[" Facial- meridional isomers is associated "],[" with which one of the following complex? "],[(M=" central metal ")]

Fac-Mer isomerism is associated with which of the following types of complexes ? (M is the central metal. A-A is a symmetrical bidentate ligand. A,B,C & D are monodentate ligands)

Which one of the following complex ions has geometrical isomers ?

Which one of the following complex ions has geometrical isomers ?

Which one of the following complex ions has geometrical isomers?