Transformations of the chiral diphosphine rhodium catalyst [(1,5-COD)Rh(-)R,R,-DIOP]~+CF_3SO_3~- under conditions of hydrogenation

摘要

Transformation products of the cationic rhodium complex [(1,5-COD)Rh(-)R,R,-DIOP]~+CF_3SO_3~-(1) (COD is cycloocta-1,5-diene and DIOP is (+-)-2,3-O-isopropylidenen-2,3-dihydroxy-1,4-bis(biphenylphosphino)butane), which were obtained in its reactions with molecular hydrogen, base (NEt_3), and solvents in the absence of a substrate, were investigated by ~1H and ~(31) NMR spectroscopy. The solvate complexes [(Solv)_2Rh(-)R,R,-DIOP]~+CF_3SO_3~-, which were generated from complex 1 in its reactin with molecular hydrogen, underent destruction of the diphosphine ligand with elimination of benzene and were subjected to oxidation by traces of moisture an oxyen to form the DIOP dioxide complex with Rh~I. In the absence of hydrogen, complex 1 in solutions produced the diphosphine dioxide rhodium(I) complex and mono-and binuclear rhodium(I) sovlate complexes. The scheme of deactivation of the complex in the absence of the substrate was proposed. The catalytic activity of the solvate complexes [(ArH)Rh(-)R,R-DIOP]~+CF_3SO_3~-, which contain benzene, p-xylene, and mesitylene in the coordiantion sphere, was studied in hydrogenation of Z-#alpha#-acetamidocinnamic acid.