Unusual rearrangement of an N-heterocyclic carbene via a ring-opening and ring-closing process

Abstract

The reaction of a pentadentate NHC ligand precursor with Ni(OAc)₂·4H₂O or Pd(OAc)₂ in the presence of a base yields four-coordinate square-planar Ni(II) and Pd(II) complexes with an unusual ligand generated in situ. A series of experimental studies point to a ring-opening and ring-closing process via novel C–N bond cleavage and formation.