Samarium compounds using

Many of the compounds used have additional functional groups, including ester, amide, ether, and acetal. These groups may be involved in coordination to samarium and thereby influence the stereoselectivity of the reaction. 

Another completely different approach consists in choosing a dye, that already possesses aminocarboxylate functions (Meshkova et al., 1992a), such as triphenylmethane dyes. The latter can be used for selective luminescent determination of Nd111 and Ybm in samarium oxide, for instance. As previously described in the section devoted to /3-diketonates (section 3.2.1), the triplet excited states of /i-dikctonatcs lie at energies >20 000-25 000 cm-1, above most of the accepting levels of Lnm ions. As a consequence, determination of Ndm and Yb111 in europium or samarium oxides is difficult using /3-dike to nates since these two ions exhibit luminescence in the NIR, especially Smm with emission lines at 908, 930, 950, and 1038 nm close to the analytical lines of Ndm and Ybm. Therefore, the detection limit of Ndm and Ybm in samarium compounds by luminescence of their ternary complexes with tta and phen is only 0.1-1 wt%. 

Another important metal for Barbier-type reaction is samarium. Allyl bromide reacts with a ketone and Sm to give the homoallylic alcohol. Samarium compounds, such as Sml2, can also be used with allylic halides. 

A compound of samarium is used as a catalyst in the manifacture of ethanol, which is produced at plants such as the one pictured here. IMAGE COPYRIGHT JIM PARKIN, 2007. USED UNDER LICENSE FROM SHUTTERSTOCK.COM. 

Samarium is used to dope calcium fluoride crystals for use in optical masers or lasers. Compounds of the metal act as sensitizers for phosphors excited in the infrared the oxide exhibits catalytic properties in the dehydration and dehydrogenation of ethyl alcohol. It is used in infrared absorbing glass and as a neutron absorber in nuclear reactors. The metal is priced at about 3.50/g (99.9%). Little is known of the toxicity of samarium therefore, it should be handled carefully. 

The compound Sm,Co - SmO, is a permanent magnet. Samarium is used also as a burnable poison in nuclear reactors. Finally, its compounds are used as phosphors for television screens, catalysts, and ceramic capacitors. 

Cyclopentanoids have been prepared by samarium diiodide-catalysed reaction of 8 (R-Tbdms) with either aldehydes or ketones. The stereochemical outcome was dependent on the carbonyl compound used, with cyclohexanone giving 9 as a single product, while cyclohexane carboxaldehyde gave an isomeric mixture containing predominantly 10. ... 

Synthetic Methods for Redox Reactions Using Phosphorus, Vanadium and Samarium Compounds... 

Various methods may be considered for the synthesis of divalent ytterbium or samarium compounds. Some of them, such as metathetical reactions, have been widely used but others that until now include only a few examples seem to be very attractive, for example, electrochemical reductions. 

Other catalytic uses of rare-earth compounds have not reached the same development. Neodymium salts are, however, used for mbber manufacturing (22). Divalent samarium haHdes are employed in organic synthesis (23). 

Metal-induced reductive dimerization of carbonyl compounds is a useful synthetic method for the formation of vicinally functionalized carbon-carbon bonds. For stoichiometric reductive dimerizations, low-valent metals such as aluminum amalgam, titanium, vanadium, zinc, and samarium have been employed. Alternatively, ternary systems consisting of catalytic amounts of a metal salt or metal complex, a chlorosilane, and a stoichiometric co-reductant provide a catalytic method for the formation of pinacols based on reversible redox couples.2 The homocoupling of aldehydes is effected by vanadium or titanium catalysts in the presence of Me3SiCl and Zn or A1 to give the 1,2-diol derivatives high selectivity for the /-isomer is observed in the case of secondary aliphatic or aromatic aldehydes. 

While ytterbium(II) benzamidinate complexes have been known for many years/ the synthesis of the first divalent samarium bis(amidinate) required the use of a sterically hindered amidinate ligand, [HC(NDipp)2l (Dipp = C6H3Pr2-2,6)/ As illustrated in Scheme 54, the dark green compound Sm(DippForm)2(THF)2 (DippForm = [HC(NDipp)2] ) can be prepared by three different synthetic routes. Structural data indicated that hexacoordinated... 

Another useful reagent for reduction of a-acetoxyketones and similar compounds is samarium diiodide.233 Sml2 is a strong one-electron reducing agent, and it is believed that the reductive elimination occurs after a net two-electron reduction of the carbonyl group. 

Low-valent lanthanides represented by Sm(II) compounds induce one-electron reduction. Recycling of the Sm(II) species is first performed by electrochemical reduction of the Sm(III) species [32], In one-component cell electrolysis, the use of sacrificial anodes of Mg or A1 allows the samarium-catalyzed pinacol coupling. Samarium alkoxides are involved in the transmet-allation reaction of Sm(III)/Mg(II), liberating the Sm(III) species followed by further electrochemical reduction to re-enter the catalytic cycle. The Mg(II) ion is formed in situ by anodic oxidation. SmCl3 can be used in DMF or NMP as a catalyst precursor without the preparation of air- and water-sensitive Sm(II) derivatives such as Sml2 or Cp2Sm. 

---