Beryllium complexes acetylacetone

Beryllium complexes acetylacetone solvolysis, 378 amides, 164 1,3-diketones... 

Beryllium complexes, 3, 3 acetylacetone solvolysis, 2, 378 amides, 2, 164 amines, 3, 7 anionic, 3, 10 1,3-diketones... 

Discussion. Beryllium forms an acetylacetone complex, which is soluble in chloroform, and yields an absorption maximum at 295 nm. The excess of acetylacetone in the chloroform solution may be removed by rapid washing with O.lM-sodium hydroxide solution. It is advisable to treat the solution containing up to 10 g of Be with up to 10 mL of 2 per cent EDTA solution the latter will mask up to 1 mg of Fe, Al, Cr, Zn, Cu, Pb, Ag, Ce, and U. 

Other methods reported for the determination of beryllium include UV-visible spectrophotometry [80,81,83], gas chromatography (GC) [82], flame atomic absorption spectrometry (AAS) [84-88] and graphite furnace (GF) AAS [89-96]. The ligand acetylacetone (acac) reacts with beryllium to form a beryllium-acac complex, and has been extensively used as an extracting reagent of beryllium. Indeed, the solvent extraction of beryllium as the acety-lacetonate complex in the presence of EDTA has been used as a pretreatment method prior to atomic absorption spectrometry [85-87]. Less than 1 p,g of beryllium can be separated from milligram levels of iron, aluminium, chromium, zinc, copper, manganese, silver, selenium, and uranium by this method. See also Sect. 5.74.9. 

Beryllium Beryllium pre-concentrated as acetylacetone complex onto activated charcoal Charcoal introduced directly into graphite furnace AAS 0.6 ng/1 0.0006 xg/l [79]... 

A broad range of metal centers have been used for the complexation of functional ligands, including beryllium [37], zinc, transition metals such as iridium [38], and the lanthanide metals introduced by Kido [39], especially europium and terbium. Common ligands are phenanthroline (phen), bathophenanthrolin (bath), 2-phenylpyridine (ppy), acetylacetonate (acac), dibenzoylmethanate (dbm), and 11 thenoyltrifluoroacetonate (TTFA). A frequently used complex is the volatile Eu(TTFA)3(phen), 66 [40]. 

The structure of bis(salicylaldoxime)beryllium has been proposed as being trans octahedral by comparison of the space group and unit cell volume with those of related transition metal complexes it is presumably a dihydrate if it is indeed octahedral in geometry.297 Stability constants have been reported for a range of beryllium /3-ketoamines derived from both salicylaldehyde and acetylacetone precursors. They show strong complexes which are stable to hydrolysis under the conditions used.298,299... 

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... 

Beryllium chemistry includes its S-diketonate complexes formed from dimedone (9), acetylacetone and some other S-diketones such as a,a,a-trifluoroacetylacetone. However, unlike the monomeric chelate products from acetylacetone and its fluorinated derivative, the enolate species of dimedone (9) cannot form chelates and as the complex is polymeric, it cannot be distilled and is more labile to hydrolysis, as might be expected for an unstabilized alkoxide. However, dimedone has a gas phase deprotonation enthalpy of 1418 9 kJmoD while acetylacetone enol (the more stable tautomer) is somewhat less acidic with a deprotonation enthalpy of 1438 10 klmoD Accordingly, had beryllium acetylacetonate not been a chelate, this species would have been more, not less, susceptible to hydrolysis. There is a formal similarity (roughly 7r-isoelectronic structures) between cyclic S-diketonates and complexes of dimedone with benzene and poly acetylene (10). The difference between the enthalpies of formation of these hydrocarbons is ca... 

TTA is a fluorinated /S-diketone that is more acidic than acetylacetone and therefore permits extractions at lower pH values, in spite of its complexes being less stable than those of acetylacetone. For example, iron can be extracted from 10 M nitric add. Bolomey and Wish, in developing a method for isolating carrier-free radioberyllium, studied the extraction of various metals using a dilute (0.01 M) solution of TTA in benzene. In certain cases, especially for beryllium and Fe(III) at low pH values, equihbrium was attained slowly. The extraction rate can be increased by increasing the reagent concentration or by raising the pH. Thus in some instances equilibration time can be manipulated to improve separability. The difference in the extraction behavior of the lanthanides and the actinides is noteworthy. ... 

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. 

After extraction from the matrix elements by chloroform of its acetylacetonate, beryllium was separated from co-extracted aluminum by means of a column of the stron y acidic cation-exchanger Dowex 50 Adsorption is affected by tetrahydro-furan-chlorform-methanol-hydrochloric acid medium, elution of aluminum with oxalic acid, and beryllium with 6 M hydrochloric acid. Bismuth was selectively adsorbed in the form of a thiourea complex on a column of a polymer with tri-butylphosphate in the presence of the remaining Fe, Sb, Cu V... 

One of the most versatile classes of ligands in coordination chemistry is that of the /3-diketonates, of which the most common is the acetylacetonate, (acac), Figure 9.1. The coordination chemistry of this ligand first appears in the literature in work by Combes in 1887-1894. Alfred Werner also published on the chemistry of the acac ligand in 1901. The acac ligand is remarkable in that it forms complexes with virtually any metal, including beryllium, lead, aluminum, chromium, platinum, and gadolinium. 

The major breakthrough that transformed metal chelate GC into a useful analytical technique was the introduction of fluorinated beta-diketone ligands, which formed complexes of greater volatility and thermal stability. Trifluoroacetylacetone (l,l,l-trifluoro-2,4-pentanedione—HTFA) and hexafluoro-acetylacetone (l,l,l,5,5,5-hexafluoro-2,4,-pentanedione—HHFA) are the fluorinated ligands most frequently employed. HTFA extended the range of metals that may be gas chromatographed with little or no evidence of decomposition to include Ga3+, In3+, Sc3+, Rh3+ and V4+. An example of a recent application is the analysis for beryllium in ambient air particulates. After filter sampling and extraction/chelation, packed column GC with electron capture detection allowed ppm level beryllium quantitation in collected particulates which corresponded to levels of 2-20 x 10 5 pg/m3 in the sampled air. 

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. 

Acetylacetone test acetylacetone reacts with beryllium salts to yield the complex Be(C5H702)2, which possesses a highly characteristic appearance under the microscope. 

Speciation of chromium (histidine/acetic acid acetate buffer/EDTA °), mercury (borate/MeOH), tin (pyridine/CTAB), lead (SDS/p-CD), arsenic (borate, phosphate or phosphate/borate, " phosphate/TTAB, phosphate andphosphate/TTAB ), sulfur (phosphate/TTAB/ACN), and selenium (histidine/acetic acid, SDS/p-CD ) by CE methods have been reported. Other examples include the analysis of beryllium (as an acetylacetone complex) in digested airborne dust and the determination of Fe(II)-, Cu(I)-, Ni(ll)-, Pd(II)-, and Pt(II)-cyano complexes and nitrate from leaching solutions of automobile catalytic converters. ... 

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