28.2.3—Terms
- Syllabus
- 9701–2028–2029
- Objective
- 28.2.3
- Level
- A2
Dentate terminology counts how many donor atoms one ligand uses
A monodentate ligand binds through one donor atom, a bidentate ligand through two, and a polydentate ligand through several donor atoms.
H₂O, NH₃, Cl⁻ and CN⁻ are monodentate; en and ethanedioate are bidentate; EDTA⁴⁻ is polydentate. Denticity affects coordination number and chelate stability.
One en ligand occupies two coordination sites, so three en ligands can surround a metal in an octahedral complex.
Denticity is not the same as the ligand’s charge or the number of ligands written in the formula.
ConceptA-Level CAIE Chemistry A2