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  • Inorganic Chemistry  (9,173)
  • LUNAR AND PLANETARY EXPLORATION  (3,305)
  • Biology
  • Electron microscopy
  • 2000-2004  (7)
  • 1995-1999  (1,953)
  • 1980-1984  (6,887)
  • 1930-1934
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  • 1
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    Unknown
    Toward self-organization and complex matter (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-03-30
    Description: Beyond molecular chemistry based on the covalent bond, supramolecular chemistry aims at developing highly complex chemical systems from components interacting through noncovalent intermolecular forces. Over the past quarter century, supramolecular chemistry has grown into a major field and has fueled numerous developments at the interfaces with biology and physics. Some of the conceptual advances and future challenges are profiled here.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lehn, Jean-Marie -- New York, N.Y. -- Science. 2002 Mar 29;295(5564):2400-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Science et d'Ingenierie Supramoleculaires (ISIS), Universite Louis Pasteur, 67000 Strasbourg, and College de France, 75005 Paris, France. lehn@chimie.u-strasbg.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11923524" target="_blank"〉PubMed〈/a〉
    Keywords: Biology ; Chemical Phenomena ; *Chemistry ; Chemistry, Physical ; Molecular Structure ; Nanotechnology ; Physical Phenomena ; Physicochemical Phenomena ; Physics ; *Polymers/chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
    Electronic Resource
    Electronic Resource
    Defect structure of the low temperature α-cristobalite phase and the cristobalite ⇆ tridymite transformation in (Si-Ge)O2 (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 386-397 
    Details
    ISSN: 1432-2021
    Keywords: Key words Cristobalite ; Tridymite ; Phase transformation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Using minimum exposure techniques, it is feasible to perform high resolution electron microscopy on the α-cristobalite phase of (Si0.9 Ge0.1)O2, which is extremely radiation sensitive. Such images reveal atomic scale information of twins and tridymite-like stacking faults on (1 1 1)β planes, as well as of domain boundaries resulting from the β→α transition. Polytype structures are formed in certain cases. Morphological features suggest that the phase transformation cristobalite → tridymite proceeds by means of a zonal dislocation mediated synchro-shear process on (1 1 1)β planes; the geometry of this process is analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002699900082
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  • 3
    Electronic Resource
    Electronic Resource
    The need for a shared database infrastructure: combining X-ray crystallography and electron microscopy (2000)
    Springer
    European biophysics journal 29 (2000), S. 457-462 
    Details
    ISSN: 1432-1017
    Keywords: Key words X-ray crystallography ; Electron microscopy ; Biological databases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Advances in structural biology are opening greater opportunities for understanding biological structures from the cellular to the atomic level. Particularly promising are the links that can be established between the information provided by electron microscopy and the atomic structures derived from X-ray crystallography and nuclear magnetic resonance spectroscopy. Combining such different kinds of structural data can result in novel biological information on the interaction of biomolecules in large supramolecular assemblies. As a consequence, the need to develop new databases in the field of structural biology that allow for an integrated access to data from all the experimental techniques is becoming critical. Pilot studies performed in recent years have already established a solid background as far as the basic information that an integrated macromolecular structure database should contain, as well as the basic principles for integration. These efforts started in the context of the BioImage project, and resulted in a first complete database prototype that provided a versatile platform for the linking of atomic models or X-ray diffraction data with electron microscopy information. Analysis of the requirements needed to combine data at different levels of resolution have resulted in sets of specifications that make possible the integration of all these different types in the context of a web environment. The case of a structural study linking electron microscopy and X-ray data, which is already contained within the BioImage data base and in the Protein Data Bank, is used here to illustrate the current approach, while a general discussion highlights the urgent need for integrated databases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490000089
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence for stable grain boundary melt films in experimentally deformed olivine-orthopyroxene rocks (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 480-494 
    Details
    ISSN: 1432-2021
    Keywords: Key words Olivine ; Grain boundary ; Partial melt ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The microstructure of olivine-olivine grain boundaries has been studied in experimentally deformed (1200–1227 °C, 300 MPa) partially molten olivine and olivine-orthopyroxene rocks. In-situ melting produced ∼1 vol% melt in all samples studied. Grain boundary analyses were carried out using a number of transmission electron microscopy techniques. The grain boundary chemistry in undeformed olivine-orthopyroxene starting material showed evidence for the presence of an intergranular phase along some, but not all, of the olivine-olivine boundaries. In the deformed samples, ultrathin Si-rich, Al- and Ca-bearing amorphous films have been observed along all investigated olivine-olivine grain boundaries. The chemistry of the grain boundaries, which is considered to be indicative for the presence of a thin film, was measured with energy-dispersive X-ray spectroscopy (EDX) and energy-filtering imaging. The amorphous nature of the films was confirmed with diffuse dark field imaging, Fresnel fringe imaging, and high-resolution electron microscopy. The films range in thickness from 0.6 to 3.0 nm, and EDX analyses show that the presence of Al and Ca is restricted to this ultrathin film along the grain boundaries. Because thin melt films have been observed in all the samples, they are thought to be stable features of the melt microstructure in deformed partially molten rocks. The transition from the occasional presence of films in the undeformed starting material to the general occurrence of the films in deformed materials suggests that deformation promotes the formation and distribution of the films. Alternatively, hot-pressing may be too short for films to develop along all grain boundaries. A difference in creep strength between the studied samples could not be attributed to grain boundary melt films, as these have been found in all deformed samples. However, a weakening effect of grain boundary melt films on olivine rheology could not be ruled out due to the lack of confirmed melt-film free experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690000090
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  • 5
    Electronic Resource
    Electronic Resource
    Biocompatibility of MPC: in vivo evaluation for clinical application (2000)
    Springer
    Journal of artificial organs 3 (2000), S. 39-46 
    Details
    ISSN: 1619-0904
    Keywords: Poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (MPC) ; In vivo biocompatibility ; Artificial endocrine pancreas ; Electron microscopy ; Glucose sensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Biocompatibility is important to assure a mild body reaction to an implanted device and its long-term stability and functionality. In diabetes research, subcutaneously implanted glucose monitoring systems need biocompatible surfaces for long-term application. The biocompatibility of poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (MPC), a material similar to the phospholipid layer of a cell membrane, was compared in vivo with the biocompatibility of polyurethane (PU), polyvinyl alcohol (PVA), and cuprophane (CUP). Needle-type glucose sensors and hollow-fiber probes used for microdialysis were coated with these four different biomaterials and implanted subcutaneously in 18 rats and 7 healthy volunteers. At set intervals, the implants and, in the case of the rats, also the surrounding tissue were removed and characterized by light and electron microscopy. MPC-coated sensors and hollow-fiber probes showed smooth and thin deposits in flat layers, whereas the surface deposits on PU- and PVA-coated sensors and those on CUP hollow-fiber probes appeared as rough, irregular, and dense attachments of aggregated cells and protein. This study confirmed results from earlier in vitro tests by showing the biocompatibility and reliability of MPC. Even though the amount of protein and cells attached to the MPC surface was not as low as expected from in vitro experiments, the biocompatibility and long-term stability of the implanted devices were superior to those of PU, PVA, and CUP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02479925
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of photic and thermal stress on distal and proximal rhabdomeres in the crayfish eye: why are the visual membranes of the 8th retinula cell more resilient than the others? (2000)
    Springer
    Protoplasma 210 (2000), S. 156-163 
    Details
    ISSN: 1615-6102
    Keywords: Electron microscopy ; Photoreceptor ; Visual membrane ; Photic radiation damage ; Retina ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Visual membranes of the crayfish eye either belong to the small, distally placed rhabdomere of retinula cell R8 or are part of the much more voluminous proximal rhabdom, made up of rhabdomeres belonging to cells R1–R7. Under various conditions of environmental stress (e.g., prolonged darkness, elevated temperature, bright light with and without a concomitant rise in temperature, flickering lights) the visual membranes of R8 prove far more resistant to structural damage than those of R1–R7. Membrane damage is known to occur when dormant lipoxygenases become activated, for example through heat. Since R8 is the only type of visual cell in the crayfish retina that does not contain grains of screening pigment, the view that screening-pigment granules could “aggravate” or even “trigger” membrane damage in times of stress is strengthened. Functionally, R8's strong resistance to physical damage when exposed to flickering lights points to a role of the distal rhabdom in the movement detection system of the crayfish eye.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276855
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  • 7
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    Molecular biology. Tackling biology with no holds barred, at 800 miles per hour (2000)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2000-08-05
    Description: Peter Schultz launched his academic career by exploring what made living organisms such powerful synthetic chemists. His work led him to conclude that the key to nature's success was its strategy of generating millions of possible chemical solutions to a problem and then screening for the ones that worked best. Now Schultz is applying this approach to working out the functions of the thousands of unknown genes being turned out by the world's genome projects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Service, R F -- New York, N.Y. -- Science. 2000 Jul 14;289(5477):233.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10917843" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibodies, Catalytic/chemistry ; *Bacteria/chemistry/genetics ; Biology ; Chemistry/*trends ; Chemistry, Pharmaceutical ; Combinatorial Chemistry Techniques ; Mice
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic properties of human liver and brain ferritin (1999)
    Springer
    European biophysics journal 28 (1999), S. 263-267 
    Details
    ISSN: 1432-1017
    Keywords: Key words Human liver ; Human brain ; Ferritin ; Electron microscopy ; Mössbauer spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Human brain (globus pallidus) and liver tissues were investigated by means of electron microscopy (EM), Mössbauer spectroscopy (MS) and SQUID magnetometry techniques. Based on MS measurements, the iron present was identified to be in the ferritin-like form (61–88%) and in the form of a low-spin iron species (the balance). Its overall concentration was estimated as 1.5(3) mg in the brain and 2.4(5) mg in the liver, per gram of lyophilized tissue. The average core diameter was determined by EM measurements to be equal to 7.5(1.3) nm for the liver and 3.3(5) nm for the brain. Magnetization measurements carried out between 5 and 300 K yielded an estimation of an average blocking temperature, KT BL, as equal to 6.7 K and 8.5 K for the liver and the brain, respectively. From the dependence of KT BL on the external magnetic field it was concluded that the ferritin-like cores in the studied samples can be regarded as non-interacting particles. Finally, the uniaxial magnetic anisotropy constant was determined to be 6×103 J/m3 for the liver and 4×104 J/m3 for the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050208
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  • 9
    Electronic Resource
    Electronic Resource
    Types, numbers and distribution of synapses on the dendritic tree of an identified visual interneuron in the brain of the locust (1999)
    Springer
    Cell & tissue research 296 (1999), S. 645-665 
    Details
    ISSN: 1432-0878
    Keywords: Key words Descending contralateral movement detector (DCMD) ; Identified neuron ; Vesicles ; Electron microscopy ; 3-D reconstruction ; Locust ; Schistocercagregaria (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The descending contralateral movement detector (DCMD), an identified descending interneuron in the brain of the locust Schistocerca gregaria has been investigated by using light and electron microscopy. We describe the fine structure, distribution and numbers of synapes that it receives from another identified brain neuron, the lobular giant movement detector (LGMD), and from unidentified neurons. The DCMD dendrites emerging from the integrative segment vary in form and number between individuals and sexes but always form a flattened dendritic domain. The arborizations and the integrative segment appear to be exclusively postsynaptic. Two types of synaptic contacts (Type 1 and 2) onto the DCMD can be discerned as having either round (Type 1) or pleiomorphic synaptic vesicles (Type 2) and by large (Type 1) or small (Type 2) subsynaptic appositions. Contact zones of Type 1 synapses are smaller than those of Type 2. LGMD-synapses are of Type 1 and occur intermingled with presynaptic sites of unidentified units. Some branches of the DCMD receiving input from unidentified units are devoid of contacting LGMD processes. Synapses of both types are randomly distributed over the DCMD integrative segment and at fibres with similar sizes.Type 1 synapses are much more frequent than Type 2 synapses and their number is negatively correlated with fibre diameter. For a whole DCMD dendritic arborization, a total of 8500 active zones of chemical synapses has been calculated, including a mininum of 2250 LGMD-synapses and about 1000 Type 2 synapses. The DCMD may thus receive a considerable amount of input from as yet unidentified neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051325
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  • 10
    Electronic Resource
    Electronic Resource
    Metaphase-specific cell death in meiotic spermatocytes in mice (1999)
    Springer
    Cell & tissue research 296 (1999), S. 359-369 
    Details
    ISSN: 1432-0878
    Keywords: Key words Apoptosis ; Electron microscopy ; Meiosis ; Spermatocytes ; Spermatogenesis ; Testis ; TUNEL ; Mouse (10 strains)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Apoptosis of male germ cells is a widespread but little-understood phenomenon in many animal species. The elucidation of its mechanisms could be useful in the understanding of male infertility. We have examined the distribution of dying cells with the terminal transferase-mediated nick-end labeling (TUNEL) method and by an electron-microscopic procedure in the testes of 10 mouse strains, viz., C57BL/10 (B10), SL/NiA (SL), C57BL/6 (B6), C3H/He (C3H), BALB/c (BALB), DBA2 (DBA), CBA/J (CBA), MRL/MpJ-+/+ (M+), MRL/MpJ-lpr/lpr (lpr), and wild-type NJL mice (Mus musculus musculus). In the testes of the B10, NJL, SL, B6, C3H, BALB, DBA, and CBA mice, very few TUNEL-positive cells are distributed in the seminiferous tubules, whereas in the testes of the M+ and lpr mice, many TUNEL-positive cells, which are restricted to stage XII seminiferous tubules, have been identified. The most important finding is that many metaphases of meiotic spermatocytes show a marked TUNEL-positive reaction. Some metaphases show apoptotic morphology electron-microscopically. These results suggest that the testes of MRL strains will provide a useful model for the study of the mechanism of metaphase-specific apoptosis in meiotic spermatocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051296
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  • 11
    Electronic Resource
    Electronic Resource
    Effect of high-level oxygen exposure on the peroxidase activity and the neuromelanin-like pigment content of the nerve net in the earthworm, Lumbricus terrestris (1999)
    Springer
    Cell & tissue research 295 (1999), S. 349-354 
    Details
    ISSN: 1432-0878
    Keywords: Key words Neuromelanin ; Neuron ; Peroxidase ; Oxygen metabolism ; High-definition light microscopy ; Electron microscopy ; Ultrastructure ; Cytochemistry ; Substantia nigra ; Lumbricusterrestris (Annelida)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Histochemical examination of 1-μm tissue sections from the dorsal nerve plexus of the earthworm, Lumbricus terrestris, reveals multiple brown intraneuronal granules. These granules contain material morphologically and histochemically consistent with neuromelanin. When viewed with transmission electron microscopy, these were seen as single membrane-enclosed biphasic granules with diameters of 370–730 nm. Exposure of L. terrestris to high-level environmental oxygen resulted in an increase in the number of neuromelanin-like pigment granules within the neurons of the circular muscle layer. As measured by ortho-phenylenediamine hydrochloride, the endogenous peroxidase activity of extracts from worms incubated in high-level environmental oxygen was 51% more than controls. The endogenous peroxidase activity was localized in situ with 3,3-diaminobenzidine (DAB) and was found to increase in and around the neuromelanin-like pigment-containing neurons within the circular muscle layer. These studies suggest that the nerve net of L. terrestris may serve as a model to study the role of neuromelanin production in oxidative stress and its relationship to endogenous peroxidases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051241
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  • 12
    Electronic Resource
    Electronic Resource
    Op/op mice defective in production of functional colony-stimulating factor-1 lack macrophages in muscularis externa of the small intestine (1999)
    Springer
    Cell & tissue research 295 (1999), S. 485-493 
    Details
    ISSN: 1432-0878
    Keywords: Key words Immunohistochemistry ; Electron microscopy ; Interstitial cells of Cajal ; F4/80 ; CSF-1 ; Kit-receptor ; Mouse (op/op)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The osteopetrotic (op/op) mutant mouse possesses an inactivating mutation in the colony-stimulating factor-1 (CSF-1) gene, which results in the absence of certain macrophages and in osteopetrosis, following a lack of osteoclasts. Studies of the op/op mouse indicate that CSF-1-dependent tissue macrophages may belong to a trophic and/or scavenger subpopulation, which through their effect on other cell types can significantly affect tissue functions, and that cells which are CSF-1 independent have antigen presentation and immunological functions.We have previously identified a cell system of regularly distributed macrophages in the muscularis externa of the small intestine and wanted to extend these studies to the op/op mouse.The present investigations with light- and electron-microscopic methods using fluorescent dextran, methylene blue and immunohistochemistry (F4/80, anti-kit receptor, anti-CD3, anti-CD45R/B220) show that macrophages are absent from the muscle layers, with only an occasional macrophage present in the subserosa. In the lamina propria and submucosa, macrophage numbers are reduced. In all other respects the muscularis externa appears normal, including normal organization and number of interstitial cells of Cajal. Control and op/op mice both lack cells expressing CD3 (T lymphocytes), CD45R/B220 (B lymphocytes) and mast cells in the muscularis externa. This leaves the muscularis externa macrophages as the most likely source of local cytokine production under such conditions as postoperative ileus and intussusception in infants, where the muscularis externa appears to be one target of cytokines. We conclude that the lack of macrophages, combined with the preservation of otherwise normal structure, will make the op/op mouse a valuable model by which to assess the functions and relative importance of the muscularis externa macrophages in relation to intestinal motility under normal and pathological conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051254
