Neodymium 4 oxidation state

A true colorless glass such as an optical glass must be made with very low iron materials since decolorizing agents would reduce the transmission. The main physical decolorizers are manganese, selenium, cobalt and neodymium oxides. Manganese with a little cobalt is effective in complimenting the iron in the ferric state. 

The third oxide used for physical decolorizing is neodymium oxide. Its absorption curve closely compliments an average mixture of ferrous and ferric oxides especially with the strong absorption band at 589 nm. Neodymium oxide is also stable against any state of oxidation change in the furnace. Neodymium is exceptionally good as a decolorizer for potassium silicate and lead glasses. If the redox balance is not quite correct for the... 

Hoskins and Soffer (117) measured the fluorescent lifetime of the neodymium 4Fy2 state in yttrium oxide. They found a value of approximately 260 /zsec both at room temperature and at liquid-nitrogen temperature. They also observed a weaker long-lived component in the decay. They were unable to say whether this was evidence for a low-transition-probability ion site, or an effect of trapping of the resonance radiation near 0.9 /x. They report laser action, with a threshold of 260joules. This is a fairly high value for most crystalline materials. 

Table 13.3 Replicate determinations of plutonium oxidation-state species in filtered seawater using neodymium fluoride (100mgl-1) as co-precipitant...

Total tetravalent uranium may be precipitated as an insoluble oxalate or fluoride (Grinberg et at., 1957) or in trace amounts co-precipitated for example with neodymium fluoride (cf. Pu ). Such a procedure can be used to show whether uranium is present in the lower oxidation state, for example, in anoxic waters because hexavalent uranium does not co-precipitate in this way. 

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. 

These elements are usually terpositive, forming salts such as La(N03)g 6H20. Cerium forms also a w ell-defined series of salts in which it is quadripositive. This oxidation state corresponds to its atomic number, 4 greater than that of xenon. Praseodymium, neodymium, and terbium form dioxides, but not quadrivalent salts. 

Neodymium has only one stable oxidation state (+3) within the electrochemical window of water, but it forms several relatively stable compounds with oxygen and hydrogen, which differ in their degree of hydration and in their crystallographic structure. Nominal degree of hydration indicated by a chemical name/formula reported in the literature does not necessarily reflect the actual degree of hydration. PZCs/IEPs of Neodymium (hydr)oxides are presented in Tables 3.689 through 3.691. 

Fluorosulphates of most of the lanthanide elements in the oxidation state iii have been prepared by the action of peroxydisulphuryl difluoride on the anhydrous metal carbonates. The oxides of neodymium, samarium, and europium, however, gave indications of partial reaction with S2O6F2 to form mixtures of fluorosulphate with oxide. The vibrational spectra and structure of the lanthanide fluorosulphates suggested the presence of mixed co-ordination type anions. Fluorescence emission, and vibrational spectra of the europium compound indicated octaco-ordination and the presence of ter- and bi-dentate fluorosulphate groups. 

A bimolecular route is also postulated to explain the reduction of less electron rich hydrides when the lower oxidation state is accessible (samarium and ytterbium). Thus, the hydrogenolysis of analogous neodymium and samarium hydrides bearing tetramethylphospholyl ligands leads to the stable neodymium hydride and to the reduced samarium(II) metallocene, respectively (Scheme 8). 

Complexes between some lanthanides in a low oxidation state and olefins were isolated by W.J. Evans et al. (1978a, 1981b). Cocondensation of lanthanum, neodymium, samarium or erbium metal with butadiene or 2,3-dimethylbutadiene at — 196°C in a metal vaporization reactor produces a brown solid, which can be extracted by toluene and tetrahydrofuran yielding soluble brown products with the empirical formulas R(C4H4)j for R = Nd, Sm, Er, and R[(CH3)2C4H4]2 for R = La, Er. For these complexes the following three formulas have been suggested ... 

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... 

Halides of the lanthanides in the oxidation state -1-2 have been known since the early decades of the twentieth century. EuCl2, SmCl2, and YbCb were the first to be reported. For these 3 elements, ah 12 possible halides are known. This is not the case for the elements thulium, dysprosium, and neodymium for which only the halides of the fiiad chlorine, bromine, and iodine have been synthesized and crystallographically characterized. They structmaUy bear close resemblance to the respective alkahne-earth metal halides. The electronic configmations of the M + ions of these six elements are 6s 5d 4f with n = 4 (Nd), 6 (Sm), 7 (Eu), 10 (Dy), 13 (Tm), and 14 (Yb). 

Studies on promethium have been few because of its radioactivity, which calls for special safety measures. All available information on oxidation states, structure of compounds, etc., is in full agreement with the expected behaviour of an element between neodymium and samarium. The chemistry of promethium has been authoritatively reviewed by Weigel (1969, 1978). Most of the some 40 compounds known today have been synthesized by Weigel and Scherer they include a few complex inorganic compounds, e.g., carbonate and nitrate hydrates (Weigel, 1978). 

In the assessment of the refining performance of uranium, systematic data has been reported for the chemical properties of uranium complex in various alkali chlorides such as LiCl-RbCl and LiCl-CsCl mixtures [3-5], Information on the coordination circumstance of solute ions is also important since it should be correlated with stability. The polarizing power of electrolyte cations controls the local structure around neodymium trivalent Nd " " as an example of f-elements and the degree of its distortion from octahedral symmetry is correlated with thermodynamic properties of NdClg " complex in molten alkali chlorides [6]. On the other hand, when F coexists with Cr in melts, it is well-known that the coordination circumstances of solute ions are drastically changed because of the formation of fluoro-complexes [7-9]. A small amount of F stabilizes the higher oxidation states of titanium and induces a negative shift in the standard potentials of the Ti(IV)ITi(ni) and Ti(III)ITi(II) couples [7, 8], The shift in redox potentials sometimes causes specific electrochemical behavior, for example, the addition of F to the LiCl-KCl eutectic leads to the disproportionation of americium Am into Am " and Am metal [9],... 

Kondo H, Matsumiya M, Tsunashima K, Kodama S (2012) Investigation of oxidation state of the electrodeposited neodymium metal related with the water contents of phosphonium ionic liquids. ECS Trans 50(ll) 529-538... 

Hydrogen transfer reactions are highly selective and usually no side products are formed. However, a major problem is that such reactions are in redox equilibrium and high TOFs can often only be reached when the equilibria involved are shifted towards the product side. As stated above, this can be achieved by adding an excess of the hydrogen donor. (For a comparison, see Table 20.2, entry 8 and Table 20.7, entry 3, in which a 10-fold increase in TOF, from 6 to 60, can be observed for the reaction catalyzed by neodymium isopropoxide upon changing the amount of hydrogen donor from an equimolar amount to a solvent. Removal of the oxidation product by distillation also increases the reaction rate. When formic acid (49) is employed, the reduction is a truly irreversible reaction [82]. This acid is mainly used for the reduction of C-C double bonds. As the proton and the hydride are removed from the acid, carbon dioxide is formed, which leaves the reaction mixture. Typically, the reaction is performed in an azeotropic mixture of formic acid and triethylamine in the molar ratio 5 2 [83],... 

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