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The complex(es), which can exhibit the type of isomerism shown by [Pt(NH$$_3$$)$$_2$$Br$$_2$$], is(are)
[en = H$$_2$$NCH$$_2$$CH$$_2$$NH$$_2$$]
The complex $$[Pt(NH_3)_2Br_2]$$ is square-planar with the composition $$MA_2B_2$$ (here $$A = NH_3$$ and $$B = Br^-$$).
Square-planar $$MA_2B_2$$ species can exist in two geometrical arrangements:
• cis : the two $$A$$ ligands are adjacent.
• trans : the two $$A$$ ligands are opposite.
Hence the “type of isomerism” referred to in the question is cis-trans (geometrical) isomerism.
We must therefore look for complexes in the options that are capable of showing the same cis-trans geometrical isomerism.
Option A : $$[Pt(en)(SCN)_2]$$
• Coordination number = 4, geometry = square-planar.
• The bidentate ligand $$en$$ occupies two adjacent positions compulsorily (it must be cis).
• The two $$SCN^-$$ ligands are forced into the remaining two adjacent positions, so only one spatial arrangement is possible.
• Therefore no cis-trans isomerism is possible. (The complex can show linkage isomerism through $$S$$ vs $$N$$ binding, but that is a different type.)
⇒ Does not match the required isomerism.
Option B : $$[Zn(NH_3)_2Cl_2]$$
• $$Zn^{2+}$$ with coordination number 4 usually forms a tetrahedral complex.
• A tetrahedral $$MA_2B_2$$ arrangement is symmetric; cis and trans positions are indistinguishable.
• Therefore no geometrical isomerism exists.
⇒ Does not match the required isomerism.
Option C : $$[Pt(NH_3)_2Cl_4]$$
• Coordination number = 6, oxidation state $$+4$$, geometry = octahedral.
• General formula $$MA_2B_4$$ (two $$NH_3$$ and four $$Cl^-$$).
• In an octahedron, two distinct arrangements exist:
- cis : the two $$NH_3$$ ligands are 90° apart.
- trans : the two $$NH_3$$ ligands are 180° apart.
• Thus the complex does show cis-trans geometrical isomerism.
⇒ Matches the required type.
Option D : $$[Cr(en)_2(H_2O)(SO_4)]^{+}$$
• Coordination number = 6, geometry = octahedral.
• Two bidentate $$en$$ ligands occupy four sites; $$H_2O$$ and $$SO_4^{2-}$$ occupy the remaining two sites.
• For the monodentate pair ($$H_2O$$ vs $$SO_4^{2-}$$) we can have:
- cis : $$H_2O$$ adjacent to $$SO_4^{2-}$$.
- trans : $$H_2O$$ opposite $$SO_4^{2-}$$.
• Hence the complex exhibits cis-trans geometrical isomerism; in addition it can be optically active, but that does not affect the present question.
⇒ Matches the required type.
Therefore, the complexes capable of showing the same cis-trans geometrical isomerism as $$[Pt(NH_3)_2Br_2]$$ are:
Option C which is: $$[Pt(NH_3)_2Cl_4]$$
Option D which is: $$[Cr(en)_2(H_2O)(SO_4)]^{+}$$
Answer: Option C and Option D.
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