Thermodynamics of complex formation in dimethyl sulfoxide with ligands coordinating via N,P, As,Sb, OR Bi : III. A comparison between aromatic and aliphatic amines and phosphines

The stabilities of the complexes formed by silver(I), cadmium(II) and zinc(II) with tri-n-butylamine and tri-n-butylphosphine have been determined in dimethyl sulfoxide (DMSO). For the two latter metal ions, it has also been found that complexes are not formed in appreciable amounts with the triphenyl compounds Ph₃X, X = N, P and, in the case of cadmium(II), also As.From these and earlier measurements referring to DMSO as well as aqueous solutions, it was found that the stepwise stability constants increase by roughly one power of ten for each aromatic ring replaced by an aliphatic group, evidently as a consequence of the improved donor properties of the coordinating atoms. Further, for ligands of the same type, the stabilities are always markedly lower in DMSO than in aqueous solution. This is certainly due to the fact that the solvent molecules compete more strongly for the coordination sites in DMSO than in water, as reflected by the larger heats of solvation found in the former solvent for the metal ions concerned.     

Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part VII: Cyclodextrins with an inverse substitution pattern – synthesis and enantioselectivity

Transferring the site of specific substitution of dipentylated cyclodextrins with methyl or acyl residues from the secondary 3-hydroxyl group to the primary 6-hydroxyl group was expected to provide new information on the mechanism of chiral recognition. The 3-position points towards and the 6-position points away from the cyclodextrin cavity which via inclusion complex formation is supposed to play a major role in chiral separation. The “inverse” 6-O-acyl-2,3-di-O-pentyl-cyclodextrins displayed almost no enantioselectivity but the corresponding 6-O-methyl derivatives are a versatile supplement to the chiral capillary GC phases nowadays available. Among the compounds that could be enantiomerically resolved are alcohols, amino acids, alkyl halides, bicyclic ethers, acetals, olefins, other hydrocarbons and chiral pharmaceuticals.     

Über Pentaiodoplatinate M2PtI5 · 2 H2O (M  K,Rb, NH4). Gemischtvalente Verbindungen mit linear kettenförmigen,iodverbrückten Anionen

On Pentaiodoplatinates(II, IV) M₂PtI₅ · 2 H₂O (M ? K, Rb, NH₄). Mixed-valence Compounds with Linear Chain Iodobridged Anions Pentaiodoplatinates M₂PtI₅ · 2 H₂O (M ? K, Rb, NH₄) are obtainable by crystallization from aqueous solutions formed by dissolving of tetrachloroplatinates(II) in highly concentrated solutions of alkali iodides MI. The structural parameters were determinated from single crystal data. The compounds are classed with the group of linear chain mixed-valence platinum complexes from Wolffram's Salt type. In the crystal structures PtI₄-units are connected by asymnetric I-bridges to [PtI₄I_2/2] chains. There was no evidence of the existence of crystalline tetraiodoplatinates(II) M₂PtI₄.     

Über Kaliumdihalogenomonocyanomercurate(II) KHgX2CN · H2O (X = Cl,Br)

On Potassium Dihalogenomonocyanomercurates(II) KHgX₂CN · H₂O (X = Cl, Br) Hydrates of the dihalogenomonocyanomercurates KHgX₂CN · H₂O (X = Cl, Br) are obtained by reactions of equimoleculare amounts of HgX₂ and KCN in aqeuous solutions. The crystal structure of the rhombic KHgBr₂CN · H₂O (a = 454.2 pm; b = 1738.1 pm; c = 465.1 pm; Pmmm; Z = 2) contains linear HgBr₂ and Hg(CN)₂ groups and isolated Br^? and K⁺ ions. Therefore the compound can be formulated as a double salt Hg(CN)₂ · HgBr₂ · 2 KBr · 2 H₂O. The chloro compound is isotype.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. 58. Zur Kenntnis von 2-(Dimethylaminomethyl)ferrocenyl-Verbindungen des Vanadiums,Molybdäns,Wolframs, Thoriums und Urans

