Lanthanides chloride

Table 8. Acute Lethal Doses of Lanthanide Chlorides for Mice...

The sohds are treated with hydrochloric acid at 70°C at pH 3—4. The thorium hydroxide [13825-36-0] remains iasoluble and can be filtered off. Small amounts of trace contaminants that carry through iato solutioa, such as uranium and lead as well as some thorium, are removed by coprecipitation with barium sulfate ia a deactivatioa step. The resultiag product, after SX-removal of the heavy La fractioa, is a rare-earth/lanthanide chloride,... 

Mischmetal. Mischmetal [62379-61-7] contains, in metallic form, the mixed light lanthanides in the same or slightly modified ratio as occurs in the resource minerals. It is produced by the electrolysis of fused mixed lanthanide chloride prepared from either bastnasite or mona2ite. Although the precise composition of the resulting metal depends on the composition of chloride used, the cerium content of most grades is always close to 50 wt %. 

At this stage, the influence of several lanthanide salts was evaluated (Figure 35.2) (19). In the presence of lanthanide nitrates, the conversion and the selectivity towards 1,3-PDO decreased compared to the reference, i.e., the reaction run without any additives, except H2WO4. In contrast, the addition of lanthanide chlorides had a positive effect on the selectivity to 1,3-PDO. However, low conversions were observed in all cases. Under these conditions, the highest ratio l,3-PDO/l,2-PDO reached 0.9. 

Table 2—Solubility of lanthanide chlorides, sulfates, and hydroxides and the pH at which the hydroxides precipitate from solutions ...

Most lanthanide compounds are sparingly soluble. Among those that are analytically important are the hydroxides, oxides, fluorides, oxalates, phosphates, complex cyanides, 8-hydroxyquinolates, and cup-ferrates. The solubility of the lanthanide hydroxides, their solubility products, and the pH at which they precipitate, are given in Table 2. As the atomic number increases (and ionic radius decreases), the lanthanide hydroxides become progressively less soluble and precipitate from more acidic solutions. The most common water-soluble salts are the lanthanide chlorides, nitrates, acetates, and sulfates. The solubilities of some of the chlorides and sulfates are also given in Table 2. 

Moeller and Vicentini (48) have reported the complexes of DMA with lanthanide perchlorates in which the number of DMA molecules per metal ion decreases from eight for La(III)—Nd(III) to six for Tm(III)—Lu(III).apparently due to the decrease in the cationic size. The complexes of the intermediate metal ions have seven molecules of DMA in their composition. Complexes of lanthanide chlorides with DMA (49, 50) exhibit a decrease in L M from 4 1 to 3 1 through 3.5 1. These complexes probably have bridging DMA molecules. The corresponding complexes with lanthanide iodides (51), isothiocyanates (52), hexafluorophosphates (57), nitrates (54, 55), and perrhenates (49, 56) also show decreasing L M with decreasing size of the lanthanide ion. However, complexes of DMA with lanthanide bromides (55) do not show such a trend. Krishnamurthy and Soundararajan (41) have reported the complexes of DPF with lanthanide perchlorates of the composition [Ln(DPF)6]... 

A number of complexes of urea and substituted ureas with various lanthanide salts have been isolated. The lanthanide acetates give both anhydrous and hydrated complexes with urea (67, 68). The hydrated complexes could be dehydrated by drying the complexes over CaCl2 or P4Oi0 (68). It is interesting to note that in the complexes of substituted ureas like EU (70) and CPU (71), the L M is independent of the anion. The anions in these complexes with a L M of 8 1 are apparently nonco-ordinated. Seminara et al. (72) have reported complexes of lanthanide chlorides with DMU and DEU which contain five and three molecules of the ligand respectively per... 

With the lanthanide chlorides, tris-DMP complexes were obtained (99) in which all the chlorides are supposed to be coordinated. 

Oximes can act both as anionic and neutral ligands. Complexes of Box (134), DBox (135), Fox (136), BMox (137) and DAMox (138) with lanthanide chlorides have been reported. These oximes act as bidentate ligands coordinating through the oxygen of the C=0 or the C-O—H group and the oxime group. 

By changing the method of preparation, complexes of the formula Ln(Py0)3(N03)3, in which all the nitrates are coordinated to the lanthanide ion in a bidentate fashion, could be prepared (152). PyO yields complexes with lanthanide chlorides (156), bromides (156), iodides (157) and hexathiocyanatochromate (159) all of which have a L M of 8 1. However, by changing the synthetic procedure, Sivapullaiah and Soundararajan (158) could prepare complexes of the formula [Ln(PyO)6 Br2(H20)2]Br... 

