Beryllium species

Some structural and spectroscopic infonnation for selected beryllium amides and other beryllium species complexed by nitrogen containing ligands is provided in Table 3.1. 

The stability constant and enthalpy of reaction derived for each beryllium species can be used together with the Gibbs energy and enthalpy of formation given for Be in the literature (Bard, Parsons and Jordan, 1985 Renders and Anderson, 1987) and that for H2O listed in Chapter 5 to derive the Gibbs energy and enthalpy of formation values for each species. These can then be coupled with literature entropy data (Grenthe etal., 1992) to derive the respective entropy values. These thermodynamic data are Usted in Table 7.1. 

There is very little data on the formation of BegfOH), and other species may have been postulated in mistake for this species. The species was first identified by Bruno (1987), but, more importantly, he demonstrated that all beryllium species that form must contain reasonable chemical structures. As already indicated, the proposed structure of Be5(OH)g is similar to that of Be3(OH)3 except that it contains a second ring. Consequently, the most likely complete formula for the species is Be50(0H)4(H20)g. The potentiometric method cannot distinguish between the two structures Be5(OH)g and BegOfOH) since both species are produced with the same number of deprotonation steps (six). The formation of this species, although it is likely only a relatively minor species, appears to be sound (Alderighi et al., 2000). 

There are four stability constants available for the Beg(OH)3 species in perchlorate media at ionic strengths ranging from 0.5 to 3.0 mol dm . The agreement between the data is somewhat poorer than for the other polymeric beryllium species. All data measured in perchlorate media have been retained in this... 

Table 7.5 Literature thermodynamic data for beryllium species at 25 C.

Beryllium is found in some 30 mineral species, the most important of which are bertrandite, beryl, chrysoberyl, and phenacite. Aquamarine and emerald are precious forms of beryl. Beryl and bertrandite are the most important commercial sources of the element and its compounds. Most of the metal is now prepared by reducing beryllium fluoride with magnesium metal. Beryllium metal did not become readily available to industry until 1957. 

Some of the early reentry vehicles utilized metallic heat sinks of copper [7440-50-8] or beryllium [7440-41-7] to absorb reentry heat. Other metallic materials that have been evaluated for nosetip appHcations include tungsten [7440-33-7] and molybdenum [7439-98-7]. The melt layers of these materials are beHeved to be very thin because of the high rate at which volatile oxide species are formed. 

The hydrides of the later main-group elements present few problems of classification and are best discussed during the detailed treatment of the individual elements. Many of these hydrides are covalent, molecular species, though association via H bonding sometimes occurs, as already noted (p. 53). Catenation flourishes in Group 14 and the complexities of the boron hydrides merit special attention (p. 151). The hydrides of aluminium, gallium, zinc (and beryllium) tend to be more extensively associated via M-H-M bonds, but their characterization and detailed structural elucidation has proved extremely difficult. 

There are a few species in which the central atom violates the octet rule in the sense that it is surrounded by two or three electron pairs rather than four. Examples include the fluorides of beryllium and boron, BeF2 and BF3. Although one could write multiple bonded structures for these molecules in accordance with the octet rule (liable 7.2), experimental evidence suggests the structures... 

Combeau, C. Carlier, M.-F. (1989). Characterization of the aluminium and beryllium fluoride species bound to F-actin and microtubules at the site of the y-phosphate of the nucleotide. J. Biol. Chem. 264,19017-19022. 

Beryllium(II) is the smallest metal ion, r = 27 pm (2), and as a consequence forms predominantly tetrahedral complexes. Solution NMR (nuclear magnetic resonance) (59-61) and x-ray diffraction studies (62) show [Be(H20)4]2+ to be the solvated species in water. In the solid state, x-ray diffraction studies show [Be(H20)4]2+ to be tetrahedral (63), as do neutron diffraction (64), infrared, and Raman scattering spectroscopic studies (65). Beryllium(II) is the only tetrahedral metal ion for which a significant quantity of both solvent-exchange and ligand-substitution data are available, and accordingly it occupies a... 

Metals are divided into light (also called alkali-earth metals) and heavy. All toxic metals are heavy metals except for beryllium and barium. Additionally, other categories of elements that are or may be significant chemically as dissolved species in deep-well-injection zones include the following ... 

