Coordination Compounds: The Complex Story

From our study of the d-block and the f-block elements, we know that most of the transition metals form a wide variety of compounds. These compounds are called complex compounds. Here metal atoms (generally transition metal) are surrounded either by neutral molecules or anions or both.

The chemistry of these compounds is complex and their properties depend on the type and number of anions or neutral molecules bound to them. The chemistry of these compounds has been under study for a very long time. Complex compounds such as Prussian blue have been found to exist from early times. But only limited insight was available on these compounds until the 17th century. In modern chemistry, these types of compounds are referred to as coordination compounds.

Coordination Compounds

Complex Story Of Coordination Compounds

It has been observed that most transition metals form coordinate compounds. This complex forming property of transition metals is often attributed to the small sizes of metal ions with high ionic charges in them. Transition metals also have vacant d-orbitals available in them for the bond formation. This gives rise to the complex formation tendency of transition metals. Coordination compounds are generally studied in relation to the transition metals. But it has been seen that some main group elements such as Aluminum (Al), Tin (Sb), Lead (Pb) also form complex compounds.

The neutral molecules or the anions that are attached to the metal are generally called ligands and they greatly affect the properties of the coordinate compounds. The transition metal atom to which the ligands are bound in coordination compounds is known as the central atom or the coordination centre. The total number of ligands attached to a coordination centre is referred to as the coordination number for that particular compound.

The study of coordinate compounds is particularly important due to their presence in biological systems. The developments in complex compound chemistry have helped the scientists to exploit the applications of coordination compounds in the field of medical sciences. These complex compounds are now used in various industrial processes, such as extraction of metals, as catalysts, etc. These compounds thus play an important role in our daily lives.


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