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  • 13
    Electronic Resource
    Electronic Resource
    Caveolin and its cellular and subcellular immunolocalisation in lung alveolar epithelium: implications for alveolar epithelial type I cell function (1999)
    Springer
    Cell & tissue research 295 (1999), S. 111-120 
    Details
    ISSN: 1432-0878
    Keywords: Key words Caveolin ; Caveolae ; Lung ; Alveolar epithelial type I cell ; Immunocytochemistry ; Electron microscopy ; Confocal laser scanning microscopy ; Rat (CD)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Caveolae are flask-shaped invaginations of the plasmalemma which pinch off to form discrete vesicles within the cell cytoplasm. Biochemically, caveolae may be distinguished by the presence of a protein, caveolin, that is the principal component of filaments constituting their striated cytoplasmic coat. Squamous alveolar epithelial type I (ATI) cells, comprising approximately 95% of the surface area of lung alveolar epithelium, possess numerous plasmalemmal invaginations and cytoplasmic vesicles ultrastructurally indicative of caveolae. However, an ultrastructural appearance does not universally imply the biochemical presence of caveolin. This immunocytochemical study has utilised a novel application of confocal laser scanning and electron microscopy unequivocally to localise caveolin-1 to ATI cells. Further, cytoplasmic vesicles and flask-shaped membrane invaginations in the ATI cell were morphologically identified whose membranes were decorated with anti-caveolin-1 immunogold label. Coexistent with this, however, in both ATI and capillary endothelial cells could be seen membrane invaginations morphologically characteristic of caveolae, but which lacked associated caveolin immunogold label. This could reflect a true biochemical heterogeneity in populations of morphologically similar plasmalemmal invaginations or an antigen threshold requirement for labelling. The cuboidal alveolar epithelial type II cell (ATII) also displayed specific label for caveolin-1 but with no ultrastructural evidence for the formation of caveolae. The biochemical association of caveolin with ATI cell vesicles has broad implications for the assignment and further study of ATI cell function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051217
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  • 14
    Electronic Resource
    Electronic Resource
    Phase and aggregation behaviour of double-chain cationic surfactants from the class of N-alkyl-N-alkyl′-N, N-dimethylammonium bromide surfactants (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 856-867 
    Details
    ISSN: 1435-1536
    Keywords: Key words Double chain surfactants ; Aggregates ; Phase diagrams ; Lamellar phases ; Electron microscopy ; SANS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We present the phase diagrams and the properties of newly synthesised double-chain cationic N-alkyl-N-alkyl′-N,N-dimethylammonium bromide surfactants [C x C y DMABr (x = 12, 14 and 16; y = 10, 11, 12, 14 and 16)]. All the systems studied form liquid-crystalline lamellar phases but with different morphologies: unilamellar vesicles at low surfactant concentrations, multilamellar vesicles and tubular aggregates for surfactant concentrations between 2 and 10 wt% and at even higher concentrations planar bilayers of surfactant molecules in the classical Lα phase. The phase diagrams were determined with macroscopic and microscopic methods (polarisation microscopy, freeze-fracture transmission electron microscopy, scanning electron microscopy and differential interference contrast microscopy). The properties of the surfactant solutions were determined with differential scanning calorimetry measurements for Krafft point determination and small-angle neutron scattering measurements for interlamellar spacing and bilayer thickness. Finally, conductivity and viscosity measurements for phase characterisation were carried out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050462
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  • 15
    Electronic Resource
    Electronic Resource
    Synthesis of colloids and films of Pr, Er and Yb with nonaqueous solvents (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 164-173 
    Details
    ISSN: 1435-1536
    Keywords: Keywords Nanostructures ; Thin films ; Vapor deposition ; Electron microscopy ; Optical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Colloidal dispersions of Yb, Er and Pr have been prepared by chemical liquid deposition. The metals were cocondensed at 77 K with 2-methoxyethanol and ethanol to produce solvated metal atoms. The particle size of the dispersions was determined by transmission electron microscopy to range from 52 to 1080 Å; the particles had spherical shapes. After solvent evaporation under vacuum, active solids and amorphous powder were deposited over Cu and Al metal. Dispersion stability, particle size, UV/Vis absorption and zeta potential were studied. The solids prepared by solvent evaporation were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The films prepared on Al were studied by scanning electron microscopy. The most stable colloid was obtained using 2-methoxyethanol: several concentrations were stable for several months and the zeta potential indicated that this colloid stability is mainly due to solvation effects. FTIR spectroscopy of the solids indicated solvent incorporation in the film. This observation was corroborated by thermal analysis. Information on the thermal stability of the films was obtained by TGA. The UV/Vis absorption spectrum was measured at several concentrations under different conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050381
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  • 16
    Electronic Resource
    Electronic Resource
    Morphological and physical characterization of the capsular layer of Vibrio cholerae O139 (1998)
    Springer
    Archives of microbiology 170 (1998), S. 339-344 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsV. cholerae O139 ; Lipopolysaccharide ; Electron microscopy ; Freeze-substitution technique ; Capsule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The morphological and physical characteristics of the capsule of Vibrio cholerae O139 were examined. An electron microscopic study using the freeze-substitution technique showed that all of the V. cholerae strains of the O139 serogroup examined have a very thin fibrous layer on the outside of the outer membrane. In contrast, the mutants of strain O139, strain MO10T4 (which lacks capsule synthesis), and strain Bengal-2R1 (which fails to synthesize both the capsule and the O-antigen of lipopolysaccharide) were all found to have lost the surface layer. In addition, the capsule layer could also not be observed on the surface of V. cholerae strain O1. To determine the biological characteristics of the capsule of strains of the O139 serogroup, we investigated the serum killing activity and bacterial phagocytosis by polymorphonuclear leukocytes. The O139 strains were more resistant to the serum killing activity than were the V. cholerae O1 strain and the O139 mutant strains, thus suggesting that the existence of the capsule gave a serum-resistant character to the O139 strains. The surface character of the O139 strains had the same hydrophobic character as did that of the O139 mutant strains and the O1 strain. In addition, all the V. cholerae O1 and O139 strains examined, including the mutant strains, were effectively ingested by the human polymorphonuclear leukocytes. The number of ingested bacteria was not significantly different among the strains, and the ingestion of the acapsular O139 mutants thus showed that the capsule does not play an antiphagocytic role. These data suggest that the capsule of V. cholerae O139 has a physiological function different from that of the ordinal hydrophilic capsule that is found in invasive bacteria such as Klebsiella pneumoniae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050651
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    Phylogenetic affiliation and ultrastructure of uncultured magnetic bacteria with unusually large magnetosomes (1998)
    Springer
    Archives of microbiology 169 (1998), S. 136-147 
    Details
    ISSN: 1432-072X
    Keywords: Key words Magnetic bacteria ; Biomineralization ; Magnetite ; 16S rRNA ; In situ hybridization ; Ultrastructure ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Natural enrichments of magnetic bacteria from the Itaipu lagoon near Rio de Janeiro were dominated by coccoid-to-ovoid morphotypes that produced unusually large magnetosomes. To determine the phylogenetic position of these unusual microorganisms, 16S rRNA genes were retrieved from bacteria magnetically separated from sediment of the Itaipu lagoon by in vitro amplification and cloning of PCR products into a plasmid vector. Partial sequencing of the obtained clones revealed two clusters of closely related sequences affiliated to a distinct lineage consisting exclusively of magnetic bacteria within the α-subclass of Proteobacteria. For a detailed phylogenetic analysis, several almost complete sequences of the 16S rRNA genes were determined. One representative clone of each cluster provided a PCR template for the in vitro transcription of group-specific polynucleotide probes complementary to a variable region of the 16S rRNA molecule. At least three different morphotypes of magnetic bacteria were reliably identified by post-embedding hybridization of ultra-thin sections. Electron microscopic analyses of hybridized cells enabled for the first time a detailed description of the morphological variety and ultrastructure of phylogenetically identified, uncultured magnetic bacteria. Two distinct coccoid bacteria were identified by the transcript probe complementary to the 16S rRNA sequence mabrj12, whereas the probe complementary to the sequence mabrj58 allowed the identification of an ovoid morphotype that displayed magnetosomes with the largest volumes observed to date.
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    URL: http://dx.doi.org/10.1007/s002030050553
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    X-ray diffractometry and electron microscopy of DNA from Bacillus subtilis bound on clay minerals (1998)
    Springer
    Sciences of soils 3 (1998), S. 1-10 
    Details
    ISSN: 1432-9492
    Keywords: Transformation ; Clay-DNA complexes ; Nucleases ; X-ray diffraction ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract DNA bound on clay minerals, sand, and humic acids has been shown, both in vitro and in situ, to be capable of transforming bacteria and to resist degradation by nucleases, which could result in the crypticity of genes in soil and other natural habitats. To determine where DNA is bound on clay minerals, which may help to explain how bound DNA becomes resistant to degradation by nucleases but retains the ability to transform competent cells, chromosomal DNA from Bacillus subtilis bound on montmorillonite (M) and kaolinite (K) was examined by X-ray diffractometry and transmission and scanning electron microscopy. X-ray diffraction analysis showed that the basal spacings of M and K were not altered, indicating that this DNA did not significantly intercalate the clays. Scanning and transmission electron microscopy showed that the binding of this DNA was primarily on the edges of M and K, although some binding was also apparent on the planar surfaces. Based on the results of these studies, it is postulated that: 1.extension from the edges of the clays enables the unbound end of DNA to interact with receptor sites on competent cells and result in their transformation; and 2.binding on clays alters the electron distribution and/or conformation of DNA, which reduces its hydrolysis by nucleases.
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    URL: http://dx.doi.org/10.1007/s10112-998-0001-3
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    Distribution and submicroscopic immunogold localization of cellular prion protein (PrPc) in extracerebral tissues (1998)
    Springer
    Cell & tissue research 292 (1998), S. 77-84 
    Details
    ISSN: 1432-0878
    Keywords: Key words Prion protein (PrPc) ; Electron microscopy ; Secretory granules ; Membrane ; Extracerebral tissues ; Hamster ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  In transmissible spongiform encephalopathies (TSE), such as scrapie in animals and Creutzfeldt-Jakob disease in humans, the central event is the conversion of a host-encoded amyloidogenic protein (PrPc) into an abnormal isoform (PrPsc) that accumulates as amyloid in TSE brain. PrPc is a membrane sialoglycoprotein synthesized in the central nervous system and elsewhere. We have examined the ultrastructural localization of PrPc in numerous hamster and some human extracerebral tissues, by means of a post-embedding electron-microscopic method combined with immunogold labeling. In stomach, intestine, lung, and kidney from hamsters, and in stomach, kidney, and spleen from humans, immunogold labeling specific for PrPc is observed on various cellular substructures related to secretory pathways: Golgi apparatus, secretory globules, and plasma membrane. In mucous epithelial cells of stomach and intestine, PrPc appears to be concentrated in secretory globules, suggesting a role for PrPc in the secretory function of the digestive tract. The secretory aspect of PrPc may be a key to understanding the physiopathological mechanisms underlying TSE.
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    URL: http://dx.doi.org/10.1007/s004410051036
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    A role for vesicles in human basophil secretion (1998)
    Springer
    Cell & tissue research 293 (1998), S. 1-22 
    Details
    ISSN: 1432-0878
    Keywords: Key words Piecemeal degranulation ; Histamine ; Charcot-Leyden crystal protein ; Anaphylactic degranulation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The evidence for vesicular transport as a mechanism for secretion by human basophils is reviewed. Initially, direct electron-microscopic inspection of experimentally produced and sequentially biopsied contact allergy skin lesions revealed a unique form of secretion termed piecemeal degranulation, characterized by the slow emptying of secretory granule contents (with retention of empty containers) in the absence of extrusion of entire granules. Budding of small vesicles to/from secretory granules was observed, and cytoplasmic vesicles were abundant. A generalized degranulation model was proposed to unify classical regulated secretion and this new form of secretion. Investigation of the mechanism(s) of secretion from human basophils required the development of numerous tools and resources. Chief among these were: (a) isolation and purification of circulating basophils; (b) identification of specific growth factors to increase the supply of this rare granulocyte; (c) understanding of secretogogue mechanisms and reliable analyses of secreted basophil products; and (d) development of ultrastructural preparations allowing imaging of small vesicles and quantifiable small electron-dense tags for granule materials in small vesicles. Applications of these tools to well-defined models of basophil secretion have established a role for vesicles as a mechanism for effecting secretion of histamine and the Charcot-Leyden crystal protein from activated human basophils.
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    URL: http://dx.doi.org/10.1007/s004410051093
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    Maturation of rat dendritic cells during intrahepatic translocation evaluated using monoclonal antibodies and electron microscopy (1998)
    Springer
    Cell & tissue research 294 (1998), S. 503-514 
    Details
    ISSN: 1432-0878
    Keywords: Key words Dendritic cells ; Maturation ; Intrahepatic translocation ; Immunohistochemistry ; Electron microscopy ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Specific populations of hepatic sinusoidal cells were stained with monoclonal antibodies that recognize monocytes/macrophages (ED1), tissue macrophages (Kupffer cells) (ED2), MHC class II (Ia) antigen (MRC OX6), and dendritic cells/γ,δ T-cells (MRC OX62) and analyzed by light and electron microscopy. The majority of ED1+ and/or ED2+ cells were localized to the hepatic parenchyma, whereas OX6+ and/or OX62+ cells were more densely distributed within Glisson’s sheath than in the hepatic parenchyma. Double-immunoperoxidase staining of normal liver for ED1, ED2, and OX6 identified dendritic cells (DC) of two different phenotypes, ED1+ED2–OX6+ and ED1–ED2–OX6+. DC can be classified into three different types based on ultrastructural characteristics. The first type (type I) is characterized by one or more long cytoplasmic processes and a well-developed lysosomal system. The second type (type II) has an inconspicuous lysosomal system, abundant hyaloplasm, and characteristic short cytoplasmic processes. The third type (type I–II) has cytologic features intermediate between those of type I and type II DC. At the electron-microscopic level, these three cell types are found in the sinusoidal lumen, whereas the majority of type II DC are located in the space of Disse and Glisson’s sheath. Furthermore, some OX6-labeled elongated DC appeared to traverse the lumen of sinusoids through endothelial pores to enter the space of Disse. One hour after intravenous injection of latex particles (0.81 μm in diameter), numerous latex-laden dendritic cells (ED1+OX6+, type I and type I–II) were detected in the lumen of hepatic sinusoids, but not in the space of Disse or Glisson’s sheath. These findings suggest that normal rat liver contains resident dendritic cells which downregulate phagocytic activity and mature into potent accessory cells during migration from the portal vein toward the central vein. These DC then traverse the sinusoidal lumen to the hepatic lymph system via the space of Disse.
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    URL: http://dx.doi.org/10.1007/s004410051201
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    Interaction of the Escherichia coli DnaA protein with bacteriophage k DNA (1998)
    Springer
    Molecular genetics and genomics 259 (1998), S. 679-688 
    Details
    ISSN: 1617-4623
    Keywords: Key words Bacteriophage λ ; DnaA-DNA interactions ; Electron microscopy ; DNA-protein complexes ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Interaction of the Escherichia coli DnaA (replication initiator) protein with restriction fragments of phage λ DNA demonstrated differential binding of DnaA along the whole λ DNA. Interaction of DnaA with the λ replication region (from the promoter p R to the origin of replication, oriλ) demonstrated a strong binding of DnaA to the region around the p o promoter where synthesis of a short antisense oop RNA is initiated. The four sequences protected by DnaA (two 9mers and two 5mers) are not related even to a relaxed DnaA box. The pattern of protection of these four sequences and the location of three DNase I hypersensitive sites in the λ DNA r strand, together with results of mobility shift assays and electron microscopy studies, may indicate an interaction involving DnaA monomers bound to different DNA positions on one side of the helix and the formation of higher-order nucleoprotein structures. Therefore, it is tempting to suggest that DnaA, in addition to its activity in regulation of replication and transcription, could be considered as a factor which structures certain chromosomal regions.
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    URL: http://dx.doi.org/10.1007/s004380050863
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    Electron and X-ray microscopic analyses of reaggregated materials obtained after fractionation of dissolved sporopollenin (1998)
    Springer
    Protoplasma 204 (1998), S. 13-21 
    Details
    ISSN: 1615-6102
    Keywords: Sporopollenin ; Solubilisation ; 2-Aminoethanol ; Reaggregation ; Electron microscopy ; X-ray microscopy ; Thypha angustifolia L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Exines fromTypha angustifolia L. pollen were dissolved in hot 2-aminoethanol. The solubilisate was successively fractionated and reaggregated via a dialysis cascade with dialysis tubings of different exclusion volumina. Four fractions of reaggregated material with different molecular mass were obtained. Fraction 1 with a molecular mass above 25,000 Da, fraction 2 with a molecular mass between 10,000–25,000 Da, fraction 3 with a molecular mass between 5,000–10,000 Da, and fraction 4 of a molecular mass lower than 5,000 Da. The fractions were comparatively analysed by scanning and transmission electron microscopy and X-ray microscopy. The material of the fractions with a molecular mass above 10,000 Da exhibit high congruence to the initial material. Analysis of the reaggregated material with the lowest molecular mass revealed special distinct substructures which in form and size showed high similarities to substructures of exines described in literature. In detail, spherical substructures consisting of an electron-dense core surrounded by an electron-transparent corona and in addition elongated substructures with a distinctive surface sculpture were detected.
