Beiträge zur Chemie des Phosphors. 235. Zur Darstellung größerer Mengen von Diphosphan(4) im Laboratorium

Contributions to the Chemistry of Phosphorus. 235. On the Preparation of Larger Amounts of Diphosphane(4) in the Laboratory The preparation of several hundred grammes of diphosphane(4) by hydrolysis of calcium phosphide in a semicontinuous process as well as the handling of larger amounts of this compound are reported. In comparison with earlier results [12], the yield has been raised by 37 percent with simultaneous increase of the accessible total amount. The white solid which is formed in the preparation and purification of diphosphane(4) is not, as was believed in earlier work [25, 8], triphosphane(5) or another, novel phosphorus hydride but is rather a clathrate compound of diphosphane(4) or the phosphanes P_nH_n+2 (n = 2–4) and water, respectively.     

Synthesis and reactivity of rhodium(III) pentamethylcyclopentadienyl complexes of N-B-PTA(BH3): X-ray crystal structures of [CpRhCl2{N-B}-PTA(BH3)] and [CpRh{N-B-PTA(BH3)}(η-CH2 = CHPh)]

The reaction between 1-boranyl-1,3,5-triaza-7-phosphaadamantane ligand N-B-PTA(BH₃) and [Cp^∗RhCl(μ-Cl)]₂ affords [Cp^∗Rh{N-B-PTA(BH₃)}Cl₂] (3) or [Cp_∗Rh{N-B-PTA(BH₃)}₂Cl]Cl (5) containing one or two P-bonded boronated PTA ligands. The hydride [Cp_∗Rh{N-B-PTA(BH₃)}H₂] (8) was also obtained by reaction of 3 with NaBH₄ and alternatively by direct hydroboration of [Cp^∗Rh(PTA)Cl₂] with excess NaBH₄. Moderately slow hydrolysis of the N-boranyl rhodium complexes affords dihydrogen, H₃BO₃ and the corresponding PTA derivatives, including the water-soluble dihydride [Cp^∗Rh(PTA)H₂] (9). Finally, the reaction of 8 with electron poor alkynes gives the alkene complexes [Cp^∗Rh{N-B-PTA(BH₃)}(η²-CH₂ = CHR)] (R = Ph, 10; C(O)OEt, 11) as a mixture of rotamers η²-coordinated to rhodium without affecting the N-BH₃ moiety. The X-ray crystal structures of 3 and 10 were also obtained and are here discussed.     

Formation region and hydrogen storage abilities of perovskite-type hydrides

Formation region and hydrogen desorption and absorption properties of the perovskite-type structure in Li_xNa_1−xMgH₃ with x = 0, 0.17, 0.33, 0.50 and 1.00 were studied in the present work. The experimental results are reasonably explained from the viewpoint of the geometric restrictions of ions that are described by so-called Goldschmidt tolerance factors. In NaMgH₃ (x = 0), two plateau pressures of about 0.040 and 0.15 MPa were clearly detected by hydrogen pressure–composition (p–c) isotherm measurement at 673 K. Moreover, NaMgH₃ can be reversibly formed in 1.0 MPa of hydrogen at 673 K, from the decomposed phase of elemental Na and Mg.     

氢化物发生原子荧光光谱法测定镍基高温合金中痕量硒和碲

研究了用氢化物发生原子荧光光谱法测定镍基高温合金中痕量硒和碲。试验了氢化物发生的最佳条件、酸度和还原剂加入量以及在断续流动条件下镍、钴的干扰 ,并采用柠檬酸对其干扰进行抑制。提出了一个直接快速和准确测定镍基高温合金中硒和碲的分析方法 ,硒和碲的测量下限可达 5× 1 0 -5%。     

Activation of the Ge-H bond of Et3GeH in photochemical reaction with molybdenum(0) carbonyl complexes and hydrogermylation of norbornadiene

The germane intermediate σ-complexes, characterized by high-field resonances in the region from −6 to −8 ppm, have been detected during the ¹H NMR spectroscopy monitoring of the photochemical reaction of Et₃GeH with Mo(CO)₆, [Mo(CO)₄(η⁴-cod)], and [Mo(CO)₄(η⁴-nbd)] in the NMR tube. The activation of the Ge-H bond of germane in photochemical reaction of the norbornadiene (nbd) complex [Mo(CO)₄(η⁴-nbd)] has been applied in the hydrogermylation of norbornadiene, which leads to the formation of triethylgermylnorbornene.     

