Rare earth complexes acetylacetone

Raman spectroscopy metal in water complexes, 309 Rare earth complexes acetylacetone synthesis, 377 guanidinium, 282 hydroxamic acids, 506 Redox properties bipyridyl metal complexes, 90 Reductive coupling nitrile metal complexes, 265 Resorcinol, 2,4-dinitro-metal complexes, 273 Rhenium complexes acetylacetone, 376 synthesis, 375, 378... 

Extraction of the rare earths with acetylacetone has been investigated [418, 419] and is found to be enhanced by the decreasing basicity of the rare earth ions. The gas chromatographic separation of rare earth complexes with 2,2,6,6-tetramethyl-3,5-heptanedione has already been mentioned. The acetylacetonate complexes of the rare earths are reported to exist as either anhydrous [420, 421], mono- [422], di- [422] or trihy-drates [422, 423], Stites et al. [424] have studied the pH of the precipitation of several rare earth acetylacetonates and reported the melting points of the complexes. The europium acetylacetonate precipitated at pH 6.5, and melted at 144—45° C. The existence of monomers and dimers for these complexes in nonaqueous solvents has been proposed [421, 425-427],... 

The ionization energy values for rare earth complexes with acetylacetone (acac) and M(dpm)3 are given in Table 9.8. Photoelectron spectra showed covalency of M-L bonds in the order SCL3 > LUL3 > YL3. This order is based on the fact a2(n )-e(n ) splitting and ionization energies of n orbitals decreased in the same order. 

The complex Tb(TTFA) (o-phen) with TTFA = thenoyltrifluoroaceto-nate is a octacoordinate rare earth chelate which contains one o-phen and three TTFA ligands (45-46). The latter are related to acetylacetonate. 

Table 33. Stability constants of the acetylacetonate complexes of the rare earths [429] (p = 0.1 at 30° C)...

Acetylacetonates. — The p-diketonate complexes of the trivalent rare earths are among the more stable of the complex species. The general... 

Scandium can also be separated from rare-earth and other metals by extraction as a complex of HTTA [8,9], or salicylate [10]. Xylene [8], CHCI3 [9], and mesityl oxide [10] have also been used for extraction of Sc. Scandium has been extracted from ascorbic acid medium with Aliquat 336S [11], or with acetylacetone in the presence of 3,5-dichlorophenol [12]. Macrocyclic ethers have also been used for extraction of Sc [13]. 

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". ... 

Saitoh et al. [152] separated seven rare-earth ions (Nd(III), Gd(III), Tb(III), Dy(ni), Ho(ni), Er(III), Lu(III)) as their tetraphenylporphine complexes using a C 8 column (2 = 555 nm) and a 90/10 methanol/water (0.5% acetylacetone with 0.68% triethylamine) mobile phase. Injections of 10 pL of 0.1 mM metal-complex solutions were made. The Nd(III) complex was stable for less than one hour in any of the solvents methanol, acetone, acetonitrile, or dichloromethane. Elution was complete in <15 min. Similarly, the tetraphenylporphine complexes of VO(IV), Cu(II), Ni(II), Zn(II), and Pd(II) were resolved on a C g column (X = 420nm) using a metha-nol/octane mobile phase where octane was present at less than 0.1 mole fraction [153]. (It should be noted that 0.1 mole fraction octane is equivalent to 21% in methanol.) A 1 pL injection of a standard containing 4 x 10 M metal complex was readily detected. 

Metal acetylacetonates are covalently bound by the reaction of crosslinked chloromethyl-ated polystyrene (DMF, 100 °C) under formation of 7 [104]. Rare earth Eu(III)-complexes of l-carboxy-8-naphthoyl bound covalently at polystyrene 8 are obtained by Friedel-Crafts acylation of the corresponding naphthalenetetracarboxylic acid anhydride with the polymer followed by reaction with Eu [105]. The luminescence properties of lanthanide ions with polycarboxylates were investigated in detail [106]. The effects of the conformation of polymer chains on electron transfer and luminescence behaviour of Co(II)-, Co(III)-ethylenediamine complexes at polycarboxylates were studied [107]. 

The above mentioned impregnated layers suffer from the limitations such as (a) the impregnants are eluted to some extent by the mobile phases used and (b) the stripping of liquid stationary phase from the support by incompatible mobile phases. To overcome these problems, chemically bonded layer materials of similar properties were developed for safer use as stationary phase. Lipophilic Cjg bonded silica gel phases with polar aqueous mobile phases were used for reversed-phase TLC of rare earth elements (52,54,56) and organometallics (180). Lanthanide complexes of tetraphenyl porphine are resolved on layers made of aminopropyl silica gel (NH2) and octadecyl silica gel (Cjg) using methanol-water-acetylacetone-diethylamine in different proportions from the mobile phase (162). 

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