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]

Abstract

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.

Activation of alkynes by {[Cp∗Ru(CO)(PMeiPr2)]+}: X-ray crystal structures of and

“…At variance with the related systems containing two phosphine ligands [5][6][7][8][9], in this case there is no evidence for the formation of a Ru IV hydrido-alkynyl complex as intermediate in the alkyne to vinylidene tautomerization. This reflects the important change in the electron richness, and in hence, in the reactivity of the metal centre when replacing one bulky, strong electron-releasing phosphine ligand by the much smaller, p-acceptor CO ligand.…”

“…As it occurs in other cases previously reported, the process involves most likely the formation of a hydroxyvinylidene intermediate [6][7][8][9]11] which undergoes spontaneous dehydration affording the dark purple allenylidene complex 7 (Scheme 1). The resonance for the ruthenium-bound C a atom of the allenylidene ligand appears as one doublet at 289 ppm in the 13 C{ 1 H} NMR spectrum.…”

“…In this work we report the outcome of our investigations on the activation of alkynes by the fragment {[Cp * Ru(CO)(PMe i Pr 2 )] + }. Here, we compare the results with those previously obtained with the {[Cp * Ru(P) 2 ] + } ((P) 2 = dippe [6,7,11], (PEt 3 ) 2 [7,8,10], (PMe i Pr 2 ) 2 [9]) fragments and the analogous less electron rich {[CpRu(CO)(P i Pr 3 )] + } fragment [13].…”

“…The involvement of transition metal vinylidene and allenylidene complexes in the stoichiometric and catalytic transformations of alkynes is well established [1][2][3][4]. We have previously reported the isolation of metastable half-sandwich Ru IV alkynylhydrido complexes of the type [Cp * RuH(C"CR)(P) 2 ] + ((P) 2 = 1,2-bis(diisopropylphosphino)ethane (dippe) [5,6], (PEt 3 ) 2 [7,8], (PMe i Pr 2 ) 2 [9]) as intermediates in the formation of vinylidene complexes. Our research group has reported very recently the isolation and structural characterization of three isomers of the acetylene adduct [Cp * Ru(C 2 H 2 )(PEt 3 ) 2 ][BPh 4 ], namely the g 2 -acetylene, hydridoacetylide and vinylidene forms [10].…”

“…Hydroxyalkynylhydrido complexes have been also characterized as intermediate species in the formation of hydroxyvinylidene complexes, which by subsequent dehydration alternatively lead to allenylidene, vinylvinylidene or hydrido-enynyl derivatives [5][6][7][8][9]11]. In the context of our studies in the chemistry of pentamethylcyclopentadienylruthenium complexes, we have recently reported the complexes [Cp * RuCl(CO)(PMe i Pr 2 )] and the cationic acetone adduct [Cp * Ru{OC(CH 3 ) 2 }(CO)-(PMe i Pr 2 )] + [12].…”