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

A series of ur(||) hydroxyalkyne derived species [Ru3(CO)9(n-CO){nrC(H)=CC(R)OH(R1)}] has been prepared. Unexpectedly, the complexes (where neither R nor R1 = H) react with alumina to form the corresponding alkynyl species [Ru3(CO)9(n-H){|a3-C2C(R)OH(R1)}], a transformation which may also be effected by thermolysis. More importantly, acid induced dehydration of the propargyl alcohol species [Ru3(CO)9(n-CO){nrC(H)=CC(R)OH(R1)}] (R = R1 = Ph; R = Ph, R1 = Me) leads to formation of the corresponding allenylidene complexes [Ru3(CO)9(u-CO){u3-C=C=C(Ph)R}] (R = Ph or Me), [Ru5(CO)I5(n4-C=C=CPh2)] and [Ru5(CO)I5{u5-C=C=C(Ph)Me}]; the pentaruthenium complexes have been shown by X-ray diffraction studies to contain unprecedented multi-site bound allenylidene ligands and different metal atom arrangements.