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    URL: http://dx.doi.org/10.1007/BF01282289
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    Callose deposition and breakdown, followed by phytomelan synthesis in the seed coat ofGasteria verrucosa (Mill.) H. Duval (1998)
    Springer
    Protoplasma 201 (1998), S. 221-230 
    Details
    ISSN: 1615-6102
    Keywords: Callose ; Electron microscopy ; Gasteria verrucosa ; Phenolics ; Phytomelan ; Seed coat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the seed coat ofGasteria verrucosa the deposition of phytomelan takes place during seed development in three stages. Phytomelan is a black cell wall material which is chemically very inert. First the radial walls and part of the transverse cell wall of the outer epidermis of the outer integument become thickened by exocytosis of dictyosome vesicles. Callose is deposited at the tangential plasma membrane against those walls. After the callose deposition about two thirds of the original cell volume is filled with callose. During the second stage the callose is broken down, probably into glucose monomers or small polymers. At the same time cellulose is deposited at the outer tangential plasma membrane, forming a wall between the dissolving callose and the plasma membrane. In the third phase small granules appear in the solution of dissolved callose. which grow out and finally fuse to form a block of phytomelan, consisting of spherical 15-nm units. Remarkable is the function of the callose: it determines the size of the phytomelan block, and it probably functions as carbohydrate source for the phytomelan synthesis and/or for the cellulose inner layer. In this study transmission electron microscopy and cryo scanning electron microscopy are used to study the three developmental stages of the formation of the phytomelan layer.
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    URL: http://dx.doi.org/10.1007/BF01287418
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    Virus assembly inHincksia hincksiae (Ectocarpales, Phaeophyceae) An electron and fluorescence microscopic study (1998)
    Springer
    Protoplasma 203 (1998), S. 153-167 
    Details
    ISSN: 1615-6102
    Keywords: Algae ; Virus assembly ; DAPI staining ; Electron microscopy ; Hincksia hincksiae ; Immunofluorescence ; Marine double-stranded DNA virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The filamentous brown algaHincksia hincksiae can be infected by a large icosahedral double-stranded DNA virus (HincV-1). The virus shows extended latency and is replicated only in cells homologous to sporangia. Virus formation was studied by transmission electron microscopy, DAPI staining, and β-tubulin immunofluorescence. Inhibition of cytokineses results in multinucleate cells, which are the first indication of virus replication in productive cells; the microtubular cytoskeleton does not seem to be affected by the virus. Replication of viral DNA begins in the nuclei, which increase in size and eventually disintegrate. Virus assembly takes place in a mixed nucleo-/cytoplasm. Capsids bud from cisternae, which are interpreted as modified endoplasmic reticulum aggregated to virus assembly centres. The internal membranous component of the virus is thus derived from the endoplasmic reticulum. The particles are empty (electron translucent) when assembled, and the nucleoprotein core seems to be packaged subsequently through an opening in the capsid. A number of fine structural features not previously reported from brown algae and related to virus formation are described. Our results on Hincksia hincksiae virus are compared with observations made on various other icosahedral DNA viruses infecting eukaryotic algae and animals.
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    URL: http://dx.doi.org/10.1007/BF01279472
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    Renewing olfactory receptor neurons in goldfish do not require contact with the olfactory bulb to develop normal chemical responsiveness (1997)
    Springer
    Journal of comparative physiology 181 (1997), S. 425-437 
    Details
    ISSN: 1432-1351
    Keywords: Key words Olfactory receptor cells ; Olfactory bulbectomy ; Olfactory axotomy ; Electrophysiology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study investigated whether contact with the olfactory bulb was necessary for developing and renewing olfactory receptor neurons (ORNs) to attain normal odorant responsiveness, and whether the anatomical and functional recoveries of the olfactory epithelium were similar in both bulbectomized (BE) and bilaterally axotomized (AX) preparations. In vivo electrophysiological recordings were obtained in response to amino acids, a bile acid [taurolithocholic acid sulfate(TLCS)] and a pheromonal odorant [17α, 20β,-dihydroxy-4-pregnen-3-one (17,20P)] from sexually immature goldfish. Both transmission and scanning electron microscopy indicated that the olfactory epithelium degenerated in BE and AX goldfish. Within 1–2 weeks subsequent to the respective surgeries, responses to high concentrations (〉0.1 mmol · l−1) of the more stimulatory amino acids remained, whereas responses were no longer obtainable to TLCS and 17,20P. At 4 weeks, responses to amino acid stimuli recovered to control levels, while responses to TLCS and 17,20P were minimal. By 7 weeks post bilateral axotomy, the olfactory epithelium recovered to a condition similar to control sensory epithelium; however, the rate of degeneration and proliferation of receptor neurons in BE preparations appeared to remain in balance, thus blocking further recovery of the olfactory epithelium. At 7 weeks post surgery, odorant responses of AX and BE goldfish to TLCS and 17,20P were still recovering.
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    URL: http://dx.doi.org/10.1007/s003590050126
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    Scots pine needle injuries at subarctic industrial sites (1997)
    Springer
    Trees 11 (1997), S. 378-387 
    Details
    ISSN: 0931-1890
    Keywords: Key words Pinus sylvestris (L.) ; Electron microscopy ; Heavy metals ; Multi-stress-symptoms ; SO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Injuries to needles of Scots pines (Pinus sylvestris L.) growing in nutrient-poor soils on the Kola Peninsula collected in April 1991 were studied on a gradient of increasing distances (10 – 115 km) from the Monchegorsk nickel smelter, Russia, which emits SO2, Ni and Cu. The condition of the mesophyll cells was quantified from needles of the two latest age classes using a light and an electron microscope. The damage to the ultrastructure consisted of multistress symptoms caused by excess sulphur, heavy metals, frost, acidic precipitation and ozone. Injuries were most commonly manifested in the form of dark, irregularly shaped chloroplasts with protrusions and light thylakoids and plastoglobuli. These symptoms gradually disappeared with increasing distance and decreasing deposition rate. Concentrations of sulphur, copper and nickel decreased towards more distant sites where normal levels of the latter two elements were reached. Sulphur concentrations remained above background throughout the distance gradient. In the closest plots to the smelter area, cell collapse under the stomata and epidermis related to acute SO2 and heavy metal effects was found, whereas further away symptoms were more diverse, pointing towards the effects of ozone, acidic deposition and thereby decreased frost tolerance. The additive multistress symptoms were clearly seen in the area up to 40 km from the smelter where needle Cu concentration was above 110 ppm, Ni concentration above 39 ppm and S concentration above 1343 ppm.
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    URL: http://dx.doi.org/10.1007/s004680050099
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    Effects of brefeldin-A and monensin on organelle distribution and morphology in the preimplantation mouse embryo (1997)
    Springer
    Development genes and evolution 206 (1997), S. 503-514 
    Details
    ISSN: 1432-041X
    Keywords: Key words Preimplantation mouse embryo ; Brefeldin-A ; Monensin ; Golgi ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The intracellular trafficking of integral membrane and secreted proteins is likely to be a key element involved in the morphogenesis and differentiation of the early mammalian embryo. In this study, we used transmission electron microscopy (TEM) to analyse the effects of brefeldin-A (BFA) and monensin, well known inhibitors of vesicular protein trafficking in somatic cells, on the structure of preimplantation mouse embryos. Both BFA and monensin distinctively altered the morphology of Golgi compartments in the blastomeres of treated morulae. BFA-treated morulae lacked recognizable Golgi complexes but possessed heterogeneous organelle clusters consisting of an abundance of smooth tubular and vesicular membrane compartments in addition to mitochondria, endosomes and lysosomes. Treatment of morulae with monensin was associated with swelling of Golgi compartments in addition to altering the morphology of mitochondria, lysosomes and the plasma membrane. BFA, and to a lesser extent monensin, inhibited cytokinesis as evidenced by the detection of binucleate blastomeres. In addition, BFA induced morulae to decompact. These latter effects have not been reported previously for these agents in mammalian somatic cell lines or other vertebrate or invertebrate embryos. These results provide the first demonstration of the structural effects of BFA and monensin on cells of the early mammalian embryo, some of which are consistent with the known actions of these agents on components of the vesicular protein trafficking system in mammalian somatic cells. This information serves as a foundation for the further use of these agents in studies of vesicular protein trafficking as an agent of preimplantation morphogenesis.
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    URL: http://dx.doi.org/10.1007/s004270050081
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    Neuropeptide Y-immunoreactive intracardiac neurones, granule-containing cells and nerves associated with ganglia and blood vessels in rat and guinea-pig heart (1997)
    Springer
    Cell & tissue research 289 (1997), S. 445-454 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Intracardiac neurones ; Innervation ; Heart ; Neuropeptide Y ; Immunocytochemistry ; Electron microscopy ; Rat (Sprague Dawley) ; Guinea-pig (Dunkin Hartley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Intrinsic neuropeptide Y-containing neurones in rat and guinea-pig hearts were studied at the ultrastructural level by the pre-embedding peroxidase-antiperoxidase immunocytochemical technique. Intracardiac neuronal cell bodies were often weakly or moderately immunostained, and the labelling was usually pronounced in the Golgi complex, multivesicular bodies, some cisterns of granular endoplasmic reticulum and large granular vesicles. Neuropeptide Y-immunoreactive nerve fibres were also observed in association with intracardiac neurones. A subpopulation of neuropeptide Y-immunoreactive granule-containing cells in the rat heart are described for the first time and were very heavily labelled; other granule-containing cells were non-immunoreactive, but were contacted by neuropeptide Y-containing nerves. Preterminal regions of nerve fibres that were located in nerve bundles were only weakly neuropeptide Y-immunoreactive, in contrast to the heavy labelling observed in varicosities that contained many synaptic vesicles. Many neuropeptide Y-immunoreactive nerve fibres were associated with the coronary vasculature and were particularly prominent in the walls of small arteries and arterioles where labelled nerve varicosities were present close to the smooth muscle cells. Immunoreactive nerves were also seen in the myocardium, usually near to capillaries. In axonal varicosities, the central core of large granular vesicles was immunolabelled, and electron-dense immunoreactive material outlined the membranes of small and large clear vesicles. The significance of neuropeptide Y-immunoreactive intracardiac neurones and granule-containing cells and the origin of associated labelled nerve fibres in the heart are discussed.
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    URL: http://dx.doi.org/10.1007/s004410050890
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    Immuno-electron microscopy reveals that the excitotoxin quinolinate is associated with the plasma membrane in human peripheral blood monocytes/macrophages (1997)
    Springer
    Cell & tissue research 290 (1997), S. 633-639 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Quinolinic acid ; Interferon-γ ; Kynurenine ; Electron microscopy ; Immunocytochemistry ; Excitotoxicity ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract.  Quinolinate (QUIN), a tryptophan-derived excitotoxin, was localized ultrastructurally in human peripheral blood monocytes/macrophages (MØ) by immuno-electron microscopy. A combined carbodiimide/glutaraldehyde/paraformaldehyde-based fixation procedure was developed for optimal retention of QUIN in the cell as well as minimal loss of ultrastructure; a silver-enhanced colloidal gold detection system was used for electron-microscopic analysis. Gold particles representing QUIN immunoreactivity were associated with the inner side of the plasma membrane in normal MØ. The number of gold particles increased significantly when QUIN levels were elevated by treatment with its precursor kynurenine, but location of the gold particles remained essentially the same under this condition. Treatment with interferon-γ increased the number of Golgi bodies, vacuoles and pseudopodia, reflecting the activated state of the cell. Significantly increased numbers of gold particles representing QUIN were detectable in approximately the same location as in the case of kynurenine treatment. Combined treatment with kynurenine and interferon-γ maximally increased the number of gold particles at the periphery of the cell. The pseudopodia were intensely stained with gold particles, while they were not detectable in the inner part of the cytoplasm or in any other organelle even under this activated condition. The significance of the specific location of QUIN revealed in the present study and its relation to the release and subsequent actions of QUIN are discussed.
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    URL: http://dx.doi.org/10.1007/s004410050969
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    Synaptic exocytosis of dense-core vesicles in blue crab (Callinectes sapidus) stomach muscles (1997)
    Springer
    Cell & tissue research 289 (1997), S. 517-526 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Neuromuscular junction ; Synaptic vesicles ; Vesicle fusion ; Electron microscopy ; Callinectes sapidus (Crustacea)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Neuromuscular terminals of a single motoneuron to four muscles (CPV7a, GM5a, CV2, and CV3) in the stomach of the blue crab Callinectes sapidus showed structural evidence for the exocytotic release of dense-core vesicles exclusively at synapses. The primary evidence was the appearance of dense cores in the synaptic cleft, accompanied by indentations of the presynaptic or postsynaptic membrane. In their simplest form, these consisted of an omega-shaped figure of the presynaptic membrane enclosing one dense core, denoting release of a single dense-core vesicle. A larger indentation of the presynaptic membrane enclosing several dense cores denoted multiple release. A more complex form of multiple release was where the presynaptic membrane was normal, but the postsynaptic membrane elaborated into a sac projecting into the granular sarcoplasm and filled with dense cores. The postsynaptic sac in some instances was compressed into a thin, fingerlike extension, which lacked dense cores and, at its distal end, separated into small cisternae, suggesting a mechanism for membrane recycling. Profiles depicting single and multiple releases of dense-core vesicles were found more frequently at neuromuscular terminals that release relatively large amounts of transmitter with a single stimulus, such as CV2 and CV3, compared to those releasing smaller amounts, such as CPV7a and GM5a. The disparity in release sites among the four muscles of this single motor unit and the fact that many of the multiple-release figures were closely adjacent to the active zones for transmitter release suggest a possible modulatory role for dense-core vesicles in synaptic transmission. Such modulation may be long lasting, as implied by the postsynaptic sacs, which may permit prolonged release of the contents of their dense cores into the synaptic cleft. This is in keeping with the functional role of these stomach muscles, which is to be continuously active for long periods of time.
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    URL: http://dx.doi.org/10.1007/s004410050897
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    Immunoreactive excitatory amino acids in the parietal eye of lizards, a comparison with the pineal organ and retina (1997)
    Springer
    Cell & tissue research 287 (1997), S. 275-283 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Parietal eye ; Pineal organ ; Retina ; Glutamate ; Aspartate ; Immunocytochemistry ; Electron microscopy ; Lacerta muralis ; Lacerta agilis ; Lacerta viridis (Lacertilia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The fine structure of the organ and the localization of the excitatory amino acids glutamate and aspartate were studied in the parietal eye of lizards by postembedding immunoelectron microscopy. The parietal eye contains cone photoreceptor cells, secondary neurons, and ependymal and lens cells. The photoreceptors form long inner and outer segments, some of them being paired as ”twin-photoreceptors” by zonulae adherentes. Perikarya of neurons bear sensory cilia (containing 9×2+0 pairs of tubules) extending into the intercellular space. No neurohormonal terminals are present in the parietal eye. A higher immunoreactivity to glutamate than to aspartate is found in the photoreceptors and in the secondary neurons of the parietal eye. Glutamate immunogold labeling is more intense in the axonal processes of photoreceptors and neurons and in most of the nerve fibers of the parietal nerve running to the brain stem. Weak aspartate and glutamate immunoreactivity can be detected in the ependymal and lens cells. A similar distribution of immunoreactive amino acids is found in the photoreceptors, secondary neurons, and ependymal glial elements of the pineal organ, and retina of the lateral eye of the same animals. Immunoreactive glutamate accumulates in the axons of photoreceptors and secondary neurons of the parietal eye suggesting that this excitatory amino acid acts as a synaptic mediator in the neural efferentation of the organ. Thus, the efferent light-conducting pathway of the parietal organ is similar to that of the pineal organ and lateral eye retina. As the Mullerian cells of the retina, the ependymal and lens cells of the parietal eye and the ependymal-glial cells of the pineal organ may play a role in the metabolism and/or elimination of excitatory amino acids released by photoreceptors.
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    Expression of basic fibroblast growth factor-like immunoreactivity in the nuclei of regenerating hepatocytes (1997)
    Springer
    Cell & tissue research 288 (1997), S. 517-527 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Liver ; Subcellular fractions ; Immunohistochemistry ; Electron microscopy ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. This study, utilizing rats subjected to two-thirds partial hepatectomy or sham operation, was designed (1) to investigate the content of basic fibroblast growth factor (bFGF) in the subcellular fractions of regenerating and sham-operated rat livers by immunoblot experiments and enzyme-linked immunosorbent assay (ELISA), (2) to show that bFGF immunoreactivity and proliferating cell nuclear antigen (PCNA) immunoreactivity are markers for hepatocellular mitosis before and after partial hepatectomy, and (3) to observe the location and fine structure of the bFGF immunoreaction within the regenerating liver with special attention to bFGF immunoreactivity in the nuclei of regenerating hepatocytes. Immunoblot experiments and ELISA showed a transient increase in high-molecular-weight forms of bFGF in the nuclear subcellular fraction of regenerating liver 48 h after partial hepatectomy. By light microscopy, bFGF and PCNA immunoreactivities were detected in the nuclei of regenerating hepatocytes. Electron microscopy demonstrated bFGF-like immunoreactivity mainly in the nuclear euchromatin and rarely in the heterochromatin or nucleoli of regenerating hepatocytes. The transient increase in high-molecular-weight forms of bFGF in the nuclear euchromatin of regenerating hepatocytes, together with the concomitant expression of PCNA in the regenerating liver, suggests an important role of the high-molecular-weight forms of bFGF in hepatocyte proliferation and/or mitosis, although authentic bFGF with a molecular form of 18 kDa is not considered to be involved in hepatic regeneration.
