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  • 1995-1999  (640)
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  • 1
    ISSN: 1437-160X
    Keywords: Rheumatoid pannus ; Adhesion molecules ; β1 integrins ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To investigate the mechanism of synovial pannus formation in rheumatoid arthritis, immunohistochemical and immunoelectron microscopic studies with monoclonal antibodies against the adhesion molecules, CD54 (ICAM-1), CD 11a (LFA-1), CDw49a (VLA-1), CDw49b (VLA-2), CDw49c (VLA-3), Cdw49d (VLA-4) and CDw49e (VLA-5), were carried out to determine the pattern of distribution of these molecules at the rheumatoid synovial cartilage junction. Treatment with anti-ICAM-1 resulted in membrane staining of most of the macrophages and fibroblasts infiltrating the synovial tissue and bordering the pannus-cartilage junction, suggesting the possibility that ICAM-1 may function to facilitate the adhesion of synovial type A cells bearing ICAM-1 to type B cells of the pannus. ICAM-1-positive macrophages and fibroblasts were often found to be in contact with lymphoid cells, suggesting also that a cellular immune reaction occurs in the formation of the pannus. In addition, VLA-3, VLA-4 and, particularly, VLA-5 were the predominantβ1 integrins expressed by rheumatoid synovial pannus. Since these three integrins all function as fibronectin receptors, it is possible that the fibronectin-rich environment of the rheumatoid cartilage surface effectively traps pannus cells expressing high levels of these molecules. The VLA-5 molecule was found in a pericellular and interterritorial matrix distribution in the present study, strongly suggesting that a recepfor-ligand interaction between VLA-5 and cartilage matrix may occur at the early stage of pannus formation. Furthermore, an increase inβ1 integrin may be necessary for the growth of the pannus and also for the upregulation of the VLA molecules, leading secondarily to increased attachment.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Neurosurgical review 19 (1996), S. 39-42 
    ISSN: 1437-2320
    Keywords: Electron microscopy ; immunohistochemistry ; meningeal melanocytoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A case of cervical juxtamedullary meningeal melanocytoma is presented along with results of careful neuroradiological and pathological examinations. The authors review the previous literature and discuss the problems related to the intriguing diagnosis of this very rare entity. CT and MRI show variable appearances due to different degrees of melanization and do not reliably allow us to distinguish meningeal melanocytomas from other pigmented tumors. Pathological examination of the tumor is critical for diagnosis, but is absolutely must comprise electron microscopy and immunohistochemistry. Immunohistochemical and ultrastructural criteria are thus proposed to distinguish meningeal melanocytoma from pigmented meningioma or schwannoma and malignant melanoma (primary or secondary).
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1433-0423
    Keywords: Schlüsselwörter Makulaforamen ; Epiretinale Membran ; Elektronenmikroskopie ; Vitrektomie ; Pathogenese ; Key words Macular hole ; Epiretinal membrane ; Electron microscopy ; Vitrectomy ; Pathogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Anteroposterior and tangential traction on the central retina is an important factor in the pathogenesis of idiopathic macular hole formation. Histological studies have shown that macular holes of different stages can be associated with epiretinal membranes. Such membranes can be removed during surgery for macular holes. We investigated such tissue samples of 11 patients with macular holes in stages II – IV. Light microscopially, the tissue consisted of a thin collagen layer mostly covered by a thin layer of cells. Ultrastructural analysis revealed glial cells and macrophages as cellular components. The collagen can be ascribed to vitreous, inner limiting membrane and newly formed collagen. According to the morphological findings a multilayered tissue structure can be assumed. Macrophages were found on the retinal side of the inner limiting membrane and at the vitreal side of the tissue. Therefore, the macrophages probably originate from the retina as well as from the vitreous as so-called resident hyalocytes. Glial cells covered the inner limiting membrane forming pericellular collagen to which outer vitreous collagen fibrils can be attached. The multilayered membrane structure might possibly be the cause for only partial laminar surgical extraction so that contractile or potentially proliferative tissue residues might be one of the reasons for surgical failures after incomplete membrane peeling.
    Notes: A.-p. und tangentiale Traktionen an der zentralen Netzhaut spielen für die Entstehung idiopathischer Makulaforamina eine wichtige Rolle. Durch histologische Untersuchungen ließen sich bei Makulaforamina unterschiedlicher Stadien epiretinale Membranen nachweisen, die für die tangentiale Traktion auf die Foramenränder verantwortlich gemacht werden. Von 11 Patienten konnten wir derartige, von uns chirurgisch entfernte Membranen licht- und elektronenmikroskopisch untersuchen. Die Membanen bestehen lichtmikroskopisch aus einem azellulären Kollagenband mit einem schmalen, teilweise nur einschichtigen Zellbesatz. Elektronenmikroskopisch lassen sich als zelluläre Komponenten Gliazellen und Makrophagen differenzieren. Die Kollagenanteile sind Glaskörperkollagen, neugebildetem Kollagen und der Lamina limitans interna zuzuordnen. Aus den Befunden läßt sich eine Schichtung der Membranen rekonstruieren mit sublaminären Makrophagen, der Lamina limitans interna und epilaminären Gliazellen und vereinzelten Makrophagen, die am ehesten residenten Hyalozyten entsprechen. Auf der vitrealen Seite können auch Verbindungen der Membran zum äußeren Glaskörperkollagen bestehen. Die Membranen zeigen Charakteristika, die in ihrem Aufbau epiretinalen Proliferationsmembranen entsprechen. Die topographische Schichtung der Membranen könnte zur Folge haben, daß chirurgisch teilweise nur Lamellen und nicht die gesamte Membran abgeschält werden. Kontraktions- oder auch proliferationsfähige Membranreste können dann einer der Faktoren für operative Mißerfolge sein.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric surgery international 12 (1996), S. 49-53 
    ISSN: 1437-9813
    Keywords: Key words Silicone ; Silicon tubing ; Ivac 560 pump ; Energy-dispersive X-ray analysis (EDXA) ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Migration of particulate matter from plastic tubing and solid plastic implants has been documented in a number of studies, including some with the use of cardiac bypass, haemodialysis, and pump-assisted intravenous infusions. In order to ascertain whether silicone embolisation occurs when children have an Ivac 560 pump-assisted IV infusion, we passed 180 ml of pumped fluid through a microfilter and compared the scanning electron micrographs of those filters with unused filters and with others through which a similar volume had been passed without using the pump. The particles on the filters were analysed for their elemental content using energy-dispersive X-ray analysis. In addition, the appearance of the silicone tubing used in the pump over 3 and 72 h was assessed and compared to that of flow-only and unused tubing. More particles were found on the microfilter when fluid had been delivered via the pump than on those through which non-pumped fluid had passed or that were unused. Elemental silicon-containing particles were only found on the filter when a pump had been attached to the IV line. The flow-only and unused tubing were found to have adherent particles on the inner surface that were not seen once the tubing had been used for 3 h in the Ivac 560 pump. Also, after 72 h use, the silicone tubing had a deformed inner layer. The clinical significance of these findings is yet to be determined, but it does appear that silicone embolisation occurs during pump-assisted infusions in children.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric surgery international 12 (1996), S. 49-53 
    ISSN: 1437-9813
    Keywords: Silicone ; Silicon tubing ; Ivac 560 pump ; Energy-dispersive X-ray analysis (EDXA) ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Migration of particulate matter from plastic tubing and solid plastic implants has been documented in a number of studies, including some with the use of cardiac bypass, haemodialysis, and pump-assisted intravenous infusions. In order to ascertain whether silicone embolisation occurs when children have an Ivac 560 pump-assisted IV infusion, we passed 180 ml of pumped fluid through a microfilter and compared the scanning electron micrographs of those filters with unused filters and with others through which a similar volume had been passed without using the pump. The particles on the filters were analysed for their elemental content using energy-dispersive X-ray analysis. In addition, the appearance of the silicone tubing used in the pump over 3 and 72 h was assessed and compared to that of flow-only and unused tubing. More particles were found on the microfilter when fluid had been delivered via the pump than on those through which nonpumped fluid had passed or that were unused. Elemental silicon-containing particles were only found on the filter when a pump had been attached to the IV line. The flow-only and unused tubing were found to have adherent particles on the inner surface that were not seen once the tubing had been used for 3 h in the Ivac 560 pump. Also, after 72 h use, the silicone tubing had a deformed inner layer. The clinical significance of these findings is yet to be determined, but it does appear that silicone embolisation occurs during pump-assisted infusions in children.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2307
    Keywords: Papillary adenoma of type II pneumocytes ; Immunohistochemistry ; Electron microscopy ; Morphometry ; Multivariate cluster analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Papillary adenoma of type II pneumocytes is a rare tumour. It is considered to be a benign neoplasm and is derived from immature cells in the bronchioloalveolar epithelium, however, its biological nature has not been elucidated. We report a case of an adenomatous tumour; a papillary adenoma of type II pneumocytes, which we regard as possessing malignant potential. Light microscopically, as well circumscribed, papillary tumour of predominantly cuboidal cells resembling type II pneumocytes was found, but Clara type and ciliated cells were also present. Immunohistochemically, the tumour cells reacted positively with antibodies to surfactant apoproteins (A, B), carcinoembryonic antigen, cytochrome P-450 1A1-2 and 2B1-2. Ultrastructurally, many osmiophilic lamellar bodies and electron-dense granules were demonstrated. Semi-serial sections revealed signs of transbronchial dissemination and vascular invasion. Morphometry using 12-dimensional cluster analysis disclosed features of the tumour cells which resembled those of pneumocyte type II adenocarcinoma. These findings suggest that the present case has some malignant characteristics and originates from immature bronchiolar or alveolar cells, with a potential to develop into both type II pneumocyte and Clara cell type adenocarcinomas.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-0879
    Keywords: Interstitial stroma ; Carcinogenesis ; Bladder epithelium ; Neovascularization ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study describes ultrastructural alterations of the interstitial stroma in the rat bladder epithelium during N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced bladder carcinogenesis using scanning (SEM) and transmission (TEM) electron microscopy with NaOH treatment. The results obtained with SEM demonstrated the occurrence and development of stroma protrusions which exhibited pipe-like structures in the rat bladder epithelium following administration of BBN. Number and size of blood vessel sections also gradually increased both in the stroma and within the layer of the proliferated epithelial cells as examined by light microscopy (LM) and TEM. In this study stroma alterations were not only observed in malignant lesions of rat bladder, but hyperplastic lesions were also accompanied by stroma alterations. It is suggested that: (1) the interstitial stroma of the rat bladder epithelium may exhibit pathological changes in structure and these changes may correlate with the progression of epithelial cell proliferation following administration of BBN and (2) one of the most important alterations in the stroma is the occurrence of neovascularization, which may induce structural modification of the stroma in the processes of bladder tumor growth and development.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 193 (1996), S. 331-339 
    ISSN: 1432-0568
    Keywords: Synapse ; Cell migration ; Olfactory neurons ; Electron microscopy ; Vomeronasal organ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rat neonate vomeronasal organs were transplanted into the parietal cortex of littermates to examine their survival and the behavior of axon growth into the surrounding host brain parenchyma. After survival times of 10–100 days the brains were processed for ultrastructural examination. The transplanted vomeronasal organs (VNO) formed several vesicles lined with a sensory epithelium. From these sensory epithelia, VNO neurons leave the epithelium and enter the host brain. Transplant neurons grew axons that fasciculated into bundles surrounded by sheath cell processes and formed one or more fiber plexuses containing distinct globose or spherical-shaped glomeralar-like structures. The glomeruli consisted of nerve terminals between which existed asymmetric synaptic contacts. Rarely did we observe clear reciprocal synapses. The glomeruli also contained terminals that showed signs of degeneration, such as increased density of the terminals, clumping of mitochondria and multivesicular bodies. The glomeruli were not partitioned or subdivided by glial septa; however, glial profiles were interspersed among the sensory terminals. Transplant glomeruli also lacked periglomerular cells and had no definitive glial envelope. These results suggest that glomerular formation is not dependent on dendrite contribution of second order neurons or glial support, but rather on a complementary population of receptor neurons.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0568
    Keywords: Thalamus ; Somatosensory system ; Synaptogenesis ; Nervous system ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Electron microscopy has been employed to analyze the normal maturationai sequence that characterizes the postnatal development of synaptic circuits in the ventrobasal (VB) and reticular (Rt) thalamic nuclei of rats at different ages (from birth to the end of the third postnatal week). Throughout the first postnatal week, similar signs of immaturity are observed in both nuclei, mainly consisting in scarcity of cytoplasmic organelles, presence of wide extracellular spaces, and absence of myelinated fibers. Several synaptic terminals are however present from birth, thus indicating that some of the afferents have already reached and contacted their thalamic target during embryonic life. Most of the terminals are small and contain only a few round, clear vesicles, and therefore their cytological features do not allow the identification of their origin. In particular, in both nuclei, terminals with flat vesicles and symmetric specialization are only rarely observed, and in VB the ascending terminals are not distinguishable from terminals of other sources as they are in adults. During the second postnatal week, progressive maturationai changes in VB and Rt lead to neurons having well-developed cytoplasmic organelles and to an elaborate neuropil containing myelinated fibers and synaptic terminals that are morphologically heterogeneous and resemble the adult ones. The permanence of growth cone-like profiles and of numerous somatic and dendritic protrusions, often contacted by synaptic terminals, indicates that a certain degree of reorganization is still taking place in both nuclei. By the end of the third postnatal week the synaptic organization of VB and Rt is indistinguishable from that observed in adults. This ultrastructural study shows that the appearance of the neuropil of VB and Rt and the morphological complexity of the synaptic arrangements characteristic of the adult rat are not present in neonates, but are gradually acquired during the first three postnatal weeks, and that they result from progressive modifications in circuit organization involving both pre- and postsynaptic elements.
