Sulfides, lanthanide

The interplay of variously capped (and oriented) trigonal coordination prisms with coordination octahedra is essential also for the complex lanthanide sulfides and the layer misfit compounds. Through the entire range of structures and compositions the relative plasticity (ability for minor adjustments) of large coordination polyhedra created around large or lone-electron-pair cations is of primary importance in the interlayer and interblock adjustments. 

Figure 16. Interlayer match of pseudotetragonai (Q) and orthohexagonal (H) submesh in (a) layer misfit compound (LaS)./ 2(pi S2 (i.e., "-LaCrS/) and (b) in the lanthanide sulfide ErgLa.f( 27 match analogous to that in cannizzarfte.

Fig. 18. The excitation energies from the divalent to the tri valent state (AjEhui) for some lanthanide sulfides (Mdrtensson et al. 1982). The open points are from the data in fig. 16, the full points are interpolated using the data for the metals (Lang et al. 1981).

The simplest argument that TmS is trivalent, TmSe intermediate valent and TmTe divalent under normal conditions comes from comparing the lattice constants of the lanthanide sulfides, selenides and tcllurides as shown in fig. 58 (after Bucher et al. 1975). The lanthanide contraction is the cause for the general trend in the curves and the standard divalent Sm, Eu and Yb ions with their larger ionic radius are the obvious deviations. TmTe lies on the divalent curve, TmS on the trivalent one and TmSe is intermediate and by linear interpolation between a hypothetical divalent and trivalent TmSe one obtains a valency of 2.75. The figure also shows that SmS, in this case by pressure or trivalent rare earth doping, can be intermediate valent, TmSe, in this case by stoichiometry variation, can become trivalent and TmTe, in this case by pressure, oxidation and stoichiometry variation, can become intermediate valent. 

Most of the methods of synthesizing lanthanide sulfides involve high-tempera-ture gas-solid reactions between a sulfurizing agent (H2S and/or CS2) and lanthanide precursors at high temperatures or under high pressures ... 

Fig. 3. Dependence of multiphonon relaxation on the number of phonons in the glass former needed to bridge the energy gap between the luminescent /-level and the closest lower-lying level. The curves refer to glasses of the following types (1) phosphate (2) borate (3) silicate (4) tellurite (5) fluoroberyllate (6) germanate (7) zirconium fluoride (ZBLA) (8) aluminum lanthanide sulfide (ALS) and gallium lanthanide sulfide (GLS) (9) the crystalline hosts YjAljOj CYAG), and (10)...

Solid Compounds. The tripositive actinide ions resemble tripositive lanthanide ions in their precipitation reactions (13,14,17,20,22). Tetrapositive actinide ions are similar in this respect to Ce . Thus the duorides and oxalates are insoluble in acid solution, and the nitrates, sulfates, perchlorates, and sulfides are all soluble. The tetrapositive actinide ions form insoluble iodates and various substituted arsenates even in rather strongly acid solution. The MO2 actinide ions can be precipitated as the potassium salt from strong carbonate solutions. In solutions containing a high concentration of sodium and acetate ions, the actinide ions form the insoluble crystalline salt NaM02(02CCH2)3. The hydroxides of all four ionic types are insoluble ... 

The chlorides, bromides, nitrates, bromates, and perchlorate salts ate soluble in water and, when the aqueous solutions evaporate, precipitate as hydrated crystalline salts. The acetates, iodates, and iodides ate somewhat less soluble. The sulfates ate sparingly soluble and ate unique in that they have a negative solubitity trend with increasing temperature. The oxides, sulfides, fluorides, carbonates, oxalates, and phosphates ate insoluble in water. The oxalate, which is important in the recovery of lanthanides from solutions, can be calcined directly to the oxide. This procedure is used both in analytical and industrial apptications. 

Oxides (Ln Oj), fluorides (LnF ), sulfides (Ln S, LnS), sulfofluorides (LnSF) of lanthanides are bases of different functional materials. Analytical control of such materials must include non-destructive methods for the identification of compound s chemical forms and quantitative detenuination methods which does not require analytical standards. The main difficulties of this analysis by chemical methods are that it is necessary to transform weakly soluble samples in solution. 

Kolis et al. reported the synthesis of some metal sulfide salts of homolep-tic lanthanide ammine complexes using supercritical ammonia as a reaction medium (Scheme 12) [49]. They proposed that these reactions proceed via a... 

The structural chemistry of the actinides is often similar to that of lighter transition metals, such as Zr and Hf, and to that of the lanthanides however, the diffuse nature of the 5/ orbitals leads to some differences and specifically to interesting magnetic and electrical properties. The actinide sulfides are generally isostructural with the selenides, but not with the analogous tellurides. The binary chalcogenides of uranium and thorium have been discussed in detail [66], but the structural... 

The synthesis of a series of chiral organophosphine oxide/sulfide-substituted binaphtholate ligands has recently been reported by Marks and Yu and their corresponding lanthanide complexes characterized. These complexes, generated in situ from Ln[N(TMS)2]3, cleanly catalysed enantioselective intramolecular hydroamination/cyclisation of 1-amino-2,2-dimethyl-4-pentene albeit with a low enantioselectivity of 7% ee (Scheme 10.82). 

Many difluondes and dioxides arc found with the fluonie structure Examples are the fluorides of Ca, Sr, Ba, Cd, Hg, and Pb, and the dioxides of Zr, lit, and some lanthanides and actinides, ff the numbers and positions or the cations and anions are reversed, one obtains the antifluorite structure which is adopted by the oxides and the sulfides of Li, Na, K, and Rb. 

Studied through the use of tracer quantities, the chemical properties of californium indicate that its chemical properties are analogous to those of the tripositive actinides and lanthanides, showing the fluoride and the oxalate to be insoluble in acid solution, and the halides, perchlorate, nitrate, sulfate and sulfide to be soluble. 

The other lanthanide compounds in this series were prepared either by a similar method as above or alternately by a polymerized complex method using Ti(OiPr)4 and Ln(NC)3) 6I I2O to yield the lanthanoid titanate precursor which was subsequently sulfided in a flowing H2S atmosphere.485 The Sm2Ti2S20s compound was... 

These complexes are the first examples of multifunctional catalysts and demonstrate impressively the opportunities that can reside with the as yet hardly investigated bimetallic catalysis. The concept described here is not limited to lanthanides but has been further extended to main group metals such as gallium [31] or aluminum [32]. In addition, this work should be an incentive for the investigation of other metal-binaphthyl complexes to find out whether polynuclear species play a role in catalytic processes there as well. For example, the preparation of ti-tanium-BINOL complexes takes place in the presence of alkali metals [molecular sieve ( )]. A leading contribution in this direction has been made by Kaufmann et al, as early as 1990 [33], It was proven that the reaction of (5)-la with monobromoborane dimethyl sulfide leads exclusively to a binuclear, propeller-like borate compound. This compound was found to catalyze the Diels-Alder reaction of cyclopentadiene and methacrolein with excellent exo-stereoselectivity and enantioselectivity in accordance with the empirical rule for carbonyl compounds which has been presented earlier. 

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