Samarium(II) bromide

Samarium bromide is an inorganic compound with the chemical formula. It is a brown solid that is insoluble in most solvents but degrades readily in air.

Structure

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

History

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

Reactions

Samarium bromide has reducing properties reminiscent of the more commonly used samarium diiodide. It is an effective for pinacol homocouplings of aldehydes, ketones, and cross-coupling carbonyl compounds. Reports have shown that samarium bromide is capable of selectively reducing ketones if it is in the presence of an alkyl halide.
Samarium bromide forms soluble adducts with hexamethylphosphoramide. This species reduces imines to amines and alkyl chlorides to hydrocarbons. For example, SmBr₂_x converts cyclohexyl chloride to cyclohexane.
Samarium bromide will reduce ketones in tetrahydrofuran if an activator is absent.