Complex formation reaction of the iron(III) hydroxo dimer with periodate ion

摘要

The kinetics and mechanism of the ligand substitution reaction between Fe2(OH)24+ and periodate ion has been studied. This process is unique among the reactions of the iron(III) hydroxo dimer because the initial rate is second-order with respect to Fe_2(OH)_2~(4+). The formation of a bi- and a tetranuclear complex, Fe_2(OH)_2(H_4IO_6)~(3+) and Fe_4(OH)_4(H_4IO_6)~(7+), is proposed. Comprehensive fitting of the kinetic data was used to show that the proposed model, which is very similar to earlier models used with other inorganic oxoanions, gives a reasonable interpretation of all observations. It is shown that the lifetime of Fe_2(OH)_2(H_4IO_6)~(3+) is relatively long and it can open a pathway to form oligomeric and less soluble products at higher initial concentrations. The speciation of aqueous periodate ion solution was also studied and it is proposed that the tetrahedral form, IO_4~-, is less dominant over the octahedral form, H_4IO_6~-, than previously thought.