Synthesis, structure and catalytic activity of macrocyclic NHC Pd pincer complexes

- We synthesized a series of new N-heterocyclic carbene (NHC) macrocyclic Pd pincer complexes (17-22) by the reaction of Pd(OAc) 2 or Pd 2 (dba) 3 with the corresponding macrocycles, which were prepared by the coupling reaction of dibromides with bisimidazoles. The complex adopted twisted conformation, and the activation energy of the conformational interconversion of the macrocycle was determined by VT-NMR. We also examined the catalytic activity of these Pd complexes in Mizoroki-Heck and oxidative alkynyl-alkynyl homocoupling reactions.