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  • 2000-2004
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  • 101
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 198-198 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 102
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 208-217 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die “bovine spongiforme encephalopathy” (BSE) wurde 1986 in britischem Rindvieh diagnostiziert ‘36’. vorliegende Ergebnisse zeigen, daß die Krankheit durch Zustaz von kontaminiertem Tier-und/oder Knochenmehl entstand, das einen Scrapieähnlichen Erreger (siehe unten) enthielt, der von Schafen oder Rindern stammte ‘37’. Der orale Weg der Infektion konnte durch Verfütterung von hirnhomogenaten BSE erkrankter Rinder an Ziegen experimentell belegt werden ‘2’.Es wurde schon Anfang des jahrhunderts empfohlen, Proteinzustz Futtermitteln beizumischen. Die Verfütterung an Wieder käuer wurde in verschidenen Ländern praktiziert ‘8’. Sie stellt keine Besonderheit der britischen Agrarindustrie dar.In diesem Artikel soll ausgeführt werden, was Tiermehl ist, wie es produzxiert und wie es in der amtlichen Futtermittelkontrolle nachgewiesen wird. Es wirde die Kontamination von Futtermitteln für Wiederkäuer mit Spuren von Bestandteilen tierischer Herkunft im Produktionsprozeß dargestellt und das Problem des Nachweises solcher Sputren in Futter diskutiert. Abschließend wird auf die Zukunft des Produktes “Tiermehyl” im Zusammenhang mit Alternativen zur bestehenden Entsorgung toter tierischer Körper und von Schlacht abfällen eingegangen.
    Additional Material: 7 Ill.
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  • 103
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 223-237 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Zu den faszinierendsten “Waffen” im Tierreich gehören die Gifte. Auch viele Insekten setzen Gifte ein, zum Beispiel als Wehrgifte, wie sie von den staatenbildenden sozialen Hymenopteren, den Bienen, Hornissen und Faltenwespen bekannt sind. Die Wirkung dieser Gifte ist aufgrund ihrer medizinischen Bedeutung bereits intensiv untersucht. Über die Art und Weise der Giftinjektion sowie die Wirkungsweise der Gifte solitär lebender Wespenarten, etwa von Weg- und Grabwespen, ist vergleichs weise wenig bekannt. Eine Besonderheit der solitären Wespenarten ist, daß ausschließlich ihre Weibchen Insekten oder Spinnen jagen, um ihre künftige Brut zu versorgen. Spezielle jagdstrategien verringern dabei die Gefahr, daß potentielle Beutetiere die jagenden Wespenweibchen früch zeitig entdecken. Ist ein Beutetier optisch und/oder chemisch identifiziert. wird es je nach Wespenart durch einen oder mehrere Stiche paralysiert (gelähmt). Anfängliches Abwehrverhalten, selbst größerer Beutetiere, wird auf diese Weise unterbunden, und die Opfer können an einen sicheren Ort, ein Nest oder eine umfangreiche Nestanlage mit günstigem Mikroklima, gebracht werden, wo anschließend ein Ei abgelegt wird. Die sich auf ihrem Wirt entwickelnde Larve ist so vor dem Zugriff durch Feinde geschützt.Die an der Beute als Folge eines Stiches zu beobachtenden Giftwirkungen reichen von der vollständigen Paralyse, also dem totalen, in einigen Fällen auch irreversiblen Verlust der Fähigkeit, such zu bewegen, über vielfähigkeit, sich zu bewegen, über vielfältige, durch sas Gift bewirkte auffällige Verhaltensänderungen. Im Hinblick auf das Nervensystem lassen sich peri pher und zentral wirkende Gifte unter sscheiden, wobei der Wirkort durch das Stechverhalten der Wespe vorgegeben sein kann.
    Additional Material: 8 Ill.
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  • 104
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 308-309 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Der Nachhaltigkeitsgedanke bei der Nutzung der Natur ist, zumindest als Begriff, jedermann bewußt. Daß es selbstverständlich auch nicht-nachhaltige Umweltnutzungen gibt, wird uns klar, wenn wir an die überdüngten, blaualgen verseuchten Gewässer insbesondere in den neuen Bundesländern denken, uns die Hochwässer in den süddeutschen Flüssen dieses Frühjahrs vor Augen führen, durch die Braunkohletagebau-Regionen Mitteleuropas fahren oder uns die Wasser- oder Winderosionsprobleme in deutschen Landschaften vergegenwärtigen. Dies sind nur einige, willkürlich zusammengestellte Beispiele. Das Institut für Gewässerökologie (IGB) versucht, den Gedanken der nachhaltigen Bewirtschaftung von Binnengewässern zu präzisieren und in aktuelle Forschungsarbeiten umzusetzen.
    Type of Medium: Electronic Resource
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  • 105
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999) 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 106
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 12-17 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die heutigen Wälder, die man in Europa vorfindet, waren nicht immer dort. VOr 22000 Jahren - im Hochglazial - gab es nur im Mittelmeergebiet die klimatischen Voraussetzungen für das Wachstum von Bäumen. Allerdings waren dies meist keine dichten Wälder, sondern Steppen mit einzelnen Baumgruppen. Das bedeutet jedoch, daß die heute in Europa wachasenden Bäume während der letzten 12000 Jahre - also seit dem Ende der letzten Eiszeit - nach Mittel- und Nordeuropa eingewandert sein müssen. Am Beispiel der Waldbäume Eiche (Quercus), Hainbuche (Carpinus), Fichtet (Picea) und Tanne (Abies) soll diese Einwanderung aufgezeigt werden.
    Additional Material: 8 Ill.
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  • 107
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 55-55 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 108
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 44-53 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Quecksilber und seine Verbindungen haben trotz ihrer Giftigkeit vielfältige medizinische und industrielle Anwendungen. Die Nutzung des Quecksilbers durch den Menschen hat jedoch erhebliche Umweltbelastungen, insbesondere quecksilberbelastete Abwässer und Böden, zur Folge, die auch mit physikalisch-chemischen Sanierungsverfahren nicht befriedigend beseitigt werden können, da die Verfahren häufig teuer oder nicht spezifisch genug sind. Mikroorganismen haben im Laufe ihrer Evolution einen Mechanismus entwickelt, um Quecksilberverbindungen zu entgiften. Er beruht auf den Aktivitäten von zwei durch das mikrobielle mer-Operon codierten Enzymen, Quecksilberreduktase und Quecksilberlyase, die in der Lage sind, Organoquecksilberverbindungen und ionuisches Quecksilber in metallisches Quecksilber zu überführen. Die mikrobielle Quecksilberreisistenz kann eingesetzt werden, um quecksilberhaltige Abwasserströme mittels eines einfachen, umweltfreundlichen Verfahrens zu reinigen.Innenansicht einer Chlor-Alkali-Elektrolyseanlage zur Gewinnung von Chlor und Natronlauge nach dem Amalgamverfahren. Bei diesem Prozeß wird auch heute noch in großem Umfang Quecksilber eingesetzt. In den Elektrolysezellen dieser Halle befinden sich insgesamt etwa 50 Tonnen Quecksilber.
    Additional Material: 7 Ill.
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  • 109
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 58-58 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 110
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 59-60 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 111
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 61-61 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 112
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 153-153 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 113
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 90-97 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die fossile Überlieferung aus den letzten präkambrischen Jahrmillionen deutet darauf hin, daß gelatinös organisierte Formenj, also quallenähnlich gebaute Organismen, die das marine Pelagial (den freien Wasserkörper des Meeres) besiedelten ‘3’. Was sie dort vorfanden war jedoch wenig labensfreundlich. Zwar wimmelte das Meer von bakterien und Protozoen, aber im wesentlichen waren die riesigen Wasserräume leer und unbesiedelt. Crustaceen und andere Organisationsformen waren - wenn die Befunde stimmen - noch in der Entwicklungsphase beziehungsweise noch nicht zu der pelagischen Lebensweise übergegangen. Wie überlebten die quallenförmigen Organismen in dieser Umwelt, und warum leben sie noch heute in allen Bereichen des Meeres, von der Flach- bis in die Tiefsee, von den Polen bis zu den Tropen? Der pelagische Lebensraum beinhaltet Tausende von Arten, die viel “höher” organisierten Gruppen angehören, die schneller und kräftiger sind. Wieso wurden die gelatinösen Plankter nicht in irgendeine skurrile Nische gedrängt oder über die Konkurrenz völlig ausgeschaltet? Mögliche Antworten auf diese Fragen finden wir in der Gegenwart.
    Additional Material: 9 Ill.
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  • 114
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 79-89 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Nach dem Grundsatz “Vermeiden geht vor Wiederverwertung oder Recycling und letzteres vor Ablagerung auf einer Deponie”, schreibt das Kreislaufwirtschafts- und Abfallgesetz 3 zwingend die Wiederverwertung von Wertstoffen vor. Schlacke aus Müllheizkraftwerken (MHKWs) wird vom Gesetzgeber als ein Wertstoff klassifiziert und unterliegt damit dem Wiederverwertungszwang. Verwendung findet die MHKW-Schlacke im Straßenbau als Ersatz für Sand und als Versatzmaterial in au fgelassenen Bergwerken. Während der letztere Verwendungszweck relativ unumstritten, wenn auch sehr teuer ist, stößt der erstere auf herbe Kritik seitens ökologisch orientierter Gruppen, insbesondere wegen des hohen Schwermetallgehalts der MHKW-Schlacke. Dieses geschieht unbeschadet der Tatsache, daß der Einsatz von Schlacke als Baumaterial starken Einschränkungen unterliegt, die insbesondere einen Kontakt der Schlacke mit Grundwasser und Niederschlägen und damit eine Elution ausschließen ‘6’. In Zukunft dürfte die Schlackeproblematik noch mehr als bisher Gegenstand umweltpolitischer Disku ssion sein, da ab dem Jahre 2005 alle herkömmlichen Hausmülldeponien für unverbrannten Restmüll de facto geschlossen werden. Dieses wird zwangsweise zu einer vermehrten Verbrennung von Restmüll und somit zu einer verstärkten Schlackeproduktion führen. Damit erhebt sich erneut die Frage nach der Wiederverwendung von Schlacke und damit nach ihrer Umweltverträglichkeit. Als sowohl ökonomisch als auch ökologisch vertretbare Alternativen stehen bislang nur neue kostengünstige Formen der Deponierung im Raum. Der folgende Artikel befaßt sich mit dem Pro und Contra der Wiederverwendung von MHKW-Schlacke aus Sicht der Pflanzenphysiologie und gibt eine Übersicht über die Streßfaktoren, denen Pflanzen bei der Kultur auf Schlacke ausgesetzt sind.
    Additional Material: 12 Ill.
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  • 115
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    Biologie in unserer Zeit 29 (1999), S. 121-124 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 116
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    Biologie in unserer Zeit 29 (1999), S. 125-125 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 117
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 126-126 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 118
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. VIII 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 119
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. XI 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 120
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999) 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 121
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 132-141 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Für einen landwirtschaftlichen Anbau in Deutschland ist die Entwicklung von traansgenen Sorten beim Winterraps zur Zeit am weitesten gediehen, weshalb das Thema Gentechnik für diese Pflanzenart besondere Aktualität besitzt. Überdies erfolgt die züchterische Sortenentwicklung bei jeder Kulturpflanze prinzipiell in denselben Schritten. Es erscheint hilfreich, sich diese an einem erfolgreichen Beisiel zu vergegenwärtigen, will man die neuen Methoden der Biotechnologie mit den bisher in der Pflanzenzüchtung gebräuchlichen vergleichen und sachgerecht bewerten.
    Additional Material: 7 Ill.
