Novel Pathways in the Reactions of Superoxometal Complexes

The reaction of a 1:1 mixture of (H(2)O)(5)Cr((16)O(2))(2+) and (H(2)O)(5)Cr((18)O(2))(2+) at pH 1 did not yield measurable amounts of (16)O(18)O. This result rules out a Russell-type mechanism (2(H(2)O)(5)CrO(2)(2+) --> 2(H(2)O)(5)CrO(2+) + 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 (H(2)O)(5)CrO(2)(2+) in strongly acidic solutions (pH </= 1). In the pH range 4-5, (H(2)O)(5)CrO(2)(2+) undergoes hydrolysis-induced disproportionation to (H(2)O)(5)CrO(2)H(2+), Cr(H(2)O)(6)(3+) and O(2). The first step produces HO(2)(*)/O(2)(*)(-), which in further reaction with (H(2)O)(5)CrO(2)(2+) yields the observed products.