Assertion: Complexes of MX6, and MX5L type (X and L are unidentate ligands) do not show geometrical isomerism.

Reason: Geometrical isomerism is not shown by complexes of coordination number 6.

1. Both assertion and reason are true and the reason is the correct explanation of assertion.

2. Both assertion and reason are true and the reason is not the correct explanation of assertion.

3. Assertion is true but the reason is false.

4. Assertion is false but the reason is true.

Hint: MX6 and MX5L  contains an element of symmetry

Complexes of ${\mathrm{MX}}_{6}$ and ${\mathrm{MX}}_{5L}$ type (X and L are unidentate) do not show geometrical isomerism due to the presence of a plane of symmetry and the necessary condition for showing geometrical isomerism is that complex is a must of type.

This type of isomerism arises in heteroleptic complexes due to different possible geometric arrangements of the ligands. Important examples of this behavior are found with coordination numbers 4 and 6.

Hence, Assertion is true but the reason is false.