Inst. Chemie

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Fragmentable Heterogeneous Cocatalysts for the Metallocene-Catalyzed Polymerization of Olefins, I. Surface Modification of Silica and Characterization of the Resulting Carriers

Schumann, Herbert ; Widmaier, Ralf ; Lange, Katharina C. H. ; Wassermann, Birgit C. (2005)

Surface modification of pre-dried spherical silica nano-particles with diameters of 235 nm and 10 to 20 nm and of commercially available non-spherical silica materials using various aminoalkyltrialkoxysilanes and α-ω-bis(alkoxysilyl)organyls (organyl = alkanediyl, aminoalkanediyl, polyether, polysiloxane) has been performed in suspension in solvents with water. The quantity of water has a domin...

Fragmentable Heterogeneous Cocatalysts for the Metallocene-Catalyzed Polymerization of Olefins, II [1]. Preparation, Characterization and Testing of the Cocatalysts and Microscopic Evaluation of the Polyethylene

Schumann, Herbert ; Widmaier, Ralf ; Lange, Katharina C. H. ; Wassermann, Birgit C. (2005)

Surface modified silica were reacted with different aluminiumalkyls AlR2R’ (R = Me, Et, i-Bu, R’ = H, Me, Et, i-Bu), oligomeric methylaluminoxane (MAO) and combinations of both, to yield heterogeneous cocatalysts. These cocatalyts were employed to polymerize ethylene using zirconocene dichloride as the catalyst. The polymerization activity profiles have been recorded and compared with the infor...

2,5-Dimethyl-3,6-bis[(2,6-diisopropylphenylimino)methyl]- and 2,6-Bis[(2,6-diisopropylphenylimino)methyl]pyrazine: Two New Chelating Ligands for Transition Metal Complexes

Schumann, Herbert ; Luo, He-Kuan (2005)

The reaction of tetramethylpyrazine with SeO2 yields 2,5-dimethylpyrazine-3,6-dicarboxaldehyde (1) from which the 2,5-dimethyl-3,6-bis[(2,6-diisopropylphenylimino)methyl]pyrazine (2) was synthesized by treatment with 2 equivalents of 2,6-diisopropylaniline. 2,6-Dimethylpyrazine reacts with benzaldehyde to give 2,6-distyrylpyrazine (3). Ozonolysis of 3, followed by treatment with Na2SO3 and 2,6-...

Di-, Hexa- und Deca-substituierte Decaphenylferrocene

Schumann, Herbert ; Sühring, Klaudia (2005)

5-Bromo-1,2,3,4-tetraphenyl-5-p-tolyl-1,3-cyclopentadiene (1a), 5-Bromo-1,4-di-phenyl-2,3,5- tri-p-tolyl-1,3-cyclopentadiene (1b), 5-Bromo-1,2,3,4,5-penta-p-tolyl-1,3-cyclopentadiene (1c), 5- Bromo-1,2,3,4-tetraphenyl-5-p-bromophenyl-1,3-cyclopentadiene (1d), and 5-Bromo-1,2,3,4-tetraphenyl- 5-p-anisyl-1,3-cyclopentadiene (1e) react with ironpentacarbonyl in m-xylene to yield the corresponding ...

Metallkomplexe von 2,2’-Dipyridyldisulfid mit Quecksilber(II)-, Cadmium(II)- und Zink(II)-Halogeniden und mit Cadmium(II)- Trifluormethansulfonat

Pickardt, Joachim ; Chrzanowski, Lars von ; Steudel, Ralf ; Borowski, Marina ; Beck, Sebastian (2005)

Crystals of diiodo-2,2’-dipyridyldisulfide mercury(II) [HgI2(C5H4N)2S2], dichloro-2,2’-dipyridyldisulfide zinc(II) [ZnCl2(C5H4N)2S2], dibromo-2,2’-dipyridyldisulfide cadmium(II) [CdBr2 (C5H4N)2S2], diiodo-2,2’-dipyridyldisulfide cadmium(II) [CdI2(C5H4N)2S2], and diaquo 2,2’-dipyridyldisulfide cadmium(II) trifluoromethanesulfonate [Cd(H2O)2(C5H4N)2S2](CF3SO3)2, were obtained by evaporation of so...

Studies on the Thermolysis of Ether-Stabilized Lu(CH2SiMe3)3. Molecular Structure of Lu(CH2SiMe3)3(THF)(diglyme)

Rufanov, Konstantin A. ; Freckmann, Dominique M. M. ; Kroth, Heinz-Jürgen ; Schutte, Stefan ; Schumann, Herbert (2005)

Lu(CH2SiMe3)3(THF)2 (2) decomposes slowly at room temperature with formation of Me4Si. In order to understand the mechanism of this elimination process, Lu(CH2SiMe3)3([D8]-THF)2 (1), Lu(CH2SiMe3)3(THF)(DME) (3), and Lu(CH2SiMe3)3(THF)(diglyme) (4) were prepared. The results of 1H NMR spectroscopic studies of the decomposition in solution exclude an α- as well as a β -H elimination mechanism and...

