REDOX BEHAVIOR OF TRINUCLEAR M-3(MU-H)(MU(3)-ETA(1)ETA(2)ETA(2)-C(2)FC)(CO)(9) AND TETRANUCLEAR RUM3(MU-H)(MU-4-ETA(1)ETA(1)ETA(1) ETA(2)-C(2)FC)(CO)(12) (M = RU OR OS, AND FC = FERROCENYL) CLUSTERS - ELECTRONIC INTERACTION BETWEEN THE FERROCENYLACETYLIDE LIGAND AND THE METAL CORE OF THE CLUSTER

The redox properties of the clusters Ru-3(CO)(12) (1), -3(mu-H)(mu(3)- eta(1):eta(2):eta(2)-C(2)Fc)(CO)(9) (2), -3(mu-H)(mu(3)-eta(1):eta(2): eta(2)-C(2)Fc)(CO)(9) (3), (mu(4)-eta(1):eta(1):eta(1):eta(2)-C(2)Fc)( CO)(12) (4), and (mu(4)-eta(1):eta(1):eta(1):eta(2)-C(2)Fc)(CO)(12) (5 ) in THF have been studied by cyclic voltammetry in the temperature ra nge from -60 to +20 degrees C. It was demonstrated that reversible one -electron oxidation of the ferrocenyl fragment in clusters 2-5 occurs at more positive potentials (Delta E-0 = 0.15-0.26 V) than that of fre e ferrocene. This is indicative of the electron-withdrawing character of the cluster core with respect to the ferrocenylacetylide ligand. Th e electron-withdrawing effect of the metal core is more pronounced in tetranuclear cluster 4 and 5 than in trinuclear clusters 2 and 3. Unli ke complex 1-3, which undergo irreversible reduction, complexes 4 and 5 undergo reversible one-electron reduction to form the corresponding radical anions 4(.-) and 5(.-).