Metall-π-Komplexe von benzolderivaten XXXVIX. Di[1,4-bis(diphenylphosphano)-η6 benzol]chrom: Ein baustein für polynukleare bimetallkomplexe?
| Autor: | Heikenfeld, Jochen Sebbach, Bernhard Metz, Christoph Elschenbroich, Gottfried |
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| Rok vydání: | 1992 |
| Předmět: |
Ligand
Stereochemistry Organic Chemistry chemistry.chemical_element Bridging ligand Biochemistry Redox law.invention Inorganic Chemistry Crystallography Chromium chemistry.chemical_compound chemistry Sandwich compound law Materials Chemistry Nucleophilic substitution Physical and Theoretical Chemistry Electron paramagnetic resonance Bifunctional |
| Zdroj: | Journal of Organometallic Chemistry. 426:173-185 |
| ISSN: | 0022-328X |
| Popis: | Nucleophilic substitution at bis(1,4-dichloro-η6-benzene)chromium by means of lithiumdiphenylphosphide affords di[1,4-bis(diphenylphosphano)η6-benzene]chromium (5). Two para-positioned organometallic diphos units and a central metal atom featuring variable charge and magnetism, render the complex 5 a versatile potential bridging ligand in oligomeric materials. Here the bifunctional chelating nature of 5 is exploited for the synthesis of the hetera-metallocyclophane [2,2,11,11-tetracarbony-1,1,3,3,10,10,12,12-octaphenyl-2,11-dinickela(0)-1,3,10,12-tetraphospha- η12-[3.3]paracyclophane]chromium (6). According to 1H, 13C, and 31P NMR spectroscopic evidence the bridges -PPh2-Ni(CO)2-PPh2- in 6 in the range − 80 Cyclic voltammetry uncovers a rich redox chemistry for the trinuclear complex 6 which, however, is reversible only for the first oxidation step 6+/0. The anodic peak potentials which follow this first, chromium-centered, oxidation are assigned to the couples Ni+/0, Cr2+/1, and Ni2+/1+. The reduction 60/− occurs quasi reversibly; the relative ease, with which the stage 6 − is reached, points to electron delocalization over both Ni(CO)2 units. The radical cations 1+, 2+, 5 + and 6+ are also accessible through chemical oxidation, they are subjected to EPR spectroscopic study. The hyperfine interaction a(31P), observed for 2+ and 5+ testifies to spin delocalization into the ligand periphery. |
| Databáze: | OpenAIRE |
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