Deca(4-methylbenzyl)ferrocen und -stannocen

Schumann, Herbert ; Sühring, Klaudia ; Weimann, Roman ; Hummert, Markus (2005)

Cyclopentadiene reacts with five equivalents of 4-methylbenzylalcohol (1:5,6 mole ratio) and sodium yielding penta(4-methylbenzyl)cyclopenta-2,4-diene (1), which upon treatment with butyl lithium affords the lithium salt [(4-MeC6H4CH2)5C5]Li (2). The reactions of 2 with FeCl2 and SnCl2 result in the formation of deca(4-methylbenzyl)ferrocene (3) and deca(4-methylbenzyl)stannocene (4), respectiv...

Introduction of Substituents on the 2-Oxo-piperazine Skeleton by [3+2] Cycloaddition and Subsequent Transformation

Wierschem, Frank ; Rück-Braun, Karola (2006)

The 3,4-substituted 2-oxo-piperazines 5 - 9 are obtained by [3+2] cycloaddition from nitrone 1 and a variety of alkenes. Subsequent functionalization of the bicyclic adducts involves reductive N-O bond cleavage. A route towards libraries of immobilized 1,3-aminoalcohols with a 3,4-substituted 2-oxo-piperazine scaffold is briefly discussed for adducts derived from N-substituted maleic imides

Structure-Activity Relationships of Synthetic Analogs of Jasmonic Acid and Coronatine on Induction of Benzophenanthridine Alkaloid Accumulation in Eschscholzia californica Cell Cultures

Haider, Georg ; Schrader, Thomas von ; Füßlein, Martin ; Blechert, Siegfried ; Kutchan, Toni M. (2000)

A facile test system based on the accumulation of benzo[c]phenanthridine alkaloids in Eschscholzia californica cell suspension culture (an indicator of defense gene activation) has been used to analyze a series of synthetic compounds for elicitor-like activity. Of the 200 jasmonic acid and coronatine analogs tested with this system, representative results obtained with 49 of them are presented ...

Fluorite-Type Solid Solutions in the System Y-Ta-O-N: A Nitrogen-Rich Analogue to Yttria-Stabilized Zirconia (YSZ)

Schilling, H. ; Wolff, H. ; Dronskowski, Richard ; Lerch, Martin (2006)

Fluorite-type phases in the system Y-Ta-O-N have been prepared by ammonolysis of Y-Ta-O precursors. X-ray powder patterns show unusual asymmetrical reflection profiles explained by DFT and MD methods. The anion vacancy concentration of some of these oxynitrides is similar to that of yttria-doped zirconia, commercially used as solid electrolyte in fuel cells. Hence, these compounds are interesti...

Untersuchungen Über Iodomercurate: Kristallstrukturen Von Bis-Tetramethylammonium-Tetraiodomercurat(Ii), Tetramethylammoniumpentaiododimercurat(Ii) Und Bis[Di(12-Krone-4)Lithium]-Decaiodotetramercurat(Ii)

Pickardt, Joachim ; Wiese, Sven ; Borowski, Marina (2006)

Crystals of [Me4N]2[HgI4] (1) and [Me4N][Hg2I5] (2), were obtained from solutions of stoichiometric amounts of HgI2 and Me4NI in EtOH or acetone, resp., while crystals of [Li(12-crown- 4)2]2[Hg4I10] (3) formed upon interdiffusion of methanolic solutions of HgI2, LiI and of the auxiliary ligand. The crystal structures of the compounds were determined. The [Hg2I5]− ion in (2) has a polymeric shee...

New Synthetic Routes for 1-Benzyl-1,4,7,10-tetraazacyclododecane and 1,4,7,10-Tetraazacyclododecane-1-acetic Acid Ethyl Ester, Important Starting Materials for Metal-coded DOTA-Based Affinity Tags

Kohl, Stephan W. ; Kuse, Katharina ; Hummert, Markus ; Schumann, Herbert ; Mügge, Clemens ; Janek, Katharina ; Weißhoff, Hardy (2007)

Two improved routes to synthesize 1-benzyl-1,4,7,10-tetraazacyclododecane (6) and 1,4,7,10- tetraazacyclododecane-1-acetic acid ethyl ester (11) are described as well as the synthesis of 1-{2-[4-(maleimido-N-propylacetamidobutyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane- 4,7,10-triacetic acid (17) and its Y, Ho, Tm, and Lu complexes. The 1H and 13C NMR spectra of the new compounds as we...

Carbamoyl Derivatives of a Pyridine-Based Tetraamine

Bilakhiya, Anvarhusen K. ; Heinemann, Frank W. ; Grohmann, Andreas (2007)

The reaction of four equivalents of phenyl or tert-butyl isocyanate with the pyridine-derived tetraamine 2,6-C3H3N[CMe(CH2NH2)2]2 in toluene gives high yields of the quadruply ureido substituted products 2,6-C5H3N[CMe(CH2R)2]2 [R = -NH(CO)NHPh and -NH(CO)NHtBu]. Full spectroscopic data for both compounds are given. A single crystal X-ray structure determination of the phenyl derivative reveals ...

