#### Answer

(a) \[{{\left[ Cr{{\left( N{{H}_{3}} \right)}_{5}}\left( OH \right) \right]}^{2+}}\]
will not exhibit geometrical isomerism.
(b) \[{{\left[ Cr{{\left( en \right)}_{2}}C{{l}_{2}} \right]}^{+}}\]
will exhibit geometrical isomerism.
(c) \[{{\left[ Cr\left( {{H}_{2}}O \right){{\left( N{{H}_{3}} \right)}_{3}}C{{l}_{2}} \right]}^{+}}\]
will exhibit geometrical isomerism.
(d) \[{{\left[ Pt\left( N{{H}_{3}} \right)C{{l}_{3}} \right]}^{-}}\]
will not exhibit geometrical isomerism.
(e) \[\left[ Pt{{\left( {{H}_{2}}O \right)}_{2}}{{\left( CN \right)}_{2}} \right]\]
will exhibit geometrical isomerism.

#### Work Step by Step

Geometrical isomerism is a type of stereoisomerism that results when the ligands bonded to the metal have a different spatial arrangement. Geometrical isomerism (cis–trans isomerism) occurs in the square planar complexes of the type \[~M{{A}_{2}}{{B}_{2}}\] and octahedral complexes of the type \[M{{A}_{4}}{{B}_{2}}\]. Geometrical isomerism does not occur in tetrahedral complexes because all the bond angles around the central metal and each corner of a tetrahedron can be considered to be adjacent to all other corners. Similarly, a linear complex cannot exhibit cis–trans isomerism.