Electrochemical generation of hydridopentamminerhodium(III) and its reaction with molecular oxygen

The electrochemistry of Rh(NH 3 ) 5 OH 2+ has been studied in a buffered ammoniacal solution. The polarographic reduction wave at the dropping mercury electrode had E 1/2 0 equal to −1.10 V (vs. saturated calomel electrode) in a 0.10 M NH 3 – 0.10 M NH 4 ClO 4 electrolyte, and gross Hg cathode electrolysis at −1.19 V produced a stable Rh(NH 3 ) 5 H 2+ hydride species. Both reductions were found to take place through a Rh(I) intermediate.The reaction of the Rh(NH 3 ) 5 H 2+ with molecular O 2 in the ammoniacal electrolyte was also studied. The product was demonstrated to be a stable Rh(NH 3 ) 4 (OH)(O 2 H) + hydroperoxo species.