7642-15-1Relevant articles and documents
Hydrogen transfer from formic acid to alkynes catalyzed by a diruthenium complex
Gao,Jennings,Puddephatt
, p. 915 - 921 (2001)
The diruthenium(0) complex [Ru2(μ-CO)(CO)4(μ-dppm)2] (1) (dppm = Ph2PCH2PPh2), is a catalyst for the transfer hydrogenation, using formic acid as hydrogen donor, of the alkynes PhC≡CPh, PhC≡CMe, EtC≡CEt, and PrC≡CPr but not of the terminal alkynes HC≡CH, PhC≡CH, BuC≡CH, or the alkynes containing one or two electron-withdrawing substituents PhC≡CCO2Me and MeO2CC≡CCO2Me. In the successful reactions, the formic acid is first decomposed to carbon dioxide and hydrogen, which then hydrogenates the alkynes in a slower reaction. In the unsuccessful reactions, the decomposition of formic acid is strongly retarded by the alkyne. In the case with the alkyne PhC≡CH, it is shown that the alkyne reacts with protonated 1 to give first [Ru2(μ-CPh=CH2)(CO)4(μ-dppm) 2][HCO2], which then isomerizes to give the catalytically inactive, stable complex [Ru2(μ-CH=CHPh)(CO)4(μ-dppm)2][HCO 2]. This complex has been structurally characterized and both of the μ-styrenyl complexes are shown to be fluxional in solution.
5 - Endo ring closures of allylic hydroperoxides: Useful routes to 1,2 - dioxolanes involving strongly stereoselective free radical and polar reactions
Courtneidge, John L.,Bush, Melanie,Loh, Lay See
, p. 3835 - 3856 (1992)
Intramolecular cyclisation of simple allylic hydroperoxides to give substituted 1,2 - dioxolanes using electrophilic reagents has been investigated. Closure using mercury(II) acetate and electrophilic halogen reagents (NBS, Br2 ButOC1) occurs by Markovnikov - directed and conformationally strict stereospecificity. Subsequent free - radical reaction of the mercurated dioxolanes involved specific reaction involving reaction from the sterically unprotected face of the intermediate dioxolanyl radical.
Catalytic Hydrogenation of Alkenes and Alkynes by a Cobalt Pincer Complex: Evidence of Roles for Both Co(I) and Co(II)
Alawisi, Hussah,Arman, Hadi D.,Tonzetich, Zachary J.
, p. 1062 - 1070 (2021/04/09)
The Co(I) complex, [Co(N2)(CyPNP)] (CyPNP = anion of 2,5-bis-(dicyclohexylphosphinomethyl)pyrrole), is active toward the catalytic hydrogenation of terminal alkenes and the semi-hydrogenation of internal alkynes under 2 bar of H2 (g) at room temperature. The products of alkyne semi-hydrogenation are a mixture of E- and Z-alkenes. By contrast, use of the related cobalt(I) precatalyst, [Co(PMe3)(CyPNP)], results in formation of exclusively Z-alkenes. A semi-stable Co(II) species, [CoH(CyPNP)], can also be generated by treatment of degassed solutions of [Co(N2)(CyPNP)] with H2. The CoII-hydride displays activity toward both alkene hydrogenation and isomerization, but its instability hampers implementation as a catalyst. Several species relevant to potential catalytic intermediates have been isolated and detected in solution. These compounds include alkene and alkyne adducts of Co(I) as well as a Co(III) dihydride species. Catalytic results with the compounds examined are most consistent with a process involving shuttling between Co(I) and Co(III) states. However, generation of small quantities of Co(II) during catalytic turnover appears to be responsible for the isomerization observed for alkyne semi-hydrogenation. The interplay of cobalt oxidation states within the same catalyst system is discussed in the context of mechanistic scenarios for catalytic hydrogenation.
Pd, Cu and Bimetallic PdCu NPs Supported on CNTs and Phosphine-Functionalized Silica: One-Pot Preparation, Characterization and Testing in the Semi-Hydrogenation of Alkynes
Sánchez-Resa, Daniel,Delgado, Jorge A.,Fernández-Martínez, Maria Dolores,Didelot, Chloé,De Mallmann, Aimery,Szeto, Ka? C.,Taoufik, Mostafa,Claver, Carmen,Godard, Cyril
supporting information, p. 4970 - 4978 (2021/11/10)
Triphenylphosphine stabilized Pd, Cu and PdCu nanocatalysts supported on carbon nanotubes (CNTs) or phosphorus functionalised silica (P?SiO2) were prepared via a one-pot methodology. The series of P?SiO2 supported catalysts evidenced metal particle sizes of metallic nanoparticles (M-NPs) between 1 and 2.4 nm, smaller than their equivalents on CNTs (2.4–2.6 nm). Such a difference in particle size as a function of the support and the metallic composition indicated the more pronounced mediation of the CNTs support during the formation of the M-NPs when compared to the P?SiO2 support. The series of supported catalysts were tested in the semi-hydrogenation of alkynes providing differences in reactivity which might be correlated with the size and composition of the M-NPs and the nature of corresponding support. The carbon supported catalysts displayed in general higher activities than those supported on silica and the bimetallic catalyst PdCu/CNTs were the most selective for the case of alkyl substituted alkynes. This catalyst could moreover be recycled several times without loss of activity nor selectivity.
