Lanthanide mixed salts

Inspection of the proposed nitration mechanism (Scheme 1) reveals that the mononitrate dipositive lanthanide species [Ln(H20)x(N03)](0Tf)2 (1) is the key intermediate. An independent preparation and characterisation of such a species enables possible indentification of 1 directly in situ in the reaction mixture. Additionally, spectroscopic examination of these salts may provide some evidence for our working model. We have developed a novel preparation of these mixed salts by simple metathesis of lanthanide chlorides with the requisite quantities of silver nitrate and silver triflate in water (Scheme 3).17 The resulting hydrated salts were white or lightly coloured (pink, green or yellow) solids which were found to be stable indefinitely at room temperature in the solid state. 

Ln(OH)3 can be converted to the corresponding hydrated chloride or fluoride by treatment with the appropriate acids. These hahde compoxmds are carefully dehydrated to yield the lanthanide anhydrous salts. Alisch metal is a mixture of lanthanide elements (it is approximately 50% cerium), and is obtained via the electrolysis of the fused mixed lanthanide chlorides. 

Comparable recent detailed reviews of the actinide halides could not be found. The structures of actinide fluorides, both binary fluorides and combinations of these with main-group elements with emphasis on lattice parameters and coordination poly-hedra, were reviewed by Penneman et al. (1973). The chemical thermodynamics of actinide binary halides, oxide halides, and alkali-metal mixed salts were reviewed by Fuger et al. (1983), and while the preparation of high-purity actinide metals and compounds was discussed by Muller and Spirlet (1985), actinide-halide compounds were hardly mentioned. Raman and absorption spectroscopy of actinide tri- and tetrahalides are discussed in a review by Wilmarth and Peterson (1991). Actinide halides, reviewed by element, are considered in detail in the two volume treatise by Katzet al. (1986). The thermochemical and oxidation-reduction properties of lanthanides and actinides are discussed elsewhere in this volume [in the chapter by Morss (ch. 122)]. 

Although direct reaction of lanthanide mono-porphyrins with free phthalo-cyanine or its lithium derivatives is generally more efficient than the template synthesis, and gives rise to mixed-ligand complexes, the template strategy can also be applied for synthesis of phthalocyanine-porphyrin complexes, as in the case of unsymmetric bisphthalocyanine complexes (Scheme 8.2, B(b)) [106, 136, 145, 146]. Thus, metallation of free porphyrins with lanthanide salts in TCB or n-octanol leads to single-decker complexes, which then react with phthalonitriles under the action of DBU in alcoholic media to give the desired compounds. 

No, the editor didn t know what this name meant either.) It means salts of the triva-lent anions of Group V, restricted in [1] to arsenides, antimonides and bismuthides and prepared by reaction of sodium pnictides with anhydrous halides of transition and lanthanide metals. This violently exothermic reaction may initiate as low as 25°C. Avoidance of hydrated halides is cautioned since these are likely to react uncontrollably on mixing. Another paper includes a similar reaction of phosphides, initiated by grinding [2], Nitrides are reported made from the thermally initiated reaction of sodium azide with metal halides, a very large sealed ampoule is counselled to contain the nitrogen [3],... 

The study of coordination compounds of the lanthanides dates in any practical sense from around 1950, the period when ion-exchange methods were successfully applied to the problem of the separation of the individual lanthanides,131-133 a problem which had existed since 1794 when J. Gadolin prepared mixed rare earths from gadolinite, a lanthanide iron beryllium silicate. Until 1950, separation of the pure lanthanides had depended on tedious and inefficient multiple crystallizations or precipitations, which effectively prevented research on the chemical properties of the individual elements through lack of availability. However, well before 1950, many principal features of lanthanide chemistry were clearly recognized, such as the predominant trivalent state with some examples of divalency and tetravalency, ready formation of hydrated ions and their oxy salts, formation of complex halides,134 and the line-like nature of lanthanide spectra.135... 

