Template reactions: Axial-ligation and macrocyclization of alpha-furilglyoximates and alpha-aminedioximates of cobalt(III) and rhodium(III)

A series of cobaloximes were synthesized from a-furilglyoximates and α-aminedioximates of cobalt(II), cobalt(III) and rhodium(III) and monodentate ligands having different inductive and steric requirements. The six-coordinate H-bonded macrocycles initially formed were used as metal templates to prepare the corresponding BF₂-capped macrocycles. Characterization of the complexes was carried out by magnetic, spectroscopic, ¹H and ¹³C nmr measurements as well as elemental analysis. The cobaloximes reported are quite stable and mimic the metal core of several biological molecules such as vitamin B₁₂.