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    URL: http://dx.doi.org/10.1007/s004410050837
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    Osmoregulatory mutants that affect the function of the contractile vacuole inChlamydomonas reinhardtii (1997)
    Springer
    Protoplasma 200 (1997), S. 99-111 
    Details
    ISSN: 1615-6102
    Keywords: Chlamydomonas reinhardtii ; Contractile vacuole ; Electron microscopy ; Videomicroscopy ; Osmoregulation ; Osmoregulatory mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four independent osmoregulatory mutants,osml, osm3,osm4, and osm7, were isolated on the basis of their requirement for growth medium of high osmotic strength. In normal low-osmoticstrength medium, in contrast to wild-type cells, the mutants grow poorly or not at all; in distilled water mutant cells are immobilized and eventually swell and burst. The mutants were examined by ordinary brightfield and phase-contrast microscopy, videomicroscopy, and electron microscopy. The four mutants showed different defects in the contractile vacuole (CV) cycle. Timing of various stages of the CV cycle showed thatosm1 was affected primarily in the early stage of the cycle when the CV begins to grow,osm3 primarily in midcycle when vacuoles fuse to form the CV proper,osm7 at a late stage of the cycle at docking and fusion of the CV with the plasma membrane, andosm4 during contraction of the CV. At the electron microscopic level, in dilute medium, mutant cells by comparison with wild-type cells had large autophagosomes, swollen mitochondria, and dilated ER cisternae. Although electron microscopy showed general abnormalities of the contractile vacuoles consistent with the videomicroscopic observations of living cells, no obvious vacuole membrane abnormalities were seen which would explain the mutational defects. The mutations help define the separate processes that contribute to the coordinated CV cycle inChlamydomonas, and open the way to eventual isolation of some of the genes responsible for CV function.
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    Structure and behavior of contractile vacuoles inChlamydomonas reinhardtii (1997)
    Springer
    Protoplasma 198 (1997), S. 73-84 
    Details
    ISSN: 1615-6102
    Keywords: Chlamydomonas reinhardtii ; Contractile vacuole ; Osmoregulation ; Videomicroscopy ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The contractile vacuole (CV) cycle ofChlamydomonas reinhardtii has been investigated by videomicroscopy and electron microscopy. Correlation of the two kinds of observation indicates that the total cycle (15 s under the hypo-osmotic conditions used for videomicroscopy) can be divided into early, middle, and late stages. In the early stage (early diastole, about 3 s long) numerous small vesicles about 70–120 nm in diameter are present. In the middle stage (mid-diastole, about 6 s long), the vesicles appear to fuse with one another to form the contractile vacuole proper. In the late stage (late diastole, also about 6 s long), the CV increases in diameter by the continued fusion of small vesicles with the vacuole, and makes contact with the plasma membrane. The CV then rapidly decreases in size (systole, about 0.2 s). In isosmotic media, CVs do not appear to be functioning; under these conditions, the CV regions contain numerous small vesicles typical of the earliest stage of diastole. Fine structure observations have provided no evidence for a two-component CV system such as has been observed in some other cell types. Electron microscopy of cryofixed and freeze-substituted cells suggests that the irregularity of the profiles of larger vesicles and vacuoles and some other morphological details seen in conventionally fixed cells may be shrinkage artefacts. This study thus defines some of the membrane events in the normal contractile vacuole cycle ofChlamydomonas, and provides a morphological and temporal basis for the study of membrane fusion and fluid transport across membranes in a cell favorable for genetic analysis.
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    URL: http://dx.doi.org/10.1007/BF01282133
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    Selective UV-induced damage to short-wavelength receptor cells in the butterflyPapilio xuthus (1997)
    Springer
    Protoplasma 200 (1997), S. 112-115 
    Details
    ISSN: 1615-6102
    Keywords: Electron microscopy ; UV-induced cell damage ; Photoreceptor ; Eye ; Lepidoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A technique that allows the specific inactivation of short-wavelength-sensitive photoreceptive cells has been needed for a long time. Such a technique could be useful in studies on the role(s) of UV-receptors in circadian rhythmicity, recognition of floral patterns, homing behaviour, and mate selection in arthropods. We provide ultrastructural evidence that short-wavelength receptor cells can be selectively damaged without affecting other spectral-cell types. Since the method does not require the killing of the experimental animal, the latter can be used in behavioural or other follow-up tests.
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    URL: http://dx.doi.org/10.1007/BF01280739
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    Hydrogen Bonding and Conformational Analysis of Chelate-Stabilized Alkoxopalladium(II) Complexes Derived from Amino Alcohol Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 35-44 
    Details
    ISSN: 0009-2940
    Keywords: Alkoxopalladium(II) ; Conformational analysis ; Hydrogen bonding ; Two-dimensional and cage structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of palladium acetate with two equivalents of di- and triethanolamines RN(CH2CH2OH)2 in the presence of a base affords the new chelate-stabilized alkoxo Pd(II) complexes [Pd(OCH2CH2N(R)CH2CH2OH)2] [R = Me (1), Et (2), n-Bu (3), benzyl (4) or CH2CH2OH (5)]. These N,O-ligated complexes are isolated in high yield as yellow, crystalline solids and are thermally stable despite the presence of several β-hydrogen atoms in the ligand system. Both complexes possess a square-planar palladium coordination geometry with the two oxygen atoms positioned mutually trans. The most notable difference in the molecular structures is that 1 forms a two dimensional network of intermolecular O-H≡O hydrogen bonds, whereas 5 forms intramolecular O-H⃛O hydrogen bonds, which cage the palladium center. In solution 1-4 exist as a diastereoisomeric mixture (a racemic enantiomeric pair SNSN, RNRN and a mesomeric form RNSN) in a 1:1 molar ratio, and this ratio is independent of temperature in nonalcoholic solvents, When complexes 1-4 are dissolved in protic solvents (e.g. MeOH) the diastereomeric excess is temperature-dependent due to an exchange process between the meso diastereoisomer and the (racemic) enantiomeric pair. Thermodynamic parameters for this process in a mixture of MeOH-toluene have been determined with NMR and show this process to be influenced by the steric nature of the alkyl substituent (R) on nitrogen. A conformational analysis based on 1H-NMR coupling constants within the N,O-chelate ring of complexes 1-4 provides details on the solution structure of the ring in both diastereoisomers.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300106
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    Synthesis of Functionalized Carbamates through a Palladium-Catalyzed Reductive Carbonylation of Substituted Nitrobenzenes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 13-22 
    Details
    ISSN: 0009-2940
    Keywords: Carbamates ; Catalysis ; Substituted nitrobenzenes ; Palladium ; Reductive carbonylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The palladium-catalyzed reductive carbonylation of ortho and para-substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1, 10-phenanthroline)2(triflate)2 catalyst system, the scope of the reaction has been studied. Substrates with electron-donating substituents at the para position were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. the selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron-withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at the ortho position of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion ot the nitro group. Especially with 4-nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis for N-protected amines containing carboxylic acid function.
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    URL: http://dx.doi.org/10.1002/cber.19971300104
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    Dimeric Silver(I) Complexes of Some Isothiazole-Based LigandsDedicated to Prof. Dr. Rolf Gleiter on the occasion of this 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 95-100 
    Details
    ISSN: 0009-2940
    Keywords: Isothiazole complexes ; Dinuclear silver(I) complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of isothiazole-based potential ligands bearing substituents with additional donor sites in the 5-position of the heterocycle was synthesized [3-Me-5-R-C3HNS; R = CH=N(CH2)2py (1), CH=NCH2py (2), CH2N(CH2CH2NEt2)2 (4), (CH2)2SMe (5)]. Upon reaction with AgO3SCF3 they formed complexes [(1)AgOSO2CF3]2 (6), [(2)AgOSO2CF3]2 (7), [(4)Ag]2+2(O3SCF-3)2 (8) and [(5)AgOSO2CF3]2 (9), respectively. 6, 8 and 9 were shown by X-ray structural analyses to consist of dimeric units L2Ag2+2, either discrete (8), coordinated by terminal CF3SO-3 units (6). In 8 and 9 the isothiazole moiety is bonded to the metal center via the ring-N. The coordination potential of the isothiazole heterocycle is discussed.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300115
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    Synthesis and Structure of Binuclear Single-Bridged Bis[(phosphane)gold(I)]halogenonium Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 115-118 
    Details
    ISSN: 0009-2940
    Keywords: Gold complexes ; Bromonium complex ; Halogenonium complex ; Halogen, two-coordinate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of (R3P)AuX (X = Cl, Br, I) with [(R3P)Au]+ BF-4 obtained from (R3P)AuCl and AgBF4 in tetrahydrofuran, lead to cationic binuclear gold(I) complexes of the general formula ([(R3P)Au]2X}+ BF-4. A number of chloro- (R = Ph, o-Tol, Mes, Bzl, Et), bromo- (R = Ph, o-Tol, Mes) and iodo-bridged (R = Ph, Mes) complexes of this type have been isolated and identified on the basis of their analytical and spectroscopic data. The crystal structure of bis[(triphenylphosphane)gold(I)]bromonium tetrafluoroborate was determined by single-crystal X-ray diffraction. The cations contain two-coordinate bromine atoms with an Au-Br-Au angle of 96.83(3)°.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300119
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    A Specific Route to Enantiomerically Pure Asymmetric (η6-Arene)(η4-1,5-cyclooctadiene)Ru(0) ComplexesDedicated to Professor Rolf Gleiter on the occassion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 123-130 
    Details
    ISSN: 0009-2940
    Keywords: Arene complexes ; Ruthenium compounds ; Electrophilic substitution ; Lithiation ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral or achiral (arene)(COD)Ru complexes can be made by replacing the η6-ligands of (η4-1,5-COD)(η6-1,3,5-cyclooctatriene)Ru (1) or (η4-1,5-COD)(η6-naphthalene)Ru (2) by a suitable arene. This well known reaction has been extended to mono- and dibromoarenes and we report a novel route to substituted (arene)(COD)Ru species, utilizing (bromoarene)-(COD)Ru as starting materials. These facilitate a rapid bromine-lithium exchange reaction with nBuLi at low temperatures and the lithiated species react readily with alkyl chloroformates as electrophiles. By using chiral electrophiles [alkyl = (-)-menthyl] enantiomerically pure or diastereomeric complexes containing CO2R* groups are formed, depending on the symmetry of the original complex. A diastereomeric 1:1 mixture was separated by recrystallization. All (arene)-(COD)Ru complexes tested so far are useful as catalysts for the hydrogenation of simple alkenes at room temperature.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300121
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    Recent Advances in C-F Bond Activation (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 145-154 
    Details
    ISSN: 0009-2940
    Keywords: Fluorocarbons ; C-F bond activation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The main reaction pathways which lead to the breaking of C-F bonds in perfluoroalkanes and -arenes are discussed. Emphasis is placed on recent developments and on the mechanistic patterns that emerge.
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    URL: http://dx.doi.org/10.1002/cber.19971300203
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    Metal Atoms in the Synthesis of Metal Clusters, VIII.On the Reaction of Sterically Demanding Cyclopentadiene Ligands with Cobalt Atoms: Synthesis, Crystal Structure, Spectroscopic Behavior, and Reactivity of Di-, Tri- and Tetranuclear Hydrido Clusters of CobaltDedicated to Professor IV Siehert on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 161-170 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metal-vapor reactions of Co atoms with 1,3-tBu2CpH (1a), 1,3-tBu2CpH (1a), 1,2,4-tBu3CpH (1b) and EtMe4CpH (1c) are described. With 1a the two mononuclear complexes [(η5-tBu2Cp) (η4-tBu2-1,3-cyclopentadiene)Co] (2a) and [(η5-tBu2Cp)2Co] (3a) were isolated, together with the dinuclear cobalt cluster [{(η5-tBu2Cp)Co}2H3] (4a) and trace amounts of the tetranuclear cluster [{(η5-tBu2Cp)CoH}4] (5a). The molecular structures of 3a and 4a were determined by X-ray diffraction. Reaction of 1b with Co atoms afforded a single product, the dinuclear cluster [{(η5-tBu3Cp)Co}2H3] (4b), whose molecular structure was determined by single-crystal X-ray diffraction. Both, 4a and 4b exhibit extremely short Co-Co distances [2.244(1) (4a) and 2.242(1) Å (4b)], as found for the Me5Cp analog [{(η5-Me5Cp)Co}2H3] (4c). Reaction of an isomeric mixture of Me4EtCpH (1c) with Co atoms furnished the mononuclear sandwich [ (η5-Me4EtCp)(η4-Me4Et-1,3- cyclopentadiene)Co] (2b), the trinuclear hydridocobalt cluster [{(η5-Me4EtCp)Co}3H4] (6a) and the tetranuclear hydridocobalt cluster [{(η5-Me4EtCp)Co}4H4] (5c). The molecular structure of 5c was determined by X-ray crystallography and revealed a tetrahedral arrangement of the cobalt atoms. The electrochemical behavior of the dinuclear complexes 4a-4c was studied by cyclic voltammetry. Reversible redox couples were found for all three compounds, with a correlation between the degree of alkyl substitution and their respective cathodic shifts. Compounds 4a and 4b react with CO to yield the mononuclear and dinuclear complexes [ (η5- CpR)Co(CO)2] (R=1,3-tBu2, 1,2,4-tBu3) (7a and 7b) as well as [{(η5-CpR)CO}2(CO)2] (8a and 8b). Reaction of the trinuclear hydridocobalt cluster 6a and its Me5Cp analog 6b with AgBF4 in the presence of PEt3 yielded the heteronuclear clusters [{η5-Me4CPR)Co}3AgP(Et)3H4]+[BF4]- (R=Et, Me) (9a and 9b). 9a was structurally characterized by X-ray crystallography.
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    Generation and Synthetic Application of Metallated Methyl Isopropenyl Ether, A Substitute for Acetone Enolate (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 45-48 
    Details
    ISSN: 0009-2940
    Keywords: Metallated methyl isopropenyl ether ; Tetrahydrofurans ; 1-Oxabicyclo[4.3.0]heptanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl isopropenyl ether (1) has been metallated at low temperature with a 1:1 molar mixture of n-BuLi/t-BuOK in THF-hexane, and subsequently functionalized with a variety of electrophilic reagents. At temperatures higher than - 30°C, the metallated methyl isopropenyl ether (2) decomposes with formation of allene. When the suspension of 2 is allowed to warm up to room temperature in the presence of an additional equivalent of n-BuLi, the intermediary allene is converted into 1-propynyllithium (2c), which reacts with propylthiocyanate to give 1-propylthio-1-propyne (4). Some of the functionalization products were subjected to acidic hydrolysis affording the expected methyl ketones.
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    URL: http://dx.doi.org/10.1002/cber.19971300107
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    Asymmetric Catalysis, 105Part 104: Ref.. Stereoselective Hydrogenation of Folic Acid with Immobilized Optically Active Rhodium(I)/Diphosphane Catalysts (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 55-62 
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    ISSN: 0009-2940
    Keywords: Diastereoselective hydrogenation ; Folic acid ; Immobilized optically active rhodium(I)/diphosphane catalysts ; Leucovorin ; HPLC analysis of 5-formyltetrahydrofolic acid derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the hydrogenation of the C=N bonds in the pyrazine ring of the vitamin folic acid (1) optically active rhodium(I)/diphosphane complexes immobilized on supports such as silica gel or Al2O3 were used. The reduction was carried out at 50 bar hydrogen pressure in an aqueous solution buffered to pH 7. Thus, 5,6,7,8-tetrahydrofolic acid (2) was obtained which contains a new asymmetric center at C-6 of the pterine system. Therefore, in combination with the (S) configuration of the natural L-glutamic acid part of the molecule two diastereomers with (6S,S) and (6R,S) configuration arise. The relatively unstable tetrahydrofolic acid (2) was converted into its 5-formyl derivative folinic acid (4) by treatment with methyl formate/formic acid in a 5:1 mixture of DMSO/pyridine. The Ca salt of folinic acid (4) is the widely used drug leucovorin. The diastereomers were separated by silica gel HPLC. To the column bovine serum albumine (BSA) is covalently bound. With optically active rhodium(I)/diphosphane catalysts, immobilized on silica gel supports, a diastereoselectivity of up to 90% could be achieved in the hydrogenation of folic acid (1).
    Additional Material: 1 Ill.
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    Hexahydro-closo-hexaborane as a Ligand in Coordination Compounds: Syntheses and Crystal Structures of [M2(μ-bis-η3-B6H6)(PPh3)2] )M = Cu, Au) (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 405-408 
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    ISSN: 0009-2940
    Keywords: Hexahydro-closo-hexaborates ; Boron ; Bridging ligands ; NMR spectroscopy ; Gold ; Copper ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By reaction of (PPh3)3 CuCl and PPh3AuCl with [B6H6]2- in organic media, dinuclear complexes are formed containing the hexaborate as a bridging ligand coordinated to the metal centers by opposite B3 facets of the B6 cluster in a trihapto mode. This is verified by single-crystal X-ray structural analysis of the isotypical (Paā) compounds [Cu2μ-bis-η3-B6H6)(PPh3)2] (1) and [Au2(μ-bis-η3-B6H6)(PPh3)2)] (2) which showed the metal centers to be very close to the B3 plane [1.92 (1), 2.10 (2) Å. The 11B NMR spectra of the two compounds feature doublets, at δ= -15.32 in 1 and at -11.51 in 2, which are significantly shifted downfield in comparison to [B6H6]2- (δ= -17.2).
