P-Diketones anions

The (3-diketonate chelate complexes are very stable and exhibit properties which are rather typical of aromatic systems. Many of their reactions such as halogenation, alkylation and acylation can be compared with those of the P-diketonate anions associated with alkali metal cations. However, complexes of transition and other metals add to the stability of the system, so that quite vigorous reaction conditions can be employed. In most of the work carried out on P-diketonate chelates, the modified ligand has not been removed from the metal ion, but this can usually be effected if desired. 

Indanedione dehydro dimers (45) undergo facile carbon-carbon bond cleavage (equation 29), either electrochemically, or by a variety of chemical reductants such as Pt/H2, Na/NHa or TxtlHCV Presumably the process is markedly assisted here by the production of two p-diketonate anions. By the same... 

Pandey S, Baker GA, Sze L et al (2013) Ionic liquids containing iluorinated p-diketonate anions synthesis, characterizati(Hi and potential applications. New J Chem 37 909-919... 

As mentioned earlier, nitrone 1 can be regarded as isoelectronic with an anion of p-diketone, and hence Eu(fod)3, an NMR shift reagent, bearing p-diketone anions as ligands was expected to activate (Z)-l in an equilibrium mixture of (Z)-l and E)- by forming (Z)-l-Eu(fod)3 complex, which would undergo stereoselective cycloaddition (Scheme 6.2) [7-9]. 

Even though ketones have the potential to react with themselves by aldol addition recall that the position of equilibrium for such reactions lies to the side of the starting materials (Section 18 9) On the other hand acylation of ketone enolates gives products (p keto esters or p diketones) that are converted to stabilized anions under the reaction conditions Consequently ketone acylation is observed to the exclusion of aldol addition when ketones are treated with base m the presence of esters... 

Stabilized anions exhibit a pronounced tendency to undergo conjugate addition to a p unsaturated carbonyl compounds This reaction called the Michael reaction has been described for anions derived from p diketones m Section 18 13 The enolates of ethyl acetoacetate and diethyl malonate also undergo Michael addition to the p carbon atom of a p unsaturated aldehydes ketones and esters For example... 

OL Alkylation of aldehydes and ketones (Section 18.15) Alkylation of simple aldehydes and ketones via their enolates is difficult. p-Diketones can be converted quantitatively to their enolate anions, which react efficiently with primary alkyl halides. 

In closing, recovery of technetium from waste solution should be touched upon. Studies of the base hydrolysis of technetium P-diketone complexes revealed that all of the complexes studied decompose in an alkaline solution even at room temperature, until technetium is finally oxidized to pertechnetate. These phenomena are very important for the management of technetium in waste solutions. Since most metal ions precipitate in alkaline solution, only technetium and some amphoteric metal ions can be present in the filtrate [29]. A further favorable property of pertechnetate is its high distribution coefficient to anion exchangers. Consequently, it is possible to concentrate and separate technetium with anion exchangers from a large volume of waste solution this is especially effective using an alkaline solution [54],... 

Now let us look at the ease of forming the enolate anion nucleophiles. Ketones are more acidic than esters (see Section 10.7). Taken together, these factors mean the more favoured product is going to be the P-diketone (acetylacetone), formed from a ketone nucleophile by a Claisen reaction with an ester. This is the reaction observed. 

Reaction between the nitroso group and the anion of a P-diketone is often sufficiently rapid to compete with further reduction of the nitroso compound to the hy-droxylamine. This process is illustrated by reduction of 8. The initial ring closure product undergoes further reduction at the catltode and 9 is isolated in good yield... 

Pettinari et al. [49] reported a Zundel ion H5OJ stabilized tetrakis(P-diketonate) europium complex, H5O J [Eu(L" )4]. The complex anion in this ion-pair complex is charge balanced by the Zundel cations H5OJ, which is stabilized by strong H bonding with the N atoms of the anionic heterocyclic ligand The crystal structure study revealed that different [Eu(L )4] ... 

Figure 2.30 Representation of the asymmetric unit of [Nd(L )4(H20)][(TTF—CH=CH—Py+)] 2-The radical cation donors are drawn as balls and sticks the paramagnetic anionic coordination complexes of Nd(III) are drawn as capped sticks [23d], (Reprinted with permission from F. Pointillart, O. Maury, Y. Fe Gal, S. Golhen, O. Cador and F. Ouahab, 4-(2-Tetrathiafulvalenyl-ethenyl)pyridine (TTF—CH=CH—py) radical cation salts containing poly(P-diketonate) rare earth complexes synthesis, crystal structure, photoluminescent and magnetic properties, Inorganic Chemistry, 48, 7421-7429, 2009. 2009 American Chemical Society.)...

Bis- -diketones have been demonstrated to be powerful ligands in the engineering of supramolecular architectures. Pikramenou and coworkers [53a] used two bis-P-diketones of l,3-bis(3-phenyl-3-oxopropanoyl)benzene (H2L ) and l,3-bis(3-phenyl-3-oxopropanoyl) 5-ethoxy-benzene (H2L ) to synthesize neutral homodimetallic complexes [Ln2(L )3] (Ln = Eu, Nd, Sm, Y, Gd) and [Ln2(L )3] (Ln = Eu, Nd) and also an anionic dinuclear lanthanide complex [Eu2(L )4] . The detailed studies by NMR, electrospray, and MALDI (matrix assisted laser desorption ionization) mass spectrometry, by addition of chiral Pirkle s reagent, revealed that [Ln2(L" )3] and [Eu2(L )4] (see Eigure 2.38) are chiral, and have triple- and quadruple-stranded supramolecular structures, respectively, with the latter being more strongly emissive than the former. 

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