Lanthanide halide complexes

Vapor Phase Spectroscopy of Complex Lanthanide Halide-Aluminum Halide Molecular Species, W.T. Camall, J.P. Hessler, C.W. Williams, and H.R. Hoekstra, J. Mol. Struct. 46, 269-284 (1978). 

Lanthanide halide complexes free of coordinated Lewis bases, such as alcohols, phosphates, amines, dimethylsulfoxide, or THF, suffer from low solubilities in non-coordinating solvents. Therefore, catalytic systems based on LnCl3 generally require preformation or aging in order to reach maximum activities. In contrast, lanthanide tetrahalogenoaluminate complexes are soluble in aromatic solvents. Such simple Ln/Al heterobimetallic halide... 

Many studies on the absorption spectra of lanthanides in alcoholic media have been made and the observations and anomalies have been explained in terms of entry of a chloride ion into the coordination sphere of the lanthanide ion. The composition and stability of halide complexes of lanthanides in alcohol and aqueous alcoholic solutions have been studied by spectral techniques. The halide ions have been found to cause marked changes in the spectra of lanthanides in alcoholic and aqueous media. The observed spectral changes may be attributed to changes in the immediate coordination environment of the lanthanide ion [223]. 

The. applications of ion-exchange chromatography are exemplified by the selection shown in table 4.18. Among the most notable are the separation of lanthanides and actinides using a citrate, lactate or EDTA eluting agent the separation of many metals as halide complexes on anionic resins and the separation of amino-acids with citrate buffers. The use of pressurized systems for complex mixtures is likely to become more widespread in the future. 

Hydrates of the oxoanion and halide complexes are numerous and are mostly isostructural with the hydrated lanthanide chlorides. In the hydrated salicylate, AmL3 H20, one water molecule is in the inner coordination sphere of the Am cation. The hydrated xenate(VIII), Am4(XeO6)3 40H2O, has also been reported. 

Hydrates of the oxoanion and halide complexes are numerous for Am and Cm and a few have also been reported for Bk and Cr . The hexahydrate trichlorides and tribromides, AnCl3 6H20 (An = Am or Bk) and AnBr3 6H20 (An = Am or Cf), are isostructural with the hydrated lanthanide chlorides and involve mixed ligand complexes, such as [AnCl2(H20)6]". ... 

Varying the ligand, L in the initial component LnHal3 3L does not change the microstructure of the polybutadiene formed [14]. Nevertheless, the analysis of propagation rate constants shows that active centres in catalytic systems on the basis of TBP and diamyl sulfoxide complexes of the same halide of lanthanide are different [14]. 

The synthesis of lanthanide and actinide compounds was the subject of a book (Meyer and Morss 1991). Detailed information is given on the synthesis of lanthanide fluorides (Muller 1991), binary lanthanide halides, RX3 (X=Cl,Br,l) (Meyer 1991a), complex lanthanide(in) chlorides, bromides and iodides (Meyer 1991b), and on two alternative routes to reduced halides, the conproportionation route (Corbett 1991) and the action of alkaU metals on lanthanide(lll) halides (Meyer and Schleid 1991). Therefore, a brief outline of the main preparative routes and synthetic strat es might be sufficent. 

Additional areas of lanthanide halide chemistry that have been reviewed include the synthesis, phase studies, and structures of complex lanthanide halides - compounds formed between one or more group 1 cation and lanthanide element halides (Meyer 1982). Halides in combination with lanthanide elements in the II, III, and IV oxidation states were considered with the chemistry of the heavier halides being emphasized. More recently the reduced ternary lanthanide halides (Meyer 1983) and the reduced halides of the lanthanide elements were reviewed (Meyer 1988). The latter review considered lanthanides in which the formal oxidation state of the cation was 2 and included hydride halides, oxide halides, mixed-valence ternary halides, and reduced halide clusters. Corbett et al. (1987) discussed the structures and some bonding aspects of highly reduced lanthanide halides and compounds stabilized by a second-period element bound within each cluster, e.g., SC7CIJ2B, SC5CI5B, YjCljC. 

Divalent lanthanide halide complexes studied by absorption spectroscopy involve the Sm(II)-Al-Cl and Eu(II)-Al-Cl vapor complexes. The data are interpreted by the presence of EuAljCln and EuAUCIh vapor molecules (Sorlie and 0ye 1978) while the stoichiometries of the SmCla-AlC vapor complexes are not known (Papatheodorou and Kucera 1979). Spectra of divalent lanthanides are expected to exhibit weak Laporte-forbidden 4f <— 4f transitions and relatively strong bands arising from 5d 4f, 6s <— 4f,. .. transitions. Such transitions are observed in the near-UV region in spectra of both Sm(II)-Al-Cl and Eu(II)-Al-Cl vapor complexes (figs. 12 and 13). 

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