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–, SbF6–) 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.