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The existence of two different coloured complexes with the composition of $[Co(NH_3)_4Cl_2]^+$ is due to
A
Ionization isomerism
B
Linkage isomerism
C
Geometrical isomerism
D
Coordination isomerism
Detailed Solution
$[Co(NH_3)_4Cl_2]^+$ is an octahedral complex of the type $[MA_4B_2]$.
The two $Cl^-$ ligands can occupy adjacent positions ($90^\circ$ apart, cis isomer) or opposite positions ($180^\circ$ apart, trans isomer).
These are geometrical isomers; the cis form is violet and the trans form is green.
Ionisation isomerism needs exchange of a ligand with a counter ion, linkage isomerism needs an ambidentate ligand, and coordination isomerism needs both cation and anion to be complexes; none applies to this single complex ion.
Hence the two coloured forms are due to geometrical isomerism.
The two $Cl^-$ ligands can occupy adjacent positions ($90^\circ$ apart, cis isomer) or opposite positions ($180^\circ$ apart, trans isomer).
These are geometrical isomers; the cis form is violet and the trans form is green.
Ionisation isomerism needs exchange of a ligand with a counter ion, linkage isomerism needs an ambidentate ligand, and coordination isomerism needs both cation and anion to be complexes; none applies to this single complex ion.
Hence the two coloured forms are due to geometrical isomerism.