Salen ligand

Salen ligand
Other names 2,2'-Ethylenebis(nitrilomethylidene)diphenol, N,N'-Ethylenebis(salicylimine)
Identifiers
CAS number	94-93-9 Y
Properties
Molecular formula	C16H16N2O2
Molar mass	268.31
Appearance	yellow solid
Melting point	125-129 °C, 269 K, -75 °F
Solubility in water	organic solvents
Y ligand (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.

Nomenclature

The diphenol H₂salen is the conjugate acid of the ligand that logically is salen^2-. But the terminology is used loosely. As an anionic tetradendate ligand, salen^2- resembles tetradentate ligands including those that are macrocyclic, such as porphyrinate, corrin, bis(dimethylglyoximate), and some Schiff bases.

Preparation

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]

References

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 9780470132340.