Unusual copper(II) coordination mode from a potential Schiff-base reaction

The Schiff-base ligands (1-3) formed from the reaction of 3-hydroxybenzaldehyde with three alkyl diamines have been synthesised and characterised. They are stable both in solution and in the solid state for several weeks, with no degradation to the starting amines and aldehyde observed. The reactions of the three Schiff-base ligands with various MX2 salts (M = Cu, Ni or Zn; X = chloride, perchlorate or acetate) resulted in the cleavage of the imine bond and formation of metal-amine complexes, as well as the entrapment of a two coordinate CuCl2 molecule within the lattice in one particular case.