Influence of the trans Substituent on N2 Bonding in Iron(ii)–Phosphane Complexes: Structure,Synthesis, and Properties of the Monomeric Adducts trans-[FeXN2(depe)2]BPh4, X=Cl,Br

Not a dimer but a monomer was found in the X-ray structure analysis of the complex “trans-[{FeCl(depe)₂}₂(µ-N₂)](BPh₄)₂” (depe=Et₂PCH₂CH₂PEt₂). The complexes [FeXN₂(depe)₂]BPh₄ (X=Cl, Br; structure of the cation for X=Cl shown on the right) are much less stable than the analogous hydride compounds and undergo N₂ exchange at room temperature even in the solid state.     

Oscillation of nonlinear differential systems with retarded arguments

In this work we investigate some oscillatory properties of solutions of non-linear differential systems with retarded arguments. We consider the system of the form

Ein ungewöhnlicher trimerer Bimetallkomplex mit dem Gerüst [Zr3(μ2-OH)3(μ3-O)Li5] durch Reaktion von Zirconiumorgano- und -hydrido-Komplexen mit Wasser

An Unusual Trimeric Bimetallic Li? Zr Complex with the Backbone [Zr₃(μ₂-OH)₃(μ₃-O)Li₅] by Reaction of Zirconiumorgano and Hydrido Complexes with Water The reaction of compounds of the type [(LZr)(LiH)(L′)]_n and [(LZr)(LiH)(L′)(alkyne)]_n (L: 2,2′-Biphenolato-dianion, L′: thf, Bu₃P, alkyne: Ph? C?C? SiMe₃, CH?CH) with water at 0°C in a thf solution results in the formation of th trimeric bimetallic complex 8 [(L₂Zr)₃(μ₂-OH)₃(μ₃-O)Li₅(thf)₈(H₂O)₅] in 50% yield. The X-ray analysis of 8 shows that a planar six-membered ring Zr₃(μ₂-OH)₃ is formed. In the middle of this ring is a dianionic oxygen atom placed, coordinating to the three L₂Zr centres in a planar μ₃-coordination (bond angles 120,05μ). Five lithium ions stabilize the anionic backbone by bridging the biphenolato chelate ligands, which form seven-membered chelate rings with the atoms. ¹H-, ¹³C-, and ⁷Li-NMR spectra exhibit that the solid state structure remains unchanged in solution (thf).     

Effective elasticity coefficients of native rocks and consolidated granular matter

The elastic coefficients of binary heterogeneous materials, such as several native rock materials or consolidated granular matter will be determined in terms of a perturbation expansion. Furthermore, in order to check the validity of the obtained results, these are compared with numerical investigations using Boole's model of randomly distributed spheres. Finally, we apply the results on several classes of native rocks and consolidated granular materials.     

Bis(diphenylphosphino)amid-komplexe des platins,palladiums und nickels. Kristallstruktur des N-methylierungsprodukts {CH3N[(C6H5)2P]2}2Pd2+ 2SO3F−

Reaction of lithiated bis(diphenylphosphino)amine, [(C₆H₅)₂P]₂N^? Li⁺, with K₂PtCl₄ or PdCl₂ (in the presence of trimethylphosphine) yields the homoleptic bis[bis(diphenylphosphino)amide] complexes I and II, respectively. With NiCl₂/(CH₃)₃P the chloro-bridged dinuclear complex III is obtained. A symmetrical bonding of the Ph₂P-·N-·PPh₂ anion to the metal through the phosphorus atoms is indicated for these diamagnetic, deep-yellow (I, II) or red (III) complexes by ³¹P NMR spectroscopy (J(PtP) 1812 Hz for I). I and II are dissolved in CF₃COOH with protonation at the nitrogen atoms to give bis(diphenylphosphino)amine complexes IV and V, respectively (J(PtP) 2080 Hz for IV). IV and V are 1:2 electrolytes in CH₃NO₂. Methylation of I-III with CH₃OSO₂F leads to the bis(diphenylphos-phino)methylamine complexes VI-VIII, of which the palladium compound VII has been structurally characterized by single crystal X-ray diffraction. VII contains a planar CNP₂PdP₂NC skeleton and is thus based on planar ligand arrays both at Pd and at the two N atoms.     

A Generalized Bell Inequality and Decoherence for the K0KO

First, a generalized Bell inequality for different times and for different quasi-spin states is developed. We focus on special quasi-spin eigenstates and times. The inequality based on a local realistic theory is violated by the CP-violating parameter [1] if the quantum theory is used to recalculate the probabilities. Next, the quantum mechanical probabilities are modified by the decoherence approach, which enables the initial state to factorize spontaneously. In this way we get a lower limit for the decoherence parameter , which measures the degree of decoherence. This result is compared with the experimental value [2, 3] of the decoherence parameter deduced from the data of the CPLEAR experiment [4].     

Enantioselective silica-based monoliths modified with a novel aminosulfonic acid-derived strong cation exchanger for electrically driven and pressure-driven capillary chromatography

Silica monoliths modified with trans-(1S,2S)-2-(N-4-allyloxy-3,5-dichlorobenzoyl)amino cyclohexanesulfonic acid were tested for enantioselective separations of various chiral bases by aqueous and nonaqueous CEC as well as nano-HPLC. The optimization of the immobilization procedure showed that an intermediate selector (SO) coverage, as does result from a single static immobilization cycle in the capillary at 60 degrees C with an 8% (m/v) SO solution in methanol, affords maximal EOF and optimal enantioselectivity values, while a second immobilization cycle does not lead to any improvements. Furthermore, the mobile phase composition was examined regarding the effectiveness of aqueous phases (ACN/water and methanol/water) compared to nonaqueous eluents (ACN/methanol) in terms of separation selectivity and efficiency. Additionally, different acids of varying strengths were tested as co-ions in the ion-exchange process, including formic acid, acetic acid, methanesulfonic acid, and TFA (pK(a) from 4.75 to 0.5). It turned out that the effects regarding EOF and enantioselectivity were largely negligible. The chromatographic efficiencies of the new capillary columns were compelling and remarkable for bases. H-u curves established for mefloquine revealed a C-term contribution (resistance to mass transfer) by a factor of about six lower in CEC than in nano-HPLC and an A-term (flow maldistribution) about three times lower in the CEC mode. Theoretical plate heights as low as around 3-5 mum could be obtained in CEC over a wide flow range (0.5-1.5 mm/s). Run-to-run repeatabilities like in HPLC and excellent system stability promise the practical usefulness of the novel monolithic capillary column for enantiomeric composition analysis of pharmaceuticals by CEC.     

Quinoidal tetrazines: formation of a fascinating compound class

A series of different N-heterocyclic carbenes (NHCs) were reacted with 3,6-bis(3',5'-dimethylpyrazolyl)-tetrazine in the presence of an inorganic carbonate to provide access to a hitherto unprecedented compound class. The formed tetrazine derivatives bearing the NHC in the 3-position and an oxygen in the 6-position show a quinoidal-like structure, according to physical examinations and X-ray crystallography.