Collect. Czech. Chem. Commun. 1996, 61, 574-588

Kinetic Study of Oxygen Transfer Reactions from Oxo-Monoperoxo Complexes of Vanadium(V) to Thiolatocobalt(III) Complex in Water and Concentrated Solutions of Electrolytes

Oľga Vollárováa, Ján Benkoa and Michal Sivákb

a Department of Physical Chemistry, Comenius University, 842 15 Bratislava, Slovak Republic
b Department of Inorganic Chemistry, Comenius University, 842 15 Bratislava, Slovak Republic


[Co(en)2SCH2CH2NH2]2+ ion is oxidized to [Co(en)2SOCH2CH2NH2]2+ by the oxo-monoperoxovanadium(V) complexes in aqueous media. These reactions are accompanied by oxygen atom transfer from the peroxo ligand to the coordinated sulfur atom. The relative reactivities for each substrate stand in the order: [VO(O2)(ada)]- << [VO(O2)nta]2- ~ H2O2 ~ [VO(O2)(H2O)4]+ < [VO(O2)(quin)2]3- << [VO(O2)(H2O)2(pic)], where ada = N-(carbamoylmethyl)iminodiacetato(2-), nta = nitrilotriacetato(3-), quin = 2,3-pyridinedicarboxylato(2-) and pic = 2-pyridinecarboxylato(1-) ligands. The effect of pH on the second order rate constant for oxidation by monoperoxo-nta complex is in the pH range 4.8-6.5 consistent with equation k(298.2 K) = 0.709 + 1.28 . 105 [H+]. Two new oxo-monoperoxo complexes of vanadium(V), NH4[VO(O2)(ada)] . H2O and (NH4)3[VO(O2)(quin)2] . 3 H2O, were synthesized and characterized. The salt effects on the thiolatocobalt(III) oxidation by vanadium(V) oxo-monoperoxo complexes as well as by H2O2 were studied at 298.2 K in different, up to 5 M solutions of electrolytes. The results can be rationalized in terms of the salt-water interactions.

Keywords: Oxo-monoperoxo complexes of vanadium(V); Salt effect; Oxygen transfer reaction.