摘要:
A family of N-heterocyclic carbene ligands based on N-acyl iminoimidazolium ylides has been developed and investigated. The ylides are stable and are easily obtained in two steps. Following deprotonation, they form bidentate anionic NHC ligands. The synthesis of silver(I) complexes was explored. Different complex structures have been obtained, depending on the steric and electronic properties of the starting ylide proligands. Dimeric structures were usually obtained, but trimeric structures were observed under certain conditions. DFT calculations were used to explain these results. The electronic properties of the complexes can be modified by the choice of the electron-withdrawing group attached to the anionic tether. The silver complexes are proficient ligand transfer agents. The first example of a proligand/ligand exchange was demonstrated. The catalytic activity of the silver complexes was evaluated in a model (3 + 2) heterocycloaddition of an imino ester with an activated alkene.