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  • 122
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    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 158-166 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Gentechnikspezifische rechtliche Vorgaben sind beim Herstellen von gentechnisch veränderten Pflanzen (GVP), Arbeiten mit GVP und dem Vermarkten von GVP einzuhalten. Diese reichen von der Anmeldung oder Genehmigung der gentechnischen Arbeit in einer gentechnischen Anlage, der Dokumentation der Arbeiten, bis zu den erforderlichen Genehmigungen von Freisetzungen oder des Inverkehrbringens der GVP.Die Einhaltung der gesetzlichen Vorgaben erfordert ebenso wie die praktische Überwachung geeignete Nachweisverfahren. Nach einer kurzen Darstellung der gesetzlichen Etikettierungsvorschriften für gentechnisch veränderte Organismen sollen diese Verfahren hier vorgestellt werden.
    Additional Material: 5 Ill.
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  • 123
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    Biologie in unserer Zeit 29 (1999), S. 184-187 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 1 Ill.
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  • 124
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    Biologie in unserer Zeit 29 (1999), S. 189-191 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 125
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    Biologie in unserer Zeit 29 (1999), S. 192-192 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 126
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    Biologie in unserer Zeit 29 (1999), S. 177-183 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Vielfalt in allen Erscheinungsformen kennzeichnet schon die unbelebte und in noch stärkerem Maße die belebte Natur. Dagegen drängt die Nutzung von Naturkräften durch den Menschen, insbesondere in ihren weiter entwickelten und technisierten Formen stets auf Vereinfachung. So werden landwirtschaftliche Kulturpflanzen bei ein- bis mehrjähriger Nutzung im Regelfall in Reinkultur angebaut, ganz im Gegensatz zur standorttypischen Artenvielfalt eines natürlichen Pflanzenbestandes. Lediglich die verbliebene Unkrautflora erinnert dann and die ursprüngliche Artenvielfalt einer Pflanzengesellschaft. Es kommt hinzu, daß sich landwirtschaftlicher Pflanzenbau auf nur wenige anbauwürdige Kulturpflanzenarten konzentriert. Weltweit nimmt das Ackerland etwa 10 % der Landoberfläche der Erde ein, die mit nur etwa 30 Kulturpflanzenarten von überregionaler Bedeutung bestellt werden. Allein 37,4% davon sind dem Anbau von nur dreif für die Ernährung der Menschheit besonders bedeutsamen Arten (Weizen, Resi und Mais) gewidmet. In Deutschland werden gegenwärtig sogar 33% der Landoberfläche als Ackerland genutzt. Von den insgesamt etwa 14 bei uns häufiger anzutreffenden Kulturpflanzenarten besetzen die drei dominierenden Arten (Winterweizen, Mais und Wintergerste) dabei 48% der Anbaufläche. Landwirtschaftlicher Pflanzenbau wird also generell artenarm betrieben.Die zweite Ebene bilogischer Vielfalt im landwirtschaftlichen Pflanzenbau stützt sich auf die mehr oder weniger regelmäßige Folge verschiedener in Reinkultur angebauter Kulturpflanzenarten. Bozogen auf die Gesamtfläche eines Betriebes order die Feldflur einer Gemeinde ergibt sich dann noch immer ein abwechslungsreiches Gesamtbild verschiedener Aussaat-, Blühund Erntezeiten. Für artenreiche Fruchtfolgen lassen sich darüber hinaus viele, für die Bodenbewirtschaftung vorteilhafte Argumente anführen. Die hohe Schlagkraft der vollmechanisierten Betriebe und die beliebige Verfügbarkeit von Dünge- und Pflanzenschutzmitteln in Verbindung mit artunterschiedlichen Ertrags- und Preisrelationen haben jedoch auf intensive bewirtschafteten Betrieben in günstigen Lagen zu einer oft drastischen Reduktion der Pflanzenproduktion (auf den Anbau von nur noch drei, manchmal sogar nur zwei Arten) geführt, von denen der jeweils höchste Beitrag zur Deckung der Betriebskosten erwartet werden kann.Inzwischen hat sich jedoch die Erkenntnis durchgesetzt, daß die Aufrechterhaltung “biologischer Diversität” ein wesentliches Element zur Sicherung der “Nachhaltigkeit” der landwirtschaftlichen Pflanzenproduktion darstellt. Dies hat in der Konferenz von Rio (1992) im Rahmen der Agenda 21 zum Abschluß einer “Konvention über Biologische Vielfatl” geführt, der auch die Bundesrepublik Deutschland beigetreten ist.Mit dem Begriff biologische Vielfalt werden in dieser Konvention nicht nur Naturschutzverpflichtungen zur Sicherung des Erhalts bedrohter Tier- und Pflanzenarten übernommen, sondern es geht zu einem wesentlichen Teil auch um die 3. Ebene der biologischen Vielfalt in Form der genetischen Vielfalt innerhalb der für die Welternährung grundlegend bedeutsamen Kulturpflanzenarten. In diesem Zusammenhang soll hier gefragt werden, ob mit der Einführung transgener Nutzpflanzen neben ihrem wirtschaftlichem Nutzen auch Risiken für die biologische Vielfatl verbuden sind.
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  • 127
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    Biologie in unserer Zeit 29 (1999), S. 200-207 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Es ist schon erstaunlich: Man setzt sich eine einfache Brille auf, die als “Gläser” zwei farblose Folien enthält, und schon spielt die räumliche Sehwelt verrückt. Farbige Felder in bunt gemusterten Flächen springen in der Wahrenhmung auf uns zu, und andere weichen zurück. Betrachtet man eine Person vor dunklem Hintergrund, die einen roten Pullover and eine blause Hose anhat, so sieht man die obere Hälfte viel näher als die untere. Und noch verrückter: Ähnlich wei bei Michael Endes “Scheinriese” Tur-Tur ‘1’ nimmt der Tiefeneindruck zu, je weiter man sich von dem betrachteten Objekt entfernt. Wie kommt dieser Effekt zustande?Das Grundprinzip der ChromaDepth-Brille (C3DTM glasses), die von der Firma Chromatek in Georgia/USA hergestellt wird, ist die Farbdispersion: Rotes Licht wird durch das Gitter der brillenfolie stärker seitlich abgelenkt (gebeugt) als blaues Licht (Abbildung 1). Das dies für beide Augen gegensinnig erfolgt, ergeben sich Bildunterschiede zwischen rechtem und linkem Auge; Disparitäten, die das Sehsytem im Gehirn wie gewohnt als Raumtiefe deutet(Farbtiefeneffekt, Abbildung 2) Deshalb seiht man mit der ChromaDepth-Brille bunt gemusterte Flächen räumlich, genauer formuliert: Setzt man die Brille auf, so springen die Bilder, die wir mit unseren beiden Augen sehen, etwas aufeinander zurote Bildteile mehr, blaue weniger, Die Folge ist: Vor dunklem hintergrund erscheinen rote Flachen näher als blaue. Vor hellem Hintergrund ist es genau umge Kehrt: Rot erscheint hinter Blau. Das Ausmaß der wahrogenommenen Tiefe ist beträchtlich. So scheint der rote Fleck eines Laser-Pointers, auf eine vier Meter entfernte weiße Wand fällt, 110 Zentimeter vor dieser Wand in der Luft zu schweben. Im einzelnen kan der Sachverhalt sehr kompliziert sein. Auch wenn wir meinen, eine bestimmte Farbe zu sehen, handelt es sich in Wirklichkeit meist um ein kompliziertes Gemisch verschiedener Wellenlängen, die alle mit der ChromaDepth-Brille auseinan-dersortiert werden und ganz unerwartete Tiefenstaffelungen erzeugen können.
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    Biologie in unserer Zeit 29 (1999), S. 218-222 
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    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Scheinbar hat es Vortelie, Zwitter zu sein. Die Erstbesiedlung neuer oder gestörter lebensräume wird durch die Möglichkeit zur Selbstbefruchtung vereinfaht oder bei Abwesenheit von Sexualpartnern sogar erst möglich. Aus einem einzigen Samen einer selbstbestäubenden Pflanze kann sich bei gleichzetig hoher Reproduktionsrate, schnell eine große Population aufbauen. Viele kleine Brassicaceen (Kreuzblülter), wie etwa die Ackerschmalwand Arabidopsis thaliana, sind dafür gute Beispiele. Doch uneingeschränkte Selbstbefruchtung hat offensichtliche Nachtelie. Ungünstige Mutationen häufen sich im Genom an, und die durch Durchmischung des Erbgutes bewirkten heterosiseffekte entfalten sich nicht. Daher finden sich in etwa der Hälfte aller pflanzenfamilien Arten, bei denen Selbstbefruchtung (Autogamie) ausgeschlossen ist ‘5’. Verbreitete Mechanismen, die eine Allogamie (Frembdefruchtung) begünstigen, sind unterschiedliche Reifezeitpunkte und -orte der weiblichen und mänlichen gameten auf einer Pflanze oder die Diözie (Zweihäusigkeit), bei der weibliche und männliche Gameten auf unterschiedlichen Individuen gebildet werden. Weiterhin gibt es eine Vielzahl morphologischer Barrieren, die das zufällige Bestäuben mit dem eigenen Pollen behindern und Pflanzen häufig an Tiere als Pollenüberträger von Blüte zu Blüte binden. “Echte” selbstinkompatible pflanzen können den eigenen Pollen oder den der “näheren Verwandtschaft” erkennen und abn der Befruchtung hindern, sie sind aber nicht etwa steril, wie der früher gebrächliche Begriff Selbststerilität nahelegte, da sie fertile Gameten bilden. Erkannt wurde das Phänomen schon 1764 von Köreuter für die Königskerze Verbascum phoenichicum, doch die erste eingehende Analyse und Zusammen fassung dieser Daten und eigener Befunde erfolgte später (1867) durch Charles Darwin. Er erkannte als erster, daß die beobachtete Unfruchtbarkeit durchaus als “Begabung” angesehen werden kann.Viele landwirtschaftlich genutzte Arten sind heute selbstkompatibel, weil im Laufe ihrer Kulturgeschichte die Selbstinkompatibilitäts- Mechanismen verlorengegangen sind oder bewuß darauf verzichtet wurde. Dies hat gute Gründe: Einer davon ist vor allem eine Ertragssteigerung durch die ungehinderte (Selbst-) Befruchtung. Allerdings ist mit solchen Pflanzen die Produktion von Hybridsaatgut zur, “Handarbeit” des Züchters geworden. Im Zeitalter teurer menschilcher Arbeitskraft hat daher jede Art von Pollensterilität nicht zu unter schätzende wirtschaftliche Bedeutung gewonnen. Die (Rück-) Übertragung eines funktionierenden Selbstinkomatibilitätssystems auf kulturpflanzen erscheint hier als ein Lösungsweg, insbesondere da solche Pflanzen weiterhin fertilen Pollen produzieren könnten, also nicht steril wären. Allerdings ist man heutzutage noch zu weit von einem umfassenden Verständnis der natürlichen Selbstinkompatibilitäts Systeme entfernt, um deren übertragung auf selbstkompatible Methoden, erreichen zu Können.
