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Preparative, structural, and electrochemical investigations on peralkylated niobocene dichlorides and difluorides
Brunner, Henri, Gehart, G., Meier, Walter, Wachter, Joachim, Riedel, Astrid, Elkrami, S., Mugnier, Y. und Nuber, B. (1994) Preparative, structural, and electrochemical investigations on peralkylated niobocene dichlorides and difluorides. Organometallics 13 (1), S. 134-140.Veröffentlichungsdatum dieses Volltextes: 03 Jan 2012 08:34
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DOI zum Zitieren dieses Dokuments: 10.5283/epub.23017
Zusammenfassung
CP(dagger)2NbCl2 (CP(dagger) = 175-C5Me4Et) (1b) was synthesized from NbCl5 and a slight excess of Cp(dagger)Li and NaBH4. Its electrochemical (2 e-, E1/2 = -1.6 V) and chemical reduction (2 equiv of Na/Hg) was studied showing that peralkylation of the Cp ligand facilitates two-electron reduction compared to less substituted CP2NbHal2 derivatives. The reduced solutions of CP*2NbCl2 (CP* = C5Me5) ...
CP(dagger)2NbCl2 (CP(dagger) = 175-C5Me4Et) (1b) was synthesized from NbCl5 and a slight excess of Cp(dagger)Li and NaBH4. Its electrochemical (2 e-, E1/2 = -1.6 V) and chemical reduction (2 equiv of Na/Hg) was studied showing that peralkylation of the Cp ligand facilitates two-electron reduction compared to less substituted CP2NbHal2 derivatives. The reduced solutions of CP*2NbCl2 (CP* = C5Me5) (1a) and of lb were shown by means of EPR spectroscopy to contain two new paramagnetic species 1A,B for which bent niobocene (A(Nb) = 100 G) and fulvene-like structures (A(Nb) = 55 G) are proposed. The high reduction potential of these species led in their reaction with HPF6 to the first stable difluoroniobocene derivative, [CP(dagger)2NbF2]PF6 (2), in good yield. The molecular structures of 2 and a cocrystallizate of 2 and [CP(dagger)2NbCl2]PF6 (3), analyzing as [CP(dagger)2NbCl(Cl,F)]PF6 (4), were studied by X-ray diffraction techniques. Comparison with the structure of 1b shows a marked decrease of the angle Hal-Nb-Hal from 102.3(4)-degrees (2) to 85.2(1)-degrees (1b). Electrochemical 1 e- reduction of 2 gave rise to the formation of CP(dagger)2NbF2, which exhibits a much lower potential (E1/2 = -2.38 V) than other niobocene dihalides. Reaction of 2 with Li2S2 gave CP(dagger)2Nb(eta-S2)F, whereas 3 was reduced by Li2S2 to give 1b.
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| Dokumentenart | Artikel | ||||
| Titel eines Journals oder einer Zeitschrift | Organometallics | ||||
| Verlag: | American Chemical Society | ||||
|---|---|---|---|---|---|
| Band: | 13 | ||||
| Nummer des Zeitschriftenheftes oder des Kapitels: | 1 | ||||
| Seitenbereich: | S. 134-140 | ||||
| Datum | 1994 | ||||
| Institutionen | Chemie und Pharmazie > Institut für Anorganische Chemie > Entpflichtete oder im Ruhestand befindliche Professoren > Arbeitskreis Dr. Joachim Wachter | ||||
| Identifikationsnummer |
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| Dewey-Dezimal-Klassifikation | 500 Naturwissenschaften und Mathematik > 540 Chemie | ||||
| Status | Veröffentlicht | ||||
| Begutachtet | Unbekannt / Keine Angabe | ||||
| An der Universität Regensburg entstanden | Unbekannt / Keine Angabe | ||||
| URN der UB Regensburg | urn:nbn:de:bvb:355-epub-230179 | ||||
| Dokumenten-ID | 23017 |
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