Rhodium(I) complexes with OPPy2Ph and OPPy3 (Py=2-pyridyl), and their behavior in hydrogenation reactions

The reaction of [Rh-2(mu -Cl)(2)(COD)(2)] (COD = 1,5-cyclooctadiene) or [Rh -2(mu -Cl)(2)(TFB)(2)] (TFB= tetrafluorobenzobicyclo[2.2.2]octatriene) with the N-donor chelating ligand OPPy2Ph (Py = 2-pyridyl) in the presence of T lBF4 affords cationic complexes [Rh(diene)(OPPy2Ph)](BF4) (1, diene: COD; 2 , diene: TFB). Compounds 1 or 2 react with CO to give [Rh(CO)(2)(OPPy2Ph)]( BF4) (4), which is also obtained by treatment of [Rh-2(mu -Cl)(2)(CO)(4)] w ith OPPy2Ph and TIBF4. In a similar way, the complexes [Rh(diene)(OPPy3)] ( BF4) (5, diene: COD; 6, diene: TFB) are obtained when using OPPy3; they rea ct with CO to give [Rh-2(mu -CO)(3)(OPPy3)(2)] (BF4)(2) (9) The behavior of the complexes in solution is reported. The complexes with OPPy3, 5 and 6, show equivalence of the three Py groups in their NMR spectra. Complex 5 is square-planar in the solid state, and in solution, and the uncoordinated an d coordinated Py groups undergo fast exchange in solution. Complex 6 is pen tacoordinated in the solid state and in solution, and its Py groups exchang e their coordination sites in a fast topomerization process. The single-cry stal X-ray structures of 5 and 6 have been solved. The behavior of 1 and 5 as catalysts in hydrogenation reactions of cyclohexene, acetone, and cycloh exanone is also reported.