Abstract
The reaction of [Rh2(µ-Cl)2(COD)2] (COD = 1,5-cyclooctadiene) or [Rh2(µ-Cl)2(TFB)2] (TFB = tetrafluorobenzobicyclo[2.2.2]octatriene) with the N-donor chelating ligand OPPy2Ph (Py = 2-pyridyl) in the presence of TlBF4 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 [Rh2(µ-Cl)2(CO)4] with OPPy2Ph and TlBF4. In a similar way, the complexes [Rh(diene)(OPPy3)](BF4) (5, diene: COD; 6, diene: TFB) are obtained when using OPPy3; they react with CO to give [Rh2(µ-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 and coordinated Py groups undergo fast exchange in solution. Complex 6 is pentacoordinated in the solid state and in solution, and its Py groups exchange their coordination sites in a fast topomerization process. The single-crystal 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 cyclohexanone is also reported.
Published Version
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