title: Mechanistic Insight into Peroxydisulfate Reactivity: Oxidation of the cis,cis-[Ru(bpy)2(OH2)]2O(4+) "Blue Dimer".
abstract: One-electron oxidation of the μ-oxo dimer (cis,cis-[Ru(III)(bpy)2(OH2)]2O(4+), {3,3}) to {3,4} by S2O8(2-) can be described by three concurrent reaction pathways corresponding to the three protic forms of {3,3}. Free energy correlations of the rate constants, transient species dynamics determined by pulse radiolysis, and medium and temperature dependencies of the alkaline pathway all suggest that the rate-determining step in these reactions is a strongly nonadiabatic dissociative electron transfer within a precursor ion pair leading to the {3,4}|SO4(2-)|SO4(•-) ion triple. As deduced from the SO4(•-) scavenging experiments with 2-propanol, the SO4(•-) radical then either oxidizes {3,4} to {4,4} within the ion triple, effecting a net two-electron oxidation of {3,3}, or escapes in solution with ∼25% probability to react with additional {3,3} and {3,4}, that is, effecting sequential one-electron oxidations. The reaction model presented also invokes rapid {3,3} + {4,4} → 2{3,4} comproportionation, for which kcom ∼5 × 10(7) M(-1) s(-1) was independently measured. The model provides an explanation for the observation that, despite favorable energetics, no oxidation beyond the {3,4} state was detected. The indiscriminate nature of oxidation by SO4(•-) indicates that its fate must be quantitatively determined when using S2O8(2-) as an oxidant.
authors.affiliation: †Department of Chemistry, Washington State University, Pullman, Washington 99164, United States.
authors.forename: James K
authors.initials: JK
authors.lastname: Hurst
authors.affiliation: ‡Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, United States.
authors.forename: Margo D
authors.initials: MD
authors.lastname: Roemeling
authors.affiliation: §Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, United States.
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Lymar
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D019281:Dimerization; D004583:Electrons; D015394:Molecular Structure; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism; D013431:Sulfates / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D013431:Sulfates; D012428:Ruthenium