Oxygenation of a low valent rhodium complex, TpiPr2 Rh(dppe):: sequential conversion of molecular oxygen into peroxo and hydroperoxo complexes and characterization of the peroxo species

Sequential conversion of molecular oxygen into peroxo- and hydroperoxo-metal species involved in an effective O-2-activation is verified for the Tp(iPr2)Rh system by isolation and characterization of the intermediates. O-2-treatment of the Rh(l) precursor, Tp(iPr2)Rh(dppe) (1), in the presence of 3,5-diisopropylpyrazole (H-pz(iPr2)) gives the kappa(2)-peroxometal complex, Tp(iPr2)(H-pz(iPr2))Rh(kappa(2)-O-2) (2), which is subsequently converted to the hydroperoxo complex, Tp(iPr2)(H-pz(H2))(pz(H2))Rh-OOH (4), upon treatment with pyrazole (H-pz(H2)). The peroxo species 2 and 4 have been characterized by spectroscopic and crystallographic methods and it is revealed that, in the present N-rich coordination system, the basic peroxo ligands (O-2, OOH) form hydrogen-bonding interactions with the proximal N- and NH-functional groups. (C) 2003 Elsevier B.V. All rights reserved.