$\left[ Ni \left( NH _{3}\right)_{2} Cl _{2}\right]$ does not show structural isomerism
$\left[ Ni \left( NH _{3}\right)_{4}\left( H _{2} O \right)_{2}\right]^{2+} \&\left[ Pt \left( NH _{3}\right)_{2} Cl _{2}\right]$ show geometrical isomerism
$\left[ Ni ( en )_{3}\right]^{2+}$ show optical isomerism