Reactions of vanadium(IV) and (V) with s^2 metal-ion reducing centers

The s^2 centers, Sn(II), Ge(II), and In(I) reduce VO2+ rapidly and quantitatively to VO2+, and In(I) converts VO2+(much more slowly) to V3+. Sn(II) and Ge(II) react measurably with VO2+ only in chloride media in the presence of added Cu(II). Arguments are presented that the V (V) reductions are initiated by a two-unit reduction to V(III)(via a hydroxo bridge), followed by a rapid comproportionation (VIII+ VV(right arrow)2 VIV). The Cu(II)-catalyzed V(IV)-Sn(II) and V(IV)-Ge(II) reactions at high [Cl-] involve preliminary conversion of the catalyst to Cu(I), which then reduces V(IV), and kinetic profiles of the Ge(II) system point to participation of chloride-bound Ge(III) as well.