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In chemistry, linkage isomerism or ambidentate isomerism is a form of structural isomerism in which certain coordination compounds have the same composition but differ in which atom of the ligand is bonded to the metal. Typical ligands that give rise to linkage isomers are: cyanide, CN − – isocyanide, NC −; cyanate, OCN − – isocyanate ...
A classic bidentate ligand is ethylenediamine, which is derived by the linking of two ammonia groups with an ethylene (−CH 2 CH 2 −) linker. A classic example of a polydentate ligand is the hexadentate chelating agent EDTA , which is able to bond through six sites, completely surrounding some metals.
In coordination chemistry, denticity (from Latin dentis 'tooth') refers to the number of donor groups in a given ligand that bind to the central metal atom in a coordination complex. [1] [2] In many cases, only one atom in the ligand binds to the metal, so the denticity equals one, and the ligand is said to be unidentate or monodentate.
In DNA-ligand binding studies, the ligand can be a small molecule, ion, [1] or protein [2] which binds to the DNA double helix. The relationship between ligand and binding partner is a function of charge, hydrophobicity, and molecular structure. Binding occurs by intermolecular forces, such as ionic bonds, hydrogen bonds and Van der Waals forces.
Doubly deprotonated cysteine is often an N,S-bidentate ligand. Using kinetically inert metal ions, complexes containing monodentate amino acids have been characterized. These complexes exist in either the N or the O linkage isomers. It can be assumed that such monodentate complexes exist transiently for many kinetically labile metal ions (e.g ...
Thiosulfate is a potent ligand for soft metal ions. A typical complex is [Pd(S 2 O 3) 2 (ethylenediamine)] 2−, which features a pair of S-bonded thiosulfate ligands. Simple aquo and ammine complexes are also known. [2] Three binding modes are common: monodentate (κ 1-), O,S-bidentate (κ 2-), and bridging (μ-).
Even though the ligand is written as MNO 3, the oxygen atoms are invariably coordinated. Thus, monodentate nitrate is illustrated by [Co(NH 3) 5 NO 3] 2+, which could also be written as [Co(NH 3) 5 ONO 2] 2+. Homoleptic metal nitrate complexes generally have O,O'-bidentate nitrate ligands.
This ligand–metal–ligand geometric parameter is used to classify chelating ligands, including those in organometallic complexes. It is most often discussed in terms of catalysis , as changes in bite angle can affect not just the activity and selectivity of a catalytic reaction but even allow alternative reaction pathways to become accessible.