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    Biologie in unserer Zeit 29 (1999), S. 250-254 
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    Biologie in unserer Zeit 29 (1999), S. 238-246 
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    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Nur bei wenigen Wachstumsprozessen wird eine so groß Genauigkeit gefordert und erreicht wie bei der Abstimmung der Augenlänge auf die Brennweite von Linse und Hornhaut. Wenn das Auge um nur ein Prozent zu lang ist, besteht bereist eine Kurzsichtigkeit (Myopie) von fast einer Dioptrie (dpt). Dabei fällt die Sehschärfe in der Ferne auf etwa ein Drittel. ab. Ist das Auge daggen zu kurz (Weitsichtigkeit-Hyperopie), so kann man zwar in der Ferne meist noch gut sehen, aber die Arbeit in der Nähe wird schwierig, weil mehr Akkommodation aufgebracht werden muß. Die hat nichts mit der “Alterweitsichtigkeit” (Presbyopie) zu tun, wo zwar der Bau des Auges normal ist, aber der altersbedingte Verlust der Akkommodation scharfes Sehen in der Nähe unmöglich macht.Beim Menschen, einigen Afen und Vögeln erreicht die Abbildungsgüte im Bereich der Stelle des schärfsten Sehens (Fovea) die Grenze der physikalischen Möglichkeiten. Nicht optische Schwächen oder Ungenauigkeiten im Bau des Auges, sondern die Lichtbeugung an der Pupille, die zwangsläufig aus den Welleneigenschaften des Lichtes folgt, begrenzen weitere Auflösung. Es ist schwer vorstellbar, wie diese Genaukeit erreicht werden kann, wenn nicht eine Steuerung des Wachstums durch einen rückgekoppeltn Regelkreis erfolgt, der sein Fehlersignal aus dem Netzhautbild entnimmt. Bis vor wenigen Jahren herrschte dennoch die Meinnung vor, daß das Augenlängenwachstum weitgehend genetisch bestimmt ist. Inszwischen ist aber durch Experimente mit brillentragenden Hühnern und Affen gezigt worden, daß “normale” Seherfahrung tatsächlich Voraussetzung für genaues Wachtsum ist. Die zugrundeliegenden Mechanismen sind noch nicht vollständig aufgeklärt, ber bisherige Ergebnisse lassen Schlüsse über mögliche Ursachen von Kurzsichtigkeit zu.
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    Biologie in unserer Zeit 29 (1999), S. 268-277 
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    Biologie in unserer Zeit 29 (1999), S. 286-291 
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    Topics: Biology
    Notes: Kein Schiff überquert sden Ozean ganz ohne blinde passagiere. Muscheln undAsseln bohren sich in Holzplanken. Algen und Seepocken heften sich mi Unterwasserbereich an die Schiffsrümpfe. Planktische sporen und Larven gelangen in das Ballastwasser, das jedes moderne Schiff zur Stabilisierung mit sich führt ‘1 und 3’. Je größer und schneller ein Schiff ist, desto, besser ist dies für die unbeachteten Tramper der Weltmeere. Wer solch eine lange Seereise überlebt, ist auch widerstands- und anpassungsfähig genug, um sich an neuen Küsten zurechtzufinden (Abbildung 2). Günstige Gelegenheiten zur Mitreise ergeben sich auch, wenn Austern oder andere Meerestiere für die Weiterzucht an ferne Küsten versandt werden. Solch ein Handel hat weltweit zugenommen, ebenso wie der interkontinentale Schffsverkehr. Diese Entwicklung führte dazu, daß mehr und mehr Arten zu Bewohnern weit voneinander entfernter Küsten wurden. Der mensch half die natürlichen Ausbreitungsbarrieren zu überwinden und leitete eine Globalisierung der Lebensgemeinschaften an den Küsten ein. - Welchen Umfang aber hat dies im Bereich der Nordsee angenommen? - Welche ökologischen Konsequenzen ergeben sich? - Kann und soll dieser Trend aufgehalten werden? - Diese brisanten Fragen stellen sich weltweit für die Meeresküsten und ebenso auch für die Süßwasser und das Land ‘11-13’.
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    Biologie in unserer Zeit 29 (1999), S. 292-300 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Zu en vielen Schutz- und Verteidigungsstrategien, die von den Organismen entwickelt wurden, um dem Gefressenwerden zu entgehen, Zählen ein sperrigerwerden der Individuen, die Bildung von Panzern, Stacheln und Dornen, das Produzieren und Speichern von schwerverdaulichen Stoffen und Giften, aber auch die Entwicklung eines komplexen verhaltensrepertoires zur Vermeidung von Freßfeinden ‘8’. Bis zur dieses Jahrhunders glaubte man, daß die der Verteidigung dienenden Maßnahmen dauerhaft seien, also im Laufe der Evolution entstanden sind und im Verlauf ddes Lebens eines Individuums zu einem bestimmten Zeitpunkt zur Ausprägung, gelangen, unabhängig von der gerad herrschenden Bedrohung. Heute wissen wir, daß neben einer solchen kionstitutiven Verteidigung in vielen Organismengruppen auch induzierbare Verteidigungsmechanismen existieren, welche nur dann wirksam werden wenn Freßfeinde im Biotop in größerer Dchte auftreten und somit eine ernstzunehmende Bedrohung darstellen. Das Spektrum induzierbarer Feindabwehrmechanismen ist der Palette der kionstitutiven Abwehrmaßnahmen dabei durchaus sehr ähnlich. Der entscheidende Unterschied ist jedoch der, daß der bedrohte Organismus erst auf ein bestimmtes Signal hin von seinem genetisch festgelegten Schutzmechanismus Gebrauch macht. Dadurch werden die Kostenfür die Feindabwehr minimiert. Neben physikalischen Signalen (wie Licht und Temperatur), welche dem Organismus indirekt Auskunft über den Grad einer aktuellen Bedrohung geben können, spielen von den Freßfeinden abgegebene chemische Signale (Kairomone) eine entscheidende Rollen als Auslöser der induzierbaren Verteidigungsmechanismen. An der Aufklärung der chemischen Natur der Kariomione wird zur Zeit intenxiv gearbeitet.
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    Biologie in unserer Zeit 29 (1999), S. 301-306 
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    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Früher wurden über 90% aller Vogelarten als monogam klassifiziert, also als in Einehen lebend ‘5’. Manhatte zwar auch schon damals vereinzelt beobachtet, daß es bei einem Teil dieser Arten manchmal zu Kopulationen mit anderen Individuen als dem Paarpartner kommen kann, maß diesem Verhalten jedoch keine größere Bedeutung bei. Man dachte vielmehr, daß es sichhierbei um eine Art krankhaftes Verhalten handele. Dises Ansicht änderte sich erst, als verschiedene Methoden von Elternschaftsnachweissen gezielt auch bei Vögeln angewenden wurden, um damit Jungtiere zu identifizieren, die aus solchen “Fremdkopulationen resultieren”. Dabei stellte sich heraus, daß die Häfigkeit dieses Verhaltens aufgrund der wenigen Beobachtungen stark unterschätzt worden war und daß bei einer beeinduruckenden Zahl von Vogelarten mit einem monogamen paarungsssytem Jungtiere zu finden sind, die nicht von dem Männchen abstammen, welches die Brut versorgt ‘1’.Die Untersuchungsergebnisse werfen eine Reihe weiterführender evolutionsbiologischer Fragen auf. So stellt sich unter ande rem die Frange nach dem Anpassungswert, halb des Paarbundes. Während der Nutzen f¨r die Männchen auf der hand zu liegen scheint, sie können durch, “Fremdkopulationen” die Anzahl ihrer Nachkommen erhöhen, ist der evlutionsbiologische Vorteil für die Weibchen nicht nämlilck durch Ko pulationen außerhalb des Paarbundes normalerweise nicht die Anzahl ihrer Nachkommen steigern. Sie erhöhen durch Kopulationen mit einem anderen Männchen allenfalls die genetische Variabilität ihree Nachkommen.Ein weiterer Fragenkomplex ergibt sich durch den Umstand, daß brutpflegende Männchen vermeiden sollten, für Jungtiere zu sorgen, die nicht von ihnen selbst stammen. Dises Erwartung basiert darauf, daß Brutpflege gewöhnlich mit Kosten (Enegie und Zeit) verbunden ist: Wenn die Männchen für Jungtiere sorgen, die nicht von ihnen selbst stammen, dann reduzieren sie auf längere Sicht ihren eingene Fortpflanzungserfolg.Im fogenden Aufastz soll versucht werden, die beiden genannten Fragenkomplexe beispielhaft an Untersuchungsergebnissen zum Paarungsverhalten von Kohleisen zu vertiefen. Dabei soll zunächst gezeigt werden, wie mit Hilfe moderner molekulargenetischer Methoden, namentlich dem DNA-Fingerprinting, das Fortpflanzungsverhalten einer Vogelart analysiert werden kann, um dann anschließend auf die eben genannten evolutionsbiologisch relevanten Aspekte einzugehen.
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    Biologie in unserer Zeit 29 (1999), S. 309-309 
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    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Seit 1989 organisieren die beiden Zoologen Prof. Dr. H. K. Schminke aus Oldenburg und Prof. Dr. W. Westheide aus Osnabrück im Sommer einwöchige Intensivkurse zur Vermittlung taxonomisch-ökologischer Kenntnisse über einheimische Tiergruppen. BIUZ wollte mehr über diese Kurse und ihre Ziele wissen.
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    Biologie in unserer Zeit 29 (1999), S. V 
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    Biologie in unserer Zeit 29 (1999), S. IX 
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    Biologie in unserer Zeit 29 (1999), S. 318-318 
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    Biologie in unserer Zeit 29 (1999), S. 330-335 
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    Topics: Biology
    Notes: Blütenpflanzen können nur über ihre Ausbreitungseinheiten oder Diasporen wandern. Das sind Keimkörper, die entweder auf ungeschlechtliche oder geschlechtliche Weise gebildet werden. Im folgenden werden nur die auf geschlechtlichem Weg entstandenen und für die Bluütenpflanzenevolution so wichtigen Ausbreitungskörper diskutiert.Im einfachsten Fall sind die Ausbreitungskörper bei en Blütenpflanzen die Samen selbst. Es können jedoch auch andere Blütenteile (Fruchtblätter, Blütenaches) und sogar Pflanzenteile außerhalb der Blüte (Tragblätter) in den Aufbau der Diasporen einbezogen sein. Mannigfaltig sind dabei die Anpassungen an die verschiedenen Vektoren, die für den Transport der Diasporen verantwortlich sind. Wind, Wasser, Tiere oder die Pflanzen selbst sorgen für eine geeignete Ausbreitung. Oft wirken mehrere Vektoren zusammen. Große Unterschiede bestehen in der Größe der Diasporen und in der Anzahl, die eine Blütenpflanze hervorbringt. experimente deuten jedoch immer wieder auf ein einheitliches Grundmuster der Ausbreitung hin.
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    Biologie in unserer Zeit 29 (1999), S. 346-352 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A Is unerläßliches Nebenprodukt fördert der Steinkohlenbergbau unverwertbares Gestein, die “Berge”. Nur ein geringer Prozentsatz dieses Materials kann wieder unter die Erde zuruckgebracht werden, der weitaus größte Teil wird zu Bergehalden aufgeschüttete man die Halden in Form von Spitzkegeln auf, später wurden sie als terrassierte Tafelberge gestaltet. Heute versucht man, die Bergehalden als eine Art “Landschaftsbauwerk” in die Umgebung zu integrieren.Das nackte, schwarze Gestein der Aufhaldungen findet bei der Bevölkerung keine Akzeptanz, darüber hinaus verursacht eine unbegrünte Bergehalde erhebliche Staubentwicklung. Diese Gründe machten es erforderlich, die Bergehalden zu begrünung bestockte man die Halden mit Gehölzpflanzen, mittlerweile versucht man, die Halden unter Einbeziehung wissenschaftlicher Erkenntnisse nach ökoogischen Gesichtspunkten zu bepflanzen ‘22’. Von besonderem Interesse ist die Frage nach dem Wert dieser Flächen seitens des Naturschutzes. Dies gewinnt insbesondere deshalb an Bedeutung, da gerade in den industriellen Ballungsräumen im städtischen Bereich oft ein großer Verlust an Grünflaächen Stattgefunden hat. Eine Bewertung der Bergehalden hinsichtlich ihres Nutzens für naturschutzorientierte Zwecke kann jedoch nur anhand mehrjähriger Untersuchungen erfolgen.
