28.2.2—Terms: ligand as a species that contains
- Syllabus
- 9701–2028–2029
- Objective
- 28.2.2
- Level
- A2
A ligand donates a lone pair to a central metal through a coordinate bond
A ligand is an ion or molecule with at least one lone pair that forms a dative covalent bond to a metal atom or ion. The donor atom is the atom directly attached to the metal.
Water and ammonia donate oxygen or nitrogen lone pairs; chloride and cyanide donate anionic lone pairs. The ligand’s charge contributes to the complex charge but does not change the donor definition.
In [Co(NH₃)₆]³⁺, each NH₃ donates one nitrogen lone pair and the six ligands are neutral.
A ligand is not any surrounding ion, and a coordinate bond is not formed by the metal donating both electrons.
ConceptA-Level CAIE Chemistry A2