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    URL: http://dx.doi.org/10.1002/cber.19971300315
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    Crown Thioether Chemistry: Novel Silver(I) Complexes of 1,3-Dithiole-Annelated 1,4,7-Trithiacyclononane (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 425-429 
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    ISSN: 0009-2940
    Keywords: Silver complexes ; Crown compounds ; Thioethers ; 1,3-Dithioles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination chemistry of two crown thioethers 2,5,8,10,12-pentathiabicyclo[7.3.0]dodeca-1)9)-ene-11-thione (L) and -11-one (L') with Ag1 has been investigated by structural methods. Both thioethers act as tridentate ligands coordinating the silver ion in a trigonal fashion. In the case L, the 11- thione sulfur is coordinated additionally by another silver ion, to yield a polymeric chain with a distorted-tetrahedral geometry about the metal ion. Despite differing only in its carbonyl chalcogen, L' forms six-coordinated, monomeric complexes.
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    URL: http://dx.doi.org/10.1002/cber.19971300319
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    Unsymmetric Dinucleating Ligands for Metallobiosite Modelling (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 433-442 
    Details
    ISSN: 0009-2940
    Keywords: Metallobiosites ; Metalloproteins ; Metalloenzymes ; Dinucleating ligands ; Transition metals ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Awareness of the asymmetric nature of numerous dinuclear metallobiosites and of the ability of the individual metal ions to have quite distinct roles in the functioning of the metalloenzyme concerned has led to a search for carefully designed unsymmetric dinucleating ligands that will give dinuclear complexes capable of acting as models for the metallobiosites. This review surveys progress made in the design and synthesis of complexes capable of serving as models for donor atom, coordination number and geometric asymmetries found at dinuclear metal centres.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300402
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    Chemie polyfunktioneller Moleküle, 125Part 124: Ref. Synthese und Kristallstruktur von N,N,N′,N“,N-Pentamethyl-diethylentriamin-cokoordiniertem Kalium-bis(diphenylphosphanyl)amidHerrn Prof. Dr. Gerhard Herberich zum 60. Geburtstage gewidmet. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 141-144 
    Details
    ISSN: 0009-2940
    Keywords: Alkali metal organophosphanylamide ; Carbon-potassium bonding ; Phosphazane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metalation of bis(diphenylphosphanyl)amine [HN-(PPh2)2,1 with KOtBu at 95°C in toluene affords a pale yellow precipitate of potassium bis(diphenylphosphanyl)amide (3a). On addition of liquid N,N,N′,N“,N“-pentamethyldiethylenetriamine (PMDTA, 4) the precipitate dissolves in toluene at 115°C to give a yellow solution, from which yellow-green blocks of [(Ph2P)2NK·PMDTA] (3b) are obtained. X-ray analysis reveals that the coordination sphere of potassium consists of the chelating triamine ligand and [N(PPh2)2]- as N-donor as well as η1 and η2 C-donor with two phenyl fragments. No phosphorus coordination of [N(PPh2)2]- is observed.
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    Organophosphorus Compounds, 114. Tetracyclic Phosphorus-Aluminium-Carbon Compounds - Synthesis by Cooligomerization of Kinetically Stabilized Phosphaalkynes with Trialkylaluminium CompoundsDedicated to Professor Michael Hanack on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 255-259 
    Details
    ISSN: 0009-2940
    Keywords: Phosphaalkynes ; Triorganoaluminium compounds ; Cooligomerization ; Cage compounds ; Aluminium compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When the trialkylaluminium reagents 5 are allowed to react with phosphaalkynes 4 in n-pentane, a highly selective phosphaalkyne cyclotrimerization with incorporation of two organometallic units occurs (→ 6). The tetracyclooctane derivatives 6a-e represent the first examples of phosphorus-aluminium-carbon cage compounds. The polycyclic products 6 are able to function as ligands in transition-metal complexes (→ 7), which is illustrated by the reactions of 6b, c with nonacarbonyldiiron and pentacarbonyl(tetrahydrofuran)tungsten, respectively.
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    URL: http://dx.doi.org/10.1002/cber.19971300219
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    On the Ligating Properties of Sulfonate and Perchlorate Anions Towards Zinc (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 283-289 
    Details
    ISSN: 0009-2940
    Keywords: Zinc ; Sulfonate ligands ; Perchlorates ; Coordination modes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempts are reported to incorporate sulfonate and perchlorate anions as ligands in zinc complexes of tripodal ligands. Using tris(benzimidazolylmethyl)amine (BIMA) only the aqua complexes [ (BIMA)Zn-OH2](RSO3)(ClO4) and [(BIMA)Zn-OH2](RSO3)2(R=CH3, CF3, p-tolyl) were accessible. Using substituted pyrazolylborates (Tp*), the same three sulfonate anions were found to be ligands in the complexes Tp*Zn-OSO2R. Spectroscopic evidence for perchlorate coordination in Tp*ZnClO4 · 2 DMSO conflicts with crystallograpic evidence against it in Tp*ZnClO4 · pyridine. The crystal structures of [(BIMA)Zn-OH2](CH3SO3)2, TpCum,MeZn-OS02CH3, TPtBu,MeZn-OSO2C6H4-p-CH3, and [TpCum,MeZn · NC5H5]ClO4 were determined.
    Additional Material: 4 Ill.
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    Multiple Bonds Between Main-Group Elements and Transition Metals, CLXIV. Alkylrhenium(VI) Oxides-Synthesis and Characterization (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 295-298 
    Details
    ISSN: 0009-2940
    Keywords: Rhenium ; Oxides ; Alkyl ligands ; Dirhenium compounds ; Metal-metal interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Most alkylrhenium(VII) oxides, e.g. ((cyclo)-C3H5)Re03 (2) are rather sensitive to temperature and moisture with the prominent exception of methyltrioxorhenium (1). The corresponding alkylrhenium(VI) oxides of formula [RR′(O)- Re(μ-O)]2 [R=R′=(cyclo)-C3H5 (3), iPr (4); R=CH3, R′=C2H5 (5), R=CH3, R′=iPr (6)] are much more stable in this regard. They can be handled in air at room temperature. They were synthesized from Re207 and dialkylzinc precursors, fully characterized and are available in much higher yields than their ReVII congeners. Mixed tetraalkyltetraoxodirhenium(VI) complexes (R # R′) synthesized from 1 and dialkylzinc compounds form as a mixture of cis/trans isomers. They are oily liquids at room temperature. The Re=O and Re-Re stretching force constants as a measure of the bond strengths, were determined from IR and Raman data.
    Additional Material: 3 Tab.
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    Hydroxy- and Carboxy-Substituted Allylsilanes: A Simple and Stereoselective Method of Preparation (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 335-340 
    Details
    ISSN: 0009-2940
    Keywords: Allylsilanes ; Superbases ; Metalations ; Stereoselectivity ; Cyclizations ; Silicon ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When treated with two equivalents of a butyllithium/potassium tert-butoxide mixture, terminal olefins carrying unprotected hydroxy or carboxy groups generate allylmetal intermediates which can be trapped with chlorotrimethylsilane to afford functionalized (Z)-2-alkenyltrimethylsilanes. One equivalent of the superbasic reagent suffices if the unsaturated alcohols are first protected as acetals before being subjected to the metalation/silylation/hydrolysis sequence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300306
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    Preparation, Properties, and Reactions, of Metal-Containing Heterocycles, XCVIPart XCV: E. Lindner, E. Bosch, R. Fawzi, M. Steimann, H.A. Mayer, K. Gierling, Chem. Ber. 1996, 129, 945-951.. Mono-, Di- and Trinuclear Metallacycloalkanes of the Iron-TriadDedicated to Professor Wolfgang Beck on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 347-356 
    Details
    ISSN: 0009-2940
    Keywords: Metallacycloalkanes ; Metallacycloalkenes ; Osmium ; Iron ; Cyclic ketones ; Metallacycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the bis(triflates) [F3CSO3-(CH)m-O3SCF3] [m = 5-10, 12, 14, 16 (1a-i) with Na2[Os(CO)4] in dimethyl either affords the osmacycloalkanes 2a, 2b and 2f-i (m = 5, 6, 10, 12, 14, 16), diosmacycloalkanes 3a-i (m = 5-10, 12, 14, 16), and triosmacycloalkanes 4a-i (m = 5-10, 12, 14, 16). The structure of 3f was investigated by an X-ray structural analysis. This 22-membered disomacycle crystallizes in the space group Pā with Z = 1. If the unsaturated cis-4-octen-1,8-diyl bis(trifluoromethanesulfonate) (5) is treated with Na2[Os(CO)4] the diosmacyclooctadeca-5,14-diene 6 is obtained. By treating the bis(triflates) 1a, b with Na2[Fe(CO)4] the corresponding ferracycloalkanes are formed only in situ. Insertion of carbon monoxide into the M-C σ bonds leads to the cyclic ketones 7a, d and to the diketone 8d.
    Additional Material: 4 Ill.
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    Enantioselective Catalysis, XIIIPart XII: U. Nagel, J. Leipold, Chem. Ber., 1996, 129815-821.. Preparative and Structural Chemistry of Chiral 3-(Diphenylphosphanyl)-pyrrolidiens and Their Palladium(II) Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 385-398 
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    ISSN: 0009-2940
    Keywords: Pyrrolidinephosphanes ; 3-Hydroxypyrrolidine ; 3-Diphenylphosphanylpyronlidine ; Salt effects ; Polymorphism ; Homogeneous catalysis ; Palladium ; Asymmetric catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of both enantiomers of 3-diphenylphosphanulpyrrolidiine (2) and several N-substituted derivatives together with two PdIi complexes of this ligand is reported. Form L-malic acid and L-hydroxyproline both enantiomers of 3-hydroxypyrrolidine are prepared without any problems due to epimerization. KPPh2 in the presence of LiCl is shown to be the most effective reagent for the synthesis of 2. The reported X-ray structure determination sof Pdl2 complexes show a rather rigid bicyclic hetero-norbornane skeleton. The flexibility of the other parts of the molecules is obvious in several polymorphs revealed by this method. This polymorphism is additionally investigated by a 31P-CP-MAS study. From solution 1-, 13C- and 31P-NMR studies it is concluded that the bicyclic hetero-norbornane skeleton is retained in solution.
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    Reactions of Silicon-Silicon Bonds, VIFor part V, see ref.[1].. Reductive Trichloroslilylation Reactions Leading to Alkyl- and Dialkylaminobis(trichlorosilyl)phosphanesDedicated to Professor Walter Siebert on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 377-384 
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    ISSN: 0009-2940
    Keywords: Trichlorosilylation ; Dichlorophosphanes ; Silylphosphanes ; Amino(silyl)phosphanes ; Silicon /Reductions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of hexachlorodisilane and of trichlorosilane/triethylamine with alkyl-and dialkylaminodichlorophosphanes RPCl2 1a-i [R = iPr: a; (Me3Si)2CH: b; R=1-adamantly: c: R=tBu: d; R=Et2N: e; R=iPr2M: f] furnish bis(trichlorosilyl)-phosphanes RP(SiCl3)2 3a-f. However, when less bulky substituents are attached to the phosphorus atom, so that there is little steric crowding, the double reductive silylations leading from 1 to 3 are accompanied by side reactions and decomposition of 3. Therefore, only 3b, 3c, 3d, and 3f wre isolated in a pure state. These compounds are more readily prepared by the; trichlorosilane/triethylamine method. 1H-, 31P- and 29Si-Nmr spectra confirm their constitution. The structure of solid 3f, the first aminobis(trichlorosilyl)phosphane, was determined by X-ray crystallography. 3f contains a phosphorus atom in a pyramidal environment surrounded by two silicon atoms and a planar nitrogen atom of the diisopropylamino group.
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    Formation of the Digallium Compound [(C5C6)2N3](R)Ga-Ga(R)[N3(C6H5)2] with Two Bis(trimethylsilyl)methyl Groups and Two Terminal Chelating Diphenyltriazenido Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 417-420 
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    ISSN: 0009-2940
    Keywords: Gallium ; Low-valent compounds ; Gallium-gallium bond ; Terminal triphenytriazenido ligand ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrakis[bis(trimethylsilyl)methyl]digallane (4) 1 reacts with 1,3-diphenyltriazene to yield two compounds, which were both characterized by a crystal structure determination. The gallium-gallium bond is retained in the yellow derivate [(H5C6)2N3](R)Ga-Ga(R)[N3(C6H5)2 2 [R = CH(SiMe3)2], which is formed by a ligand exchange reaction and shows two terminal chelating triazenido ligands besides two bis(trimethylsilyl)methyl groups; the Ga—Ga bond length is 245.79(6) pm. The second product is the orange dialkyl(diphenyltriazenido)gallium derivative R2Ga[N3(C6H5)2] 3, where the triazene has reacted as an oxidant by the cleavage of the Ga—Ga bond and probably by release of elemental hydrogen.
    Additional Material: 2 Ill.
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    The Electronic Structure of [Te15Br4][MoOBr4]2 and Some General Aspects of Bonding in “Classical” and Hypervalent Tellurium Halides (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 463-472 
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    ISSN: 0009-2940
    Keywords: Hypervalent compounds ; Tellurium ; Polycations ; Molecular Orbital Theory ; Band structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Approximate MO and band structure calculation are used to analyze the bonding in the recently synthesized paramagnetic, semiconducting phase [Te15Br4]2+. The [Te15Br4]2+ chains are very similar to those in the tellurium subhalide Te2Br. The electronic structure and bonding within these chains is analysed and the possibility of hypervalency in both [Te15Br4][MoOBr4]2 and Te2Br is discussed. The bonding in the classically hypervalent molecule TeBr42- and a model Te3Br24- is compared to that of the infinite system. Our calculations indicate that both [Te15Br4][MoOBr4]2 and Te2Br contain weakly hypervalent Te atoms and that the interesting electronic properties of [Te15Br4][MoOBr4]2 arise within the distinct sublattices, which do not interact significantly.
    Additional Material: 12 Ill.
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    Heterobimetallic Complexes with a Propynylidene C3-Bridge: General Synthetic Routes to Bimetallic Ethynylcarbene Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 479-488 
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    ISSN: 0009-2940
    Keywords: Heterobimetallic complexes ; Carbene complexes ; Alkynes ; Coupling reaction ; Bridging ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sequential reaction of the dimethylamino(trimethylsilylethylnyl)carbene complexes [(CO)5M'=C(NMe2)C≡CSiMe3] [M' = W (1a)] with KF/THFMeOH, nBuLi and transition metal halides, [XMLn], affords heterobimetallic propynyliden complexes of the type [(CO)5M'=C(N-Me2)C≡CMLn] [MLn = Ni(PPh3) Cp (4a, b). Ni(PMe2Ph)2- {Mes) (Mes=2,4,6-C6H2Me3) (5a), Rh(CO)(PPh3)2 (6a), Fe(CO)2Cp (7a,b)]. In contrast, reaction of 1a with MeLi · LiBr and [IFe(CO)2Cp] yields the novel N-metallated complex [(CO)5W=C{N(ME)Fe(CO)2Cp}C≡CSiMe3] (8a). The complexes [(CO)5M'=C(NMe2)C≡CMLn=Fe(CO)2Cp (7a, b), Ru(CO)2Cp (10a,b), Ru(CO)(PPh3)Cp (11a), Mn(CO)5 (12a), Re(CO)5 (13a)] are accessible by Pd-catalyzed coupling of the C-stannylated carbene complexes [(CO)5M'=C-(NMe2)C≡CSnBu3] (9a, b) with [XMLn]. The related monomethylaminocarbene complexes [(CO)5M'=C(NHMe)C≡ CSnBu3] (16a, b), obtained by stannylation of [(C))5M'=C(NHMe)C=CH] (15a, B) with Bu3SnNEt2, react with [IFe(CO)2Cp] to give the bimetallic complexes [(CO)5M'=C(NHMe)C≡CFe(CO)2Cp] (17a, b). The complexes 4a, 5a, 7a and 10a were characterized by X-ray structural analysis. The spectroscopic and structural data suggest that the two metal centers in 4-7, 10-13, and 17 interact only weakly.
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    Synthesis and Molecular Structure of a Rhenium Complex Derived from 8a-Amino-6-methyl-ergolineDedicated to Professor Roland Mayer on the occasion of his 70th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 839-841 
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    ISSN: 0009-2940
    Keywords: Rhenium ; Technetium ; 8a-Amino-6-methyl-ergoline ; Chelates ; Structure elucidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Current research in radiopharmaceutical chemistry is aimed at the design of technetium-based receptor-binding radiotracers because of the excellent nuclide properties of the isotope 99mTc. Tc tracers and the corresponding complexes of rhenium, as the inactive surrogate of Tc, are required to imitate organic agonists or antagonists of the receptor. We have started studies with ergolines, which are known to be dopamine substitutes. The present report deals with the functionalization of 8α-amino-6-methyl-ergoline (2) with a 2-mercaptoacetyl group, and the subsequent synthesis of the first rhenium complex containing a pendent ergoline moiety [Re- O(SSS)(RS)] (HSSSH = HS-CH2CH2-S-CH2CH2-SH and RSH = 8a-amino-N-(2-mercaptoacetyl)-6-methyl-ergoline) (4). The molecular structure of the rhenium complex was determined by X-ray crystal structure analysis.
