Erbium halides

Holmium is obtained from monazite, bastnasite and other rare-earth minerals as a by-product during recovery of dysprosium, thulium and other rare-earth metals. The recovery steps in production of all lanthanide elements are very similar. These involve breaking up ores by treatment with hot concentrated sulfuric acid or by caustic fusion separation of rare-earths by ion-exchange processes conversion to halide salts and reduction of the hahde(s) to metal (See Dysprosium, Gadolinium and Erbium). 

The isostructural solutions formed by yttrium(III) and erbium(III) have been used to study the structures of their halide complexes in aqueous solutions at different concentrations (35). The RDFs for some erbium(III) bromide and chloride solutions with different metal ion concentration and halide to metal ratios are given in Fig. 20 after elimination of the nonmetal interactions. For comparison those of three perchlorate solutions of similar concentrations are also given. For all of these solutions the peaks at 2.35 A, which correspond to the inner coordination sphere of the metal ion, are nearly the same and are closely reproduced by a theoretical peak calculated for 8.0 Er-H20 interactions. This indicates that the anions do not penetrate the first... 

Among seven-coordinate structures, many involve dike-tonate complexes Ln(diket)3 L these generally have either capped-octahedral or capped trigonal prismatic geometry. A considerable number of complexes with neutral donors (e g. thf) of the type LnX3L4 (X = halide, NCS), however, have structures closest to pentagonal bipyramidal, similarly found in the erbium perchlorate complex with 2,6-dimethyl-4-pyrone (Section 3.7.4). 

Since no accurate vapor pressure data are available for the erbium and thulium hahdes, the molar absorptivities were determined directly from a weighed amount of the respective rare-earth halides. Good results could be obtained from this method if the respective halogen, bromine, or iodine were added to the cell such that its pressure at 1000°C. was 1 atm. This procedure greatly reduced the reaction of the rare-earth... 

Iodine cleaves one erbium-cyclopentadienyl bond in tricyclopentadienyl erbium with formation of pink dicyclopentadienyl erbium iodide (Maginn et al., 1963), and the tricyclopentadienyl complexes of neodymium and ytterbium are cleaved by hydrogen cyanide with formation of the corresponding dicyclopentadienyl lanthanide cyanide (Kanellakopulos et al., 1974). The colors and some physical data of the cyclopentadienyl rare earth halides and cyanides are given in table 4. 

The pink erbium derivative [Cp2ErCsCCMc3]2 was synthesized by the halide-free reaction of [Cp2ErMe]2 with HC=CCMc3 in THF solution (Atwood et al. 1981). Its X-ray structural analysis confirms the dimeric formulation. 

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