Kinetics and mechanisms of the reactions of nickel(II) with 4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dione in aqueous solution

Abstract

The kinetics and mechanisms of the reactions of nickel(II) with 4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dione (Htftbd) to form the 1 :1 complex have been studied in aqueous solution at 25 °C and l= 0.2 mol dm^–3 adjusted using sodium sulphate. The equilibrium constants for reaction of Htftbd with proton and Ni²⁺ have also been determined. The kinetic data are consistent with a mechanism in which the metal ion reacts with the enol tautomer of the ligand by acid-independent and inverse-acid paths. The rate constants for reaction of Ni²⁺ with the protonated enol tautomer and with the enolate ion are 11.3 and 1 294 dm³ mol^–1 s^–1 respectively.