Hydrido(3-hydroxyalkynyl) Complexes as Intermediates in the Activation of Propargyl Alcohol Derivatives by [Cp*RuCl(dippe)] [Cp* = C5Me5, dippe = 1,2-bis(diisopropylphosphanyl)ethane]

The reaction of propargyl alcohol derivatives with the complex [Cp*RuCl(dippe)] [dippe = 1,2-bis(diisopropylphosphane)ethane] and NaBPh4 in MeOH yields hydrido(3-hydroxyalkynyl) compounds [Cp*Ru(H){C≡CC(OH)RR′}(dippe)][BPh4] [R, R′ = Ph, Ph (1a); H, Ph (1b); H, Me (1c)]. These represent intermediates in the formation of 3-hydroxyvinylidene species [Cp*Ru{=C=CHC(OH)RR′}(dippe)][BPh4] [R, R′ = Ph, Ph (2a); H, Ph (2b); H, Me (2c)], into which they irreversibly rearrange both in solution and in the solid state. Solution kinetic studies have been carried out on this isomerization process. Ulterior dehydration processes are feasible, resulting in the formation of allenylidene [Cp*Ru(=C=C=CRR′)(dippe)][BPh4] [R, R′ = Ph, Ph (3a); H, Ph (3b)] or vinylvinylidene [Cp*Ru{=C=CHCH(=CH2)}(dippe)][BPh4] (4) species. The X-ray crystal structure of the novel secondary allenylidene complex [Cp*Ru(=C=C=CHPh)(dippe)][BPh4] is presented.