Ligand
Definition and meaning of Ligand in chemistry.
A ligand is a molecule or ion that binds to a central metal atom or ion by donating electron pairs to form coordinate covalent bonds. Ligands are Lewis bases that form the structural components of coordination complexes.
In more detail
When a ligand donates its electron pair to a metal atom (which acts as a Lewis acid), they form a coordinate covalent bond. Ligands can be monodentate, bonding through a single donor atom, or polydentate, bonding simultaneously through multiple atoms on the same molecule. The identity, number, and spatial arrangement of ligands determine the geometry, stability, color, and chemical properties of the resulting coordination complex. Ligands play critical roles in biochemistry, transition metal catalysis, and materials science.
Key facts
| Field | Inorganic Chemistry |
|---|---|
| Bonding type | Coordinate covalent bond |
| Common examples | H2O, NH3, Cl-, CN- |
| Classification | Monodentate (one donor atom) or polydentate (multiple donor atoms) |
In the hexaaquairon(III) complex [Fe(H2O)6]3+, six water molecules serve as monodentate ligands. Each water molecule donates an electron pair from its oxygen atom to form a coordinate covalent bond with the central iron(III) ion.
Frequently asked questions
Can water be a ligand?
Yes, water (H2O) is a common neutral ligand that donates an electron pair from its oxygen atom to metal centers, forming aqua complexes like [Fe(H2O)6]3+.
What is the difference between monodentate and polydentate ligands?
Monodentate ligands donate electrons from a single atom, while polydentate ligands have multiple donor atoms that bond to the same metal center, generally creating more stable complexes.