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http://dx.doi.org/10.18419/opus-7959
Autor(en): | Gudat, Dietrich Schiffner, Hans M. Nieger, Martin Stalke, Dietmar Blake, Alexander J. Grondey, Hiltrud Niecke, Edgar |
Titel: | Coordination isomerism in pentamethylcyclopentadienyl-substituted iminophosphanes: from classical structures to a π-complexed iminophosphenium ion |
Erscheinungsdatum: | 1992 |
Dokumentart: | Zeitschriftenartikel |
Erschienen in: | Journal of the American Chemical Society 114 (1992), S. 8857-8862. URL http://dx.doi.org./10.1021/ja00049a018 |
URI: | http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-74338 http://elib.uni-stuttgart.de/handle/11682/7976 http://dx.doi.org/10.18419/opus-7959 |
Zusammenfassung: | Novel iminophosphanes of the type (Me5C5)P=NR [R = C6H2tBu3 (5a), Si-i-Pr3 (5b), SiMe3 (5c)] are prepared via either thermolytic or base-promoted elimination reactions and characterized by analytical and spectroscopic methods. The x-ray crystal structures of 5a,b establish the presence of coordination isomerism of the cyclopentadienyl ring, which at the same time strongly alters the characteristics of the P-N multiple bond. For 5a, η1-attachment of the Me5C5 moiety to the phosphorus and a localized phosphorus-carbon σ-bond are found, and the P-N double bond compares to that of alkylated iminophosphanes (rPN = 155.1 (8) pm). 5b exhibits η2-coordination of the cyclopentadienyl ring leading to increased P-N triple-bond character, as evidenced by shortening of the P-N distance (153.3 (3) pm) and the remarkable opening of the nitrogen valence angle (153.3 (2)°). The structure is discussed as an intramolecular π-complex between a formal cyclopentadienyl anion and an iminophosphenium cation. The 1H and 13C NMR spectra show that rapid elementotropic rearrangements around the five-membered ring take place both in solution and in the solid state. The unique temperature dependence of δ31P in solution together with the considerable differences in δ 31P between the solution and solid states are interpreted in a model assuming a "haptotropic" mechanism for the fluxionality involving dynamic η1/η2-coordination isomerizations in solution. As expected, nucleophilic displacement of the Me5C5 moiety takes place in the reaction of 5b,c with LiC6H2tBu3, yielding the iminophosphanes tBu3H2C6P=NR (R = Si-i-Pr3 (8b), SiMe3 (c)) as products. |
Enthalten in den Sammlungen: | 15 Fakultätsübergreifend / Sonstige Einrichtung |
Dateien zu dieser Ressource:
Datei | Beschreibung | Größe | Format | |
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gud6.pdf | 1,62 MB | Adobe PDF | Öffnen/Anzeigen |
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