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Which of the following will give a pair of enantiomorphs?
(en $= NH_2CH_2CH_2NH_2$)
(en $= NH_2CH_2CH_2NH_2$)
A
$[Cr(NH_3)_6][Co(CN)_6]$
B
$[Co(en)_2Cl_2]Cl$
C
$[Pt(NH_3)_4][PtCl_6]$
D
$[Co(NH_3)_4Cl_2]NO_2$
Detailed Solution
Non-superimposable mirror images are called optical isomers and may be described as chiral. They are also called enantiomers (enantiomorphs) and rotate plane polarised light in opposite directions.
$[Co(en)_2Cl_2]^+$ is an octahedral complex with two bidentate en ligands and two chloride ligands. It exists as cis and trans geometrical isomers.
The trans isomer has a plane of symmetry and is optically inactive.
The cis isomer has no plane of symmetry; its mirror image cannot be superimposed on it, so it exists as a pair of enantiomers (d and l forms).
$[Cr(NH_3)_6][Co(CN)_6]$ and $[Pt(NH_3)_4][PtCl_6]$ show coordination isomerism, not optical isomerism.
$[Co(NH_3)_4Cl_2]NO_2$ shows geometrical and ionisation isomerism; with only monodentate ligands both its forms have planes of symmetry.
So the complex that gives a pair of enantiomorphs is $[Co(en)_2Cl_2]Cl$.
$[Co(en)_2Cl_2]^+$ is an octahedral complex with two bidentate en ligands and two chloride ligands. It exists as cis and trans geometrical isomers.
The trans isomer has a plane of symmetry and is optically inactive.
The cis isomer has no plane of symmetry; its mirror image cannot be superimposed on it, so it exists as a pair of enantiomers (d and l forms).
$[Cr(NH_3)_6][Co(CN)_6]$ and $[Pt(NH_3)_4][PtCl_6]$ show coordination isomerism, not optical isomerism.
$[Co(NH_3)_4Cl_2]NO_2$ shows geometrical and ionisation isomerism; with only monodentate ligands both its forms have planes of symmetry.
So the complex that gives a pair of enantiomorphs is $[Co(en)_2Cl_2]Cl$.