title: Electron transfer-oxygen transfer oxygenation of sulfides catalyzed by the H5PV2Mo10O40 polyoxometalate.
abstract: The oxygenation of sulfides to the corresponding sulfoxides catalyzed by H(5)PV(2)Mo(10)O(40) and other acidic vanadomolybdates has been shown to proceed by a low-temperature electron transfer-oxygen transfer (ET-OT) mechanism. First, a sulfide reacts with H(5)PV(2)Mo(10)O(40) to yield a cation radical-reduced polyoxometalate ion pair, R(2)(+*),H(5)PV(IV)V(V)Mo(10)O(40), that was identified by UV-vis spectroscopy (absorptions at 650 and 887 nm for PhSMe(+*) and H(5)PV(IV)V(V)Mo(10)O(40)) and EPR spectroscopy (quintet at g = 2.0079, A = 1.34 G for the thianthrene cation radical and the typical eight-line spectrum for V(IV)). Next, a precipitate is formed that shows by IR the incipient formation of the sulfoxide and by EPR a VO(2+) moiety supported on the polyoxometalate. Dissolution of this precipitate releases the sulfoxide product. ET-OT oxidation of diethylsulfide yielded crystals containing [V(O)(OSEt(2))(x)(solv)(5-x)](2+) cations and polyoxometalate anions. Under aerobic conditions, catalytic cycles can be realized with formation of mostly sulfoxide (90%) but also some disulfide (10%) via carbon-sulfide bond cleavage.
authors.affiliation: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Khenkin
authors.forename: Gregory
authors.initials: G
authors.lastname: Leitus
authors.forename: Ronny
authors.initials: R
authors.lastname: Neumann
mesh_terms: D002384:Catalysis; D004579:Electron Transport; D008958:Models, Molecular; D008982:Molybdenum / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D013454:Sulfoxides / Q000138:chemical synthesis* / Q000737:chemistry; D014639:Vanadium / Q000737:chemistry*
chemical_list: D013440:Sulfides; D013454:Sulfoxides; D014639:Vanadium; D008982:Molybdenum; D010100:Oxygen