Reductions of oxo species by aquatitanium(ii) as catalyzed by titanium(iv)

Abstract

Titanium(II) solutions, prepared by dissolving titanium wire in triflic acid + HF, contain equimolar quantities of Ti(IV). These preparations react readily with oxidizing species such as VO₂⁺, substituted benzoquinones, and the biguanide complex of Mn(IV). Reactions with excess Ti(II) yield Ti(III). Reductions of 1,4-benzoquinones and the Mn(IV) complex are catalyzed by added Ti(IV) but stoichiometry is unaffected. Rate laws for the Ti(IV)-catalyzed reactions are consistent with formation of a Ti^II–Ti^IV complex (K_formation 4 × 10² M⁻¹), which, in some cases, also partakes in contributing deprotonated and halogen-catalyzed paths.