Coupling of Alkynes on a Pd−Pd Bond to Generate an Electrophilic μ-Butenediylidene Moiety

Murahashi, Tetsuro; Otani, Tomohito; Okuno, Taketoshi; Kurosawa, Hideo

doi:10.1002/(sici)1521-3757(20000204)112:3<547::aid-ange547>3.0.co;2-b

Cited by 22 publications

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References 27 publications

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“…The mixture did not change significantly until the temperature was raised to 298 K, where 4a gradually disappeared and a new allylic Pd complex formed, which was identified as [Pd 2 (η 3 -C 3 H 5 )(μ-CCR)(PPh 3 ) 2 ] (7, R= 1-cyclohexenyl). 36 Some allyl acetate was also observed, which reflects the occurrence of the decomposition of the allylic Pd(II) compound to Pd(0), the reactant species in the formation of Pd(I) complex 7. The formation of dialkyne 2 was also observed.…”

Section: ■ Results and Discussionmentioning

confidence: 91%

Palladium-Catalyzed Aerobic Homocoupling of Alkynes: Full Mechanistic Characterization of a More Complex Oxidase-Type Behavior

et al. 2018

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A combined experimental and computational approach has been used to shed light on the mechanism of the Pdcatalyzed oxidative homocoupling of alkynes using oxygen as oxidant. Mechanistic understanding is important because of the synthetically relevant direct involvement of oxygen in the oxidative coupling, and because of the presence of related processes as undesired side reactions in cross-coupling reactions involving terminal alkynes. A low-ligated [Pd(PPh3)(alkyne)] complex is key in the process and it can be conveniently generated from allylic palladium(II) complexes in the presence of a base or from Pd(I) allylic dimers as precatalysts. The catalytic coupling occurs by alkyne metalation to give an anionic [Pd(PPh3)(alkynyl)]complex that is then oxidized by oxygen. The interaction of oxygen occurs only on this electron rich Pd(0) anionic species and leads to a 2-peroxo palladium(II) singlet intermediate that undergoes subsequent protonolysis to a 1-hydroperoxide palladium(II) complex. The second alkyne metalation occurs on the Pd(II) hydroperoxo derivative, this ligand acting as an internal base, to give a bis(alkynyl)Pd(II) complex that evolves to the product by reductive elimination as the product-forming step. This reaction is an oxidase-type process that, in contrast to most Pd-catalyzed oxidative processes, occurs without separation of the substrate transformation and the catalyst oxidation, both processes being intertwined and dependent of one another.

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Section: ■ Results and Discussionmentioning

confidence: 91%

Palladium-Catalyzed Aerobic Homocoupling of Alkynes: Full Mechanistic Characterization of a More Complex Oxidase-Type Behavior

et al. 2018

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“…In addition, the C⋮C stretching band of the ethynyl ligand is observed at 1796 cm -1 , which occurs at Δν = 154 cm -1 lower wavenumbers than for the mononuclear Pd II -ethynyl complex 5a . The C⋮C stretching band is indicative of an additional π-coordination of the triple bond and, hence, the presence of a σ−π-ethynyl ligand. 25a,b …”

Section: Resultsmentioning

confidence: 99%

A Dinuclear Palladium(I) Ethynyl Complex: Synthesis, Structure, and Dynamics

et al. 2001

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The reaction of Pd(η3-C3H5)2 with PiPr3 at −30 °C affords yellow crystals of the PdII complex (iPr3P)Pd(η3-C3H5)(η1-C3H5) (1). At 20 °C 1 transforms into the dinuclear PdI complex {(iPr3P)Pd}2(μ-C3H5)2 (2) due to oxidative C−C coupling of two allyl groups with elimination of 1,5-hexadiene. Heating 1 or 2 in 1,6-heptadiene to 80 °C produces the Pd0 complex (iPr3P)Pd(η2,η2-C7H12) (3). {(η3-C3H5)PdCl}2 reacts with iPr3P to give (iPr3P)Pd(η3-C3H5)Cl (4b), from which further derivatives (iPr3P)Pd(η3-C3H5)X (X = OSO2CF3 (4a), C⋮CH (5a), CH3 (5b)) are obtained by replacement reactions. The mononuclear PdII-acetylide 5a and complex 3 combine to give the dinuclear PdI derivative {(iPr3P)Pd}2(μ-C3H5)(μ2-η2-C2H) (6). The Pd−Pd bond in 6 is unsymmetrically bridged by a π-allyl and a σ−π-ethynyl group, as determined by X-ray structure analysis. The structures of 1, 4a,b, and 6 are dynamic in solution, with 1 undergoing an exchange of the binding modes of the π- and σ-coordinated allyl groups and 4a,b displaying a π/σ-allyl group rearrangement, and in 6 the C⋮CH substituent oscillates in its π-coordination from one PdI atom to the other.

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A Rare Phosphane Coordination Mode: A Symmetricallyμ2-Bridging Phosphole in a Dinuclear Palladium(I) Complex

et al. 2001

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Coupling of Alkynes on a Pd−Pd Bond to Generate an Electrophilic μ-Butenediylidene Moiety

Cited by 22 publications

References 27 publications

Palladium-Catalyzed Aerobic Homocoupling of Alkynes: Full Mechanistic Characterization of a More Complex Oxidase-Type Behavior

Palladium-Catalyzed Aerobic Homocoupling of Alkynes: Full Mechanistic Characterization of a More Complex Oxidase-Type Behavior

A Dinuclear Palladium(I) Ethynyl Complex: Synthesis, Structure, and Dynamics

A Rare Phosphane Coordination Mode: A Symmetricallyμ2-Bridging Phosphole in a Dinuclear Palladium(I) Complex

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