Question

The stabilization of coordination compounds due to chelation is called the chelate effect. Which of the following is the most stable complex species?
a.) \[\left[ {Fe{{\left( {CO} \right)}_5}} \right]\]
b.) \[{\left[ {Fe{{\left( {CN} \right)}_6}} \right]^{3 - }}\]
c.) \[{\left[ {Fe{{\left( {{C_2}{O_4}} \right)}_3}} \right]^{3 - }}\]
d.) \[{\left[ {Fe{{\left( {{H_2}O} \right)}_6}} \right]^{3 + }}\]

Answer 1

Hint: The process of chelation (formation of a cycle by formation of links between the metal ion and ligand) stabilizes a coordination compound. Among all the coordinate compounds given to us only \[{\left[ {Fe{{\left( {{C_2}{O_4}} \right)}_3}} \right]^{3 - }}\] is formed by chelation, so it is more stable than the others.

Complete step by step answer:
Let’s start by discussing Chelation
Chelation – It is the bonding of metal ions to ions and molecules. Chelation is the formation of two or more separate coordinate bonds (when an atom donates two electrons to another atom) between a ligand and a single central metal ion. They are mostly organic in origin but some synthetic chelates also present.
Most important is that the process of chelation (formation of a cycle by formation of links between the metal ion and ligand) stabilizes a coordination compound. The molecule that forms coordinate bonds with the metal ion is called a ligand.
We are given the following compounds in the problem
 \[\left[ {Fe{{\left( {CO} \right)}_5}} \right]\]
 \[{\left[ {Fe{{\left( {CN} \right)}_6}} \right]^{3 - }}\]
 \[{\left[ {Fe{{\left( {{C_2}{O_4}} \right)}_3}} \right]^{3 - }}\]
 \[{\left[ {Fe{{\left( {{H_2}O} \right)}_6}} \right]^{3 + }}\]
Among the given coordinate compounds only \[{\left[ {Fe{{\left( {{C_2}{O_4}} \right)}_3}} \right]^{3 - }}\] is a coordination compound which is formed by the process of chelation where the formation of a cyclic compound provides it more stability than the other three coordinate compounds which are not formed by the process of chelation.
In \[{\left[ {Fe{{\left( {{C_2}{O_4}} \right)}_3}} \right]^{3 - }}\] , three oxalate molecules \[\left( {{C_2}{O_4}} \right)\] act as a chelating ligand and \[F{e^{ + 3}}\] is the central metal ion.
So, the correct answer is “Option C”.

Note: In the solution, we discussed the process of chelation. Chelation finds application is providing supplements to weak patients. It is also used in chelation therapy to remove toxic metals from the body and in water treatment to remove metals and to enhance the power of fertilizers.