Competitive catalytic epoxidation and oxidative cleavage of stilbene by ruthenium complexes

The catalytic oxidation of stilbenes, cis- and trans-, by iodosobenzene in the presence of the diphosphino-complexes of ruthenium(II) [RuCl(LL)(2)]PF6 (LL = 1,3-bis(diphenylphosphino) propane, DPP; 1-diphenylphosphino-2-(2'pyridyl)ethane, PPY) gives rise to stilbene epoxides, cis- and trans-, and to benzaldehyde with distinctly different kinetic pathways. The reaction is first-order to the catalyst for the epoxidation and second-order for the oxidative cleavage, whereas the rate dependence upon substrate concentration indicates reversible formation of a common catalyst-substrate intermediate.