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  • 10
    ISSN: 1432-0533
    Keywords: Key words Fukuyama-type congential muscular ; dystrophy ; Fetus ; Cerebrocortical pathology ; Breaches in glia limitans ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A light and electron microscopic study of the brain of an 18-week fetus with a prenatal genetic diagnosis of Fukuyama-type congenital muscular dystrophy revealed a widespread mantle of abnormal neurogliomesenchymal tissue that covered a dysplastic cerebral cortex. In this area alone, the glia limitans that adjoined the abnormal mantle via one or two layers of basal lamina had frequent breaches, through which neuroglial elements extruded. In the most severely affected cortical region, which had only a rudimentary and fragmentary glia limitans, the majority of cortical neurons had migrated into the neurogliomesenchymal tissue. The massive overmigrated neurons still maintained a somewhat columnar arrangement, and the marked dysplasia abruptly shifted to a neurogliomesenchymal tissue-free normal cortical structure with an intact glia limitans, thus indicating essentially vertical overmigration of neurons without significant tangential migration of them. Together the above findings imply that breaches in the glia limitans may be the primary cause of the micropolygyria seen in this genetic disorder.
    Type of Medium: Electronic Resource
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  • 11
    ISSN: 1432-0533
    Keywords: Key words Central neurocytoma ; Glial fibrillary acidic protein ; Immunohistochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have identified two central neurocytomas which contained cells co-expressing glial fibrillary acidic protein and synaptophysin defined by double-label immunostaining. Dual-positive cells were mostly polygonal in shape and with a morphological appearence similar to that of reactive astrocytes. This distinct morphology could be used to distinguish cells expressing glial fibrillary acidic protein from cells with round and clear cytoplasm which did not express glial fibrillary acidic protein and which composed the majority of the tumor. Samples containing polygonal cells were selected for electron microscopy from toluidine blue-stained semithin sections. Ultrastructural findings were similar in both neurocytomas, with both being composed predominantly of round cells with clear cytoplasm corresponding to the clear cells identified by light microscopy. Dense-core vesicles and clear vesicles were frequently observed in the cell processes. Apart from these clear cells, polygonal cells with electron-dense cytoplasm were noted. Paralleling the results of double immunostaining, these polygonal cells contained both dense-core vesicles and intermediate, presumably glial filaments. Microtubules and lipofuscin granules were also observed. These results suggest that cells expressing glial fibrillary acidic protein in central neurocytoma include tumor cells with both neuronal and glial characteristics.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 193 (1996), S. 259-269 
    ISSN: 1432-0568
    Keywords: Stomach ; Parietal cell lineage ; Heterogeneity ; Electron microscopy ; Cattle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The origin and differentiation of the oxyntic cell lineage during physiological cell renewal was investigated by light and electron microscopy in the abomasal mucosa of adult cattle. The morphologically heterogeneous oxyntic cell population exhibits various developmental subtypes depending on the position within the oxyntic unit. Pre-oxyntic cells of the isthmus and neck represent the immature precursors. Though heterogeneous with respect to the degree of canalicular and tubulovesicular membrane development, they all contain secretory granules resembling those of either isthmus cells, immature surface mucous cells, neck cells or young chief cells. A secretory granule-free stem cell is not present in the bovine. Downward to the gland base genesis of canalicular as well as tubulovesicular membranes is gradually completed; thus pre-oxyntic cells give rise to mature oxyntic cells. Older degenerative oxyntic cells, primarily located within the gland bottom, are characterized by progressive involution of canalicular and tubulovesicular membranes. Towards the pit, differentiation of pre-oxyntic cells is associated with atypical and incomplete development of canaliculi and tubulovesicles. In consequence, these superficial oxyntic cells have a reduced secretory capacity from a morphological point of view.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 288 (1996), S. 91-97 
    ISSN: 1432-069X
    Keywords: Key words Hemidesmosomes ; Basement membrane ; Fetal skin ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hemidesmosomes are junctional complexes involved in the attachment of epidermal basal keratinocytes to the basement membrane. To try to understand better the sequence of events in the morphogenesis of hemidesmosomes, we undertook an ultrastructural analysis of hemidesmosome formation in fetal and neonatal digit skin. Hemidesmosomes, defined as membrane-associated densities or plaques, were counted and scored for three morphological characteristics: (1) the presence of a sub-basal dense plate, (2) association with anchoring filaments within the lamina lucida and (3) contacts with intermediate filaments. No hemidesmosomes were evident at 7 weeks’ gestational age. Between 9 and 15 weeks the number of hemidesmosomes increased by about fourfold (from 20.6 ± 3.8 (SD) to 95.5 ± 8.4 per 40 μm of basal cell plasma membrane; P 〈 0.01). The association of hemidesmosomes with intermediate filaments and anchoring filaments also increased after 15 weeks ( P 〈 0.05). Early attachment plaques first appeared as triangular focal densities on the basal plasma membrane with the appearance of sub-basal dense plates, which later became both larger and more electron dense. By 15 weeks, an inner plaque could be distinguished from the outer plaque, which coincided with a closer association with intermediate filaments. Hemidesmosomes appeared fully developed by 15 weeks’ gestation. This study illustrates the structural relationship of hemidesmosomes to both intra- and extracellular filaments, suggesting close functional interactions. The complexity of the hemidesmosome plaque is also revealed early during development.
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  • 14
    ISSN: 1432-1173
    Keywords: Schlüsselwörter Papillomatosis confluens et reticularis ; Minocyclin ; Tetracycline ; Elektronenmikroskopie ; Key words Confluent and reticulated papillomatosis ; Minocycline ; Tetracycline ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Confluent and reticulated papillomatosis (CRP) is a rare dermatosis of unknown aetiology. Recent electron microscopic studies suggest that CRP is a disorder of keratinisation. In our case we could not confirm the previously reported ultrastructural findings. CRP is generally resistant to therapy. We treated a 19-year-old patient with typical CRP with oral minocycline. Within a few weeks the eruption resolved completely. A mild relapse 7 months later responded promptly to a repeated course of minocycline. Twelve months after discontinuatin of therapy there is no evidence of recurrence. In CRP minocycline should be preferred to systemic retinoid therapy because of its minor side effects.
    Notes: Zusammenfassung Die Papillomatosis confluens et reticularis (PCR) ist eine seltene Erkrankung unklarer Ätiopathogenese. Neuere elektronenmikroskopische Untersuchungen stützen die Vermutung, daß eine Keratinisierungsstörung vorliegt. Anhand unseres Falles konnten wir diese Befunde allerdings nicht bestätigen. Die PCR ist ausgesprochen therapieresistent. Wir behandelten einen 19jährigen Patienten mit klinisch und histologisch typischer PCR systemisch mit Minocyclin. Innerhalb weniger Wochen heilten die Effloreszenzen vollständig ab. Ein 7 Monate später auftretendes leichtes Rezidiv konnte durch einen zweiten Behandlungszyklus schnell und erfolgreich behandelt werden. Der Patient ist jetzt bereits 12 Monate nach Absetzen der Therapie erscheinungsfrei. Zur Behandlung der PCR sollte Minocyclin wegen seiner geringeren Nebenwirkungen systemischen Retinoiden vorgezogen werden.
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  • 15
    ISSN: 1432-1106
    Keywords: GluR1 ; GABA ; Electron microscopy ; Cerebral neocortex ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Specimens of human cerebral neocortex were obtained during neurosurgical operations and studied by immunocytochemistry and electron microscopy, using antibodies to the glutamate receptor subunit GluR1 and gamma-aminobutyric acid (GABA). Many GluR1-positive pyramidal neurons and fewer GluR1-positive nonpyramidal neurons were present in the cortex. Non-pyramidal neurons were more heavily labelled for GluR1 than pyramidal neurons. Most GABAergic neurons were labelled for GluR1. The white matter was unstained, except for occasional labelled neurons. This pattern of GluR1 immunostaining is similar to that in rat cerebral cortex, but is different from that in the hippocampus and amygdala, where large numbers of pyramidal or projection neurons, but few non-pyramidal or GABAergic neurons, were labelled for GluR1.
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  • 16
    ISSN: 1432-1106
    Keywords: Glutamate receptor ; Cerebral cortex ; White matter ; Electron microscopy ; Development ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The distribution of the [3H]alpha-amino-3-hydroxy-5-methylisoxzalepropionic acid (AMPA) receptor subunit GluR4 was studied in frontal, parietal and temporal cerebral cortex, subcortical white matter and corpus callosum of neonatal, immature and mature rats. In 1-to 2-day-old rats, a few oligodendrocyte progenitors and amoeboid microglia in the supraventricular part of the corpus callosum were immunolabelled for GluR4. At 7 to 10 days, the number of amoeboid microglia and oligodendrocyte progenitors in white matter increased; many neurons in cortex, including pyramidal neurons, were also moderately labelled for GluR4. The pattern of GluR4 immunostaining in 14-day-old rats was different from that in 7-to 10-day-old rats, but similar to the adult, in that there was no immunoreactivity in microglia and oligodendrocyte progenitors in subcortical white matter. A proportion of non-pyramidal neurons in cortex were moderately labelled, while some pyramidal neurons were lightly labelled. A population of small glial cells with features of oligodendrocyte progenitors were densely labelled in cortex.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 155 (1996), S. 561-567 
    ISSN: 1432-1076
    Keywords: Key words Glycogen deficiency ; Glycogen synthase ; Ketotic ; hypoglycaemia ; Corn (maize) ; starch ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Three children from two German families are described and the observations compared with the previously published three families comprising eight patients. The two index cases presented with morning fatigue, had ketotic hypoglycaemia when fasting which rapidly disappeared after eating, and hepatic glycogen deficiency and absent or very low hepatic glycogen synthase activity. Metabolic profiles comprising glucose, lactate, alanine, and ketones in blood were typical for hepatic glycogen synthase deficiency. Symptoms were rapidly relieved and chemical signs corrected by introducing frequent protein-rich meals and night-time feedings of suspensions of uncooked corn (maize) starch. The discovery of oligosymptomatic and asymptomatic siblings suggests that there are more persons with undiagnosed hepatic glycogen synthase deficiency. Conclusion Liver glycogen synthase deficiency is likely to be more common than is believed today. It should be sought in children who, before the first meal of the day, present with drowsiness, lack of attention, pallor, uncoordinated eye movements, disorientation or convulsions and who have hypoglycaemia and acetone in urine.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 155 (1996), S. 561-567 
    ISSN: 1432-1076
    Keywords: Glycogen deficiency ; Glycogen synthase ; Ketotic hypoglycaemia ; Corn (maize) starch ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Three children from two German families are described and the observations compared with the previously published three families comprising eight patients. The two index cases presented with morning fatigue, had ketotic hypoglycaemia when fasting which rapidly disappeared after eating, and hepatic glycogen deficiency and absent or very low hepatic glycogen synthase activity. Metabolic profiles comprising glucose, lactate, alanine, and ketones in blood were typical for hepatic glycogen synthase deficiency. Symptoms were rapidly relieved and chemical signs corrected by introducing frequent protein-rich meals and night-time feedings of suspensions of uncooked corn (maize) starch. The discovery of oligosymptomatic and asymptomatic siblings suggests that there are more persons with undiagnosed hepatic glycogen synthase deficiency.
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  • 19
    ISSN: 1432-1017
    Keywords: Key words Gallstone ; Cholesterol monohydrate crystals ; Phase separation ; Light scattering ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Phospholipid/cholesterol vesicles were solu-bilized by 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). Above 30 mol% cholesterol (Ch) in the lipid vesicles several remarkable changes of the solubilization process were observed. (i) Two modes of solubilization: The effective detergent to lipid ratio Rc(M) for the formation of mixed micelles decreased from Rc(M) = 43 ± 3 at low lipid concentrations, [L]≤ 0.15 mm, to Rc(M) = 2.4 ± 0.3 above [L] = 0.5 mm (40 mol% Ch, T = 20 °C). (ii) At subsolubilizing CHAPS concentrations, filamentous and helical microstructures were formed, similar to those which were observed in native and model bile. (iii) The number of observed fibers was about two orders of magnitude higher in the presence of the negatively charged lipids phosphatidylglycerol (PG) and phosphatidic acid (PA) compared to the zwitterionic phosphatidylcholine (PC). Fiber formation began after 16–18 h using PG and PA compared to 3–4 days in the presence of PC. Screening of the charged lipids by NaCl effectively reduced the formation of fibers. Assuming binding of Na+ to the charged lipid aggregates, an intrinsic binding constant Kint = 0.6 M–1 was determined by applying the Gouy-Chapman theory. After the addition of CHAPS to PG/Ch vesicles, a fast initial solubilization of the vesicles (〈1 min) to mixed micelles (rh = 2.3 ± 0.2 nm) and small vesicles (rh = 23 ± 1 nm) was observed, followed by an intermediate period of 2 h, after which the formation of fibers occurred (〉15 h). The microstructures are visualized by darkfield and electron microscopy. The method of vesicle solubilization is compared to the dilution of concentrated micellar solutions, which is usually applied to model bile systems.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 21 (1996), S. 293-302 
    ISSN: 1432-0789
    Keywords: Key words Ammonium excretion ; Azorhizobium caulinodans ; Auxine ; 2 ; 4-Dichlor-phenoxy-acetic acid ; Nitrogen fixation ; Paranodulation ; Rice ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rice seedlings developed nodule-like tumors (para-nodules) along primary and secondary roots when treated with the auxin 2,4-dichlor-phenoxy-acetic acid (2,4-D). Histologically, these tumors appeared as cancerous out-grown lateral-root primordes and were thus comparable with stem nodules of the legume Sesbania rostrata. Azorhizobium caulinodans (a diazotroph known as a specific endophyte of Sesbania rostrata) was introduced and became established inside rice para-nodules and in root tissues around tumor bases. The infection with A. caulinodans followed a typical “crack-entry” invasion at places where para-nodule tumors had emerged through the root cortex and epidermis. The bacteria settled with high cell densities in intercellular spaces of the induced tumors and betwen root cortical cells. Infection of plant cells took place both in the epidermis and in cortical tissue. Intracellularly established A. caulinodans was found inside the cytoplasm, surrounded by membrane-like structures. N2 fixation by tumor-inhabiting Azorhizobium sp. was increased at low O2 tensions (1.5–3 kPa) compared with an untreated control. Only a little activity remained at O2 tensions of 5 kPa and above. The present results confirm that root-tumor induction offers a suitable method of establishing diazotrophs endophytically in the roots of gramineous crops.
