氢化物发生—光度分析法

氢化物发生－光度分析法是同一反应系统中，使氢化物的发生、传输，吸收显色同时进行并同步完成的一种新分析方法，具有高灵敏，高选择性，且简单实用的特点，适用于Ｇｅ，Ａｓ，Ｓｎ，Ｓｂ，Ｓｅ，Ｂｉ，Ｐｂ，Ｔｅ等共价氢化物元素的分析，本文对这一方法的原理及其在吸收显色体系、多元素的同时或连续测定，价态形态分析，干扰的消除方法及分析应用等方面的发展进行了评述。     

Molecular Structures of Dimeric and Trimeric Dineopentylaluminum Hydride and Trimeric Diphenylaluminum Hydride

The synthesis of dineopentylaluminum hydride, H‐Al(CH₂CMe₃)₂, is known in the literature since 1988. We determined the crystal structure of this important starting material and found different ring sizes with dimeric versus trimeric formula units. The molecular shape depends on the polarity of the solvent used for recrystallization (n‐pentane or 1,2‐difluorobenzene). The synthesis of diphenylaluminum hydride, which is also long known in the literature, was optimized. It has a trimeric structure in the solid state with an Al₃H₃ heterocycle.     

三氢化铝乙醚配合物的稳定性及其固相转晶制备α-三氢化铝

针对不同贮存时长三氢化铝醚合物能否转晶制备α-三氢化铝问题进行了深入研究。 本文采用传统法制得三氢化铝醚合物并在氮气气氛下储存1~20 d,然后基于此三氢化铝醚合物,采用固相、真空转晶技术制备α-三氢化铝。 X射线衍射(XRD)、热重分析(TGA)和扫描电子显微镜(SEM)分析表明,随着醚合物贮存时间的延长,其乙醚成分逐渐降低,贮存10 d仍然可以制备出纯度较高的α-三氢化铝,然而10 d后,有γ-三氢化铝产生,而且产物粒径变小。 证明醚合物中乙醚的含量多少与制备出的α-三氢化铝的品质有直接关联。 制备过程摒弃有毒试剂甲苯,也为α-三氢化铝的千克级制备提供了一种可能。     

Synthesis of High-Purity Calcium Hydride

A procedure for synthesizing high-purity calcium hydride in high yield was suggested. The admixture composition of the resulting CaH₂ was determined by laser mass spectrometry.     

Hydrogen-Release Reaction of a Complex Transition Metal Hydride with Covalently Bound Hydrogen and Hydride Ions

The hydrogen-release reaction of a complex transition metal hydride, LaMg₂NiH₇, composed of La³⁺, 2×Mg²⁺, [NiH₄]⁴⁻ and 3×H⁻, was studied by thermal analyses, powder X-ray, and neutron diffraction and inelastic neutron scattering. Upon heating, LaMg₂NiH₇ released hydrogen at approximately 567 K and decomposed into LaH₂₋₃ and Mg₂Ni. Before the reaction, covalently bound hydrogen (H^c°^v.) in [NiH₄]⁴⁻ exhibited a larger atomic displacement than H⁻, although a weakening of the chemical bonds around [NiH₄]⁴⁻ and H⁻ was observed. These results indicate the precursor phenomenon of a hydrogen-release reaction, wherein there is a large atomic displacement of H^c°^v. that induces the hydrogen-release reaction rather than H⁻. As an isothermal reaction, LaMg₂NiH₇ formed LaMg₂NiH_2.4 at 503 K in vacuum for 48 h, and LaMg₂NiH_2.4 reacted with hydrogen to reform LaMg₂NiH₇ at 473 K under 1 MPa of H₂ gas pressure for 10 h. These results revealed that LaMg₂NiH₇ exhibited partially reversible hydrogen-release and uptake reactions.     

Hydride encapsulation by molecular alkali-metal clusters

The sequential treatment of group 12 and 13 Lewis acids with alkali-metal organometallics is well established to yield so-called 'ate' complexes, whereby the Lewis-acid metal undergoes nucleophilic attack to give an anion, at least one group 1 metal acting to counter this charge. However, an alternative, less well recognised, reaction pathway involves the Lewis acid abstracting hydride from the organolithium reagent via a beta-elimination mechanism. It has recently been shown that in the presence of N,N'-bidentate ligands this chemistry can be harnessed to yield a new type of molecular main-group metal cluster in which the abstracted LiH is effectively trapped, with the hydride ion occupying an interstitial site in the cluster core. Discussion focuses on the development of this field, detailing advances in our understanding of the roles of Lewis acid, organolithium, and amine substrates in the syntheses of these compounds. Structure-types are discussed, as are efforts to manipulate cluster geometry and composition as well as hydride-coordination. Embryonic mechanistic studies are reported, as well as attempts to generate hydride-encapsulation clusters under catalytic control.     

Aluminum Hydride Catalyzed Hydroboration of Alkynes

An aluminum‐catalyzed hydroboration of alkynes using either the commercially available aluminum hydride DIBAL‐H or bench‐stable Et₃Al?DABCO as the catalyst and H‐Bpin as both the boron reagent and stoichiometric hydride source has been developed. Mechanistic studies revealed a unique mode of reactivity in which the reaction is proposed to proceed through hydroalumination and σ‐bond metathesis between the resultant alkenyl aluminum species and HBpin, which acts to drive turnover of the catalytic cycle.     

