Classify the following into homoleptic and heteroleptic complexes?
A.\[{K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]\]
B.\[\left[ {CO{{\left( {N{H_3}} \right)}_5}\left( {C{O_3}} \right)} \right]Cl\]
C.\[{K_2}\left[ {Zn{{\left( {OH} \right)}_4}} \right]\]
D.\[\left[ {Pt{{\left( {N{H_3}} \right)}_2}Cl\left( {N{O_2}} \right)} \right]\]

Hint- We must know that in a complex where only one type of ligand is present is homoleptic complex and in complex where more than one type of ligands are present is a heteroleptic complex.

Complete step by step answer:
We must remember that the ligands can be anions, cations, or neutral molecules. And further we classify Ligands monodentate, bidentate, tridentate and polydentate ligands. In coordination chemistry, the metal coordinated with ligands in the coordination sphere. The Complexes compounds in which all the ligands are bound to the metal center which are identical to each other are known as homoleptic complexes and the complexes in which the metal atoms or ions are linked with more than one kind of ligands are known as heteroleptic complexes.
As we know,
\[{K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]\]and \[{K_2}\left[ {Zn{{\left( {OH} \right)}_4}} \right]\]are homoleptic complex.
In\[{K_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right]\], iron atom coordinated with \[C{N^ - }\]ligands only. Also in\[{K_2}\left[ {Zn{{\left( {OH} \right)}_4}} \right]\], zinc metal coordinated with \[O{H^ - }\]ligands only.
\[\left[ {CO{{\left( {N{H_3}} \right)}_5}\left( {C{O_3}} \right)} \right]Cl\] and\[\;\left[ {Pt{{\left( {N{H_3}} \right)}_2}Cl\left( {N{O_2}} \right)} \right]\] are heteroleptic complex.
In\[\left[ {CO{{\left( {N{H_3}} \right)}_5}\left( {C{O_3}} \right)} \right]Cl\], cobalt metal coordinated with \[N{H_3}\]and \[C{O_3}\]two different ligands. Also in\[\;\left[ {Pt{{\left( {N{H_3}} \right)}_2}Cl\left( {N{O_2}} \right)} \right]\], platinum metal coordinated with \[N{H_3}\]and \[N{O_2}\]ligands.
Therefore, we can conclude that the A and C are homoleptic. Also, B and D are heteroleptic complexes.

Note:We must remember that the metalloids and metals are around ligands in all circumstances, although gaseous "open" metal ions can be generated in a highly vacuum state. The ligands in a complex dictate the reactivity of a central atom also includes ligand substitution rates and also the reactivity of the ligands themselves.
Also we remember that the ligands are classified in different ways including charge, size and the identity of the coordinating atoms. The size of a ligand is indicated by different cone angles.