A highly substitutable palladium(II) complex stabilized by the smallest steric N-heterocyclic carbene, IMe (IMe = 1,3- dimethylimidazole-2-ylidene)

Abstract

Palladium complexes supported by N-heterocyclic carbenes (NHCs) have been of great interests in catalysis because of their capability as efficient catalysts in organic synthesis.[1, 2] Since the strong palladium–NHC bonds retain the stability of palladium complexes, and steric modification of the NHC ligands can be readily available, NHCs become more popular and important alternatives to phosphines as supporting ligands.[3, 4] Thus, the synthetic direction of NHCs has been aimed to optimize both electronic and steric properties of NHCs, which allows one to maximize the reactivity of inorganic catalysts for desired results.[4] As the results, numerous Pd(II)–NHC complexes have been synthesized and applied in cross-coupling reactions, telomerization reactions, oxidation reactions including a catalytic conversion of methane to methanol.[5-9] Although significant efforts have been made to increase steric bulkiness of NHC in particular,[10] another simple approach to access a reactive palladium complex is to introduce labile ligands to a metal center. In addition, since mono-ligated palladium complexes have been also known as active catalysts in most palladium catalyzed organic reactions, efficient methods to generate mono-ligated NHC palladium complexes have been successfully developed and utilized for the organic synthesis.[3, 11] © 2016 Korean Chemical Society