Metallocene electrochemistry. 3. Reduction-oxidation study of dicyclopentadienyl compounds of ruthenium and titanium in Lewis acid-base molten salts

Voltammetry at vitreous C electrodes of Ru(eta/sup 5/-C/sub 5/H/sub 5/)/sub 2/ and Ti(eta/sup 5/-C/sub 5/H/sub 5/)/sub 2/Cl/sub 2/ in the 0.8:1 molar ratio AlCl/sub 3/-1 butylpyridinium chloride melt reveals an irreversible oxidation (E/sub p/2/ = = +0.68 V, 100 mV s/sup -1/) and a reversible 1e reduction (E/sub 1/2/ = -0.65 V vs. SCE), respectively. These electrode potentials are comparable to those found for each species in nonaqueous, organic electrolytes. In the acidic melts (excess AlCl/sub 3/), Ru(eta/sup 5/-C/sub 5/H/sub 5/)/sub 2/ is oxidized by multistep pathways sensitive to the melt composition, while the Ti(eta/sup 5/-C/sub 5/H/sub 5/)/sup 2 +/ dication is reduced by a reversible 1e step (E/sub 1/2/ = +0.67 V vs. SCE, 2:1 mole ratio melt) in a pC1/sup -/ dependent process. Electrochemical behavior of each of these metallocenes in neutral 1:1 molar ratio melts is complicated.