Oxygenation of a low valent rhodium complex, TpiPr2Rh(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 O2-activation is verified for the TpiPr2Rh system by isolation and characterization of the intermediates. O2-treatment of the Rh(I) precursor, TpiPr2Rh(dppe) (1), in the presence of 3,5-diisopropylpyrazole (H-pziPr2) gives the κ2-peroxometal complex, TpiPr2(H-pziPr2)Rh(κ2-O2) (2), which is subsequently converted to the hydroperoxo complex, TpiPr2(H-pzH2)(pzH2)Rh–OOH (4), upon treatment with pyrazole (H-pzH2). 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 (O2, OOH) form hydrogen-bonding interactions with the proximal N- and NH-functional groups.