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  • 21
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    Biology and fertility of soils 21 (1996), S. 293-302 
    ISSN: 1432-0789
    Keywords: Ammonium excretion ; Azorhizobium caulinodans ; Auxine 2.4-Dichlor-phenoxy-acetic acid ; Nitrogen fixation ; Paranodulation ; Rice ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rice seedlings developed nodule-like tumors (para-nodules) along primary and secondary roots when treated with the auxin 2,4-dichlor-phenoxy-acetic acid (2,4-D). Histologically, these tumors appeared as cancerous out-grown lateral-root primordes and were thus comparable with stem nodules of the legume Sesbania rostrata. Azorhizobium caulinodans (a diazotroph known as a specific endophyte of Sesbania rostrata) was introduced and became established inside rice para-nodules and in root tissues around tumor bases. The infection with A. caulinodans followed a typical “crack-entry” invasion at places where paranodule tumors had emerged through the root cortex and epidermis. The bacteria settled with high cell densities in intercellular spaces of the induced tumors and between root cortical cells. Infection of plant cells took place both in the epidermis and in cortical tissue. Intracellularly established A. caulinodans was found inside the cytoplasm, surrounded by membrane-like structures. N2 fixation by tumor-inhabiting Azorhizobium sp. was increased at low O2 tensions (1.5–3 kPa) compared with an untreated control. Only a little activity remained at O2 tensions of 5 kPa and above. The present results confirm that root-tumor induction offers a suitable method of establishing diazotrophs endophytically in the roots of gramineous crops.
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  • 22
    ISSN: 1432-1076
    Keywords: Key words Rhizomelic ; chondrodysplasia punctata ; Dihydroxyacetonephosphate-acyl-transferase ; Electron microscopy ; Peroxisomes ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rhizomelic chondrodysplasia punctata (RCDP) is clinically characterized by symmetrical shortening of the proximal limbs, contractures of joints, a characteristic dysmorphic face, and cataracts. In the classical form an impairment of several peroxisomal functions and enzymes (plasmalogen synthesis, phytanic acid oxidation, 3-oxoacyl-CoA thiolase) has been repeatedly shown. Recently a variant involving only the peroxisomal dihydroxyacetonephosphate acyltransferase (DHAP-AT) has been described. We present a patient with isolated DHAP-AT deficiency and all clinical, radiological, and pathological features of classical RCDP. For the first time, microscopy and immunocytochemistry of hepatocytes could be performed. Conclusion In contrast to studies on classical rhizomelic chondrodysplasia punctata which have shown enlarged peroxisomes in numbers varying from hepatocyte to hepatocyte, the peroxisomes in our patient seem to be normal in size, number and shape.
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  • 23
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    Archives of microbiology 166 (1996), S. 357-360 
    ISSN: 1432-072X
    Keywords: Key wordsEscherichia coli ; Capsule ; Serotype ; Edema disease ; Electron microscopy ; Cell adhesion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fine structure of the cell surface of seven enterotoxemic Escherichia coli (ETEEC) O139:K12 strains isolated from piglets with edema disease were examined electron microscopically using both the negative-staining method and the freeze-substitution fixation method. Densely packed, fine fibers were observed; they consisted of a capsule layer approximately 25 nm thick around the cell surfaces of strains 107/86, IW-2, ED-3, ED-43, and ED-61, all of which have a capacity to adhere strongly to HEp-2 cells. In contrast, no such structure was observed on the surface of strains RK-O139 or ED-1, both of which adhere only weakly to HEp-2 cells. These results suggest that the capsule structure might be associated with the ability to adhere to HEp-2 cells and, as a result, also potentially play some role in ETEEC infection.
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  • 24
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    Bioscience reports 16 (1996), S. 159-187 
    ISSN: 1573-4935
    Keywords: Electron microscopy ; photosystem II ; thylakoid membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This review covers the recent progress in the elucidation of the structure of photosystem II (PSII). Because much of the structural information for this membrane protein complex has been revealed by electron microscopy (EM), the review will also consider the specific technical and interpretation problems that arise with EM where they are of particular relevance to the structural data. Most recent reviews of photosystem II structure have concentrated on molecular studies of the PSII genes and on the likely roles of the subunits that they encode or they were mainly concerned with the biophysical data and fast absorption spectroscopy largely relating to electron transfer in various purified PSII preparations. In this review, we will focus on the approaches to the three-dimensional architecture of the complex and the lipid bilayer in which it is located (the thylakoid membrane) with special emphasis placed upon electron microscopical studies of PSII-containing thylakoid membranes. There are a few reports of 3D crystals of PSII and of associated X-ray diffraction measurements and although little structural information has so far been obtained from such studies (because of the lack of 3D crystals of sufficient quality), the prospects for such studies are also assessed.
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  • 25
    ISSN: 1432-2307
    Keywords: Acinar cell carcinoma ; Fetal pancreas ; Electron microscopy ; Fibrillary inclusion ; Rough endoplasmic reticulum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a case of pancreatic acinar cell carcinoma which contained a large number of pleomorphic inclusions with fibrillary internal structures and mature zymogen granules. To clarify the significance of fibrillary inclusions in the differentiation of acinar cells of the pancreas, we further investigated fetal pancreases (gestational weeks 16, 17, 19, 20 and 28). We found two types of inclusions: type A, corresponding to fibrillary inclusion of neoplastic acinar cells, was observed only in a 19-week fetus; type B showed a homogeneous density similar to that of zymogen granules. Type B was observed in all the fetuses after the 17th gestational week. Although the type A inclusion might be generated throught a different mechanism than the type B inclusion, the appearance of a large number of fibrillary inclusions in neoplastic acinar cells may represent a transient form of zymogen granule.
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  • 26
    ISSN: 1432-2307
    Keywords: Alveolar adenoma ; Lung neoplasms ; Flow cytometry ; Electron microscopy ; Proliferating cell nuclear antigen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Alveolar adenoma of the lung is a poorly characterized, uncommon pulmonary lesion with proliferation of alveolar epithelium and septal mesenchyme. We describe the electron microscopy, immunohistochemistry and DNA flow cytometry in a case of alveolar adenoma in a 55-year-old woman. Alveolar adenoma appears to be a distinct benign neoplasm of the alveolar structures. Our findings further suggest that it is not a precursor of bronchioloalveolar carcinoma or other type II pneumocyte lesions of presumed malignant potential.
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  • 27
    ISSN: 1432-0878
    Keywords: Key words: Electrocyte ; Intermediate filaments ; Desmin ; Cytoskeleton ; Electron microscopy ; Electrophorus electricus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Desmin protein is an abundant constituent of the intermediate filaments in the electrocytes of the electric organ of the electric eel Electrophorus electricus. Polyclonal antibodies were raised against purified desmin from the electric organ and used for immunolabeling of the protein in reconstituted filaments. In thick sections of the main electric organ that has been stained with fluorescein-labeled desmin-specific antibodies, light microscope revealed a diffuse meshwork of desmin filaments dispersed in the cytoplasm of electrocytes. In the region under the membrane, the immunostaining was slightly more intense than elsewhere. The meshwork of intermediate filaments composed of desmin was examined by electron microscopy of the main electric organ. Immuno-gold labeling demonstrated a widespread meshwork of desmin filaments in the cytoplasm and in close association with the plasma membrane. These observations suggest that intermediate filaments play a role in the maintenance of the morphology of electrocytes and, as an intracellular meshwork spanning the width of the cell, they may contribute to the organization of the intracellular compartments.
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  • 28
    ISSN: 1432-0878
    Keywords: Key words: Innervation ; Heart ; Intracardiac neurone ; Nitric oxide ; Immunocytochemistry ; Electron microscopy ; Rat (Sprague Dawley) ; Guinea-pig (Dunkin Hartley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The nitric oxide synthase-immunoreactivity and NADPH-diaphorase activity of intracardiac neurones in the rat and guinea-pig was studied at the ultrastructural level. While some nitric oxide synthase-containing intracardiac neurones were very heavily labelled, with electron-dense immunoprecipitate distributed throughout the neuronal cell bodies and their processes, most of the labelled neurones exhibited a lighter and more patchy distribution of nitric oxide synthase-immunoreactive material. Synapses made by nitric oxide synthase-negative nerve fibres with labelled intracardiac neurones were seen. Conversely, many nitric oxide synthase-containing nerve fibres that made synaptic contacts with unlabelled intracardiac neurones were also observed. Some small granule-containing cells were nitric oxide synthase-immunoreactive and were associated with unlabelled nerve terminals, while non-immunoreactive small granule-containing cells that were innervated by nitric oxide synthase-immunoreactive nerves were also seen. Small patches of osmiophilic electron-dense material were observed in the cytoplasm of NADPH-diaphorase-positive intracardiac neurones. This is the first description of the ultrastructural distribution of nitric oxide synthase-immunoreactivity and NADPH-diaphorase activity in a subpopulation of intracardiac neurones of rat and guinea-pig heart and provides further evidence in support of a role for nitric oxide in the local control of the heart by intrinsic neurones.
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  • 29
    ISSN: 1432-0878
    Keywords: Key words: Ocellus ; Photoreceptor cells ; Retinal degeneration ; Subrhabdomeric cisternae ; Electron microscopy ; Immuno-electron microscopy ; Phosphatidylinositol transfer protein ; Drosophila melanogaster (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We studied the structure of ocellar photoreceptor cells of Drosophila melanogaster, particularly the subrhabdomeric cisternae which our previous studies have shown to be essential structures for turnover of photoreceptive membranes in compound eyes. Each ocellus contained elongated photoreceptor cells with rhabdomeres positioned distally. In the subrhabdomeric regions, endocytotic invaginations were frequently observed, suggesting active turnover of photoreceptive membranes. In the vicinity of the photoreceptive microvilli, membranous structures similar to the subrhabdomeric cisternae in compound eyes were observed. These membranous structures were immunopositive for the rdgB protein, a phosphatidylinositol transfer protein that is localized to the subrhabdomeric cisternae in compound eyes. The ocellar photoreceptor cells of the retinal degeneration mutants (rdgA,B) were also studied. In these mutants, retinal degeneration has been reported to start, in compound eyes, with the disappearance of the subrhabdomeric cisternae. We found that the ocellar subrhabdomeric cisternae also disappear during the initial stage of retinal degeneration. From these observations, we conclude that the mechanism of photoreceptive membrane turnover in ocellar photoreceptor cells involves the rdgB and probably the rdgA proteins which are associated with subrhabdomeric cisternae, as is the case for photoreceptive membrane turnover in compound eyes.
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  • 30
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    Cell & tissue research 284 (1996), S. 125-142 
    ISSN: 1432-0878
    Keywords: Key words: Chordotonal organ ; Scolopidium ; Mechanoreceptor ; Sensilla ; Electron microscopy ; Phylogenesis ; Teleogryllus commodus (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. More than 50 chordotonal sensilla, or scolopidia, embedded entirely in the integument were found in each side of the genital chamber wall in the female cricket, Teleogryllus commodus. Their cell bodies lie among the epidermal cells, and the tips of their dendrites terminate in the cuticle. About half of them contain two sensory cells (two-cell scolopidium), the others only one (one-cell scolopidium). The sensory cell in the one-cell scolopidium is the type-1 cell. In the two-cell scolopidium one is type-1 and the other type-2. Regardless of the number of sensory cells, they are all amphinematic. In the two-cell scolopidium only the type-2 dendrite, rich in microtubules, penetrates into the cuticle, bifurcates and terminates in the tube enclosed by an attachment cell; the type-1 never extends into the cuticle. On the other hand, the type-1 cell in the one-cell scolopidium projects its apex into the cuticle. The unique topography and structure of these scolopidia lead to the following hypothesis about the phylogenetic relationship between the scolopidia and other kinds of sensilla: the type-1 scolopidial sensory cell buried in the integument may be the original model, which through the loss of the long regular axoneme has given rise to type-2 cells. Modification of the apical region, the tubular body or ramification, may have lead to the cuticular sensilla corresponding to the development of the cuticular apparatus, and the scolopidia may have been withdrawn into the body cavity to form ordinary chordotonal organs.
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  • 31
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    International journal of legal medicine 109 (1996), S. 147-149 
    ISSN: 1437-1596
    Keywords: Gunshot wounds ; Momentum ; Physics ; Wound ballistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract Shooting incidents are often portrayed as resulting in a sometimes violent backwards displacement of the victim. This opinion is also not infrequently held by expert witnesses. The physical force responsible for this would be momentum (mass x velocity). The physics of momentum in ballistic injury is explained in detail. The maximum momentum transferred from different small arms projectiles including large calibre rifles and a 12-gauge shotgun only results in a backwards motion of a 80 kg target body of 0.01–0.18 m/s, which is negligible compared to the velocity of a pedestrian (1–2 m/s). Furthermore, counterbalance is constantly maintained by neurophysiological reflexes. So the effect of the momentum transferred from the missile is virtually zero and there is no backwards motion of the person shot. Empirical evidence verifying these calculations can be obtained from hunting big game, from human gunshot victims and from a video documentary demonstrating the lack of any backwards motion of a person wearing body armour after hits from a centre fire rifle. So the alleged backwards hurling of a person shot is nothing but a myth which should be refuted not only because it is incorrect but also because it can result in miscarriages of justice.
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  • 32
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    Methods in cell science 18 (1996), S. 15-18 
    ISSN: 1573-0603
    Keywords: Angiogenesis ; Endothelial cells ; Angiogenesis analysis ; Electron microscopy ; Cell culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Determination of the structural characteristics of angiogenesis requires a procedure protective of the forming vascular fibers and the endothelial cell monolayer exhibiting cord formation. This report describes in situ fixation of angiogenic cultures in 96-well plates and the subsequent double embedding processing for electron microscopy. Cross sections of the monolayer are obtained without damage of the incipient capillaries.