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    Aminotroponimines as Ligands for Yttrium and Lanthanide Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 859-862 
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    ISSN: 0009-2940
    Keywords: Yttrium ; Lanthanum ; Samarium ; Lanthanides ; Aminotroponiminate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of N-isopropyl-2-(isopropylamino)troponimine, [(i-Pr)2ATI]H, with KH in THF affords [(i-Pr)2ATI]K. This is a useful starting material for the preparation of the mono-, bis- and tris-substituted compounds [[i-Pr)2ATI]YCl2-(THF)2}2, [(i-Pr)2ATI2Y[O(2,6,t-Bu2C6H3)] and [(i-Pr)2-ATI]3Ln (Ln = Y, La, Sm), which can be obtained from ([i-Pr)2ATI]K and LnX3 and LnX3 (X = Cl, I), or Y[O(2,6-t-BuC6H3)]3. All compounds have been characterized by spectroscopic methods. The monosubstituted yttrium complex {[(i-Pr)2ATI]YCl2(THF)2}2 has also been investigated by single crystal X-ray diffraction.
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    C-H Bond Activation of Simple Alkenes with (C5H5)CO Fragments: Preparation, Molecular Structure, and Dynamical Behaviour of Tri- and Tetranuclear Cyclopentadienylcobalt Cluster complexes with μ-Cycloalkyne Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 593-603 
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    ISSN: 0009-2940
    Keywords: C-H activation ; Alkyne complexes ; Cyclopentadienyl cobalt ; Fluxionality ; Hydrido complexes ; Clusters ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vicinal C-H bonds of the cycloalkenes CnH2n (n = 5-8) were activated upon treatment under mild conditions with reactive sources of the (C5H5)CO fragment. With [C5H5)CO(C2H4)2] (2a), the trinuclear cluster complexes [H2((C5H5)CO)3(μ3-C2(CH2)n-2)] (5a: n = 5; 5c: n = 5d: n = 8) were formed. Using the more reactive [(C5H5)2Co]/K, 5a-5dwere obtained, along with small amounts of the tetranuclear [{(C5H5)CO}4r{μ4-C2(CH2)n-2}] (8a-c: n = 5-7). X-ray structure analyses of 5c, d and 8b, c were performed. A μ-‖ (orμ3-η1:η2:η1) coordination of the cycloalkyne ligands was found in the trinuclear cluster complexes. The tetranuclear 8b, c had the cycloalkynes quadruply bridging (μ4-η1:η2:η2:η1_ a butterfly arrangement of the metal atoms. The acetylenic carbon-carbon bonds are considerably lengthened upon coordination [1.392(4), 1.398(3) å in 5c d; 1.464(8), 1.499(5) Å in 8b, c]. Three dynamic processes - alkyne “walk” on top of the CO3 triangle, μ2-hydride migration, and μ2/μ3-hydride exchange - are operational in the trinuclear 5a-d. Dynamic NMR data for 5a are consistent with a “windshield-wiper” mechanism for the alkyne migration. Hydride exchange is associated with a higher energy barrier, and is probably and independent dynamic process.
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    Organoamido- and Aryloxolanthanoids, 15Part 14: Ref. [1a].. Organometallic Compounds of the Lanthanoids, 116Part 115: Ref. [1b].. Syntheses of Low Coordination Number Divalent Lanthanoid Organoamide Complexes, and the X-ray Crystal Structures of Bis[(N-2,6-diisopropylphenyl)(N-trimethylsilyl)amido]bi(tetrahydrofuran)samarium(II)and -ytterbium(II) (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 409-415 
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    ISSN: 0009-2940
    Keywords: Mercury ; Lanthanides ; Lanthanoid(II) complexes ; (N-2,6-Diisopropylphenyl)(N-trimethylsily)amide complexes ; Bis(trimethylsilyl)amide complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Mercury(II) amide complex Hg[N(SiMe3)(2,6-iPr2C6H3)]2 (1) was prepared by reaction of HgBr2 with Li[N(SiMe3) 2,6-iPr2C6H3)] in diethyl ether solvent. Redox transmetallation reactions of 1 with elemental samarium, europium or ytterbium in THF solvent (THF = tetrahydrofuran), generated the novel divalent complexes Ln[N(SiMe3)(2,6-iPr2C6H3]2(THF)2 with Ln = Sm (2), Eu (3) and Yb (4). 4 was also synthesized by reaction of elemental ytterbium, HgPh2 and HN(SiMe3)(2,6-Me3)2]2(THF)2 [Ln = Sm (5), Yb (6)] by reaction of the metals with HgPh2 and HN(SiMe3)2. Thermal desolvation of 4 under high vacuum gave Yb(N)(SiMe3)2,6-iPr2C6H3)]2 (THF) (7), whereas under identical conditions 6 yielded the solvent-free complex [Yb[N{SiMe3)2]2]2. (8). The new compounds 1-4 and 7 are hydrocarbon soluble and 171Yb-NMR spectra were recorded for 4, 6, 7 and 8. X-ray crystal structure determinations of 2 and 4 revealed four-coordinate, distorted tetrahedral metal environments augmented by weak Ln…ipso-C(aryl) interactions.
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    Synthesis and Structure of 2,2′ -Boryl-, Germyl-Silyl-, and Stannyl-Substituted 1,1′ -Binaphthyl SystemsDedicated to Professor Hans Paulsen on the occasion of his 75th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 923-932 
    Details
    ISSN: 0009-2940
    Keywords: Biaryls ; Boron ; Chirality ; Cooperative Effects ; Lewis acids ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of Lewis acid binaphthyl systems, substituted in 2-or 2,2′-position, are synthesized by lithiation of 2,2′-dibromo-1,l ′-binaphthyl (5), followed by addition of various electrophiles. Stepwise lithiation and subsequent borylation with trimethyl borate leads to the bromoboronic acid 6, which can be stabilized by esterification with pinacol giving 7. By increasing the reaction mixture to 2 equiv. of n-butyllithium and 2 equiv. of methyl borate the path to the binaphthylmonoboronic acid ester 9 is opened up. A further increase in the quantity of electrophile also leads to the binaphthylbisboronic acid ester 12. The 2,2′-disubstituted silyl, germyl, and stannyl derivatives 13a-15a are accessible in good yields. Treatment with boron halides leads exclusively to methyl/halogen exchange, giving the bidentate Lewis acids 13b-15b, the former of which can be bridged by oxygen.Only in case of the bis(tributylstannyl)binaphthyl 16a does ipso substitution occur in the presence of boron trichloride, giving the bis(dichloroboryl)-substituted binaphthyl 16b which can then be hydrolysed to 11. The structures of the majority of the compounds were investigated by X-ray diffraction. In case of the 2,2′-disubstituted compounds 13a-15a the naphthyl groups are orientated perpendicular to each other. The intra- and intermolecular interactions are dominated by this binaphthyl system. In case of the oxygenbridged compounds 13c and 14c the angle between the naphthyl planes decreases to about 70°. This also has an effect on the packing of the molecule; in this instance the orientation of two naphthyl in neighbouring molecules is nearly parallel. The structure of the diboronic acid is dominated by intra- and intermolecular hydrogen bonding.
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    Temperature-dependent Ring-Opening and -Closure of a Cyclic Phosphane-BoraneDedicated to Professor Gottfried Huttner on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 951-954 
    Details
    ISSN: 0009-2940
    Keywords: Phosphane-boranes ; Medium-sized rings ; Ring opening and closure ; Temperature-dependent NMR studies ; Phosphorus ; Boron ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A phosphane-borane (3) with the P-B bond integrated into a seven-membered ring was prepared from 4-pentenyl-diphenylphosphane (4) by hydroboration using 9-borabicyclononane (9-BBN). The product was confirmed to have a ring structure in the solid state by single crystal X-ray diffraction. The P-B distance of 2.057(2) Å is indicative of a standard donor-acceptor bond similar to the type found in homologous five- and six-membered rings. The room-temperature 31P-NMR signal of the compound in various solvents (δ ≈ - 15) is not compatible with the cyclic structure and suggests that ring opening occurs as the compound is dissolved. Variable-temperature NMR work corroborated this assumption, and the enthalpy of ring closure was determined to be ΔH = -30.5(4) kJmol-l. In CD2C12 at -90°C, δ31P is shifted to +3.5 ppm to low field, suggesting virtually complete ring closure under these conditions.
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    The Coordination Chemistry of Fluorocarbons: Group-I and Group- II Metal Ion Complexes of Fluoro Macrocycles (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 963-968 
    Details
    ISSN: 0009-2940
    Keywords: Fluorine ; Macrocycles ; Complexes ; Sodium ; Barium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new fluoro macrocycles BenzoFN2O3 and F(N2O2)2C2H4 were synthesized in the reactions of 1,3-bis(bromomethyl)-2-fluorobenzene with benzo-diaza-15-crown-5 and 1,2-bis(diaza-12-crown-4)ethane, respectively, in 30% yield each. Close CF...metal ion interactions in the respective alkaline metal complexes in solution are evidenced by characteristic shifts of the 19F-NMR resonances of up to δ = 18.7 relative to the free ligand and by a decrease of the 1J(CF) coupling constant of up to 20 Hz, which is most pronounced in BenzoFN2O3 · Li+ and F(N2O2)2C2H4 · K+. In BenzoFN2O3· Li+ a1J(19F-7Li) of 15.5 Hz was observed, which is indicative very close CF...Li+ interactions in solution. In the X-ray crystal structures of BenzoFN2O3 · Na+ [CF⃛Na+ 246.8(2) pm], 26-fluoro-4,7,13,16-tetraoxa-1, 10-diazatricyclo[ 8.8.7.1 20,24 ] - hexacosa-20,22,24(26)triene · Na+ (CF⃛Na+ 267.1(2) pm) and 21 -fluoro-3,6,9,12,15,18-hexaoxabicyclo[ 18.3.1 1,20]heneicosa- l(24),20,22-triene. Ba2+ [CF⃛Ba2+ 299.0(3) pm] short CF⃛metal interactions were found. Such close CF⃛metal ion interactions do not result in a lengthening of the C-F bonds, which is not a sign of weak CF⃛metal ion interactions, since a Cambridge Structural Database search revealed that a shortening of the C-O bond length is also not observed in crown ether complexes of alkaline metals.
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    Organophosphorus Compounds, 118Part 2: 117: Ref1. Reactions of 1-Chloro-1H-phosphirenes with Nucleophiles (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 711-723 
    Details
    ISSN: 0009-2940
    Keywords: Phosphorus heterocycles ; 1H-Phosphirenes ; Nucleophilic substitution reactions at 1H-phosphirenes ; Metal-complexation of functionalized 1H-phosphirenes ; Carbonyl complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The halogen atoms in the 1-chloro-1H-phosphirenes, 5a-c, are easily substituted on reaction with organolithium and Grignard reagents, 14a-p, with formation of the corresponding O-, N-, C-, Si-, and Ge-substituted 1H-phosphirenes, 15a-t. C1/H exchange reactions also occur on reaction with lithium metal hydrides (5a → 17). Furthermore, substitution reactions are also realized with the alkali metal borates, 18a-g (→19a-g); the same is true for reactions with trimethylsilyl cyanide and azide (→22a-d). Some of the substitution products have been characterized in the form of their metal complexes, 16, 23, 24, and 25.
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    Synthesis of Germatranyl Derivatives of Esters of Carboxylic Acids via Organometallic (Si, Ge, Sn) Reagents (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 739-746 
    Details
    ISSN: 0009-2940
    Keywords: Germatranes ; Organotrihalogenogermanes ; Organometallic (Si, Ge, Sn) reagents ; Transmetallation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trialkylstannyl esters of tris(2-hydroxyalkyl)amines, N(CH2CHROSnAlk3)3 (9-11 (R = H, Me; Alk = Et, Bu), react with X3GeC(R1)(R2)COOR3 (12-17) (X = Cl or Br; R1, R2=H, Me, Ph, SiMe3, COOEt; R3=Me, Et) to give esters of α-germatranylcarboxylic acids, N(CH2CHRO)3GeC(R1)(R2)-COOR3 (1-8), in high yields. The synthesis of esters 12-17 is reported. Esters of α-germatranyldiphenylacetic acid 24 and 25 can be obtained by treatment of diphenylketene with Et3SnOMe to give in situ Et3SnC(Ph2)COOMe (23), followed by reaction with GeCl4 to give in situ Cl3GeC(Ph2)COOMe (22 and further reactions with 9 or 11, respectively. Reduction of germatrane 6 with LiAlH4 in diethyl ether leads to cleavage of the germanium-carbon bond with subsequent formation of (2-hydroxyethyl)trimethylsilane. The crystal structures of 3, 6 and 7 are reported. 1-Acyloxygermatranes 26 and 27 are obtained by treatment of 1-methoxygermatrane (28) with diphenyl- and dichloroacetic acid, respectively.
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    Base-Induced Synthesis of a Tetrastannatriazabicyclo[3.1.1]heptane from Tris)dimethylchlorostannyl)amineDedicated to Professor W. Sieber on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 765-769 
    Details
    ISSN: 0009-2940
    Keywords: Tin - Nitrogen cage compounds ; Sn—X—Sn intramolecular bridges ; Distannylamine pyridine adduct ; Tin ; Moessbauer spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(dimethylchlorostannyl)amine (2a) reacts with pyridine in a 3:4 molar ratio to produce the tin-nitrogen containing bicyclo[3.1.1]heptane (3) with elimination of the adduct Me2SnCl2·2 py. Treatment of the distannylamine 2,6-[Pr2H3N(SnMe2Cl)2 (4) with pyridine, however, leads to the formation of the 1:1 pyridine adduct 4 and this can be regarded as a model to explain the route to 3. The molecular structures of 3 and 5 were determined by multinuclear magnetic resonance spectroscopy in solution, as well as by X-ray structure analysis of their crystals. Typical structural features for both compounds are intramolecular Sn—X—Sn bridges. Support for the structures comes from MS fragmentation patterns, IR spectra, and the Mössbauer spectra.
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    Thermal Reactions of 5-Alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-Phosphapyrazolines) - A Route to Various P—Heterocycles and to 2-PhosphabutadienesDedicated to Professor M. Hanack on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 779-788 
    Details
    ISSN: 0009-2940
    Keywords: 1,2,4-Diazaphospholes ; Phosphiranes, alkylidene- ; 2-Phosphabutadienes ; Phosphorus heterocycles ; pyrazolines, thermolysis ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 5-alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-phosphapyrazolines) are thermally much more stable than related compounds without the exocyclic double bond. Thermolysis reactions typically occur in the range 110-150°C in toluene solution, and different, mostly competing, reaction pathways are observed. Thermal extrusion of nitrogen from 8a-g gives rise to β-phosphanaylsiloxyalkenes 10, benzo[c]-phosphole derivatives 11, 14 and 115, (β-siloxyalkylidene)-Phosphiranes 12, and dihydro-1,3-oxaphospholes 13. The thermolysis of 5-alkylidene-4,5-dihydro-4-trimethylsilyl-3-trimethylsilyloxy-3H-1,2,4-dizaphospholes 17 afforded three products, including the highly substituted and stable 2-phosphabutadienes 18 formed by nitrogen extrusion and rearrangement. Finally, the 4-chloro-3-trimethylsilyloxy-substituted heterocycle 21 was transformed at 170°C into 4H-1,2,4-diazaphosphole 23. The structures of 13c and 18a were determined by single-crystal X-ray diffraction.
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    Reaction of 1,3-Dialkyl-4,5-dimethylimidazol-2-ylidenes with 2-Bromo-2,3-dihydro-1H-1,3,2-diazaboroles (Alkyl=iPr and tBu)Dedicated to professor Adolf Zschunke on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 705-710 
    Details
    ISSN: 0009-2940
    Keywords: Boron ; Diazaboroles ; Carbenes ; Heterocycles ; Imidazoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Bromo-2,3-dihydro-1H-1,3,2-diazaboroles (3a-c) were synthesized by cyclocondensation of dilithiated 1,4-diazabutadienes (5a-c) with boron tribromide in hexane. 3a was also obtained by sodium amalgam reduction was conducted in ether solvents, diboroxane (2) resulted as the main product. Compound 3a and 1,3-dialkyl-4,5-dimethylimidazol2-ylidenes (6a, b) underwent halide displacement to afford the borolylimidazolium salts 7a, b. Compounds 2, 3a-c, and 7a, b were characterized by elemental analyses and spectroscopic methods (1H, 11B, 13C NMR; Ir; MS). The molecular structures of 2 and 7a were established by single-crystal X-ray diffraction analyses.
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    Well-Defined Metallodendrimers by Site-Specific Complexation (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 725-728 
    Details
    ISSN: 0009-2940
    Keywords: Dendrimers ; Metal complexes ; Nanostructures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Strong multiple complexation of transition metal ions, Cu(II), Zn(II) and Ni(II) with different generations of well-defined poly(propylene imine) dendrimers as multi(tridentate) ligands has been used to construct nanoscopic assemblies of defined structure and size incorporating a distinct number of metal ions from 2 up to 32.
