The interaction of [Cp * RuCl(dippe)] and [CpRuCl(dippe)] with alkynols: Hydroxyvinylidene, allenylidene and related derivatives (dippe = 1,2-bis(diisopropylphosphino)ethane)

Article abstract of DOI:10.1016/S0022-328X(97)00472-5

The reactions of [Cp * RuCl(dippe)] and [CpRuCl(dippe)] (dippe = 1,2-bis(diisopropylphosphino)ethane) with several alkynols HC≡CC(OH)RR′ (R = R′ = H, Me; R = Me, R′ = Ph) have been studied. These reactions leads to the formation of the corresponding allenylidene derivatives, although in some cases hydroxyvinylidene complexes were isolated as intermediates in such process. The X-ray crystal structure of [CpRu:=C=C=CMePh(dippe)][BPh₄] was determined. In the course of the reaction of [CpRuCl(dippe)] with HC≡CC(OH)Me₂, there is evidence for the formation of a deep blue dimeric alkynyl-carbene (or alkenyl-allenylidene) complex [{CpRu(dippe)}₂(μ-C₁₀H₁₁)][BPh₄] resulting formally from the coupling of two allenylidene moieties followed by the loss of one proton. The reaction of [Cp * Ru=C=C=CMePh(dippe)][BPh₄] with KOBu^t leads to the ene-yne derivative [Cp * Ru(C≡CC(Ph)=CH₂)(dippe)] as result of the deprotonation of the allenylidene ligand at the δ-position. This compound was structurally characterized by single crystal X-ray crystallography. In an attempt to obtain the primary allenylidene complex [Cp * Ru=C=C=CH₂(dippe)][BPh₄] by dehydration of the hydroxyvinylidene [Cp * Ru=C=CHCH₂OH(dippe)][BPh₄] using P₂O₅, the previously reported carbonyl complex [Cp * Ru(CO)(dippe)][BPh₄] was obtained and its crystal structure determined. This is also accessible by aerial oxidation of the hydroxy-vinylidene derivative.