金属氢化物电极的化学活化

通过对Mm（NiMnCoAl）5电极的化学活化处理提高了金属氢化物电极的容量、电催化活性、活化性能和快速放电能力；讨论了化学活化处理对金属氢化物电极电化学性能的影响；在活化剂KBH4作用下，金属氢化物表面的氧化物技还原，在活化过程中一部分氢原子贮入合金之中，增加了电极的比表面，文中试验了这种活化方法对Ni／MH电池封口化成的作用，测试结果表明封口化成的AA型Ni-MH电池性能与开口化成电池的性能相当，其容量达到1050～1150mAh，1C、3C、SC信率下放电容量分别达到0．2C下的96．7％、89．0％、83．8％     

Analysis of Germanium Hydride Molecular Clusters

Isotope clusters in library electron ionization mass spectra of germanes often appear a few u lower than theoretically expected from elemental composition; for example, the dominant peak of the Ge₄H₁₀⁺ pattern is shifted 8 u down. This phenomenon is due to combinations of three essential components: the molecular ion Ge _n H_2n+2⁺ and two products of hydrogen elimination, Ge _n H⁺ and Ge _n ⁺. Using these components, isotope clusters can be accurately projected for germanium hydrides from Ge₂H₆ up to Ge₅H₁₂.     

Hydride and ammonia dispersion of metals

Chemical (hydride and ammonia) dispergation of Group II–V metals induced by hydrogen and ammonia in the temperature range of 100–500°C at a pressure of 0.5–2.0 MPa was studied. The phase transitions in the M-H₂ and M-NH₃ systems were investigated and conditions for metal hydride and nitride formation as highly dispersed powders were identified. The characteristic features of metal dispergation under the action of hydrogen and ammonia and the degrees of dispersity of the obtained powders were compared.     

Hydride atomization in graphite furnace atomizers

Summary A new type of graphite furnace atomizer — the graphite paper atomizer (GPA) — is described. The tube dimensions are large: l=92 mm, i.d.=9 mm. Analytical determinations of hydride forming traces were carried out in the absence and in the presence of hydride forming matrices using both a normal quartz tube atomizer (QTA) and the new GPA. The analyticalk results for pure solutions of the traces are the same for both atomizers. In the presence of hydride forming matrices the GPA gave improvements of 1 to 3 orders of magnitude for GPA. Chemical matrix modifications were employed to reduce matrix interferences of Se, Te (with Cu²⁺ ions) and Bi (with EDTA). It was possible to explain the types of interference by hydride forming elements. Thermodynamic calculations were made of the equilibrium composition in hydride vapours. The influence of temperature and hydrogen on the atomization in both atomizers has been studied. The AsSb molecule could be detected spectroscopically in appropriate hydride vapours.It was concluded that the main source of matrix interference by hydride forming matrices is the formation of diatomic molecules of the AsSb type between trace and matrix elements. At higher temperatures (about 2000–2300 K) the thermal atomization of the hydrides plays the main role.

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Hydridatomisierung in Graphitrohratomisatoren

Zusammenfassung Ein neuer Typ eines Graphitrohratomisators — der Graphitpapieratomisator (GPA) — wird beschrieben. Die Rohrdimensionen dieses Atomisators sind relativ groß: l=92 mm, i =9 mm. Analytische Bestimmungen von hydridbildenden Spuren wurden durchgeführt in Abwesenheit und in Gegenwart von hydridbildenden Matrices. Dabei wurde sowohl ein normaler Quarzrohratomisator als auch der neue Graphitpapieratomisator eingesetzt. Die analytischen Resultate waren, wenn nur reine Lösungen eingesetzt wurden, für beide Atomisatoren gleich. In Gegenwart von hydridbildenden Matrices ergaben sich jedoch für den Graphitpapieratomisator analytische Verbesserungen von 1–3 Größenordnungen. Chemische Matrixmodifikation wurde eingesetzt zur Verminderung der Matrixeinflüsse von Se, Te (durch Cu²⁺-Ionen) und von Bi (durch EDTA). Die Mechanismen der Störungen durch hydridbildende Matrices konnten geklärt werden. Thermodynamische Berechnungen der Gleichgewichtszusammensetzung in Hydrid-Dämpfen wurden ausgeführt. Verschiedene Experimente werden beschrieben zum Studium des Einflusses der Temperatur und des Wasserstoffs auf die Atomisierung von Hydriden in beiden Atomisatoren. Das AsSb-Molekül konnte auf spektroskopischem Wege in entsprechenden Hydrid-Dämpfen nachgewiesen werden. Die Schlußfolgerungen aus diesen Berechnungen und Experimenten sind:Der Hauptgrund für die Matrixeffekte hydridbildender Matrices ist die Bildung von zweiatomigen Molekülen zwischen Spur und Matrixelement. Bei höheren Temperaturen (2000–2300 K) spielt die thermische Atomisierung der Hydride die Hauptrolle.

     

Hydride abstraction in fast atom bombardment

Under fast atom bombardment conditions, compounds having long alkyl chains may exhibit [M ? H]⁺ as the major quasimolecular ion species, which can lead to incorrect assignment of molecular masses. It is shown that for a long-chain ether the loss of the hydride occurs from the hydrocarbon chain remote from the oxygen. This effect may yield information concerning ionization mechanisms in fast atom bombardment/mass spectrometry.