Beryllium compounds, acetylacetonate

Four-coordinate monomeric complexes are formed with either tetrahedral or planar stereochemistries. With acetylacetone, the beryllium compound (2) has been studied crystallographically and has the expected tetrahedral configuration. Crystalline Cu(AA)2 shows a nearly planar (13) arrangement however, some intermolecular perturbation does occur. 

By functioning as Lewis acids, many beryllium compounds attain maximum coordination of the metal atom. Thus the chloride forms etherates, Cl2Be(OR2)2, and complex ions such as BeF and [Be(H20)4]2+ exist. In chelate compounds such as the acetylacetonate, Be(acac)2, four approximately tetrahedral bonds are formed with the C—O and Be—O bond lengths equivalent. 

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... 

The interaction of beryllium acetylacetonate with bis(acetoacetyl) compounds leads to coordination polymers. With bis(acetoacetyl)phenyl ether in dimethylformamide the reaction was found to be reversible [214], viz. 

Nomenclature. The nomenclature of the metallic derivatives of the 1,3-diketones in the literatme has not been definitive. These compounds have usually been called acetylacetonates or derivatives of acetylacetonates, e.g., zirconium acetylacetonate, beryllium benzoylacetonate, and lanthamun trifluoroacetylacetonate. A better nomenclature is based on the extensions of the International Union of Chemistry (I.U.C.) rules for inorganic nomenclature to include all types of coordination compounds. Thus, the foregoing names become tetrakis(2,4-pentane-diono) zirconium, bis(l-phenyl-l,3-butanediono)-beryl-lium, and tris(l,l,l-trifluoro-2,4-pentanediono)lanthanum. Further examples are... 

Photometric methods are widely employed in the determination of microamounts of beryllium. These methods are used primarily when simplicity and speed are preferred. Many colored reagents are employed, as well as reagents such as acetylacetone, salicyclic and sulfosalicyclic acids, whose compounds with beryllium display an intense absorption in the UV range. Colorimetric determination of beryllium in coal has been described by Abernethy and Hattman [1]. This spectro-photometric method is sufficiently sensitive for the determination of microgram quantities and may be desirable for small laboratories without access to spectro-graphic equipment. 

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