Propargylic Substitution Reaction Catalyzed by Group IV (Ti, Zr, Hf)–Ru Heterobimetallic Complexes

A series of heterobimetallic complexes consisting of group IV metallocenyl diphosphines and Ru were synthesized and structurally characterized. Most of them work as catalysts toward propargylic substitution reaction of 1,1-diphenyl-2-propyn-1-ol (4) with EtOH. The stoichiometric reactions of the heterobimetallic complexes [MCl2(μ-η5:η1-C5H4PEt2)2RuClCp*] (M = Zr, Hf) with 4 and NaBArF4 afforded key reactive intermediate allenylidene complexes [MCl2(μ-η5:η1-C5H4PEt2)2RuCp*(CCCPh2)]BArF4, whose molecular structures were confirmed by X-ray analyses. A plausible reaction pathway for the catalytic reaction is proposed where group IV metal chloride and Ru moieties work cooperatively.