Samarium iodide is easily prepared in nearly quantitative yields from samarium metal using diiodomethane, 1,2-diiodoethane, or molecular iodine, typically using THF as solvent.<ref>Template:Cite journal</ref> The resulting solutions are most often used directly, without isolation of the inorganic reagent itself.
Solid, solvent-free SmI2 forms by high temperature decomposition of samarium(III) iodide (SmI3).<ref name="SM_1930">G. Jantsch, N. Skalla: "Zur Kenntnis der Halogenide der seltenen Erden. IV. – Über Samarium(II)jodid und den thermischen Abbau des Samarium(III)jodids", Zeitschrift für Allgemeine und Anorganische Chemie, 1930, 193, 391–405; {{#invoke:CS1 identifiers|main|_template=doi}}.</ref><ref>G. Jantsch: "Thermischer Abbau von seltenen Erd(III)halogeniden", Die Naturwissenschaften, 1930, 18 (7), 155–155; {{#invoke:CS1 identifiers|main|_template=doi}}.</ref><ref name="GMELIN">Gmelins Handbuch der anorganischen Chemie, System Nr. 39, Band C 6, p. 192–194.</ref>
Reactions
Samarium(II) iodide is a powerful reducing agent – for example it rapidly reduces water to hydrogen.<ref name = "Greenwood"/> It is available commercially as a dark blue 0.1 M solution in THF. Although used typically in superstoichiometric amounts, catalytic applications have been described.<ref>Template:Cite journal</ref>
Typical reaction conditions use SmI2 in THF in the presence of catalytic NiI2.
Esters react similarly (adding two R groups), but aldehydes give by-products. The reaction is convenient in that it is often very rapid (5 minutes or less in the cold). Although samarium(II) iodide is considered a powerful single-electron reducing agent, it does display remarkable chemoselectivity among functional groups. For example, sulfones and sulfoxides can be reduced to the corresponding sulfide in the presence of a variety of carbonyl-containing functionalities (such as esters, ketones, amides, aldehydes, etc.). This is presumably due to the considerably slower reaction with carbonyls as compared to sulfones and sulfoxides. Furthermore, hydrodehalogenation of halogenated hydrocarbons to the corresponding hydrocarbon compound can be achieved using samarium(II) iodide. Also, it can be monitored by the color change that occurs as the dark blue color of SmI2 in THF discharges to a light yellow once the reaction has occurred. The picture shows the dark colour disappearing immediately upon contact with the Barbier reaction mixture.
Work-up is with dilute hydrochloric acid, and the samarium is removed as aqueous Sm3+.
Carbonyl compounds can also be coupled with simple alkenes to form five, six or eight membered rings.<ref>Template:Cite journal</ref>
Tosyl groups can be removed from N-tosylamides almost instantaneously, using SmI2 in conjunction with distilled water and an amine base. The reaction is even effective for deprotection of sensitive substrates such as aziridines:<ref name="Ankner2009">Template:Cite journal</ref>
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