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Which of the following coordination compounds would exhibit optical isomerism
A
Diamminedichloroplatinum (II)
B
Trans-dicyanobis (ethylenediamine) chromium (III) chloride
C
Tris–(ethylenediamine) cobalt (III) bromide
D
Pentaamminenitrocobalt (III) iodide
Detailed Solution
A complex shows optical isomerism if it is chiral, i.e. it has no plane or centre of symmetry, so it is not superimposable on its mirror image.
$[Pt(NH_3)_2Cl_2]$ is square planar. A square planar complex has its molecular plane as a plane of symmetry, so it is optically inactive (it shows only geometrical isomerism).
trans-$[Cr(CN)_2(en)_2]Cl$: in the trans form the two $CN^-$ groups are opposite each other and the two en rings lie in one plane, which is a plane of symmetry. So it is optically inactive (only the cis form is chiral).
$[Co(en)_3]Br_3$: three bidentate en ligands wrap around Co like the blades of a propeller. The arrangement has no plane of symmetry and exists as two non-superimposable mirror images (d and l forms). So it shows optical isomerism.
$[Co(NH_3)_5(NO_2)]I_2$ is of the $MA_5B$ type and has planes of symmetry, so it is optically inactive (it shows linkage isomerism).
So tris(ethylenediamine)cobalt(III) bromide exhibits optical isomerism.
$[Pt(NH_3)_2Cl_2]$ is square planar. A square planar complex has its molecular plane as a plane of symmetry, so it is optically inactive (it shows only geometrical isomerism).
trans-$[Cr(CN)_2(en)_2]Cl$: in the trans form the two $CN^-$ groups are opposite each other and the two en rings lie in one plane, which is a plane of symmetry. So it is optically inactive (only the cis form is chiral).
$[Co(en)_3]Br_3$: three bidentate en ligands wrap around Co like the blades of a propeller. The arrangement has no plane of symmetry and exists as two non-superimposable mirror images (d and l forms). So it shows optical isomerism.
$[Co(NH_3)_5(NO_2)]I_2$ is of the $MA_5B$ type and has planes of symmetry, so it is optically inactive (it shows linkage isomerism).
So tris(ethylenediamine)cobalt(III) bromide exhibits optical isomerism.