Samarium(II) iodide is an inorganic compound with the formula SmI2. When employed as a solution for organic synthesis, it is known as Kagan's reagent. SmI2 is a green solid and forms a dark blue solution in THF.[1] It is a strong one-electron reducing agent that is used in organic synthesis.
In solid samarium(II) iodide, the metal centers are seven-coordinate with a face-capped octahedral geometry.[2]
Structure of the samarium(II) iodide-tetrahydrofuran complex
In its ether adducts, samarium remains heptacoordinate with five ether and two terminal iodide ligands.[3]
Preparationedit
Samarium iodide is easily prepared in nearly quantitative yields from samarium metal and either diiodomethane or 1,2-diiodoethane.[4] When prepared in this way, its solutions is most often used without purification of the inorganic reagent.
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Solid, solvent-free SmI2 forms by high temperature decomposition of samarium(III) iodide (SmI3).[5][6][7]
Reactionsedit
Samarium(II) iodide is a powerful reducing agent – for example it rapidly reduces water to hydrogen.[2] It is available commercially as a dark blue 0.1 M solution in THF. Although used typically in superstoichiometric amounts, catalytic applications have been described.[8]
Typical reaction conditions use SmI2 in THF in the presence of catalytic NiI2.
Esters react similarly (adding two R groups), but aldehydes give by-products. The reaction is convenient in that it is often very rapid (5 minutes or less in the cold). Although samarium(II) iodide is considered a powerful single-electron reducing agent, it does display remarkable chemoselectivity among functional groups. For example, sulfones and sulfoxides can be reduced to the corresponding sulfide in the presence of a variety of carbonyl-containing functionalities (such as esters, ketones, amides, aldehydes, etc.). This is presumably due to the considerably slower reaction with carbonyls as compared to sulfones and sulfoxides. Furthermore, hydrodehalogenation of halogenated hydrocarbons to the corresponding hydrocarbon compound can be achieved using samarium(II) iodide. Also, it can be monitored by the color change that occurs as the dark blue color of SmI2 in THF discharges to a light yellow once the reaction has occurred. The picture shows the dark colour disappearing immediately upon contact with the Barbier reaction mixture.
Work-up is with dilute hydrochloric acid, and the samarium is removed as aqueous Sm3+.
Carbonyl compounds can also be coupled with simple alkenes to form five, six or eight membered rings.[10]
Tosyl groups can be removed from N-tosylamides almost instantaneously, using SmI2 in conjunction with distilled water and an amine base. The reaction is even effective for deprotection of sensitive substrates such as aziridines:[11]
Removal of a tosyl group from an N-tosylamide using SmI2
In the Markó-Lam deoxygenation, an alcohol could be almost instantaneously deoxygenated by reducing their toluate ester in presence of SmI2.
Markó-Lam deoxygenation using SmI2
The applications of SmI2 have been reviewed.[12][13][14] The book Organic Synthesis Using Samarium Diiodide, published in 2009, gives a detailed overview of reactions mediated by SmI2.[15]
^William J. Evans; Tammy S. Gummersheimer & Joseph W. Ziller (1995). "Coordination Chemistry of Samarium Diiodide with Ethers Including the Crystal Structure of Tetrahydrofuran-Solvated Samarium Diiodide, SmI2(THF)5". J. Am. Chem. Soc.117 (35): 8999–9002. doi:10.1021/ja00140a016.
^P. Girard, J. L. Namy and H. B. Kagan (1980). "Divalent Lanthanide Derivatives in Organic Synthesis. 1. Mild Preparation of SmI2 and YbI2 and Their Use as Reducing or Coupling Agents". J. Am. Chem. Soc.102 (8): 2693–2698. doi:10.1021/ja00528a029.
^G. Jantsch, N. Skalla: "Zur Kenntnis der Halogenide der seltenen Erden. IV. – Über Samarium(II)jodid und den thermischen Abbau des Samarium(III)jodids", Zeitschrift für Allgemeine und Anorganische Chemie, 1930, 193, 391–405; doi:10.1002/zaac.19301930132.
^G. Jantsch: "Thermischer Abbau von seltenen Erd(III)halogeniden", Die Naturwissenschaften, 1930, 18 (7), 155–155; doi:10.1007/BF01501667.
^Huang, Huan-Ming; McDouall, Joseph J. W.; Procter, David J. (2019). "SmI2-catalysed cyclization cascades by radical relay". Nature Catalysis. 2 (3): 211–218. doi:10.1038/s41929-018-0219-x. S2CID 104423773.
^Machrouhi, Fouzia; Hamann, Béatrice; Namy, Jean-Louis; Kagan, Henri B. (1996). "Improved Reactivity of Diiodosamarium by Catalysis with Transition Metal Salts". Synlett. 1996 (7): 633–634. doi:10.1055/s-1996-5547. S2CID 196761752.
