BRUNNER, H and GEHART, G and MEIER, W and WACHTER, J and RIEDEL, A and ELKRAMI, S and MUGNIER, Y and NUBER, B (1994) PREPARATIVE, STRUCTURAL, AND ELECTROCHEMICAL INVESTIGATIONS ON PERALKYLATED NIOBOCENE DICHLORIDES AND DIFLUORIDES. ORGANOMETALLICS, 13 (1). pp. 134-140. ISSN 0276-7333,
Full text not available from this repository.Abstract
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.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CRYSTAL-STRUCTURE; CARBON-DIOXIDE; COMPLEXES; REDUCTION; CHEMISTRY; NIOBIUM; DERIVATIVES; TITANOCENE; NITROGEN; |
| Depositing User: | Dr. Gernot Deinzer |
| Last Modified: | 19 Oct 2022 08:41 |
| URI: | https://pred.uni-regensburg.de/id/eprint/53585 |
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