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  • 33
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    European archives of oto-rhino-laryngology and head & neck 253 (1996), S. 205-213 
    ISSN: 1434-4726
    Keywords: Nasal neuropeptides ; Perennial rhinitis ; Mucosal glands ; Immunofluorescence ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study morphological effects on the nasal and sinus mucosa, New Zealand White rabbits underwent either unselective, regional sectioning of sensory and parasympathetic nerve branches or topical treatment of the mucosa with capsaicin. Ten days after treatment, mucosal specimens were analyzed by light and electron microscopy. Immunohistochemistry was used to evaluate neuropeptides present, in particular substance P, calcitonin gene-related peptide, vasoactive intestinal peptide and neuropeptide Y. In surgically denervated rabbits, mucosal glands were found to be enlarged and contained an increased number of zymogen granules having a bipartite substructure. Topical capsaicin application caused localized epithelial changes in the sinus mucosa and maxilloturbinal region of the nose, including clotting of cilia and an increased number of goblet cells. Reduced amounts of all neuropeptides investigated were found in the surgically denervated animals, while topical capsaicin treatment had only marginal effects on the mucosal neuropeptide content. The morphological changes observed after surgical denervation suggest an imbalance between neural stimulation and secretory capacity of the mucosal glands. These findings could explain the difference in clinical effect noted between sectioning of the vidian nerve and topical treatment with capsaicin in patients with perennial rhinitis.
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  • 34
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    Berichte der deutschen chemischen Gesellschaft 129 (1996) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 35
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 11-13 
    ISSN: 0009-2940
    Keywords: Triferriophosphane sulfide ; Metallothioxophosphorane ; PS complex ; Spiro compounds ; Decarbonylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The P-H-functional triferriophosphonium salts [{CpFe-(CO)2}3PH]2FeCl4 (1) and [{μ-CO(CpFeCO)2}{CpFe-(CO)2}PH]2FeCl4 (4) are easily deprotonated by DBU to the corresponding unstable triferriophosphanes 2, 5, which subsequently are oxidized by sulfur to the triferriophosphane sulfides {CpFe(CO)2}3P=S (3) and {μ-CO(CpFeCO)2}{CpFe-(CO)2}P=S (6), respectively. The photolysis of 3 results only in its decomposition by elimination of [CpFe(CO)2]2, whereas the photolysis of 6 cleaves off one CO ligand to give the new spiro compound (CpFeCO)(μ-η2-PS){μ-CO(CpFeCO)2} (7), where the P=S unit is η2-bonded to the 15-electron CpFeCO fragment, and the phosphorus atom bridges two 17-electron fragments. Compound 7 shows a new coordination mode of the PS unit where sulfur is also bound to one of the metal atoms. Compounds 6 and 7 can be regarded as first examples of a new class of PS complexes of transition metals. All compounds were characterized by IR, 31P{1H}- and 13C{1H}-NMR spectroscopy as well as mass spectrometry; for 6 the X-ray analytical data are given.
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  • 36
    ISSN: 0009-2940
    Keywords: Triazacyclohexanes ; Chromium complexes ; Amides ; Hexamethyldisilane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of N,N′,N′′-trimethyl-1,3,5-triazacyclohexane chromium trichloride ((Me3TAC)CrCl3, 1) with LiN(SiMe3)2 or NaN(SiMe3)2 in petroleum ether yields nearly quantitatively [Cr{N(SiMe3)2}3] (2) with loss of the Me3TAC ligand. Compound 2 could be crystallized from hexamethyldisilane as [Cr{N(SiMe3)2}3] · (Me6Si2)0,5 which allowed the refinement of the X-ray crystal structure in the trigonal space group P-31c (no. 163) (a = 16.012(3) Å, c = 8.4796(12) Å, V = 1882.8(6) Å3, Z = 2) without severe disorder.
    Additional Material: 3 Ill.
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  • 37
    ISSN: 0009-2940
    Keywords: Glyceraldehyde ; Ligands, tridentate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of seven chiral, tripodal N,O,S and N,N,O ligands were prepared in which N stands for a secondary amine or imidazole donor, O for a phenol, and S for a thioether or thiol metal-binding group. Key steps are (1) the construction of ortho-hydroxyacetophenones bearing the phenolic binding group and either a thioether, a protected thiol or an imidazole substituent in the α-position, and (2) subsequent reductive amination with a primary amine. The modular synthesis allows a rapid construction of a variety of structurally related ligands. In three cases, the enantiomers of the racemic products could be separated after condensation with (R)-glyceraldehyde acetonide as chiral auxiliary. The relative configurations of the cyclic N,O- and N,N-acetals thus obtained were established by NOE spectroscopy. X-ray structural analysis of two crystalline N,O- and N,N-acetals allowed the assignment of absolute configurations. Hydrolysis of the dia-stereomerically pure acetals afforded the enantiomerically pure ligands in high yield. By comparison of their CD spectra, absolute configuration could also be assigned to the third pair of enantiomerically pure ligands.
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  • 38
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 85-89 
    ISSN: 0009-2940
    Keywords: Rhodium complexes, chiral ; Hydrogenation ; Bisolefins ; Thermodynamic stability ; Kinetic control ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Asymmetric hydrogenations of prochiral olefines by means of chiral rhodium(I) complexes of the type [Rh(L)(PP*)]A (L = COD, [(Z,Z)-cycloocta-1,5-diene], or NBD (norborna-2;5-diene), PP* = chiral bisphosphane forming seven-membered chelate rings, A = anion like BF4-) are often associated with induction periods caused by partial blocking of the catalyst. NBD complexes are hydrogenated faster than the corresponding COD complexes. Catalytic hydrogenation of COD/NBD mixtures and the determination of the ratio of the Michaelis constants showed that the steady-state concentration of the COD complex under hydrogen is higher than that of the NBD complex. However, under argon the NBD complex predominates owing to its higher thermodynamic stability compared with that of the COD complex as determined by 31P-NMR spectoscopy. This complete reversion of the ther-modynamically determined ratios of COD to NBD complex concentration under hydrogenation conditions was proven by means of UV/Vis spectroscopy.
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  • 39
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 233-235 
    ISSN: 0009-2940
    Keywords: Positional selectivity ; Bromination ; Halogen/lithium exchange ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Bromo-3,5-bis(trifluoromethyl)benzene (1) can be selectively prepared by treatment of 1,3-bis(fluoromethyl)benzene with N,N'-dibromo-5,5-dimethylhydantoin in strongly acidic media. A number of synthetically useful reactions via 3,5-bis(trifluoromethyl)phenylmagnesium, -lithium, and -copper intermediates were accomplished.
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  • 40
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 253-257 
    ISSN: 0009-2940
    Keywords: Lithiated phosphane imines ; Phosphane imines, lithiated ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithiated Phosphane Imines. Synthesis and Crystal Structures of [LiCH2PMe2NSiMe3]4 and [LiCMe2P(iPr)2NSiMe3]2The title compounds were prepared by the reaction of Me3-SiNPMe3 and Me3SiNP(iPr)3, respectively, with n-Butylli-thium at 20°C in n-hexane solution. They form white, moisture- and oxygen-sensitive crystals, which were characterized by IR spectroscopy and by crystal structure determinations. - [LiCH2PMe2NSiMe3]4 (1) forms a Li4 tetrahedron, the faces of which are capped with CH2 groups with average Li-C distances of 233 and 251 pm, while the nitrogen atoms occupy the corners of the Li4 tetrahedron. - [LiCMe2P(iPr)2N-SiMe3]2 (2) forms molecules of symmetry C2 in which the lithium atoms have coordination number three by two carbon atoms and one nitrogen atom with Li-C distances of 215.2 and 237.9 pm and Li-N of 192.8 pm.
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  • 41
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 269-273 
    ISSN: 0009-2940
    Keywords: Organometallic polymers ; Coupling reactions ; Butadiynyl complexes ; Cobalt compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 3a starting from compound 1 is described. Copper-catalyzed oxidative coupling of 3b under Hay conditions gives the novel polymer 9 with octatetrayne-cyclobutadiene units.
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  • 42
    ISSN: 0009-2940
    Keywords: Bis[2.2]metacyclophanes ; Stilbenes ; π-π Interaction ; Tricarbonylchromium complexes ; Charge-transfer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (E)-8,8′-(Ethene-1,2-diyl)bis(5-tert-butyl[2.2]metacyclo-phane) (2) was obtained from a McMurry reaction of 5-tert-butyl-8-formyl[2.2]metacyclophane (1). Irradiation of 2 with a high-pressure mercury lamp gave the corresponding (Z) isomer 3. X-ray crystallographic analyses of 2 and 3 show a certain degree of twisting of the bond connecting the meta-cyclophane unit and the central π system due to steric crowding. UV spectra of 2 and 3 and of the charge-transfer complexes [2/TCNE] and [3/TCNE] allow for a discussion of π-π interaction between the central stilbene subunit and the outer benzene rings of the metacyclophane units. Bis[2.2]meta-cyclophanes 2 and 3 reacted regioselectively with hexacar-bonylchromium on the outer benzene rings giving 1:1 and 1:2 complexes 9-14 with tricarbonylchromium. No 1:3 and 1:4 complexes formed due to steric restrictions. Analysis of UV spectral data of the complexed [2.2]metacyclophanes was performed for an indication of π-π interactions in the complexes.
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  • 43
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 283-287 
    ISSN: 0009-2940
    Keywords: Self-assembling frameworks ; Thermal stability ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Here we report on investigations that have revealed for the first time that the Cs+ ion templates the same metal germanium sulfide open-framework as (CH3)4N+ (TMA+), and that metal complexing agents enhance crystal size by at least two orders of magnitude. The synthesis, structures and thermal properties of Cs2FeGe4S10 ·× H2O and TMA2FeGe4S10 are also described. Both have 3D zinc blende-type open-framework structures. These materials have the same connectivity as TMA2MnGe4S10. The tetrahedral sites in the lattice are alternately substituted by pseudo-tetrahedral Fe2+ and adamantanoid Ge4S104- building blocks, covalently linked together by Fe(μ-S)Ge bridge bonds, to give a tetragonal unit cell. The charge-balance of the anionic framework [Fe-Ge4S10]2- is maintained by either Cs+ or TMA+ ions in the cavity spaces. Synthesis of these materials demonstrates an interesting example of a self-assembly process in which a 3D framework is built from molecular precursors. Water adsorption-desorption cycling from room temperature to 200 °C reveals framework flexibility between larger and smaller tetragonal unit cell 14 isotypes. The compound TMA2FeGe4S10 is stable in nitrogen at 350 °C and under vacuum at 450 °C. The corresponding temperatures for Cs2FeGe4S10 are 530 °C and 630°C; it is stable on cooling to room temperature under vacuum, and after subsequent exposure to air. Six hundred thirty degrees celsius is the highest recorded temperature at which the integrity of a non-oxide framework has been maintained. The framework stability and flexibility of “all-inorganic” Cs2FeGe4S10 provides an encouraging example for researchers interested in developing sulfide-based framework materials with practical applications.
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  • 44
    ISSN: 0009-2940
    Keywords: Gold complexes ; Silver complexes ; Palladium complexes ; S-Donor ; Thiones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: AgClO4 reacts with bidentate ligands 2-(methylthio)pyridine (SMepy) or complexes PPN[Au(Spy)2] [PPN = N(PPh3)2, HSpy = pyridine-2(1H)-thione) or PPN[Au(Sbz)2] (HSbz = benzoxazole-2(3H)-thione), themselves acting as ligands, to give dinuclear complexes [Ag2(μ-SMepy)2](ClO4)2 (1), [AgAu(μ-Spy)2] (2), or [AgAu(μ-Sbz)2] (3), respectively. By treating 1 with [AuCl(tht)] (tht = tetrahydrothiophene), [Au(SMepy)(tht)]ClO4 (4) is obtained which, in turn, reacts with SMepy to give [Au(SMepy)2]ClO4 (5). Similarly, [PdCl2(NCPh)2] reacts with SMepy in 1:1 molar ratio to give [Pd2Cl2(μ-Cl)2(SMepy)2] (6) which reacts with SMepy in 1:2 molar ratio to give [PdCl2(SMepy)2] (7). On the other hand, HSpy reacts with Ag2CO3 to give [Ag2(μ-Spy)2] (8), and (SMepyH)ClO4 reacts with [Au(acac)PPh3] (acacH = acetyl-acetone) to give [Au(SMepy)PPh3]ClO4 (9).
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  • 45
    ISSN: 0009-2940
    Keywords: Histidine peptides ; Zinc complexes ; EXAFS analysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: One tripeptide, five tetrapeptides, and one pentapeptide, all containing His-Xn-His sequences and being blocked at the N and C termini with acyl and amide functions, respectively, were synthesized by solid-phase methods. With one exception their reaction with various zinc salts led to the precipitation of 1:1 (zinc/peptide) complexes. Analytically pure compounds were obtained from zinc tetrafluoroborate and His-Gly-His (1), from zinc chloride (resp. bromide) and His-Gly -Gly-His (2), His-Ala-Gly-His (3), His-Leu-Gly-His (4), His-Pro-Gly-His (5), and His-Pro-Asn-His (6) as well as from zinc sulfate and His-Leu-Gly-His (4) and His-Ala-Pro-Gly-His (7). 1H-NMR data, when available, indicate the coordination of both histidine units to zinc in all cases. The low solubility of the complexes points to their polymeric nature. The only 1:2 (zinc/peptide) complex in this series was obtained from zinc perchlorate and His-Gly-Gly-His (2). An EXAFS study revealed that it contains zinc symmetrically coordinated by four histidine imidazole ligands. Based on the available information it is proposed that all complexes are one-dimensional polymers containg [-Zn-His-Xn-His-Zn-]x backbones.
