Salen refers to a tetradentateC2-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]
H2salen may be synthesized by the condensation of ethylenediamine and salicylaldehyde.[3]
Salcomine, a complex of salen with cobaltJacobsen's salen-Mn catalyst
Complexes of salen with metal cations may be made without isolating it from the reaction mixture.[4][5] This is possible because the stability constant for the formation of the metal complexes are very high, due to the chelate effect.
The name "salen ligands" is used for tetradentate ligands which have similar structures. For example, in salpn there is a methyl substituent on the bridge. It is used as a metal deactivation additive in fuels.[8] The presence of bulky groups near the coordination site may enhance the catalytic activity of a metal complex and prevent its dimerization. Salen ligands derived from 3,5-di-tert-butylsalicylaldehyde fulfill these roles, and also increase the solubility of the complexes in non-polar solvents like pentane. Chiral "salen" ligands may be created by proper substitution of the diamine backbone, the phenyl ring, or both.[5] An example is the ligand obtained by condensation of the C2-symmetrictrans-1,2-diaminocyclohexane with 3,5-di-tert-butylsalicylaldehyde. Chiral ligands may be used in asymmetric synthesis reactions, such as the Jacobsen epoxidation:[9][10]
A class of tetradentate ligands with the generic name acacen are obtained by the condensation of derivatives of acetylacetone and ethylenediamine.[11] Cobalt complexes [Co(acacen)L2]+, selectively inhibit the activities of histidine-containing proteins through exchange of the axial ligands. These compounds show promise for the inhibition of oncogenesis.[12]
The salan and salalen ligands are similar in structure to salen ligands, but have one or two saturated nitrogen-aryl bonds (amines rather than imines). They tend to be less rigid and more electron rich at the metal center than the corresponding salen complexes.[13][14] Salans can be synthesized by the alkylation of an appropriate amine with a phenolic alkyl halide. The “half-salen” ligands have only one salicylimine group. They are prepared from a salicylaldehyde and a monoamine.[15]
The name “salen” or “salen-type” may be used for other ligands that have similar environment around the chelating site, namely two acidic hydroxyls and two Schiff base (aryl-imine) groups. These include the ligands abbreviated as salph, from the condensation of 1,2-phenylenediamine and salicylaldehyde, and salqu, from the condensation of salicylaldehyde and 2-quinoxalinol.[16]
^Cozzi, Pier Giorgio (2004). "Metal–Salen Schiff base complexes in catalysis: practical aspects". Chem. Soc. Rev. 33 (7): 410–421. doi:10.1039/B307853C. PMID 15354222.
^Shaw, Subrata; White, James D. (11 June 2019). "Asymmetric Catalysis Using Chiral Salen–Metal Complexes: Recent Advances". Chemical Reviews. 119 (16): 9381–9426. doi:10.1021/acs.chemrev.9b00074. PMID 31184109. S2CID 184486101.
^Tsumaki, T. (1938). "Nebenvalenzringverbindungen. IV. Über einige innerkomplexe Kobaltsalze der Oxyaldimine". Bulletin of the Chemical Society of Japan (in German). 13 (2): 252–260. doi:10.1246/bcsj.13.252.
^ abPier Giorgio Cozzi (2004). "Metal-Salen Schiff base complexes in catalysis: Practical aspects". Chem. Soc. Rev. 33 (7): 410–421. doi:10.1039/B307853C. PMID 15354222.
^Appleton, T. G. (1977). "Oxygen Uptake by a Cobalt(II) Complex". J. Chem. Educ.54 (7): 443. doi:10.1021/ed054p443.
^Yamada, Shoichiro (1999). "Advancement in stereochemical aspects of Schiff base metal complexes". Coordination Chemistry Reviews. 190–192: 537–555. doi:10.1016/S0010-8545(99)00099-5.
^Larrow, J. F.; Jacobsen, E. N. (2004). "(R,R)-N,N'-Bis(3,5-Di-tert-Butylsalicylidene)-1,2-Cyclohexanediamino Manganese(III) Chloride, A Highly Enantioselective Epoxidation Catalyst". Organic Syntheses; Collected Volumes, vol. 10, p. 96.
^ abWeber, Birgit; Jäger, Ernst-G. (2009). "Structure and Magnetic Properties of Iron(II/III) Complexes with N 2O2– 2-Coordinating Schiff Base-Like Ligands". Eur. J. Inorg. Chem.: 455. doi:10.1002/ejic.200990003.
