Rhodium complexes with the chelating and binucleating ligands P(CH2CH2Py)(n)Ph3-n (Py=2-pyridyl; n=1, 2): Structures and fluxional behavior

Several rhodium(I) complexes of the type [RhX(CO)(PePy(2))], [Rh(diene)(PeP y)](+), and [Rh(diene)(PePy(2))](+) (PePy(n) = P(CH2CH2Py)(n)Ph3-n; Py = 2- pyridyl; n = 1, 2) have been prepared. The two former are square planar; th e latter are pentacoordinated for diene = tetrafluorobenzobarrelene or norb ornadiene (confirmed by X-ray diffraction), but an equilibrium of 4- and 5- coordinate isomers exists in solution for diene = 1,5-cyclooctadiene. The f luxional behavior of all these complexes is studied by NMR spectroscopy. Th e complex [Rh(NBD)(PePy(2))]PF6. Cl2CH2 crystallizes in the monoclinic spac e group P2(1)/n with a = 8.455(1) Angstrom, b = 18.068(3) Angstrom, c = 19. 729(3) Angstrom, beta = 99.658(3)degrees, and Z = 4. The complexes [Rh(dien e)(PePy(2))](+) react with CO to give the dimeric complex [Rh-2(CO)(2){P(CH 2CH2Py)(2)Ph}(2)](BF4)(2) with the pyridylphosphine acting as P,N-chelating and P,N-bridging.