Question Details

The complex(es) which can exhibit the type of isomerism shown by [Pt(NH3)2Br2] is(are):

Options

A

[Pt(en)(SCN)2]

B

[Zn(NH3)2Cl2]

C

[Pt(NH3)2Cl4]

D

[Cr(en)2(H2O)(SO4)]+

Show Answer

Correct Answer :

Option C

[Pt(NH3)2Cl4]

Option D

[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 MA2B2 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 MA2B2, 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 MA2B4.

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 M(M-M)2AB (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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