Dysprosium divalent

Gamma rays from spent reactor fuel rods were used for the photoreduction of the trivalent lanthanides. A spectral survey of these divalent containing crystals has been presented by McClure and Kiss (16). This photoreduction technique reduces only a minor fraction of the total trivalent concentration, and those divalent ions produced are unstable with respect to heat and/or light. Fong (3) has described these effects using divalent dysprosium as an example. 

Tml2, Dyh and Ndh have also been used in an acetonitrile/amine coupling reaction, which produced amidines of general formula MeC (=NH)NR R R R2 = H, Me H, iPr H, fBu Et2). The reaction is sub-stoichiometric in rare-earth diiodide but not really catalytic since part of the produced amidine remained tightly held aroimd the rare-earth metal it could be liberated by heating a trivalent intermediate formulated as Rl2(amidine)4(amidinate) (R = Nd, Dy, Tm) imder vacuum, and the residue could be recycled to produce more amidine. This reaction is not specific of the divalent iodides since many rare-earth triiodides were also effective. In the case of dysprosium and diethylamine, an intermediate trivalent amidine complex has been isolated and structurally characterised in the form of the zwitterionic [Dy MeC(=NH)NEt2 4][(I)3] (Bochkarev et al., 2007) (Figure 9). 

The low-valent molecular chemistry of rare earths was once thought to be restricted to divalent samarium, europium and ytterbium. This chemistry has now been extended to many of the rare earths in the zero-valent state, to mono- and divalent scandium, to divalent lanthanum, cerium, neodymium, dysprosium and thulium, and to systems in which dinitrogen is activated and that may contain yet other highly reactive divalent rare earths. It is the opinion of the author that this research area is likely to find fascinating developments in the near future. 

The most common raw materials for the REM molten salt electrolysis are in the RE " state, such as RE2O3, RECI3. But RE " still exists to a certain extent in the molten salts, especially in the chloride melts, some rare earth metal elements have presented a higher level of divalent oxidation states, such as neodymium, samarium, europium, dysprosium, thulium, and ytterbium, which result in a lower current efficiency. For Sm and Eu molten salt electrolysis processes, even no metals can be obtained at the cathodes due to a cyclic transformation of Sm VSm (Eu /Eu ) and Sm /Sm (Eu /Eu ) on the electrodes during electrolysis. And some of the rare earth metal elements show tetravalent oxidation states at the chlorine pressure far in excess of atmospheric pressure, such as Ce. Most of the rare earth metal elements in oxidation state of -1-4 are not stable in chloride melts, because the reaction occurs according to the following equation RE " -I- Cl = RE -" -I- I/2CI2. 

For ninety years samarium, europium, and 5dterbium were the only accessible divalent rare earths in molecular organometalhc chemistry. However, the past two decades have witnessed the addition of scandium(II), yttrium(II), lanthanum(II), cerium(II), neodymium(II), dysprosium(II), hohnium(II), erbium(n) and thulium(II) in a molecular context.Thus 12 of the 17 rare earths are now known in the divalent state in an organometalhc context and no other area of chemistry has seen such a dramatic expansion in the number of available oxidation states. It would therefore seem to be only a matter of time before divalent states are extended to the remaining REs. An extensive palate of... 

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