1. Coordination chemistry

The origins of coordination chemistry lie in the work of A. Werner at the end of the 19th century . Based on his work, Werner postulated that metal ions possess two types of valence: primary valence (today called oxidation number) and secondary valence (today called coordination number), which can be different.

A coordination compound can be defined as a polyatomic structure in which an ion of a transition element, i.e. an element from blocks d or f of the periodic table (figure