| Abstract
| - Rhodium complexes containing the cationic 1-(diphenyl(2-diphenylphosphinoethyl)phosphonio)-3-triphenylphosphoniobenzo[c]phospholide as monodentate (κ1-P) or chelating bidentate (κ2-P,P‘) ligands were prepared and characterized by spectroscopic techniques and in one case by X-ray diffraction. Some of the prepared chelate complexes were shown to be active as precatalysts which allow the hydroformylation of 1-hexene at room temperature.
- The 1-(diphenyl(2-diphenylphosphinoethyl)phosphonio)-3-triphenylphosphoniobenzo[c]phospholide cation 1 reacts with [RhCl(C2H4)2]2 to form a dinuclear chelate complex, [RhCl(κ2-P(σ2),P‘(σ3)-1)]2 (5). Treatment of 5 with PPh3 affords mononuclear [RhCl(PPh3)(κ2-P(σ2),P‘(σ3)-1)] (8), whereas reaction with 1,5-cyclooctadiene proceeds via cleavage of the Clbridges to give [RhCl(cod)(κ-P(σ3)-1)] (6). The chelating binding mode of 1 can be reconstitutedby abstraction of chloride with TlOTf to give the dicationic complex [Rh(cod)(κ2-P(σ2),P‘(σ3)-1)]2+ (7). All complexes have been characterized by 1H, 31P, and 103Rh NMR spectroscopy,and 5[BPh4]2 was characterized as well by single-crystal X-ray diffraction. The structuralparameters and metal NMR data confirm the different electronic properties of the two typesof phosphorus centers in 1 and support in particular the assumption of distinct π-acceptorcharacter for the σ2-P atom, which should render the complexes potentially interestingprecatalysts for hydroformylation. In accord with this hypothesis, complexes 5[BPh4]2 and7[BPh4]2 display good activities and chemoselectivies as catalysts for the hydroformylationof 1-hexene at room temperature, even though the regioselectivities for n-aldehydes are low.
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