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  • 46
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 47
    ISSN: 0009-2940
    Keywords: Silanediols ; Silanetriols ; Siloxanes ; Hydrogen bonding ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The silanediols RN(SiMe3)Si(OSiMe3)(OH)2 (R = 2,4,6-Me3C6H2 4, 2,6-Me2C6H3 5, and 2,6-iPr2C6H3 6) were prepared by the reactions of the respective silanetriols RN(SiMe3)-Si(OH)3 1 - 3 with SiMe3Cl in THF/hexane. Silanetriol 1 in CH2Cl2/hexane solution converts over a period of 4 weeks into the silanediol (2,4,6-Me3C6H2)N(SiMe3)Si(OSiMe2 R)-(OH)2 [R = CH2(2-NH2-3,5-Me2C6H2)] (7). Compounds 4 - 7 were characterized by means of mass, IR and NMR (1H and 29Si) spectroscopy. Additionally, the molecular structures of 4 and 7 were determined by single-crystal X-ray diffraction studies. Compound 4 forms O — H…O hydrogen-bonded tetramers in the solid state. A nine-membered ring formed by an intermolecular O—H…N hydrogen bond is found in the solid-state structure of 7.
    Additional Material: 3 Ill.
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  • 48
    ISSN: 0009-2940
    Keywords: Iridium complexes ; Stibane complexes ; Hydrido complexes ; Ethene complexes ; Ligand displacement reactions ; Alkyne-to-vinylidene rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of [IrCl(C8H14)2]2 (2) with SbiPr3 in the presence of H2 yields the dihydridoiridium(III) complex cis,mer-[IrH2Cl(SbiPr3)3] (3) which on treatment with CO and with HC≡CR (R = Ph, CO2Me) affords the octahedral derivatives [IrH2Cl(CO)(SbiPr3)2] (4) and [IrHCl(C≡CR)(SbiPr3)3] (5, 6), respectively. The stibane ligand trans to hydride in 5 and 6 is rather labile and, therefore, 5 and 6 react with pyridine to give [IrHCl(C≡CR)(py)(SbiPr3)2] (7, 8). Five-coordinate bis-(stibane)iridium(I) complexes [IrCl(C2H4)2(SbR3)2] (10-12) were prepared from [IrCl(C2H4)2]2 (9) and four equiv. of SbR3 (R = iPr, Me, Ph). The X-ray crystal structural analysis of 10 reveals a distorted trigonal-bipyramidal geometry around the metal center with one stibane ligand and the two olefinic ligands in the equatorial plane. Compound 10 reacts with NaC5H5 to yield [C5H5Ir(C2H4)(SbiPr3)] (13) and with different alkynes by partial or complete displacement of the ethene ligands to give trans-[IrCl(PhC≡CPh)(SbiPr3)2] (14), [IrHCl(C≡CTol)(C2H4)(SbiPr3)2] (15), and trans-[IrCl-{=C=C(SiMe3)R}(SbiPr3)2] (16, 17), respectively.
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  • 49
    ISSN: 0009-2940
    Keywords: Azolylborane adducts ; Boron-imidazole adducts ; Boron-pyridine adducts ; Protic-hydric interactions ; Protic-fluoride interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation, NMR and X-ray diffraction studies of a series of azolylboron hydrides derived from pyrrole, indole, and carbazole coordinated with tetrahydrofuran, pyridine, and imidazole are reported. The azolyl substituents are very electroattractive leading to an acidic boron atom which strongly coordinates with the Lewis bases. The stabilization of the =BH2=groups against disproportionation could be explained in terms of the interactions found between the acidic hydrogen atoms of the heterocycles (C=Hδ+ acceptor) and the hydrides (B=Hδ- donors).
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  • 50
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 51
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 485-487 
    ISSN: 0009-2940
    Keywords: Dimetallations ; Insertions ; Rhenium ; Isothiocyanates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecules containing dimetallated hydrocarbyl groupings are of great chemical interest[1-3]. These groupings often represent intermediates in important catalytic processes[4]. Recently, we have shown that substituted dimetallated olefins can be formed by alkyne insertion into the metal-metal bonds of certain dinuclear complexes[2,5]. Complexes having dimetallated hydrocarbyl groups combined with heteroatoms are quite rare[6]. Herein is described the formation of a dimetallathioimidate grouping by the insertion of an organic isothiocyanates into an unsupported metal-metal bond. Organic isothiocyanates are useful reagents in organic synthesis[7], but the organometallic chemistry of these molecules is not yet well developed[8].
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  • 52
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 521-525 
    ISSN: 0009-2940
    Keywords: Liquid crystals ; Siloxanes ; Phase behaviors ; Defined topology ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that supermolecules with a tetrahedral symmetry and appropriate side-chains exhibit liquid-crystalline phase behaviour. The use of an optimised hydrosylation reaction allows for the synthesis of materials that have four mesogenic groups attached to a siloxane core, where the conformation and the configuration are unambiguous. The materials show low glass transition temperatures and, depending on the spacer length, complex liquid-crystalline morphologies.
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  • 53
    ISSN: 0009-2940
    Keywords: Iron and ruthenium complexes ; Water soluble complexes ; Sulfur ligands ; X-ray structure analyses ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In search of water soluble transition metal complexes with sulfur dominated coordination spheres that model key reactions of nitrogenases, the benzenedithiol derivatives ‘CO2HS2’-H2 (1) and ‘CO2Me-S2’-H2 (2) were synthesized as precursors for multidentate sulfur ligands. The template alkylation of 2 by C2H4Br2 at [Fe(CO)2] fragments yielded a mixture of two diastereomeric C2 symmetrical [Fe(CO)2(‘CO2Me-S4’)] complexes (4a and 4b), which were separated by crystallization. The hydrolysis of the mixture of the diastereomers 4a and 4b led to the isomerically pure tetradentate thioether thiol ligand ‘CO2Me-S4’-H2 (5) proving the regioselectivity of the template alkylation of the asymmetrical dithiol 2. The C1 symmetrical [Fe(‘CO2Me-S2’)2]2- anion is an intermediate of the template alkylation and was isolated as (AsPh4)2 [Fe(‘CO2Me-S2’2] (11), 4a, 5 and 11 were characterized by X-ray structural analysis. Saponification of the methyl ester groups of 5 yielded ‘CO2H-S4’-H2 (7). Treatment of 7 with FeCl2 · 4 H2O in the presence of CO and LiOMe gave a mixture of two C2 symmetrical and water soluble diastereomers of Li2[Fe(CO)2(‘CO2-S4’)] (8). Upon treatment with [RuCl2 (PPh3)3] 7 yielded isomerically pure [Ru(PPh3)2-(‘CO2H-S4’)] (9). 9 also exhibits C2 symmetry and could be reversibly deprotonated to form the water soluble complex K2[Ru(PPh3)2 (‘CO2-S4’)] (10). Treatment of (NBu4)2 (‘CO2MeS2’) with “Ru(NO)Cl3” led to isomerically pure (NBu4)[Ru(NO)(‘CO2Me-S2’)2] (12).
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  • 54
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 833-836 
    ISSN: 0009-2940
    Keywords: Oxotitanium(IV) porphyrinate ; Peroxotitanium(IV) porphyrinate ; Photochemistry ; Singlet oxygen ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of oxotitanium(IV) meso-tetrakis(2,3,4,5,6-pentafluorophenyl)porphyrinate O=Ti(TPPF20) (1), oxotitanium(IV) meso-tetrakis(2,6-difluorophenyl)porphyrinate O=Ti-(TPPF8) (3), and oxotitanium(IV) meso-tetrakis(2,6-dichlorophenyl)porphyrinate O=Ti(TPPCl8) (5) from titanium tetrachloride and the corresponding porphine are described. The structure of 1 was determined by single-crystal X-ray diffraction. The reaction of oxotitanium porphyrinates with aqueous hydrogen peroxide leads to the corresponding light-sensitive peroxotitanium(IV) complexes: Ti(O2)(TPPF20) (2), Ti(O2)-(TPPF8) (4), Ti(O2)(TPPCl8) (6). All complexes are efficient and stable photosensitizers for the generation of singlet oxygen.
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  • 55
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 837-839 
    ISSN: 0009-2940
    Keywords: Boron compounds ; Silaboranes ; Dihetero-closo-borane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of 3 equivalents of KH · BEt3 to [Me3NH][Me-SiB10H12] followed by addition of one equivalent of SnCl2 or SbI3 affords the stanna-sila-closo-borate(1-) 3 and stiba-sila-closo-borane 4, respectively. [MePh3P] · 3 crystallizes in the orthorhombic space group P212121.
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  • 56
    ISSN: 0009-2940
    Keywords: Amides ; Pyrrolyl complexes ; Chelate complexes ; Transition-metal complexes ; Metallacycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intramolecularly Stabilized Metal Amides: 2-(Dimethylaminomethyl)pyrrolyl Complexes of Titanium(III), Vanadium(III), Chromium(III), Cobalt(II) and Nickel(II)By the metallation of 2-(dimethylaminomethyl)pyrrol (HL) with butyllithium the lithium pyrrolide LiL (1) was obtained. The reactions of 1 with TiBr3 · 3 THF, VBr3 · 3 THF, CrBr3 · 3 THF, CoBr2 · 2 THF, and NiBr2 · 1.67 THF result in the formation of the 2-(dimethylaminomethyl)pyrrolyl complexes of type ML3 (2-4), and ML2 (5, 6), respectively. The structures of these new compounds are discussed on the basis of magnetic and visible absorption measurements. An X-ray crystal structure determination of 4 reveals a strongly distorted octahedral environment of the chromium atom with facial arrangement of the ligands.
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  • 57
    ISSN: 0009-2940
    Keywords: Rhodium complexes ; Alkyne complexes ; Insertion reactions ; Alkyl isocyanides ; Metallacycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cyclopentadienyl complexes [C5H5Rh(RC≡CR′)(SbiPr3)] (5-8), which were prepared from trans-[RhCl-(RC≡CR′)(SbiPr3)2] (1-4) and NaC5H5 and which contain a labile Rh-SbiPr3 bond, reacted with CO and CNR″ (R″ = Me, tBu) to give the carbonyl and isocyanide derivatives [C5H5Rh(RC≡CR′)(CO)] (9-11) and [C5H5Rh(RC≡CR′)-(CNR″)] (12-16), respectively. On treatment of 12 (R = R′ = Ph; R″ = Me) with SbiPr3, the metallacyclobutene complex [C5H5Rh{κ2(C,C}-C( = NMe)CPh=CPh}(SbiPr3)] (17) was formed; it reacts with excess CNMe or CNtBu to yield the metallacyclopentenes [C5H5Rh{κ2(C,C)-C(=NMe)CPh=CPhC-(=NR)}(CNR)] (18, 19). Similar compounds 20-23 containing a five-membered RhC4 metallacycle were prepared either from [C5H5Rh(RC≡CR′)(SbiPr3)] (7, 8) or [C5H5Rh-(PhC≡CPh)(CNtBu)] (14) and excess isocyanide. The crystal and molecular structures of 17 and 18 (R = Me) have been determined.
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  • 58
    ISSN: 0009-2940
    Keywords: Phthalocyanines ; Porphyrins ; Lanthanide(III) compounds ; Macrocyclic ligands ; Double-decker complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of 5,10,15,20-tetra-4-pyridylporphyrin [(TPyP)H2] with europium(III) or gadolinium(III) acetylacetonate [Ln(acac)3 · nH2O] (Ln = Eu, Gd) in 1,2,4-trichlorobenzene produced Ln(acac)(TPyP), which reacted with dilithium phthalocyaninate [Li2(Pc)] to give Li[Ln(Pc)(TPyP)] in moderate yields. Upon exposure to air, solutions of these compounds converted slowly to the corresponding neutral complexes Ln(Pc)(TPyP). The new compounds were spectroscopically characterized.
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  • 59
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 937-944 
    ISSN: 0009-2940
    Keywords: Iron acyl complexes ; (Alkynyl)carbene ligand ; Cationic aminocarbene complexes ; Iron (2-methoxyvinyl)aminocarbene complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (Alkynoyl)iron complexes 1, Cp(CO)2Fe(O=CC≡CR) (R = CH3, Ph, SiMe3), were synthesized by applying a mixed anhydride procedure and transformed into the cationic methoxycarbene complexes 2, [Cp(CO)2 Fe(C(OMe)C≡CR)+]-[PF6-]. Primary amines H2NR′ react with the methoxycarbene complexes to furnish exclusively cationic aminocarbene complexes 3, [Cp(CO)2 Fe(C(NHR′)C≡CR)+][PF6-], or (2-methoxyvinyl)aminocarbene complexes 5. The spectroscopic properties of the new complexes are discussed. The (alkynyl)-aminocarbene complexes 3e and 3f were characterized by X-ray crystal structure analysis.
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  • 60
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 967-971 
    ISSN: 0009-2940
    Keywords: Phthalocyanines, sulphonated ; Diazadithiamacrocycles ; Pentanuclear complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal phthalocyanines (M = Cu, Ni, Co) 3-5 bearing four 16-membered diazadithia macrocycles at the peripheral positions were prepared. Detosylation with concentrated sulfuric acid afforded products containing both sulfonated groups on the aromatic rings of the macrocyclic substituents which are excellently soluble in water and donor sites for binding four CuII ions to give a pentanuclear complex.
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  • 61
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1379-1381 
    ISSN: 0009-2940
    Keywords: Thionitrosyl chloride ; Thiazyl chloride ; Neutralization-reionization mass spectrometry ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio MO calculations at the QCISD(T)/6-311++G(3df,2p) + ZPE level show that the thionitrosyl chloride ion, ClNS+•, is 36 kJ/mol more stable than the thiazyl chloride ion, NSCl+•, whereas neutral NSCl is 77 kJ/mol more stable than ClNS [IEa (ClNS) = 9.2 ± 0.3 eV, IEa (NSCl) = 10.5 ± 0.3 eV]. Mild flash-vacuum pyrolysis of the thiazyl chloride trimer (NSCl)3 followed by electron impact ionization resulted in the formation of [N,S,Cl]+• ions (m/z 81). The fragments observed in the CA spectrum of these ions indicate the formation of both NSCl+• and ClNS+• ions. A very weak recovery signal is observed in a neutralizationreionization experiment. This signal is tentatively assigned to the neutral thionitrosyl chloride.
