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

Abstract

A series of μ₃-(∥) hydroxyalkyne derived species [Ru₃(CO)₉(μ-CO){μ₃-C(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(μ-H){μ₃-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(μ-CO){μ₃-C(H)CC(R)OH(R¹)}] (R = R¹ = Ph; R = Ph, R¹ = Me) leads to formation of the corresponding allenylidene complexes [Ru₃(CO)₉(μ-CO){μ₃-CCC(Ph)R}] (R = Ph or Me), [Ru₅(CO)₁₅(μ₄-CCCPh₂)] and [Ru₅(CO)₁₅{μ₅-CCC(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.