Electron Transfer. 130. Reductions with Indium(I)(1).
Aqueous solutions of the hypovalent state indium(I) have been prepared by treatment of In(Hg) with silver triflate in acetonitrile, followed by dilution with oxygen-free water. These solutions are stable for over 5 h at 25 degrees C. In(I)(aq) reacts with oxidants of the type [(NH(3))(5)Co(III)(Lig)](2+) (In(I) + 2Co(III) --> In(III) + 2Co(II)), and kinetic profiles are consistent with a two-step sequence proceeding with formation of the metastable state In(II), which reacts rapidly with Co(III). Rate ratios for reductions of halogeno-substituted oxidants point to predominance of halide-bridged paths for the chloro, bromo and iodo complexes. Reductions of carboxylato-substituted derivatives are slow but appear to entail inner-sphere precursors if aided by an O-donor group in a position favorable for chelation. In no case is there evidence for reaction via initial reduction of the ligand (the radical-cation mechanism) although the potential of the In(I,II) couple (-0.40 V) allows this path for carbonyl-substituted oxidants. Reductions by In(I), like those by Eu(II), make no significant use of bridging by heterocyclic donor nitrogen centers in pyridine and pyrazine complexes.
Chandra
Swapan K.
SK
Department of Chemistry, Kent State University, Kent, Ohio 44242.
Gould
Edwin S.
ES