Salen refers to a

tetradentate In chemistry, tetradentate ligands are ligands that bind four donor atoms to a central atom to form a coordination complex. This number of donor atoms that bind is called denticity and is a method of classifying ligands. Tetradentate ligands are ...

C₂-symmetric ligand synthesized from

salicylaldehyde Salicylic aldehyde (2-hydroxybenzaldehyde) is an organic compound with the formula . Along with 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde, it is one of the three isomers of hydroxybenzaldehyde. This colorless oily liquid has a bitter almo ...

(sal) and

ethylenediamine Ethylenediamine (abbreviated as en when a ligand) is the organic compound with the formula C2H4(NH2)2. This colorless liquid with an ammonia-like odor is a basic amine. It is a widely used building block in chemical synthesis, with approximately ...

(en). It may also refer to a class of compounds, which are structurally related to the classical salen ligand, primarily bis-

Schiff bases In organic chemistry, a Schiff base (named after Hugo Schiff) is a compound with the general structure ( = alkyl or aryl, but not hydrogen). They can be considered a sub-class of imines, being either secondary ketimines#Nomenclature and classi ...

. Salen ligands are notable for coordinating a wide range of different metals, which they can often stabilise in various oxidation states. For this reason salen-type compounds are used as

metal deactivator Metal deactivators, or metal deactivating agents (MDA) are fuel additives and oil additives used to stabilize fluids by deactivating (usually by sequestering) metal ions, mostly introduced by the action of naturally occurring acids in the fuel ...

Metal salen complexes A metal salen complex is a coordination compound between a metal cation and a ligand derived from ''N'',''N''′-bis(salicylidene)ethylenediamine, commonly called salen. The classical example is salcomine, the complex with divalent cobalt , usuall ...

also find use as

catalysts Catalysis () is the increase in reaction rate, rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst ...

Synthesis and complexation

H₂salen may be synthesized by the

condensation Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor ...

of ethylenediamine and salicylaldehyde. : Preparation of salen

Complexes of salen with metal cations can often be made in situ, i.e., without isolating the H₂salen.{{cite journal , doi = 10.1039/B307853C , journal = Chem. Soc. Rev. , title = Metal-Salen Schiff base complexes in catalysis: Practical aspects , year = 2004 , author = Pier Giorgio Cozzi, volume = 33 , issue = 7 , pages = 410–421 , pmid=15354222 :H₂salen + M²⁺ → M(salen) + 2 H⁺

References

Organometallic chemistry Schiff bases Tetradentate ligands 2-Hydroxyphenyl compounds

Synthesis and complexation

See also

References