Linkage isomerism in transition-metal complexes of mixed (arylcarboxamido)(arylimino)pyridine ligands

The synthesis of a series of asymmetric mixed 2,6-disubstituted (arylcarboxamido)(arylimino)pyridine ligands and their coordination chemistry toward a series of divalent first-row transition metals (Cu, Co, and Zn) have been explored. Complexes featuring both anionic N,N,N″-carboxamido and neutral O,N,N-carboxamide coordination have been prepared and characterized by X-ray crystallography, cyclic voltammetry, and UV-visible and EPR spectroscopy. Specifically, ^RLM(X) (M = Cu; X = Cl^-, OAc^-) and ^RL(H)MX₂ (M = Cu, Co, Zn; X = Cl^-, SbF ₆^-) complexes that feature N,N,N″- or O,N,N-coordination are presented. Base-induced linkage isomerization from O,N,N-carboxamide to N,N,N″-carboxamido coordination is also confirmed by multiple forms of spectroscopy.