Acid promoted formation of tri- and penta-ruthenium allenylidene complexes

A series of mu (3)-(parallel to) hydroxyalkyne derived species [Ru-3(CO)(9) (mu -CO){mu (3)-C(H)=CC(R)OH(R-1)}] has been prepared. Unexpectedly, the co mplexes (where neither R nor R-1=H) react with alumina to form the correspo nding alkynyl species [Ru-3(CO)(9)(mu -H){mu (3)-C2C(R)OH(R-1)}], a transfo rmation which may also be effected by thermolysis. More importantly, acid i nduced dehydration of the propargyl alcohol species [Ru-3(CO)(9)(mu -CO){mu (3)-C(H)=CC(R)OH(R-1)}] (R=R-1=Ph; R=Ph, R-1=Me) leads to formation of the corresponding allenylidene complexes [Ru-3(CO)(9)(mu -CO){mu (3)-C=C=C(Ph) R}] (R=Ph or Me), [Ru-5(CO)(15)(mu (4)-C=C=CPh2)] and [Ru-5(CO)(15){mu (5)- C=C=C(Ph)Me}]; the pentaruthenium complexes have been shown by X-ray diffra ction studies to contain unprecedented multi-site bound allenylidene ligand s and different metal atom arrangements.