Acetylacetone dissociation

Chen, X.-B. Fang, W.-H. Phillips, D. L. Theoretical Studies of the Photochemical Dynamics of Acetylacetone Isomerization, Dissociation, and Dehydration Reactions. J. Phys. Chem. A 2006,110, 4434-4441. 

Acid Dissociation Constants and Formation Constants. Attempts to determine acid dissociation constants of bisacetylacetoneethylenediimine and bis-acetylacetone-m-phenylenediamine in 50 volume % dioxane-water were unsuccessful. The procedure used was successful when applied to bis (/ -diketones) (II). Likewise, attempts to determine formation constants of the tetradentate / -keto-imines were unsuccessful, apparently because of hydrolysis. 

In the above examples, the nucleophilic role of the metal complex only comes after the formation of a suitable complex as a consequence of the electron-withdrawing effect of the metal. Perhaps the most impressive series of examples of nucleophilic behaviour of complexes is demonstrated by the p-diketone metal complexes. Such complexes undergo many reactions typical of the electrophilic substitution reactions of aromatic compounds. As a result of the lability of these complexes towards acids, care is required when selecting reaction conditions. Despite this restriction, a wide variety of reactions has been shown to occur with numerous p-diketone complexes, especially of chromium(III), cobalt(III) and rhodium(III), but also in certain cases with complexes of beryllium(II), copper(II), iron(III), aluminum(III) and europium(III). Most work has been carried out by Collman and his coworkers and the results have been reviewed.4-29 A brief summary of results is relevant here and the essential reaction is shown in equation (13). It has been clearly demonstrated that reaction does not involve any dissociation, by bromination of the chromium(III) complex in the presence of radioactive acetylacetone. Furthermore, reactions of optically active... 

Only a small amount of research has been published dealing with the reactions of / -diketones with clean metal surfaces.513,514 The interaction of acetylacetone with iron and nickel films under ultra high vacuum conditions has been investigated. X-Ray photoelectron spectroscopy is a particularly useful analytical probe as data on gas phase metal acetylacetonates are available for comparison.515 On iron, dissociative adsorption giving acetylacetonate occurs at 90 K. This decomposes at about 290 K to form surface oxide, chemisorbed oxygen and a species considered to contain Fe—C bonds. 

Selenophene /3-diketones can be used as extractants for the separation and isolation of metals. The advantages of selenophene /3-dike-tones were revealed by comparison of their dissociation and distribution constants with those of acetylacetone, benzoylacetone, thenoyl-trifluoromethylacetone, etc. Selenophene /3-diketones containing a trifluoromethyl group and a pyridyl radical were of particular interest. 2-Acetoacetylselenophene127 is better for the extraction of thorium from water than acetylacetone, previously extensively used. 

Acetophenone, A/-methyloxazolidine derivative, lithiation, 56, 261 Acetyl hypofluorite fluorination of uracil by, 59, 3 fluorination using, 60, 7 reaction with pyridines, 58, 280, 289 Acetylacetone, hexafluoro-, reaction with ethylenediamine, 56, 3 Acetylene cyclic dimer, trimer. tetramer, dissociation energies, 56, 343 Acetylenes, activated reactions with 3-diazo-azoles, 59, 70... 

Chromium hexacarbonyl is extremely photolabile (equation 6) therefore photochemical substitution is an efficient means of preparing derivatives. Oxidation of the Cr center requires nitric or sulfuric acid, or chlorine. Alternatively, some hgands induce complete carbonyl dissociation with concomitant oxidation, for example, acetylacetonate. Chemical reduction with alkali or alkaline-earth metals or electrochemical reduction proceeds in two-electron steps with loss of two CO molecules to first give [Cr2(CO)io]" and then [Cr(CO)s]. Nucleophilic attack at CO generates a number of stable (Nu = R) and unstable (Nu = N3, OH, H, NEt2) products. The stable [(OC)5CrCOR] ion is a carbene precursor. 

Separation of six -diketonate-metal chelates by HPLC was first carried out by liquid-liquid partition chromatography involving water-ethanol-2,2,4-trimethylpentane. Of the examined acetylacetonates of Be(II), Al(III), Cr(III), Fe(III), Co(III), Ni(II), Cu(II), Zn(II), Zr(IV) and Ru(III), they separated four-component mixmres within 25 minutes. Because of dissociation of the chelates on the column, acacH had to be included in the eluent Successful separation of S-diketonate chelates by normal phase chromatography was demonstrated also by other investigators ... 

The Michael addition of anions of C-acids, such as acetylacetone or hydrocyanic acid, to phenyl vinyl ketone follows a scheme similar to (7). In the cases studied it was possible to neglect the acid-base properties of the adduct and the reverse elimination reaction (Hrubcova, 1964). Equations analogous to (9) and (10) were used and the pH-dependence of the determined formal rate constant at a given analytical concentration of the C-acid follows a dissociation curve with an inflexion at the pKa value of the C-acid. 

Acetylacetonates of the types M(acac)2X2 and M(acac)3X are known. The former have cis octahedral configurations but appear to dissociate, whereas the latter are 7-coordinate and, except for X = I, do not dissociate.17... 

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