Samarium(II) bromide

Samarium(II) bromide is an inorganic compound with the chemical formula SmBr
₂.^[6] It is a brown solid that is insoluble in most solvents but degrades readily in air.^[2]

Samarium(II) bromide

Names
IUPAC name samarium(II) bromide
Other names samarium dibromide dibromosamarium
Identifiers
CAS Number	50801-97-3
3D model (JSmol)	Interactive image
ChemSpider	10008489
PubChem CID	11833842
CompTox Dashboard (EPA)	DTXSID701312845
InChI InChI=1S/2BrH.Sm/h2*1H;/q;;+2/p-2 Key: AEPYKHCUOAUXAI-UHFFFAOYSA-L
SMILES Br[Sm]Br
Properties
Chemical formula	SmBr2
Molar mass	310.17 g/mol[1]
Appearance	Brown crystals
Melting point	669 °C (1,236 °F; 942 K)[2]
Boiling point	1,880 °C (3,420 °F; 2,150 K)[citation needed]
Magnetic susceptibility (χ)	+5337.0·10−6 cm3/mol [3][4]
Structure
Crystal structure	SrBr2[5]
Hazards
GHS labelling:
Pictograms
Signal word	Warning[1]
Hazard statements	H315, H319, H335[1]
Precautionary statements	P261, P305+P351+P338[1]
Related compounds
Other anions	Samarium(II) chloride Samarium(II) iodide
Other cations	Samarium(III) bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Structure

In the gas phase, SmBr
₂ is a bent molecule with Sm–Br distance 274.5 pm and bond angle 131±6°.^[7]

History

Samarium(II) bromide was first synthesized in 1934 by P. W. Selwood, when he reduced samarium tribromide (SmBr₃) with hydrogen (H₂). Kagan also synthesized it by converting samarium(III) oxide (Sm₂O₃) to SmBr₃ and then reducing with a lithium dispersion in THF. Robert A. Flowers synthesized it by adding two equivalent of lithium bromide (LiBr) to samarium diiodide (SmI₂) in tetrahydrofuran. Namy managed to synthesize it by mixing tetrabromoethane (C₂H₂Br₄) with samarium metal, and Hilmerson found that heating the tetrabromoethane or samarium greatly improved the production of samarium(II) bromide.^[8]

Reactions

Samarium(II) bromide has reducing properties reminiscent of the more commonly used samarium diiodide.^[9] It is an effective for pinacol homocouplings of aldehydes, ketones, and cross-coupling carbonyl compounds. Reports have shown that samarium(II) bromide is capable of selectively reducing ketones if it is in the presence of an alkyl halide.^[8]

Samarium(II) bromide forms soluble adducts with hexamethylphosphoramide. This species reduces imines to amines and alkyl chlorides to hydrocarbons.^[10] For example, SmBr₂(hmpa)_x converts cyclohexyl chloride to cyclohexane.^[11]

Samarium(II) bromide will reduce ketones in tetrahydrofuran if an activator is absent.^[12]

References

1. "Samarium(II) bromide 99.95% | Sigma-Aldrich". www.sigmaaldrich.com. Retrieved 20 December 2016.
2. Haynes, William M. (2013). CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data (94th ed.). CRC Press. p. 86. ISBN 9781466571150.
3. Haynes, William M. (2013). CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data (94th ed.). CRC Press. p. 135. ISBN 9781466571150.
4. Lide, David R. (2004). CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data (85th ed.). Boca Raton [u.a.]: CRC Press. p. 147. ISBN 9780849304859.
5. Sass, Ronald L.; Brackett, Thomas; Brackett, Elizabeth (December 1963). "The Crystal Structure of Strontium Bromide". The Journal of Physical Chemistry. 67 (12): 2862–2863. doi:10.1021/j100806a516.
6. Elements, American. "Samarium Bromide SmBr2". American Elements. Retrieved 20 December 2016.
7. Ezhov, Yu. S.; Sevast'yanov, V. G. (January 2004). "Molecular Structure of Samarium Dibromide". Journal of Structural Chemistry. 45 (1): 160–164. doi:10.1023/B:JORY.0000041516.14569.9c. S2CID 96049918.
8. Skrydstrup, David J. Procter, Robert A. Flowers, Troels (2009). Organic synthesis using samarium diiodide a practical guide. Cambridge: Royal Society of Chemistry. p. 157. ISBN 9781847551108.{{cite book}}: CS1 maint: multiple names: authors list (link)
9. Ho, Tse-Lok (2016). Fiesers' Reagents for Organic Synthesis Volume 28. John Wiley & Sons. p. 486. ISBN 9781118942819.
10. Pecharsky, Vitalij K.; Bünzli, Jean-Claude G.; Gschneidner, Karl A. (2006). Handbook on the physics and chemistry of rare earths. Amsterdam: North Holland Pub. Co. p. 431. ISBN 9780080466729.
11. Couty, Sylvain; Baird, Mark S.; Meijere, Armin de; Chessum, Nicola; Dzielendziak, Adam (2014). Science of Synthesis: Houben-Weyl Methods of Molecular Transformations Vol. 48: Alkanes. Georg Thieme Verlag. p. 153. ISBN 9783131722911.
12. Brown, Richard; Cox, Liam; Eames, Jason; Fader, Lee (2014). Science of Synthesis: Houben-Weyl Methods of Molecular Transformations Vol. 36: Alcohols. Georg Thieme Verlag. p. 129. ISBN 9783131721310.