Template synthesis of square-planar nickel(II) and copper(III) complexes based on hydrazide ligands

Abstract

Ring-closure reactions between anionic complexes of nickel(II) and copper(II) with the hydrazide ligands (2-hydroxyiminopropionohydrazide [CH₃C(NOH)C(O)NHNH₂, H₂poh] and oxalodihydrazide [NH₂NHC(O)C(O)NHNH₂, H₂oxh] and formaldehyde have been investigated. The isolated compounds were characterised by means of NMR, IR spectroscopy, cyclic voltammetry and single crystal X-ray analysis. In the case of the copper complex with H₂oxh the cyclisation is accompanied by oxidation of the central atom to the +3 state with oxygen in the air. The central atoms in the complexes are square-planar with four nitrogen atoms belonging to the deprotonated hydrazide (Cu) or two hydrazide and two oxime (Ni) groups. The cyclic 1,3,5-oxodiazinane fragment in the complexes adopts a chair conformation which is retained in solution.