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|Type:||Artigo de periódico|
|Title:||Structural And Electronic Effects In (benzylideneacetone)dicarbonyl(phosphine)iron(0) And (benzylideneacetone)dicarbonyl(phosphite)iron(0) Complexes. A Carbon-13 Magnetic Resonance Study|
|Abstract:||The structures in solution and the electronic effects induced by the ligands L in the series (benzylideneacetone) Fe(CO)2L (L = CO, tertiary phosphines, and tertiary phosphites) were studied by 13C NMR spectroscopy. In contrast to the tricarbonyl derivative, which is fluxional at 32°C, the compounds containing a phosphorus ligand do not show fluxional behavior at this temperature. This could be attributed to an increase in the π back-donation from the filled metal d orbitals to the LUMO of benzylideneacetone (BDA) induced by the better σ-donor and poorer π-acceptor phosphorus ligands, compared to CO. The resonances of coordinated BDA show a very large upfield shift at the carbons directly involved in bonding with iron. The differences in the chemical shifts at the terminal carbon of the heterodiene function in coordinated and free BDA, AC4, correlate reasonably well with the basicities of the phosphorus ligands while the ratio ΔC4/ΔC3 correlates with the Tolman electronic parameter, v, of the phosphorus ligands. The results are interpreted on the basis of a bonding model in which the coordinated BDA acts as a "sink" for the negative charge placed in the iron atom by the phosphorus ligand via a P →σ Fe →α BDA mechanism. © 1985 American Chemical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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