Samarium availability

Relatively inexpensive samarium depends upon the mischmetal production and the production of other separated light lanthanides from the monazite and bastnasite ores for other products. In the preparation of mischmetal samarium is naturally concentrated in the slag because it is only reduced to the divalent state during electrolysis while the other rare earths are reduced to metal at the cathode. The samarium is cheaply recovered from the slag. In the early 1980 s when mischmetal production peaked, the total amount of samarium available from both the mischmetal production and as a by-product for other separated rare earths was about 400 tons per year. The production of samarium could be increased but it would be much more expensive since it would have to be separated from the ores for itself and bear the burden of the separation costs since the other lanthanides would be surplus materials. 

Oxazolines can be obtained by the Lewis acid catalyzed epoxide ring opening of glycidic esters or amides (e.g., 118) with acetonitrile . Oxazolidines are available from the palladium-catalyzed cycloaddition of vinyl epoxides with imines <00H885> or the samarium-promoted reaction of ketimines (e.g., 120) with unfunctionalized... 

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. 

When the cyclotron bombardment method became available, H. B. Law, M. L. Pool, J. D. Kurbatov, and L. L. Quill at Ohio State University bombarded samples of neodymium and samarium and obtained radioactive preparations which they believed might contain some 61 (18). C. S. Wu and E. Segre confirmed this (19). F. A. Paneth pointed out that they probably actually had obtained 61 in their mixtures, but the cyclotron method was not sufficiently powerful to give conclusive evidence of its existence (10). Nevertheless, the Ohio State group proposed the name cyclonium for the element. 

Some data on samarium compounds are available. For the 650-m/n emission peak Bhaumik et al (171) find for samarium benzoylacetonate microcrystals 15 /nsec at both 300° and 90°K. The compound samarium dibenzoylmethide has a lifetime of 45 /nsec at both 300° and 90°K, while Dieke and Hall (88) report a value of around 10 /nsec for the hydrated chloride at the same temperatures. 

The radionuclides commercially available and most commonly used for a number of the foregoing applications include anhmony-125 banum-133, 207 bismuth-207 bromine-82 cadmium-109, 115 m calcium-45 carbon-14 cerium-141 cesium-134, 137 chlorine-36 chromium-51 cobalt-57, 58, 60 copper-64 gadolimum-153 germanium-68 gold-195. 198 hydrogen-3 (tritium) indium-111, 114 m iodine-125, 129, 131 iron-55, 59 krypton-85 manganese-54 mercury-203 molvbdenum-99 nickel-63 phosphorus-32. 33 potassium-42 promethium-147 rubidium-86 ruthenium-103 samarium-151 scandium-46 selenium-75 silver-110 m sodium-22, strontium-85 sulfur-35 technetium-99 thallium-204 thulium-171 tin-113, 119 m, 121 m. titamum-44 ytterbium-169, and zinc-65. 

The 4,7-dimethoxy-2,2-dimethyl-l,3,2-benzodiselenastannole 321 was prepared from commercially available 1,4-dimethoxybenzene 320 by a sequence of tandem ortho-lithiation and selenation, and followed by dimethyltin protection in 28% yield (Scheme 51). Then, sequential treatment of the stannole 321 in THF with selenyl chloride, trimethylsilyl trifluoromethanesulfonate (TMSOTf), and samarium iodide gave crystalline 4,7-dimethoxybenzotri-selenole 42 in 75% yield <1996H(43)1843>. The structure was characterized by X-ray crystallographic analysis (Section 6.12.3.1). 

The retrosynthetic approach to welwitindolinone A isonitrile (6) used by the Wood group is shown in Scheme 33. After recognition of the possibility of deriving the vinyl isonitrile fragment from a ketone, the disconnection of 6 to 140 was proposed. A literature report of a samarium (II) iodide-mediated reductive coupling of acrylates with isocyanates to give amides, which could be expected to lead to a new spirooxindole synthesis, prompted the disconnection of 140 to 141. This compound was to be obtained from the readily available cyclohexadiene derivative 143, by way of bicyclic ketone 142. 

For various types of catalyst there are results of kinetic investigations for the oxidative dehydrogenation of ethane available (e.g., for a magnesium oxide catalyst doped with samarium oxide, lithium nitrate and ammonium chloride [64] or a V2O5/Y-AI2O3 catalyst [68]). In another study with a Sn.oLai.oNdi.oOx catalyst, investigations were reported of noncatalytic reactions, which were found to be significant at temperatures above 700 °C [69]. 

Samarium(II) iodide (Sml2) is commercially available as a solution in THF or can be prepared readily using one of several straightforward methods that have... 

Figures 20A and B show the PL spectra, recorded at 290 K, at 600 nm, and as a function of pressure, for Cs9(SmW10O36) and SmWi0O36-LDH, respectively (Park et al., 2002). For the sake of comparison, the line shapes are normalized and displaced along the vertical axis. In both cases, the peak position is red-shifted by 4—5 nm when the hydrostatic pressure increases from 1 bar to 61 kbar. It was shown that the red-shift from A to A lies solely in the deformation of the samarium complexes by the uniaxial stress exerted by the host layers, whereas the shift from B to B is also influenced by the change in the cation environment. Under the same conditions, B is not at the same position for the non-intercalated (HN (n -b u t y 1) 3) 9 (SmW10O3e) and Cs9(SmWi0O36) compounds (Park et al., 2002). Thus only peak A is available to measure the unixial stress. This observation can be used to determine the uniaxial stress, when the external pressure is zero. For the SmW10O36—LDH system, the uniaxial stress varies significantly from 75 at 28 K to 140 kbar at 290 K (Park et al., 2002).

PmCl3.xH20, Pm(N03)3.xH20, and Pm(C2O4)3.10H2O. It would be expected that promethium would form some stable compounds in the +2 oxidation state, though they are unlikely to be made in aqueous solution. No definite evidence has yet been obtained, since studies have been hindered both by the small quantities of the element available and by its radioactivity. The properties of promethium fit neatly into position between neodymium and samarium it is a microcosm of lanthanide chemistry in general. 

The secondary reduction of the terminal radical by Sml2 generates samarium alkyl species which are suitable for classical organometallic reactions, e.g. protonation, acylation, reactions with carbon dioxide, disulfides, diselenides, or the Eschenmoser salt. A broad variety of products is available (hydroxy-substituted alkanes, esters, carboxylic acids, thioethers, selenoethers, tertiary amines) by use of the double-redox four-step (reduction-radical reaction-reduction-anion reaction) route (Scheme 20) [73]. 

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