Syntheses and Crystal Structures of Copper and Silver Complexes with the Ylide Ph3PCHP(O)PPh2 as Ligand

The reactivity of the hydrolysis product of hexaphenylcarbodiphosphorane, PPh₃CHP(O)Ph₂, towards different soft Lewis acids, such as CuI and Ag[BF₄] are reported. While CuI exclusively binds at the ylidic carbon atom, reaction of the silver cation in CH₂Cl₂ leads to proton abstraction from the solvent to give the cation [PPh₃CH₂P(O)Ph₂]⁺. Surprisingly, Ag⁺ replaces the methyl group of [PPh₃CHMeP(O)Ph₂]⁺ to produce a dimeric complex, in which Ag⁺ is coordinated to C and O forming an eight membered ring. The compounds were characterized by spectroscopic methods and X‐ray diffraction.     

Azidoberyllate mit Adamantanstruktur: Synthese,IR‐Spektren und Kristallstrukturen von (Ph4P)2[Be4X4(μ‐N3)6] (X = Cl,Br)

Azido Beryllates with Adamantan‐like Structures: Synthesis, IR Spectra, and Crystal Structures of (Ph₄P)₂[Be₄X₄(μ‐N₃)₆] (X = Cl, Br) The azido beryllates (Ph₄P)₂[Be₄X₄(μ‐N₃)₆] (X = Cl 1a , X = Br 1b ) have been prepared by the reaction of Me₃SiN₃ with the halogeno beryllates (Ph₄P)₂[Be₂Cl₆] and (Ph₄P)₂[Be₂Br₆], respectively, in CH₂Cl₂ and CH₂Br₂ solution, respectively. Both complexes form moisture sensitive, colourless crystals, which are nonexplosive with respect to mechanical or thermal stress. They are characterized by IR spectroscopy and by crystal structure determinations. 1a and 1b crystallize isotypically in the space group C2/c with 12 formula units per unit cell. Whereas 1a was only refined to R₁ = 0.13, which is caused by disordering, 1b could be refined to R₁ = 0.066. The structures contain adamantanlike dianions [Be₄X₄(μ‐N₃)₆]^2— with two symmetry nonequivalent individuals which differ only slightly from one another. The Be₄N₆ core is formed by bridging function of the α‐nitrogen atoms of the azide groups with BeN bond lengths of 172.5 and bond lengths N_α—N_β = 123.2 pm and N_β—N_γ = 113.1 pm on average in the structure of 1b .     

Metallic behavior of the Zintl phase EuGe2: combined structural studies, property measurements, and electronic structure calculations

The Zintl compound EuGe₂ crystallizes in the trigonal space group (No. 164) with the CeCd₂-structure type. Its structure can be formally derived from the hexagonal AlB₂-structure type by a strong puckering of the hexagonal layers. The chemical bonding in EuGe₂ can be rationalized according to the Zintl concept as (Eu²⁺)(Ge¹⁻)₂, since the europium atoms are divalent and each germanium atom receives one additional valence electron. In that sense, EuGe₂ is expected to be a closed-shell compound with semiconducting behavior. However, temperature dependent resistivity measurements show EuGe₂ to be metallic. Subsequently, detailed crystallographic studies revealed the structure and the composition of EuGe₂ to be free of defects and impurities, which, along with the confirmed divalent oxidation state of the europium atoms by means of magnetic measurements, make EuGe₂ another example of a metallic Zintl phase. These results are in good agreement with the results of electronic structure calculations such as TB-LMTO-ASA (LDA) and FLAPW (GGA), which reveal non-zero DOS at the Fermi level.     

Rapid determination of gemcitabine in plasma and serum using reversed-phase HPLC

Gemcitabine (2'2'-difluorodeoxycytidine) is a pyrimidine analog used in the treatment of a variety of solid tumors. After intravenous (i.v.) administration, it is rapidly inactivated to 2'-deoxy-2',2'-difluorouridine (dFdU). A sensitive analytical method for the quantitation of gemcitabine is required for the assessment of alternative dosage and treatment schemes. A rapid and robust RP-HPLC assay for analysis of gemcitabine in human and animal plasma and serum was developed and validated using 2'-deoxyuridine (dU) and 5-fluoro-2'-deoxyuridine (5FdU) as internal standards. It is based on protein precipitation, the use of an Atlantis dC18 column of 100 mm length (inner diameter, 4.6 mm; particle size, 3 microm) and isocratic elution using a 10 mM phosphate buffer, pH 3.0, followed by isocratic elution with the same buffer containing 3% of ACN. For gemcitabine, RSD values for intraday and interday precision were < 4.4 and 5.3%, respectively, the LOQ was 20 ng/mL, and the assay was linear in the range of 0.020-20 microg/mL with an accuracy of > or =89%. The recovery for gemcitabine, dU and 5FdU was 86-98%. The assay was applied to determine gemcitabine levels in plasma samples of patients collected during and shortly after conventional infusion of 25-30 mg/kg body mass (levels: 2.0-18.9 microg/mL) and rats that received lower doses (1.5 mg/kg) via i.v., subcutaneous and oral drug administration (levels: 0.20-2.60 microg/mL). It could also be applied to estimate dFdU levels in human plasma.     

Admissibility of Unbounded Operators and Wellposedness of Linear Systems in Banach Spaces

We study linear systems, described by operators A, B, C for which the state space X is a Banach space.We suppose that − A generates a bounded analytic semigroup and give conditions for admissibility of B and C corresponding to those in G. Weiss’ conjecture. The crucial assumptions on A are boundedness of an H^∞-calculus or suitable square function estimates, allowing to use techniques recently developed by N. Kalton and L. Weis. For observation spaces Y or control spaces U that are not Hilbert spaces we are led to a notion of admissibility extending previous considerations by C. Le Merdy. We also obtain a characterisation of wellposedness for the full system. We give several examples for admissible operators including point observation and point control. At the end we study a heat equation in X = L^p(Ω), 1 < p < ∞, with boundary observation and control and prove its wellposedness for several function spaces Y and U on the boundary ∂Ω.     

Synthesis and Crystal Structure of a new O,N Lithium Coordination Polymer

The reaction of 4‐Amino‐6‐methyl‐1, 2, 4‐triazine‐3(2H)‐thione‐5‐one (HAMTTO) with n‐butyl lithium in dimethoxyethane (DME) gives the complex [Li(DME)(AMTTO)] ( 1 ). 1 was characterized by elemental analysis, IR‐ and mass‐spectrometry and an X‐ray structure analysis [space group P2₁/n, Z = 4, lattice dimensions at —80 °C: a = 867.6(1), b = 1721.5(2), c = 931.8(1) pm, β = 112.81(1)°, R₁ = 0.0315. The complex is a coordination polymer along [001] with a zig‐zag arrangement.