Kinetic studies on the periodate oxidation of an iron(II) oxime‐imine complex

The iron(II) complex of H₂L (H₂L=3, 14‐dimethyl‐4, 7, 10, 13‐tetraazahexadeca‐3,13‐diene‐2,15‐dione dioxime, Coord. Chem. Rev., 33, 87 (1980)) is oxidized by periodate very rapidly in the range pH 2.0–7.0, and the kinetics of the reaction has been followed by stopped‐flow spectrophotometry at 30°C and ionic strength I=0.20 mol L⁻¹ (NaClO₄). The reaction is found to follow a simple second‐order kinetics as −d/dt Fe^II(H₂L)²⁺]=k Fe^II(H₂L)²⁺] I(VII)], giving Fe^III(L)]⁺ and IO₃⁻ as the final products. The reaction has been proposed to occur through a H‐bonded transition state formed probably between the protonated oxime group of the ligand and the oxygen atom on the periodate species, followed by an electron transfer from Fe^II centre to I^VII in a rate‐determining step. The I^VI species thus generated reacts in a fast step with another Fe^II complex. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 23–28, 1999