Catalytic oxidation of hydrocarbons with O2 or H2O2 using a sterically hindered ruthenium complex

Article abstract of DOI:10.1021/ja00085a023

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 °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 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).