Explain geometrical isomerism in Co-ordination compounds giving suitable examples.

Explanation

`rarr` Geometrical isomerism arises in Co-ordination complexes due to different possible geometric arrangements of the ligands.
`rarr` This isomerism found in complexes with Co-ordination numbers 4 and 6.
`rarr` In a square planar complex of formula `[MX_(2)L_(2)]` the two ligands may be arranged in adjacent to each other in a cis isomer (or) opposite to each other in a trans isomer.

`rarr` Square planar complex of type [MAB XL] shows three isomers two-cis and one trans. (A, B, X, L are unidentate ligands is square planar complex).
`rarr` Geometrical isomerism is not possible in tetrahedral geometry.
`rarr` In octahedral complexes of formula `[MX_(2)L_(4)]` in which two ligands X may be oriented cis or trans to each other.

`rarr` Another type of geometrical isomerism occurs in octahedral Co-ordination compoundsof type `[Ma_(3)b_(3)]` if three donar atoms of the same ligands occupy adjacent positions at the corners of an octahedral face then it is facial (fac) isomer. When the positions occupied are around the meridian of the octahedran then it is meridonial (mer) isomer.

The facial (fac) and meridonial (mer) isomers of `[Co(NH_(3))_(3)(NO_(2))_(3)]`