石墨炉原子吸收分光光度法测定空气中的铍

对300余个样品进行监测,选择灵敏度高的石墨管和最佳基体,提高灰化、原子化的温度,确立了石墨炉原子吸收法测定空气中铍含量的实验条件。样品采用干灰化消解法,最佳溶剂为质量分数l％的硝酸溶液,利用仪器内置的样品浓度计算程序,绘制工作曲线直接获得样品中铍的含量。方法检出限为0．021μg／L,测定结果的相对标准偏差小于2％（n=6）,线性范围为0～6．5μg／L,加标回收率为91．6％～107％。     

X-射线荧光光谱测定氧化铍中杂质元素

拟定了ＢｅＯ中１２种痕量杂质元素的Ｘ－射线荧光光谱测定方法,采用光谱纯试剂人工合成校准标样,粉末压块法制备分析样片。考虑到ＢｅＯ对Ｘ射线的透明性,在样片与样品盒支架之间垫置钼片消除试样盒发射线的干扰并产生附加激发以提高灵敏度。本文分析结果与等离子民发射和原子吸收光谱对照相吻合。     

Ternary Complexes Stabilized by Chalcogen and Alkaline-Earth Bonds: Crucial Role of Cooperativity and Secondary Noncovalent Interactions

High-level G4 calculations show that the strength of chalcogen interactions is enhanced dramatically if chalcogen compounds simultaneously form alkaline-earth bonds. This phenomenon is studied by exploring binary YX₂⋅⋅⋅N-Base complexes and two types of ternary MCl₂⋅⋅⋅YX₂⋅⋅⋅N-Base, YX₂⋅⋅⋅N-Base⋅⋅⋅MCl₂ complexes, in which YX₂ is a chalcogen compound (Y=S, Se; X=F, Cl), the N-Bases are sp, sp², and sp³ bases (NCH, HN=CH₂, NH₃), and MCl₂ are alkaline-earth BeCl₂ or MgCl₂ derivatives. Starting from the chalcogen-bonded complexes YX₂⋅⋅⋅NH₃ and YX₂⋅⋅⋅HN=CH₂, the binding site of a new incoming alkaline-earth bond is found, surprisingly, to depend on the nature of the halogen atom attached to the chalcogen. For the YF₂ binary complexes the association site is the F atom of the YF₂ subunit, whereas for YCl₂ it is the N atom of the nitrogen base. Regarding YX₂⋅⋅⋅NCH complexes, N is the most favorable site for an alkaline-earth interaction in ternary complexes, regardless of which YX₂ derivative is used. The explanation relies on the interplay of all the noncovalent interactions involved: the strong cooperativity between chalcogen and alkaline-earth bonds, and the appearance of secondary noncovalent interactions in the form of hydrogen bonds.     

Computational Study of spx(x=1–3)-Hybridized Be−Be Bonds Stabilized by Amidinate Ligands

Complexes containing odd-electron Be−Be bonds are still rare until now. Hereby, a series of neutral di-beryllium amidinate complexes containing a Be−Be bond were explored theoretically. The complexes with direct chelation with the Be₂ dimer by the bidentate amidinate (AMD) ligands are always corresponding to their global minimum structures. The detailed bonding analyses reveal that the localized electrons of the Be−Be fragment can be adjusted by the amount of AMD ligands because each AMD ligand only takes one electron from the Be₂ fragment. Meanwhile, the hybridization of the central Be atom also changes as the number of AMD ligands increases. In particular, the sp³-hybridized single-electron Be−Be bond is firstly identified in the tri-AMD-ligands-chelated neutral D_3h- Be₂(AMD)₃ complex, which also possesses the higher stability compared to its monoanionic D_3h- Be₂(AMD)₃ ⁻ and monocationic C₃- Be₂(AMD)₃ ⁺ analogues. Importantly, our study provides a new approach to obtain a neutral odd-electron Be−Be bond, namely by the use of radical ligands through side-on chelation.     

IR Spectra of Be(IO3)2.nH2O (n = 4, O) and of the Deuterated Analogue

Abstract

The compounds of beryllium - Be(IO₃)₂.4H₂O, its deuterated analogue and Be(IO₃)₂ were studied by IR-spectroscopy over the range of 200 to 4000 cm^?1.     

