Mechanism of the reduction of vanadium(V) by titanium(III) in acidic aqueous solution

Abstract

The reduction of vanadium(V) by titanium(III) in acidic chloride or perchlorate solutions occurs in three distinct consecutive steps; the third was present only with V(V) in excess, while the first two were studied with excess Ti(III). The pseudofirst-order rate constant for the first step follows the equation kl=kr + kf [Ti(III)], where kf = a/(K& + [H+¡) and Ka is the acid dissociation constant of Ti37. For the second step, k2 = £>[Ti(III)] /(l + K[Ti(III)]), where the value of K as well as its [H7] dependence agrees identically with the ratio k¡lkr from the first step, and b = d/(e[H7] + [H7]2). The third step which is identified as the formation of a Ti(IV)-V(V) binuclear complex follows the equation -d In [Ti(IV)] /dr = (f + g[H7] + A[H7]2)[V(V)] xs. Mechanisms for these reactions are presented and discussed. Evidence is also presented for the existence of a dimeric species in Ti(III) solutions.

Oxidation of uranium(IV) by vanadium(V) in perchlorate media

“…They are not necessarily the forms of the ion which take part in the reaction. 6 Values obtained from ref terms of an acid-independent and inversely acid-dependent reaction path, the latter presumably reflecting the participation of the species UOH3+ in the reaction, and its inclusion in the reaction scheme readily yields eq 9. However, comparison of the characteristics of the present reaction with those involving the oxidation of U(IV) by other oxidants (Table VI) shows that the V(V) reaction both is very much faster and exhibits a less pronounced acid dependence than any of the other reactions examined to date.8a The unusual features of the V(V) reaction are particularly emphasized when it is compared with those of Pu(VI) and Np(VI), both of which are oxygenated cations formally similar to V(V) and have only slightly different oxidation potentials.…”

“…-10.0 ± 5.9 30.0 ± 1.1 Rms, Values obtained by least-squares analysis of data by eq 9 6. Values calculated by least-squares analysis of data by the Eyring equation.16c Root-mean-square percent deviation, defined as 100[(1/ ) (/: ß8 "" ^caIcd)%obsd2]'^2• i v i d u a l n o t d i r e c t l y a s s o c i a t e d w i t h s c i t e i s p r o h i b i t e d .…”

Reaction of molecular oxygen and titanium trichloride in anhydrous pyridine

“…More recently, the existence in very low concentration of titanium(III) dimer in aqueous HC1 solutions was proposed to account for kinetic data. 21 Others have used epr spectroscopy to determine the presence and structures of binuclear copper(II) and binuclear vanadyl complexes in solution.22"26 If titanium(III) dimers are formed in solution, a coupling of spins (5, and S2 = V2) will result in a triplet state (S = S1 + S2 = 1) and a singlet state (S = S, -S2 = 0). A magnetic field splits the triplet state into states with Ms = 1, 0, and -1.…”

Assignment of mechanism to titanium(III) reductions of cobalt(III) complexes. Hard and soft theory as a means of assessing bridging ligands for inner-sphere electron transfer

“…Other Ti(III) redox studies have also been reported. [6][7][8] Experimental Section Titanium(III) Solutions. Titanium metal sponge (Johnson and Matthey Chemicals Ltd., 0.5 g) was dissolved in concentrated hydrochloric acid (10 ml) maintained at 40-50 °C (ca.…”

“…Titanium metal sponge (Johnson and Matthey Chemicals Ltd., 0.5 g) was dissolved in concentrated hydrochloric acid (10 ml) maintained at 40-50 °C (ca. 6 h) in air-free conditions. Excess solid was removed using a porosity No.…”