Amine-substituted α-N(standard)- and δ-N(remote)-pyridylidene complexes: Synthesis and bonding

Reaction of ortho-amino-para-chloro- and ortho-chloro-para-amino-pyridinium triflate with tetrakis(triphenylphosphine) complexes of Ni or Pd afforded by oxidative substitution compounds that can be represented as cationic carbene complexes. NMR as well as X-ray structural studies revealed the role played by the NMe2 and M(PPh)2Cl (M = Ni or Pd) substituents in stabilizing the complexes by π-retro-donation and, consequently, in governing the relative importance of certain mesomeric representations describing their structures.