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    Compounds of Germanium and Tin, 2lPart 20: Ref.[1]. A Tetraaryldigermene with a Short Germanium-Germanium Double Bond and a Nearly Planar Environment of Both Germanium AtomsDedicated to Professor Hans Bürger on the occasion of his 6oth birthday (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 735-738 
    Details
    ISSN: 0009-2940
    Keywords: Germanium ; Digermenes ; Tin ; Germylenes ; Stannylenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of GeCl2 · dioxane with the Grignard reagent RMgBr (R=2-tBu-4,5,6-Me3C6H) furnishes the tetraaryldigermene R2Ge=GeR2 (8). X-ray structure-analysis of 8 reveals a short Ge=Ge double bond, a nearly planar environment of both germanium atoms and extremely widened C—Ge—C angles of 128°. In solution, 8 dissociates into two germylene molecules R2Ge, which can be trapped with oxygen or by [4+1] cycloaddition reactions with 1,4-dihetero-1,3-dienes. A similar cycloadduct of a stannylene wa obtained by thermolysis of (R′2Sn)3 (R′=2,4,6-iPr3C6H2), in the presence of a 1,4-diazabutadiene and characterized by an X-ray structure-analysis.
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    Synthesis and Crystal Structure of tert-Butylamino)di-tert-butyl)siliceniotrichloroaluminate, (Me3C)2Si=NCMe3·AlCl3, and Dimethylazomethine-Aluminium Trichloride, Me2C=NH·AlCl3Dedicated to Prof. A. Meller on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 753-755 
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    ISSN: 0009-2940
    Keywords: Silicenium ion ; Iminosilane ; Aluminate ; Silicon ; Aluminium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithiated text-butylaminolfluorosilanes react with aluminum trichloride in ether, eliminating LiF to give AlCl3 adducts of iminosilanes  -  aminosiliceniotrichloroaluminates {R2Si-NCMe3·AlCl3}, which thermally form the dimethylazomethine- aluminium trichloride, Me2C=NH·AlCl3.
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    Sulfur Compounds, 199Part 198: R. Steudel, Y Drozdova, K. Miaskiewicz, R. H. Hertwig, W. Koch, J Am. Chem. Soc. 1997, 119, 1990.. Novel Titanocene Thiolato Complexes and Their Application in Preparing New Sulfur-Containing Heterocycles (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 757-764 
    Details
    ISSN: 0009-2940
    Keywords: Titanocene complexes ; S ligands ; Organic polysulfanes ; Ligand transfer reactions ; Sulfur heterocycles ; Chalcogens ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of Cp2Ti(CO)2 (3) with the di- and polysulfanes 1,2,4-(CH2)2S3, C4S6 (9), C,7H10S3 (11), 1,2,4,6-(CH2)3S4 (16), C6H10S6(19), and S6 affords the titanocene chelate complexes Cp2TiS3(CH2)2 (8), (Cp2Ti)2C4S6 (10), Cp2TiS3C7H10 (13), Cp2TiS2C7H10 (14), Cp2TiS4(CH2)3 (17), Cp,2TiS6C6H6H10 (20), and Cp2TiS8 (23). 14 is also obtained from Cp2TiCl2 (1) and the geminal dithiol of norbornene. The analogous reaction with the dithiol of dicyclopentadiene yields Cp2TiS2C10H12 (15). In ligand transfer reactions, 8 reacts with SCl2 to give 1,2,3,5-tetrathiane (25), 10 provides 9 on reaction with Cl2, 13 when treated with S2Cl2 affords C7H10S5 (12), 15 reacts with S2Cl2Cl2 to give C10H12S4. 17 and SCl2 yield 1,2,3,5,7-pentathiepane (18), 20 is converted to C6H10S7 (22) on reaction with SCl2, and 23 yields S10 and 1,2,-C6H4(SCl)2, respectively. With phosgene, thiophosgene, and thionyl chloride, compound 15 yields the corresponding dithiocarbonate 26, the trithiocarbonate 27 and the trisulfane 2-oxide 28. The structure of 27 was determined by X-ray crystallography.
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    Synthesis of a Bisdienophilic Phthalocyanine and of Precursors for Repetitive Diels-Alder Reactions Based on Hemiporphyrazines and Phthalocyanines (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 801-806 
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    ISSN: 0009-2940
    Keywords: Unsymmetrical phthalocyanines ; Hemiporphyrazines ; Macrocyclic bisdienes and bisdienophiles ; Diels-Alder reactions ; Ladder polymers ; Cycloaddition ; Macrocycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The specific synthesis of a metal-free bisdienophilic phthalocyanine 193, suitable for repetitive Diels-Alder reactions, is reported. This was achieved by condensation of 191,3,3-trichloro-6/7-nitroioindolenine (191) and 4,9-dibutoxy-2,3,5,8-tetrahydro-1,3-diimino-1H-5,8-epoxybenz[f]isoindoline (2). The ability of 3 to undergo Diels-Alder reactions was tested by reaction with an excess of 1,2,3,4-tetraphenylcyclopentadienone (5). Experimental data of the hemiporphyrazines 9, 10, and 11, which can be used as precursors for the synthesis of ladder polymers, are also given in the Experimental Section.
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    Pseudoelement Compounds, XPart IX: Ref. Synthesis and Crystal Structure of New Complexes of the Type trans-[Pt(H)X(PPh3)2 with Cyanamide and Cyanomethanide LigandsDedicated to Professor S. Engels on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1007-1012 
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    ISSN: 0009-2940
    Keywords: Platinum ; Nitrocyanamide ; Nitrosodicyanomethanide ; 1,1,3, 3-Tetracyano-2-azapropenide ; 1,1,2,3,3-Pentacyanopropenide ; Hydrido complexes ; Coordination modes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new coordination compounds trans-[Pt(H)X(PPh3)2] with NCN- and C(CN)2-functionalized anions (X- = [N(O)C(CN)2]-, [NO2NCN]-, [N{C(CN)2}2]-, [NCC{C-(CN)2}2]-, have been characterized by 1H-, 31P-, 13C-NMR, and IR spectroscopy and elemental analyses the crystal structures of trans-[Pt(H)N(O)C(CN)2(PPh3)2], trans- [Pt(H)N{C(CN)2}2(PPh3)2], and trans-[Pt(H)NCC{C(CN)2}2-(PPh3)2) have been determined by X-ray diffraction. Remarkably, [N(O)C(CN)2]- is coordinated through the central nitrogen atom, while [N{C(CN)2}2]- and [NCC(C(CN)2]2]- are bonded through terminal nitrogen atoms of a C(CN)2 unit.
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    New Coupling Reactions and Phosphorylations Using Organozinc Reagents (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1021-1027 
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    ISSN: 0009-2940
    Keywords: Zinc ; Chirality ; Cross-coupling ; Phosphorylations ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This Microreview on the chemistry of organozinc reagents starts by briefly showing the methods of preparation of organozinc compounds and then discusses the considerable synthetic utility of zinc organometallics for the formation of new carbon-carbon bonds in the presence of transition-metal catalysts. Finally, the use of organozinc chemistry for the preparation of polyfunctional and chiral phosphanes is described.
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    Synthesis and Structures of Bis(tetramethylipiperidino)aluminum Halides-X-ray Crystal Structures of tmp2AlX (X = Cl, Br, I) and [tmp2A1(μ-F)l2 (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1047-1052 
    Details
    ISSN: 0009-2940
    Keywords: Bis(tetramethylipiperidino)aluminum halides ; Alkoxy((tetramethylpiperidino)aluminum halides ; 27Al-NMR spectra ; Aluminum ; Amides ; Synthetic methods ; Bridging ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Lithio-2,2,6,6-tetramethylpiperidine [Li(tmp)] reacts with AlX3 (X = Cl, Br) in diethyl ether/ n-hexane solution to generate the products of substitution and ether cleavage, [tmpAl(X)(μ-OEt)], (la, X = Cl; 1b, X = Br). However, when the reaction is allowed to proceed in n-hexane alone, an almost quantitative yield of compounds tmp2AlX (2a, X = Cl; 2b, X = Br; 2c, X = I) is obtained. According to 27AI-NMR spectroscopy, mass spectroscopy, cryoscopy, and X-ray crystal structure determinations, these compounds are monomeric in the solid state, in solution, and in the gas phase. 2b reacts with AgBF4 yielding the fluoride-bridged dimer (tmp2AlF), 2d, as shown by X-ray crystal structure determination.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19971300805
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    Synthesis, Structure, and Dynamic Behavior of (μ-Aldimido)(μ-η1: η2-alkyne)- biszirconocene Cation Complexes That Contain Planar-Tetracoordinate Carbon (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1069-1077 
    Details
    ISSN: 0009-2940
    Keywords: Planar-tetracoordinate carbon ; Dynamic organometallic systems, μ-alkyne complexes ; π-Agostic systems ; Zirconium ; Metallocenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The benzonitrile hydrozirconation product Cp2ZrCl(N—CHPh) 8 was treated with propynyl lithium to yield the (propynyl)(benzaldimido)ZrCp; complex 9. Subsequent treatment with trityl tetraphenylborate generated [Cp2Zr(C—C—CH3)-BPh-4] that instantaneously added to 9 to eventually form the (μ-aldimido)(μ-η1:η2-hexadiyne)ZrCp2 cation 11. The X-ray crystal structure analysis showed that 11 contains a planar-tetracoordinate carbon atom that is stabilized by forming a three-center-two-electron bond with the two adjacent metal atoms. Similarly, complex 9 reacted with [Cp2Zr(CH3)+CH3B(C6F5)3 1 to yield the planar-tetracoordinate carbon containing (μ-aldimido)(μ-η1:η2-2-butyne) Cp; cation 12. Both complexes 11 and 12 exhibit dynamic NMR spectra due to their rapid reorganization of the dimetallabicyclic frameworks (ΔG* = 10 kcal mol-1) in addition to an anchimerically assisted C—N bond rotation (ΔG* =15 kcal mol-1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300808
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    Isolation and Characterization of a Porphinatomanganese(IV) Complex from the Reaction of Dichloro Monoxide with 5,10,15,20-Tetrakis-(2,6-dichloropheny)porphinatomanganese(III) Chloride [Mn(EDCPP)CI] (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1099-1103 
    Details
    ISSN: 0009-2940
    Keywords: Porphyrinatomanganese(IV) ; Monooxygenase model ; Dichloro monoxide ; Catalytic alkene epoxidation ; Catalytic alkane oxygenation ; Catalytic alkane chlorination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isolation at -78°C and characterization of the novel crystalline reactive porphinatomanganese(IV) complex Mn-(TDCPP)(OCl)2 (5) is described. 5 is compared with the porphinatomanganese(IV) complexes Mn(TDCPP)(C6H5IOCl)2 (2), Mn(TDCPP)(C6F510C1)CI (3) and Mn(TDCPP)(OCH3)2, (4). The stoichiometric reaction of 5 with triphenylphosphane yields 2.5 equivalents of triphenylphosphane oxide and 1.0 equivalent of Mn(TDCPP)Cl (1). Complex 5 epoxidizes stilbene, and oxygenates and chlorinates cyclohexane.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19971300811
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    Synthesis and Structure of Allenyl-Substituted η6-Benzene(tricarbonyl)-chromium Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1135-1139 
    Details
    ISSN: 0009-2940
    Keywords: Arene complexes ; Chromium ; Allenes ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Cr(CO)3-complexed η6-phenylpropargylic alcohols 3 react in a displacement rearrangement with thionyl chloride or chlorodiphenylphosphane to give the chloro- or phosphoryl allenyl substituted η6-phenyl complexes 4 and 6, respectively. In the X-ray crystal structure of the novel organometallic allenic derivatives 4b and 6b the vicinal chloro or phosphoryl substituent and the benzene(tricarbonyl)chromium fragment are arranged coplanarily. Palladium/copper-catalyzed couplings of the chloroallene 4b with terminal alkynes disclose a facile access to ynallene derivatives 8, novel carbon-rich organometallic π-systems.
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    URL: http://dx.doi.org/10.1002/cber.19971300816
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    Raman and Infrared Spectra and Quantum Chemical Calculations for Trichlorophosphoranylidenesulfamoyl Chloride, CISO2N=PCI3 (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1141-1145 
    Details
    ISSN: 0009-2940
    Keywords: Trichlorophosphoranylidenesulfamoyl chloride ; Vibrational spectroscopy ; Conformational properties ; Quantum chemical calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Raman (3500-50 cm-l) and infrared (4000-400 cm-l) spectra of the title compound, ClSO2N=PCl3, were recorded for the solid and liquid phase. Additionally, the Raman spectrum of the compound dissolved in CCl4 was obtained and qualitative depolarization values were determined. The spectra of the liquid and solid phase were interpreted in terms of the existence of only one conformation possessing C1 symmetry, as predicted by quantum chemical calculations. A complete vibrational assignment is proposed based on the relative intensities, on group frequencies along with support from the normal coordinate analysis. The experimental fundamental vibrational modes are compared to those obtained from theoretical approaches employing the ab initio MP2/6-31G* method and a density functional approximation (B3PW91/6-31G*).
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300817
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    Ab Initio Studies on Disubstituted closo-Icosahedral Heteroboranes, X2B10H10 [X = CH, SiH, N, P, and Sb] (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1147-1150 
    Details
    ISSN: 0009-2940
    Keywords: Icosahedral heteroboranes ; Ab initio calculation ; Bonding models ; Aromaticity ; Nucleus Independent Chemical Shift [NICS] ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio theoretical studies on X2B10H10 (X = CH, SiH, N, P and Sb) have been done for all the three possible isomers. Unlike lower-vertex heteroboranes, all the hetero derivatives have shown similar trends in the relative stabilities, the 1,12-isomer being more stable followed by 1,7- and 1,2-isomers, except for N and Sb. No conventional 1,2-isomer for N could be found. Instead, a new nido isomer which is 18.1 kcal/mol higher in energy than the most stable isomer has been located. Any hetero group substitution to icosahedral R12H122- is found to be thermodynamically destabilizing. However, the Nucleus Independent Chemical Shift criterion shows that all compounds, except for 8, have similar aromaticity.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19971300818
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    The Molecular Structures of Triaminosilanes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1159-1166 
    Details
    ISSN: 0009-2940
    Keywords: Aminosilantes ; Structure elucidation ; Molecular conformations ; Configuration determination ; Nitrogen Planarity/Silanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structural chemistry of a series of triaminosilanes XSi(NR2)3 has been investigated in order to determine the ground-state configuration and conformation of these molecules. Theoretical studies and analogy with the isoelectronic XP(NR2)3 (X = CH2, O, Se, NSiMe3 etc.) and P(NR2)3 molecules suggest structures of Cs or C3 symmetry, with small energy differences between them. The molecular structure of HSi(NMe2)3 (1) has been determined by a single-crystal X-ray diffraction study at low temperature. Surprisingly, the molecules have a non-standard conformation with an irregular orientation of the three NMe2 groups. The hydrido-, chloro-, methyl-, and vinyltris(morpholino)silanes XSi[N(CH2CH2)2O]3 (X = H, Cl, Me, Vi; 2-5) were prepared from the corresponding chlorosilanes and morpholine (2, 3) or lithium morpholide (4,5). Their variable-temperature NMR spectra were studied and the molecular structures determined by single crystal X-ray diffraction. Compound 2 has a molecular geometry approaching mirror symmetry with one morpholino group significantly different from the other two. This structure resembles that of isoelectronic tris(amino)phosphines. Compounds 3-5 have structures with a propeller-like arrangement of the three morpholino rings approaching C3 symmetry for this part of the molecules. The chloro compound 3 shows the shortest Si-N bond lengths (average 1.690 Å), followed by 2 (1.708Å),5 (1.709Å) and 4 (l.712Å). The configuration of all nitrogen atoms is almost planar, with sums of the angles close to 360°, and the morpholino rings adopt a chair conformation. According to the solution NMR spectra the ring inversion is slow at low temperature, but the rings rotate freely about the Si-N bonds on the NMR time scale. The molecular structures are discussed in terms of steric and electronic effects of the substituents. Other model compounds, including (Me2N)3SiC6H4-4-Br (6), MeSi[N(CH2CH2)2NMe]3 (7) and PhSi[N(CH2)4]3 (8), could not be crystallized, but were characterized by their analytical and spectroscopic data.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300820
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    A Monomeric Bis(arena)lead(II) Complex with a Plumbocene-like Bent Sandwich Structural Unit  -  Structure of [Pb(1,2-C6H4Me2)2(AlCl4)2Dedicated to Professor C. G. Kreiter on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1731-1732 
    Details
    ISSN: 0009-2940
    Keywords: Lead ; Tetrachloroaluminate ; Arenes ; o-Xylene ; Bis(arene) Complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(o-xylene)lead(II) bis(tetrachloroaluminate), obtained from lead(II) chloride and aluminium trichloride in o-xylene, has been shown by X-ray crystallography to be a mononuclear lead complex with point group symmetry C2 The two aromatic ligands are arranged similarly to those in monomeric plumbocene. The coordination sphere is completed by two bidentate AlCl4-ions. The lead center uses about a quarter of its bonding capability for each of the four ligands
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    URL: http://dx.doi.org/10.1002/cber.19971301204
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    Titanium and Zirconium Complexes Containing a Novel Dianionic Trifunctional Amido Ligand (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1751-1759 
    Details
    ISSN: 0009-2940
    Keywords: Amido complexes ; Titanium ; Zirconium ; Alkylmetal compounds ; Amido complexes ; Titanium ; Zirconium ; Alkylmetal compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel tridentate diamidoamine ligands [RC(2C5H4N)(CH2NSiMe3)2)2- (R = H, CH3) have been synthesized and coordinated to TiIV giving the pentacoordinate complexes [MX2(RC(2-C5H4N)(CH2NSiMe3)2}] (M = Ti, Zr; X = Cl, Br). The crystal structure analysis of [TiBr2{HC(2-C5H4N)(CH2)2}] (M = Ti, Zr; X = Cl, Br). The crystal structure analysis of [TiBr2{HC(2-C5H4N)(CH2NSiMe3))] (10b) confirmed the involvement of the pyridyl function in the coordination to the meta centre occupying an apical position in the trigonal bipyramidal ligand polyhedron. alkylation of [TiCl2{H3CC(2-C5H4N)(CH2NSiMe3)2)] (12a) with one or two molar equivalents of [RMgCl](R = PhCH2, Me3SiC2) yielded the mono- and dialkyl complexes [TiClR{H3CC(2-C5H4N)(CH2NSiMe3)2)] and [TiR2(H3CC(2-C5H4N)(CH2NSiMe3)2)] and [TiR2(H3CC(2-C5H4N)(CH2NSiMe3)2}] in good yields. Depending on the steric demand of the alkyl group coordination or decoordination of the pyridyl group leads to four- or five-coordinate species. A crystal structure analysis of the pentacoordinate complex [TiCl(CH2SiMe3){H3CC(2-C5H4N)(CH2NSiMe3)2}] (16) was carried out.