Adsorption and thermal decomposition of diethylaluminum hydride on Si(1 0 0)-2 × 1

Chemistry of organoaluminum compounds on silicon surfaces forms a foundation of chemical vapor deposition (CVD) for the formation of metal-semiconductor interconnects. We have applied multiple internal reflection Fourier-transform infrared spectroscopy and thermal desorption mass spectrometry to analyze the chemistry of one of the promising Al-CVD precursors, diethylaluminum hydride, on a Si(1 0 0)-2 × 1 surface. Diethylaluminum hydride adsorbs molecularly on this surface both at room temperature and at 100 K. Thermally induced surface reaction consumes the monolayer of adsorbed organoaluminum molecule. The only hydrocarbon product is ethylene desorbing from the silicon surface around 600 K. Despite a clean reaction that removes carbon from the surface, aluminum deposition is not significant because of the formation of alane products.     

Mechanism of GeH4 dissociation on Si(1 1 1)-(7 × 7)

Results of an STM study of dissociative GeH₄ adsorption on Si(1 1 1)-(7 × 7) at 300 K show that GeH₄ adsorbs under scission of two Ge-H bonds according to GeH₄(g) + 4db → GeH₂(ad) + 2H(ad). GeH₂ binds to two adatom dangling bonds in a bridged configuration, while the two released hydrogen atoms saturate two additional dangling bonds. The GeH₄ sticking coefficient under these conditions is 1.2 × 10⁻⁶, one order of magnitude smaller than for SiH₄.     

A synchrotron study of high-pressure transformations in TiH0·74

Abstract

The crystal structure of the TiH_0·74 alloy was studied by the energy dispersive X-ray diffraction technique in the pressure range to 30·5 GPa at temperatures to 630 K. A phase transformation to the (η + ω) two-phase state was found to occur above 7 GPa at room temperature, then (η+ω)-TiH_0·74 remained stable up to P=30·5 GPa. Another phase transformation resulting in a single-phase state, ζ-TiH_0·74, was found to occur upon heating (η+ω)-TiH_0·74 above T ? 560 K. Both high-pressure phases, η and ζ, were indexed on the basis of the tetragonal sublattices of the Ti atoms with nearly the same specific volumes. It is assumed from the relation of the specific volumes that the hydrogen atoms occupy the tetrahedral interstices in the ζ-phase and the octahedral interstices in the η-phase.     

YMgGa as a hydrogen storage compound

The hydrogen absorption and desorption properties of the recently found ternary phase YMgGa have been studied. This compound absorbs 2.2 wt% hydrogen during the first cycle, but only 1.1 wt% can be stored reversibly for the following cycles under the applied pressure and temperature conditions. Hydrogen absorption and desorption properties were investigated by measuring the thermal desorption spectra and the pressure-composition isotherms while the crystal structure was determined using X-ray diffraction (XRD). The compound absorbs hydrogen at pressures above 0.2 MPa and 250 °C by decomposing into YH₃ and MgGa. This reaction is reversed when heating the hydride in a He atmosphere; hydrogen is released and the YMgGa phase is partially recovered together with YGa₂ and YH₂. The reformation of YMgGa occurs at temperatures below 450 °C on the expenses of hydrogen desorption from YH₂. This is not expected under these temperature conditions as YH₂ normally does not desorb hydrogen below 800 °C.     

Das Indid‐Hydrid Ba9[In]4[H]: Synthese,Kristallstruktur, NMR‐Spektroskopie,Chemische Bindung

The new indide hydride Ba₉[In]₄[H] was synthesized from the elements in stoichiometric proportions using the inherent hydrogen content of commercial elemental barium as hydrogen source. Its structure, constituting a new type, was determined using single‐crystal X‐ray data (tetragonal, space group I4/m, a = 1397.3(2), c = 591.8(1) pm, Z = 2) in sufficient quality (R1 = 0.0261) to allow identification and location of the hydride ion as well as the refinement of its thermal parameter. The crystal structure of Ba₉[In]₄[H] exhibits isolated indium atoms, which are coordinated by 10 barium cations in a cubicosahedral arrangement. The hydride anions are octahedrally surrounded by six Ba²⁺ cations. According to [HBa₄Ba_2/2] these octahedra are connected by opposite corners to form chains running along the c axis. The presence of the hydride ion was determined by solid state NMR spectroscopy, where the chemical shift of the ¹H‐MAS‐NMR signal of–9.0 ppm nicely corresponds to the values in BaH₂ and other metallid hydrides. Like in other binary alkaline‐earth indides, the band structure calculated in the frame of the FP‐LAPW methods shows a pseudo band gap slightly above the Fermi level, associated with the electron precise valence electron count after Zintl (isolated In^5–). The title compound was compared to other hydrides and indides both according to the structural as well as the bonding features.