^Bajema, Elizabeth A.; Kaleigh F. Roberts; Meade, Thomas J. (2019). "Chapter 11. Cobalt-Schiff Base Complexes:Preclinical Research and Potential Therapeutic Uses". In Sigel, Astrid; Freisinger, Eva; Sigel, Roland K. O.; Carver, Peggy L. (Guest editor) (eds.). Essential Metals in Medicine:Therapeutic Use and Toxicity of Metal Ions in the Clinic. Vol. 19. Berlin: de Gruyter GmbH. pp. 267–301. doi:10.1515/9783110527872-017. ISBN978-3-11-052691-2. PMID 30855112. S2CID 73727460. {{cite book}}: |editor4-first= has generic name (help); |journal= ignored (help)
^Atwood, David A.; Remington, Michael P.; Rutherford, Drew (1996). "Use of the Salan Ligands to Form Bimetallic Aluminum Complexes". Organometallics. 15 (22): 4763. doi:10.1021/om960505r.
^Berkessel, Albrecht; Brandenburg, Marc; Leitterstorf, Eva; Frey, Julia; Lex, Johann; Schäfer, Mathias (2007). "A Practical and Versatile Access to Dihydrosalen (Salalen) Ligands: Highly Enantioselective Titanium. In Situ Catalysts for Asymmetric Epoxidation with Aqueous Hydrogen Peroxide". Adv. Synth. Catal.349 (14–15): 2385. doi:10.1002/adsc.200700221.
^Pang, Xuan; Duan, Ranlong; Li, Xiang; Sun, Zhiqiang; Zhang, Han; Wang, Xianhong; Chen, Xuesi (2014). "Synthesis and characterization of half-salen complexes and their application in the polymerization of lactide and ε-caprolactone". Polymer Chemistry. 5 (23): 6857–6864. doi:10.1039/C4PY00734D.
^Wu, Xianghong, Gorden, A. V. E. (2009). "2-Quinoxalinol Salen Copper Complexes for Oxidation of Aryl Methylenes". Eur. J. Org. Chem.2009 (4): 503–509. doi:10.1002/ejoc.200800928.{{cite journal}}: CS1 maint: multiple names: authors list (link)
May 06, 2024
salen, ligand, been, suggested, that, this, article, merged, into, metal, salen, complex, discuss, proposed, since, december, 2023, salen, refers, tetradentate, symmetric, ligand, synthesized, from, salicylaldehyde, ethylenediamine, also, refer, class, compoun. It has been suggested that this article be merged into Metal salen complex Discuss Proposed since December 2023 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 Y94 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 Y N Infobox references This article is about Salen For Complexes of salen and related ligands see Metal salen complexes Contents 1 Synthesis and properties 2 Related ligands 3 See also 4 ReferencesSynthesis and properties editH2salen may be synthesized by the condensation of ethylenediamine and salicylaldehyde 3 nbsp nbsp Salcomine a complex of salen with cobalt nbsp Jacobsen s salen Mn catalyst Complexes of salen with metal cations may be made without isolating it from the reaction mixture 4 5 This is possible because the stability constant for the formation of the metal complexes are very high due to the chelate effect H2L Mn ML n 2 2 H where L stands for the ligand The pyridine adduct of the cobalt II complex Co salen py salcomine has a square pyramidal structure it can act as a dioxygen carrier by forming a labile octahedral O2 complex 6 7 The name salen ligands is used for tetradentate ligands which have similar structures For example in salpn there is a methyl substituent on the bridge It is used as a metal deactivation additive in fuels 8 The presence of bulky groups near the coordination site may enhance the catalytic activity of a metal complex and prevent its dimerization Salen ligands derived from 3 5 di tert butylsalicylaldehyde fulfill these roles and also increase the solubility of the complexes in non polar solvents like pentane Chiral salen ligands may be created by proper substitution of the diamine backbone the phenyl ring or both 5 An example is the ligand obtained by condensation of the C2 symmetric trans 1 2 diaminocyclohexane with 3 5 di tert butylsalicylaldehyde Chiral ligands may be used in asymmetric synthesis reactions such as the Jacobsen epoxidation 9 10 Related ligands edit nbsp Synthesis and complexation of Jager s ligand 11 A class of tetradentate ligands with the generic name acacen are obtained by the condensation of derivatives of acetylacetone and ethylenediamine 11 Cobalt complexes Co acacen L2 selectively inhibit the activities of histidine containing proteins through exchange of the axial ligands These compounds show promise for the inhibition of oncogenesis 12 The salan and salalen ligands are similar in structure to salen ligands but have one or two saturated nitrogen aryl bonds amines rather than imines They tend to be less rigid and more electron rich at the metal center than the