Complexes of lanthanide chlorides 156,173), bromides (256), and iodides 174) with 2,6-DMePyO have also been prepared and characterized. The presence of bridging 2,6- DMePyO molecules has been suggested in the complexes of lanthanide iodides. Vicentini and De Oliveira (2 73) have reported tetrakis-2,6-DMePyO complexes with lanthanide nitrates. However, by changing the method of synthesis, tris-2,6-DMePyO complexes with the lanthanide nitrates could be prepared in this laboratory (252). All the nitrate groups in the tris-2,6-DMePyO complexes are bidentate. In the 2,4,6-TMePyO complexes (252) also the nitrate groups are coordinated to the lanthanide ion in a bidentate fashion. 

Complexes of PyzO with lanthanide perchlorates (2 79) and hexafluorophosphates 180) are eight coordinate. However, La(III) perchlorate gives the complex La(Pyz0)7(C104)3 2 H20 in which both the water molecules are coordinated to La(III). In the case of complexes of PyzO with lanthanide chlorides 180), the number of coordinated ligands increases as the ionic radius of the lanthanide ion decreases. These complexes probably contain bridging ligands. 

Since 1972, complexes of lanthanides with cyclic sulfoxides have received considerable attention. Zinner and Vicentini (261) have reported the complexes of lanthanide perchlorates with TMSO. The L M in these complexes decreases along the lanthanide series. But in the case of complexes of lanthanide chlorides with TMSO, the L M increases from 2 1 for the lighter lanthanides to 3 1 for the heavier lanthanides (262). It has been suggested that these complexes, especially the bis-TMSO complexes, contain bridging chloride ions. Tetrakis-TMSO complexes with lanthanide isothiocyanates have also been reported (263). 

In the complexes of TBPO with lanthanide perchlorates, absorptions at 400 cm-1 have been ascribed to i>Ln o (210). Absorptions due to lanthanide-perchlorate vibrations (Ln—OC103) have been identified in the region 290—360 cm-1 for the complexes of lanthanide perchlorates with 2,6-DMePyO (171), TBPO (210), DMMP (210), and for the complexes of Ce(III) perchlorate with TPPO and TBPO (206, 211). Ln-Cl vibrations occur at 230 cm-1 in the complexes of lanthanide chlorides with TBP (195) and TPPO (202). In the complexes of lanthanide bromides with TBP (295), i Ln— Br occurs in the region of 195 cm-1. 

The anions in the complexes of DMSO and DMF with lanthanide chlorides are coordinated (43, 252). In DMF both these series of complexes behave as 1 1 electrolytes showing the presence of one replaceable chloride ion. This chloride is probably weakly bound compared to the other two chloride ions. These results were explained by assuming the presence of bridging chloride ions in these complexes. Results obtained for the complexes of TMSO with lanthanide chlorides have been explained in a similar fashion (262). 

Aliphatic and aromatic carboxylic esters are also directly converted, in one step, to oxazolines using amino alcohols. As expected, harsh conditions are required for this transformation. Typically, the reaction is performed in refluxing xylene in the presence of catalytic quantities of a Lewis acid such as dibromo- " or dichloro-dimethylstannane. More recently, lanthanide chloride and samarium chloride have also been reported as useful catalysts for this one-pot transformation in refluxing toluene. Representative examples are shown in Table 8.2 (Scheme 8.2). ... 

Chaumont, A., Wipff, G. (2004), M3+ Lanthanide Chloride Complexes in "Neutral" Room-Temperature Ionic Liquids. A Theoretical Study, J. Phys. Chem A 108, 3311-3319. 

In spite of the wealth of information available on the preparative and structural aspects of the lanthanide chlorides (1-3), experimental thermodynamic, and, in particular, high-temperature vaporization data are singularly lacking. The comprehensive estimates of the enthalpies of fusion, vaporization, heat capacities and other thermal functions for the lanthanide chlorides by Brewer et ah (4, 5) appear internally consistent, but the relatively few experimental measurements (6-/2) do not permit confirmation of the estimates due to the narrow temperature ranges of study. Additionally, the absence of accurate molecular data for the gaseous species has hampered third-law treatment of the limited experimental vapor pressure data available. The one reported study (12) of the vaporization of EuC12 effected by a boiling-point method lacks accuracy for these reasons. 

A careful review of all experimental data for the lanthanide chlorides, bromides and iodides, mainly made by solution calorimetry, has been made by Cordfunke and Konings (2001b) recently, who evaluated data from the literature between 1940 and 2000. The tables of this work are reproduced in Appendix B, corrected for some small errors. The present section summarises the justification of the selected values. 

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