Kinetic Study of the Oxygen-Transfer Reactions from the Oxo Diperoxo Complexes of Molybdenum(VI) and Tungsten(VI) to (Thiolato)- and (Sulfenato)cobalt(III) Complexes

摘要

The (thiolato)cobalt(III) complex (en)2Co(SCH2CH2NH2)(2+) is oxidized first to (en)2Co(S(O)CH2CH2NHZ)(2+) and then much more slowly to (en)2Co(S(O)2CH2CH2NH2)(2+) by the oxo diperoxo complexes of Mo(VI) and W(VI). Nearly quantitative oxygen atom transfer from peroxide to the coordinated sulfur acceptor accompanies these reactions. The reactions are strictly catalytic with respect to the d(0) metal ions, provided sufficient hydrogen peroxide is present to maintain them as oxo diperoxo complexes. The activation of the coordinated peroxo group is impressive; the relative reactivities for each substrate stand in the order WO(O2)2 > WO(OH)(O2)2(-) > MoO(O2)2 > MoO(OH)(o2)2(-) >> H2O2. Second-order rate constants and, with the exception of those for WO(O2)2, activation parameters for all these reactions were determined. The data are insufficient to distinguish whether nucleophilic attack by coordinated sulfur occurs directly at the peroxo ligand or after prior coordination at Mo(VI) or W(VI). Keywords: Reaction kinetics, Oxidation reduction reactions, Reprints. (AW)