An Unexpected Diboroxane: Crystal Structure of Me2HN · (CF3)2BOB(CF3)2 · NHMe2

(CF₃)₂BNMe₂ ( 1 ) reacts at room temperature with water in a 2:1 ratio to form bis(dimethylamine)‐tetrakis(trifluoromethyl)diboroxane Me₂HN·(CF₃)₂BOB(CF₃)₂·NHMe₂ ( 2 ), whereas a 1:1 ratio at —78 °C had yielded HO(CF₃)₂B·NHMe₂ ( 3 ). The constitution of 2 has been deduced from multinuclear NMR, IR and mass spectra, and the structure has been determined by single‐crystal X‐ray diffraction. Averaging 1.396(6) Å, the B—O bond length is short, and the B—O—B bond angle, 150.4(3)°, is very wide.     

Heterodinukleare Cobalt(II)‐, Nickel(II)‐, Kupfer(II)‐, Zink(II)und Palladium(II)‐Komplexe mit einem makrocyclischen Liganden vom Schiff‐Basen‐Typ: Synthesen und Strukturen

Complexes with Macrocyclic Ligands. IV. Heterodinuclear Cobalt(II), Nickel(II), Copper(II), Zinc(II) and Palladium(II) Complexes with a Macrocyclic Ligand of Schiff‐Base Type: Syntheses and Structures The synthesis and properties of nickel(II), copper(II), and palladium(II) complexes, [ML^Ph] ( 3 ; L^Ph = N,N′‐phenylene‐bis(3‐formyl‐5‐tert.‐butyl‐salicylaldimine)), are described. These neutral mononuclear complexes react with metal(II) perchlorate and 1,3‐propylenediamine to form heterodinuclear, macrocyclic, cationic complexes of the type [MM′(L^Ph,3)]²⁺ ( 4 ; M = Ni, Cu, Pd; M′ = Co, Cu, Zn). The structures of the five new compounds [NiCo(L^Ph,3)](ClO₄)₂, [NiCu(L^Ph,3)](ClO₄)₂, [CuCu(L^Ph,3)](ClO₄)₂, [CuZn(L^Ph,3)](ClO₄)₂, and [PdCu(L^Ph,3)](ClO₄)₂ were determined by X‐ray diffraction.     

A gas chromatography/combustion/isotope ratio mass spectrometry system for high-precision delta13C measurements of atmospheric methane extracted from ice core samples

Past atmospheric composition can be reconstructed by the analysis of air enclosures in polar ice cores which archive ancient air in decadal to centennial resolution. Due to the different carbon isotopic signatures of different methane sources high-precision measurements of delta13CH4 in ice cores provide clues about the global methane cycle in the past. We developed a highly automated (continuous-flow) gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) technique for ice core samples of approximately 200 g. The methane is melt-extracted using a purge-and-trap method, then separated from the main air constituents, combusted and measured as CO2 by a conventional isotope ratio mass spectrometer. One CO2 working standard, one CH4 and two air reference gases are used to identify potential sources of isotope fractionation within the entire sample preparation process and to enhance the stability, reproducibility and accuracy of the measurement. After correction for gravitational fractionation, pre-industrial air samples from Greenland ice (1831 +/- 40 years) show a delta13C(VPDB) of -49.54 +/- 0.13 per thousand and Antarctic samples (1530 +/- 25 years) show a delta13C(VPDB) of -48.00 +/- 0.12 per thousand in good agreement with published data.     

An a posteriori error estimate for a dual mixed method applied to Stokes system with non-null source terms

Advances in Computational Mathematics - We propose and analyze a time-stepping Crank-Nicolson(CN) alternating direction implicit(ADI) scheme combined with an arbitrary-order orthogonal spline...     

Dinukleare Kupfer(II)‐Komplexe mit chiralen makrocyclischen Liganden vom Schiff‐Basen‐Typ: Synthesen und Strukturen

Complexes with Macrocyclic Ligands. V Dinuclear Copper(II) Complexes with Chiral Macrocyclic Ligands of Schiff‐Base Type: Syntheses and Structures The synthesis and properties of four chiral, dinuclear, macrocyclic, cationic copper(II) complexes, [Cu₂(L^m,n)]²⁺ ( 1 – 4 ), are described. The two symmetrical compounds [Cu₂(L^2,2)][ClO₄]₂ ( 1 and 2 ) were synthesized in a one‐step reaction from 2,6‐diformyl‐4‐tert.‐butylphenol, copper(II)‐perchlorate and the chiral diamine (1S,2S)‐1,2‐diphenylethylenediamine (synthesis of 1 ) and (1R,2R)‐1,2‐diaminocyclohexane (synthesis of 2 ), respectively. For the synthesis of the two unsymmetrical compounds [Cu₂(L^Ph,n)][ClO₄]₂ ( 3 and 4 ) the mononuclear, neutral copper(II) complex [CuL^Ph] ( 5 ) [synthesized from 2,6‐diformyl‐4‐tert.‐butylphenol, copper(II)‐acetate and 1,2‐phenylenediamine] was reacted with (1R,2R)‐1,2‐diaminocyclohexane (synthesis of 3 ) and (S)‐1,1′‐binaphthyl‐2,2′‐diamine (synthesis of 4 ), respectively. The structures of the two unsymmetrical copper(II) compounds ( 3 and 4 ) were determined by X‐ray diffraction.     

Kristall- und Molekülstruktur der solvatfreien Hexamethyldisilazide des Rubidiums und Caesiums und die Kristallstruktur eines Toluolsolvates

Crystal and Molecular Structure of the Solventfree Hexamethyldisilazides of Rubidium and Cesium and the Crystal Structure of a Toluene Solvate X-ray crystal structures are reported for the dimeric rubidium and cesium hexamethyldisilazides [MN(SiMe₃)₂]₂. [RbN(SiMe₃)₂]₂ ( 1 ) crystallizes in the monoclinic space group P2₁/c with a = 1044.7(2), b = 891.1(2), c = 1281.0(3) pm, β = 100.26(2) °, Z = 2. [CsN(SiMe₃)₂]₂ ( 2 ) crystallizes in the orthorhombic space group Pbca with a = 1270.81(2), b = 1281.16(1), c = 1539.65(2) pm, Z = 4. Both compounds contain a four-membered [M–N–]₂-ring located on an inversion centre. The M–N bond lengths are: 287.8(2), 295.6(2) pm ( 1 ) and 307.4(2), 314.9(2) pm ( 2 ). The solvate [CsN(SiMe₃)₂]₂ · C₇H₈ ( 3 ) crystallizes from toluene in the triclinic space group P1 with a = 854.00(2), b = 979.58(2), c = 1084.45(3) pm, α = 111.482(1), β = 93.821(1), γ = 108.546(1)°, Z = 1. In this compound dimeric units [CsN(SiMe₃)₂]₂ and toluene molecules form a polymeric chain.