Titanium(III) ion as a reductant in electron-transfer reactions

Abstract

The reduction of cobalt(III) ammine complexes by titanium(III) perchlorate or sulphate probably proceeds through an inner-sphere (bridged) activated complex. Specific rates observed range from less than 4 × 10^–7 l. mole^–1 sec.^–1 for the reduction of hexamminecobalt(III) ion to 119 l. mole^–1 sec.^–1 for the reduction of the fluoropentaamminecobalt(III) complex. In solutions with high sulphate ion concentration, titanium(IV), not the liberated bridging ligand, causes inhibition of the reaction. The rate of reduction of perchlorate ion by titanium(III) perchlorate is acid dependent, with a specific rate of 1·89 × 10^–4+ 1·25 × 10^–4[H⁺](l. mole^–1 sec.^–1, 25°, ionic strength = 1·0M).