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]