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  • 62
    ISSN: 0009-2940
    Keywords: Gold ; Mercury ; Nitroaryl ; Transmetallation ; Biaryl ; C-C Coupling ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4-Butoxynitrobenzene reacts with [Hg(O2CCF3)2] and LiCl to give [Hg(R)Cl] [R = C6H3NO2-3, OnBu-6 (1)] which is symmetrized by Me4NCl to give [HgR2] (2), the crystal structure of which has been determined. The reaction of 2 with Me4N[AuCl4] affords Me4N[Au(R)Cl3] (3) by a facile transmetallation process. Complex 3 reacts with PPh3 (1:1) to give cis-[Au(R)(PPh3)Cl2] (4). The diaryl complex [-Ph-2)(R)Cl] (5) is obtained by reaction of 3 with [Hg-(C6H4N=NPh-2)2] through a second transmetallation reaction. Complex 5 and PPh3 (1:1) give [AuClPPh3] and the C-C coupling biphenyl RC6H4N=NPh-2 (6).
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  • 63
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1409-1419 
    ISSN: 0009-2940
    Keywords: Sulfenic acid anions ; Thiosulfinic acid anions ; Thiosulfonic acid anions ; Transition metal complexes ; Stereochemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and coordination chemistry of sulfenic, thiosulfinic, and thiosulfonic acid anions are reviewed. Different approaches, which yield the platinum(II) and ruthenium(II) complexes containing the anionic sulfur(0), sulfur(II), and sulfur(IV) oxid ligands, are described. The oxidative addition of thiosulfinates or N-sulfinyl phthalimides to platinum(0) complexes L2Pt(C2H4) [L = PPh3, 1/2 PPh2CH2CH2PPh2, 1/2 (R,R)-(-)-DIOP, 1/2 (C5H4PPh2)Fe(C5H4PPh2) leads to sulfenato complexes; those of N-thiosulfinyl phthalimidies or trisulfid 1-oxides afford the thiosulfinato complexes. Moreover, the reactions of CpRu(PPh3)(L)(SH) (L = CO, PPh3) with N-sulfinyl phthalimides forming the thiosulfinato moiety, are reported. The spectroscopic, structural and chemical properties of these complexes are discussed.
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  • 64
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1057-1059 
    ISSN: 0009-2940
    Keywords: (Alkynyl)carbene ligands ; Iron acyl complexes ; Cationic iron aminocarbene complexes ; Diels-Alder reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cationic iron (alkynyl)aminocarbene complexes [Cp(CO)2Fe(C(NHR)C≡CSiMe3][PF6], (R = C6H5, p-CH3C6H4) 1 derived from aromatic amines smoothly react with cyclopentadiene in dichloromethane to yield the cycloadducts 2. No reaction was observed for complexes derived from sterically demanding aliphatic amines, like L-alanine tert-butyl ester. For comparison, the alkynyl-substituted acyl iron compounds Cp(CO)2Fe(C=O)C≡C̊ (R = SiMe3, C6H5) 3 were investigated, requiring TiCl4 catalysis to undergo the cycloaddition reaction. The structures of the cycloadducts 4 were determined by X-ray crystallography.
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  • 65
    ISSN: 0009-2940
    Keywords: Nickel(0) ; Alkyne complexes ; Hydrogen bonds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of (cdt)Ni (cdt: cyclododeca-1,5,9-triene) with 2 equivalents of 2-methyl-4-trimethylsilyl-3-butyn-2-ol leads to the selective formation of the homoleptic complex (alkyne)4Ni3 (compound 3), which can be isolated in excellent yields. The solid-state structure of 3 exhibits three Ni centers, forming a bent Ni3 chain connected by two bridging alkynes. The other two alkynes are terminally coordinated. Additionally, the trimeric units are stabilized by three intramolecular hydrogen bonds. Two intermolecular hydrogen bonds connect the trimeric units to form a polymer rope. According to the 13C- and 1H-NMR spectra in THF the structure of the complex 3 in solution is very similar to that in the solid state. The reaction of 3 with some alkynediols and with 2,5,5-trimethylhex-3-yn-2-ol affords compounds of the type (alkyne)2Ni. Cot (cot: 1,3,5,7-cyclooctatetraene) converts 3 into [(cot)Ni]2, which in turn reacts with 2,5-dimethylhex-3-yne-2,5-diol to form the dimeric complex (alkyne)2Ni2(cot) 6. X-ray analysis of 6 reveals a very symmetrical structure in which cot connects both Ni(0) centers at opposite sides of the ring system.
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  • 66
    ISSN: 0009-2940
    Keywords: Sulfur dioxide ; Rhodium complexes ; Ether-phosphanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The SO2 coordination mode at the rhodium complex [ClRh(P∼O)()] (1) [ = η2(O,P)-chelated Cy2PCH2CH2OCH3 ligand; P∼O = =1(P)-coordinated] is controlled by the hemilabile ligand Cy2PCH2CH2OCH3 and shows a dependence on the polarity of the solvent. In polar organic solvents (e.g. acetone) the addition of sulfur dioxide results in the formation of a trigonal-pyramidal oriented SO2 group in [ClRh(η1-SO2)(P∼O)()] (2a). However, in nonpolar media (e.g. n-hexane) a trigonal-coplanar geometry of the SO2 unit in [ClRh(η1-SO2)(P∼O)2] (2b) is favored.
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  • 67
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    Berichte der deutschen chemischen Gesellschaft 129 (1996) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 68
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1475-1482 
    ISSN: 0009-2940
    Keywords: Allenylidene complexes ; Alkynyl complexes ; Cyclobutenylidene complexes ; Cycloadditions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pentacarbonyl(allenylidene)chromium and -tungsten, [(CO)5—M=C=C=CR2] (M=Cr, R=C6H4CH3-p(1a), C6H4OCH3 (1b); M=W, R=C6H4CH3-p (1c), react with the alkynyl complexes [Cp(CO)2Fe—C≡CR′] (R′ = nBu (2), Ph (4)), [Cp*(CO)2Fe—C≡CnBu] (6), [Cp(CO){P(OMe)3}-Fe—C≡CnBu] (8) and [Cp(PPh3)Ni—C≡CnBu] (10) by cycloaddition of the C≡C bond of the alkynyl complexes to the Cα=Cβ bond of the allenylidene ligand to give 3a-c), (5), (7), and respectively. The cycloaddition is highly selective. The spectroscopic data of these 1,3-heterobinuclear complexes indicate a delocalized π-system (M=Cr, W; Y=[Fe(CO)2Cp], [Fe(CO)(P{OMe}3)Cp], [Fe(CO)2Cp*], [Ni(PPh3)-Cp]). X-ray structural analyses of the compounds 3a, 9a, and 11c reveal a “butterfly” conformation of the four-membered ring. Its puckering angle is 142° (3a), 152° (9a), and 151° (11c). All Complexes exhibit a moderate to strong negative solvatochromic behavior. The extent of the solvatochromic effect depends on [(CO)5M] and Y and considerably decreases when C=CR2 is replaced by e.g. CMe2.
    Additional Material: 3 Ill.
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  • 69
    ISSN: 0009-2940
    Keywords: Phosphate - Phosphonate rearrangement ; Carbanions, benzylic, configurational stability of ; α-Hydroxyphosphonates, tertiary, chiral, non-racemic ; t-Butyl(phenyl)phosphinothioic acid, homochiral ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically active alcohols (ee ≥ 98%) such as 1-phenylpropanol, 1-(2-naphthyl)ethanol, 1-tetralol, and 1-indanol were transformed into diethyl phosphates 7a-d. sBuLi/TMEDA  -  induced phosphate - phosphonate rearrangement in diethyl ether furnished tertiary α-hydroxyphosphonates 8a-d of high enantiomeric purity (ee 94-98%) in yields of 43-83% with retention of configuration. The enantiomeric excesses were determined by using homochiral t-butyl(phenyl)phosphinothioic acid as chiral solvating agent.
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  • 70
    ISSN: 0009-2940
    Keywords: 1,1-Dithiolate ; Manganese complexes ; Rhenium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cationic tetracarbonyl complex cis-[Mn(CO)4-(S2CPCy3)]+ undergoes addition of hydride ion to the central carbon of the S2CPR3 ligand to afford, after spontaneous dimerization with loss of CO, the dimer [Mn2(CO)6{μ-S2C(H)PCy3}2] (5a), which was characterized by analytical and spectroscopic methods as well as by X-ray diffraction. In the molecule of 5a each S2C(H)PCy3- ligand is coordinated to one manganese in an η2-S,S′ chelate fashion, and one sulfur of each ligand serves as a bridge to bind the other manganese atom, thus forming a distorted Mn2S2 square. This appears to be a very stable arrangement. Compound 5a can be more easily prepared by treating the perchlorato complex [Mn(CO)3(S2CPCy3)(OClO3)] (2a) with NaBH4. This procedure is general and can be used for the preparation of several derivatives containing either manganese or rhenium [M2(CO)6{μ-S2C(H)PR3}2] 5a-d. The reaction of cationic tricarbonyl complexes [M(CO)3(S2CPR3)(PPh3)]PF6 (M = Mn, Re) with NaBH4 produced the same dimers 5a or 5c by displacement of the PPh3 ligand. Treatment of the dimer 5a with excess PEt3 or P(OMe)3 leads to the cleavage of the bridges and loss of one CO and the PR3 group from the S2C(H)PR3 unit to afford ultimately the dithioformate complexes [Mn(CO)2(S2CH)(L)2] [L = PEt3, P(OMe)3].
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  • 71
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1621-1625 
    ISSN: 0009-2940
    Keywords: Organo-zinc compounds ; Phosphaneiminato complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organo-Zinc Phosphaneiminato Complexes with Heterocubane StructureThe organo-zinc heterocubanes [ZnR(NPMe3)]4 with R = CH3 (1) and n-C4H9 (2) were prepared by the reaction of [ZnBr(NPMe3)]4 with MeLi and nBuLi, respectively, in hexane solution. In a similar reaction of nBuLi with [ZnI(NPMe3]4 the phosphaneiminato complex [Zn4I(nBu)4(NPMe3)3] (3) is formed. 1-3 were characterized by IR, NMR and MS spectroscopy, and by crystal-structure determinations. 1 and 2 possess heterocubane structures in which the zinc atoms are linked via μ3-N bridges of the phosphaneiminato groups, and all bond angles in the Zn4N4 core are close to 90°. A distorted heterocubane structure is observed for 3 with one of the NPMe3 moieties replaced by an iodine atom.
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  • 72
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 161-167 
    ISSN: 0009-2940
    Keywords: Sulfoxonium ylides ; 1,3-Dithietane 1,1,3,3-tetraoxide, silylated ; 1,3,5-Trithiane 1,1,3,3,5,5-hexaoxide, silylated ; Disulfenes, unsaturated ; Disulfenes, dianions of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sulfoxonium ylides 3a-h were synthesized by silylation of the cyclic methylene disulfones 1,3-dithietane 1,1,3,3-tetraoxide (1) and 1,3,5-trithiane 1,1,3,3,5,5-hexaoxide (4) with the silylating agents silyl nonafluorobutanesulfonates. The structure and constitution of the ylides were established with 1H-NMR, 13C-NMR, 29Si-NMR spectroscopy, mass spectrometry, and elemental analysis. On the route to the sulfoxonium ylides a new class of unsaturated disulfenes 7, 8, 12, 13 of 1 and 4 were synthesized via Knoevenagel and substitution reactions. Dianions of newly formed alkyl disulfenes 16a, b, e, f, and the trianion 17 were prepared and characterized by 1H-NMR and 13C-NMR spectroscopy and compared with the results of the ylides.
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  • 73
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 405-410 
    ISSN: 0009-2940
    Keywords: Osmium(0) complexes ; Nitrosyl complexes ; CS2, COS, SCNPh, and Ph2C=C=O as bidentate ligands ; Protonation and methylation reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of CS2 and Other Heteroallenes to the 16-Electron Osmium(0) Complexes trans-[OsCl(NO)(PiPr2R)2]The coordinatively unsaturated 16-electron compounds trans-[OsCl(NO)(PiPr2R)2] (1: R = iPr; 2: R = Ph) react with CS2 and COS to form the 1:1 adducts [OsCl(NO){κ2(C,S)-S=C=S}(PiPr2R)2)] (3, 4) and [OsCl(NO){κ2(C,S)-S=C=O}-(PiPr2R)2] (6, 7), respectively. While compounds 3, 4 are inert toward PMe3, the Os(COS) complexes 6, 7 react with tri-methylphosphane by abstraction of sulfur to give (OsCl(NO)-(CO)(PiPr2R)2] (8, 9). From 1 or 2 and phenylisothiocyanate the corresponding 1:1 adducts (OsCl(NO){κ2(C,S)-S=C=NPh}(PiPr2R)2] (10, 11) are obtained. Protonation and methylation reactions of 10 (R = iPr) with HBF4 or CF3SO3Me lead, by addition of the electrophile to the C=N nitrogen atom, to the formation of [OsCl(NO){κ2(C,S)-S=CNHPh}-(PiPr3)2]BF4 (12) and [OsCl(NO){κ2(C,S)-S=CN(Me)Ph}-(PiPr3)2]CF3SO3 (13). Treatment of 1 with diphenylketene yields [OsCl(NO){κ2(C,O)-O=C=CPh2}(PiPr3)2] (14). The X-ray structure analyses of 10 and 14 confirm the coordination of phenylisothiocyanate via S and C and of diphenylketene via O and C, respectively.
