Samarium (II) iodide

Crystal structure
__ Sm 2+      __ I -
General
Surname	Samarium (II) iodide
other names	Samarium diiodide
Ratio formula	SmI 2
Brief description	dark green crystals
External identifiers / databases
CAS number 32248-43-4 PubChem 141689 Wikidata Q421504
properties
Molar mass	404.17 g mol −1
Physical state	firmly
Melting point	~ 840 ° C (decomposition)
solubility	moderately in tetrahydrofuran
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Samarium (II) iodide (SmI ₂ ) is a chemical compound made up of the elements samarium and iodine . Samarium (II) iodide is a deep green to black solid; it dissolves in water with a deep red color. It only acquired its special significance through its diverse use in syntheses in organic chemistry. Samarium (II) iodide was introduced together with ytterbium (II) iodide  (YbI ₂ ) as a reagent for organic synthesis.

presentation

Samarium belongs to the lanthanoids and has the electron configuration [Xe] 4f ⁶  6s ² . In its compounds it occurs preferentially in the oxidation state +3 and less often in the oxidation state +2.

Samarium (II) iodide was first reported in 1906. Samarium (II) iodide cannot be obtained from the elements through direct conversion; only samarium (III) iodide is formed in this way .

${\displaystyle \mathrm {2\ Sm\ +\ 3\ I_{2}\ \longrightarrow \ 2\ SmI_{3}} }$

Samarium (II) iodide is produced by reducing anhydrous samarium (III) iodide in a hydrogen stream at around 750 ° C:

${\displaystyle \mathrm {2\ SmI_{3}\ +\ H_{2}\ \longrightarrow \ 2\ SmI_{2}\ +\ 2\ HI} }$

Samarium (II) iodide can also be produced by reducing samarium (III) iodide with metallic samarium:

${\displaystyle \mathrm {2\ SmI_{3}\ +\ Sm\ \longrightarrow \ 3\ SmI_{2}} }$

Diiodo penta (THF) samarium (II)

The representation via samarium metal and 1,2-diiodoethane in tetrahydrofuran  (THF) at room temperature has become established. Due to the sensitivity of the reagents, work must be carried out without water and under an inert gas. Otherwise rapid oxidation to samarium (III) occurs in the presence of oxygen . This can be seen from the change in color from dark blue to yellow solution. The reagent is commercially available as a dark blue 0.1 M solution in THF, but is unstable in the long term, so it is better to prepare it fresh.

${\displaystyle \mathrm {Sm\ +\ ICH_{2}CH_{2}I\ {\xrightarrow[{}]{THF}}\ SmI_{2}\ +\ H_{2}C=CH_{2}} }$

Samarium metal can also be reacted with mercury (II) iodide or with iodine in THF.

properties

Physical Properties

Samarium (II) iodide is a deep green to black solid that dissolves in water with a deep red color. SmI ₂ begins to disproportionate again in Sm and SmI ₃ from 680 ° C. at 0.01  Torr and melts with significant decomposition at 840 ° C .; the SmI ₃ in turn releases iodine. Therefore, the melting point cannot be accurately determined.

Chemical properties

The redox potential Sm ²⁺ / Sm ³⁺ is −1.55 V, so it is a strong reducing agent. Samarium (II) iodide is also very sensitive to air and moisture. It is rapidly oxidized to samarium (III) in air . The aqueous solution decomposes in the course of about 15 minutes with evolution of hydrogen and extensive discoloration; basic iodides are deposited in the process. The reaction is stormy with acids.

use

Samarium (II) iodide is suitable in a large variety for standard reactions:

• Reductions (selective one-electron reducing agent )
• Ring opening reactions
• Ring closure reactions
• Dimerizations

Individual evidence

1. ↑ ^{a b c d e f} G. Jantsch, N. Skalla: “To the knowledge of the halides of the rare earths. IV. - About samarium (II) iodide and the thermal degradation of samarium (III) iodide ”, in: Journal for inorganic and general chemistry , 1930 , 193 , pp. 391–405; doi : 10.1002 / zaac.19301930132 .
2. ↑ Entry on Samarium (II) iodide. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
3. ↑ Data sheet Samarium (II) iodide, anhydrous, powder, ≥99.9% trace metals basis from Sigma-Aldrich , accessed on June 21, 2016 ( PDF ).
4. ↑ C. Matignon, E. Cazes, Ann. Chim. Phys. , 1906 , 8  (8), p. 417.
5. ^ ^{A b} P. Girard, Jean-Louis Namy, Henri B. Kagan : “Divalent Lanthanide Derivatives in Organic Synthesis. 1. Mild Preparation of SmI ₂ and YbI ₂ and Their Use as Reducing or Coupling Agents ”, in: J. Am. Chem. Soc. , 1980 , 102  (8), pp. 2693-2698; doi : 10.1021 / ja00528a029 .
6. ↑ John A. Soderquist: "Samarium (II) Iodide in Organic Synthesis", in: Aldrichimica Acta , 1991 , 24  (1), pp. 15-23.
7. ↑ G. Jantsch: "Thermal degradation of rare earth (III) halides", in: Die Naturwissenschaften , 1930 , 18  (7), pp. 155–155; doi : 10.1007 / BF01501667 .
8. ↑ Gmelin's Handbook of Inorganic Chemistry , System No. 39, Volume C 6, pp. 192-194.
9. ↑ www.organic-chemistry.org: Reducing Agents> Samarium (low valent)

literature

• Henri B. Kagan , Jean-Louis Namy: “Lanthanides in organic synthesis”, in: Tetrahedron , 1986 , 42  (24), pp. 6573-6614; doi : 10.1016 / S0040-4020 (01) 82098-6 .
• Dennis P. Curran, Thomas L. Fevig, Craig P. Jasperse, Michael J. Totleben: "New Mechanistic Insights into Reductions of Halides and Radicals with Samarium (II) Iodide", in: Synlett , 1992 , pp. 943-961; doi : 10.1055 / s-1992-21544 .
• Gary A. Molander, Christina R. Harris: "Sequencing Reactions with Samarium (II) Iodide", in: Chem. Rev. , 1996 , 96  (1), pp. 307-338; doi : 10.1021 / cr950019y .
• Patrick G. Steel: “Recent developments in lanthanide mediated organic synthesis”, in: J. Chem. Soc., Perkin Trans. 1 , 2001 , pp. 2727-2751; doi : 10.1039 / a908189e .
• Henri B. Kagan: "Twenty-five years of organic chemistry with diiodosamarium: an overview", in: Tetrahedron , 2003 , 59  (52), pp. 10351-10372; doi : 10.1016 / j.tet.2003.09.101 .
• Yusuke Asano, Shoko Suzuki, Tadashi Aoyama, Kosuke Shimizu, Masatsugu Kajitani, Yasuo Yokoyama: "Novel and Efficient Cyanofluoromethylation Promoted by Samarium (II) Species", in: Synthesis , 2007 , pp. 1309-1314; doi : 10.1002 / chin.200736068 .
• KC Nicolaou, Shelby P. Ellery, Jason S. Chen: “Samarium Diiodide Mediated Reactions in Total Synthesis”, in: Angew. Chem. Int. Ed. , 2009 , 48  (39), pp. 7140-7165; doi : 10.1002 / anie.200902151 ; PMID 19714695 ; PMC 2771673 (free full text).
• David J. Procter, Robert A. Flowers II, Troels Skydstrup: "Organic Synthesis Using Samarium Diiodide", 2009 , Royal Society of Chemistry, ISBN 978-1-84755-110-8 .

Web links

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