Synthesis, crystal structure and spectral characterization of the first Ag+ complex compounds involving O,N,O-coordinated N-acylhydrazones of salicylaldehyde

Abstract

N-acylhydrazones of salicylaldehyde is a well known class of ligands bearing O,N,O tridentate chelate coordination site. But up to now no structurally characterized Ag+ complexes with O,N,O coordinated N-acylhydrazones of salicylaldehyde were known. Therefore three Ag+ coordination compounds with functionally substituted N-acylhydrazones of salicylaldehyde were synthesized and characterized by X-ray diffraction, IR spectroscopy and thermogravimetric studies. In solutions the complexes were studied by 1H NMR and UV–Vis spectroscopy.The influence of the presence and location of additional nitrogen donor atoms in N-acylhydrazones of salicylaldehyde on their coordination modes was investigated. Ligand N’-salicylidenephenylacetohydrazide (contains no additional donor atoms) coordinates to Ag+ in classical O,N,O tridentate chelate manner. Ligand N′-salicylidene-3-pyridinecarbohydrazide (contains β-N additional donor atom in acyl moiety) involves mixed O,N,O + β-N coordination. Whereas N’-salicylidene-4-pyridinecarbohydrazide (contains γ-N additional donor atom) coordinates to Ag+ in monodentate manner only via γ-N atom of heterocyclic substituent.All the complexes provide high coordination numbers of Ag+ and irregular shapes of coordination polyhedra which are not consistent with classical concepts of Ag+ coordination chemistry. However all the complexes are not thermally stable and easily undergo solvolysis upon dissolution.