Article: Metallkomplexe von Heteroarenen, VII: Bis(2,3,5,6-tetramethyl-η6-pyrazin)vanadium, der erste Bis(aren)metall-Komplex mit vier N-Atomen in der Koordinationssphäre / Metal Complexes of Heteroarenes, VII: Bis(2,3,5,6-tetramethyl-η6-pyrazine)vanadium, the First Bis(arene)metal Complex with Four N Atoms in the Coordination Sphere
Zeitschrift für Naturforschung. 2014 June 2, v. 48, no. 11
2014
Abstract: Cocondensation of 2,3,5,6-tetramethyl-pyrazine with vanadium atoms affords [2,3,5,6-(CH₃)₄-η⁶-1,4-C4N₂]₂V (6) which has been studied by X-ray crystallography, EPR-spectro-scopy and cyclic voltammetry. As shown by unequal metal ring-atom distances (V—C = ... ...
| Abstract | Cocondensation of 2,3,5,6-tetramethyl-pyrazine with vanadium atoms affords [2,3,5,6-(CH₃)₄-η⁶-1,4-C4N₂]₂V (6) which has been studied by X-ray crystallography, EPR-spectro-scopy and cyclic voltammetry. As shown by unequal metal ring-atom distances (V—C = 219.6, V—N = 210.9 pm) the ligand in 6 is folded along the N—N axis (dihedral angle 13.6°). The conformation adopted by the cyclic ligands in the crystal has a torsional angle of 44.2° which comes close to the angle of 45° expected for maximum back-bonding, the filled vanadium orbitals 3 dₓ₂₋ᵧ₂and 3 dₓy interacting separately with unoccupied b₃ᵤ(π*) orbitals of the individual pyrazine rings. The hyperfine coupling constant a(⁵¹V) = 4.45 mT attests to comparatively small spin density at the metal nucleus. It is proposed, that substantial transfer of spin density is effected by V 3dz²→ag(σⁿ⁺) overlap, the latter function representing the in-phase combination of the nitrogen “lone pair” orbitals. Contrary to bis(η⁶-phosphinine)vanadium 8, for the pyrazine complex 6 only the anion 6⁻ is formed reversibly in cyclovoltammetry, oxidation to 6⁺ being irreversible. However, in common with 8, the redox potentials for 6 show pronounced anodic shifts. Attempts towards η⁶-coordination of 2,4,6-trimethyl-1,3,5-triazine failed. Apparently, the 1:1 ratio of CH₃/N is insufficient to furnish the triazine ring with the appropriate combination of π-donor and δ-acceptor properties essential for synergetic bond formation. |
|---|---|
| Keywords | X-ray diffraction ; aromatic hydrocarbons ; ligands ; nitrogen ; oxidation ; pyrazines ; redox potential ; triazines ; vanadium |
| Language | English |
| Dates of publication | 2014-0602 |
| Size | p. 1581-1588. |
| Publishing place | Verlag der Zeitschrift für Naturforschung |
| Document type | Article |
| ZDB-ID | 124635-5 |
| ISSN | 0340-5087 ; 0044-3174 ; 0932-0776 ; 0341-0447 ; 0341-0420 |
| ISSN | 0340-5087 ; 0044-3174 ; 0932-0776 ; 0341-0447 ; 0341-0420 |
| DOI | 10.1515/znb-1993-1117 |
| Database | NAL-Catalogue (AGRICOLA) |
More links
Kategorien
In stock of ZB MED Bonn / Germany
| Z 4' 47/11 b: Show issues | ||||
| Z 9.8: Show issues |
Order via subito
This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.
Inter-library loan at ZB MED
Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.