- Rhodium(I)-assisted stereoselective coupling of an alkyl, aryl or vinyl group with a vinylidene ligand: A novel synthetic route to π-allyl and π-butadienyl rhodium complexes
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In the first part of this work, a general method for the preparation of aryl, methyl, vinyl and alkynyl(vinylidene)rhodium(1) complexes trans-[Rh(R')-(=C=CHR)(PiPr3)2] (8-14, 18-22) and trans-[Rh(R')(=C=CMe2)(PiPr3)2] (16, 17) from the corresponding chloro(vinylidene) derivatives and Grignard reagents is described Whilst compounds 8 and 10-13 react with pyridine to give trans-[Rh(C≡CR)(py)(PiPr3)2] (23-25) by elimination of R'H, treatment of 8-11, 16, and 18 with carbon monoxide yields the square-planar η1-vinyl and η1-butadienylrhodiumcarbonyl complexes trans-[Rh{η1-(Z)-C(R')=CHR}(CO)(PiPr3)2] (27-32). The reaction of 8 or 18 with methyl or tert-butylisocyanide leads stereoselectively to the isocyaniderhodium(I) compounds trans-[Rh{η1-(Z)C(R)=CHPh}(CNR')(PiP3)2] (33-35). Acid-induced cleavage of the rhodium carbon σ bond of 27, 30, or 31 with CH3CO2H gives trans-[Rh(η1-O2CCH3)-(CO)(PiPr3)2] (38) and the corresponding olefin or diene, respectively. In the absence of a Lewis base such as pyridine, CO, or CNR', compounds 18-20 rearrange in benzene at 40-50°C to afford the isomeric π-allyl complexes [Rh(η3-1-RC3H4)(PiPr3)2] (40-42) almost quantitatively. The vinyl(vinylidene) compounds 11 and 12 also undergo an intramolecular rearrangement that leads to the η3-2,3,4-butadienyl- or to the alkynyl(ethene)rhodium(I) isomers, depending on the reaction conditions. In an analogous manner to the η1-vinyl- and η1-butadienyl(carbonyl) derivatives 27, 30, and 31, the π-allyl and π-butadienyl complexes also react with acetic acid to give [Rh(η2-O2CCH3)(PiPr3)2] (47) and the respective olefin.
- Werner, Helmut,Wiedemann, Ralf,Steinert, Paul,Wolf, Justin
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- C-C-Verknuepfungsreaktionen als neue Syntheseroute fuer ?-Allyl- und ?-Butadienylrhodium-Komplexe
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Stichworte: Allylkomplexe * Isomerisierungen * Kohlenstoff-Kohlenstoff-Verknuepfungen * Vinylidenkomplexe
- Wiedemann, Ralf,Wolf, Justin,Werner, Helmut
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p. 1359 - 1361
(2007/10/02)
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