Organometallic Compounds of the Lanthanides 182 [1]. Calcium and Neodymium Complexes Containing the dpp-BIAN Ligand System: Synthesis and Molecular Structure of [(dpp-BIAN)CaI(THF)2]2 and [(dpp-BIAN)NdCl(THF)2]2

Schumann, Herbert ; Hummert, Markus ; Lukoyanov, Anton N. ; Chudakova, Valentina A. ; Fedushkin, Igor L. (2007)

Oxydation of (dpp-BIAN)Ca(THF)4 with 0.5 equiv. of I2 in THF yields [(dpp-BIAN)CaI(THF)2]2 (1). A corresponding neodymium compound [(dpp-BIAN)NdCl(THF)2]2 (2) has been obtained by reaction of (dpp-BIAN)Na2 with NdCl3 in THF. The X-ray single crystal structure analyses show 1 and 2 to be isostructural dimers containing octahedrally coordinated metal atoms bridged by the respective halides. The c...

Der erste verbrückte, bifunktionelle Cyclopentadienyl-Imidazolyliden- Ligand und Komplexe mit Titan und Zirconium

Müller, Jörn ; Piotrowski, Ingo ; Chrzanowski, Lars von (2007)

Starting from imidazole, 1-[2-(cyclopenta-2,4-dienyl)ethyl]-3-methylimidazolium iodide (3) was obtained as a mixture of isomers by a simple three-step synthesis. The reaction of 3 with Ti(NEt2)4 or Zr(NEt2)4 by double deprotonation of the imidazolium salt led to the isomerically pure cationic complexes [{η5-C5H4-(CH2)2-NHC}M(NEt2)2]+I− (NHC = N-heterocyclic carbene) 4a (M = Ti) and 4b (M = Zr),...

Funktion, Modifikation und Anwendung von O2-toleranten, NAD(P)+-reduzierenden [NiFe]-Hydrogenasen

Preissler, Janina (2018)

Lösliche, NAD(P)+-abhängige [NiFe]-Hydrogenasen („Soluble Hydrogenase“, SH) katalysieren die reversible Spaltung von H2 in jeweils zwei Elektronen und Protonen sowie die damit gekoppelte Reduktion des Pyridinnukleotid-Kofaktors. Die beiden Reaktionen erfolgen in zwei unterschiedlichen Modulen, dem Hydrogenasemodul HoxHY, das das H2-spaltende aktive [NiFe]-Zentrum trägt, und dem flavinhaltigen N...

New Caffeic Acid Esters from Plazia daphnoides

Hoeneisen, Maritza ; Alarcón, Julio ; Aqueveque, Pedro ; Bittner, Magalis ; Becerra, Jose ; Silva, Mario ; Jakupovic, Jasmin (2003)

Two new 3,4 dihydroxycinnamic acid esters have been isolated from Plazia daphnoides. The structures were elucidated by NMR spectroscopy.

Naphthoquinone Derivatives and Lignans from the Paraguayan Crude Drug “Tayï Pytá” (Tabebuia heptaphylla, Bignoniaceae)

Schmeda-Hirschmann, Guillermo ; Papastergiou, Fani (2003)

The Paraguayan crude drug “tayï pytá” is used to treat cancer, wounds and inflammation. It consist of the bark and trunkwood of Tabebuia heptaphylla (Bignoniaceae). A phytochemical study of the crude drug gave, in addition to previously described naphthoquinones and the known lignans cycloolivil and secoisolariciresinol, three new lapachenol (lapachonone)-, two naphthofuran-, a chromone and a n...

Electron Release and Proton Acceptance Reactions of (dpp-BIAN)Mg(THF)3

Fedushkin, Igor L. ; Chudakova, Valentina A. ; Hummert, Markus ; Schumann, Herbert (2008)

(dpp-BIAN)Mg(THF)3 (1) (dpp-BIAN = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) and (PhCOO)2 react with splitting of the peroxide bridge and formation of the dimeric magnesium benzoate [(dpp-BIAN)MgOCOPh(THF)]2 (2). The reaction of 1 with PhCOOH yields the dimeric magnesium benzoate [(dpp-BIAN)(H)MgOCOPh(THF)]2 (3), whereas 1 and furanyl-2-carboxylic acid react with liberation of hydrogen...

Modeling of variant copies of subunit D1 in the structure of photosystem II from Thermosynechococcus elongatus

Loll, Bernhard ; Broser, Matthias ; Kós, Peter B. ; Kern, Jan ; Biesiadka, Jacek ; Vass, Imre ; Saenger, Wolfram ; Zouni, Athina (2008)

In the cyanobacterium Thermosynechococcus elongatus BP-1, living in hot springs, the light environment directly regulates expression of genes that encode key components of the photosynthetic multi-subunit protein-pigment complex photosystem II (PSII). Light is not only essential as an energy source to power photosynthesis, but leads to formation of aggressive radicals which induce severe damage...