Notiz über Li2PdO2

Note on Li₂PdO₂ For the first time we prepared ruby-red single crystals of Li₂PdO₂ by reaction with the wall 3 Na₂O + Li₂O₂ + ?Tb₄O₇”?(+ Pd) = 3 Na₂TbO₃ + Li₂PdO₂ + ?TbO₂”?, Pd-tube, 1100°C, 7 d. Single crystal data confirm the Li₂CuO₂-type of structure [a = 375.34(5), b = 298.18(4), c = 931.58(10) pm; spacegroup Immm; d_x = 4.85 g · cm^?3; 144 I₀(hkl); R = 3.54%, Rw = 3.19%; MoKα ; four-circle diffractometer Philips PW 1100] and reveal clearly different parameters compared with those deduced by powder data. The Madelung Part of Lattice Energy, MAPLE, corresponds now to the sum of the MAPLE values of the binary oxides.     

Polarizing a hydrophobic cavity for the efficient binding of organic guests: the case of calix[6]tren, a highly efficient and versatile receptor for neutral or cationic species

The host-guest properties of calix[6]tren 1 have been evaluated. The receptor is based on a calix[6]arene that is covalently capped at the narrow rim by a tren unit. As a result, the system presents a concave hydrophobic cavity with, at its bottom, a grid-like nitrogenous core. Despite its well-defined cavity and opening to the outside at the large rim, 1 did not behave as a good receptor for neutral molecules in chloroform. However, it exhibited efficient endo-complexation of ammonium guests. By contrast, the per-protonated host, 1.4H(+), behaved as a remarkable receptor for small organic molecules. The complexation is driven by a strong charge-dipole interaction and hydrogen bonds between the polar guest and the tetracationic cap of the calixarene. Finally, coordination of Zn(2+) to the tren core led to the asymmetrization of calixarene cavity and to the strong but selective endo-binding of neutral ligands. This study emphasizes the efficiency of a receptor presenting a concave hydrophobic cavity that is polarized at its bottom. The resulting combination of charge-dipole, hydrogen bonding, CH-pi, and van der Waals interactions highly stabilizes the supramolecular architectures. Also, importantly, the tren cap allows the tuning of the polarization, offering either a basic (1), a highly charged and acidic (1.4H(+)), or a coordination (1.Zn(2+)) site. As a result, the system proved to be highly versatile, tunable, and interconvertible in solution by simple addition of protons, bases, or metal ions.     

Study of ion chromatographic behavior of inorganic and organic antimony species by using inductively coupled plasma mass spectrometric (ICP-MS) detection

An on-line method for the analysis of Sb(III), Sb(V) and trimethylstiboxide (TMSbO) is presented. The separation is performed using ion chromatography (IC) on a strong anion-exchange column with phthalic acid plus 2% acteone at pH 5 as mobile phase. The chromatographic system is coupled to an ICP-MS as detector. The influence of different complexing agents on the chromatographic behavior of the antimony species is studied. Rather stable complexes of Sb(III) seem to be formed with citrate and tartrate under the experimental conditions. TMSbO forms a dianionic species with citrate in contrast to the otherwise monoanionic complex. Received: 31 Juli 1997 / Revised: 8 December 1997 / Accepted: 11 December 1997     

Über Fluoride des zweiwertigen Eisens: Ba2[Fe3F10]

On the Knowledge of Ba₂[Fe₃F₁₀] For the first time colourless single crystals of Ba₂Fe₃F₁₀ have been prepared by reduction of a mixture of 3 BaF₂/7 FeF₃ in a Fe-tube (reaction with the wall 750°C, 60 d). Ba₂Fe₃F₁₀ crystallizes in the monoclinic spcgr. P2₁/c with a = 788.3(1), b = 623.0(1), c = 1868.0(3) pm, β = 111.79(1)º, Z = 4. (Fourcircle diffractometer PW 1100, Fa. Philips, MoKα, 2383 of 2383 I₀(hkl), R = 8.1%, R_w = 4.1%, parameters see in the text). The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Acidity functions of aqueous fluorinated acid solutions by differential pulse polarography

