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++ TiIII, where L3–= N(CH2COO)33–, has been studied in aqueous acidic media. The kinetics are consistent with the stepwise mechanism [Co(NH3)5(HL)]++ TiIII [graphic omitted] [Co(NH3)5LTi]3++ H+ followed by [Co(NH3)5LTi]3+ [graphic omitted] CoII+ TiIV 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.