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  • 74
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 459-463 
    ISSN: 0009-2940
    Keywords: Cyclopentadienes ; Half-sandwich complexes ; Intramolecular nitrogen donors ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 8-Lithioquinoline reacts with 2,3,4,5-tetramethylcyclopentenone to give 8-quinolylcyclopentadiene (1/2) after acidic workup and treatment with ammonia. Two of the possible three isomers are formed; the acidic protons on the Cp rings show unusual downfield shifts in the 1H-NMR spectra. Treatment with strong bases led to the intensely coloured anionic 4 which was converted into the trimethylsilyl derivative 5. This is a suitable starting compound for the trihalotitanium and -zirconium compounds 6 and 7. The two complexes were investigated by crystal structure analyses. In both cases the quinolyl nitrogen atom is coordinated to the metal.
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  • 75
    ISSN: 0009-2940
    Keywords: Silaethenes ; [4 + 2] Cycloadditions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Silaethene tBu2Si=C(SiMe3)2, and the Structure and Reactivity of Its [4 + 2] Cycloadduct with Ph2C=OFrom tBu2SiF—CLi(SiMe3)2 by LiF elimination only Me2Si= C(SiMe3)(SiMetBu2) (1b) instead of tBu2Si=C(SiMe3)2 (1a) is isolated. With benzophenone, silaethene 1b (from its THF adduct 1b · THF) forms at -78 °C a yellow [4 + 2] cycloadduct (5) and a colorless [2 + 2] cycloadduct (6). With increasing temperature 5 transforms into 6, and 6 transforms -more slowly - into the yellow [4 + 2] cycloadduct (7) of 1a and Ph2CO. It follows from this that the migration equilibrium 1a ⇄ 1b really exists. The structure of 7 shows a planar —O—CPh=C6H5-framework with the cycloadded atoms Si and C from -tBu2Si—C(SiMe3)2- located above the plane. The =C6H5—C bond (1.62 Å) is exceptionally long. 7 is a source for 1a which is trapped by acetone (formation of an ene product) and by benzaldehyde [formation of a [2 + 2] cycloadduct, unstable against cycloreversion into PhHC=C(SiMe3)2 and tBu2SiO-containing substances]. Reaction of 7 with trimethylsilyl azide, less reactive than acetone or benzaldehyde, leads - by way of 1a which transforms into 1b - to a trapping product of 1b (formation of a [3 + 2] cycloadduct, unstable against transformation into (RMe2Si)(Me3Si)CN2 with R = (Me3Si)2N, or cycloreversion into (tBu2MeSi)(Me3Si)CN2 and Me2SiNSiMe3-containing substances). Reaction of 1b or 1b · THF with acetone leads only to an ene reaction product of 1b. This means, that only undetectable amounts of 1a or 1a · THF are in equilibrium with 1b or 1b · THF. A minor substance which is shown by NMR at low temperatures besides 1b or 1b · THF is interpreted as a rotamer of 1b or 1b · THF.
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  • 76
    ISSN: 0009-2940
    Keywords: Phosphaalkynes ; Phosphaalkenes ; Spirocyclotrimerization ; Triphospha Dewar benzenes ; Phosphaalkyne cyclooligomers ; Cage compounds, phosphorus-carbon ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of Lewis acidic derivatives of group 13 elements, phosphaalkynes 7 undergo spirocyclotrimerization with incorporation of the corresponding Lewis acids to form 10a-f. Scope and limitations of this novel cyclooligomerization process are examined. Starting from the spirocyclotrimer 10a reaction with the Lewis base dimethyl sulfoxide, we have in hand for the first time a method for the selective generation of two isomeric triphospha Dewar benzene derivatives (18, 19). Both can be trapped efficiently by further reaction with the phosphaalkyne to furnish the two novel phosphaalkyne cyclotetramers 20 and 21, both still possessing a phosphorus-carbon double bond. In the case of 21, further functionalization of the phosphaalkene unit is possible by [3 + 2] cycloaddition with a nitrile oxide (→ 23).
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  • 77
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1029-1034 
    ISSN: 0009-2940
    Keywords: Hydrogen bonding ; Hydroxy carboxylic acids, self-assembly of ; Crystal engineering ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The substituted 6-hydroxy-trans-3-hexenoic acids 2a and 2b are prepared by an organometallic template reaction involving a sequence of CC coupling reactions between a CO2 equivalent, butadiene, and 3-cyclopenten-1-one or 3,4-diphenyl-3-cyclopenten-1-one, respectively. In the crystal 2a assembles to form an infinite ribbon-type structure, exhibiting an alternating array of 12 and 18 atom-containing loops. The former are each constructed by an alternating CO2H/OH/CO2H/OH sequence, originating from four different monomeric units, that are linked together by means of hydrogen bonds. Two complementary ribbons of 2a are connected by van der Waals interactions to form staples that constitute the microscopic building blocks of the true (2a)n structure in the crystal. Stacks of cyclopentene π bonds are oriented inside the columnar structure of 2a. Acid 2b also forms a related ribbon-like assembly in the solid state. Here the bulky 3,4-diphenylcyclopentadienylidene moieties are oriented laterally at the ribbons, and van-der-Waals interactions with adjacent ribbons construct a three-dimensional hydroxyhexenoic acid network.
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  • 78
    ISSN: 0009-2940
    Keywords: Dithioxophosphoranes ; Diselenoxophosphoranes ; Internal coordination ; Steric protection ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some dithioxophosphoranes 3 stabilized by intramolecular coordination with a dialkylamino group were prepared, and their structures were analyzed by X-ray crystallography involving [2,4-di-tert-butyl-6-(isopropylmethylamino)phenyl]- (3c), {2,4-di-tert-butyl-6-[(dimethylamino)methyl]phenyl}- (3f), and {2,4-di-tert-butyl-6-[2-(dimethylamino)-1,1-dimethylethyl]phenyl}dithioxophosphorane (3h). The bond between the phosphorus atom and the aromatic ring is flexible and the angle narrows with decreasing ring size of the intramolecular coordination. The 31P-NMR signals are shifted to higher field with increasing ring size of the intramolecular coordination or strength of coordination. Similarly, the corresponding diselenoxophosphoranes 4 were prepared. Both their 31P- and 77Se-NMR signals are shifted to higher field with increasing contribution of intramolecular coordination.
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  • 79
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1093-1098 
    ISSN: 0009-2940
    Keywords: Indium tris(thiobenzoate) ; Triethylammonium tetrakis(thiobenzoato)indate ; Tin, butyl-, tris(thiobenzoate) ; Tin, dichloro-, bis(thiobenzoate) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Indium(III) and tin(IV) thiocarboxylates were prepared and characterized on the basis of their IR, 13C- and 19Sn-NMR data. Indium tris(thiobenzoate) (1) decomposes into a sulfido complex In (S)[S(O)CPh] (2a). The corresponding tris(thioacetate) In[S(O)CMe]3 is thermally too unstable to be isolated. The anionic tetrakis complex [Et3NH]{In[S(O)CPh]4} (3) was characterized by X-ray crystallography which revealed a distorted tetrahedral coordination at the In atom. X-ray diffraction analysis of the complexes BuSn[S(O)CPh]3 (4) and Cl2Sn[S(O)CPh]2 (7) showed distorted tetrahedral and cis-octahedral structures, respectively.
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  • 80
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1107-1113 
    ISSN: 0009-2940
    Keywords: Tripod ligands ; Hydrazines, substituted ; Diazenes ; Cobalt(III), fivefold coordination of ; Cobalt(II), fivefold coordination of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination behaviour of ligands having the same basic constitution RN=NC(=X)R′ (X = O, NR″, S) in their tripod cobalt derivatives has been analyzed. The ligands themselves may be considered as neutral heterodiene compounds and are in this respect vinylogues to diazenes RN=NRy′. Two- electron reduction of these neutral species results in dianionic heterosubstituted heteroolefins RN- -N=C(X-)R′. Due to their redox ambiguity the oxidation state of the metal M in chelate complexes is not a priori evident. Compounds tripod [5: X, R′ = O, Ph; 6; (X, R′) = (py); 7: X, R′ = S, NH2] are best described as containing low-spin Co(III) and dianionic ligands. Co(II) species are obtained with diethyl azodicarboxylate EtOOCN=NCOOEt as the ligand. In the mononuclear compound, with only one nitrogen and one carbonyl oxygen of the ligand acting as donor groups, the neutral ligand is coordinated to give the high-spin cobalt(II) species tripod (8). In the dinuclear compound 9 with both of the nitrogen atoms and carbonyl groups involved in coordination the dianionic ligand bridges two high-spin cobalt(II) centers to give tripod (9) as a derivative with two fused five-membered chelate rings. In addition to the conventional analytical techniques X-ray structure analyses, cyclovoltametric measurements, magnetic susceptibility and ESR data are used to characterize the compounds.
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  • 81
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1131-1142 
    ISSN: 0009-2940
    Keywords: Stannyl complexes ; Plumbyl complexes ; Tungsten complexes ; Molybdenum complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition-Metal Stannyl Complexes, 10 - Molybdocen and Wolframocen Derivatives with Two Different Main-Group-4 LigandsReactions of Li[Cp2MSnPh3] (M = Mo, W) with CH3I, BuBr, PhCH2Br, PhC(O)Cl or Br(CH2)nBr (n = 4,5) yield Cp2M(R)SnPh3 [R = CH3, Bu, CH2Ph, C(O)Ph, (CH2)nBr], while tBuBr or CH3C(O)Cl give the hydrido complexes Cp2M(H)SnPh3. A silyl stannyl complex is only obtained from Li[Cp2WSnPh3] and Me3SiOSO2CF3, but not with Me3SiCl or from the anionic Mo complex. In contrast, the reactions of chlorostannanes provide the bis(stannyl) complexes Cp2M(SnR′3)SnPh3 or Cp2M(SnR′2Cl)SnPh3. R/Cl exchange at the tin atom is observed when an excess of the chlorostannane is used. Upon reaction of Li[Cp2MSnPh3] with Ph3PbCl only Cp2M(PbPh3)SnPh3 is formed, while a mixture of Cp2M(PbMe3)SnPh3 and Cp2M(PbMe2Cl)SnPh3 is obtained with Me3PbCl due to redistribution reactions. The structures of Cp2W(SnPh3)C(O)Ph, Cp2W(SnPh3)SntBu2Cl and Cp2W(SnPh3)PbMe2Cl were determined by X-ray structure analyses.
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  • 82
    ISSN: 0009-2940
    Keywords: Thioaldehyde complexes ; Selenoaldehyde complexes ; Thietane complexes ; Selenetane complexes ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pentacarbonyl(thiobenzaldehyde)tungsten und pentacarbonyl(selenobenzaldehyde)tungsten (1a and 1b) undergo a thermal [2 + 2] cycloaddition with several vinyl ethers to give highly substituted transition metal-coordinated thietanes and selenetanes. The addition is highly regio- and stereospecific. The products undergo acid-catalyzed rearrangements, which lead to thermodynamically more stable diastereomers of the thietanes and selenetanes. The stereochemistry of both addition and rearrangement was established by reaction of deuterium-labeled vinyl ethers and by reaction of the cis and trans isomers of ethyl propenyl ether. The crystal structure of the bicyclic addition product of 1a and 3,4-dihydro-2H-pyran is reported.
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  • 83
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    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1251-1257 
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Cysteine ligands ; Histidine ligands ; Imidazole ligands ; Pyrazolylborate ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Highly substituted pyrazolylborate ligands TpR,Me were used to limit the coordination number of zinc towards cysteine- and histidine-derived coligands. Monodentate thiolate attachment (→ 1a-f) was achieved with N- and C-protected cysteine, monodentate carboxylate attachment (→ 3) with N-protected histidine. C-protected cysteine was found to form a five-membered N,S-chelate ring (2). While imidazole coordination with N- and C-protected histidine could not be achieved, cationic pyrazolylborate-zinc-coligand complexes [TpZn-L]+ (4a, b) were obtained for L = 2-methylimidazole. The new complexes were characterized by their spectra and three structure determinations.
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  • 84
    ISSN: 0009-2940
    Keywords: Organotungsten selenolates ; 77Se NMR ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organotungsten-selenolato complexes were prepared in moderate yields by insertion of selenium into the alkali metaltungsten bonds of MSeW(CO)3cp (M = Li, Na) and subsequent reactions with the organohalides o-, m-, and p- C6H4(CH2Br)2, C6H5CHBr2, m-C6H4(CHBr2)2 and C6H5CCl3. The 77Se-NMR data of the new complexes are discussed and compared with those of related complexes derived from organomonohalides. Moreover, the X-ray crystal structures of C6H5CH2W(CO)3cp (1), μ-[m-C6H4{CH2SeW(CO)3cp}2] (3), μ-[p-C6H4{CH2SeW(CO)3cp}2] (4), and C6H5CH[SeW-(CO)3cp]2 (5) were determined. In complex (1), the W-CH2 bond length is 2.374 Å; the W-Se bond lengths in the complexes 3, 4 and 5 are all in the range 2.625-2.655 Å, corresponding to W-Se single bonds.
    Additional Material: 3 Ill.
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  • 85
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 86
    ISSN: 0009-2940
    Keywords: Suzuki coupling ; π Complexes, organometallic ; π Complexes, dihaloarene ; Ruthenium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of a terphenyl derivative complexed by the cationic moiety Cp*Ru+ by Suzuki coupling of [Cp*Ru(BrC6H4Br)]OTf with phenyl boronic acid under catalysis of Pd(PPh3)4 in a DME-water mixture at 85°C in quantitative yield is reported. The stable coupling product 3 was characterized by X-ray crystal structure analysis.
    Additional Material: 1 Ill.
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  • 87
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1313-1322 
    ISSN: 0009-2940
    Keywords: Vinylidene complexes ; Allenylidene complexes ; Ene type reactions ; Atom economial reactions ; Reconstitutive additions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ruthenium complexes catalyze a variety of addition or isomerization reactions that are highly atom economical. Terminal alkynes react with allyl alcohols to form β,γ-unsaturated ketones that can be readily isomerized to α,β-unsaturated ketones via transient vinylidene complexes. A cyclization via a transient allenylidene complex concomitant with this addition represents a novel way to build heterocycles. Ancillary studies with these catalysts revealed an internal oxidation reduction whereby allyl alcohols are isomerized to saturated ketones and propargyl alcohols are isomerized to α,β-unsaturated carbonyl compounds. Consideration of the reaction mechanism led to a general Alder ene type reaction wherein alkynes serve as the enophile and alkenes serve as the ene component. These discoveries have led to a number of efficient total syntheses of biologically interesting targets. Mechanistic investigations into the activation of a ruthenium complex led to the discovery of a novel bis-homo-Diels-Alder reaction of 1,4-cyclooctadiene.
