The Azide Homologues EtPPP and PhAsAsAs as Bifacially Coordinated Ligands in Tripod-Cobalt Complexes: Synthesis, Structure and Molecular Dynamics
✍ Scribed by Dipl.-Chem. Annette Barth; Prof. Dr. Gottfried Huttner; Dipl.-Chem. Martin Fritz; Dr. Laszlo Zsolnai
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 387 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0044-8249
No coin nor oath required. For personal study only.
✦ Synopsis
Aryl
a
6 b
[111 Thus, the fact that all NMR signals appear only singly in 5. despite the unsymmetrical structure, cannot be explained in terms of a rapid rmgopening 5 + 4 and renewed conrotatory ring closure. The mechanism required from the Because of the trans arrangement of the sterically very demanding aryl residues, rac-4b can rotate more easily into the s-cis conformation, i.e. rac-4 b cyclizes quantitatively to 6 a under the reaction conditions. In meso-4 a, s-cis geometry is sterically more strongly hindered because of the cis-arrangement of the aryl residues. Hence, the isolable, colorless coupling product 4 ought to be s-trans-meso-4a, which-due to the stability of the substituents at the phosphorus atoms toward inversion4onverts only slowly and exclusively into 5 in solution (e.g. in CHCI,). A slow electrocyclic ring opening of 5 to give the open-chain hexatetraene 4 is observed at 120 "C, whereas 6a remains unchanged upon heating to 150 "C.