Coordination Compounds

with -hybridisation has a square planar structure (see hint to 26 above).

In complex
Oxidation number of Co= +3
Electronic configuration of

In
In number of unpaired electrons is four, and is the ligand of weak field. Hence, it does not paired up electrons of d-orbital.
So, In
So, is paramagnetic.
has outer electronic configuration, but four unpaired electrons do not pair up because of weak field provided by

Geometrical isomerism is exhibited by only those compounds in which at least one double bond is present and different groups are attached to the same carbon atom.

fulfill both the conditions, so it exhibits geometrical (cis-trans) isomerism.