The sterically hindered complex cis-[Ru(dMP)2(S)2(PF6)2 (S = H2O; CH3CN), where dmp is 2,9-dimethyl-1,10-phenanthroline, catalyzes the oxidations of alkenes with dioxygen and of alkanes with hydrogen peroxide under mild pressures (40-50 psig) and temperatures (65-75-degrees=C). The reaction of norbornene, O2, and a catalytic amount of [Ru(dmp)2(CH3CN)2](PF6)2 results in 2,3-epoxynorbornane with 94% selectivity. Mechanistic experiments suggest that a free-radical reaction between cis-[Ru(dmp)2(CH3CN)2](PF6)2, norbornene, and O2 occurs initially to generate a high-valent ruthenium oxo species involved in an oxygen atom-transfer catalytic cycle with O2. In the presence of H2O2 and a catalytic amount of cis-[Ru(dMP)2(S)2](PF6)2 (S = H2O; CH3CN), unactivated alkanes are hydroxylated. Studies of this reaction indicate a free-radical mechanism in which H atom abstraction is the rate-determining step (k(H)/k(D) = 4 for cyclohexane).