Question

Giving suitable examples, discuss the geometrical isomerism shown by the following type of complex:

[M(AB)₂]^n±

Answer 1

• Complexes of the type [M(AB)₂]^n± can exhibit geometrical isomerism when AB is an unsymmetrical bidentate ligand that is, a ligand that coordinates to the central metal ion through two different donor atoms.
• This type of isomerism is usually found in square planar complexes (coordination number = 4), commonly formed by metal ions like Pt²⁺ and Pd²⁺.
• For example, [Pt(gly)₂] In this, Gly = Glycinato ligand (H₂NCH₂COO⁻), coordinates through N and O.
  Cis-isomer: The same donor atoms (e.g. both nitrogen atoms from two glycinato ligands) are adjacent to each other (90° apart).
  Trans-isomer: The same donor atoms are opposite each other (180° apart).