Reactions of vanadium(iv) and (v) with s2 metal-ion reducing centers

Abstract

The s² 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 (V^III + V^V → 2 V^IV). 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.