The zinc complex formed with V,V -diphenylformamidinate is structurally analogous to the basic zinc acetate structure, as [Zn4(/i4-0)L6], and the basic beryllium acetate structure. It is prepared by hydrolysis of zinc bis(diphenylformamidinate).184 Mixed metal zinc lithium species were assembled from dimethyl zinc, t-butyl lithium, V.iV -diphenylbenzamidine and molecular oxygen. The amidinate compounds formed are dependent on the solvent and conditions. Zn2Li2 and... 

Mineral gemstones that have the same basic chemical composition, that is, are composed of the same major elements and differ only in color, are considered as variations of the same mineral species. As gemstones, however, minerals that have the same composition and crystalline structure but exhibit different colors are classified as different gemstones. Beryl, for example, a mineral (composed of beryllium aluminum silicate), includes a pink variety, known by the gemstone name of morganite, and also a well-known green variety, emerald. Table 18 lists and classifies, by composition and color, gemstones that have been appreciated since antiquity. 

Although dimethylberyllium is a coordination polymer in the solid state,27 it has long been known to be monomeric in the gas phase.28 It has also been found to be monomeric when synthesized from the co-condensation of laser-ablated beryllium atoms and a methane/argon mixture at 10 K.11 Formed in conjunction with several other species, including hydrides (see Section 2.02.2.4), (CH3)2Be was identified from its infrared absorption bands, which were compared to DFT-calculated frequencies (DFT = density functional theory). 

In solvents that have donor properties, solubility leads to complex formation to give species such as S A1C13 (where S is a solvent molecule). Beryllium chloride is soluble in solvents such as alcohols, ether, and pyridine, but slightly soluble in benzene. 

Subsequent studies showed that other species are formed to a small extent just before precipitation begins these species have a hydroxide to beryllium ratio greater than 1, but because their concentrations are always relatively low their identification has been dogged by controversy. Mesmer and Baes obtained data at a range of temperatures and from this data proposed the minor species Be5(OH)7+ (66). Later they also suggested that the species Be6(OH)3+ was formed (10), in agreement with earlier work by Lanza and Carpeni (69, 72). These last had also proposed the additional species Be3(OH)4+ and Be6(OH)ir. 

Fig. 3. Calculated distribution of beryllium hydroxo species in acid conditions, (a) CBe = 0.2 M, (b) CBs = 0.002 M.

Between pH values of ca. 6 and 12 aqueous solutions hold very little dissolved beryllium because of the low solubility of Be(OH)2. When the pH is raised above 12, the hydroxide begins to dissolve with the formation of, first, Be(OH)3 and then, at even higher pH values, Be(OH) (52). The presence of these species in strongly alkaline solutions was confirmed by means of solvent extraction experiments (90) and infrared spectroscopy (31). A speciation diagram is shown in Fig. 7, which was constructed using the values of log /33 = 18.8 and log /34 = 18.6 critically selected from Table III. The diagram illustrates clearly the precipitation and dissolution of Be(OH)2. 

Investigations of the equilibria obtaining in solution have provided information concerning the stoichiometry and stability of the species formed when the beryllium ion is hydrolyzed. Although the identification of the minor species can never be regarded as definitive, there is little doubt that the principal species are Be2(OH)3+ and Be3(OH)3+ in acid solutions and Be(OH)3 and Be(OH)r in strongly basic solutions. Further support for these conclusions is provided by some crystal structures. The structure of [Be3(0H)3(H20)6]... 

Carell and Olin (58) were the first to derive thermodynamic functions relating to beryllium hydrolysis. They determined the enthalpy and entropy of formation of the species Be2(OH)3+ and Be3(OH)3+. Subsequently, Mesmer and Baes determined the enthalpies for these two species from the temperature variation of the respective equilibrium constants. They also determined a value for the species Be5(OH) + (66). Ishiguro and Ohtaki measured the enthalpies of formation of Be2(OH)3+ and Be3(OH)3+ calorimetrically in solution in water and water/dioxan mixtures (99). The agreement between the values is satisfactory considering the fact that they were obtained with different chemical models and ionic media. 

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