The acidity functions of aqueous trifluoroacetic and trifluoromethanesulphonic acid mixtures, and aqueous hexafluoropropane-2, 2-diol solutions, have been determined by differential pulse polarography. The apparent shift of the half-wave potential for the ferrocene—ferricinium couple, as the solvent composition is changed, is used to indicate the change in potential of a glass electrode; acidity is measured as the H_GF acidity function. The densities of two of these solvent systems as a function of composition are also reported. Trifluoromethanesulphonic acid—water mixtures represent the strongest aqueous acid solvent system so far studied.     

Novel Access to Furan-3-thiols and Derivatives,Impact Meat-Flavor Compounds

A versatile process for the preparation of a number of 3-thio-substituted furans 1–4 is described. These products have very low odor thresholds and are thus potent flavor compounds. Fur-3-yl thiocyanates 10a , b as well as other S-containing analogues ( 2b , 7a , b , and 8 ) were prepared by a Michael-type addition of thiocyanic acid, thioacetic acid, alakanethiols, and sodium thiosulfate to alkynones 6 or 15 , followed by cyclization (Schemes 3 and 4). The thiocyanates 10a, b were converted to mixed disulfides 3 , symmetric disulfides 4 , thioethers 2 , and thiols 1 , using ‘hard’ or ‘soft’ nucleophiles or reducing agents, respectively (Scheme 6).     

Das erste Oxomanganat(III) mit Inselstruktur: Zur Kenntnis von Na5[MnO4]

The First Oxomanganate (III) with Isolated Anion Structure. On Na₅[MnO₄] For the first time, Na₅[MnO₄] has been prepared from the binary oxides [500°C, 14 d, Ag-cylinders] as a red powder and in form of red single crystals. The orthorhombic structure (a = 5.822, b = 7.769, c = 6.005 Å, 609 I_o(hkl), R = 0.030, MoKα, 2-circlediffractometer data (Stasi, Fa. Stoe)) is characterized by strongly compressed [MnO₄] groups. Effective coordination numbers, ECoN, as well as the madelung part of lattice energy, MAPLE, are calculated and discussed.     

N(SCl)2 ⊕[MoCl5(NSCl)]⊖, ein Chlorthionitrenokomplex von Molybdän(VI)

N(SCl)₂^⊕ [MoCl₅(NSCl)]^?, a Chlorothionitrene Complex of Molybdenum (VI) . The title compound is formed together with MoCl₃(N₃S₂) by the reaction of MoCl₄ or MoCl₅ with (NSCl)₃ in CH₂Cl₂. The black, crystalline compound was characterized by its i.r. spectrum and an X-ray crystal structure determination. N(SCl)₂^⊕[MoCl₅(NSCl)]^? crystallizes in the monoclinic space group P2₁/n with four formula units per unit cell. The lattice constants are a = 716.3, b = 1627.4, c = 1178.9 pm and β = 100.90°. The [MoCl₅(NSCl)]^? ion posseses an almost linear Mo = N = S grouping with bond lengths that can be interpreted as double bonds. Crystal data for AsPh₄[MoCl₅(NSCl)] are reported.     

Formation and Crystal Structure of Stable Five‐coordinate Diorgano Cobalt(III) Complexes

The mer‐octahedral complexes(2‐carbonyl)(4‐Me)(6‐tBu)phenolato[C,O]hydridotris(trimethylphosphine)cobalt(III) ( 1 ) or ‐(1‐carbonyl)(2‐oxo)(1,2‐diphenylethene)[C,O]hydridotris(trimethylphosphine)cobalt(III) ( 2 ) via formal insertion of propynoic acid ethyl ester into Co‐H functions afford pentacoordinate vinylcobalt(III) 3 and 4 , respectively, that are diamagnetic and attain a square pyramidal structure as exemplified by an X‐ray diffraction analysis of 3 .