Be3Ru: Polar Multiatomic Bonding in the Closest Packing of Atoms

The new phase Be₃Ru crystallizes with TiCu₃-type structure (space group Pmmn (59), a=3.7062(1) Å, b=4.5353(1) Å, c=4.4170(1) Å), a coloring variant of the hexagonal closest packing (hcp) of spheres. The electronic structure revealed that Be₃Ru has a pseudo-gap close to the Fermi level. A strong charge transfer from Be to Ru was observed from the analysis of electron density within the Quantum Theory of Atoms in Molecules (QTAIM) framework and polar three- and four-atomic Be−Ru bonds were observed from the ELI−D (electron localizability indicator) analysis. This situation is very similar to the recently investigated Be₅Pt and Be₂₁Pt₅ compounds. The unusual crystal chemical feature of Be₃Ru is that different charged species belong to the same closest packing, contrary to typical inorganic compounds, where the cationic components are located in the voids of the closest packing formed by anions. Be₃Ru is a diamagnet displaying metallic electrical resistivity.     

Complexes between H2 and neutral oxyacid beryllium derivatives. The role of angular strain

ABSTRACT

The complexes between 14 different Be-salts of oxyacids from groups 13 to 16 with one and two molecules of H₂ have been investigated by means of the MP2/aug-cc-pVTZ ab initio molecular orbital theory method, which was found to be reliable for the treatment of these weakly bound species. The main conclusion is that these Be-salts yield rather stable complexes with dihydrogen, with binding energies one order of magnitude larger than other typical H₂ complexes reported in the literature. This strong binding is shown to be due to an enhancement of the electron-deficient nature of Be when attached to an oxyacid moiety, which depends more on the type of coordination of the central atom of the oxyacid moiety. The formation of these complexes is followed by a significant lengthening of the H₂ internuclear distance and a concomitant red-shift of the H–H stretching frequency, which becomes a good indicator of the strength of the interaction. The charge shifting from the bonding region of the H₂ molecule to the interboundary Be···H₂ region is the physical phenomenon behind the stability of these complexes. Accordingly, the most important contributor to this stability is the inductive term, followed by the electrostatic interactions. The ability of Be to bind H₂ is enhanced by the angular arrangement of the O–Be–O electron-acceptor group.     

9Be and 31P NMR analyses on the influence of imino groups on Be2+ complex stabilities of a series of cyclo‐μ‐imido triphosphate anions

The complexation behaviors of Be²⁺ with cyclo‐μ‐imido triphosphate anions, cP₃O_9?n(NH)_n^3? (n = 1, 2), have been investigated by both ⁹Be and ³¹P NMR techniques at ?2.3 °C in order to clarify the coordination structures of the complexes. The spectra showed that cP₃O_9?n(NH)_n (n = 1, 2) ligands form ML, ML₂, and M₂L complexes with Be²⁺ ions, and the formation of complexes coordinating with nitrogen atoms of the cyclic framework in the ligand molecule has been excluded. These complexation trends are very similar to those of Be²⁺‐cP₃O₆(NH)₃^3? system, which has been reported by us. The peak deconvolution of ⁹Be NMR spectra made these beryllium complexes amenable to stability constant determinations. The stability constants of the complexes increase with an increase in the protonation constants of the ligands as the number of imino groups, which constitute the ligand molecules, is ascended. This increase is primarily attributable to the lower electronegativity of nitrogen atoms than oxygen atoms, which are directly bonded to central phosphorus atoms; moreover, tautomerism equilibrium in the entire of the imidopolyphosphate molecule is also responsible to the higher basicity. ³¹P NMR spectra measured concurrently have verified the formation of the complexes estimated by the ⁹Be NMR measurement. Intrinsic ³¹P NMR chemical shift values of the phosphorus atoms belonging to ligand molecules complexed with Be²⁺ cations have been determined. Not only the protonation constants but also the stability constants of all Be²⁺ complexes increase approximately linearly with an increase in the number of imino groups. Copyright © 2013 John Wiley & Sons, Ltd.     

Reactivity of Diphenylberyllium as a Brønsted Base and Its Synthetic Application

Diphenylberyllium [Be₃Ph₆] is shown here to react cleanly as a Brønsted base with a vast variety of protic compounds. Through the addition of the simple molecules tBuOH, HNPh₂ and HPPh₂, as well as the more complex 1,3-bis-(2,6-diisopropylphenyl)imidazolinium chloride, one or two phenyl groups in diphenylberyllium were protonated. As a result, the long-postulated structures of [Be₃(OtBu)₆] and [Be(μ-NPh₂)Ph]₂ have finally been verified and shown to be static in solution. Additionally [Be(μ-PPh₂)(HPPh₂)Ph]₂ was generated, which is only the second beryllium-phospanide to be prepared; the stark differences between its behaviour and that of the analogous amide were also examined. The first crystalline example of a beryllium Grignard reagent with a non-bulky aryl group has also been prepared; it is stabilised with an N-heterocyclic carbene.