Trinuclear benzene clusters of ruthenium and osmium

The activated cluster [Os3(CO)7(mu(3)-eta(2):eta(2):eta(2)-C6H6)(C2H4)(MeCN)] reacts with alkynes RC2R' (R = R' = H, Ph or Me; R = H, R' = Ph; R = Me, R' = Et) to produce the new clusters [Os3(CO)7(eta(6)-C6H6)(mu(3)-eta(2)-RC2R')] in which the benzene molecule has migrated to a single osmium atom. In contrast, reaction of the ruthenium cluster [Ru3(CO)9(mu(3)-eta(2):eta(2):eta(2)-C6H6)] with similar alkynes RC2R' (R = R' = H, Ph or Me; R = Ph, R' = H) yields the new clusters [Ru3(CO)7(eta(6)-C6H6)(mu(3)-eta(2)-RC2R'CO)] in which carbonyl insertion has occurred. The molecular structures of [Os3(CO)7(eta(6)-C6H6)(mu(3)-C6H6(mu(3)-eta(2)C2Me)] and of [Ru3(CO)7(eta(6)-C6H6)(mu(3)-eta(2)-PhC2PhCO)] have been established by single-crystal X-ray analysis. The C6H6 ligand is eta(6)-bonded to a single metal atom, while the C2Me2 and the PhC2PhCO ligands lie above the metal triangles and are bonded to the three metal atoms via two sigma interactions and one pi interaction.