The aquachromyl ion, (CraqO2+)-O-IV, reacts with the hydrides L(H2O)RhH2+ (L = L-1 = [14]aneN(4) and L-2 = meso-Me-6-[14]aneN(4)) in aqueous solutions in the presence of molecular oxygen to yield Cr-aq(3+) and the superoxo complexes L(H2O)RhOO2+. At 25 degrees C, the rate constants are similar to 10(4) M-1 s(-1) (L = L-1) and 1.12 x 10(3) M-1 s(-1) (L = L-2). Both reactions exhibit a moderate deuterium isotope effect, k(RhH)/k(RhD) = similar to 3 (L-1) and 3.3 (L-2), but no solvent isotope effect, k(H2O)/k(D2O) = 1. The proposed mechanism involves hydrogen atom abstraction followed by the capture of LRh(H2O)(2+) with molecular oxygen. There is no evidence for the formation of L(H2O)Rh2+ in the reaction between L(H2O)RhH2+ and (salen)(CrO+)-O-V. The proposed hydride transfer is supported by the magnitude of the rate constants (L = L-1, k = 8800 M-1 s(-1); (NH3)(4), 2500; L-2, 1000) and isotope effects (L = L-1, kie = 5.4; L-2, 6.2). The superoxo complex [L-1(CH3CN)RhOO](CF3SO3)(2). H2O crystallizes with discrete anions, cations, and solvate water molecules in the lattice. All moieties are linked by a network of hydrogen bends of nine different types. The complex crystallized in the triclinic space group P (1) over bar with a = 9.4257(5) Angstrom, b = 13.4119(7) Angstrom, c = 13.6140(7) Angstrom, alpha = 72.842(1)degrees, beta = 82.082(1)degrees, gamma = 75.414(1)degrees, V = 1587.69(14) Angstrom(3), and Z = 2.