Stereospecific functionalisations of iron carbonyl complexes of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene. Crystal and molecular structure of (C12H12)Fe2(CO)6

When the reaction between an excess of Fe₂(CO)₉ and the pentaene 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene(I) is carried out in hexane/methanol the endo,exo-bis(tetrahaptotricarbonyliron) isomer (C₁₂H₁₂)Fe₂(CO)₆(IIa)is the major product. The structure of this complex has been determined by X-ray diffraction.The asymmetric positions of the two Fe(CO)₃ groups with respect to the roof-shaped organic skeleton was used to induce either stereo-specific functionalisation of the uncoordianted endocyclic CC double bond or stereo-and regiospecific functionalisation of one of the two coordinated s-cis-butadiene groups of the pentaene. Thus, hydroboration/oxidation of Ila gave the endo-exo-bis(tetrahaptotricarbonyliron)isomer of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]octane-2-ol (IV). cis deuteration of the exocyclic double bond was achieved by treating IIa with D₂/PtO₂ in n-hexane.Protonation of IIa by HCl/AlCl₃/CH₂Cl₂ to give the η⁴-diene : η²-ene : η³-dienyl cationic complex Va, followed by quenching of Va with NaHCO₃/CH₃OH, resulted in a 1,4-addition of methanol to one coordinated s-cis-butadiene system. In contrast, quenching with NaOCH₃/CH₃OH resulted in the corresponding 1,2-addition of methanol. This gave the η⁴-1,3-diene : η⁴-1,4-diene complex VIIIa in which, suprisingly, one Fe(CO)₃ group is coordinated to two CC double bonds in gauche positions with respect to each other.     

High performance analytical characterization of refractory metals

It is first shown what effects trace impurities generally exert on metal properties and why trace analysis is essential to modern applications of refractory metals in today's high technology. The effect of trace impurities in metals on complex systems like microelectronic components is also discussed.It is then shown, what principal analytical requirements are mandatory for trace characterization of refractory metals at levels of rising purity (4 N to 6 N). A survey of analytical methods for trace and ultratrace characterization of refractory metals is given including the following methods: flame and graphite furnace atomic absorption spectrometry, ICP and DCP-atomic emission spectrometry, X-ray fluorescence spectrometry, activation analysis, mass spectrometric methods, especially SIMS and GDMS.     

Manganoan rockbridgeite Fe4.32Mn0.62Zn0.06(PO4)3(OH)5: structure analysis and 57Fe Mössbauer spectroscopy

The structure of the basic iron phosphate rockbridgeite [iron manganese zinc tris­(phosphate) penta­hydroxide] was reinvestigated with special emphasis on the cation distribution deduced from new X‐ray and ⁵⁷Fe Mössbauer data. Rockbridgeite is orthorhombic, space group Cmcm, and shows three different Fe sites, one with symmetry, another with m symmetry and the third in a general position. One phosphate group has the P atom on a site with m symmetry, while the other has the P atom at a site with mm symmetry. Two Fe sites are fully occupied by ferric iron, while Mn³⁺ and Fe²⁺ are situated at a third, principally Fe, site. Structural data, bond‐valence sums and polyhedral distortion parameters suggest a new inter­pretation of the rockbridgeite ⁵⁷Fe Mössbauer spectrum.     

On averaging sets

For any set ={f ₁,f ₂,...,f _s} ofC ³-functions on the interval [–1, 1], and for any weight functionw(x) satisfyingL ₁w(x)L ₂(1–|x|)(L ₁,L ₂>0, 0) and , we give a constructive proof for the existence of quadrature formulas of the type

1, 4, 5, 6-Tetrahydro-ν-tetrazin-Derivate

1, 4, 5, 6-Tetrahydro-ν-tetrazin-Derivate The title compounds 2 and 13 are readily available from α-lithiated N-alkyl-nitrosoamines 1 (see Tables 1 and 2) which decompose at ? 73° to yield the N-oxides 2. The ESR. spectra of two derivatives 1 are recorded (Fig. 1), and tentative mechanisms are proposed for the head to head dimerizations ( la- 3- 4- 5- 2a and Scheme 1). Coupling of lithionitrosoamines with iodine (-6) and alternative decomposition routes of representatives of this class of organometallics with special substitution [equations (2)-(5)] are reported. The structures of the tetrazines are established by spectroscopic data [ESCA] (Fig. 2), IR., UV., ¹H- (cf. Fig. 9) and ¹³C-NMR., PE. (Scheme 2), by an X-ray analysis of 2a (Fig. 4-8 and Table 3), and by the chemical reactions. The crystal structure of 2a is a twisted boat with non planar terminal nitrogen atoms which reflects the electron repulsion in the 4-atom-6-electron N? N?N?N-system. Comparisons are made with 2-tetrazenes, the open chain analogues of 13 , wherever possible. Raney-Ni reductions of 2 or 13 gives diamines 14 to which is assigned the d, l-configuration through the ¹H-NMR. spectra of the aminals 7 and 15 . Neither the oxides 2 nor the tetrazines 13 undergo cycloaddition reactions [equation (6) and Section 4]. Compound 2a is dimerized to the bis (nitrosoamino)-2-tetrazene 18 by treatment with acid, Zn^II, Cu^I or iodomethane. 2a is oxidized at nitrogen to the ethylene diamine derivative 6a (through 20 , with H₂O₂), or at the CH₂-groups of the ring to give oxo-N-oxide 21 (with MnO₂ or the ring contracted oxo-tetrazoline-N-oxide 22 (with KMnO₄). Pyrolysis or photolysis of the dimethyl tetrahydrotetrazine 13a furnishes the trimer 26 of N-methylimine, but no diazetidine 27 . Silver and mercury complexes 29 are obtained from 13a , while Cr(CO)₅. THF does not furnish a complex as with azocompounds, but rather replaces N₂ in 13a by CO (→ 28). Oxidation with permanganate converts 13a into the oxalic acid derivative 30 with unchanged tetrazine structure.     

