1315461-60-9Relevant academic research and scientific papers
Addressing Reversibility of R-NHC Coupling on Palladium: Is Nano-to-Molecular Transition Possible for the Pd/NHC System?
Denisova, Ekaterina A.,Eremin, Dmitry B.,Gordeev, Evgeniy G.,Tsedilin, Andrey M.,Ananikov, Valentine P.
, p. 12218 - 12227 (2019/09/30)
It has recently been shown that palladium-catalyzed reactions with N-heterocyclic carbene (NHC) ligands involve R-NHC coupling accompanied by transformation of the molecular catalytic system into the nanoscale catalytic system. An important question appeared in this regard is whether such a change in the catalytic system is irreversible. More specifically, is the reverse nano-to-molecular transformation possible? In view of the paramount significance of this question to the area of catalyst design, we studied the capability of 2-substituted azolium salts to undergo the breakage of C-C bond and exchange substituents on the carbene carbon with corresponding aryl halides in the presence of Pd nanoparticles. The study provides important experimental evidence of possibility of the reversible R-NHC coupling. The observed behavior indicates that the nanosized metal species are capable of reverse transition to molecular species. Such an option, known for phosphine ligands, was previously unexplored for NHC ligands. The present study for the first time demonstrates bidirectional dynamic transitions between the molecular and nanostructured states in Pd/NHC systems. As a unique feature, surprisingly small activation barriers (18 kcal/mol) and noticeable thermodynamic driving force (-5 to -7 kcal/mol) were calculated for C-C bond oxidative addition to Pd(0) centers in the studied system. The first example of NHC-mediated Pd leaching from metal nanoparticles to solution was observed and formation of Pd/NHC complex in solution was detected by ESI-MS.
Intercepting low oxidation state main group hydrides with a nucleophilic N-heterocyclic olefin
Ibrahim Al-Rafia,Malcolm, Adam C.,Liew, Sean K.,Ferguson, Michael J.,McDonald, Robert,Rivard, Eric
supporting information; experimental part, p. 6987 - 6989 (2011/08/08)
The N-heterocyclic olefin, IPrCH2 (IPr = [(HCNDipp) 2C], Dipp = 2,6-iPr2C6H3) has been demonstrated to be of sufficient Lewis basicity to stabilize main group hydrides in unusually low oxidation states.
Recyclable catalysts for palladium-catalyzed C - O coupling reactions, Buchwald-Hartwig aminations, and Sonogashira reactions
Dumrath, Andreas,Wu, Xiao-Feng,Neumann, Helfried,Spannenberg, Anke,Jackstell, Ralf,Beller, Matthias
supporting information; experimental part, p. 8988 - 8992 (2011/02/23)
Simply reuse: Homogeneous palladium catalysts are effective and attractive tools for advanced organic synthesis (see example). Compound 1 belongs to a new class of ligands that enable recycling of the precious-metal catalyst directly from the reaction without any heterogenization.
