Salen ligand

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Salen ligand
Salen structure.svg
Other names
2,2'-Ethylenebis(nitrilomethylidene)diphenol, N,N'-Ethylenebis(salicylimine)
94-93-9 N
Molar mass 268.31
Appearance yellow solid
Melting point 125 °C (257 °F; 398 K)
organic solvents
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Salen is the abbreviation for a popular chelating ligand used in coordination chemistry and homogeneous catalysis. The name salen is a contraction for salicylaldehyde and ethylenediamine. The ligand is a bright yellow micaceous solid that is soluble in polar organic solvents.


The diphenol H2salen is the conjugate acid of the ligand that logically is salen2−. But the terminology is used loosely. As an anionic tetradendate ligand, salen2− resembles tetradentate ligands including those that are macrocyclic, such as porphyrinate, corrin, bis(dimethylglyoximate), and some Schiff bases.


SalenH2 is commercially available. It was first prepared by Pfeiffer.[1] It is often generated in situ followed by the addition of the metal salt, but the ligand is also easily prepared as a pure organic compound by the condensation of ethylenediamine and salicylaldehyde.[2]

Preparation of salen.png


  1. ^ P. Pfeiffer, E. Breith, E. Lübbe, T. Tsumaki (1933). ""Tricyclische orthokondensierte Nebenvalenzringe". Justus Liebig's Annalen der Chemie 503: 84–130. doi:10.1002/jlac.19335030106. 
  2. ^ Harvey Diehl, Clifford C. Hach (1950). "Bis(N,N' - Disalicylalethylenediamine) -μ - Aquodicobalt(II)". Inorg. Synth. Inorganic Syntheses 3: 196–201. doi:10.1002/9780470132340.ch53. ISBN 978-0-470-13234-0. 

See also[edit]