351203-69-5Relevant academic research and scientific papers
Rhodium complexes of a chelating bisphosphoniobenzophospholide cation
Haep, Stefan,Nieger, Martin,Gudat, Dietrich,Betke-Hornfeck, Michael,Schramm, Daniel
, p. 2679 - 2685 (2008/10/08)
The 1-(diphenyl(2-diphenylphosphinoethyl)phosphonio)-3-triphenylphosphoniobenzo[c]ph ospholide cation 1 reacts with [RhCl(C2H4)2]2 to form a dinuclear chelate complex, [RhCl(κ2-P(?2), P′(?)-1)]2 (5). Treatment of 5 with PPh3 affords mononuclear [RhCl(PPh3)(κ2- P(?2),P′(?3)-1)] (8), whereas reaction with 1,5-cyclooctadiene proceeds via cleavage of the Cl bridges to give [RhCl(cod)(κ-P(?3)-1)] (6). The chelating binding mode of 1 can be reconstituted by abstraction of chloride with TlOTf to give the dicationic complex [Rh(cod)(κ2-P(?2),P′(?3 )-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 structural parameters and metal NMR data confirm the different electronic properties of the two types of phosphorus centers in 1 and support in particular the assumption of distinct ?-acceptor character for the ?2-P atom, which should render the complexes potentially interesting precatalysts for hydroformylation. In accord with this hypothesis, complexes 5[BPh4]2 and 7[BPh4]2 display good activities and chemoselectivities as catalysts for the hydroformylation of 1-hexene at room temperature, even though the regioselectivities for n-aldehydes are low.
