Diketones metals

Bond character of (3-diketone metal chelates. B. Bock, K. Flatau, H. Junge, M. Kuhr and H. Muses, Angew. Chem., Int. Ed. Engl., 1971,10, 225-235 (114). 

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... 

Rearrangements of six-coordinate tris(diketonate) metal complexes have been the subject of numerous intense and careful investigations and the great body of literature has been incisively reviewed.77,283 A principal conclusion is that in no case has a unique rearrangement been unambiguously established and indeed, one may not exist. The difficulty arises from the consideration that the various five-coordinate transition states (or intermediates) which result from bond rupture processes can have quite similar energies. Thus, combinations of mechanisms can obtain which lead to extremely complicated DNMR spectra or isomerization kinetics. 

The intramolecular electron exchanges among the different metal sites of polynuclear /3-diketonate-metal complexes are a matter of intrinsic interest, especially as far as the stabilization of mixed-valent oxidation states is concerned " . Obviously, the pertinent electrochemical pattern, while becoming richer and richer, also tends to become more... 

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 elements which are co-precipitated as hydroxides can also be separated by organic reagents of the R-OH type, such as 8-hydroxyquinoline, cupferron, or 6-diketones. Metal ions giving sparingly soluble sulphides may be co-precipitated by organic reagents of the R-SH type, e.g., dithiocarbamates. 

The benzoylation of a series of 8-diketone metal chelates has been investigated for the purpose of assessing the steric and electronic factors involved in the production of O-acyl and C-acyl compounds (153). The benzoylation of the metal chelates of diisobutyrylmethane, di-n-butyryl-methane, and benzoylisobutyrylmethane was investigated by the following method. Benzoyl chloride (1 mole in the case of the sodium chelate and... 

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