Acetylacetonate complexes lanthanide

After our report, many other examples of SIMs based on mononuclear lanthanide complexes have appeared. As relevant examples, we should mention the erbium-organometallic double-decker complexes [11] and the dysprosium-acetylacetonate complexes [12], and the dysprosium-DOTA (H4DOTA, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) complexes reported by Sessoli etal. [13]. 

Fig. 4.15 The system La(III) acetylacetone (HA) - IM NaC104/benzene at 25°C as a function of lanthanide atomic number Z. (a) The distribution ratio Hl (stars, right axis) at [A ] = 10 and [HA] rg = 0.1 M, and extraction constants (crosses, left axis) for the reaction Ln + 4HA(org) LnA3HA(org) + 3FE. (b) The formation constants, K , for formation of LnA " lanthanide acetylacetonate complexes (a break at 64Gd is indicated) circles n = 1 crosses n = 2 triangles w = 3 squares w = 4. (c) The self-adduct formation constants, for the reaction of LnA3(org) + HA(org) LnA3HA(org) for org = benzene. (A second adduct, LnA3(HA)2, also seems to form for the lightest Ln ions.) (d) The distribution constant Ajc for hydrated lanthanum triacetylacetonates, LnAs (H20)2 3, between benzene and IM NaC104. (From Ref. 28.)...

Mn(II) > Mg(II).270 It should be underlined that titanium and zirconium alkoxides are efficient catalysts for both stages of reaction. Lanthanide compounds such as 2,2/-bipyridyl, acetylacetonate, and o-formyl phenolate complexes of Eu(III), La(III), Sm(III), Er(III), and Tb(III) appear to be even more efficient than titanium alkoxides, Ca or Mn acetates, Sb203, and their mixtures.273 Moreover, PET produced with lanthanides has been reported to exhibit better thermal and hydrolytic stability as compared to PET synthesized with the conventional Ca acetate -Sb203 catalytic system.273... 

Qi M-H, Liu G-F (2004) Synthesis and photoelectronic properties on a series of lanthanide dysprosium(III) complexes with acetylacetonate and meso-tetraalkyltetrabenzoporphyrin. Solid State Sci 6(3) 287-294... 

A broad range of metal centers have been used for the complexation of functional ligands, including beryllium [37], zinc, transition metals such as iridium [38], and the lanthanide metals introduced by Kido [39], especially europium and terbium. Common ligands are phenanthroline (phen), bathophenanthrolin (bath), 2-phenylpyridine (ppy), acetylacetonate (acac), dibenzoylmethanate (dbm), and 11 thenoyltrifluoroacetonate (TTFA). A frequently used complex is the volatile Eu(TTFA)3(phen), 66 [40]. 

ATdc values for the lanthanide acetylacetonates are the reverse from that expected for the size effect. The explanation is hkely that the neutral complex with the formula LnAs is coordinatively unsaturated, which means that a hydrated complex exists in the aqueous phase (possibly also in the organic phase). The more coordinatively unsaturated lanthanide complexes (of the larger ions) can accommodate more water and thus are more hydrophilic. The result is a A dc several orders of magnimde lower for the lightest. La, than for the heaviest, Lu. 

However, even this simplified formula does not justify the use of the ratio of stability constants of the extracted complexes as the only measure of selectivity of extractive separations. Such a widely used approach is obviously based on an implicit assumption that the partition constants of neutral complexes ML of similar metal ions are similar, so that their ratio should be close to unity. This is, however, an oversimplification because we have shown that the ifoM values significantly differ even in a series of coordi-natively saturated complexes of similar metals [92,93]. Still stronger differences in the values have been observed in the series of lanthanide acetylacetonates, due to different inner-sphere hydration of the complexes (shown earlier), but in this case, self-adduct formation acts in the opposite direction [100,101] and partly compensates the effect of the differences in. Tdm on S T(see also Fig. 4.15). Such compensation should also be observed in extraction systems containing coordinatively unsaturated complexes and a neutral lipophilic coextractant (synergist). 

Many metal / -diketonates are coordinatively unsaturated and reactions with Lewis bases to form complexes are a pervasive feature of their chemistry.14 In previous sections, base cleavage of M—O—M bridge bonds in oligomeric acetylacetonates and formation of hydrated lanthanide dike-tonates having high, odd coordination numbers have been noted. Mechanistically, acid-base complexes are quite likely to be involved in hydrolysis, displacement and ort/zo-metallation reactions, albeit that the interactions may be weak. 

Lanthanide aryloxides have proved to be excellent precursors to homoleptic lanthanide alkyls (B, Eq. 13) [140], The reaction can be conducted in non-polar solvents because of the good solubility of the starting compounds. The formation of insoluble alkali metal aryloxides is the driving force (kinetic control). Complexes derived from aliphatic alcohols [141] and acetylacetonates [131] are... 

Fig. 5. Sublimation behavior of various lanthanide complexes at 10 3 mbar (OEP = 2, 3, 7, 8,12, 13, 17, 18-octa(ethyl) porphyrin acac = acetylacetonate)...

In the process of lanthanide complex formation with the porphyrins, the ligand loses two protons and yields lanthanide hydroxy porphyrin or lanthanide porphyrin X, where X = C1, Br, NOJ, etc. Many lanthanide complexes with substituted porphyrins have been prepared by heating a mixture of porphyrin and the lanthanide salt in imidazole melt in the range 210-240°C. When the complex formation is complete the solvent (i.e.) imidazole is eliminated by either sublimation [81] or by dissolution of the mixture in benzene, followed by washing with water [82]. Further purification requires column chromatography. The starting material can be anhydrous lanthanide chloride or hydrated lanthanide acetylacetonate. After purification the final product tends to be a monohydroxy lanthanide porphyrin complex. 

Complexes of lanthanide nitrates with Schiff derivatives of acetylacetone, 2,4-pentan-edioneanil, and 2,4-pentanedionebenzylamine of the formula [Ln(L-LH)3(N03)](N03)2, where Ln = lighter lanthanides and [Ln(L-LH)2(N03)](N03)2, where Ln = Yb have been isolated from acetone and characterized [256]. In these complexes the ligand does not lose a proton and is in neutral form. In the case of the ligand bisalicylaldehydeethylenediamine, lanthanide complexes are formed with the loss of a phenolic proton [249]. 

Mixed complexes of lanthanides with substituted porphyrin and acetylacetone ligands were characterized by UV-Vis, IR, NMR, XPS and conductivity [55]. XPS data are given... 

Figure 4.42. Molecular structures of commonly used CVD precursor classes. Shown are (a) metal p-diketonate (acetylacetonate, acac) complex to grow a metal oxide film (H2 as the coreactant gas yields a metal film) (b) a heteroleptic (more than one type of ligand bound to the metal) p-diketonate complex to yield a Cu film the ancillary ligand helps prevent oligomerization, enhancing volatility (c) various types of complexes to deposit metallic, oxide, nitride, or oxynitride films (depending on coreactant gas(es) used - respective ligands are p-ketoiminato, p-diketiminato, amidinato, and guanidinato (d) a metal azolato complex commonly used to deposit lanthanide metal thin films.

Acetylacetonate and substituted acac derivatives are attractive because of their versatility and stability under normal conditions, as well as their ability to deposit metals cleanly under relatively mild conditions . The dipivaloylmethanato (dpm) derivative from stable and volatile lanthanide compounds, e.g. Lu(dpm)3, have in the gas phase D3 symmetry of the coordination polyhedron. According to Kepert s model, bidentate ligands can be approximated by diatomic molecules and it is completely predictable for the structures of these complexes in the gas phase, but the solid-state structures might be different. 

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