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Brunner, Henri ; Gehart, G. ; Meier, Walter ; Wachter, Joachim ; Riedel, Astrid ; Elkrami, S. ; Mugnier, Y. ; Nuber, B.

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
Artikel
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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Details

DokumentenartArtikel
Titel eines Journals oder einer ZeitschriftOrganometallics
Verlag:American Chemical Society
Band:13
Nummer des Zeitschriftenheftes oder des Kapitels:1
Seitenbereich:S. 134-140
Datum1994
InstitutionenChemie und Pharmazie > Institut für Anorganische Chemie > Entpflichtete oder im Ruhestand befindliche Professoren > Arbeitskreis Dr. Joachim Wachter
Identifikationsnummer
WertTyp
10.1021/om00013a023DOI
Dewey-Dezimal-Klassifikation500 Naturwissenschaften und Mathematik > 540 Chemie
StatusVeröffentlicht
BegutachtetUnbekannt / Keine Angabe
An der Universität Regensburg entstandenUnbekannt / Keine Angabe
URN der UB Regensburgurn:nbn:de:bvb:355-epub-230179
Dokumenten-ID23017

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