KINETICS AND MECHANISMS OF THE REACTIONS OF COPPER(II) AND OXOVANADIUM(IV) WITH HEPTANE-3,5-DIONE IN AQUEOUS-SOLUTION

The kinetics and mechanisms of the reactions of copper(II) and oxovanadium(IV), [VO]2+ with heptane-3,5-dione to form the 1:1 complex have been investigated in aqueous solution at 25 °C and ionic strength 0.5 mol dm-2 NaClO4 using the stopped- flow technique. In the case of copper(II), two separate reactions were observed, while only one reaction was observed when oxovanadium(IV) was the metal species. A detailed mechanism is proposed to account for the kinetic data. Cu2+ reacts with the enol and keto tautomers of the ligand with rate constants of 1.14 × 104 and 8.9 dm3 mol-1 s-1, respectively. [VO]2+ reacts with the enol and keto tautomers with rate constants of 5.33 and 0.986 dm3 mol-1 s-1, respectively, while [VO(OH)]+ reacts with the keto tautomer with a rate constant of 7.64 dm3 mol-1 s-1. The results are discussed in the light of previous investigations. © 1990.