| Abstract
| - PePyn ligands coordinate to rhodium (I) centers acting as bidentate and tridentate P,N-chelating and also as P,N-bridging ligands (PePyn = P(CH2CH2Py)nPh3-n; Py = 2-pyridyl; n = 1, 2). The P−N−Rh cycles are nonplanar. The conformational changes of the metallacycles are faster than the equilibria between different isomers.
- Several rhodium(I) complexes of the type [RhX(CO)(PePy2)], [Rh(diene)(PePy)]+, and [Rh(diene)(PePy2)]+ (PePyn= P(CH2CH2Py)nPh3-n; Py = 2-pyridyl; n = 1, 2) have been prepared. The two former are square planar; thelatter are pentacoordinated for diene = tetrafluorobenzobarrelene or norbornadiene (confirmed by X-ray diffraction),but an equilibrium of 4- and 5-coordinate isomers exists in solution for diene = 1,5-cyclooctadiene. The fluxionalbehavior of all these complexes is studied by NMR spectroscopy. The complex [Rh(NBD)(PePy2)]PF6·Cl2CH2crystallizes in the monoclinic space group P21/n with a = 8.455(1) Å, b = 18.068(3) Å, c = 19.729(3) Å, β =99.658(3)°, and Z = 4. The complexes [Rh(diene)(PePy2)]+ react with CO to give the dimeric complex[Rh2(CO)2{P(CH2CH2Py)2Ph}2](BF4)2 with the pyridylphosphine acting as P,N-chelating and P,N-bridging.
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