Dilead(II) trimercury(II) tetraoxide chromate(VI), Pb2(Hg3O4)(CrO4)

Pb₂(Hg₃O₄)(CrO₄) consists of [CrO₄]²⁻ tetra­hedra, linear O—Hg—O dumbbells and divalent Pb atoms in [3+5]‐coordination. The HgO₂ dumbbells are condensed into [Hg₃O₄]²⁻ units and can be regarded as a section of the HgO structure. The [Hg₃O₄]²⁻ complex anions are connected by inter­stitial Pb²⁺ ions, while the [CrO₄]²⁻ tetra­hedra are isolated.     

Synthesis and Crystal Structure of Bis(tetraethylammonium) Octabromo‐triselenate(II)‐{dibromodiselenate(I)}, [NEt4]2[Se3Br8(Se2Br2)], the Salt of a Mixed‐valence Bromoselenate(II,I) Anion

The brown crystals of [NEt₄]₂[Se₃Br₈(Se₂Br₂)] ( 1 ) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of tetraethylammonium bromide. The crystal structure of 1 has been determined by the X‐ray methods and refined to R = 0.0308 for 10433 reflections. The crystals are monoclinic, space group P2₁ with Z = 2 and a = 12.0393(3) Å, b = 11.8746(3) Å, c = 13.1946(3) Å, β = 96.561(1)° (123 K). In the solid state structure the anion of 1 is built up of Se₃Br₈ unit which consists of a triangular arrangement of three planar SeBr₄ units sharing a common edge through two μ₃‐bridging Br atoms, and one Se₂Br₂ molecule which is linked to one of μ₃‐bridging Br atoms. The three Se^II atoms form a triangle which is almost perpendicular to the planes given by three SeBr₄ moieties. The contact between the μ₃Br and the Se^I atom of the Se₂Br₂ molecule is 3.1711(8) Å and can be interpreted as a bond of the donor‐acceptor type with the μ₃Br as donor and the Se₂Br₂ molecule as acceptor. The terminal Se^II‐Br and μ₃Br‐Se^II bond lengths are in the ranges 2.3537(7)–2.4737(7) Å and 2.7628(7)–3.1701(7) Å, respectively. The bond lengths in coordinated Se₂Br₂ molecule are: Se^I‐Se^I = 2.2636(9) Å, Se^I‐Br = 2.3387(11) and 2.3936(8) Å.     

电解池电阻和容抗的快速测定仪

利用锁定放大器, 恒电势仪, 压控频率正弦波信号发生器等组装成电解池电阻和容抗的快速测定仪。可以快速地自动测是和绘出阻抗谱图和电阻/容抗～时间图。采用微小恒定振幅正弛交流电流(<10 μA)作为微扰, 数据可能较为可靠。给出了线路及所需滤波器元件的数据, 说明仪器各部份之间的干扰可以减少。测定了滴汞电极在1 mol L~(-1)Na_2SO_4溶液中及1 mol L~(-1)Na_2SO_4被正庚醇饱和的溶液中的微分电容～电势数值。证明仪器工作良好。另外, 从实验数据和理论分析, 均表明D.C.Grahame的被广泛引用的有关经典数据有误。本文做了修正。还测定了半导体氧化铁电极在光照下黑暗中的阻抗谱图和氧化银电极充电和停止充电后开路下的电阻～时间图, 显示了仪器在电化学研究中利用的可能性。     

Cation-Response Mechanism of Neutral Carrier Based Ion-Selective Electrode Membranes

Results of voltammetric, potentiometric, chronoamperometric, ion transport, and extraction studies on neutral carrier based, plasticized poly(vinyl chloride) membranes are summarized. They unambiguously confirm that such bulk membranes dispose of immobile anionic sites. These fixed sites lead to a Donnan exclusion of other anions from the membrane and thus to a permselectivity for cations. The results are in perfect agreement with the predictions of earlier membrane models. A rigorous Poisson-Boltzmann analysis of macroscopic liquid membranes clearly indicates that space-charge at the membrane/solution interfaces does not influence the electrochemical properties and the ion-selectivity behavior at steady state.     

3,7-Dioxaazelaamides as Ionophores for Lithium Ion Selective Liquid Membrane Electrodes

Lipophilic neutral carriers were synthesized which show Li⁺/Na⁺ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li⁺ in blood serum within the clinical concentration range. A 1:1 Li⁺/ionophore complex of one representative (N,N,N′,N′-tetracyclohexyl-5,5-dimethyl-3,7-dioxaazelaamide) has been prepared, and its structure was elucidated by X-ray analysis.     

Die chemie der schweren carben-analogen R2M,M = Si,Ge, Sn: IX. Eigenschaften und thermolyse von neuen 7-silabicyclo[2.2.1]heptadienen

Factors governing the ease and mechanism of 7-silabicyclo[2.2.1]heptadienes thermolysis in order to generate free silylenes and the corresponding benzene derivatives are investigated. For this purpose, 29 new compounds of the types VII–X have been prepared. No indications for a polar mechanism or an intermediate biradical could be found. The degradation is exactly of first order in all cases investigated sofar, and is enhanced by phenyl groups at the bridgehead C atoms, if a conformation coplanar with the basic ring is allowed by the neighbouring substituents, but is not enhanced by phenyl groups at the Si. The X-ray structure of two typical derivatives is discussed with this respect. A special mechanism is operating in the easy thermolysis of carbomethoxy-substituted compounds leading to cyclic sila enolether intermediates.     

Reaction of Anthranilamide with Phosphorus Pentasulfide: Formation of 2-Mercapto-(1H)-1,3,2λ5-benzodiazaphosphorine-2,4-dithione

The reaction of anthranilamide with phosphorus pentasulfide in boiling pyridine leads to the benzodiazaphosphorine-pyridine salt 2 . The structure is established by elemental analysis, ¹H- ¹³C- ¹⁵N- ³¹P-NMR, and mass spectral data.