Question 19 of 34advanced🔍 AnalyzeLong Answer3 marks

Write all the geometrical isomers of [Pt(NH3)(Br)(Cl)(py)] and how many of these will exhibit optical isomers?

Correct Answer

The complex [Pt(NH₃)(Br)(Cl)(py)] is a square planar complex with four different monodentate ligands. It exhibits three geometrical isomers:

  1. Isomer I: NH₃ trans to Br and Cl trans to py
  2. Isomer II: NH₃ trans to Cl and Br trans to py
  3. Isomer III: NH₃ trans to py and Br trans to Cl

None of these geometrical isomers will exhibit optical isomerism. Square planar complexes possess a plane of symmetry (the molecular plane itself), which makes them achiral. As stated in the context, optical isomerism is common in octahedral complexes involving didentate ligands, not in square planar complexes.

Exercise: EXERCISES | Q: 5.12 | (Page Page 22)
For More Understanding

Explanation

The question tests understanding of isomerism in coordination compounds. For square planar [MABCD] type complexes, three geometrical isomers exist based on different trans arrangements. Unlike octahedral complexes which can show optical activity (especially with didentate ligands), square planar complexes cannot exhibit optical isomerism due to the inherent plane of symmetry. The textbook context shows geometrical isomers for Pt complexes (Fig 5.2) and discusses optical isomerism primarily for octahedral complexes like [PtCl₂(en)₂]²⁺ where only the cis-isomer shows optical activity.

Solution Steps

  1. Step 1: Identify the geometry - Pt(II) forms square planar complexes with coordination number 4

  2. Step 2: For [MABCD] type square planar complex, determine geometrical isomers - three isomers based on different trans pair arrangements

  3. Step 3: Analyze optical isomerism - square planar complexes have a plane of symmetry, making them achiral and optically inactive

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