Question

Which of the following ligands is called chelating ligand?
A.) Ethane – 1,2 diamine
B.) Oxalate
C.) Glycinate
D.) All are chelating ligands.

Answer 1

Hint: The term ligand comes from the Latin word ligare, which means to bind. It was first used by Alfred Stock in 1916 in relation to silicon chemistry.

Complete step by step answer:
Let us first understand what a ligand is.
In simple words, ligands are ions or neutral molecules that bond a central metal atom or ion. Ligands act as Lewis bases (electron pair donors), and the central atom acts as a Lewis acid (electron pair acceptor). Ligands can be anions, cations or neutral molecules.

A ligand and transition metal combinely constitutes complex compounds or coordination compounds. Complex compounds have different geometry depending on the coordination number and hybridization.

Now, considering the given question.
Let us understand about chelating ligands.
Chelating ligands are molecules that can form several bonds to a single metal ion; they are also called multidentate ligands. Simple (and common) examples include ethylenediamine, and oxalate.

Let us discuss the given options.
Oxalate is often encountered as a bidentate, chelating ligand, such as in potassium ferrioxalate. Ethane-1,2 -diamine is a bidentate chelating ligand for coordination compounds, with the two nitrogen atoms donating their lone pairs of electrons. Glycine functions as a bidentate ligand for many metal ions. As a bifunctional molecule, glycine reacts with many reagents. These can be classified into N-centered and carboxylate-center reactions.
From the above information, we can say that Ethane-1,2diamine , Glycinate and Oxalate are all chelating ligands. Therefore, option D is the required answer.

Note: Non-chelating ligands are ligands that bond to just one site, such as chloride, cyanide and water, for example. Citric, malic, lactic and tartaric acids are certain amino acids that are naturally occurring chelating agents.