544-12-7Relevant articles and documents
Galvanic synthesis of AgPd bimetallic catalysts from Ag clusters dispersed in a silica matrix
Alyari, Maryam,Gangishetty, Mahesh,Scott, Robert W. J.,Sudheeshkumar, V.
, p. 8421 - 8428 (2020/12/30)
While bottom-up synthetic strategies for the formation of near-monodisperse clusters have attracted much attention, top-down synthetic strategies in which metals are dispersed into clusters can also be viable. In this study, we follow up previous work that showed the formation of Ag clusters dispersed in a silica matrix by breaking up larger triangular Ag nanoparticles upon calcination in air. AgPd bimetallic catalysts were synthesized via a galvanic replacement reaction of these thermally activated Ag clusters in a silica matrix. The galvanic reaction of the Ag clusters with Pd(ii) salts was monitored by in situ XANES spectroscopy. Interestingly, extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS) studies suggested that the majority of the Ag atoms are located on the surface of the resulting clusters and Pd atoms are in the core region. The catalytic activity for 3-hexyne-1-ol hydrogenation was investigated and the AgPd?SiO2 catalysts showed superior selectivity for the selective hydrogenation to 3-hexene-1-ol.
Study of Precatalyst Degradation Leading to the Discovery of a New Ru0 Precatalyst for Hydrogenation and Dehydrogenation
Anaby, Aviel,Schelwies, Mathias,Schwaben, Jonas,Rominger, Frank,Hashmi, A. Stephen K.,Schaub, Thomas
supporting information, p. 2193 - 2201 (2018/07/25)
The complex Ru-MACHO (1) is a widely used precatalyst for hydrogenation and dehydrogenation reactions under basic conditions. In an attempt to identify the active catalyst form, 1 was reacted with a strong base. The formation of previously unreported species was observed by NMR and mass spectrometry. This observation indicated that complex 1 quickly degraded under basic conditions when no substrate was present. X-ray crystallography enabled the identification of three complexes as products of this degradation of complex 1. These complexes suggested degradation pathways which included ligand cleavage and reassembly, along with reduction of the ruthenium atom. One of the decomposition products, the Ru0 complex [Ru(N(CH2CH2PPh2)3)CO] (5), was prepared independently and studied. 5 was found to be active, entirely additive-free, in the acceptorless dehydrogenation of aliphatic alcohols to esters. The hydrogenation of esters catalyzed by 5 was also demonstrated under base-free conditions with methanol as an additive. Protic substrates were shown to add reversibly to complex 5, generating RuII-hydrido species, thus presenting a rare example of reversible oxidative addition from Ru0 to RuII and reductive elimination from RuII to Ru0.
Selective Cobalt-Catalyzed Reduction of Terminal Alkenes and Alkynes Using (EtO)2Si(Me)H as a Stoichiometric Reductant
Raya, Balaram,Biswas, Souvagya,Rajanbabu
, p. 6318 - 6323 (2016/09/09)
While attempting to effect Co-catalyzed hydrosilylation of β-vinyl trimethylsilyl enol ethers, we discovered that, depending on the silane, solvent, and the method of generation of the reduced cobalt catalyst, a highly efficient and selective reduction or hydrosilylation of an alkene can be achieved. This paper deals with this reduction reaction, which has not been reported before in spite of the huge research activity in this area. The reaction, which uses the air-stable [2,6-bis(aryliminoyl)pyridine)]CoCl2 activated by 2 equiv of NaEt3BH as the catalyst (0.001-0.05 equiv) and (EtO)2SiMeH as the hydrogen source, is best run at ambient temperature in toluene and is highly selective for the reduction of simple unsubstituted 1-alkenes and the terminal double bonds in 1,3- and 1,4-dienes, β-vinyl ketones, and silyloxy dienes. The reaction is tolerant of various functional groups such as bromide, alcohol, amine, carbonyl, di- or trisubstituted double bonds, and water. Highly selective reduction of a terminal alkyne to either an alkene or alkane can be accomplished by using stoichiometric amounts of the silane. Preliminary mechanistic studies indicate that the reaction is stoichiometric in the silane and both hydrogens in the product come from the silane.