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    Biologie in unserer Zeit 29 (1999), S. 371-371 
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    Biologie in unserer Zeit 29 (1999), S. 372-373 
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    Biologie in unserer Zeit 29 (1999), S. 374-374 
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    Biologie in unserer Zeit 29 (1999), S. 377-377 
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    Biologie in unserer Zeit 29 (1999), S. 384-384 
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    ISSN: 1432-1890
    Keywords: Key words Glomus clarum NT4 ; Lentil ; Wheat ; Indigenous AMF ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The growth responses of lentil (Lens esculenta L. cv. Laird) and two wheat cultivars (Triticum aestivum L. cv. Laura and Neepawa) to Glomus clarum NT4 in soil containing indigenous arbuscular mycorrhizal fungi (AMF) and fertilized with phosphorus at different (0, 5, 10, 20 ppm) levels was studied in a growth chamber. Soil was inoculated with a monospecific culture of G. clarum NT4 to provide an inoculant:indigenous AMF ratio of ca. 1 : 100. The shoot and root growth, and AMF colonization levels of NT4-inoculated lentil were significantly (P≤0.05) greater than the appropriate control plants in the unfertilized soil at 48 days after planting (DAP). At 95 DAP, NT4 inoculation had significantly increased the shoot dry weight (P≤0.08) and AMF colonization (P≤0.05) of lentil plants receiving 5 mg P kg–1 soil, whereas 20 mg P kg–1 soil reduced the shoot growth of NT4-inoculated plants. The NT4 inoculant had no effect (P≤0.05) on shoot P content, but increased (P≤0.08) the P-use efficiency of lentil plants receiving 5 mg P kg–1 soil. In contrast to the inoculant's effect on lentil, NT4 generally had no positive effect on any of the parameters assessed for wheat cv. Laura at any P level at 48 or 95 DAP. Similarly, there was no positive effect of NT4 on shoot or root growth, or AMF colonization of wheat cv. Neepawa plants at any P level at 48 DAP. However, NT4 inoculation increased the grain yield of Neepawa by 20% (P≤0.05) when fertilized with 20 mg P kg–1 soil. This yield increase was associated with a significant (P≤0.05) reduction in root biomass and a significant (P≤0.05) increase in the grain P content of inoculated plants. Thus, NT4 appears to have a preference for the Neepawa cultivar. Our results show that lentil was more dependent on mycorrhizae than wheat and responded to an AMF inoculant even in soil containing high levels of indigenous AMF. It might, therefore, be possible to develop mixed inoculants containing rhizobia and AMF for field production of legumes.
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  • 153
    ISSN: 1432-1890
    Keywords: Key words AM ; Drought resistance ; Genotype ; Phosphorus ; Triticum durum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The effects of an arbuscular mycorrhizal (AM) fungus and drought stress on the growth, phosphorus, and micronutrient uptake of two wheat genotypes exhibiting differences in drought resistance were investigated. Plants were grown on a low P (4 mg kg–1 soil) silty clay (Typic Xerochrept) soil-sand mix. Mycorrhizal infection was higher under well-watered than under dry soil conditions and the drought-resistant genotype CR057 had a higher mycorrhizal colonization than the drought-sensitive genotype CR006. Total and root dry matter yields and total root length were higher in mycorrhizal than in nonmycorrhizal plants of both genotypes. CR057 had higher total dry matter but not root dry matter than CR006 plants. The enhancement in total dry matter due to AM inoculation was 42 and 39% under well-watered and 35 and 45% under water-stressed for CR057 and and CR006, respectively. For both genotypes, the contents of P, Zn, Cu, Mn, and Fe were higher in mycorrhizal than in nonmycorrhizal plants and higher under well-watered than under dry soil conditions. The enhancement of P, Zn, Cu, Mn, and Fe uptake due to AM inoculation was more pronounced in CR006 than in CR057, particularly under water-stressed conditions. Thus CR006 benefitted from AM infection more than the CR057 under dry soil conditions, despite the fact that CR057 roots were highly infected. It appears that CR006 is more dependent on AM symbiosis than CR057.
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  • 154
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    Biology and fertility of soils 24 (1997), S. 1-12 
    ISSN: 1432-0789
    Keywords: Phosphorus ; Isotope techniques ; Forest P immobilization ; Soil-plant system ; Root activity Nutrient cycling ; Organic P sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A sound understanding of nutrient dynamics in ecosystems is required in order to manage these systems on a sustainable basis. A valuable approach to studying phosphorus (P) dynamics in soil-plant systems has been the use of P isotope techniques. Isotope techniques used for studying P cycling in agricultural and forest soils are reviewed in this paper with particular reference to advances made in the part 15 years. A brief discussion of the properties of P isotopes and their measurements is included together with techniques for measuring exchangeable P in the soil, dissolution and decomposition rates of inorganic and organic P sources applied to the soil, rates of organic P immobilization and mineralization, rates of P release and retention in the soil, root activity and lifter decomposition rates in forest soils, and gene probing and hybridization. Basic principles, assumptions, procedures, limitations and merits of methods are discussed. These techniques have served as or have the potential to be valuable tools for advancing our understanding of P dynamics in soil-plant systems, and for studying the molecular characteristics of microbial communities in relation to the cycling of nutrients in the soil.
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  • 155
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    Biology and fertility of soils 24 (1997), S. 183-187 
    ISSN: 1432-0789
    Keywords: Key words Enzyme ; Hydrolysis ; Ion association ; complex ; Phosphorus ; Soil solution ; Podzol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphate in solutions of model esters and polyphosphates (glucose phosphate, inositol hexaphosphate, pyrophosphate, ribonucleic acid, tripolyphosphate and trimetaphosphate) was quantitatively released in 〈6 h by acid phosphatase or phytase at pH 5.0. Interference from insoluble, ion association complexes formed between protein in the enzymes and the phosphomolybdenum blue during the colorimetric determination of the molybdate reactive phosphorus released was removed by adding dimethyl sulphoxide. Filtered (0.45 μm) soil solution from a peaty soil contained 590 μg dm–3 total dissolved phosphorus (TDP), of which 13% was molybdate reactive phosphorus (MRP), 26% dissolved organic phosphorus (DOP) and 61% dissolved condensed phosphorus (DCP). When acid phosphatase was added to the soil solution under the conditions used to hydrolyse the model compounds, MRP increased to 54% of the TDP in about 10 h and then remained constant. From a mass balance, at least 25% of the DCP was hydrolysed. Incubation of the soil solution at 35°C without enzyme increased MRP to 44% of the TDP, reflecting native enzyme activity. Soil solution containing a higher concentration of TDP (1.27 mg dm–3) was also obtained. The distribution of MRP, DOP and DCP fractions was similar but acid phosphatase hydrolysed a greater proportion of the P and MRP increased to 64% of the TDP and at least 40% of the DCP was hydrolysed. The results of hydrolysis with phytase were similar to those with acid phosphatase. The protection of part of the DOP or DCP fraction from hydrolysis was likely caused by occlusion within colloids or the existence of P compounds unlike those of the model substrates.
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  • 156
    ISSN: 1432-0789
    Keywords: Key words Acidic forest soil ; Phosphorus ; Coal combustion by-product ; Carbon cycling ; Cellulose ; Microbial biomass ; Liming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphate rock (PR), limestone, coal combustion by-product (CCBP) high in Ca and high organic manures are potential amendments for increasing agricultural production in the acidic soils of the Appalachian region. The objective of this study was to examine effects of PR, CCBP and cellulose addition on soil microbial biomass in an acidic soil based on the measurement of soil microbial biomass P (P mic) and on the mineralization of organic matter. Application of PR alone or in combination with CCBP increased P mic. The P mic was far less when the soil received PR in combination with limestone than with PR application alone or PR in combination with CCBP. Either CCBP or limestone application alone considerably decreased P mic in the soil due to reduced P solubility. Cellulose addition alone did not increase P mic, but P mic was significantly increased when the soil was amended with cellulose in combination with PR. The decomposition of added cellulose was very slow in the soil without PR amendment. However, mineralization of both native organic matter and added cellulose was enhanced by PR application. Mineralization of organic matter was less when the soil was amended with PR in combination with high rates of CCBP (〉 2.5%) because PR dissolution varied inversely with amount of CCBP addition. Overall, CCBP had no detrimental effect on soil microbial biomass at low application rates, although, like limestone, CCBP at a high rate may decrease P mic in P-deficient soils through its influence on increased soil pH and decreased P bioavailability in the soil. Application of PR to an acidic soil considerably enhanced the microbial activity, thereby promoting the cycling of carbon and other nutrients.
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  • 157
    ISSN: 1432-1939
    Keywords: Key words Grasslands ; Mineral nutrition ; Allocation ; Phosphorus ; Adaptations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Waterlogging frequently reduces plant biomass allocation to roots. This response may result in a variety of alterations in mineral nutrition, which range from a proportional lowering of whole-plant nutrient concentration as a result of unchanged uptake per unit of root biomass, to a maintenance of nutrient concentration by means of an increase in uptake per unit of root biomass. The first objective of this paper was to test these two alternative hypothetical responses. In a pot experiment, we evaluated how plant P concentration of Paspalum dilatatum, (a waterlogging-tolerant grass from the Flooding Pampa, Argentina) was affected by waterlogging and P supply and how this related to changes in root-shoot ratio. Under both soil P levels waterlogging reduced root-shoot ratios, but did not reduce P concentration. Thus, uptake of P per unit of root biomass increased under waterlogging. Our second objective was to test three non-exclusive hypotheses about potential mechanisms for this increase in P uptake. We hypothesized that the greater P uptake per unit of root biomass was a consequence of: (1) an increase in soil P availability induced by waterlogging; (2) a change in root morphology, and/or (3) an increase in the intrinsic uptake capacity of each unit of root biomass. To test these hypotheses we evaluated (1) changes in P availability induced by waterlogging; (2) specific root length of waterlogged and control plants, and (3) P uptake kinetics in excised roots from waterlogged and control plants. The results supported the three hypotheses. Soil P avail-ability was higher during waterlogging periods, roots of waterlogged plants showed a morphology more favorable to nutrient uptake (finer roots) and these roots showed a higher physiological capacity to absorb P. The results suggest that both soil and plant mechanisms contributed to compensate, in terms of P nutrition, for the reduction in allocation to root growth. The rapid transformation of the P uptake system is likely an advantage for plants inhabiting frequently flooded environments with low P fertility, like the Flooding Pampa. This advantage would be one of the reasons for the increased relative abundance of P. dilatatum in the community after waterlogging periods.
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  • 158
    ISSN: 1573-5052
    Keywords: Deciduous ; Evergreen ; Leaf nutrient levels ; Nitrogen ; Phosphorus ; Quercus ; Soil fertility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf and soil nutrient levels interact with and may each influence the other. We hypothesize that to the extent soil fertility influences the nutritional state of trees, soil fertility should correlate with summer leaf nutrient levels, whereas to the extent that trees influence soil nutrient levels, the quality of leaf litterfall should correlate with soil fertility. We examined these correlations for five sympatric oak species (genus Quercus) in central coastal California. Soil fertility, including both nitrogen and especially phosphorus, correlated significantly with summer leaf nutrient levels. In contrast, phosphorus, but not nitrogen, in the leaf litterfall correlated positively with soil nutrients. These results suggest that soil nitrogen and phosphorus influence tree nutrient levels and that leaf phosphorus, but not leaf nitrogen, influence soil fertility under the trees. Feedback between the soil and the tree for phosphorus, but not nitrogen, is apparently significant and caused by species-specific differences in leaf quality and not by litterfall quality differences within a species. We also compared functional differences between the evergreen and deciduous oak species at our study site. There were no differences in soil nitrogen and only small differences for soil phosphorus between the phenological types. Differences in leaf nutrient concentration were much more pronounced, with the evergreen species having substantially lower levels of both nitrogen and phosphorus. Evergreen species conserved more phosphorus, but not more nitrogen, than the deciduous species, but there was no consistent relationship between retranslocation and either soil nitrogen or phosphorus. These results do not support the hypothesis that evergreenness is an adaptation to low soil fertility in this system.
