Salen ligand

Salen ligand

Names
Other names 2,2′-Ethylenebis(nitrilomethylidene)diphenol, N,N′-Ethylenebis(salicylimine)
Identifiers
CAS Number	94-93-9 Y
3D model (Jmol)	Interactive image
ChemSpider	10484366 N
ECHA InfoCard	100.002.161
UNII	M122L9EGR6 N
InChI InChI=1S/C16H16N2O2/c19-15-7-3-1-5-13(15)11-17-9-10-18-12-14-6-2-4-8-16(14)20/h1-8,11-12,19-20H,9-10H2/b17-11+,18-12+ Key: VEUMANXWQDHAJV-JYFOCSDGSA-N
SMILES C1=CC=C(C(=C1)/C=N/CC/N=C/C2=CC=CC=C2O)O
Properties
Chemical formula	C16H16N2O2
Molar mass	268.31
Appearance	yellow solid
Melting point	125 to 129 °C (257 to 264 °F; 398 to 402 K)
Solubility in water	organic solvents
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
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.

H₂salen is commercially available. It was first prepared by Pfeiffer. 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.

Related to salen ligands but based on non-aromatic precursors are the acacen ligands. These dianionic tetradentate ligands are often derived from the condensation of ketoaldehyde equivalents and diamines. The name acacen derives from the abbreviation for acetylacetone and ethylenediamine.