Chemistry Definition of Ligand

Chemistry Definition of Ligand A ligand is  an atom, ion, or molecule that donates or shares one or more of its electrons through a covalent bond with a central atom or ion. It is a complexing group in coordination chemistry that stabilizes the central atom and determines its reactivity. Ligand Examples Monodentate ligands have one atom that can bind to a central atom or ion. Water (H2O) and ammonia (NH3) are examples of neutral monodentate ligands. A polydentate ligand has more than one donor site. Bidentate ligands have two donor sites. Tridentate ligands have three binding sites. ​1,4,7-triazaheptane (diethylenetriamine) is an example of a tridentate ligand.  Tetradentate ligands have four binding atoms. A complex with a polydentate ligand is called a chelate. An ambidentate ligand is a  monodentate ligand that can bind in two possible places. For example,  The thiocyanate ion, SCN-, can bind to the central metal at either the sulfur or the nitrogen.