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  • 159
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    Plant ecology 130 (1997), S. 143-153 
    ISSN: 1573-5052
    Keywords: Community boundaries ; Fynbos ; Nitrogen ; Phosphorus ; Soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between changes in soil nutrient characteristics and fynbos community boundaries was investigated near Cape Agulhas, South Africa. Soil characteristics relating to total nutrient content (pH, total N and total P, organic carbon, and various cations) were assessed at sites along three transects crossing the boundaries between five plant communities. Dynamics of available N and P in soils of three communities were studied in the field over one year, using ion-exchange resins. There was a wide range in the degree of change in soil nutrient content across different community boundaries. The characteristics that varied most were pH, total N, Ca and total P. Differences in available nutrients among soils indicated that the communities in this landscape were associated with a mosaic of N and P availability. It is proposed that spatial variation in soil nutrient availability rather than total soil nutrient contents may be important in explaining landscape-level species distributions and community composition in nutrient-poor mediterranean-climate ecosystems.
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  • 160
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    Water, air & soil pollution 99 (1997), S. 283-295 
    ISSN: 1573-2932
    Keywords: Sedimentation ; Iron ; Aluminum ; Fractionation ; Organic material ; Phosphorus ; Humic lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The sedimentation of organic, amorphous oxides, crystalline oxides and crystalline silicate species of Fe and Al was investigated in humic Lake Örträsket. The covariation with C, N and P sedimentation also was studied. The results showed a strong temporal variation in the occurrence of different Fe species. During high discharge, such as in spring, Fe mostly occurred as crystalline Fe-silicate species, while the amorphous form dominated at other times of the year. Al generally sedimented as crystalline Al-silicate species (95%). Amorphous Fe species showed a strong relation with organic C and N, suggesting an association between organic material and amorphous Fe oxides. P was not as strongly related to amorphous Fe, probably as a result of apatite or clay bound-P species sedimentation.
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  • 161
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    Water, air & soil pollution 99 (1997), S. 283-295 
    ISSN: 1573-2932
    Keywords: Sedimentation ; Iron ; Aluminum ; Fractionation ; Organic material ; Phosphorus ; Humic lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The sedimentation of organic, amorphous oxides, crystalline oxides and crystalline silicate species of Fe and Al was investigated in humic Lake Örträsket. The covariation with C, N and P sedimentation also was studied. The results showed a strong temporal variation in the occurrence of different Fe species. During high discharge, such as in spring. Fe mostly occurred as crystalline Fe-silicate species, while the amorphous form dominated at other times of the year. Al generally sedimented as crystalline AI-silicate species (95%). Amorphous Fe species showed a strong relation with organic C and N, suggesting an association between organic material and amorphous Fe oxides. P was not as strongly related to amorphous Fe, probably as a result of apatite or clay bound-P species sedimentation.
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  • 162
    ISSN: 0009-2940
    Keywords: Alkoxopalladium(II) ; Conformational analysis ; Hydrogen bonding ; Two-dimensional and cage structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of palladium acetate with two equivalents of di- and triethanolamines RN(CH2CH2OH)2 in the presence of a base affords the new chelate-stabilized alkoxo Pd(II) complexes [Pd(OCH2CH2N(R)CH2CH2OH)2] [R = Me (1), Et (2), n-Bu (3), benzyl (4) or CH2CH2OH (5)]. These N,O-ligated complexes are isolated in high yield as yellow, crystalline solids and are thermally stable despite the presence of several β-hydrogen atoms in the ligand system. Both complexes possess a square-planar palladium coordination geometry with the two oxygen atoms positioned mutually trans. The most notable difference in the molecular structures is that 1 forms a two dimensional network of intermolecular O-H≡O hydrogen bonds, whereas 5 forms intramolecular O-H⃛O hydrogen bonds, which cage the palladium center. In solution 1-4 exist as a diastereoisomeric mixture (a racemic enantiomeric pair SNSN, RNRN and a mesomeric form RNSN) in a 1:1 molar ratio, and this ratio is independent of temperature in nonalcoholic solvents, When complexes 1-4 are dissolved in protic solvents (e.g. MeOH) the diastereomeric excess is temperature-dependent due to an exchange process between the meso diastereoisomer and the (racemic) enantiomeric pair. Thermodynamic parameters for this process in a mixture of MeOH-toluene have been determined with NMR and show this process to be influenced by the steric nature of the alkyl substituent (R) on nitrogen. A conformational analysis based on 1H-NMR coupling constants within the N,O-chelate ring of complexes 1-4 provides details on the solution structure of the ring in both diastereoisomers.
    Additional Material: 9 Ill.
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  • 163
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 13-22 
    ISSN: 0009-2940
    Keywords: Carbamates ; Catalysis ; Substituted nitrobenzenes ; Palladium ; Reductive carbonylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The palladium-catalyzed reductive carbonylation of ortho and para-substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1, 10-phenanthroline)2(triflate)2 catalyst system, the scope of the reaction has been studied. Substrates with electron-donating substituents at the para position were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. the selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron-withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at the ortho position of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion ot the nitro group. Especially with 4-nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis for N-protected amines containing carboxylic acid function.
    Additional Material: 1 Ill.
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  • 164
    ISSN: 0009-2940
    Keywords: Isothiazole complexes ; Dinuclear silver(I) complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of isothiazole-based potential ligands bearing substituents with additional donor sites in the 5-position of the heterocycle was synthesized [3-Me-5-R-C3HNS; R = CH=N(CH2)2py (1), CH=NCH2py (2), CH2N(CH2CH2NEt2)2 (4), (CH2)2SMe (5)]. Upon reaction with AgO3SCF3 they formed complexes [(1)AgOSO2CF3]2 (6), [(2)AgOSO2CF3]2 (7), [(4)Ag]2+2(O3SCF-3)2 (8) and [(5)AgOSO2CF3]2 (9), respectively. 6, 8 and 9 were shown by X-ray structural analyses to consist of dimeric units L2Ag2+2, either discrete (8), coordinated by terminal CF3SO-3 units (6). In 8 and 9 the isothiazole moiety is bonded to the metal center via the ring-N. The coordination potential of the isothiazole heterocycle is discussed.
    Additional Material: 5 Ill.
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  • 165
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 115-118 
    ISSN: 0009-2940
    Keywords: Gold complexes ; Bromonium complex ; Halogenonium complex ; Halogen, two-coordinate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of (R3P)AuX (X = Cl, Br, I) with [(R3P)Au]+ BF-4 obtained from (R3P)AuCl and AgBF4 in tetrahydrofuran, lead to cationic binuclear gold(I) complexes of the general formula ([(R3P)Au]2X}+ BF-4. A number of chloro- (R = Ph, o-Tol, Mes, Bzl, Et), bromo- (R = Ph, o-Tol, Mes) and iodo-bridged (R = Ph, Mes) complexes of this type have been isolated and identified on the basis of their analytical and spectroscopic data. The crystal structure of bis[(triphenylphosphane)gold(I)]bromonium tetrafluoroborate was determined by single-crystal X-ray diffraction. The cations contain two-coordinate bromine atoms with an Au-Br-Au angle of 96.83(3)°.
    Additional Material: 1 Ill.
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  • 166
    ISSN: 0009-2940
    Keywords: Arene complexes ; Ruthenium compounds ; Electrophilic substitution ; Lithiation ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral or achiral (arene)(COD)Ru complexes can be made by replacing the η6-ligands of (η4-1,5-COD)(η6-1,3,5-cyclooctatriene)Ru (1) or (η4-1,5-COD)(η6-naphthalene)Ru (2) by a suitable arene. This well known reaction has been extended to mono- and dibromoarenes and we report a novel route to substituted (arene)(COD)Ru species, utilizing (bromoarene)-(COD)Ru as starting materials. These facilitate a rapid bromine-lithium exchange reaction with nBuLi at low temperatures and the lithiated species react readily with alkyl chloroformates as electrophiles. By using chiral electrophiles [alkyl = (-)-menthyl] enantiomerically pure or diastereomeric complexes containing CO2R* groups are formed, depending on the symmetry of the original complex. A diastereomeric 1:1 mixture was separated by recrystallization. All (arene)-(COD)Ru complexes tested so far are useful as catalysts for the hydrogenation of simple alkenes at room temperature.
    Additional Material: 3 Ill.
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  • 167
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 145-154 
    ISSN: 0009-2940
    Keywords: Fluorocarbons ; C-F bond activation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The main reaction pathways which lead to the breaking of C-F bonds in perfluoroalkanes and -arenes are discussed. Emphasis is placed on recent developments and on the mechanistic patterns that emerge.
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  • 168
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metal-vapor reactions of Co atoms with 1,3-tBu2CpH (1a), 1,3-tBu2CpH (1a), 1,2,4-tBu3CpH (1b) and EtMe4CpH (1c) are described. With 1a the two mononuclear complexes [(η5-tBu2Cp) (η4-tBu2-1,3-cyclopentadiene)Co] (2a) and [(η5-tBu2Cp)2Co] (3a) were isolated, together with the dinuclear cobalt cluster [{(η5-tBu2Cp)Co}2H3] (4a) and trace amounts of the tetranuclear cluster [{(η5-tBu2Cp)CoH}4] (5a). The molecular structures of 3a and 4a were determined by X-ray diffraction. Reaction of 1b with Co atoms afforded a single product, the dinuclear cluster [{(η5-tBu3Cp)Co}2H3] (4b), whose molecular structure was determined by single-crystal X-ray diffraction. Both, 4a and 4b exhibit extremely short Co-Co distances [2.244(1) (4a) and 2.242(1) Å (4b)], as found for the Me5Cp analog [{(η5-Me5Cp)Co}2H3] (4c). Reaction of an isomeric mixture of Me4EtCpH (1c) with Co atoms furnished the mononuclear sandwich [ (η5-Me4EtCp)(η4-Me4Et-1,3- cyclopentadiene)Co] (2b), the trinuclear hydridocobalt cluster [{(η5-Me4EtCp)Co}3H4] (6a) and the tetranuclear hydridocobalt cluster [{(η5-Me4EtCp)Co}4H4] (5c). The molecular structure of 5c was determined by X-ray crystallography and revealed a tetrahedral arrangement of the cobalt atoms. The electrochemical behavior of the dinuclear complexes 4a-4c was studied by cyclic voltammetry. Reversible redox couples were found for all three compounds, with a correlation between the degree of alkyl substitution and their respective cathodic shifts. Compounds 4a and 4b react with CO to yield the mononuclear and dinuclear complexes [ (η5- CpR)Co(CO)2] (R=1,3-tBu2, 1,2,4-tBu3) (7a and 7b) as well as [{(η5-CpR)CO}2(CO)2] (8a and 8b). Reaction of the trinuclear hydridocobalt cluster 6a and its Me5Cp analog 6b with AgBF4 in the presence of PEt3 yielded the heteronuclear clusters [{η5-Me4CPR)Co}3AgP(Et)3H4]+[BF4]- (R=Et, Me) (9a and 9b). 9a was structurally characterized by X-ray crystallography.
    Additional Material: 8 Ill.
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  • 169
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 45-48 
    ISSN: 0009-2940
    Keywords: Metallated methyl isopropenyl ether ; Tetrahydrofurans ; 1-Oxabicyclo[4.3.0]heptanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl isopropenyl ether (1) has been metallated at low temperature with a 1:1 molar mixture of n-BuLi/t-BuOK in THF-hexane, and subsequently functionalized with a variety of electrophilic reagents. At temperatures higher than - 30°C, the metallated methyl isopropenyl ether (2) decomposes with formation of allene. When the suspension of 2 is allowed to warm up to room temperature in the presence of an additional equivalent of n-BuLi, the intermediary allene is converted into 1-propynyllithium (2c), which reacts with propylthiocyanate to give 1-propylthio-1-propyne (4). Some of the functionalization products were subjected to acidic hydrolysis affording the expected methyl ketones.
