Ligand

In coordination chemistry, a ligand ( /lɪgənd/) is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from covalent to ionic. Furthermore, the metal-ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known involving Lewis acidic "ligand."

Metals and metalloids are bound to ligands in virtually all circumstances, although gaseous "naked" metal ions can be generated in high vacuum. Ligands in a complex dictate the reactivity of the central atom, including ligand substitution rates, the reactivity of the ligands themselves, and redox. Ligand selection is a critical consideration in many practical areas, including bioinorganic and medicinal chemistry, homogeneous catalysis, and environmental chemistry.

Ligands are classified in many ways: their charge, their size (bulk), the identity of the coordinating atom(s), and the number of electrons donated to the metal (denticity or hapticity). The size of a ligand is indicated by its cone angle.

Read more about Ligand:  History, Strong Field and Weak Field Ligands, Classification of Ligands As L and X, Common Ligands, Ligand Exchange

Other articles related to "ligand, ligands":

Migratory Insertion - Overview
... See also Ligand#Classification of ligands as L and X In the migratory insertion, a ligand that is viewed as an anion (X) ligand in and a ligand that is viewed as neutral couple, generating a new anionic ... The anion and neutral ligands that react are adjacent ... A new (neutral) ligand can then react with the metal leading to a further insertion ...
Ligand Binding Assay
... In medicine and pharmacology, a ligand binding assay (LBA) is a technique to identify the presence of a molecule and quantify it ... There are numerous types of ligand binding assays, both radioactive and non-radioactive ... As such, ligand binding assays are superset of radiobinding assays, which are the conceptual inverse of radioimmunoassays (RIA) ...
Associative Substitution - Special Ligand Effects
... In special situations, some ligands participate in substitution reactions leading to associative pathways ... These ligands can adopt multiple motifs for binding to the metal, each of which involves a different number of electrons "donated." A classic case is ... Other pi-ligands behave in this way, e.g ...
Stability Constants Of Complexes - Applications
... The ideal ligand binds to the target metal ion and not to others, but this degree of selectivity is very hard to achieve ... The large stability constant of the octadentate ligand ensures that the concentration of free Gd3+ is almost negligible, certainly well below toxicity threshold ... In addition the ligand occupies only 8 of the 9 coordination sites on the gadolinium ion ...
Ligand Exchange
... A Ligand exchange (also ligand substitution) is a type of chemical reaction in which a ligand in a compound is replaced by another ... Another form of ligand exchange is seen in the nucleophilic abstraction reaction ...