Rare-earth complexes with other organic ligands

4 Rare-earth complexes with other organic ligands 

Using bulky ligands or chelating ligands to saturate the complexes coor-dinatively or sterically, the rare-earth complexes without n ligands have been obtained and characterized. The La and Sm complexes with bulky alkyl ligands 

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The lanthanides form many compounds with organic ligands. Some of these compounds ate water-soluble, others oil-soluble. Water-soluble compounds have been used extensively for rare-earth separation by ion exchange (qv), for example, complexes form with citric acid, ethylenediaminetetraacetic acid (EDTA), and hydroxyethylethylenediaminetriacetic acid (HEEDTA) (see Chelating agents). The complex formation is pH-dependent. Oil-soluble compounds ate used extensively in the industrial separation of rate earths by tiquid—tiquid extraction. The preferred extractants ate catboxyhc acids, otganophosphoms acids and esters, and tetraaLkylammonium salts. 

The first stage of oirr work was the synthesis of lanthanide elements salts (ytterbium and erbium) in a form of acetylacetonates. The rare-earth elements (REE) complexes in most cases have the coordination number (CN) more than six (7, 8, 9, 10 and even 12). CN of REE ions in complexes with organic poly dentate ligands are high and variable [10]. The reason of this phenomenon lies in the big ionic radius, which decreases from 1.06 A (La " ) to 0.88 A (Lu " ) (the effect of lanthanide compression ). The empty site of the coordination sphere is occupied by other ligands water, hydroxyl ions, etc. In IR-spectrum the hydroxyl ion is characterized by a narrow strip at 3700-3600 cm, it has higher frequency than water. Frequency v of water is located in a region of about 3600-3200 cm". ... 

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