Samarium(II) bromide is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

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(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 Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...

dispersion in

THF Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...

. Robert A. Flowers synthesized it by adding two

equivalent Equivalence or Equivalent may refer to: Arts and entertainment *Album-equivalent unit, a measurement unit in the music industry *Equivalence class (music) *''Equivalent VIII'', or ''The Bricks'', a minimalist sculpture by Carl Andre *''Equivale ...

lithium bromide Lithium bromide (LiBr) is a chemical compound of lithium and bromine. Its extreme hygroscopic character makes LiBr useful as a desiccant in certain air conditioning systems.Wietelmann, Ulrich and Bauer, Richard J. (2005) "Lithium and Lithium Compo ...

(LiBr) to

samarium diiodide 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 solutions are green as well. It is a strong one-electron reducing ...

(SmI₂) in

tetrahydrofuran Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is ma ...

. Namy managed to synthesize it by mixing

tetrabromoethane Tetrabromoethane (TBE) is a halogenated hydrocarbon, chemical formula C2H2Br4. Although three bromine atoms may bind to one of the carbon atoms creating 1,1,1,2-tetrabromoethane this is not thermodynamically favorable, so in practice tetrabromoetha ...

(C₂H₂Br₄) with samarium metal, and Hilmerson found that heating the tetrabromoethane or samarium greatly improved the production of samarium(II) bromide.

Reactions

Samarium(II) bromide has reducing properties reminiscent of the more commonly used

. It is an effective for

pinacol Pinacol is a white solid organic compound. It is a diol that has hydroxyl groups (-OH) on vicinal carbon atoms. Preparation It may be produced by the pinacol coupling reaction from acetone: Reactions As a vicinal-diol, it can rearrange t ...

homocoupling A coupling reaction in organic chemistry is a general term for a variety of reactions where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = ...

s of

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...

s, and cross-coupling

carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a ...

compounds. Reports have shown that samarium(II) bromide is capable of selectively reducing ketones if it is in the presence of an

alkyl halide The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely ...

. Samarium(II) bromide forms soluble adducts with

hexamethylphosphoramide Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (an amide of phosphoric acid) with the formula This colorless liquid is a useful reagent in organic synthesis. Structure and reactivity HMPA is the oxide of the highly basic ter ...

. This species reduces

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bo ...

s to

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...

s and alkyl chlorides to

hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

. For example, SmBr₂(hmpa)_x converts cyclohexyl chloride to

cyclohexane Cyclohexane is a cycloalkane with the molecular formula . Cyclohexane is non-polar. Cyclohexane is a colorless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used). Cyclohexan ...

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

References

{{Lanthanide halides Bromides Samarium compounds Reducing agents Lanthanide halides