A facile synthesis of mixed ligand Cu(II) complexes with salicylaldehyde and salicylaldimine ligands and their X-ray structural characterization

High yield synthetic routes to the preparation of new mixed ligand Cu(II) complexes (1–7) derived from a sterically hindered salicylaldimine and the corresponding salicylaldehyde have been developed. The complexes could be obtained either forming a salicylaldimine preligand or two optional Cu(II) complex precursors. One-pot synthesis could also be used. The complexes have been fully characterized by means of elemental analysis, UV–Vis and IR spectroscopy. Crystal structures obtained for four [(3,5-di-tert-butylsalicylaldehydato)(N-R-3,5-di-tert-butylsalicylaldiminato)]Cu(II) (where R = phenyl (1), isopropyl (3), benzyl (5) and 2-phenylethyl (6)) complexes show that three of them are cis-isomers and one is a trans-isomer with respect to the phenolic O-atoms. Complexes 1, 5 and 6 form preferably loose dimers while 3 favors to exist in a loose polymeric structure in a crystal. In all these polynuclear forms the geometry around the Cu(II) ions is a distorted octahedron.