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  • 170
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 55-62 
    ISSN: 0009-2940
    Keywords: Diastereoselective hydrogenation ; Folic acid ; Immobilized optically active rhodium(I)/diphosphane catalysts ; Leucovorin ; HPLC analysis of 5-formyltetrahydrofolic acid derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the hydrogenation of the C=N bonds in the pyrazine ring of the vitamin folic acid (1) optically active rhodium(I)/diphosphane complexes immobilized on supports such as silica gel or Al2O3 were used. The reduction was carried out at 50 bar hydrogen pressure in an aqueous solution buffered to pH 7. Thus, 5,6,7,8-tetrahydrofolic acid (2) was obtained which contains a new asymmetric center at C-6 of the pterine system. Therefore, in combination with the (S) configuration of the natural L-glutamic acid part of the molecule two diastereomers with (6S,S) and (6R,S) configuration arise. The relatively unstable tetrahydrofolic acid (2) was converted into its 5-formyl derivative folinic acid (4) by treatment with methyl formate/formic acid in a 5:1 mixture of DMSO/pyridine. The Ca salt of folinic acid (4) is the widely used drug leucovorin. The diastereomers were separated by silica gel HPLC. To the column bovine serum albumine (BSA) is covalently bound. With optically active rhodium(I)/diphosphane catalysts, immobilized on silica gel supports, a diastereoselectivity of up to 90% could be achieved in the hydrogenation of folic acid (1).
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  • 171
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 405-408 
    ISSN: 0009-2940
    Keywords: Hexahydro-closo-hexaborates ; Boron ; Bridging ligands ; NMR spectroscopy ; Gold ; Copper ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By reaction of (PPh3)3 CuCl and PPh3AuCl with [B6H6]2- in organic media, dinuclear complexes are formed containing the hexaborate as a bridging ligand coordinated to the metal centers by opposite B3 facets of the B6 cluster in a trihapto mode. This is verified by single-crystal X-ray structural analysis of the isotypical (Paā) compounds [Cu2μ-bis-η3-B6H6)(PPh3)2] (1) and [Au2(μ-bis-η3-B6H6)(PPh3)2)] (2) which showed the metal centers to be very close to the B3 plane [1.92 (1), 2.10 (2) Å. The 11B NMR spectra of the two compounds feature doublets, at δ= -15.32 in 1 and at -11.51 in 2, which are significantly shifted downfield in comparison to [B6H6]2- (δ= -17.2).
    Additional Material: 2 Ill.
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  • 172
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 425-429 
    ISSN: 0009-2940
    Keywords: Silver complexes ; Crown compounds ; Thioethers ; 1,3-Dithioles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination chemistry of two crown thioethers 2,5,8,10,12-pentathiabicyclo[7.3.0]dodeca-1)9)-ene-11-thione (L) and -11-one (L') with Ag1 has been investigated by structural methods. Both thioethers act as tridentate ligands coordinating the silver ion in a trigonal fashion. In the case L, the 11- thione sulfur is coordinated additionally by another silver ion, to yield a polymeric chain with a distorted-tetrahedral geometry about the metal ion. Despite differing only in its carbonyl chalcogen, L' forms six-coordinated, monomeric complexes.
    Additional Material: 3 Ill.
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  • 173
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 433-442 
    ISSN: 0009-2940
    Keywords: Metallobiosites ; Metalloproteins ; Metalloenzymes ; Dinucleating ligands ; Transition metals ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Awareness of the asymmetric nature of numerous dinuclear metallobiosites and of the ability of the individual metal ions to have quite distinct roles in the functioning of the metalloenzyme concerned has led to a search for carefully designed unsymmetric dinucleating ligands that will give dinuclear complexes capable of acting as models for the metallobiosites. This review surveys progress made in the design and synthesis of complexes capable of serving as models for donor atom, coordination number and geometric asymmetries found at dinuclear metal centres.
    Additional Material: 2 Ill.
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  • 174
    ISSN: 0009-2940
    Keywords: Alkali metal organophosphanylamide ; Carbon-potassium bonding ; Phosphazane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metalation of bis(diphenylphosphanyl)amine [HN-(PPh2)2,1 with KOtBu at 95°C in toluene affords a pale yellow precipitate of potassium bis(diphenylphosphanyl)amide (3a). On addition of liquid N,N,N′,N“,N“-pentamethyldiethylenetriamine (PMDTA, 4) the precipitate dissolves in toluene at 115°C to give a yellow solution, from which yellow-green blocks of [(Ph2P)2NK·PMDTA] (3b) are obtained. X-ray analysis reveals that the coordination sphere of potassium consists of the chelating triamine ligand and [N(PPh2)2]- as N-donor as well as η1 and η2 C-donor with two phenyl fragments. No phosphorus coordination of [N(PPh2)2]- is observed.
    Additional Material: 2 Ill.
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  • 175
    ISSN: 0009-2940
    Keywords: Phosphaalkynes ; Triorganoaluminium compounds ; Cooligomerization ; Cage compounds ; Aluminium compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When the trialkylaluminium reagents 5 are allowed to react with phosphaalkynes 4 in n-pentane, a highly selective phosphaalkyne cyclotrimerization with incorporation of two organometallic units occurs (→ 6). The tetracyclooctane derivatives 6a-e represent the first examples of phosphorus-aluminium-carbon cage compounds. The polycyclic products 6 are able to function as ligands in transition-metal complexes (→ 7), which is illustrated by the reactions of 6b, c with nonacarbonyldiiron and pentacarbonyl(tetrahydrofuran)tungsten, respectively.
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  • 176
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 283-289 
    ISSN: 0009-2940
    Keywords: Zinc ; Sulfonate ligands ; Perchlorates ; Coordination modes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempts are reported to incorporate sulfonate and perchlorate anions as ligands in zinc complexes of tripodal ligands. Using tris(benzimidazolylmethyl)amine (BIMA) only the aqua complexes [ (BIMA)Zn-OH2](RSO3)(ClO4) and [(BIMA)Zn-OH2](RSO3)2(R=CH3, CF3, p-tolyl) were accessible. Using substituted pyrazolylborates (Tp*), the same three sulfonate anions were found to be ligands in the complexes Tp*Zn-OSO2R. Spectroscopic evidence for perchlorate coordination in Tp*ZnClO4 · 2 DMSO conflicts with crystallograpic evidence against it in Tp*ZnClO4 · pyridine. The crystal structures of [(BIMA)Zn-OH2](CH3SO3)2, TpCum,MeZn-OS02CH3, TPtBu,MeZn-OSO2C6H4-p-CH3, and [TpCum,MeZn · NC5H5]ClO4 were determined.
    Additional Material: 4 Ill.
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  • 177
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 295-298 
    ISSN: 0009-2940
    Keywords: Rhenium ; Oxides ; Alkyl ligands ; Dirhenium compounds ; Metal-metal interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Most alkylrhenium(VII) oxides, e.g. ((cyclo)-C3H5)Re03 (2) are rather sensitive to temperature and moisture with the prominent exception of methyltrioxorhenium (1). The corresponding alkylrhenium(VI) oxides of formula [RR′(O)- Re(μ-O)]2 [R=R′=(cyclo)-C3H5 (3), iPr (4); R=CH3, R′=C2H5 (5), R=CH3, R′=iPr (6)] are much more stable in this regard. They can be handled in air at room temperature. They were synthesized from Re207 and dialkylzinc precursors, fully characterized and are available in much higher yields than their ReVII congeners. Mixed tetraalkyltetraoxodirhenium(VI) complexes (R # R′) synthesized from 1 and dialkylzinc compounds form as a mixture of cis/trans isomers. They are oily liquids at room temperature. The Re=O and Re-Re stretching force constants as a measure of the bond strengths, were determined from IR and Raman data.
    Additional Material: 3 Tab.
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  • 178
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 335-340 
    ISSN: 0009-2940
    Keywords: Allylsilanes ; Superbases ; Metalations ; Stereoselectivity ; Cyclizations ; Silicon ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When treated with two equivalents of a butyllithium/potassium tert-butoxide mixture, terminal olefins carrying unprotected hydroxy or carboxy groups generate allylmetal intermediates which can be trapped with chlorotrimethylsilane to afford functionalized (Z)-2-alkenyltrimethylsilanes. One equivalent of the superbasic reagent suffices if the unsaturated alcohols are first protected as acetals before being subjected to the metalation/silylation/hydrolysis sequence.
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  • 179
    ISSN: 0009-2940
    Keywords: Metallacycloalkanes ; Metallacycloalkenes ; Osmium ; Iron ; Cyclic ketones ; Metallacycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the bis(triflates) [F3CSO3-(CH)m-O3SCF3] [m = 5-10, 12, 14, 16 (1a-i) with Na2[Os(CO)4] in dimethyl either affords the osmacycloalkanes 2a, 2b and 2f-i (m = 5, 6, 10, 12, 14, 16), diosmacycloalkanes 3a-i (m = 5-10, 12, 14, 16), and triosmacycloalkanes 4a-i (m = 5-10, 12, 14, 16). The structure of 3f was investigated by an X-ray structural analysis. This 22-membered disomacycle crystallizes in the space group Pā with Z = 1. If the unsaturated cis-4-octen-1,8-diyl bis(trifluoromethanesulfonate) (5) is treated with Na2[Os(CO)4] the diosmacyclooctadeca-5,14-diene 6 is obtained. By treating the bis(triflates) 1a, b with Na2[Fe(CO)4] the corresponding ferracycloalkanes are formed only in situ. Insertion of carbon monoxide into the M-C σ bonds leads to the cyclic ketones 7a, d and to the diketone 8d.
    Additional Material: 4 Ill.
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  • 180
    ISSN: 0009-2940
    Keywords: Pyrrolidinephosphanes ; 3-Hydroxypyrrolidine ; 3-Diphenylphosphanylpyronlidine ; Salt effects ; Polymorphism ; Homogeneous catalysis ; Palladium ; Asymmetric catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of both enantiomers of 3-diphenylphosphanulpyrrolidiine (2) and several N-substituted derivatives together with two PdIi complexes of this ligand is reported. Form L-malic acid and L-hydroxyproline both enantiomers of 3-hydroxypyrrolidine are prepared without any problems due to epimerization. KPPh2 in the presence of LiCl is shown to be the most effective reagent for the synthesis of 2. The reported X-ray structure determination sof Pdl2 complexes show a rather rigid bicyclic hetero-norbornane skeleton. The flexibility of the other parts of the molecules is obvious in several polymorphs revealed by this method. This polymorphism is additionally investigated by a 31P-CP-MAS study. From solution 1-, 13C- and 31P-NMR studies it is concluded that the bicyclic hetero-norbornane skeleton is retained in solution.
    Additional Material: 3 Ill.
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  • 181
    ISSN: 0009-2940
    Keywords: Trichlorosilylation ; Dichlorophosphanes ; Silylphosphanes ; Amino(silyl)phosphanes ; Silicon /Reductions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of hexachlorodisilane and of trichlorosilane/triethylamine with alkyl-and dialkylaminodichlorophosphanes RPCl2 1a-i [R = iPr: a; (Me3Si)2CH: b; R=1-adamantly: c: R=tBu: d; R=Et2N: e; R=iPr2M: f] furnish bis(trichlorosilyl)-phosphanes RP(SiCl3)2 3a-f. However, when less bulky substituents are attached to the phosphorus atom, so that there is little steric crowding, the double reductive silylations leading from 1 to 3 are accompanied by side reactions and decomposition of 3. Therefore, only 3b, 3c, 3d, and 3f wre isolated in a pure state. These compounds are more readily prepared by the; trichlorosilane/triethylamine method. 1H-, 31P- and 29Si-Nmr spectra confirm their constitution. The structure of solid 3f, the first aminobis(trichlorosilyl)phosphane, was determined by X-ray crystallography. 3f contains a phosphorus atom in a pyramidal environment surrounded by two silicon atoms and a planar nitrogen atom of the diisopropylamino group.
