Palladate salts from ionic liquids as catalysts in the Heck reaction

Abstract

Palladate salts from imidazolium and pyridinium ionic liquids (ILs) were used as catalysts in Heck reaction. When compared to traditional precatalysts, they demonstrated to be more efficient catalysts. These results are attributed to the presence of nanoparticles (NPs) which served as a reservoir of palladium species. Indeed the use of palladate salts from ILs, that produce no byproducts, provide better control of the formation and surface composition of the NPs leading to a constant recyclability.

About the interactions between nanoparticles and imidazolium moieties: emergence of original hybrid materials

“…As highlighted in the preceding sections, nanoparticles in ImIL have seen dramatic developments for catalysis applications, 120,[194][195][196][197][198][199][200][201][202][203][204] amongst others in Heck 136,147,153,194,[205][206][207][208] reactions. Concerning the catalytic performances of these new hybrid materials, it was already noted that the presence of NHC cannot be omitted, and can even be considered as part of the catalytic system.…”

Ionic Liquid/Oil Microemulsions as Chemical Nanoreactors

“…Hence, the term “designer solvents” is common when describing ILs. Room-temperature ionic liquids (RTILs) can act as solvents for various reactions and often give different reactivity and selectivity than do volatile organic solvents. − Moreover, the ability of some ILs to support the self-assembly of amphiphiles is of particular importance. − Therefore, micelles as well as lyotropic liquid-crystal phases , formed by surfactant self-organization have been described. Despite the tunable properties of ILs, the limitations of solubility in nonpolar solvents remain but are likely to be overcome with the use of ILs in microemulsions …”

Heck Coupling in Ionic Liquids

“…Chitosan supported Pd(OAc) 2 nanoparticles (Pd-NP) in TBAB with added tetrabutyl ammonium acetate (TBAA) gave rise to very rapid Heck couplings of aryl bromides, iodides and activated chlorides (Scheme 23). [95] The supported catalyst was amenable to multiple recycles, whereas the free nano particles rapidly lost activity. There have been multiple reports on the use of nitrile-functionalized RTILs, such as the imidazolium and pyridinium based systems, in Pd-catalysed reactions, including the Heck reaction.…”