Metals samarium

Samarium metal in isopropanol also achieves reduction.195 Like the Meerwein-Pondorff-Verley procedure, these conditions are believed to be under thermodynamic control and the more stable stereoisomer is the main product.196... 

Hybrid materials [Ln N(SiMe3)2 3] AS-380.7oo with yttrium (12c) and samarium metal centers (12d) (Table 12.3) have been studied for the transformation of benz-aldehyde (Sj) (Table 12.10), displaying a lower conversion than the molecular homologs Ln[N(SiMe3)2]3 [89% (Y), 67% (Sm)j [117]. 

Seccand example - In the production of samariumcobalt permanent magnets impurities have practically only a dilution effect. One can therefore use instead of a 99.9 % pure samarium metal a significantly cheaper 90 %, perhaps even 80 % pure metal vdth the balance other rare earths. In any case, it is necessary in this instance that the conposition of the other rare earth elements be held constant, vdiich is not always quite so siitple. 

The oxide, the precursor to the metal/alloy, is currently available to the extent of about 150-200 tons per year and output may conceivably be doubled by 1985. Even so, when expressed in terms of samarium metal this quantity is relatively small, hence it is desirable to optimise the available resources by whatever means are possible. In Table II we illustrate one solution to the problem, namely the production of alloys containing much greater quantities of mischmetal. 

In ebenfalls guten Ausbeuten werden Nitrobenzole mit Samarium-Metall zu Azoxy-Verbindungen reduziert3. 

Some additives accelerate the pinacol coupling reactions. Addition of Me3SiCl to Sml2 also accelerates the pinacol coupling reactions of aliphatic ketones and aldehydes. Pinacol coupling reactions are also promoted with samarium metal and a Lewis acid such as Et2AlCl or MesSiCl. Coordination of such a Lewis acid to a carbonyl oxygen facilitates the one-electron reduction by samarium. 

The preparation of samarium sulphide, SmS, is of interest because it contains samarium (a lanthanide element) In an unusual oxidation state +2 instead of the more common state +3. Samarium metal In powder form and powdered sulfur are... 

Reduction of multiple bonds with samarium diiodide has been reviewed. Chemo-and stereo-selective reduction of various compounds such as conjugated alkenes, c/,/3-unsaturated carboxylic acids, activated alkynes, carbonyl, azides, nitriles, and nitro compounds, under mild conditions, has been discussed. Recent developments in the use of samarium metal in this field have also been discussed.381... 

Samarium metal, in the presence of various additives such as ammonium chloride or bromide, induces reductive dimerizations of aromatic ketones to give 1,2-diols, with some diastereoselectivity, and with some alcohol (i.e. reduced ketone) by-product.164 The syn-selectivity observed in many cases may be due to samarium chelation of the... 

Exposure of the dioxanobornane 1055 to samarium diiodide in the presence of samarium metal at low temperature leads to the formation of a mixture of the tetrahydropyran-4-one 1056 and the ring opened product 1057. Treatment of this mixture with tosic acid leads to a single tetrahydropyran-4-one product (Scheme 269) <2004OL3735>. 

Scheme 50 Formation of a <

In 1992, Ishii reported the generation of a Sml2 equivalent that displayed similar reactivity to Sml2 by treatment of samarium metal with TMSC1 and Nal.4... 

In recent years, exposing the preparation of the reagent from samarium metal and an oxidant to different stimuli has led to significant improvements in reaction time. Concellon utilized the sonication of samarium metal and iodoform at room temperature to give a solution of Sml2 in THF in approximately 5 min (Scheme 2.3).5 This approach was also used by Flowers to synthesise other Sm(II) species.6 It was also reported that using different oxidants, such as 1,2-diiodoethane, diiodomethane and iodine, works just as well with this technique.5... 

Hilmersson7 achieved similar results by heating the reaction to 180 °C under microwave conditions for 5 min (Scheme 2.3). Although this method is compatible with all of the oxidants described above, formation of Sml2 from samarium metal and iodine is preferred as no gas evolution accompanies the reaction.7... 

The exploration of Lnl2(THF) c, in particular, Sml2(THF)4, which is prepared by the reaction of samarium metal with ICH2CH2I in THF [96], or the reaction of iodine with an excess of samarium metal in THF, provides appropriate starting materials for divalent organometallic complexes (Equation 8.29). 

Metals. Kruglikh, et al. (104) measured saturated vapor pressures of erbium, samarium, and ytterbium by the Knudsen effusion method, and standard (average) sublimation entropies of 18.4, 20.7, and 25.6 cal./(gram atom °K.) were derived. Nesmeyanov, et al. (146) studied the vapor pressure of yttrium by an integral variant of the effusion technique. Similar studies at higher temperatures by Herrick (70) on samarium metal have been interpreted in good accord by both first and second law methods. Ideal gas thermodynamic functions have been derived from 100 °K. to 6000°K. at 100° intervals for both actinide and lanthanide elements by Feber and Herrick (45). 

Disulfides RSSR can also be produced. Other sulfonic acid derivatives can be converted to disulfides. Esters, such as PhSAc, are converted to disulfides PhS—SPh with Clay an and microwave irradiation. Thiobenzoate derivatives PhSBz are similarly converted to PhS—SPh with SmU. In a similar manner, RS—S03Na is converted to RS—SR when heated with samarium metal in water. ... 

Samarium metal poses a threat to workers who may come into contact with it and its fumes. When inhaled, those fumes may damage the lungs and, over long periods of time, affect the liver. Very little information is available on the health hazards of samarium compounds, although they are suspected of being irritants to the skin, eyes, and respiratory system. 

Mercury(II) chloride (1.084 g, 4.00 mmol) and samarium metal (0.902 g, 6.00 mmol) are allowed to react as described above, giving the white title compound. Yield 0.520 g (49%). 

Samarium diiodide is very conveniently prepared by oxidation of samarium metal with organic di-halides or with iodine (equations 10-12). Deep blue solutions of SmI (0.1 M in THF) are generated in virtually quantitative yields by these processes. This salt can be stored as a solution in THF for long periods when it is kept over a small amount of samarium metal. Tetrahydrofuran solutions of SmI are commercially available as well. If desired, the solvent may be removed to provide Sml2-(THF)n as a powder. For synthetic purposes, Smh is typically generated and utilized in situ. 

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