The reactions of transition metal ions with chlorine(III)

Practical applications and unique kinetic phenomena have generated considerable interest in the redox chemistry of chlorine(III). The complex kinetic and stoichiometric features of the related reactions are well documented, but relatively little is known about possible interactions between chlorine(III) and transition metal ions, Recent studies confirmed that the chlorite ion forms weak complexes with common metal ions such as Cu(II), Fe(III) or Hg(II) and the formation of an inert chlorito complex was also reported. This paper reviews kinetic and equilibrium aspects of the formation of chlorito complexes as well as the role of transition metal ions in the redox reactions and the catalytic decomposition of chlorine(III). It will be shown that the metal ions enhance the reactivity of chlorine(III) by activating the O-Cl bond. Chlorito complexes may undergo either redox decomposition or promote the reactions of the coordinated chlorine(III) with other oxychlorine species. It is a common feature that reactive intermediates are formed, which are involved in subsequent fast reactions with the reactants and other intermediates. As a consequence, complex kinetic patterns ensue and the stoichiometries are kinetically controlled. Mechanistic aspects of these reactions will be discussed in detail. (C) 2001 Elsevier Science B.V. All rights reserved.