Edexcel A Level Chemistry:复习笔记6.2.4 Ligands

Monodentate ligands


  • Monodentate ligands can form only one dative bond to the central metal ion
  • This is because they have a single lone pair of electrons to form a dative bond with the metal ion
  • Examples of monodentate ligands are:
    • Water (H2O) molecules
    • Ammonia (NH3) molecules
    • Chloride (Cl–) ions
    • Cyanide (CN–) ions


Examples of complexes with monodentate ligands

Bidentate & Multidentate Ligands

Bidentate Ligands

  • Bidentate ligands can each form two dative bonds to the central metal ion
  • This is because each ligand contains two atoms with lone pairs of electrons
  • Examples of bidentate ligands are:
    • 1,2-diaminoethane (H2NCH2CH2NH2) which is also written as ‘en’
    • Ethanedioate ion (C2O42- ) which is sometimes written as ‘ox’


Examples of complexes with bidentate ligands

Multidentate Ligands

  • Some ligands contain more than two atoms with lone pairs of electrons
  • These ligands can form more than two dative bonds to the and are said to be multidentate ligands
  • An example of a multidentate ligand is EDTA4-, which is a hexadentate ligand as it forms 6 dative covalent bonds to the central metal ion


Example of a polydentate ligand complex