Salen ligand

Salen refers to a tetradentate C₂-symmetric ligand synthesized from salicylaldehyde (sal) and ethylenediamine (en). It may also refer to a class of compounds, which are structurally related to the classical salen ligand, primarily bis-Schiff bases. Salen ligands are notable for coordinating a wide range of different metals, which they can often stabilise in various oxidation states.^[1] For this reason salen-type compounds are used as metal deactivators. Metal salen complexes also find use as catalysts.^[2]

Salen ligand

Names
Other names 2,2′-Ethylenebis(nitrilomethylidene)diphenol, N,N′-Ethylenebis(salicylimine)
Identifiers
CAS Number	129409-01-4 Y 94-93-9 (non-specific) Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL594100 Y
ChemSpider	10484366 Y
ECHA InfoCard	100.002.161
EC Number	202-376-3
PubChem CID	26518
UNII	M122L9EGR6 Y
CompTox Dashboard (EPA)	DTXSID5059113
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	268.32
Melting point	126 °C (259 °F; 399 K)
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

This article is about Salen. For Complexes of salen and related ligands, see Metal salen complexes.

Synthesis and complexation

Main article: Metal salen complexes

H₂salen may be synthesized by the condensation of ethylenediamine and salicylaldehyde.^[3]

Salcomine, a complex of salen with cobalt

Jacobsen's salen-Mn catalyst

Complexes of salen with metal cations can often be made in situ, i.e., without isolating the H₂salen.^[4][5]

H₂salen + M²⁺ → M(salen) + 2 H⁺

See also

• Bisthiosemicarbazones, a structurally related class of C₂-symmetric imine based ligands