Electron transfer. 141. Reactions of indium(I) with transition metal center oxidants

Aqueous solutions of the hypovalent state In(I) reduce a series of complexe s of Fe(III) and selected derivatives of Ir(IV), Cr(V), Pt(IV), Ag(III), an d Ni(IV). All reactions yield In(III). Ions derived from Fe(III) and Ir(IV) undergo net le(-) conversions, whereas the other oxidants change by two un its. Reductions of Fe(III) are strongly promoted by increasing pH or by add ing Cl-, Br-, NCS-, or N-3(-). Reaction appears to proceed through monoliga ted complexes, Fe-III(Lig(-))(2+), and the kinetic response to alteration o f added ligand indicates initiation mainly via a bridged transition state F e-III-Lig-In-I. Oxidations by Fe(CN)(6)(3-) are exceptionally rapid, those by Fe-III(EDTA) are unusually slow, and redox is blocked by addition of exc ess F-. Reduction of IrCl62- proceeds somewhat more slowly than predicted b y the Marcus model for outer-sphere reactions, Conversions of the 2e(-) oxi dants are rapid. For these, multistep routes initiated by le- changes are r easonable, but direct 2e(-) paths involving oxygen transfer (from (CrO)-O-V ) or Cl+ transfer (from PtCl62-) cannot be ruled out. Whether inner-sphere 2e(-) transactions without transfer of atomic species can be competitive re mains an open question.