Contributions to the Chemistry of Transition Metal Alkyl Compounds. 58 On 2-(Dimethylaminomethyl)ferrocenyl Compounds of Vanadium, Molybdenum, Tungsten, Thorium, and Uranium Earlier results according to which dimethylaminomethylferrocenyl groups (FcN) are able to form stable organometallic chelate compounds were confirmed by synthesis of the heterobimetallic chelate compounds (FcN)₂VO · Li(acac) II , (FcN)MoO₂(acac) III , (FcN)WOCl₃ IV , (FcN)Th(acac)₃ V , and (FcN)UO₂(acac) VI from the corresponding metal acetylacetonates or oxidchlorides and (FcN)Li I . The new compounds were characterized by elemental analysis, the i.r., ¹H-n.m.r., and electron spectra and by their effective magnetic moments.     

Microdevices for manipulation and accumulation of micro- and nanoparticles by dielectrophoresis

Microfluidic devices with three-dimensional (3-D) arrays of microelectrodes embedded in microchannels have been developed to study dielectrophoretic forces acting on synthetic micro- and nanoparticles. In particular, so-called deflector structures were used to separate particles according to their size and to enable accumulation of a fraction of interest into a small sample volume for further analysis. Particle velocity within the microchannels was measured by video microscopy and the hydrodynamic friction forces exerted on deflected particles were determined according to Stokes law. These results lead to an absolute measure of the dielectrophoretic forces and allowed for a quantitative test of the underlying theory. In summary, the influence of channel height, particle size, buffer composition, electric field, strength and frequency on the dielectrophoretic force and the effectiveness of dielectrophoretic deflection structures were determined. For this purpose, microfluidic devices have been developed comprising pairs of electrodes extending into fluid channels on both top and bottom side of the microfluidic channels. Electrodes were aligned under angles varying from 0 to 75 degrees with respect to the direction of flow. Devices with channel height varying between 5 and 50 microm were manufactured. Fabrication involved a dedicated bonding technology using a mask aligner and UV-curing adhesive. Particles with radius ranging from 250 nm to 12 microm were injected into the channels using aqueous buffer solutions.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XLVI. Polarographisches Verhalten von Dibenzyl- und Diphenyltitan in aprotischen Lösungsmitteln

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XLVI. Polarographic Properties of Dibenzyl and Diphenyl Titanium in Aprotic Solvents The polarographic properties of dibenzyl and diphenyl titanium were investigated using acetonitrile (AN), dimethylformamide (DMF), and dimethylsulfoxide (DMSO) as solvents. Both compounds are reduced irreversibly at very negative potentials in a two-electron step with formation of titanium. The half-wave potentials depend on the donor strength of the solvents. With increasing donor number the half-wave potentials are shifted to more negative values. The fact that the limiting currents turned out to be diffusion controlled suggests a monomeric structure of the titanium diorganyls in AN, DMF, and DMSO.     

Influence of anchored cerium ions on the dispersity and activity of Pd/SiO2 catalysts

(Pd+Ce)/SiO₂ catalysts prepared by decomposition of organometallic complexes of Ce and Pd have higher activity, dispersity and selectivity in methanol synthesis than Pd/SiO₂ catalysts.

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, (Pd+Ce)/SiO₂ , Ce Pd, Pd/SiO₂.

     

Cathodoluminescence Depth Profiling in SiO2:Ge Layers

 For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary electron energy E ₀ = 2…30 keV. Applying a constant incident power regime (E ₀·I ₀ = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx. Thermally grown SiO₂ layers of thickness d = 500 nm have been implanted by Ge⁺-ions of energy 350 keV and doses (0.5–5)10¹⁶ ions/cm². Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of d_m≅240 nm are expected. Afterwards the layers have been partially annealed up to T _a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm.     

Darstellung und Kristallstruktur von Bis(heptaquocalcium)-dekachlorodithallat(III) [Ca(OH2)7]2TI2Cl10

Preparation and Crystal Structure of Bis(heptaquocalcium)-decachlorodithallat(III) [Ca(OH₂)₇]₂Tl₂Cl₁₀ Colourless, hygroscopic crystals of the compound CaTlCl₅ · 7H₂O were obtained by crystallization from aqueous solutions of CaCl₂ and TlCl₃. The crystal structure consists of [Ca(OH₂)₇]²⁺ cations and [Tl₂Cl₁₀]^4?anions.