The ZEALEX Process Researchers from KRI have shown that the zirconium salt of dibutyl phosphoric acid (ZS-HDBP) was soluble in Isopar-L in the presence of 30% TBP. This super PUREX solvent, known as ZEALEX, extracts actinides (Np-Am) together with lanthanides and other fission products, such as Ba, Cs, Fe, Mo, and Sr from nitric acid solutions. The extraction yields depend on both the molar ratio between Zr and HDBP in the 30% TBP/Isopar-L mixture and the concentration of HN03 (232). Trivalent transplutonium and lanthanide elements can be stripped together from the loaded ZEALEX solvent by a complexing solution, mixing ammonium carbonate, (NH4)2C03, and ethylenediamine-N.N.N. N -tetraacetic acid (EDTA). An optimized version of the process should allow the separation of... 

Figure 5.3 Synthetic conditions for the mixed-ligand Pc complexes, containing one Pc ligand. Route 1 interaction of o-dicyanobenzene(s) and their analogues with lanthanide salts. Route 2 metallation reaction of the macrocyclic ligand or its dianione by lanthanide compounds. Route 3 reactions of axial substitution in the environment of the central atom in lanthanide complexes ([96] and references cited therein). (From Ref. 96, with permission.)...

Lanthanide complexes of poorly coordinating ligands such as aldehydes and ketones [24], esters [25], and ligands containing sulphur and phosphorus [26] have been prepared. The procedure consists of mixing a solution of hydrated lanthanide salt with a solution of the... 

Lanthanide complexes with macrocyclic polyethers [64] have been obtained by mixing solutions of the ligand and solution of a hydrated lanthanide salt [65]. 

Aqueous aliquots of the macromolecule and lanthanide salt, both in the same buffer of known pH and ionic strength are mixed. Slow evaporation of the mixture containing an excess of lanthanide salt results in crystallization of the complex. Centrifugation and decantation of the supernatant liquid gives the solid complex. Repeated extraction with alcohol will remove the excess lanthanide salt [78]. 

Phthalocyanines are tetraaza tetrabenzo analogues of porphyrins. Lanthanide complexes with phthalocyanines are prepared by the condensation of phthalonitrile (4 moles) with a lanthanide salt. The monocomplexes were prepared by heating a 1 4 mixture of lanthanide saltiphthalonitrile at 275°C. The molten solution solidified after an hour and purification of the complex is done by removal of excess phthalonitrile and impurities with organic solvents. Final purification is done by chromatography [85]. The bis complexes are prepared in a similar fashion but with a large excess of phthalonitrile [86]. Mixed ligand... 

This transition (Fig. 4.48), which is unique for a given Eu(III) chemical environment, has been monitored versus time after mixing the lanthanide salt and the ligand in the presence of an excess of triethylamine. The results point to a very fast initial formation of the 1 1 complex [Eu(N03)(H6butCx[8])(DMF)4] (half-life in the ms range) which then slowly transforms into the bimetallic 2 1 assembly with a half-life of 5500 s in the presence of an 18-fold excess of triethylamine. It is noteworthy that this second reaction is 6 times slower in the presence of a 4-fold excess of Et3N and becomes incomplete when only one equivalent of base per Eu(III) ion is added. 

The significant nephelauxetic effect in the spectra of Nd(III) hydroxyaquobisbenzoy-lacetonate was attributed to resonance in the /J-diketone by Dutt [238], while the others interpreted this to the lower coordination number of six. Anhydrous lanthanide salts mixed with /1-dikctonatcs of the type (LnL1, L11, L111) show markedly greater nephelauxetic effect and intensity than the lanthanide tris /J-diketonates in semiaqueous media which has been attributed to a lower coordination number in anhydrous /J-diketonates [239,240]. 

Feed Solutions. The process is applicable to solutions of trivalent actinides or lanthanides in either dilute acid or a variety of salt solutions in either nitrate or chloride or mixed media. Sodium concentrations up to 3 M can be tolerated, but lithium begins to have adverse effects above 2 M and potassium is objectionable even at 0.5 M. Certain special constituents can be tolerated in the feed if specific precautions (described later) are taken. 

---