complex, and one or more anions or molecules called ligands. The number of coordinated ligands represents the coordination number (C.N.). In the simplest case, when the charges of both the metal ion and the ligands are not considered, the formation of a metal complex can be represented as 

Most theories of metal-Ugand bonding consider the Lewis behavior of the species involved. In a Lewis add-base reaction, a pair of electrons from a species is used to form a covalent bond with another spedes. A Lewis base is the species that donates an electron pair, and a Lewis acid is the species that accepts the electron pair. The reaction can be written. 

This series is known as the Irving-Williams stability series. 

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