Manganese and Zinc Complexes Incorporating an Unsaturated Cyclic Schiff Base Ligand

A number of manganese(II) and -(III) as well as two zinc(II) complexes with the conjugated cyclic Schiff base, H₂[14]12eneN₄, have been synthesized and fully characterized. The high-spin Mn(III) complexes have the stoichiometry Mn(III) [14] 12eneN₄X, where X is Cl^-, Br^-, SCN^-, and N₃^-. The compounds are intensely colored and exhibit a number of electronic transitions which appear to be associated with the ligand framework. The reduced magnetic moment of the azide derivative suggests that for this complex the Mn(III) ions are linked via an azide bridge in the solid state. Manganese(II) and zinc(II) form five-coordinate complexes with H₂[14] 12eneN₄ having stoichiometry M(II)[14] 12eneN₄(amine), where amine is triethylor tri-n-propylamine. NMR studies on the diamagnetic zinc(II) complexes indicate that the sterically hindered tertiary amine is axially coordinated to the metal ion. The distorted five-coordinate geometry is attributed to the mismatch between the relatively large high-spin d⁵ and d¹⁰ metal ions and the hole provided by the macrocyclic ligand. The chemical reactivity of the complexes is also discussed.