Chlorite ion and chlorine dioxide

These present an interesting dichotomy in their reductions by tm(l,10-phen-anthroline)iron(ri) (ferroin) °. That of CIO2 to CIOJ is rapid, is first-order in each component ki = 1.86 0.13 l.mole sec at 35 °C) and is independent of acidity. Ferriin is the immediate product and an outer sphere electron-transfer is proposed. The reduction of CIO2 is much slower, proceeding at the same rate as dissociation of ferroin at high chlorite concentrations and a major product is feriin dimer, possibly [(phen)2Fe-0-Fe(phen)2] . Clearly the reaction depends on ligand-displacement followed by an inner-sphere electron transfer. 

Reduction of CIOJ by citrate, tartrate and EDTA complexes of Fe(II) and by Cu(NH3)4 has been examined polarographically. All four reactions are first-order in reductant and C102. The data for the citrate and tartrate complexes were not reproducible but estimates of k2 (27 °C) were obtained. The rate data are 

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