Analysis of the quorum-sensing regulon of the opportunistic pathogen Burkholderia cepacia H111 by proteomics

Burkholderia cepacia H111, an important pathogen for persons suffering from cystic fibrosis, employs a quorum-sensing (QS) system, cep, to control expression of virulence factors as well as the formation of biofilms. The QS system is thought to ensure that pathogenic traits are only expressed when the bacterial population density is high enough to overwhelm the host before it is able to mount an efficient response. In this study, we compared the protein pattern of the intracellular, extracellular, and surface protein fractions of an AHL-deficient cepI mutant with the one of the parent strain H111 by means of two-dimensional gel electrophoresis (2-DE). Our analysis showed that 55 proteins out of 985 detected spots were differentially expressed; these are expected to represent QS-controlled gene products. Addition of the respective signal molecules to the growth medium of the cep mutant fully restored the wild-type protein expression profile. In total about 5% of the B. cepacia proteome was downregulated and 1% upregulated in the cepI mutant, indicating that quorum sensing represents a global regulatory system. Nineteen proteins were identified with high confidence by N-terminal sequence analysis.     

Adsorption of a diverse set of organic vapors on quartz, CaCO3, and alpha-Al2O3 at different relative humidities

Adsorption constants of a diverse set of 50 organic vapors have been measured on quartz (SiO(2)), CaCO(3), and alpha-Al(2)O(3) at different relative humidities at 15 degrees C. For nonpolar compounds we found an exponential decrease of the adsorption constants on a given mineral between 40 and 97% relative humidity. Extrapolated to 100% relative humidity, the adsorption constants of nonpolar compounds on the different minerals coincide and agree with those measured on a bulk water surface. The adsorption constants of polar compounds also decrease with increasing humidity up to 90%, but between 90% and 100% they increase again. We speculate that this effect is due to a change in the orientation of the water molecules that form the surface at which the organic vapors adsorb at this high humidity. The compound variability in the adsorption constants of all compounds on a given surface at a given relative humidity could be described rather well with a linear free energy relationship using Abraham's solvation parameters for the van der Waals and electron-donor/acceptor properties of the compounds. The remaining deviation between fitted and experimental data was found to be systematic, which indicated that an optimized parameter set for the used compounds could still considerably improve the fit.     

Deep hydration of an Li7–3xLa3Zr2MIIIxO12 solid-state electrolyte material: a case study on Al- and Ga-stabilized LLZO

Single crystals of an Li-stuffed, Al- and Ga-stabilized garnet-type solid-state electrolyte material, Li₇La₃Zr₂O₁₂ (LLZO), have been analysed using single-crystal X-ray diffraction to determine the pristine structural state immediately after synthesis via ceramic sintering techniques. Hydrothermal treatment at 150 °C for 28 d induces a phase transition in the Al-stabilized compound from the commonly observed cubic Iad structure to the acentric I3d subtype. Li^I ions at the interstitial octahedrally (4 + 2-fold) coordinated 48e site are most easily extracted and Al^III ions order onto the tetrahedral 12a site. Deep hydration induces a distinct depletion of Li^I at this site, while the second tetrahedral site, 12b, suffers only minor Li^I loss. Charge balance is maintained by the incorporation of H^I, which is bonded to an O atom. Hydration of Ga-stabilized LLZO induces similar effects, with complete depletion of Li^I at the 48e site. The Li^I/H^I exchange not only leads to a distinct increase in the unit-cell size, but also alters some bonding topology, which is discussed here.     

Kobalt(III)-Komplexe von N,N, N′, N′-Tetrakis-(β-aminoäthyl)-äthylendiamin (= «penten»)

Several salts containing the cation Co(penten)³⁺, in which the hexamin «penten» (formula: page 625) acts as a sexadentate ligand, have been synthesized and characterized. Its optical antipodes have been separated in some of the salts (Fig. 4), and the rate of racemization studied. In strongly alkaline solution one of the 5 chelate rings slowly opens and Co(penten)OH²⁺ is produced (Fig. 1), to which a first proton can be attached at the terminal NH₂-group (→ Co(Hpenten)OH³⁺), and a second which converts the hydroxo-complex into the aquo-complex (→ Co(Hpenten)OH⁴⁺). The equilibria between Co(penten)³⁺, Co(penten)OH²⁺, Co(Hpenten)OH³⁺ and Co-(Hpenten)OH₂⁴⁺ have been elucidated, and the kinetics of the ring opening and ring closing reactions have been studied. Ring opening and ring closure take place with retention of configuration. It proved impossible to open two of the chelate rings of Co(penten)³⁺. Cristalline salts with cations of the general formula Co(penten)X³?λ or Co (Hpeten)X^4?λ, with Xλ? ? OH?, H₂O, F?, Cl?, Br?, J?, SCN?, NO₂,? and CO₃²?, have been obtained and characterized (Fig. 1, 2, 7 and Table 1).