^Molander, G. A.; McKiie, J. A. (1992). "Samarium(II) iodide-induced reductive cyclization of unactivated olefinic ketones. Sequential radical cyclization/intermolecular nucleophilic addition and substitution reactions". J. Org. Chem.57 (11): 3132–3139. doi:10.1021/jo00037a033.
^Ankner, Tobias; Göran Hilmersson (2009). "Instantaneous Deprotection of Tosylamides and Esters with SmI2/Amine/Water". Organic Letters. 11 (3). American Chemical Society: 503–506. doi:10.1021/ol802243d. PMID 19123840.
^Patrick G. Steel (2001). "Recent developments in lanthanide mediated organic synthesis". J. Chem. Soc., Perkin Trans. 1 (21): 2727–2751. doi:10.1039/a908189e.
^Molander, G. A.; Harris, C. R. (1996). "Sequencing Reactions with Samarium(II) Iodide". Chem. Rev.96 (1): 307–338. doi:10.1021/cr950019y. PMID 11848755.
^K. C. Nicolaou; Shelby P. Ellery; Jason S. Chen (2009). "Samarium Diiodide Mediated Reactions in Total Synthesis". Angew. Chem. Int. Ed.48 (39): 7140–7165. doi:10.1002/anie.200902151. PMC2771673. PMID 19714695.
^Procter, David J.; Flowers,II, Robert A.; Skydstrup, Troels (2009). Organic Synthesis Using Samarium Diiodide. Royal Society of Chemistry. ISBN978-1-84755-110-8.
April 12, 2024
samarium, iodide, inorganic, compound, with, formula, smi2, when, employed, solution, organic, synthesis, known, kagan, reagent, smi2, green, solid, forms, dark, blue, solution, strong, electron, reducing, agent, that, used, organic, synthesis, namesiupac, nam. Samarium II iodide is an inorganic compound with the formula SmI2 When employed as a solution for organic synthesis it is known as Kagan s reagent SmI2 is a green solid and forms a dark blue solution in THF 1 It is a strong one electron reducing agent that is used in organic synthesis Samarium II iodide NamesIUPAC name samarium II iodideOther names samarium diiodideIdentifiersCAS Number 32248 43 4 Y3D model JSmol Interactive imageChemSpider 125002 YPubChem CID 141689UNII L15T8U41LC YCompTox Dashboard EPA DTXSID80893790InChI InChI 1S 2HI Sm h2 1H q 2 p 2 YKey UAWABSHMGXMCRK UHFFFAOYSA L YInChI 1 2HI Sm h2 1H q 2 p 2Key UAWABSHMGXMCRK NUQVWONBADSMILES I Sm IPropertiesChemical formula SmI2Molar mass 404 16 g molAppearance green solidMelting point 520 C 968 F 793 K HazardsFlash point Non flammableRelated compoundsOther anions Samarium II chlorideSamarium II bromideOther cations Samarium III iodideEuropium II iodideExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa Y verify what is Y N Infobox references Samarium II iodide Contents 1 Structure 2 Preparation 3 Reactions 3 1 Organic chemistry 4 ReferencesStructure editIn solid samarium II iodide the metal centers are seven coordinate with a face capped octahedral geometry 2 nbsp Structure of the samarium II iodide tetrahydrofuran complexIn its ether adducts samarium remains heptacoordinate with five ether and two terminal iodide ligands 3 Preparation editSamarium iodide is easily prepared in nearly quantitative yields from samarium metal and either diiodomethane or 1 2 diiodoethane 4 When prepared in this way its solutions is most often used without purification of the inorganic reagent Sm ICH2I THFSmI2 0 5H2C CH2Sm I CH2 2I THFSmI2 H2C CH2 displaystyle begin array cl ce Sm ICH2I gt ce THF SmI2 0 5 ce H2C CH2 ce Sm I CH2 2I gt ce THF SmI2 H2C CH2 end array nbsp Solid solvent free SmI2 forms by high temperature decomposition of samarium III iodide SmI3 5 6 7 Reactions editSamarium II iodide is a powerful reducing agent for example it rapidly reduces water to hydrogen 2 It is available commercially as a dark blue 0 1 M solution in THF Although used typically in superstoichiometric amounts catalytic applications have been described 8 Organic chemistry edit Main article Reductions with samarium II iodide Samarium II iodide is a reagent for carbon carbon bond formation for example in a Barbier reaction similar to the Grignard reaction between a ketone and an alkyl iodide to form a tertiary alcohol 9 R1I R2COR3 R1R2C OH R3 nbsp Barbier reaction using SmI2Typical reaction conditions use SmI2 in THF in the presence of catalytic NiI2 Esters react similarly adding two R groups but aldehydes give by products The reaction is convenient in that it is often very rapid 5 minutes or less in the cold Although samarium II iodide is considered a powerful single electron reducing