Coordination Compounds

Compounds in which transition metals make several anions or neutral molecules are called coordination compounds. Ex: Chlorofyll, haemoglobin, vitamin B-12 etc.

Werner’s theory for coordination compounds: In 1898, a swiss chemist propounded his theory of coordination compounds. The main points of this theory are as follows:

1. Metals show two types of linkages or valences- primary and secondary in coordination compounds.

2. The primary valences are normally ionisable and are satisfied by anions(negative ions).

3. The secondary valences are nonionisable.

4. The ions/groups bound by the secondary linkages to the metal have characteristic spatial arrangements corresponding to different coordination numbers.

Isomerism in coordination compounds: Compounds having same molecular formula but different structures are called and this phenomenon is called isomerism.

Coordination compounds show two types isomerism: 1. Structural isomerism and 2. Stereo isomerism

I.Structural isomerism : Isomerism due the difference in the structures of compounds is called structural isomerism. This isomerism is of four types:

2. Stereo or space isomerism : The isomerism due to the different relative positions of the ligands is known as stereo isomerism. This isomerism is of two types :

I. Geometrical isomerism : The isomerism in which isomers differ in the spatial distribution of atoms or groups about the central atom is known as geometrical isomerism. It is also known as cis-trans isomerism.

Ex :

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