title: Kinetic studies of oxygen atom transfer reactions from trans-dioxoruthenium(VI) porphyrins to sulfides.
abstract: The kinetics of the reactions of three trans-dioxoruthenium(VI) porphyrin derivatives with organic sulfides were measured. The dioxo systems studied were 5,10,15,20-tetramesityl porphyrin-dioxoruthenium(VI) (2a), 5,10,15,20-tetraphenylporphyrin-dioxoruthenium(VI) (2b), and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin-dioxoruthenium(VI) (2c). Species 2 were competent oxidants and reacted rapidly with thioanisoles to generate the corresponding sulfoxides. Typical second-order rate constants determined from pseudo-first-order kinetic studies for sulfoxidation reactions are 8-60 M(-1)s(-1), which are 3 orders of magnitude larger in comparison with those of well studied alkene epoxidations and activated C-H bond oxidations by the same dioxo species. For a given sulfide substrate, the reactivity order for the dioxoruthenium(VI) species was 2a<2b<2c, which is in agreement with expectation on the basis of the electron-withdrawing and steric effects of the porphyrin macrocycles. Various para-substituted thioanisoles react in a narrow kinetic range with the same dioxo species. The kinetic results obtained in this study indicate a concerted oxygen atom transfer and/or electron transfer followed by oxygen transfer mechanism from oxidant to sulfide. Competition kinetic reactions with a catalytic amount of porphyrin ruthenium(II) species and a terminal oxidant give relative rate constants for sulfoxidations of competing substrates that are somewhat smaller than the ratios of absolute rate constants, implying a multiple oxidant model for sulfoxidation reactions.
authors: Department of Chemistry, Western Kentucky University, Bowling Green, KY 42101-1079, USA.
authors: Chris
authors: C
authors: Abebrese
authors: Yan
authors: Y
authors: Huang
authors: Alice
authors: A
authors: Pan
authors: Zhibo
authors: Z
authors: Yuan
authors: Rui
authors: R
authors: Zhang
mesh_terms: D002384:Catalysis; D007700:Kinetics; D008665:Metalloporphyrins / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*
chemical_list: D008665:Metalloporphyrins; D013440:Sulfides; D010100:Oxygen