Question

What are the unidentate ligands with more than one coordinating atom called as?

Answer 1

Hint : The ambidentate ligands are the same as unidentate ligands but the only difference in them is they may have two atoms linking to the central metal atom at a time. Many such unidentate ligands behave as the ambidentate ligands.

Complete Step By Step Answer:
Ligands are the ions that are bonded to neutral metals or central metal ions in a coordination complex. In a coordination complex, the central metal ion acts as Lewis acids and the ligands act as a Lewis base which donates their electron pairs to form bonds with the central metal ion. Ligands have at least one donor atom with an electron pair used to form covalent bonds with the central atom.
Unidentate ligands- the ligands that coordinate through only one atom are called unidentate ligands. Only one of the atoms in unidentate ligand can donate their pair of electrons. Example-${H_2}O,C{N^ - },SC{N^ - }{\text{or }}NC{S^ - },N{H_3}$ etc.
The unidentate ligands with more than one coordinating atom are called ‘Ambidentate ligands’. These ligands have two or more atoms for donating electrons but at a time only one of the atoms will donate its electrons to form a bond with the central metal ion during the complex formation. For example $N{O_2}^ -$ group, it has two donor atoms $N$ and $O$ . But during bonding with the central metal ion only one of them will be linked to the metal ion as $M - ONO$ or $M - N{O_2}$ .
Also $SC{N^ - }$ . Its two donor atoms are $S$ and $N$ , and their linking with the central metal will be either as $M - SCN$ or $M - NCS$ .

Note :
Ligands when interacting with the central metal atom they produce a splitting effect that splits the orbitals into higher and lower energy levels. Their splitting depends upon how strong the ligand is; if the ligands produce a larger splitting then they are called strong field ligands and if they produce smaller splitting then they are called weak field ligands.