Answer
Cis-trans isomerism is one type of geometrical isomerism that occurs in the square planar complexes of the type \[MA2{{B}_{2}}\] and octahedral complexes of the type \[MA4{{B}_{2}}.\]
Work Step by Step
For example: Square planar complex Pt \[{{\left( N{{H}_{3}} \right)}_{2}}C{{l}_{2}}\] exhibits cis-trans isomerism.
Octahedral complex ion \[{{\left( Co{{\left( N{{H}_{3}} \right)}_{4}}C{{l}_{2}} \right)}^{+}}\] exhibits cis-trans isomerism.
Cis-trans isomerism does not occur in tetrahedral complexes because all the bond angles around the central metal are \[109.5,\] and each comer of a tetrahedron can be considered to be adjacent to all other corners. Similarly, a linear complex cannot exhibit cis-trans isomerism.
