Question

Which is the pair of ambulant ligands?
A. $C{N^ - }$ , $N{O_2}^ - $
B. $N{O_3}^ - $ , SCN
C. ${N_3}^ - $ , $N{O_2}^ - $
D. $NC{S^ - }$ , ${C_2}{O_4}^{2 - }$

Answer 1

Hint: An ambulant ligand is one which has two donor sites but can ligate or coordinate using only one donor site at a given instant but not using both donor sites. $C{N^ - }$ , $N{O_2}^ - $ , $NC{S^ - }$ etc. are the examples of ambulant ligands.

Complete step by step answer:
A ligand is an ion or molecule, which donates a pair of electrons to the central metal atom or ion to form a coordination complex. Ambulant ligand is a type of ligand which has the ability to bind to the central atom via the atoms of two different elements.
Example: In $N{O_2}^ - $ , it can bind to the central metal or ion at either the nitrogen or oxygen atom. So, $N{O_2}^ - $ is an ambulant ligand.
 $C{N^ - }$ is also an ambulant ligand as it can ligate through either the C center or N center but not using both centers at a time.
Thiocyanate ion (SCN) can bind to the central metal atom or ion through either nitrogen or Sulphur atoms. So, it is an ambulant ligand.
 $NC{S^ - }$ is an ambulant ligand because it can bond to a coordination center through Nitrogen as well as Sulphur.
 $N{O_3}^ - $ is not an ambulant ligand
If the bonding between the ligand and the coordination center is through two donor atoms, it is referred to as a bidentate Oxalate ion $({C_2}{O_4}^{2 - })$ is a bidentate as it can bond through two atoms to the central atom in a coordination compound.
Nitrogen ion $({N_3}^ - )$ is also not an ambulant ligand.

Therefore, the correct answer is option (A).

Note: All ambulant ligands are monodentate but all monodentate ligands are not ambulant. When the central atom and ligand are bound together through a single donor atom, the ligand is said to be unidentate. Some common unidentate are $C{l^ - }$ , ${H_2}O$ etc.