Metal-π-Komplexe von Benzolderivaten
| Autor: | Heike Mellinghoff, Werner Massa, Gerhard Baum, Jörg Schneider, Christoph Elschenbroich |
|---|---|
| Rok vydání: | 1988 |
| Předmět: |
chemistry.chemical_classification
Double bond Ligand Stereochemistry Organic Chemistry Crystal structure Biphenylene Ring (chemistry) Biochemistry Inorganic Chemistry chemistry.chemical_compound Crystallography chemistry Sandwich compound Materials Chemistry Proton NMR Molecule Physical and Theoretical Chemistry |
| Zdroj: | Journal of Organometallic Chemistry. 355:163-176 |
| ISSN: | 0022-328X |
| Popis: | The novel arene transition-metal complexes bis(η 6 -biphenylene)chromium ( 3 ) and (η 6 -biphenylene)(η 6 -benzene)chromium ( 4 ) are accessible via metal-atom ligand-vapor cocondensation. In contrast to sandwich complexes of naphthalene and of anthracene, the complexes of biphenylene are inert to substitution. As determined by X-ray diffraction, the ligands in crystalline 3 adopt the syn -conformation. Solid 3 is disordered in such a way that the two bis (η 6 -arene) coordination sites between eclipsed pairs of biphenylene ligands are occupied statistically by chromium atoms. The degree of double bond fixation in biphenylene is reduced upon η 6 -coordination. 1 H NMR coordination shifts Δδ( 1 H) were determined for 3 and 4 . Coordination-induced quenching of an alleged paratropic ring current in the central four-membered ring of biphenylene as a source for the coordination shift is deemed insignificant. In the ESR spectra of the radical cations 3 + and 3 + , differences of the proton hyperfine coupling constants for symmetry-inequivalent protons are resolved which is unusual for (η 6 -arene) 2 M( d 5 ) species. This finding is rationalized in terms of the particularly large difference in spin density at the 1- and 2-positions in the ligand radical anion 1 − . |
| Databáze: | OpenAIRE |
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