Kinetics of the reaction of molecular oxygen with iron(II).–Cysteine complexes

Abstract

The rapid interaction of cysteinate complexes of iron(II) with oxygen in aqueous solution have been examined. By controlling the pH of the solutions it is possible to study separately the reactions of the 1 : 1 and 1 : 2 complexes by use of a stopped-flow apparatus. The rate constants at 25° are 5 ± 1 × 10³ l. mole^–1sec.^–1 for the monocomplex and 2 ± 0·5 × 10⁴ l. mole^–1sec.^–1 for the bis-species. These rates are substantially faster than those for other iron(II)–oxygen reactions and the mechanism is considered to involve metal–sulphur as well as metal–oxygen interactions.