Beryllium, chelates

Beryllium chelates such as bis[2-(2-hydroxyphenyl)-pyridine]beryllium (Beq2, 86) (Scheme 3.74) emit pure blue light with an emission peak centered at 465 nm [269]. ITO/NPD/Bepp2/LiF/Al exhibited a maximum luminance of 15,000 cd/m2 and amaximum luminescent efficiency of 3.43 lm/W (3.8 cd/A). The emission color may have contributions from both NPD and Bepp2 as stated by the authors. 

The beryllium chelate of 2,4-pentanedione is another example of a stable chelate it melts at 108°, boils at 270°, and is soluble in many organic solvents. By replacing the methyl groups of 2,4-pentanedione with rert-butyl groups, a diketone is obtained which, with many metals including transition and rare-earth metals, forms complexes that often are highly soluble in nonpolar organic solvents. The interior of these chelates is saltlike but the exterior is hydrocarbonlike and nonpolar, which accounts for the substantial solubility in nonpolar solvents. 

In environmental analyses, Ross and Sievers [629] analysed water and solid particles trapped on air sampling filters and for the detection of beryllium chelates used on ECD... 

Bis(A-alkylsalicylaldiminato)beryllium complexes (54) have been prepared and their physicochemical properties studied. Dipole momenr and NMR studies are interpreted in terms of a tetrahedral environment for the beryllium. NMR studies on the magnesium and calcium analogues are similarly interpreted. The free energy of enantiomerization has been determined for (54 R = isopropyl) using NMR techniques and without needing resolution of the mtical antipodes the inversion has been proposed as proceeding via a dimerization step. The fluorescent properties of a range of beryllium chelates have been monitored with a... 

The chemistry of alkali-metal tetramonocarboxylatoberyllates M2[Be(RC02)4] (M = Na, K, Rb, or Cs) has been extended to include acetate, formate, mono-chloroacetate, propionate, butyrate, and benzoate ligands. Beryllium chelates of N-substituted acetoacetamides react with N-iodosuccinimide (in CHQ3) and... 

In the presence of very large amounts of beryllium, which fluoresces under the same conditions as zirconium, the use of 3,4, 7-trihydroxyflavone as reagent instead of morin is recommended because the fluorescence of its zirconium chelate is 1,400 times stronger than the corresponding beryllium chelate.2... 

Ceramic-grade beryllium oxide has also been manufactured by a process wherein organic chelating agents (qv) were added to the filtered beryllium sulfate solution. Beryllium hydroxide is then precipitated using ammonium hydroxide, filtered, and carefully calcined to obtain a high purity beryllium oxide powder. 

In addition to the oxide carboxylates, beryllium forms numerous chelating and bridged complexes with ligands such as the oxalate ion C204 , alkoxides, /9-diketonates and 1,3-diketonates. These almost invariably feature 4-coordinate Be... 

Other fluorinated derivatives of acetylacetone are trifluoroacetylacetone (CF3COCH2COCH3) and hexafluoroacetylacetone (CF3COCH2COCF3), which form stable volatile chelates with aluminium, beryllium, chromium(III) and a number of other metal ions. These reagents have consequently been used for the solvent extraction of such metal ions, with subsequent separation and analysis by gas chromatography [see Section 9.2(2)]. 

The number of reported applications to analytical determinations at the trace level appear to be few, probably the best known being the determination of beryllium in various samples. The method generally involves the formation of the volatile beryllium trifluoroacetylacetonate chelate, its solvent extraction into benzene with subsequent separation and analysis by gas chromatography..61... 

A poly(acrylaminophosphamic-dithiocarbamate) chelating fibre hasbeen used to preconcentratrate several trace metals in seawater by a factor of 200 [957]. The elements included beryllium, bimuth, cobalt, gallium, silver, lead, cadmium, copper, manganese, and indium. ICP-MS was used for detection. 

Published equilibrium constants for monocarboxylato complexes are summarized in Table VII. All that can be deduced with certainty from these data is that the anions derived from monocarboxylic acids form rather weak complexes with beryllium. In all probability they act as monodentate ligands. The possibility of bidentate chelation using both carboxylate oxygen atoms can be ruled out on the grounds... 

The interaction of ligands derived from salicylic acid and its derivatives has been extensively investigated (83, 147, 149, 160, 170, 176, 183-205). A similar situation obtains with regard to l-hydroxy-2-naphthoic acid (185, 194, 196, 198, 206-215). Salicylic acid derivatives may be useful in chelation therapy for beryllium poisoning (2). 

Other metal chelate materials of ligands such as benzimidazole have been disclosed in a Kodak patent as their beryllium or aluminum complexes (244) [271]. These materials generate very pure blue color within CIE range of (0.15-0.16, 0.12-0.17) [154,272]. 

Where the valency of a metal is not indicated, the normal valency of the metal is assumed. Beryllium probably is placed in the 0=N group because of the stability of its phthalocyanine chelate. Most often Be forms very stable bonds with oxygen as the donor element. Vanadium, nickel, and copper from the N > O group and iron from the ON group are the elements most frequently found in petroleum, chelated with porphyrin ligands. The porphyrin chelate contains four nitrogens as donor elements. 

A second form of optical isomerism analogous to that shown by organic spirocyclic compounds has been demonstrated. Any molecule will be optically active if it is not superimposable on its mirror image. The two enantiomers of bisfben-zoylacetonato)beryllium are illustrated in Fig. 12.3. In order for the complex to be chiral, the chelating ligand must be unsymmetric (no/ necessarily asymmetric or chiral, itself) [Be cac ] is not chiral. 

That a number of metal chelate complexes are intensely fluorescent did not escape attention and the use of morin by E. B. Sandell (1940) for the quantitative determination of traces of beryllium in the presence of aluminum is a noteworthy landmark.5... 

Ammonium beryllium carbonate solutions are prepared by dissolving the hydroxide or the basic carbonate in warm (50°C) aqueous mixtures of NH4HCO3 and (NH4) C03. After filtering to remove insoluble impurity hydroxides and adding a chelating agent, heating above 88°C evolves... 

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