Electron transfer. 137. Formal potentials involving indium(II)

Aqueous solutions of indium(III) undergo le(-) reductions by Sm(II) (E-0 -1.55 V) and by Yb(II) (-1.05 V), but not by U(III) (- 0.52 V). The facile and irreversible reduction, by In-aq(+), of Ru(NH3)(6)(3+) (E-0 +0.067 V) at reagent concentrations near 10(-3) M implies a potential more negative than -0.23 V for In(II,I) and, in conjunction with the known value of -0.43 V for In(III,I), a complementary potential less negative than -0.65 V for In(III,II). These observations, taken together, support le(-) indium potentials E-II,I(0) -0.2 V and E- III,II(0) -0.6 V.