agent it does display remarkable chemoselectivity among functional groups For example sulfones and sulfoxides can be reduced to the corresponding sulfide in the presence of a variety of carbonyl containing functionalities such as esters ketones amides aldehydes etc This is presumably due to the considerably slower reaction with carbonyls as compared to sulfones and sulfoxides Furthermore hydrodehalogenation of halogenated hydrocarbons to the corresponding hydrocarbon compound can be achieved using samarium II iodide Also it can be monitored by the color change that occurs as the dark blue color of SmI2 in THF discharges to a light yellow once the reaction has occurred The picture shows the dark colour disappearing immediately upon contact with the Barbier reaction mixture Work up is with dilute hydrochloric acid and the samarium is removed as aqueous Sm3 Carbonyl compounds can also be coupled with simple alkenes to form five six or eight membered rings 10 Tosyl groups can be removed from N tosylamides almost instantaneously using SmI2 in conjunction with distilled water and an amine base The reaction is even effective for deprotection of sensitive substrates such as aziridines 11 nbsp Removal of a tosyl group from an N tosylamide using SmI2In the Marko Lam deoxygenation an alcohol could be almost instantaneously deoxygenated by reducing their toluate ester in presence of SmI2 nbsp Marko Lam deoxygenation using SmI2The applications of SmI2 have been reviewed 12 13 14 The book Organic Synthesis Using Samarium Diiodide published in 2009 gives a detailed overview of reactions mediated by SmI2 15 References edit https www sigmaaldrich com GB en sds aldrich 347116 userType anonymous a b Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann ISBN 978 0 08 037941 8 William J Evans Tammy S Gummersheimer amp Joseph W Ziller 1995 Coordination Chemistry of Samarium Diiodide with Ethers Including the Crystal Structure of Tetrahydrofuran Solvated Samarium Diiodide SmI2 THF 5 J Am Chem Soc 117 35 8999 9002 doi 10 1021 ja00140a016 P Girard J L Namy and H B Kagan 1980 Divalent Lanthanide Derivatives in Organic Synthesis 1 Mild Preparation of SmI2 and YbI2 and Their Use as Reducing or Coupling Agents J Am Chem Soc 102 8 2693 2698 doi 10 1021 ja00528a029 G Jantsch N Skalla Zur Kenntnis der Halogenide der seltenen Erden IV Uber Samarium II jodid und den thermischen Abbau des Samarium III jodids Zeitschrift fur Allgemeine und Anorganische Chemie 1930 193 391 405 doi 10 1002 zaac 19301930132 G Jantsch Thermischer Abbau von seltenen Erd III halogeniden Die Naturwissenschaften 1930 18 7 155 155 doi 10 1007 BF01501667 Gmelins Handbuch der anorganischen Chemie System Nr 39 Band C 6 p 192 194 Huang Huan Ming McDouall Joseph J W Procter David J 2019 SmI2 catalysed cyclization cascades by radical relay Nature Catalysis 2 3 211 218 doi 10 1038 s41929 018 0219 x S2CID 104423773 Machrouhi Fouzia Hamann Beatrice Namy Jean Louis Kagan Henri B 1996 Improved Reactivity of Diiodosamarium by Catalysis with Transition Metal Salts Synlett 1996 7 633 634 doi 10 1055 s 1996 5547 S2CID 196761752 Molander G A McKiie J A 1992 Samarium II iodide induced reductive cyclization of unactivated olefinic ketones Sequential radical cyclization intermolecular nucleophilic addition and substitution reactions J Org Chem 57 11 3132 3139 doi 10 1021 jo00037a033 Ankner Tobias Goran Hilmersson 2009 Instantaneous Deprotection of Tosylamides and Esters with SmI2 Amine Water Organic Letters 11 3 American Chemical Society 503 506 doi 10 1021 ol802243d PMID 19123840 Patrick G Steel 2001 Recent developments in lanthanide mediated organic synthesis J Chem Soc Perkin Trans 1 21 2727 2751 doi 10 1039 a908189e Molander G A Harris C R 1996 Sequencing Reactions with Samarium II Iodide Chem Rev 96 1 307 338 doi 10 1021 cr950019y PMID 11848755 K C Nicolaou Shelby P Ellery Jason S Chen 2009 Samarium Diiodide Mediated Reactions in Total Synthesis Angew Chem Int Ed 48 39 7140 7165 doi 10 1002 anie 200902151 PMC 2771673 PMID 19714695 Procter David J Flowers II Robert A Skydstrup Troels 2009 Organic Synthesis Using Samarium Diiodide Royal Society of Chemistry ISBN 978 1 84755 110 8 Retrieved from https en wikipedia org w index php title Samarium II iodide amp oldid 1213339777, wikipedia, wiki, book, books, library,
