Dinuclear Zn(II) complexes with Schiff base ligands derived from 4-aminoantipyrine; crystal structure and catalytic activity in the synthesis of tetrazoles

Abstract

Two new phenolato bridged dinucelar Zn(II) complexes, [Zn2(L1)2(N3)2] (1) and [Zn2(L2)2(N3)2] (2), were synthesized where HL1 and HL2 are tridentate Schiff base ligands obtained from the reaction of 4-aminoantipyrine with 5-bromo-2-hydroxybenzaldehyde and 2-hydroxybenzaldehyde, respectively. The ligands and complexes were characterized by elemental analysis and spectroscopic methods. Crystal structures of complexes 1 and 2 were determined by X-ray analysis which revealed the Zn(II) ions in both of these neutral dinuclear complexes are five coordinated and have distorted square pyramidal geometry. The equatorial plane of this geometry is filled by ONO-donor atoms of the ligands and the axial position is filled by azide co-ligand. Intermolecular interactions in the crystal structure of 1 and 2 were studied by Hirshfeld surface analysis. Due to the presence of azide ligand in the structure of these complexes, they were used as catalysts in the synthesis of 5-phenyl-1H-tetrazole from the reaction of benzonitrile and sodium azide. The results indicated that complexes 1 and 2 are active catalysts for the synthesis of tetrazoles from nitrile and azide cycloaddition reaction.