Novel pathways in the reactions of superoxometal complexes

The reaction of a 1:1 mixture of (H2O)(5)Cr(O-16(2))(2+) and (H2O)(5)Cr(O-18(2))(2+) at pH 1 did not yield measurable amounts of (OO)-O-16-O-18. This result rules out a Russell-type mechanism (2(H2O)(5)CrO22+ --> 2(H2O)(5)CrO2+ + O-2) for the bimolecular decomposition reaction. Evidence is presented in support of unimolecular (S(H)1) and bimolecular (S(H)2) homolyses as initial steps in the decomposition of (H2O)(5)CrO22+ in strongly acidic solutions (pH less than or equal to 1). In the pH range 4-5, (H2O)(5)CrO22+ undergoes hydrolysis-induced disproportionation to (H2O)(5)CrO2H2+, Cr(H2O)6(3+) and O-2. The first step produces HO2./O-2(.-) which in further reaction with (H2O)(5)CrO2+ yields the observed products.