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  • 88
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1373-1377 
    ISSN: 0009-2940
    Keywords: Thionitrosyl azide ; Thiazyl azide ; Nitrosyl azide ; Tetranitrogen sulfide ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stimulated by the recent detection of nitrosyl azide (N3—N=O), we investigated the stability of the sulfur analogues thionitriosyl azide (N3—N=S) and thiazyl azide (N3—S≡N) by using ab initio MO calculations up to the QCISD(T)/6-311+G(d)//QCISD/6-311G(d) + ZPE level. Both azides have a similar energy content. While thionitrosyl azide is not stable with respect to N2 elimination, thiazyl azide resists to this process by an energy barrier of about 110 kJ/mol. The NS and N3 fragments resulting from homolytic cleavage lie about 100 kJ/mol above the azides. The five-membered ring is thermodynamically much more stable than both azides but kinetically unstable with respect to cheletropic decomposition yielding N2S + N2. Overall, trans-thiazyl azide is the most likely candidate for experimental observation of, for example, the reaction of NS+ salts with the azide anion. IR wavenumbers of the azides were also predicted.
    Additional Material: 1 Ill.
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  • 89
    ISSN: 0009-2940
    Keywords: Amido complexes ; Titanium(III) compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses, Properties, and Crystal Structures of the Titanium(III) Amido Complexes Ti[N(SiMe3)2]3, [TiCl2{N(SiMe3)2}(THF)2], and [Na(12-Crown-4)2][TiCl2{N(SiMe3)2}2]TiCl3(THF)3 reacts with NaN(SiMe3)2 to furnish [TiCl2{N(SiMe3)2}(THF)2] (1), whereas in the presence of 12-crown-4 the ionic amido complex [Na(12-crown-4)2][TiCl2{N(SiMe3)2}2] (5) is obtained besides [Na(12-crown-4)2][TiCl4(THF)] (4). On the other hand, the titanium(III) amido complex Ti[N(SiMe3)2]3 (2), the crystal structure of which was solved, reacts with NaN(SiMe3)2 in the presence of 12-crown-4 with deprotonation of one of the methyl groups to give the carbometalated complex [Na(12-crown-4)2][Ti{N(SiMe3)2}2{N(SiMe 3CH2)}] (3).
    Additional Material: 4 Ill.
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  • 90
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 259-262 
    ISSN: 0009-2940
    Keywords: Halide complexes of diiodacetylene ; Crystal structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexes of Halide Ions with Diiodoacetylene. The Crystal Structures of PPh4[X(I-C≡C-I)2] with X = Cl, Br, IThe complexes PPh4[X(I-C≡C-I)2] with X = Cl (1), Br (2), and I (3) have been prepared from the phosphonium salts PPh4X and 1-C≡C-I in dichloromethane solutions. 1-3 form colourless crystals, which according to crystal structure analysis crystallize isotypically in the space group P421m with two formula units per unit cell. The diiodacetylenes are coordinated by the halide ions X- in a distorted tetragonal fashion, the I-C≡C-I molecules being in μ2-bridging function. Thus, a polymeric anionic network [X(I-C≡C-I)2]nn- with a layered structure results.
    Additional Material: 2 Ill.
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  • 91
    ISSN: 0009-2940
    Keywords: 2-(2-Pyridyl)phosphinines ; 2,2′-Biphosphinines ; Transition metals ; Biphosphinine chelates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and coordination chemistry of 2-(2-pyridyl)-phosphinines and 2,2′-biphosphinines are reviewed. A noteworthy series of homoleptic complexes of 4,4′,5,5′-tetramethyl-2,2′-biphosphinine (tmbp) with Cr(0), Mo(0), Wo(0) and Ni(0) are described. A [Cu(bpy)(tmbp)]+ cationic polymer has been characterized by X-ray analysis. Ruthenium, manganese and rhenium chelates were also obtained. With Mn2(CO)10, a (tmbp)-Mn2(CO)6 complex is formed where tmbp acts as an eight electron donor.
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  • 92
    ISSN: 0009-2940
    Keywords: Transition-metal indium complexes ; Nickel-indium bonds ; Intramolecular Lewis base adducts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of InBr/InBr3 or InBr/BrIn[(CH2)3NMe2]2 with the transition metal dimers [L(CO)nM]2 {L = CO, Cp, C5H4[(CH2)2NMe2]; M = Fe, Co, Ni; n = 1-3} in THF or dioxane gives in almost quantitative yield the transition metal indium complexes L(CO)nM—InBr2(Do) (Do = THF, NC7H13) and L(CO)nM—In[(CH2)3NMe2](Br) respectively. The new compounds were characterized by elemental analysis, infrared v(CO) spectroscopy, NMR, and mass spectrometry. An X-ray single crystal structure determination of (η5-C5H5)(CO)-Ni-InBr2(NC7H13) (1a) revealed a short Ni-In bond of 246.3(1) pm.
    Additional Material: 3 Ill.
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  • 93
    ISSN: 0009-2940
    Keywords: {[ω-(Phosphanyl)alkyl]cyclopentadienyl}cobalt(I) ; Cobalt complexes ; Bidentate ligand ; Alkynes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An improved synthesis of [(2-phosphanylethyl)cyclopenta-dienyl]cobalt(I) chelate complexes is presented, in which the paramagnetic chloride 3 is a precursor of the ethene complex 4. The latter readily undergoes ligand exchange reactions which in the case of bidendate reagents (1,5-cyclooctadiene, 1,2-bis(diisopropylphosphanyl)ethane, 2,2′-bipyridine, nor-bornadiene) cause a decomplexation of the phosphane arm at room temperature with formation of 7, 5, 6, 8. The ethene ligand in 4 can be replaced by alkynes under equally mild reaction conditions (formation of 9, 11 - 16). The reaction with ethyne results in the formation of vinylidene complex 10. The yields of the reactions with nonaromatic alkynes could be improved by treating 3 with the alkyne in the presence of sodium amalgam. The unsubstituted vinylidene complex 10 and its tert-butyl derivative 17 were obtained by this route in 38 and 40% yield, respectively.
    Additional Material: 1 Ill.
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  • 94
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 355-359 
    ISSN: 0009-2940
    Keywords: Aluminium compounds ; Gallium compounds ; Indium compounds ; Trimethylfluoro metalates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cesium-Fluorine Four-Membered Rings as Structural Motive in Cesium Triorganofluoro Metalates of Group 13The reactions of AlMe3, GaMe3, and InMe3 with CsF in acetonitrile furnish the corresponding trimethylfluoro metalates Cs[Me3MF] (1: M = Al, 2: M = Ga, 3: M = In). The salt-like compounds 1 - 3 were characterized by NMR, IR, and MS techniques as well as by X-ray structure analysis. Cs2F2 four-membered rings are the structure-dominating units in all three compounds. Compound 1 consists of puckered layers of weakly associated Cs2F2 rings parallel to (100), while the four-membered rings in 2 form infinite ladder-type chains. The Cs-F rings in 3 build up a heterocubane with a Cs4F4 core by ring stacking.
    Additional Material: 5 Ill.
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  • 95
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 381-384 
    ISSN: 0009-2940
    Keywords: Alanes, tert-butoxy- and bis(tert-butoxy)- ; Gallanes, tert-butoxy- and bis(tert-butoxy)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structures obtained by X-ray methods of (tert- butoxy)alane and -gallane (tBuOMH2) are isotypic and are composed of discrete centrosymmetric dimers. The dimers arise from almost symmetrical Al—O—Al [1.810(3), 1.815(3) Å] and Ga—O—Ga [1.902(9), 1.908(9) Å] bridges forming a central rhombohedral four membered M2O2 cycle [O—Al—O 81.0(2)°, O—Ga—O 78.6(5)°] with the metallic atoms in a distorted tetrahedral environment. When one of the hydride ligands on the metals is further substituted by tert-butoxy, the formation of (tBuO)2AlH and (tBuO)2 GaH is observed. These two compounds crystallize in different lattices and space groups, but they are nevertheless very similar in their structure: the centrosymmetric M2O2 cycle is maintained [Al—O 1.817(3), 1.817(3) Å; Ga—O 1.904(4), 1.907(4) Å] As expected, the terminal Al-O [1.675(3) Å] and Ga—O [1.783(4) Å] distances are considerably shorter than the bridging ones.
    Additional Material: 3 Ill.
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  • 96
    ISSN: 0009-2940
    Keywords: Germanium ; Trigermanes ; Germylene ; Trapping reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of hexa-tert-butylcyclotrigermane (3) with CCl4, Br2, and I2 furnishes the correspondingly substituted 1,3-dichloro- (4), 1,3-dibromo- (5), and 1,3-diiodotrigermanes (6). The symmetries of the molecules of 5 and 6 are very similar (point group C1) revealing gauche-anti conformations and different Ge—Ge bond lengths. However, while 5 crystallizes as a racemate, 6 forms a conglomerate of enantiomerically pure crystals. The X-ray structure analysis of the 1,3-dimethyltrigermane (7) derivative, derived from 6 by a sequence of metalation and methylation reactions, reveals more symmetrical molecules of the point group C2 which also crystallize as a racemate. Irradiation of 3 leads to tetra-tert-butyldigermene (8) and di-tert-butylgermylene (9) which could be trapped by addition and cycloaddition reactions with selenium, tellurium, and 3,5-di-tert-butyl-1,2-benzoquinone.
    Additional Material: 2 Ill.
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  • 97
    ISSN: 0009-2940
    Keywords: Carbene complexes ; Metallacycles ; Claisen rearrangement ; Cascade reaction ; Cyclopentenones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cationic ferracyclic carbene complexes 1 react with carbon nucleophiles like lithium enolates and organocuprates to give the corresponding 4-substituted 1, (3E)-diene tricarbonyl-iron complexes 6 and 9. The reaction is thought to proceed by initial attack on the allyl terminus and subsequent ferra Claisen-Ireland rearrangement of the intermediate (η2 alkene)carbene complex 4. This rationale is supported by the isolation and characterisation of analogous aminooxocarbene derivatives 8. With sterically demanding enolates products 6 are formed in diastereomeric ratios of up to 90:10, thus demonstrating the inductive power of the chiral metallacycle in 1. Lithium acetylides as carbon nucleophiles react with 1 according to a novel cascade to give regio- and stereospecifically 2,5,5-trisubstituted-cyclopentenones 10 suggesting a concerted formation of four C=C bonds together with a CO insertion and a formal carbene transfer step.
    Additional Material: 1 Tab.
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  • 98
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 435-440 
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Sulfur and nitrogen ligands ; Structure and bonding ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The zinc complex chemistry of the tridentate thiol ligand N- (2-mercaptophenyl)(2-picolyl)amine (MPPAH) differs considerably from that of the aliphatic analogue N-(2-mercaptoethyl)(2-picolyl)amine reported previously. This is due to the lower basicity and hence bridging tendency of its aromatic thiolate function. With zinc salts of oxo anions the 1:1 complexes (MPPA)ZnX (1a-c: X = ONO2, OAc, OBz) are formed which according to spectroscopic data are monomeric while the halide (MPPA)ZnBr (2) seems to be polymeric. In the absence of coordinating anions the monomeric 2:1 complex (MPPA)2Zn (3) results which according to a crystal structure determination contains tetrahedral zinc coordinated by one MPPA ligand in a tridentate fashion while the other is only monodentate and sulfur-bound. A similar N2S2 coordination can be deduced for the 1:1:1 complex (MPPA)Zn(STrt) (4) resulting from ZnEt2, MPPAH and triphenylmethanethiol.
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  • 99
    ISSN: 0009-2940
    Keywords: Phosphenium cations ; Silver complexes ; 31P, 109Ag NMR shift correlation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of bis(diisopropylamino)phosphenium triflate (1[CF3SO3]) with silver salts AgY [Y- = CF3CO2- (2a), CF3-SO3- (2b), CH3CO2- (2c)] affords neutral complexes [{(iPr2N)2(Y)P} Ag(OSO2CF3)] (3a-c). While 3a, c are stable up to ambient temperature, 3b is only stable at low temperature and in equilibrium with the cation 1. The constitution of 3a-c was derived from multinuclear (1H, 13C, 31P, 109Ag) NMR spectra. Compound 3a was further studied by X-ray single-crystal diff ractommetry which showed the presence of dimeric units with μ2-bridging triflate ligands and three-coordinate silver atoms with a planar T-shaped coordination geometry. Reaction of 4-chloro-1,3-bis(2,6-dimethylphenyl)-1,3,2-diazaphospholenium triflate (4[CF3SO3]) with 2a, c affords equilibrium mixtures whose 31P- and 109Ag-NMR spectra suggested the presence of silver complexes 5a, c with constitutions similar to those of 3a, c besides unreacted cation 4. No reaction was observed between 4[CF3SO3] and 2b. A common mechanism accounting for the different outcome of the individual reactions will be discussed.
    Additional Material: 1 Ill.
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  • 100
    ISSN: 0009-2940
    Keywords: Nitroxide radical ; Silver(I) complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 2,5-dihydro-4,5,5-trimethyl-2,2-di-2-pyridyl-imidazole-1-oxyl (L) with AgSbF6 gives the complex [Ag2L2]2+[SbF6-]2 which was characterized by X-ray diffraction. - The complex (a biradical) forms a four-membered ring with two Ag(I) ions and two imine nitrogen atoms of the imidazolines with a relatively short Ag - Ag distance [2.839(2) Å]. Magnetic measurements indicate that two nitroxide radicals are slightly coupled.
    Additional Material: 3 Ill.
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