Electron transfer reactions of peroxydisulfate and fluoroxysulfate reactions with the cyanide complexes M(CN)(n)(4-) (M=Fe(II), Ru(II), Os(II), Mo(IV), and W(IV))

摘要

The stoichiometry and the kinetics of oxidation of the cyanide complexes M(CN)(n)(4-) (M = Fe(II), Ru(II), Os(II), Mo(IV), and W(IV)) by the peroxydisulfate ion, S2O82-, and by the much more strongly oxidizing fluoroxysulfate ion, SO4F-, were studied in aqueous solutions containing Li+. Reactions of S2O82- with M(CN)(n)(4-) are known to be strongly catalyzed by Li+ and other alkali metal ions, and this applies also to the corresponding reactions of SO4F-. The primary reactions of S2O82- and SO4F- have both been found to be one-electron processes in which the equally strong O-O and O-F bonds are broken. The primary reaction of S2O82- consists of a single step yielding M(CN)(n)(3-), SO4-, and SO42-, whereas the primary reaction of SO4F- comprises two parallel one-electron steps, one leading to M(CN)(n)(3-), SO4-, and F- and the other yielding M(CN)(n-1)(2-,) CN-, SO4- and F-. The relationship between the rate constants and the standard free energies of reaction for the Li+-catalyzed reactions of SO4F- and S2O82- with M(CN)(n)(4-), and for the uncatalyzed reactions of S2O82- with bipyridyl and phenanthroline complexes MLn2+ (M = Fe(II), Ru(II), and Os(II)) studied previously, suggests that the intrinsic barrier for all three sets of reactions is similar, i.e., unaffected by the Li+ catalysis, and that the electron transfer and the breakage of the O-O and O-F bonds are concerted processes.