Kinetics of the electron-transfer reaction of penta-ammine(nitrilotriacetato)cobalt(III) and titanium(III): evidence for a binuclear intermediate

Abstract

The reaction [Co(NH₃)₅(H₂L)]²⁺+ Ti^III, where L^3–= N(CH₂COO)₃^3–, has been studied in aqueous acidic media. The kinetics are consistent with the stepwise mechanism [Co(NH₃)₅(HL)]⁺+ Ti^III [graphic omitted] [Co(NH₃)₅LTi]³⁺+ H⁺ followed by [Co(NH₃)₅LTi]³⁺ [graphic omitted] Co^II+ Ti^IV with k=a/(b+[H⁺]). At 25 °C, log *K₁= 1.60 ± 0.18 and 1.73 ± 0.21 at ionic strength 1.0 mol dm^–3(LiClO₄ and NaCl respectively), a= 0.046 ± 0.005 (NaCl) and 0.055 ± 0.010 (LiClO₄) mol dm^–3 s^–1, and a/b= 1.0 ± 0.1 s^–1(NaCl). The formation of the binuclear intermediate is confirmed by rapid-scan spectroscopy. The mechanism of the intramolecular electron-transfer reaction is discussed.