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    Masthead (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301101
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    Cobalt Phthalocyanine Derivatives Supported on TiO2 by Sol-Gel Processing. Part 1: Preparation and Microstructure (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1585-1589 
    Details
    ISSN: 0009-2940
    Keywords: Phthalocyanines ; Sol-gel processes ; Titanium alkoxides ; Supported catalysts ; Heterogenous catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cobalt(II) 2,9,16,23-tetrasulphophthalocyanine and cobalt(II) 2,9,16,23-tetra(chlorosulphonyl)phthalocyanine were supported on TiO2 by reaction of the phthalocyanines with Ti(OR)4 followed by sol-gel synthesis. The thus obtained solid materials are stable in sulfide-containing media and are therefore suitable as catalysts for HS oxidation. The structure of the samples was characterized by electron microscopy diffraction. The morphology of the matrix strongly depends on the cobalt phthalocyanine derivative. The pathalocyanines in the titania matrices are monomeric or dimeric depending both on the type of substituents of the CoPc derivative and on the titanium alkoxide used as precursors.
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    Reversible Rearrangements of Chlorophosphane-Dichlorogermylene Ylides to Trichlorogermylphosphanes  -  Structure Determination of a Tetranuclear Bis(chlorophosphane)bis(trichlorogermylphosphane) Silver Bromide Complex (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1619-1623 
    Details
    ISSN: 0009-2940
    Keywords: Dichlorogermylene ; Trichlorogermylphosphanes ; Insertion ; Silver bromide complex ; Carbene homologues ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chlorophosphanes RR'PCl (1a: R,R' = 1b: R = tBu, R' = iPr, 1c: R = iPr, R' = Et2N, 1d: R = Et2N react with the dichlorogermylene dioxane complex 2 furnishing trichlorogermylphosphanes RR'PGeCl3 4a-d. In the cases of 1c/4c and 1d/4d the insertion reaction remain incomplete; similarly, 4a always contains, shortly after isolation in pure state, small amounts of 1a that can be detected by NMR. A provided by the reaction of trichlorosilylphosphane tBu(Et2N)PSiCl3 (5d) with GeCl4. The alkyl(dialkylamino) trichlorogermylphosphane 4d exists only in an equilibrium with chlorophosphane 1d, which coordinates GeCl2 leading to the dichlorogermylene complex 3d. A 1:1 mixture of 4a with 1a is formed by the novel cleavage (“chlorogermylation”) of the P-P bond of tetraisopropyldiphosphane with germanium tetrachloride. Di-tert-butyl(trichlorogermyl)phosphane 4e (R, R' = tBu) reacts with silver bromide providing a crystalline silver complex 7. A structure determination by X-ray diffraction reveals that 7 is [Ag4Br4(tBu2PCl)2(tBu2PGeCl3)2]. 2C7H8. Two of the Ag atoms of the cubane-like (AgBr)4 core of 7 are coordinated by chlorophosphane 1e, the other two by trichlorogermylphosphane 4e.
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    Formation of the Cationic [(2-Aminoethenyl)carbine]iron Complexes by Treatment of (2-Methoxyethenyl)carbene Complexes with Primary Amines:Synthesis and Characterisation (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1647-1654 
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    ISSN: 0009-2940
    Keywords: Iron ; Carbene complexes ; (2-Methoxythenyl)methoxycarbene complexes ; Aminolysis ; (2-Aminoethenyl) methoxycarbene complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic (2-methoxyethenyl)methoxycarbene iron complexes 2, [Cp(CO)2Fe(C(OMe)CH=CR(OMe))+][PF6-], are obtained by the addition of methanol to the corresponding (alkynyl)-methoxycarbene complexes 1, [Cp(CO)2Fe(C(OMe)C≡CR)+][PF6-]. Primary amines, H2NR', react with these 1,3-dimethoxy-substituted (alkenyl)carbene complexes, 2, through an addition/elimination process to yield cationic (2-aminoethenyl)methoxycarbene iron complexes, 3, [Cp(CO)2Fe(C(OMe)CH=CR(NHR'))+][PF6-] in an isolated yield of 71-90%. The complexes 3a-c were characterized by X-ray structural analyses. Thus, previously isolated products, from the reaction, of the (alkynyl)methoxycarbene complexes 1a and 1c, with aniline at room temperature, are assigned to the structures 3c and 3e. The spectroscopic and structural data obtained are discussed.
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    1-Hexene Hydroformylation with the Rhodium (I) Triphosphane Complex [Rh(CO){PhP(CH2CH2PPh2)2}]PF6: An In Situ Study Using High-Pressure NMR Spectroscopy (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1633-1641 
    Details
    ISSN: 0009-2940
    Keywords: Hydroformylation ; High-pressure NMR ; Homogeneous catalysis ; Rhodium ; Polyphosphane ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rhodium-catalyzed hydroformylation of 1-hexene in THF with the linear triphosphane PhP(CH2CH2PPh2)2 [PP,] has been studied both in situ and in high-pressure autoclaves. Sapphire NMR tubes with titanium valves have proved useful for studying the in situ reactions under conditions of relatively high syngas pressure (30-90 atm H,/CO) and temperature (60-100 C). Under conditions conducive to effective hydroformylation, the catalyst precursor [ (PP,)Rh(CO)]+ is quantitatively converted to the dicarbonyl [ (PP,)Rh(CO),]+, which is also the termination product of the catalysis. Irrespective of the syngas composition and of the total pressure, the dicarbonyl complex is the only phosphorus-containing species detectable on the NMR time-scale during the course of the isomerization and hydroformylation of the alkene. The PP2-Rh catalytic system exhibits some peculiar features that may be summarized as follows. (i) Very high partial pressures of CO (120 atm) neither inhibit the hydroformylation nor affect the n/i selectivity; (ii) alkene hydrogenation occurs neither at very high partial pressures of H, (120 atm) nor in the absence of added CO; (iii) the isomerization rate is slightly faster than that of hydroformylation; (iv) terminal and internal alkenes (2-, 3-hexenes) are hydroformylated with comparable rates. Various control experiments have been carried out using in-situ NMR, as well as batch experiments under different reaction conditions or with different catalyst precursors. Despite these extensive studies, unambiguous conclusions about the catalysis mechanism have not been reached. In particular, the possibility that different catalysts may be operative depending on the reaction conditions cannot be ruled out. The hydroformylation results rule out the involvement of phosphane-free “Rh-CO” catalysts, even under conditions of very high partial pressure of CO, and point to “(PP,)Rh(CO),” catalysts with small steric hindrance over the whole range of syngas pressures investigated.
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    Masthead (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cber.19971301201
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    Coordination Chemistry of PentahalocyclopentadienylsThis article is dedicated to Professor Wolfgang Beck on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1721-1730 
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    ISSN: 0009-2940
    Keywords: Perhalometallocenes ; Cylopentadienes ; Perhalogenated ; Halogen-metal exchange reactions ; Sandwich complexes ; Ligand effects ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination chemistry of perhalocyclopentadienyl ligands, first developed in the early 1970's as a part of a research program directed towards the synthesis of oxidation-resistant fuel additives, has been revived in the last ten years. This renewed interest stems from the discovery that the coordinated cyclopentadienyl ligand allows multiple functionalizations. Thus, the high versatility of this important class of ligands can be broadened even further, which may be important with regard to industrial applications of metallocenes.
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    Density Functional Studies on Amino-Substituted Methane and Silane (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1745-1749 
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    ISSN: 0009-2940
    Keywords: Density functional calculations ; Tetra(amino)methane ; Tetra(amino)silane ; Transition states ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In all-electron density functional calculations on mono- and tetraaminosubstituted methane and silane the coordination around the nitrogen center is found, in complete agreement with experiment, to be less pyramidal in the silicon compounds. The calculated barrier to inversion at nitrogen is only 0.6 kcal/mol in silylamine, while in methylamine it is 5.5 kcal/mol. The larger flexibility is attributed to the greater ionic character of the Si-N bond compared to that of the C-N bond. In tetra(amino)methane, inversion of one amino group leads to a local minimum (calculated inversion barrier: 6.4 kcal/mol), while a corresponding structure (or barrier) does not exist for the silicon compound. Due to the steric influence of the amino groups, the barrier to rotation around the C-N bond is larger in the tetrasubstituted compound (6.4 kcal/mol compared to 2.3 kcal/mol in methylamine). While the average binding energy of the amino groups is similar in both tetra(amino)compounds, the binding energy of the fourth ligand is about 25% larger in the silicon compound for both homolytic and heterolytic bond cleavage. This difference arises from the relative stabilization of the tri(amino)-methyl species, due to some n contribution to the C-N bond.
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    URL: http://dx.doi.org/10.1002/cber.19971301207
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    Phosphanyl-Substituted Phosphaferrocenes as p,p-Chelate Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1771-1776 
    Details
    ISSN: 0009-2940
    Keywords: Chelates ; P ligands ; Phosphaferrocene ; Carbonyl complexes ; Heterocycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dicyclohexyl-acid diphenylphosphanyl-substituted phosphaferrocenes 2 and 3 were synthesized by substitution of the amino group in 2-dimethylaminomethyl-3,4,-dimethylphosphaferrocene 1 · Homologization of 2-formyl-3,4-dimethylphosphaferrocene 4 by one CH2 unit via Wittig olefination provided access to the phosphanylethyl derivative 9. Ligands 2, 3 and 9 formed P, P-chelate complexes with tetracarbonyl metal fragments in good yield. X-ray crystal structure determinations were carried out for the five-ring chelate complex 2. Mo(CO)4 (≡ l0), and the six-ring chelate complex 9 . Mo(CO)4, (≡ 13).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301211
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  • 97
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    Electronic Resource
    A Structural Study of Selenobenzamides: Crystal Structures and Dynamic 13C NMR (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 49-54 
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    ISSN: 0009-2940
    Keywords: 4-(p-Bromoselenobenzoyl)morpholine ; 4-[(p-(Dimethylamino)selenobenzoyl]morpholine ; Hindered rotation ; Hammett treatment ; Selenoamides ; Amides ; Selenium compounds ; Structure elucidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-state structures of (p-bromoselenobenzoyl)morpholine (2a) and [p-(dimethylamino)selenobenzoyl]morpholine (2b) were determined by X-ray diffraction. Both molecules show a flat selenoamide group. The larger contribution of resonance stabilization by the aromatic ring carrying the p-dimethylamino substituent is reflected by the smaller interplanar angle Θ between the aromatic ring and the selenoamide group [53.3(1)° vs. 81.1(1)°] and by the shorter length of the C=Se bond [1.824(5) Å vs. 1.840(3) Å]. The Gibbs free energy of activation of C-N bond rotation (ΔG≠rot) of five p-substituted (selenobenzoyl)morpholines was determined by dynamic 13C NMR. The activation barriers were found to range from 61.6 kJ/mol (X = NNMe2) to 75.1 kJ/mol (X = H). The ΔG≠rot values of the corresponding (thiobenzoyl)morpholines were found to be from 3.2 kJ/mol (X = NMe2) to 5.0 kJ/mol (X = H) lower. In both cases, ΔG≠rot showed an excellent linear Hammett correlation with s̰+p.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300108
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  • 98
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    Electronic Resource
    A Theoretical Investigation of Cycloadditions of Hydrogen Isocyanide to CH2=X and PH=X Dipolarophiles (X = CH2, NH, O, SiH2, PH, S)We dedicate this paper to the memory of our friend and colleague, Prof. Dr. Gerrit L'Abbé, who untimely passed away on August 27, 1996. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 69-76 
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    ISSN: 0009-2940
    Keywords: [2 + 1] Cycloadditions ; Hydrogen cyanide ; Phosphorus dipolarophiles ; Three-membered rings ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We performed a systematic investigation of [2 + 1] cycloadditions of HN≡C to dipolarophiles of the type CH2=X and PH=X with X=CH2, NH, O, SiH2, PH, and S, as well as HN=NH and H2Si=SiH2. Ab initio MO calculations at the QCISD(T)/6-311G(d,p)/MP2/6-31G(d,p)+ZPE level were applied to construct the minimum-energy reaction pathways. Calculated results concerning the regiochemistry of the approaches and the stereochemistry of the product formation were analyzed in relation with established concepts such as frontier orbital, net charge distribution and stereoelectronic effect. For some systems, up to four distinct transition structures for cycloaddition were found. In general, there is a certain similarity between the behavior of both C and P series of dipolarophiles. The characteristics of the transition structures can be, in most cases, recovered by using qualitative concepts. The [2 + 1] cycloadditions are highly regioselective and stereospecific. Silicon-containing dipolarophiles are particularly attractive as they exhibit very small energy barriers to addition to isocyanides.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300111
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  • 99
    Electronic Resource
    Electronic Resource
    Triphenylphosphonio-Substituted 1,2,3,4-Triazaphospholes and 1,2,4-Diazaphospholes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 89-94 
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    ISSN: 0009-2940
    Keywords: (Triphenylphosphonio)phosphaethyne ; Azides ; [3 + 2] Cycloadditions ; Phosphonio-1,2,3,4-triazaphospholes ; Diphosphonio-1,2,4-diazahospholes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several products resulting from the condensation of the bis-(trimethylsilyl)ylide 1 with PCl3 serve as synthetic equivalents of a phosphoniophosphaethyne. Cycloaddition reactions with azides lead to phosphonio-1,2,3,4-triazaphosphole cations 5, 7 and to the zwitterionic phosphonio-1,2,3,4-triazaphospholide 6. The latter readily undergoes a cycloreversion yielding a phosphoranediyl diazomethane 12 as intermediate. Its cycloaddition affords the diphosphonio-1,2,4-diazaphosholide chloride 9a as the final product. 9a is a remarkably stable and unreactive derivative of the two-coordinate phosphorus. By HCL it is protonated at a nitrogen atom to give dication without any tendency to associate with the chloride counterions.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300114
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  • 100
    Electronic Resource
    Electronic Resource
    Tris(phenylthiomethyl)phosphane Sulfide and Selenide, (PhSCH2)3PX (X = S, Se), as Ambidentate Ligand Systems in Copper(I) Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 105-110 
    Details
    ISSN: 0009-2940
    Keywords: Sulfides ; Selenides ; Copper complexes ; Ambidentate ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Triphenylphosphite has been converted into tris(phenylthiomethyl)phosphane (1) by reaction with LiCH2SPh/DABCO, and subsequently into the corresponding sulfide (2) and selenide (3) by treatment with elemental sulfur or selenium, respectively. Ligands 2 and 3 react with copper(I) halides CuX (X = Cl, Br, I) in polar organic solvents to give either 1:1 (X = Cl: 4, 7, X = Br: 5, 8 ) or 1:2 complexes (X = Br: 9, X = I: 6, 10). The crystal structures of five of these complexes have been determined by single crystal X-ray diffraction studies. All compounds of the type [(PhSCH2)3P=S/Se]CuX (X = Cl, Br) form centrosymmetrical dinuclear complexes featuring a four-membered ring core Cu2[S/Se], fused to two five-membered rings Cu[S/Se]PCS through common trans edges. Only one of the three phenyl-thiomethyl functions is involved in coordination to a metal center. The compound [(PhSCH2)3P=S](CuI)2 (6) is associated into a centrosymmetrical tetranuclear complex containing two four-membered rings (ICu2S) bridged via iodine atoms in 1,3-cis positions. The ligand is found to employ two of its PhSCH2 functions for metal coordination, giving rise to two five-membered rings fused to the four-membered rings via neighbouring edges. In all cases, therefore, the P=S/Se functions of the ligands are the preferred donor sites, which are used for the building of bridgehead structural units of polynuclear complexes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300117
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