The complex(es) which can exhibit the type of isomerism shown by [Pt(NH3)2Br2] is(are):
Correct Answer :
[Pt(NH3)2Cl4]
[Cr(en)2(H2O)(SO4)]+
Solution :
The correct options are [Pt(NH3)2Cl4] and [Cr(en)2(H2O)(SO4)]+.
Step 1: Identify the type of isomerism in the reference complex
The given complex is [Pt(NH3)2Br2].
In this complex, Platinum (Pt2+) has a coordination number of 4 and adopts a square planar geometry. A square planar complex of the type exhibits geometrical isomerism (specifically cis-trans isomerism):
1. cis-isomer: The identical ligands (e.g., NH3 or Br) are adjacent to each other (90° apart).
2. trans-isomer: The identical ligands are opposite to each other (180° apart).
Therefore, the reference complex exhibits geometrical isomerism (cis-trans isomerism).
Step 2: Analyze each given option for geometrical isomerism
Option 1: [Pt(en)(SCN)2]
Here, 'en' (ethylenediamine) is a bidentate ligand. Because the two coordinating donor atoms of 'en' must attach to adjacent (cis) positions in a square planar complex, the two SCN- ligands are restricted to being cis to each other. Consequently, a trans isomer cannot form without breaking the ring constraint of ethylenediamine. Thus, this complex does NOT exhibit cis-trans geometrical isomerism.
Option 2: [Zn(NH3)2Cl2]
Zinc (Zn2+) forms a 4-coordinate complex with an sp3 hybridized tetrahedral geometry. In a symmetrical tetrahedral complex of type , all positions are adjacent and equivalent relative to one another (bond angle is ~109.5°). Thus, geometrical isomerism is NOT possible for tetrahedral complexes.
Option 3: [Pt(NH3)2Cl4]
This is an octahedral complex of Platinum (Pt4+) with coordination number 6, conforming to the formula type .
This complex exhibits geometrical isomerism:
- cis-isomer: The two NH3 ligands occupy adjacent positions (at a 90° angle).
- trans-isomer: The two NH3 ligands occupy opposite positions across the metal center (at a 180° angle).
Hence, [Pt(NH3)2Cl4] exhibits geometrical isomerism.
Option 4: [Cr(en)2(H2O)(SO4)]+
This is an octahedral complex of Chromium (Cr3+) with coordination number 6, corresponding to the general type (where 'en' is a symmetrical bidentate ligand, and H2O and SO42- are monodentate ligands).
It exhibits geometrical isomerism based on the positions of the monodentate ligands H2O and SO42-:
- cis-isomer: The H2O and SO42- ligands are adjacent (90° apart).
- trans-isomer: The H2O and SO42- ligands are opposite each other (180° apart).
Hence, [Cr(en)2(H2O)(SO4)]+ exhibits geometrical isomerism.
Conclusion:
Both [Pt(NH3)2Cl4] and [Cr(en)2(H2O)(SO4)]+ exhibit geometrical isomerism, the same type of isomerism shown by [Pt(NH3)2Br2].
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