    Additional Material: 2 Ill.
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  • 182
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 417-420 
    ISSN: 0009-2940
    Keywords: Gallium ; Low-valent compounds ; Gallium-gallium bond ; Terminal triphenytriazenido ligand ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrakis[bis(trimethylsilyl)methyl]digallane (4) 1 reacts with 1,3-diphenyltriazene to yield two compounds, which were both characterized by a crystal structure determination. The gallium-gallium bond is retained in the yellow derivate [(H5C6)2N3](R)Ga-Ga(R)[N3(C6H5)2 2 [R = CH(SiMe3)2], which is formed by a ligand exchange reaction and shows two terminal chelating triazenido ligands besides two bis(trimethylsilyl)methyl groups; the Ga—Ga bond length is 245.79(6) pm. The second product is the orange dialkyl(diphenyltriazenido)gallium derivative R2Ga[N3(C6H5)2] 3, where the triazene has reacted as an oxidant by the cleavage of the Ga—Ga bond and probably by release of elemental hydrogen.
    Additional Material: 2 Ill.
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  • 183
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 463-472 
    ISSN: 0009-2940
    Keywords: Hypervalent compounds ; Tellurium ; Polycations ; Molecular Orbital Theory ; Band structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Approximate MO and band structure calculation are used to analyze the bonding in the recently synthesized paramagnetic, semiconducting phase [Te15Br4]2+. The [Te15Br4]2+ chains are very similar to those in the tellurium subhalide Te2Br. The electronic structure and bonding within these chains is analysed and the possibility of hypervalency in both [Te15Br4][MoOBr4]2 and Te2Br is discussed. The bonding in the classically hypervalent molecule TeBr42- and a model Te3Br24- is compared to that of the infinite system. Our calculations indicate that both [Te15Br4][MoOBr4]2 and Te2Br contain weakly hypervalent Te atoms and that the interesting electronic properties of [Te15Br4][MoOBr4]2 arise within the distinct sublattices, which do not interact significantly.
    Additional Material: 12 Ill.
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  • 184
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 479-488 
    ISSN: 0009-2940
    Keywords: Heterobimetallic complexes ; Carbene complexes ; Alkynes ; Coupling reaction ; Bridging ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sequential reaction of the dimethylamino(trimethylsilylethylnyl)carbene complexes [(CO)5M'=C(NMe2)C≡CSiMe3] [M' = W (1a)] with KF/THFMeOH, nBuLi and transition metal halides, [XMLn], affords heterobimetallic propynyliden complexes of the type [(CO)5M'=C(N-Me2)C≡CMLn] [MLn = Ni(PPh3) Cp (4a, b). Ni(PMe2Ph)2- {Mes) (Mes=2,4,6-C6H2Me3) (5a), Rh(CO)(PPh3)2 (6a), Fe(CO)2Cp (7a,b)]. In contrast, reaction of 1a with MeLi · LiBr and [IFe(CO)2Cp] yields the novel N-metallated complex [(CO)5W=C{N(ME)Fe(CO)2Cp}C≡CSiMe3] (8a). The complexes [(CO)5M'=C(NMe2)C≡CMLn=Fe(CO)2Cp (7a, b), Ru(CO)2Cp (10a,b), Ru(CO)(PPh3)Cp (11a), Mn(CO)5 (12a), Re(CO)5 (13a)] are accessible by Pd-catalyzed coupling of the C-stannylated carbene complexes [(CO)5M'=C-(NMe2)C≡CSnBu3] (9a, b) with [XMLn]. The related monomethylaminocarbene complexes [(CO)5M'=C(NHMe)C≡ CSnBu3] (16a, b), obtained by stannylation of [(C))5M'=C(NHMe)C=CH] (15a, B) with Bu3SnNEt2, react with [IFe(CO)2Cp] to give the bimetallic complexes [(CO)5M'=C(NHMe)C≡CFe(CO)2Cp] (17a, b). The complexes 4a, 5a, 7a and 10a were characterized by X-ray structural analysis. The spectroscopic and structural data suggest that the two metal centers in 4-7, 10-13, and 17 interact only weakly.
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  • 185
    ISSN: 0009-2940
    Keywords: Rhenium ; Technetium ; 8a-Amino-6-methyl-ergoline ; Chelates ; Structure elucidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Current research in radiopharmaceutical chemistry is aimed at the design of technetium-based receptor-binding radiotracers because of the excellent nuclide properties of the isotope 99mTc. Tc tracers and the corresponding complexes of rhenium, as the inactive surrogate of Tc, are required to imitate organic agonists or antagonists of the receptor. We have started studies with ergolines, which are known to be dopamine substitutes. The present report deals with the functionalization of 8α-amino-6-methyl-ergoline (2) with a 2-mercaptoacetyl group, and the subsequent synthesis of the first rhenium complex containing a pendent ergoline moiety [Re- O(SSS)(RS)] (HSSSH = HS-CH2CH2-S-CH2CH2-SH and RSH = 8a-amino-N-(2-mercaptoacetyl)-6-methyl-ergoline) (4). The molecular structure of the rhenium complex was determined by X-ray crystal structure analysis.
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  • 186
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 859-862 
    ISSN: 0009-2940
    Keywords: Yttrium ; Lanthanum ; Samarium ; Lanthanides ; Aminotroponiminate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of N-isopropyl-2-(isopropylamino)troponimine, [(i-Pr)2ATI]H, with KH in THF affords [(i-Pr)2ATI]K. This is a useful starting material for the preparation of the mono-, bis- and tris-substituted compounds [[i-Pr)2ATI]YCl2-(THF)2}2, [(i-Pr)2ATI2Y[O(2,6,t-Bu2C6H3)] and [(i-Pr)2-ATI]3Ln (Ln = Y, La, Sm), which can be obtained from ([i-Pr)2ATI]K and LnX3 and LnX3 (X = Cl, I), or Y[O(2,6-t-BuC6H3)]3. All compounds have been characterized by spectroscopic methods. The monosubstituted yttrium complex {[(i-Pr)2ATI]YCl2(THF)2}2 has also been investigated by single crystal X-ray diffraction.
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  • 187
    ISSN: 0009-2940
    Keywords: C-H activation ; Alkyne complexes ; Cyclopentadienyl cobalt ; Fluxionality ; Hydrido complexes ; Clusters ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vicinal C-H bonds of the cycloalkenes CnH2n (n = 5-8) were activated upon treatment under mild conditions with reactive sources of the (C5H5)CO fragment. With [C5H5)CO(C2H4)2] (2a), the trinuclear cluster complexes [H2((C5H5)CO)3(μ3-C2(CH2)n-2)] (5a: n = 5; 5c: n = 5d: n = 8) were formed. Using the more reactive [(C5H5)2Co]/K, 5a-5dwere obtained, along with small amounts of the tetranuclear [{(C5H5)CO}4r{μ4-C2(CH2)n-2}] (8a-c: n = 5-7). X-ray structure analyses of 5c, d and 8b, c were performed. A μ-‖ (orμ3-η1:η2:η1) coordination of the cycloalkyne ligands was found in the trinuclear cluster complexes. The tetranuclear 8b, c had the cycloalkynes quadruply bridging (μ4-η1:η2:η2:η1_ a butterfly arrangement of the metal atoms. The acetylenic carbon-carbon bonds are considerably lengthened upon coordination [1.392(4), 1.398(3) å in 5c d; 1.464(8), 1.499(5) Å in 8b, c]. Three dynamic processes - alkyne “walk” on top of the CO3 triangle, μ2-hydride migration, and μ2/μ3-hydride exchange - are operational in the trinuclear 5a-d. Dynamic NMR data for 5a are consistent with a “windshield-wiper” mechanism for the alkyne migration. Hydride exchange is associated with a higher energy barrier, and is probably and independent dynamic process.
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  • 188
    ISSN: 0009-2940
    Keywords: Mercury ; Lanthanides ; Lanthanoid(II) complexes ; (N-2,6-Diisopropylphenyl)(N-trimethylsily)amide complexes ; Bis(trimethylsilyl)amide complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Mercury(II) amide complex Hg[N(SiMe3)(2,6-iPr2C6H3)]2 (1) was prepared by reaction of HgBr2 with Li[N(SiMe3) 2,6-iPr2C6H3)] in diethyl ether solvent. Redox transmetallation reactions of 1 with elemental samarium, europium or ytterbium in THF solvent (THF = tetrahydrofuran), generated the novel divalent complexes Ln[N(SiMe3)(2,6-iPr2C6H3]2(THF)2 with Ln = Sm (2), Eu (3) and Yb (4). 4 was also synthesized by reaction of elemental ytterbium, HgPh2 and HN(SiMe3)(2,6-Me3)2]2(THF)2 [Ln = Sm (5), Yb (6)] by reaction of the metals with HgPh2 and HN(SiMe3)2. Thermal desolvation of 4 under high vacuum gave Yb(N)(SiMe3)2,6-iPr2C6H3)]2 (THF) (7), whereas under identical conditions 6 yielded the solvent-free complex [Yb[N{SiMe3)2]2]2. (8). The new compounds 1-4 and 7 are hydrocarbon soluble and 171Yb-NMR spectra were recorded for 4, 6, 7 and 8. X-ray crystal structure determinations of 2 and 4 revealed four-coordinate, distorted tetrahedral metal environments augmented by weak Ln…ipso-C(aryl) interactions.
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  • 189
    ISSN: 0009-2940
    Keywords: Biaryls ; Boron ; Chirality ; Cooperative Effects ; Lewis acids ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of Lewis acid binaphthyl systems, substituted in 2-or 2,2′-position, are synthesized by lithiation of 2,2′-dibromo-1,l ′-binaphthyl (5), followed by addition of various electrophiles. Stepwise lithiation and subsequent borylation with trimethyl borate leads to the bromoboronic acid 6, which can be stabilized by esterification with pinacol giving 7. By increasing the reaction mixture to 2 equiv. of n-butyllithium and 2 equiv. of methyl borate the path to the binaphthylmonoboronic acid ester 9 is opened up. A further increase in the quantity of electrophile also leads to the binaphthylbisboronic acid ester 12. The 2,2′-disubstituted silyl, germyl, and stannyl derivatives 13a-15a are accessible in good yields. Treatment with boron halides leads exclusively to methyl/halogen exchange, giving the bidentate Lewis acids 13b-15b, the former of which can be bridged by oxygen.Only in case of the bis(tributylstannyl)binaphthyl 16a does ipso substitution occur in the presence of boron trichloride, giving the bis(dichloroboryl)-substituted binaphthyl 16b which can then be hydrolysed to 11. The structures of the majority of the compounds were investigated by X-ray diffraction. In case of the 2,2′-disubstituted compounds 13a-15a the naphthyl groups are orientated perpendicular to each other. The intra- and intermolecular interactions are dominated by this binaphthyl system. In case of the oxygenbridged compounds 13c and 14c the angle between the naphthyl planes decreases to about 70°. This also has an effect on the packing of the molecule; in this instance the orientation of two naphthyl in neighbouring molecules is nearly parallel. The structure of the diboronic acid is dominated by intra- and intermolecular hydrogen bonding.
