Weakly acetylacetone

The chemical structure of a typical divalent metal acetylacetonate, for which the abbreviation would be MCacac). These compounds are internally bonded ionically and complexed to oxygen at the same time. Thus, their intramolecular forces are very strong (they are stable), but their interraolecular forces are weak (they are volatile). 

Solvent extraction has become a common technique for the determination of formation constants, P , of aqneons hydrophilic metal complexes of type MX , particularly in the case when the metal is only available in trace concentrations, as the distribntion can easily be measnred with radioactive techniques (see also section 4.15). The method reqnires the formation of an extractable complex of the metal ion, which, in the simplest and most commonly used case, is an nn-charged lipophilic complex of type MA. The metal-organic complex MA serves as a probe for the concentration of metal ions in the aqueous phase through its equilibrium with the free section 4.8.2. This same principle is used in the design of metal selective electrodes (see Chapter 15). Extractants typically used for this purpose are P-diketones like acetylacetone (HAA) or thenoyltrifluoroacteone (TTA), and weak large organic acids like dinonyl naph-talene sulphonic acid (DNNA). 

The weak nucleophilic nature of polynitroaliphatic alcohols is also reflected in their slow reactions with isocyanates to yield carbamates. These reactions often need the presence of Lewis acids like ferric acetylacetonate or boron trifluoride etherate. The reaction of bifunctional isocyanates with polynitroaliphatic diols has been used to synthesize energetic polymers.33°... 

Group VI Donors. Oxygen donor ligands. A series of unsymmetrical tris-(P-diketonato)M " complexes (17) has been investigated in order to establish CIS—trans isomer distributions, and relative rates of isomerization. Included in this study was the preparation and separation of the geometric isomers of [Ru(tfac)3] and [Ru(bzac)3] (tfac = trifluoroacetylacetone, bzac = benzoyl-acetylacetone). In weakly polar media, the trans-isomer of [Ru(tfac)3] was found to be more stable, whereas the isomer distribution of similar complexes with R, R = alkyl or Ph, is statistical. ... 

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. 

The hydroxo complexes behave as strong bases in aqueous organic solvents and react with weak acids, including carbon acids such as nitromethane, methyl ketones, acetylacetone, acetonitrile, phenylacetylene and cyclopentadiene this provides a useful synthesis under mild conditions of platinum(II)-carbon a-bonded complexes, as exemplified in Equation 6 (18) ... 

Chelating extractants such as beta-diketones, tropolones, hydroxyoximes, and 8-hydroxyquinolines (Figure 2.1), have been used extensively for the extraction of actinide ions from moderate to weakly acidic solutions (15-17). Beta-diketones such as acetylacetone (acac), HTTA, benzoyl trifluoroacetone (BTFA), and dibenzoyl-methane (HDBM) have been commonly used for the separation of actinide ions. The extraction mechanism involved formation of the enol form of the beta-diketone prior to complexation and extraction of the metal ion (Figure 2.2). 

He(I) photoelectron spectra of lanthanum tris-yS -diketonate complexes have been studied and the spectra interpreted on the basis of quantum chemical calculations of ground and ionized states by X -DV and ab initio methods [54]. The comparative analysis of the photoelectron spectra of Sc, and Lu tris-acetylacetonates showed that substitution of one oxygen atom by NH group shifts the two pairs of n and n orbitals to a different extent. The IE (ionization energy) values for (e) and 7T3 (ai) orbitals decreased by 0.8-1.0 eV. The n and n+ molecular orbital two pair bands showed a weak shift of 0.1 eV or less. 

The nickel complex, Ni ( 5115)2, has been made by the action of the Grignard reagent on nickel (II) acetylacetonate (217) or from potassium cyclopentadienyl and the ammine [Ni(NHs)el (S N)2 in liquid ammonia (58). It forms dark emerald-green crystals which sublime at 80-90° and which, when heated in nitrogen, melt, with decomposition and the formation of a nickel mirror, at 173-174°. It is only slowly oxidized in air, and cold water neither attacks nor dissolves it it is, however, readily soluble in organic liquids. Oxidation of the compound yields an orange-yellow solution containing the ion [Ni( 5H5)2]+, which is stable for a short period in weakly acidic media, and which may be precipitated as the reineckate or tetraphenylborate. 

Diketones. Beta-diketones such as acetylacetone, benzoyl-acetone, and isopropyltropolone are well known for their applications in analytical extraction of actinides. These compounds are weak acids due to tautomerization thus they can act as cation exchange extractants. Trivalent actinide [M(III)] extraction by the reagent (HA) at low aqueous acid concentration where the compound behaves both as cation exchanger and coordinator probably follows the reaction... 

From weakly acid solutions, Fe(III) is extractable with acetylacetone [5], hexafluoroacetylacetone [6], and HTTA [7]. Iron(III) can be extracted with oxine in chloroform [8,9], HDEHP [10], dithiocarbamates [11,12], and Adogene 464 (in toluene) [13,14]. 

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