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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 305-310 
    ISSN: 1434-1948
    Keywords: Ab initio calculations ; Carbene homologues ; Boron ; Isoelectronic analogues ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: While Arduengo-type carbenes are now well established for the Group IVa elements carbon, silicon and germanium, they are experimentally unknown for the isoelectronic anions with the Group IIIa elements boron, aluminum, gallium, and indium. In the present quantum chemical investigations, the bonding features of this class of compounds are explored. As a result, they are predicted to be stable species with sizeable singlet-triplet energy separations and electron affinities. Hence, they may be considered as valid targets for experimental investigations. An analysis of the electron density distribution in the case of boron and aluminum reveals a strongly polar B-N bond for the former, and a half Al-N bond with positive charge at the aluminum, emphasizing the donor-acceptor formulation for the latter.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-1948
    Keywords: Ab initio calculations ; Chelates ; Donor-acceptor systems ; P ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mono- and bidentate chelation of the main-group elements silicon, germanium, tin, and lead through the phosphorus atoms of the diphosphanylmethanide ligand has been studied by means of quantum chemical methods. In accord with experimental investigations, the species are found to adopt a ψ-tbp conformation of high flexibility. The various distortional modes causing the axial and equatorial positions to become equivalent have also been investigated. In addition, the bonding situations in the electronically related bis(diamino)- and the higher element homologue bis(diarsanyl)methanide ligand systems have been studied. The bonding situation in the hitherto experimentally unknown bis(diamino)methanide ligands is predicted to be similar to that in bis(amidinate) complexes. An analysis of the electron distributions (natural bond orbital population analysis) in these compounds reveals that the central main-group element is positively charged and weakly chelated by the surrounding ligands.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 33 (1999), S. 177-185 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemical concepts are important to gain a qualitative understanding of chemistry. They are needed to find interesting questions to which experimental research as well as quantum-chemical investigations and computer simulations can contribute. We point out why chemical concepts should be seen as an important and from fundamental physical theories to a certain degree independent part of chemistry. An overview and analysis of some concepts - which are often introduced only in connection with special examples instead of a discussion for their own sake - are given. We take a closer look at some concepts to illustrate our assertions. An analysis of the stability of the cyclic (MoNL3)-trimer demonstrates how these concepts work and what they can tell us about this special case.
    Notes: Wir haben versucht, deutlich zu machen, wie wichtig theoretische Konzepte in der Chemie sind. Dabei gelangen wir zu folgenden Schlußfolgerungen über die Konzepte, die in der Chemie herangezogen werden, um Beobachtungen zu deuten und zu verstehen: Qualitativ chemische Konzepte sind für ein Verständnis der Chemie unverzichtbar. Eine quantenchemische Berechnung liefert nicht automatisch Verständnis und Einordnung in einen Gesamtzusammenhang.Erst die vereinfachende Beschreibung chemischer Konzepte ermöglicht eine unmittelbare Diskussion chemischer Fragestellungen.Die Konzepte sind trotz grundlegender physikalischer Theorien bis zu einem gewissen Grade eigenständig.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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