corresponding salen complexes 13 14 Salans can be synthesized by the alkylation of an appropriate amine with a phenolic alkyl halide The half salen ligands have only one salicylimine group They are prepared from a salicylaldehyde and a monoamine 15 The name salen or salen type may be used for other ligands that have similar environment around the chelating site namely two acidic hydroxyls and two Schiff base aryl imine groups These include the ligands abbreviated as salph from the condensation of 1 2 phenylenediamine and salicylaldehyde and salqu from the condensation of salicylaldehyde and 2 quinoxalinol 16 See also editMetal salen complexes Bisthiosemicarbazones a structurally related class of C2 symmetric imine based ligandsReferences edit Cozzi Pier Giorgio 2004 Metal Salen Schiff base complexes in catalysis practical aspects Chem Soc Rev 33 7 410 421 doi 10 1039 B307853C PMID 15354222 Shaw Subrata White James D 11 June 2019 Asymmetric Catalysis Using Chiral Salen Metal Complexes Recent Advances Chemical Reviews 119 16 9381 9426 doi 10 1021 acs chemrev 9b00074 PMID 31184109 S2CID 184486101 Tsumaki T 1938 Nebenvalenzringverbindungen IV Uber einige innerkomplexe Kobaltsalze der Oxyaldimine Bulletin of the Chemical Society of Japan in German 13 2 252 260 doi 10 1246 bcsj 13 252 Diehl Harvey Hach Clifford C 1950 Bis N N Disalicylalethylenediamine m Aquodicobalt II Inorganic Syntheses Vol 3 pp 196 201 doi 10 1002 9780470132340 ch53 ISBN 978 0 470 13234 0 a href Template Cite book html title Template Cite book cite book a journal ignored help a b Pier Giorgio Cozzi 2004 Metal Salen Schiff base complexes in catalysis Practical aspects Chem Soc Rev 33 7 410 421 doi 10 1039 B307853C PMID 15354222 Appleton T G 1977 Oxygen Uptake by a Cobalt II Complex J Chem Educ 54 7 443 doi 10 1021 ed054p443 Yamada Shoichiro 1999 Advancement in stereochemical aspects of Schiff base metal complexes Coordination Chemistry Reviews 190 192 537 555 doi 10 1016 S0010 8545 99 00099 5 Dabelstein W Reglitzky A Schutze A Reders K Automotive Fuels Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a16 719 pub2 ISBN 978 3527306732 a href Template Cite encyclopedia html title Template Cite encyclopedia cite encyclopedia a CS1 maint multiple names authors list link Larrow J F Jacobsen E N 2004 R R N N Bis 3 5 Di tert Butylsalicylidene 1 2 Cyclohexanediamino Manganese III Chloride A Highly Enantioselective Epoxidation Catalyst Organic Syntheses Collected Volumes vol 10 p 96 Yoon TP Jacobsen EN 2003 Privileged Chiral Catalysts Science 299 5613 1691 1693 Bibcode 2003Sci 299 1691Y doi 10 1126 science 1083622 PMID 12637734 S2CID 27416160 a b Weber Birgit Jager Ernst G 2009 Structure and Magnetic Properties of Iron II III Complexes with N2 O2 2 Coordinating Schiff Base Like Ligands Eur J Inorg Chem 455 doi 10 1002 ejic 200990003 Bajema Elizabeth A Kaleigh F Roberts Meade Thomas J 2019 Chapter 11 Cobalt Schiff Base Complexes Preclinical Research and Potential Therapeutic Uses In Sigel Astrid Freisinger Eva Sigel Roland K O Carver Peggy L Guest editor eds Essential Metals in Medicine Therapeutic Use and Toxicity of Metal Ions in the Clinic Vol 19 Berlin de Gruyter GmbH pp 267 301 doi 10 1515 9783110527872 017 ISBN 978 3 11 052691 2 PMID 30855112 S2CID 73727460 a href Template Cite book html title Template Cite book cite book a editor4 first has generic name help journal ignored help Atwood David A Remington Michael P Rutherford Drew 1996 Use of the Salan Ligands to Form Bimetallic Aluminum Complexes Organometallics 15 22 4763 doi 10 1021 om960505r Berkessel Albrecht Brandenburg Marc Leitterstorf Eva Frey Julia Lex Johann Schafer Mathias 2007 A Practical and Versatile Access to Dihydrosalen Salalen Ligands Highly Enantioselective Titanium In Situ Catalysts for Asymmetric Epoxidation with Aqueous Hydrogen Peroxide Adv Synth Catal 349 14 15 2385 doi 10 1002 adsc 200700221 Pang Xuan Duan Ranlong Li Xiang Sun Zhiqiang Zhang Han Wang Xianhong Chen Xuesi 2014 Synthesis and characterization of half salen complexes and their application in the polymerization of lactide and e caprolactone Polymer Chemistry 5 23 6857 6864 doi 10 1039 C4PY00734D Wu Xianghong Gorden A V E 2009 2 Quinoxalinol Salen Copper Complexes for Oxidation of Aryl Methylenes Eur J Org Chem 2009 4 503 509 doi 10 1002 ejoc 200800928 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link Retrieved from https en wikipedia org w index php title Salen ligand amp oldid 1207345507, wikipedia, wiki, book, books, library,
