Question

Which of the following species is not expected to be a ligand?
(a) NO
(b) $NH_4^+$
(c) NH₂CH₂CH₂NH₂
(d) CO

Answer 1

Answer:

NH4+

Explanation:

In coordination chemistry, a ligand is defined as an ion or a molecule of a functional group that binds itself to a central metal atom to form a coordination complex. The bonding with the metal usually involves a formal donation of one or more of the ligand's electron pairs.

For example -H20 and NH3 are the examples of a neutral monodentate ligands. When H20 is a ligand, the oxygen is donor atom binding to the metal. whereas when NH3 is a ligand, nitrogen is the donor atom binding to the metal.

The dative bond in NH4(+) is thought to be of as the N losing one of the electrons in its lone pair to the H+, thereby making it neutral and N as positively charged. Thus, the NH4+ Ion do not act as ligand because nitrogen atom has no lone pair of  electrons that it can donate to metal atom.