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4. Cationic methyl complexes of the rare-earth metals: an experimental and computational study on synthesis, structure, and reactivity

Author

Kramer, Mathias U., Robert, Dominique, Arndt, Stefan, Zeimentz, Peter M., Spaniot, Thomas P., Yahia, Ahmed, Maron, Laurent, Eisenstein, Odile, and Okuda, Jun

Subjects
Density functionals -- Usage, Methyl groups -- Chemical properties, Organometallic compounds -- Chemical properties, Organometallic compounds -- Structure, Rare earth metals -- Chemical properties, Chemistry
Published
2008

5. Yttrium Dihydride Cation [YH 2 (THF) 2 ] + n : Aggregate Formation and Reaction with (NNNN)-Type Macrocycles

Author

Arndt, Stefan, Kramer, Mathias, Fegler, Waldemar, Nakajima, Yumiko, del Rosal, Iker, Poteau, Romuald, Spaniol, Thomas, Maron, Laurent, Okuda, Jun, Institute of Inorganic Chemistry [Aachen], Rheinisch-Westfälische Technische Hochschule Aachen (RWTH), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Institute of Inorganic Chemistry [Aachen] (IAC RWTH), Rheinisch-Westfälische Technische Hochschule Aachen University (RWTH), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph]
Abstract

International audience; Monocationic bis(hydrocarbyl)yttrium complexes [YR2(THF)2][A] (R = CH2SiMe3, CH2C6H4-o-NMe2; A = weakly coordinating anion) underwent hydrogenolysis using dihydrogen or phenylsilane to give a mixture of polynuclear solvent-stabilized dihydride cations [YH2(THF)2]n[A]n. The mixture composition as well as the nuclearity n depended on the starting material, solvent, and reaction conditions. NMR spectroscopic data in solution and X-ray diffraction data suggested that the main product was tetranuclear, although conclusive structural data were not obtained. DFT calculations supported a closo-type tetrahedral [YH2(THF)2]44+ core. The hydridic character of these cations was revealed by their reaction with benzophenone to give the bis(diphenylmethoxy) cation [Y(OCHPh2)2(THF)4][AlR4]. The reaction of this cluster with the (NNNN)-type macrocycle Me4TACD under dihydrogen gave the dinuclear tetrahydride dication with quadruply bridging hydride ligands, [Y2(μ-H)4(Me4TACD)2][A]2, analogous to the previously characterized lutetium derivative. NH-acidic (Me3TACD)H gave the dinuclear dihydride dication [Y2(μ-H)2(Me3TACD)2(THF)2][A]2.

Published
2015

8. Rote Liste und Artenverzeichnis der Laufkäfer Baden-Württembergs : (Coleoptera: Carabidae)

Author

Trautner, Jürgen, Bräunicke, Michael, Kiechle, Josef, Kramer, Mathias, Rietze, Jörg, Schanowski, Arno, and Wolf-Schwenninger, Karin

Subjects
ddc:590
Abstract

Vor über 10 Jahren wurde die erste Fassung einer Roten Liste und Checkliste gefährdeter Laufkäferarten Baden-Württembergs publiziert (TRAUTNER 1992), eine zweite Fassung, getrennt in Rote Liste und Artenverzeichnis, folgte 1996 (TRAUTNER 1996a, TRAUTNER & BRÄUNICKE 1996). Seit dieser Zeit hat sich der Kenntnisstand zu Verbreitung, Habitatansprüchen und Gefährdungssituation der Laufkäferarten in Baden-Württemberg wesentlich verbessert. Eine Neufassung der Roten Liste als wichtiges Instrument für die Praxis in Naturschutz und Landschaftsplanung war daher dringend erforderlich.

Published
2009

14. Molecular Rare-Earth-Metal Hydrides in Non-Cyclopentadienyl Environments.

Author

Fegler, Waldemar, Kramer, Mathias, Okuda, Jun, and Venugopal, Ajay

Subjects
*HYDRIDES, *RARE earth metal catalysts, *ADDITION polymerization, *CHEMICAL bonds, *LIGAND exchange reactions, *HYDROGENOLYSIS, *MOLECULAR imprinting
Abstract

Molecular hydrides of the rare-earth metals play an important role as homogeneous catalysts and as counterparts of solid-state interstitial hydrides. Structurally well-characterized non-metallocene-type hydride complexes allow the study of elementary reactions that occur at rare-earth-metal centers and of catalytic reactions involving bonds between rare-earth metals and hydrides. In addition to neutral hydrides, cationic derivatives have now become available. [ABSTRACT FROM AUTHOR]

Published
2015
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15. Molekulare Seltenerdmetallhydride in Nicht-Cyclopentadienyl-Umgebungen.

Author

Fegler, Waldemar, Venugopal, Ajay, Kramer, Mathias, and Okuda, Jun

Abstract

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2015
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17. C–C coupling reaction of pyridine derivatives at the dimethyl rare-earth metal cation [YMe2(THF)5]+: A DFT investigation

Author

Yahia, Ahmed, Kramer, Mathias U., Okuda, Jun, and Maron, Laurent

Subjects
*RARE earth metals, *METAL ions, *DENSITY functionals, *PYRIDINE derivatives, *ELIMINATION reactions, *COMPLEX compounds, *REACTION mechanisms (Chemistry)
Abstract

Abstract: Applying DFT methods, the reductive elimination reaction of bis(pyridyl) rare-earth metal cation [Ln(η 2-C,N-pyridyl)2(THF)3]+ (Ln = Y, La) was studied. The effect of both electron-donating and electron-withdrawing substituents in the para-position of the pyridine ring was considered. An alternative mechanism for the C–C coupling reaction between pyridine derivatives (pyridine, DMAP and 4-trifluoromethyl-pyridine) and [LnMe2(THF)5]+ (Ln = Y or La) is suggested. The reaction involves a single electron reductive C–C coupling to form of Ln(II) complexes with a bipyridine radical anion. [ABSTRACT FROM AUTHOR]

Published
2010
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19. [Risk assessment of bluetongue disease incursion into Germany using geographic information system (GIS)].

Author

Koslowsky S, Staubach C, Kramer M, and Wieler LH

Subjects
Animals, Bluetongue transmission, Ceratopogonidae physiology, Germany epidemiology, Insect Vectors physiology, Population Density, Population Dynamics, Risk Factors, Ruminants, Seasons, Sheep, Bluetongue epidemiology, Ceratopogonidae virology, Geographic Information Systems, Insect Vectors virology, Risk Assessment methods
Abstract

Using a geographic information system (GIS), by analysis of the relationship between the spatial distribution of cattle density and the risk factors temperature, altitude and rainfall, we defined geographical habitats enabling optimal development and competence of Culicoides spp. to transmit Bluetongue-Virus (BTV): Risk zones (low, high, highest risk) were identified mainly in Baden-Württemberg, Hessen and Rheinland-Pfalz if persistently infected ruminants are imported into these zones in summer (June to August mainly), based on the current climatic conditions, BTD outbreaks are considered a real possibility. Overwintering of the virus seems unlikely. However, global warming will lead to a steady increase of the size of the risk zones. In addition, the possibility of primary outbreaks increases. The reason for this is not only the expected northern shift of Culicoides imicola, but in addition an increasing vector competence of domestic Culicoides species. We therefore recommend the storage of vaccines as well as conducting ecological studies analysing the presence of Culicoides vectors. Using the data from these studies, it will be possible to produce updated quantitative risk assessment via GIS.

Published
2004

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