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  • 190
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 951-954 
    ISSN: 0009-2940
    Keywords: Phosphane-boranes ; Medium-sized rings ; Ring opening and closure ; Temperature-dependent NMR studies ; Phosphorus ; Boron ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A phosphane-borane (3) with the P-B bond integrated into a seven-membered ring was prepared from 4-pentenyl-diphenylphosphane (4) by hydroboration using 9-borabicyclononane (9-BBN). The product was confirmed to have a ring structure in the solid state by single crystal X-ray diffraction. The P-B distance of 2.057(2) Å is indicative of a standard donor-acceptor bond similar to the type found in homologous five- and six-membered rings. The room-temperature 31P-NMR signal of the compound in various solvents (δ ≈ - 15) is not compatible with the cyclic structure and suggests that ring opening occurs as the compound is dissolved. Variable-temperature NMR work corroborated this assumption, and the enthalpy of ring closure was determined to be ΔH = -30.5(4) kJmol-l. In CD2C12 at -90°C, δ31P is shifted to +3.5 ppm to low field, suggesting virtually complete ring closure under these conditions.
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  • 191
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    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 963-968 
    ISSN: 0009-2940
    Keywords: Fluorine ; Macrocycles ; Complexes ; Sodium ; Barium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new fluoro macrocycles BenzoFN2O3 and F(N2O2)2C2H4 were synthesized in the reactions of 1,3-bis(bromomethyl)-2-fluorobenzene with benzo-diaza-15-crown-5 and 1,2-bis(diaza-12-crown-4)ethane, respectively, in 30% yield each. Close CF...metal ion interactions in the respective alkaline metal complexes in solution are evidenced by characteristic shifts of the 19F-NMR resonances of up to δ = 18.7 relative to the free ligand and by a decrease of the 1J(CF) coupling constant of up to 20 Hz, which is most pronounced in BenzoFN2O3 · Li+ and F(N2O2)2C2H4 · K+. In BenzoFN2O3· Li+ a1J(19F-7Li) of 15.5 Hz was observed, which is indicative very close CF...Li+ interactions in solution. In the X-ray crystal structures of BenzoFN2O3 · Na+ [CF⃛Na+ 246.8(2) pm], 26-fluoro-4,7,13,16-tetraoxa-1, 10-diazatricyclo[ 8.8.7.1 20,24 ] - hexacosa-20,22,24(26)triene · Na+ (CF⃛Na+ 267.1(2) pm) and 21 -fluoro-3,6,9,12,15,18-hexaoxabicyclo[ 18.3.1 1,20]heneicosa- l(24),20,22-triene. Ba2+ [CF⃛Ba2+ 299.0(3) pm] short CF⃛metal interactions were found. Such close CF⃛metal ion interactions do not result in a lengthening of the C-F bonds, which is not a sign of weak CF⃛metal ion interactions, since a Cambridge Structural Database search revealed that a shortening of the C-O bond length is also not observed in crown ether complexes of alkaline metals.
    Additional Material: 3 Ill.
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  • 192
    ISSN: 0009-2940
    Keywords: Phosphorus heterocycles ; 1H-Phosphirenes ; Nucleophilic substitution reactions at 1H-phosphirenes ; Metal-complexation of functionalized 1H-phosphirenes ; Carbonyl complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The halogen atoms in the 1-chloro-1H-phosphirenes, 5a-c, are easily substituted on reaction with organolithium and Grignard reagents, 14a-p, with formation of the corresponding O-, N-, C-, Si-, and Ge-substituted 1H-phosphirenes, 15a-t. C1/H exchange reactions also occur on reaction with lithium metal hydrides (5a → 17). Furthermore, substitution reactions are also realized with the alkali metal borates, 18a-g (→19a-g); the same is true for reactions with trimethylsilyl cyanide and azide (→22a-d). Some of the substitution products have been characterized in the form of their metal complexes, 16, 23, 24, and 25.
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  • 193
    ISSN: 0009-2940
    Keywords: Germatranes ; Organotrihalogenogermanes ; Organometallic (Si, Ge, Sn) reagents ; Transmetallation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trialkylstannyl esters of tris(2-hydroxyalkyl)amines, N(CH2CHROSnAlk3)3 (9-11 (R = H, Me; Alk = Et, Bu), react with X3GeC(R1)(R2)COOR3 (12-17) (X = Cl or Br; R1, R2=H, Me, Ph, SiMe3, COOEt; R3=Me, Et) to give esters of α-germatranylcarboxylic acids, N(CH2CHRO)3GeC(R1)(R2)-COOR3 (1-8), in high yields. The synthesis of esters 12-17 is reported. Esters of α-germatranyldiphenylacetic acid 24 and 25 can be obtained by treatment of diphenylketene with Et3SnOMe to give in situ Et3SnC(Ph2)COOMe (23), followed by reaction with GeCl4 to give in situ Cl3GeC(Ph2)COOMe (22 and further reactions with 9 or 11, respectively. Reduction of germatrane 6 with LiAlH4 in diethyl ether leads to cleavage of the germanium-carbon bond with subsequent formation of (2-hydroxyethyl)trimethylsilane. The crystal structures of 3, 6 and 7 are reported. 1-Acyloxygermatranes 26 and 27 are obtained by treatment of 1-methoxygermatrane (28) with diphenyl- and dichloroacetic acid, respectively.
    Additional Material: 4 Ill.
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  • 194
    ISSN: 0009-2940
    Keywords: Tin - Nitrogen cage compounds ; Sn—X—Sn intramolecular bridges ; Distannylamine pyridine adduct ; Tin ; Moessbauer spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(dimethylchlorostannyl)amine (2a) reacts with pyridine in a 3:4 molar ratio to produce the tin-nitrogen containing bicyclo[3.1.1]heptane (3) with elimination of the adduct Me2SnCl2·2 py. Treatment of the distannylamine 2,6-[Pr2H3N(SnMe2Cl)2 (4) with pyridine, however, leads to the formation of the 1:1 pyridine adduct 4 and this can be regarded as a model to explain the route to 3. The molecular structures of 3 and 5 were determined by multinuclear magnetic resonance spectroscopy in solution, as well as by X-ray structure analysis of their crystals. Typical structural features for both compounds are intramolecular Sn—X—Sn bridges. Support for the structures comes from MS fragmentation patterns, IR spectra, and the Mössbauer spectra.
    Additional Material: 2 Ill.
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  • 195
    ISSN: 0009-2940
    Keywords: 1,2,4-Diazaphospholes ; Phosphiranes, alkylidene- ; 2-Phosphabutadienes ; Phosphorus heterocycles ; pyrazolines, thermolysis ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 5-alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-phosphapyrazolines) are thermally much more stable than related compounds without the exocyclic double bond. Thermolysis reactions typically occur in the range 110-150°C in toluene solution, and different, mostly competing, reaction pathways are observed. Thermal extrusion of nitrogen from 8a-g gives rise to β-phosphanaylsiloxyalkenes 10, benzo[c]-phosphole derivatives 11, 14 and 115, (β-siloxyalkylidene)-Phosphiranes 12, and dihydro-1,3-oxaphospholes 13. The thermolysis of 5-alkylidene-4,5-dihydro-4-trimethylsilyl-3-trimethylsilyloxy-3H-1,2,4-dizaphospholes 17 afforded three products, including the highly substituted and stable 2-phosphabutadienes 18 formed by nitrogen extrusion and rearrangement. Finally, the 4-chloro-3-trimethylsilyloxy-substituted heterocycle 21 was transformed at 170°C into 4H-1,2,4-diazaphosphole 23. The structures of 13c and 18a were determined by single-crystal X-ray diffraction.
    Additional Material: 2 Ill.
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  • 196
    ISSN: 0009-2940
    Keywords: Boron ; Diazaboroles ; Carbenes ; Heterocycles ; Imidazoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Bromo-2,3-dihydro-1H-1,3,2-diazaboroles (3a-c) were synthesized by cyclocondensation of dilithiated 1,4-diazabutadienes (5a-c) with boron tribromide in hexane. 3a was also obtained by sodium amalgam reduction was conducted in ether solvents, diboroxane (2) resulted as the main product. Compound 3a and 1,3-dialkyl-4,5-dimethylimidazol2-ylidenes (6a, b) underwent halide displacement to afford the borolylimidazolium salts 7a, b. Compounds 2, 3a-c, and 7a, b were characterized by elemental analyses and spectroscopic methods (1H, 11B, 13C NMR; Ir; MS). The molecular structures of 2 and 7a were established by single-crystal X-ray diffraction analyses.
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  • 197
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 725-728 
    ISSN: 0009-2940
    Keywords: Dendrimers ; Metal complexes ; Nanostructures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Strong multiple complexation of transition metal ions, Cu(II), Zn(II) and Ni(II) with different generations of well-defined poly(propylene imine) dendrimers as multi(tridentate) ligands has been used to construct nanoscopic assemblies of defined structure and size incorporating a distinct number of metal ions from 2 up to 32.
    Additional Material: 5 Ill.
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  • 198
    ISSN: 0009-2940
    Keywords: Germanium ; Digermenes ; Tin ; Germylenes ; Stannylenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of GeCl2 · dioxane with the Grignard reagent RMgBr (R=2-tBu-4,5,6-Me3C6H) furnishes the tetraaryldigermene R2Ge=GeR2 (8). X-ray structure-analysis of 8 reveals a short Ge=Ge double bond, a nearly planar environment of both germanium atoms and extremely widened C—Ge—C angles of 128°. In solution, 8 dissociates into two germylene molecules R2Ge, which can be trapped with oxygen or by [4+1] cycloaddition reactions with 1,4-dihetero-1,3-dienes. A similar cycloadduct of a stannylene wa obtained by thermolysis of (R′2Sn)3 (R′=2,4,6-iPr3C6H2), in the presence of a 1,4-diazabutadiene and characterized by an X-ray structure-analysis.
    Additional Material: 2 Ill.
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  • 199
    ISSN: 0009-2940
    Keywords: Silicenium ion ; Iminosilane ; Aluminate ; Silicon ; Aluminium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithiated text-butylaminolfluorosilanes react with aluminum trichloride in ether, eliminating LiF to give AlCl3 adducts of iminosilanes  -  aminosiliceniotrichloroaluminates {R2Si-NCMe3·AlCl3}, which thermally form the dimethylazomethine- aluminium trichloride, Me2C=NH·AlCl3.
    Additional Material: 2 Ill.
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  • 200
    ISSN: 0009-2940
    Keywords: Titanocene complexes ; S ligands ; Organic polysulfanes ; Ligand transfer reactions ; Sulfur heterocycles ; Chalcogens ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of Cp2Ti(CO)2 (3) with the di- and polysulfanes 1,2,4-(CH2)2S3, C4S6 (9), C,7H10S3 (11), 1,2,4,6-(CH2)3S4 (16), C6H10S6(19), and S6 affords the titanocene chelate complexes Cp2TiS3(CH2)2 (8), (Cp2Ti)2C4S6 (10), Cp2TiS3C7H10 (13), Cp2TiS2C7H10 (14), Cp2TiS4(CH2)3 (17), Cp,2TiS6C6H6H10 (20), and Cp2TiS8 (23). 14 is also obtained from Cp2TiCl2 (1) and the geminal dithiol of norbornene. The analogous reaction with the dithiol of dicyclopentadiene yields Cp2TiS2C10H12 (15). In ligand transfer reactions, 8 reacts with SCl2 to give 1,2,3,5-tetrathiane (25), 10 provides 9 on reaction with Cl2, 13 when treated with S2Cl2 affords C7H10S5 (12), 15 reacts with S2Cl2Cl2 to give C10H12S4. 17 and SCl2 yield 1,2,3,5,7-pentathiepane (18), 20 is converted to C6H10S7 (22) on reaction with SCl2, and 23 yields S10 and 1,2,-C6H4(SCl)2, respectively. With phosgene, thiophosgene, and thionyl chloride, compound 15 yields the corresponding dithiocarbonate 26, the trithiocarbonate 27 and the trisulfane 2-oxide 28. The structure of 27 was determined by X-ray crystallography.
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